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{{#Wiki_filter:LS-AA-125-1001 Revision 5 N:\PUBLIC\Quad Cities Q2R18 Dryer\!Final RCA Docs\!!RCR Dryer Final no Att.doc Title: Q2R18 Concerns Related to Steam Dryer Unit(s): Quad Cities Unit 2 Event Date:
{{#Wiki_filter:LS-AA-125-1001 Revision 5 Title: Q2R18 Concerns Related to Steam Dryer Unit(s): Quad Cities Unit 2 Event Date: 03/29/2006 Event Time:
03/29/2006 Event Time:
Action Tracking Item Number: 472321-03 Report Date: 05/16/2006 Sponsoring Manager: Tim Hanley, Exelon Nuclear Corporate Manager Exelon Corporation Investigators & Exelon Contracted Contributors:
Action Tracking Item Number:
Roger Armitage & Steve Boline, Quad Cities RC Team Leads Alan Lewis, Quad Cities Engineering (RC Investigator Qualified)
472321-03 Report Date
Bhausaheb Shete, Dresden Engineering (RC Investigator Qualified)
: 05/16/2006 Sponsoring Manager: Tim Hanley, Exelon Nuclear Corporate Manager Exelon Corporation Investigators & Exelon Contracted Contributors: Roger Armitage & Steve Boline, Quad Cities RC Team Leads Alan Lewis, Quad Cities Engineering (RC Investigator Qualified)  
Karl Adlon, Quad Cities Engineering Joe Sipek, Dresden Engineering Programs Manager Jeff Miller, Clinton Engineering Programs Manager Chris Cooney, Kennett Square Engineering Dave Haberkorn, Quad Cities Operations Matt Dreyfuss, Kennett Square Engineering Bill McDonald, LaSalle Engineering Pete Shier, Byron Engineering Guy DeBoo, SME Exelon Engineering, Cantera David Melear, Engineer, ILD Inc.
 
Bhausaheb Shete, Dresden Engineer ing (RC Investigator Qualified) Karl Adlon, Quad Cities Engineering Joe Sipek, Dresden Engineering Programs Manager Jeff Miller, Clinton Engineering Programs Manager Chris Cooney, Kennett Square Engineering Dave Haberkorn, Quad Cities Operations Matt Dreyfuss, Kennett Square Engineering Bill McDonald, LaSalle Engineering  
 
Pete Shier, Byron Engineering  
 
Guy DeBoo, SME Exelon Engineering, Cantera  
 
David Melear, Engineer, ILD Inc.  
 
Robert Stackenborghs, Engineer, ILD Inc.
Robert Stackenborghs, Engineer, ILD Inc.
General Electric Corporation (GE) Investigation Team (see Ref. 21 for full list): Robert Gamble, SME GE RC Team Rowland Linford, GE RC Team Lead  
General Electric Corporation (GE) Investigation Team (see Ref. 21 for full list):
Robert Gamble, SME GE RC Team Rowland Linford, GE RC Team Lead N:\PUBLIC\Quad Cities Q2R18 Dryer\!Final RCA Docs\!!RCR Dryer Final no Att.doc


Page 2 of 43 Table of Contents Section Page I. Executive Summary 3-4 II. Condition Statement 5 III. Event Description 6-12 IV. Analysis   13-20 V. Evaluation A. Table of Causal Factors   B. Discussion of Basis for Cause Determination C. Discussion of Evaluation of Other Conditions 21 23 30 VI. Extent of Condition 35 VII. Risk Assessment 36 VIII. Previous Events 37 IX. Corrective Actions to Prevent Recurrence 37 X. Corrective Actions 38 XI. Effectiveness Reviews 38 XII. Programmatic/Organizational Issues 39 XIII. Other Issues 42 XIV. Communication Plan 43 Figures: 1. General Steam Dryer Configuration
Table of Contents Section                                                                     Page I. Executive Summary                                                       3-4 II. Condition Statement                                                     5 III. Event Description                                                     6-12 IV. Analysis                                                               13-20 V. Evaluation A. Table of Causal Factors                                         21 B. Discussion of Basis for Cause Determination                     23 C. Discussion of Evaluation of Other Conditions                     30 VI. Extent of Condition                                                     35 VII. Risk Assessment                                                       36 VIII. Previous Events                                                       37 IX. Corrective Actions to Prevent Recurrence                               37 X. Corrective Actions                                                       38 XI. Effectiveness Reviews                                                   38 XII. Programmatic/Organizational Issues                                     39 XIII. Other Issues                                                         42 XIV. Communication Plan                                                     43 Figures:
: 2. Schematic of Steam Dryer of Base Ring to RPV Lug Orientation F. 1 F. 2 Attachments:
: 1. General Steam Dryer Configuration                               F. 1
: 1. Event and Causal Factors Chart
: 2. Schematic of Steam Dryer of Base Ring to RPV Lug Orientation     F. 2 Attachments:
: 2. Event Timeline
A. 1-2
: 3. References
: 1. Event and Causal Factors Chart A. 3-4
: 4. Comparison: QC 2 Replacement Dryer Pressure Sensor Data with Q2R18 Dryer Damage. 5. Failure Mode Tree - Dryer Skirt Crack/Deformation
: 2. Event Timeline A. 5-7
: 6. Failure Mode Tree -
: 3. References A. 8-10
Dryer End Plate Cracks
: 4. Comparison: QC 2 Replacement Dryer Pressure Sensor Data with Q2R18 Dryer Damage.
: 7. Dryer Lift Event De scription and Pictures
: 5. Failure Mode Tree - Dryer Skirt Crack/Deformation               A. 11-20
: 8. Table of Q2R18 INRs/IRs  
: 6. Failure Mode Tree - Dryer End Plate Cracks                       A. 21-24
: 7. Dryer Lift Event Description and Pictures                       A. 25-34
: 8. Table of Q2R18 INRs/IRs                                         A. 35 9: CAs from ERV Actuator RCA Aligned with CF2 of Q2R18            A. 36-37 Steam Dryer RCA 10: Root Cause Quality Checklist                                    A. 38-39 Page 2 of 43


9: CA's from ERV Actuator RCA Aligned with CF2 of Q2R18 Steam Dryer RCA 10:  Root Cause Quality Checklist
I. Executive Summary:
During the planned in-vessel visual inspection (IVVI) of the Quad Cities Unit 2 (U-2) reactor steam dryer at the beginning of refueling outage Q2R18, a crack was discovered in the dryer skirt at the 140° azimuth location. At the completion of all dryer inspections, cracks were discovered at various locations in the dryer assembly including the dryer skirt base ring, a vane bank end plate, chevron plates, and a latch box. Several of these cracks occurred in areas adjacent to one of the two areas most severely deformed during removal of the dryer in May 2005.
This Root Cause Analysis (RCA) investigation scope was focused on determining the causes of the dryer assembly cracking in the dryer skirt plate, the vane bank endplate, and the latch box assembly.
RCA investigation into the events associated with the design, fabrication, installation and operation of the steam dryer identified a series of factors that, when taken in aggregate, are the causes for the formation of the identified cracks. The causes for each of the three cracks included in the scope of this RCA is summarized below:
: 1. Steam Dryer Lower Skirt Crack at 140°: The root cause for this cracking is related to deformation caused when the dryer skirt base ring caught on the reactor pressure vessel (RPV) dryer support lugs in May 2005 (referred to as the lifting event). The exact mechanism of initiation of the cracks could not be determined, however the RCA concludes that this event introduced significant plastic strains that reduced the materials fatigue endurance properties. When combined with the cyclic loadings that the dryer experiences during normal operation, fatigue cracking propagated through the skirt base ring and into the dryer skirt panels. The lifting event occurred as a result of changes in design of the installation hardware used in the replacement dryer. This change in installation hardware is considered a root cause.
These changes, combined with widened installation clearances introduced during dryer fabrication (referred to as ovality) allowed for enough movement for the dryer to become damaged on the RPV support lugs during removal. The widened installation clearance introduced from fabrication ovality is also considered a root cause for the dryer skirt cracking.
: 2. Cracking in Gusset 19 of Vane Bank E at 320°: Root cause is: having very little weld metal between the end plates, proximity to a weld transition (Stress Riser), fabrication stresses due to hood assembly and weld shrinkage, and the presence of operating vibration loads.
: 3. Cracking in Latch Box at 220°: Root cause is: high residual weld stress from weld end discontinuity and the corner location.
Corrective actions include:
* Repair of the most severely damaged portions of the dryer skirt and base plate near the 140° azimuth.
* Replacement of skirt and base plate material in the 220° azimuth area, which did not exhibit cracking but was considered to have similar potential crack initiating factors as the 140° azimuth areas.
* Modification of the dryer base plate to reduce the potential for future lifting events.
* Modification of the dryer guide slots to reduce the potential for future lifting events.
* Repair of the crack in the dryer latch box at the 220° azimuth.
Page 3 of 43
* Evaluation of the visual indications (crack) in the bank E drying vane end plate. Evaluation concluded that there was adequate justification for continued operation of the steam dryer without repair of the cracking at the gusset to vane bank end plate locations (Ref. 17)
* Modified main steam relief valve branch lines with acoustic side branches to reduce dryer cyclic loads.
An extent of condition review included inspections of other susceptible areas of the steam dryer. All dryer cracking was reviewed in accordance with IVVI program requirements regarding actions required prior to restart from Q2R18, and appropriate inspections in future outages. The key analysis documents for these determinations are listed in Attachment 8 of this RCA. No other degradation similar to the three events in the scope of this RCA was identified. Analyses completed by General Electric (GE) and reviewed by Exelon determined that without the additional stresses and material degradation resulting from the May 2005 lifting event, the operational loads were not sufficient to initiate cracking in the U-2 dryer skirt plate. Therefore, similar cracking of the Unit 2 dryer is not expected to occur in the future.
In addition, the Unit 1 steam dryer, which did not experience either fabrication ovality or installation lifting events, did not exhibit similar cracking when inspected in the Q1M19 outage in May 2006.
The steam dryer degradation was not reportable, however the issue has been discussed with the Nuclear Regulatory Commission (NRC). A risk assessment of the identified condition was performed and determined the consequences of this event had minimal impact on reactor safety. Although unanticipated structural cracking was identified in the dryer, the cracking did not represent an increase in risk to nuclear safety or off-site dose consequences. A Probabilistic Risk Assessment (PRA) evaluation found this event to be non-risk significant.
Page 4 of 43


A. 1-2 A. 3-4 A. 5-7 A. 8-10
II. Condition Statement:
During the planned IVVI in Q2R18, the RPV steam dryer was removed from the vessel and inspected.
Initial inspection revealed a branching crack in the dryer lower skirt area approximately 6 feet in total length at the 140° azimuth location (Refs. 10&11). Subsequent inspections also identified cracking in the steam dryer vane bank end plate in the E bank (Refs. 12&13), and a crack in the lower right corner of one dryer latch box (Refs. 14&15). These three conditions form the specific investigation scope requiring resolution in this RCA, and are referred to in subsequent sections of the RCA as:
Event 1: Steam Dryer Lower Skirt Cracking near the 140° azimuth, identified in AR 472321.
Event 2: Steam Dryer Cracking in Gusset 19 of Vane Bank E End Plate near the 320° azimuth, identified in AR 473034.
Event 3: Steam Dryer Cracking in Latch Box near the 220° azimuth, identified in AR 475369.
Additional dryer cracking was identified during Q2R18, and although not specifically included in the scope of this RCA, all dryer cracking was reviewed and dispositioned in accordance with IVVI program requirements. Specifically, actions required prior to restart from Q2R18 were completed, and appropriate inspections in future outages were specified. The key analysis documents for these determinations are listed in Att. 8 of this RCA.
Consequences & Significance: The dryer is a passive non-safety related component, however, it must remain structurally intact to preclude introduction of loose material into plant systems such that no safety-related systems, structures or components are prevented from performing their design basis safety function. Additionally, the dryer skirt must function as a boundary to maintain the basis for reactor water level sensing and protective actuations. At the time of discovery, all dryer components, including the skirt, remained constrained within the dryer envelope and therefore, there was no safety significance to this event.
This report focuses on the equipment failure, the failure modes, and causal factors for the identified dryer issues. The failure of the skirt plate has the potential to generate debris, for which a lost part evaluation (Ref. 20 is the Lost Parts Evaluation for this condition) was completed for Unit 1 impacts.
This event is not considered a recurring problem since the Unit 2 dryer is a newly installed replacement.
OPEX reviews have not identified previous history with large cracking in dryer skirt plate material similar to that identified in Q2R18. Quad Cities Unit 1 has a similarly designed installed replacement dryer and Dresden Units 2 & 3 have similar replacement dryers that are not yet installed. These three additional dryers will be considered for extent of condition in this RCA.
Page 5 of 43


A. 11-20 A. 21-24 A. 25-34 A. 35 A. 36-37 
III. Event
 
A. 38-39
 
Page 3 of 43 I. Executive Summary:
During the planned in-vessel visual inspection (IVVI) of the Quad Cities Unit 2 (U-2) reactor steam dryer at the beginning of refueling outage Q2R18, a crack was discovered in the dryer skirt at the 140 azimuth location. At the completion of all dryer insp ections, cracks were discove red at various locations in the dryer assembly including the dryer skirt base ring, a vane bank end plate, chevron plates, and a latch box. Several of these cracks occurred in areas adjacent to one of the two areas most severely deformed during removal of the dryer in May 2005. This Root Cause Analysis (RCA) investigation scope was focused on determining the causes of the dryer assembly cracking in the dryer skirt plate, the vane bank endplate, and the latch box assembly. RCA investigation into the events associated with the design, fabrication, installation and operation of the steam dryer identified a series of factors that, when taken in aggregate, are the causes for the formation of the identified cracks. The causes for each of the three cracks included in the scope of this RCA is summarized below: 1. Steam Dryer Lower Skirt Crack at 140:  The root cause for this cracking is related to deformation caused when the dryer skirt base ring caught on the reactor pressure vessel (RPV) dryer support lugs in May 2005 (referred to as the "lifting event"). The exact mechanism of initiation of the cracks could not be determined, however the RCA concludes that this event introduced significant plastic strains that reduced the material's fatigue endurance properties. When combined with the cyclic loadings that the dryer experiences during normal operation, fatigue cracking propagated through the skirt base ring and into the dryer skirt panels.
The lifting event occurred as a result of changes in design of the installation hardware used in the replacement dryer. This change in installation hardware is considered a root cause. These changes, combined with widened installation clearances introduced during dryer fabrication (referred to as "ovality") allowed for enough movement for the dryer to become damaged on the RPV support lugs during removal. The widened installation clearance introduced from fabrication ovality is also considered a root cause for the dryer skirt cracking. 2. Cracking in Gusset 19 of Vane Bank "E" at 320:  Root cause is: having very little weld metal between the end plates, proximity to a weld transition (Stress Riser), fabrication stresses due to hood assembly and weld shrinkage, and the presence of operating vibration loads.
: 3. Cracking in Latch Box at 220:  Root cause is: high residual weld stress from weld end discontinuity and the corner location. 
 
Corrective actions include:  Repair of the most severely damaged portions of the dryer skirt and base plate near the 140 azimuth. Replacement of skirt and base plate material in the 220 azimuth area, which did not exhibit cracking but was considered to have similar potential crack initiating factors as the 140 azimuth areas. Modification of the dryer base plate to reduce the potential for future lifting events. Modification of the dryer guide slots to reduce the potential for future lifting events. Repair of the crack in th e dryer latch box at the 220 azimuth.
Page 4 of 43 Evaluation of the visual indications (crack) in the bank E drying vane end plate. Evaluation concluded that there was "adequate justification for continued operation of the steam dryer without repair of the cracking at the gusset to vane bank end plate locations -" (Ref. 17) Modified main steam relief valve branch lines with acoustic side branches to reduce dryer cyclic loads.
An extent of condition review included inspections of other susceptible areas of the steam dryer. All dryer cracking was reviewed in accordance with IVVI program requirements regarding actions required prior to restart from Q2R18, and appropriate inspections in future outages. The key analysis documents for these determinations are listed in Attachment 8 of this RCA. No other degradation similar to the three events in the scope of this RCA was identified. Analyses completed by General Electric (GE) and reviewed by Exelon determined that without the additional stresses and material degradation resulting from the May 2005 lifting event, the operational loads were not sufficient to initiate cracking in the U-2 dryer skirt plate. Therefore, similar cracking of the Unit 2 dryer is not expected to occur in the future. In addition, the Unit 1 steam dryer, which did not experience either fabrication ovality or installation lifting events, did not exhibit similar cracking when inspected in the Q1M19 outage in May 2006.
The steam dryer degradation was not reportable, however the issue has been discussed with the Nuclear Regulatory Commission (NRC). A risk assessment of the identified condition was performed and determined the consequences of this event had minimal impact on reactor safety. Although unanticipated structural cracking was identified in the dryer, the cracking did not represent an increase in risk to nuclear safety or off-site dose consequences. A Probabilistic Risk Assessment (PRA) evaluation found this event to be non-risk significant.
 
Page 5 of 43 II. Condition Statement:
During the planned IVVI in Q2R18, the RPV steam dryer was removed from the vessel and inspected. Initial inspection revealed a branching crack in the dryer lower skirt area approximately 6 feet in total length at the 140 azimuth location (Refs. 10&11). Subsequent inspections also identified cracking in the steam dryer vane bank end plate in the "E" bank (Refs. 12&13), and a crack in the lower right corner of one dryer latch box (Refs. 14&15). These three conditions form the specific investigation scope requiring resolution in this RCA, and are referred to in subsequent sections of the RCA as:
Event 1:  Steam Dryer Lower Skirt Cracking near the 140 azimuth, identified in AR 472321. Event 2: Steam Dryer Cracking in Gusset 19 of Vane Bank "E" End Plate near the 320 azimuth, identified in AR 473034. Event 3:  Steam Dryer Cracking in Latch Box near the 220 azimuth, identified in AR 475369.
Additional dryer cracking was identified during Q2R18, and although not specifically included in the scope of this RCA, all dryer cracking was reviewed and dispositioned in accordance with IVVI program requirements. Specifically, actions required prior to restart from Q2R18 were completed, and appropriate inspections in future outages were specified. The key analysis documents for these determinations are listed in Att. 8 of this RCA. Consequences & Significance:  The dryer is a passive non-safety related component, however, it must remain structurally intact to preclude introduction of loose material into plant systems such that no safety-related systems, structures or components are prevented from performing th eir design basis safety function. Additionally, the dryer skirt must function as a boundary to maintain the basis for reactor water level sensing and protective actuations. At the time of discovery, all dryer components, including the skirt, remained constrained within the dryer envelope and therefore, there was no safety significance to this event. This report focuses on the equipment failure, the failure modes, and causal factors for the identified dryer issues. The failure of the skirt plate has the potential to generate debris, for which a lost part evaluation (Ref. 20 is the Lost Parts Evaluation for this condition) was completed for Unit 1 impacts. This event is not considered a recurring problem since the Unit 2 dryer is a newly installed replacement.
OPEX reviews have not identified previous history with large cracking in dryer skirt plate material similar to that identified in Q2R18. Quad Cities Unit 1 has a similarly designed installed replacement dryer and Dresden Units 2 & 3 have similar replacement dryers that are not yet installed. These three additional dryers will be considered for extent of condition in this RCA.
 
Page 6 of 43 III. Event


== Description:==
== Description:==


Note: This event description provides a chronological narrative of the sequence of events as they apply to this RCA. This section also includes "Notes" intended to highlight the significance of the information as it applies to the subsequent Analysis and Evaluation sections. Additional items included in this RCA report, which may assist in general understanding of the events, include:
Note: This event description provides a chronological narrative of the sequence of events as they apply to this RCA. This section also includes Notes intended to highlight the significance of the information as it applies to the subsequent Analysis and Evaluation sections. Additional items included in this RCA report, which may assist in general understanding of the events, include:
Att. 1: Event and Causal Factors Chart. Att. 2: Event Timeline Table.  
Att. 1: Event and Causal Factors Chart.
 
Att. 2: Event Timeline Table.
Att. 3: List of References.
Att. 3: List of References.
Fig. 1: General Steam Dryer Configuration Fig. 2: Schematic of Steam Dryer Base Ring to RPV Lug Orientation 2004 - Early 2005 Following several previous Quad Cities outages in which steam dryers were found with failed or degraded dryer elements, a decision was made to purchase and install new steam dr yers in both units.  
Fig. 1: General Steam Dryer Configuration Fig. 2: Schematic of Steam Dryer Base Ring to RPV Lug Orientation 2004 - Early 2005 Following several previous Quad Cities outages in which steam dryers were found with failed or degraded dryer elements, a decision was made to purchase and install new steam dryers in both units.
 
The steam dryer was fabricated and assembled at U.S. Tool and Die in Pittsburgh, PA under the direction of GE. Due to transportation limitations, the steam dryer could not be shipped in one piece in the required timeframe. This required that the dryer be fabricated as two assemblies that were shipped separately and then assembled locally.
The steam dryer was fabricated and assembled at U.S. Tool and Die in Pittsburgh, PA under the direction of GE. Due to transportation limitations, the steam dryer could not be shipped in one piece in the required timeframe. This required that the dryer be fabricated as two assemblies that were shipped separately and then assembled locally. Note: During the design and fabrication of the new Quad Cities steam dryers, several issues imposed constraints on the delivery of the first dryer for Quad Cities. Manufacturing delays necessitated that the dryer originally intended for Quad Cities U-1 installation during Q1R18, be delivered for installation in Unit 2 during Q2P03.  
Note: During the design and fabrication of the new Quad Cities steam dryers, several issues imposed constraints on the delivery of the first dryer for Quad Cities. Manufacturing delays necessitated that the dryer originally intended for Quad Cities U-1 installation during Q1R18, be delivered for installation in Unit 2 during Q2P03.
 
March 2005 The Unit 2 replacement steam dryer upper half (vane banks and support ring) and the skirt assembly were welded together at J. T. Cullen in Fulton, IL.
March 2005 The Unit 2 replacement steam dryer upper half (vane banks and support ring) and the skirt assembly were welded together at J. T. Cullen in Fulton, IL.
3/30/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 0 was signed by the Reactor Services department representative. Note: This was the initial end user's review in the Exelon design process. This review is considered a "cross discipline" review and a barrier to prevent negative impacts of design changes. This review was documented after dryer fabrication was almost complete. This topic is discussed further in the evaluation section.
3/30/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 0 was signed by the Reactor Services department representative.
 
Note: This was the initial end users review in the Exelon design process. This review is considered a cross discipline review and a barrier to prevent negative impacts of design changes. This review was documented after dryer fabrication was almost complete. This topic is discussed further in the evaluation section.
3/31/05 Inspection of the dryer at J.T. Cullen following assembly determined that the as-built dryer dimensions were outside the expected design tolerances. The diameter measured across the 0-180 orientation measured 245", while the 90-270 orientation measured 249". Welding distortion was noted as the cause. Laser measurements of the assembled dryer were conducted and confirmed that QC2 dryer base was approximately 2 inches out of round.
3/31/05 Inspection of the dryer at J.T. Cullen following assembly determined that the as-built dryer dimensions were outside the expected design tolerances. The diameter measured across the 0°-180° orientation measured 245, while the 90°-270° orientation measured 249. Welding distortion was noted as the cause. Laser measurements of the assembled dryer were conducted and confirmed that QC2 dryer base was approximately 2 inches out of round.
Note: Subsequent sections of this RCA refer to this as the "ovality" issue.
Note: Subsequent sections of this RCA refer to this as the ovality issue.
Page 7 of 43 4/25/05 GE Deviation Disposition Request (DDR) 431002828-27 (Ref. 7) was approved, accepting the dimensions of the base plate as-is. Investigation determined the dimensional deficiencies resulted from welding performed at J. T. Cullen, which resulted in distortion of the dryer mid-support ring, skirt and base plate. The DDR noted that the dryer will fit in the vessel despite this ovality. Normal clearances were "compromised" so additional guidance constraints were placed in the lower guide block to limit misalignment and assist in installation. Notes:  1. The additional constraints noted above are the guide rod spacer blocks installed under Field Disposition Instructi on (FDI) 0085 (Ref. 9)  2. This DDR addressed the dimensional issues due to the ovality but did not address potential residual stresses in the dryer as a result of this distortion.
Page 6 of 43
4/26/05 The U-2 replacement dryer was transported to the station and subsequently moved to the reactor building refueling floor. 


4/25/05 GE Deviation Disposition Request (DDR) 431002828-27 (Ref. 7) was approved, accepting the dimensions of the base plate as-is. Investigation determined the dimensional deficiencies resulted from welding performed at J. T. Cullen, which resulted in distortion of the dryer mid-support ring, skirt and base plate. The DDR noted that the dryer will fit in the vessel despite this ovality. Normal clearances were compromised so additional guidance constraints were placed in the lower guide block to limit misalignment and assist in installation.
Notes: 1. The additional constraints noted above are the guide rod spacer blocks installed under Field Disposition Instruction (FDI) 0085 (Ref. 9)
: 2. This DDR addressed the dimensional issues due to the ovality but did not address potential residual stresses in the dryer as a result of this distortion.
4/26/05 The U-2 replacement dryer was transported to the station and subsequently moved to the reactor building refueling floor.
4/26/05 Exelon Nuclear Fuels determined that the replacement dryer dP will be less than the original dryer (original dryer dP was nominally 0.3 psid versus an expected dP of 0.1 psid on the replacement dryer).
4/26/05 Exelon Nuclear Fuels determined that the replacement dryer dP will be less than the original dryer (original dryer dP was nominally 0.3 psid versus an expected dP of 0.1 psid on the replacement dryer).
This change has an impact on Minimum Critical Power Ratio Operating Limit, and on the ASME overpressure results. Root cause analysis on these issues is assigned under IR 330331 (Ref. 37). Note: The subsequent RCA concluded: "the root cause of the event was a lack of information on the project team regarding the sens itivity of non-structural analyses to the dryer dP value.  
This change has an impact on Minimum Critical Power Ratio Operating Limit, and on the ASME overpressure results. Root cause analysis on these issues is assigned under IR 330331 (Ref. 37).
 
Note: The subsequent RCA concluded: the root cause of the event was a lack of information on the project team regarding the sensitivity of non-structural analyses to the dryer dP value.
5/4/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 1 was signed by the Reactor Services department representative.
5/4/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 1 was signed by the Reactor Services department representative.
Note: This was a second user's review in the Exelon design process. This review is considered a "cross discipline" review and a barrier to prevent negative impacts of design changes. This topic is discussed further in the evaluation section. This review was documented after the dryer was already fabricated and staged on the Quad Cities Refueling floor.
Note: This was a second users review in the Exelon design process. This review is considered a cross discipline review and a barrier to prevent negative impacts of design changes. This topic is discussed further in the evaluation section. This review was documented after the dryer was already fabricated and staged on the Quad Cities Refueling floor.
05/07/05 Unit 2 shutdown for Q2P03 for the main purpose of installing the replacement dryer.
05/07/05 Unit 2 shutdown for Q2P03 for the main purpose of installing the replacement dryer.
5/11/05 During initial installation in the U-2 reactor vessel an interference was encountered that prevented setting the dryer onto RPV dryer support lugs. At approximately 2.5" above the dryer support lugs, the overhead crane cables went slack and the dryer assembly shifted towards North (approximately 110 azimuth). The dryer was lifted and the vessel area inspected without identifying the source of the interference. Upon restart of the descent, the dryer again st opped and shifted towards North. The dryer was raised slightly to allow further detailed inspection. A camera inspection inside the skirt revealed that the inner diameter of the dryer skirt base plate was interfering with the steam separator Page 8 of 43 guide rods. Although the overall outer diameter of the dryer assembly was not changed by the new design (Ref. 1), the skirt inner diameter is smaller with the base pl ate protruding farther towards the center of the dryer than the original design. This resulted in the interference with the separator guide rods, with the skirt base plate contacting the two guide rods located at the 20 and 200 azimuths.
5/11/05 During initial installation in the U-2 reactor vessel an interference was encountered that prevented setting the dryer onto RPV dryer support lugs. At approximately 2.5 above the dryer support lugs, the overhead crane cables went slack and the dryer assembly shifted towards North (approximately 110° azimuth). The dryer was lifted and the vessel area inspected without identifying the source of the interference. Upon restart of the descent, the dryer again stopped and shifted towards North.
Installation activities were stopped and the Outage Control Center (OCC) was notified of the issue, and discussions were initiated to determine resolution of this problem. Note:  The U-2 replacement dryer exhibited limited clearance between the RPV dryer support lugs and the cutouts provided in the base plate ring. As the dryer is lowered, the skirt base plate must pass all four of the support lugs. The width of a support lug is 3 inches, while the width of the base plate cutout provided is 4-inches, leaving a nominal 1/2" clearance on each side of the lug. This presented a known challenge and plans were to use additional care to field verify that acceptable clearance existed, or modify the clearances as needed. While the dryer was lowered into the RPV for the first time, the GE Product Line Manager was stationed in the reactor cavity to monitor the clearances. It was confirmed during this initial lowering that the clearance between the base ring cutout and RPV lugs was small, but the dryer had been installed without incident until the interference with the separator guide rods was identified. 
The dryer was raised slightly to allow further detailed inspection. A camera inspection inside the skirt revealed that the inner diameter of the dryer skirt base plate was interfering with the steam separator Page 7 of 43
 
5/12/05 When the interference between the separator support rods and the base plate was identified and the dryer could not be installed, it was decided that the dryer would be removed from the RPV to allow modification of the base plate. The OCC recovery and action plan for the dryer removal discussed the tight clearance issue with the oncoming crew. Instructions were provided to the oncoming refuel floor crew performing the dryer lift to watch the RPV lug cl earance very closely due to the tight clearance. During the lift for removal of the dryer, the base plate impacted the vessel support lugs despite the increased scrutiny, including performing the lift slowly, as evidenced by multiple stops. Att. 7 describes in detail the sequence for the base plate contact with the RPV support lugs. At the time of this dryer lift, the load cell display for the overhead cran e was not functional (overload cutout circuits were functional), so there was no ability to estimate the impact load based on floor observations. Workers reported visual evidence of a high load on the lift cables from the noise and rapid cable movement when the load sprung free. When the dryer was set on the decontamination pad, visual damage to the base plate was evident and the OCC was notified. Inspection of the base plate showed a downward deflection/distortion in the dryer base plate from its normal flat horizontal shape. These downward bends were recorded as 3/4" at the 140 location, 5/8" at the 220 location, and 5/16" at the 320 location (Ref. 1). A detailed discussion of what occurred during this "Lift Event", along with pictures of the damage are provided in Att. 7. 
 
5/13/05 Prompt Investigation Report 334348 (Ref.4) on the dryer damage was performed and presented to MRC on 5/13/05. This report reviewed th e sequence of events, and detailed the observed damage as follows: 1. Marks on the bottom of the base plate at the 20 position 2. Mark (burr) on the inside of the base plate at the 220 position 3. At the 40 and 140 positions, seismic shim blocks were noted to have shifted and were scratched 4. Raised metal on 3 clearance slots Page 9 of 43 5. Wear on one RPV support lug
 
Items 1 through 3 were believed to have occurred when the dryer shifted towards North as it contacted the separator guide rod. The prompt investig ation described conflicts or problems with: 1. Original tolerances did not allow the separator guide pins to clear the ID of the dryer base plate. 2. Traveler Package KCZKU-INSTALL-1 stated that special care should be taken to verify no interferences exist, as well as the need to maintain the dryer level and to watch the overhead crane load cell for deviations 3. The overhead crane load cell was not functioning. This prompt investigation concluded that the base plate damage was caused by interference with the separator guide rods and RPV support lugs. Note:  The prompt investigation addressed the fact that the dryer could not set into place due to contact with the separator guide rods. It noted that the cause of the damage was not known at this time (this was handed off to the subsequent ACE). The prompt did not discuss the effects of the damage to the dryer from the lifting event. 
 
5/15/05 To eliminate the interference between the separator guide rods and the skirt/base plate, cutouts were provided in the dryer skirt and the base plate at the 20 o and 200 o azimuth locations. (WO732708-01 / GE Field Deviation Disposition Request (FDDR) RMCN06243, Ref. 29). The cutout of the partial penetration weld was seal welded at the cutout and examined via PT exam. The damage to the base plate was evaluated and found acceptable by GE, an independent third party review, and Exelon for use-as-is (Ref. 1 & 8). FDDR RMCN 06245 included instructions for the material cleanup and disposition of the as-left deformations. The indications caused by the contact with the RPV lugs during the dryer removal were removed from the metal surfaces of the dryer and examined via PT exam prior to reinstalling the dryer in the reactor vessel.
Note:  This RCA reviewed this FDDR, and the supporting documentation, and noted a lack of detail in documenting both the inspection and analysis activities completed to resolve this issue. Because this RCA concluded that the transient imposed on the base plate and dryer skirt was a causal factor for the subsequent cracks during operation, it must be concluded that the Q2P03 review (May 2005) was a missed opportunity to determine the actual state of the dryer. This topic is discussed in more de tail in the Evaluation section.
5/16/05 Unit 2 was started up and operated at EPU and pre-EPU power levels during the remainder of the fuel cycle. No apparent complications to Unit 2 operation due to steam dryer issues were observed during this operating cycle, and the dryer cracking condition was not evident until reactor disassembly for
 
Q2R18 in March 2006.


guide rods. Although the overall outer diameter of the dryer assembly was not changed by the new design (Ref. 1), the skirt inner diameter is smaller with the base plate protruding farther towards the center of the dryer than the original design. This resulted in the interference with the separator guide rods, with the skirt base plate contacting the two guide rods located at the 20° and 200° azimuths.
Installation activities were stopped and the Outage Control Center (OCC) was notified of the issue, and discussions were initiated to determine resolution of this problem.
Note: The U-2 replacement dryer exhibited limited clearance between the RPV dryer support lugs and the cutouts provided in the base plate ring. As the dryer is lowered, the skirt base plate must pass all four of the support lugs. The width of a support lug is 3 inches, while the width of the base plate cutout provided is 4-inches, leaving a nominal 1/2 clearance on each side of the lug. This presented a known challenge and plans were to use additional care to field verify that acceptable clearance existed, or modify the clearances as needed. While the dryer was lowered into the RPV for the first time, the GE Product Line Manager was stationed in the reactor cavity to monitor the clearances. It was confirmed during this initial lowering that the clearance between the base ring cutout and RPV lugs was small, but the dryer had been installed without incident until the interference with the separator guide rods was identified.
5/12/05 When the interference between the separator support rods and the base plate was identified and the dryer could not be installed, it was decided that the dryer would be removed from the RPV to allow modification of the base plate. The OCC recovery and action plan for the dryer removal discussed the tight clearance issue with the oncoming crew. Instructions were provided to the oncoming refuel floor crew performing the dryer lift to watch the RPV lug clearance very closely due to the tight clearance.
During the lift for removal of the dryer, the base plate impacted the vessel support lugs despite the increased scrutiny, including performing the lift slowly, as evidenced by multiple stops.          Att. 7 describes in detail the sequence for the base plate contact with the RPV support lugs. At the time of this dryer lift, the load cell display for the overhead crane was not functional (overload cutout circuits were functional), so there was no ability to estimate the impact load based on floor observations. Workers reported visual evidence of a high load on the lift cables from the noise and rapid cable movement when the load sprung free. When the dryer was set on the decontamination pad, visual damage to the base plate was evident and the OCC was notified.
Inspection of the base plate showed a downward deflection/distortion in the dryer base plate from its normal flat horizontal shape. These downward bends were recorded as 3/4 at the 140° location, 5/8 at the 220° location, and 5/16 at the 320° location (Ref. 1).
A detailed discussion of what occurred during this Lift Event, along with pictures of the damage are provided in Att. 7.
5/13/05 Prompt Investigation Report 334348 (Ref.4) on the dryer damage was performed and presented to MRC on 5/13/05. This report reviewed the sequence of events, and detailed the observed damage as follows:
: 1. Marks on the bottom of the base plate at the 20° position
: 2. Mark (burr) on the inside of the base plate at the 220° position
: 3. At the 40° and 140° positions, seismic shim blocks were noted to have shifted and were scratched
: 4. Raised metal on 3 clearance slots Page 8 of 43
: 5. Wear on one RPV support lug Items 1 through 3 were believed to have occurred when the dryer shifted towards North as it contacted the separator guide rod. The prompt investigation described conflicts or problems with:
: 1. Original tolerances did not allow the separator guide pins to clear the ID of the dryer base plate.
: 2. Traveler Package KCZKU-INSTALL-1 stated that special care should be taken to verify no interferences exist, as well as the need to maintain the dryer level and to watch the overhead crane load cell for deviations
: 3. The overhead crane load cell was not functioning.
This prompt investigation concluded that the base plate damage was caused by interference with the separator guide rods and RPV support lugs.
Note: The prompt investigation addressed the fact that the dryer could not set into place due to contact with the separator guide rods. It noted that the cause of the damage was not known at this time (this was handed off to the subsequent ACE). The prompt did not discuss the effects of the damage to the dryer from the lifting event.
5/15/05 To eliminate the interference between the separator guide rods and the skirt/base plate, cutouts were provided in the dryer skirt and the base plate at the 20o and 200o azimuth locations. (WO732708-01 / GE Field Deviation Disposition Request (FDDR) RMCN06243, Ref. 29). The cutout of the partial penetration weld was seal welded at the cutout and examined via PT exam.
The damage to the base plate was evaluated and found acceptable by GE, an independent third party review, and Exelon for use-as-is (Ref. 1 & 8). FDDR RMCN 06245 included instructions for the material cleanup and disposition of the as-left deformations. The indications caused by the contact with the RPV lugs during the dryer removal were removed from the metal surfaces of the dryer and examined via PT exam prior to reinstalling the dryer in the reactor vessel.
Note: This RCA reviewed this FDDR, and the supporting documentation, and noted a lack of detail in documenting both the inspection and analysis activities completed to resolve this issue.
Because this RCA concluded that the transient imposed on the base plate and dryer skirt was a causal factor for the subsequent cracks during operation, it must be concluded that the Q2P03 review (May 2005) was a missed opportunity to determine the actual state of the dryer. This topic is discussed in more detail in the Evaluation section.
5/16/05 Unit 2 was started up and operated at EPU and pre-EPU power levels during the remainder of the fuel cycle. No apparent complications to Unit 2 operation due to steam dryer issues were observed during this operating cycle, and the dryer cracking condition was not evident until reactor disassembly for Q2R18 in March 2006.
5/25/05 An ACE (Ref. 2) for the steam dryer lifting event was completed and approved on this date. This RCA reviewed this ACE in detail following the identification of cracking in Q2R18. The results of this review are discussed in the Evaluation section.
5/25/05 An ACE (Ref. 2) for the steam dryer lifting event was completed and approved on this date. This RCA reviewed this ACE in detail following the identification of cracking in Q2R18. The results of this review are discussed in the Evaluation section.
Page 10 of 43 This ACE also noted the fact that the crane load cell was not working at the time of the May 2005 dryer lifting event, concluding that that this was not a significant factor in the apparent cause.  (Note:  The load cell was repaired May 16, 2005 prior to placing the dryer back into the vessel (WO 805641-02)). A GE Root Cause Analysis (Ref. 6) was provided on 5/25/05. This report determined that the cause of the interference between the base plate and the steam separator guide pins was that the dryer design process did not ensure that fit-up problems did not exist. This occurred because the Computer Aided Design (CAD) model was not adequately developed. The GE RCA noted that several GE design engineers had initially identified the potential for interference at the separator guide pins, but had failed to revisit the concern prior to completion of the dryer design.
Page 9 of 43


This ACE also noted the fact that the crane load cell was not working at the time of the May 2005 dryer lifting event, concluding that that this was not a significant factor in the apparent cause. (Note: The load cell was repaired May 16, 2005 prior to placing the dryer back into the vessel (WO 805641-02)).
A GE Root Cause Analysis (Ref. 6) was provided on 5/25/05. This report determined that the cause of the interference between the base plate and the steam separator guide pins was that the dryer design process did not ensure that fit-up problems did not exist. This occurred because the Computer Aided Design (CAD) model was not adequately developed. The GE RCA noted that several GE design engineers had initially identified the potential for interference at the separator guide pins, but had failed to revisit the concern prior to completion of the dryer design.
3/28/06 U-2 shutdown for refueling outage Q2R18. While performing IVVI during Q2R18, the cracks were discovered on the steam dryer that led to the initiation of this RCA. The scope of this RCA includes (references noted are for the original Exelon Corrective Action Process (CAP) Issue Report (IR) numbers, and the GE Indication Notification Report (INR) numbers):
3/28/06 U-2 shutdown for refueling outage Q2R18. While performing IVVI during Q2R18, the cracks were discovered on the steam dryer that led to the initiation of this RCA. The scope of this RCA includes (references noted are for the original Exelon Corrective Action Process (CAP) Issue Report (IR) numbers, and the GE Indication Notification Report (INR) numbers):
Event 1- The large crack in the dryer skirt at the 140° azimuth (Ref. 10, 11)
Event 1- The large crack in the dryer skirt at the 140° azimuth (Ref. 10, 11)
Event 2- Dryer "E" bank end plate crack at 320° azimuth. (Ref. 12, 13)
Event 2- Dryer E bank end plate crack at 320° azimuth. (Ref. 12, 13)
Event 3- Latch Box crack at 220° azimuth. (Ref. 14, 15)  
Event 3- Latch Box crack at 220° azimuth. (Ref. 14, 15)
In addition, all four steam dryer lifting eyes were discovered out-of-position, with one lifting eye exhibiting thread damage to the lifting rod. This issue was originally in the scope of this RCA, but it was determined that the lifting eye concerns were not related to the dryer cracking issues. For this reason, the lifting eye issue was removed from the RCA scope, and transferred for evaluation as a separate Equipment Apparent Cause Evaluation (EACE) (AR# 471848-05). A summary of the results of this EACE appears below:
Summary EACE 471848-05: Dryer Lifting Lug Rotation Apparent cause: The design of the lifting eye retention method was inadequate to ensure positive engagement. The design provided no ability for ensuring adequate alignment. The recess was located on the lifting rod, which was contained within the threaded connection once the lifting eye was threaded on. The design relied entirely on external orientation of the lifting eyes, which provided no positive verification. In addition, the dimensions of the recess provided minimal opportunity for successful engagement.
Corrective Actions:
: 1. Modify/Install design of Quad Cities Unit 2 Steam Dryer Lifting Eyes to provide more robust anti-rotation. (Completed before start-up from Q2R18)
: 2. Modify/Install design of Quad Cities Unit 1 Steam Dryer Lifting Eyes per EC 360571.
(Scheduled for completion during Q1M19 in spring 2006).
: 3. Similar corrective actions will be completed on the Dresden replacement dryers prior to installation.
Page 10 of 43


In addition, all four steam dryer lifting eyes were discovered out-of-position, with one lifting eye exhibiting thread damage to the lifting rod. This issue was originally in the scope of this RCA, but it was determined that the lifting eye concerns were not related to the dryer cracking issues. For this reason, the lifting eye issue was removed from the RCA scope, and transferred for evaluation as a separate Equipment Apparent Cause Evaluation (EACE) (AR# 471848-05). A summary of the results of this EACE appears below:
Identification of Missed Opportunities:
This RCA used the information presented in this event description (and the associated Event and Causal Factors chart in Att. 1) to identify potential issues and missed opportunities for earlier detection, or prevention of the three events in the scope of the RCA. These items are listed below and became the subject of more detailed analysis described in the next section.
Missed Opportunities for Earlier Detection or Prevention of Dryer Cracking:
: 1. Inadequate inspection of the May 2005 damage: Actions were identified in Ref. 1 & 8 to perform a liquid penetrant test (PT) of adjacent welds. The Field Deviation Disposition Request [FDDR]
(Ref. 8) was not clear in identifying specific welds to be inspected - it just specified, all adjacent welds in the areas that were distorted shall be subjected to PT examination. Interviews with QC personnel determined that only adjacent welds on the outside diameter (OD) of the skirt were PT examined. The weld between the vertical skirt plate and the horizontal base plate on the ID of the skirt was not examined either visually or via PT. This was a missed opportunity to determine the integrity of the base material and weld integrity on the skirt inside diameter (ID) and thus we cannot conclusively eliminate the skirt ID as a crack initiation site. The lack of inspection of the ID of the skirt also eliminated the potential to find the dimpled section of the skirt at the 140 and 220° locations which may have led to further analysis of the residual stress placed on the metal.
: 2. Inadequate disposition of May 2005 damage: In the original dryer design effort, the lower skirt hardware was included in the modeling as a super element. That is, because the as-designed load conditions on the dryer skirt are typically low and the size of the finite element model was already excessively large, the skirt details below the water line were not included in the finite element calculations with fine nodal granularity. The entire lower area is modeled as a lumped mass and stiffness matrices in the finite element calculations. This is appropriate if the service conditions stay inside the assumed as-designed bounds. However, once this portion of the unit had been subject to permanent, localized damage, a rigorous evaluation would have considered whether the dryer was subject to future degradation. This was not specifically included in the disposition of the damaged area.
: 3. Deficiencies in Design Change Development: A fundamental change in the design of the dryer caused the outer diameter of the dryer shell skirt plate to be reduced, in order that the drain channels could be on the exterior of the dryer assembly. (Note that the outer diameter of the horizontal skirt base plate was the same. The vertical skirt shell plate was reduced.) Exterior drain channels were used in an effort to reduce minor cracking commonly experienced in the area of internal drain channels in earlier designed BWR steam dryers. In addition, because the more robust replacement dryers were heavier, the designers looked for non-structural areas where weight could be reduced. For these reasons, the original design use of 2 continuous guide channels for both of the dryer guide rods, and (4) guide channels for the RPV support lugs were eliminated. These channels were each changed from being a continuous vertical guide path along the height of the dryer skirt, to being two-point (top and bottom) alignment connections (Dryer guide slots for alignment with the RPV guide rods), and Base Ring cutouts to pass through the RPV support lugs. The original guide channels for the RPV support lugs had the same 4 wide clearance as the new dryers base plate notches. The implication of this is that the tight tolerance on the rotational alignment is enforced at all axial positions during movement. It is this enforcement of rotational alignment that was compromised by the removal of the guide Page 11 of 43


Summary EACE 471848-05:  Dry er Lifting Lug Rotation Apparent cause
channels. The 4 wide notches in the base plate only enforce this alignment while the base plate is at the elevation of the RPV lugs, setting up the potential for misalignment at other dryer elevations. This, in conjunction with the small clearance (the RPV lugs are 3 wide, so the average clearance is 1/2 on each side) increase the probability that an impact would occur, by making a higher demand on the users to obtain the simultaneous alignment without impact. Thus a negative consequence of the revised dryer design sacrificed a tolerant and self-correcting configuration for a less tolerant configuration that invited interferences.
:  The design of the lifting eye retention method was inadequate to ensure positive engagement. The design provided no ability for ensuring adequate alignment. The recess was located on the lifting rod, which was contained within the th readed connection once the lifting eye was threaded on. The design relied entirely on external orienta tion of the lifting eyes, which provided no positive verification. In addition, the dimensions of the recess provided minimal o pportunity for successful engagement. Corrective Actions
: 4. Fabrication Ovality Issues: Fabrication deficiencies had already been identified prior to the May 2005 lift event. These deficiencies resulted during the welding of the two halves of the QC2 dryer at J. T. Cullen. This assembly process resulted in distortion of the dryer mid-support ring, skirt and base plate.
:    1. Modify/Install design of Quad Cities Unit 2 Steam Dryer Lifting Eyes to provide more robust anti-rotation. (Completed before start-up from Q2R18) 2. Modify/Install design of Quad Cities Unit 1 Steam Dryer Lifting Eyes per EC 360571. (Scheduled for completion during Q1M19 in spring 2006). 3. Similar corrective actions will be completed on the Dresden replacement dryers prior to installation.
The distorted as-built dryer base plate condition was identified, evaluated and addressed prior to shipping the dryer to Quad Cities under a Deviation Disposition Request (DDR) (Ref. 7).
Page 11 of 43 Identification of Missed Opportunities
Corrective measures were taken to prevent this distortion in the assembly of the subsequent dryer assemblies (QC 1 dryer). The distorted QC2 dryer was evaluated and accepted for use, with actions to install additional guidance constraints on the lower guide blocks. (Refs.7&9).       This evaluation focused on vessel clearances for installation and removal of the dryer but did not address potential for induced stresses on the dryer components resulting from the distortion.
:  This RCA used the information presented in this event description (and the associated Event and Causal Factors chart in Att. 1) to identify potential issues and missed opportunities for earlier detection, or prevention of the three events in the scope of the RCA. These items are listed below and became the subject of more detailed analysis described in the next section.
Despite the completion of these corrective actions to accommodate installation and removal of the distorted QC2 dryer, the assembly distortion still contributed to the excessive clearances between the dryer and dryer guide rods, and was cited as one of the two apparent causes in the ACE for the May 2005 events. These conditions indicate two missed opportunities:
* The potential for installation alignment issues was recognized after the ovality was identified but corrective actions were not successful in preventing the lift event.
* The potential for internal metal stresses induced from the ovality was not formally addressed in the DDR, FDDR, EACE, or ECs reviewed during this RCA.
Page 12 of 43


Missed Opportunities for Earlier Detecti on or Prevention of Dryer Cracking: 1. Inadequate inspection of the May 2005 damage: Actions were identified in Ref. 1 & 8 to perform a liquid penetrant test (PT) of adjacent welds. The Field Deviation Disposition Request [FDDR] (Ref. 8) was not clear in identifying specific welds to be inspected - it just specified, "all adjacent welds in the areas that were distorted shall be subjected to PT examination". Interviews with QC personnel determined that only adjacent welds on the outside diameter (OD) of the skirt were PT examined. The weld between the vertical skirt plate and the hori zontal base plate on the ID of the skirt was not examined either visually or via PT. This was a missed opportunity to determine the integrity of the base material and weld integrity on the skirt inside diameter (ID) and thus we cannot conclusively eliminate the skirt ID as a crack initiation site. The lack of inspection of the ID of the skirt also eliminated the potential to find the "dimpled" section of the skirt at the 140 and 220 locations which may have led to further analysis of the residual stress placed on the metal. 2. Inadequate disposition of May 2005 damage: In the original dryer design effort, the lower skirt hardware was included in the modeling as a "super element". That is, because the as-designed load conditions on the dryer skirt are typically low and the size of the finite element model was already excessively large, the skirt details below the water line were not included in the finite element calculations with fine nodal granularity. The entire lower area is modeled as a lumped mass and stiffness matrices in the finite element calculations. This is appropriate if the service conditions stay inside the assumed "as-designed" bounds. However, once this portion of the unit had been subject to permanent, localized damage, a rigorous evaluation would have considered whether the dryer was subject to future degradation. This was not specifically included in the disposition of the damaged area. 3. Deficiencies in Design Change Development: A fundamental change in the design of the dryer caused the outer diameter of the dryer shell skir t plate to be reduced, in order that the drain channels could be on the exterior of the dryer assembly.  (Note that the outer diameter of the horizontal skirt base plate was the same. The vertical skirt shell plate was reduced.)  Exterior drain channels were used in an effort to reduce minor cracking commonly experienced in the area of internal drain channels in earlier designed BWR steam dr yers. In addition, because the more robust replacement dryers were heavier, the designers looked for non-structural areas where weight could be reduced.
IV. Analysis:
For these reasons, the original design use of 2 continuous guide channels for both of the dryer gui de rods, and (4) guide channels for the RPV support lugs were eliminated. These channels were each changed from being a continuous vertical guide path along the height of the dryer skirt, to being two-point (top and bottom) alignment connections (Dryer guide slots for alignment with the RP V guide rods), and Base Ring cutouts to pass through the RPV support lugs. Th e original guide channels fo r the RPV support lugs had the same 4" wide clearance as the new dryer's base plate notches. The implication of this is that the tight tolerance on the rotational alignment is enforced at all axial positions during movement. It is this enforcement of rotational alignment that was compromised by the removal of the guide Page 12 of 43 channels. The 4" wide notches in the base plate only "enforce" this alignment while the base plate is at the elevation of the RPV lugs, setting up the potential for misalignment at other dryer elevations. This, in conjunction with the small clearance (the RPV lugs are 3" wide, so the average clearance is 1/2" on each side) increase the probability that an impact would occur, by making a higher demand on the users to obtain the simultaneous alignment without impact. Thus a negative consequence of the revised dryer design sacrificed a tolera nt and self-correcting configuration for a less tolerant confi guration that invited interferences. 4. Fabrication "Ovality" Issues: Fabrication deficiencies had already been identified prior to the May 2005 lift event. These deficiencies resulted during the welding of the two halves of the QC2 dryer at J. T. Cullen. This assembly process resulted in distortion of the dryer mid-support ring, skirt and base plate. The distorted as-built dryer base plate condition was identified, evaluated and addressed prior to shipping the dryer to Quad Cities under a Deviation Disposition Request (DDR) (Ref. 7). Corrective measures were taken to prevent this distortion in the assembly of the subsequent dryer assemblies (QC 1 dryer). The distorted QC2 dryer was evaluated and accepted for use, with actions to install additional guidance constraints on the lower guide blocks. (Refs.7&9). This evaluation focused on vessel clearances for installation and removal of the dryer but did not address potential for induced stresses on the dryer components resulting from the distortion. Despite the completion of these corrective actions to accommodate installation and removal of the distorted QC2 dryer, the assembly distortion still contributed to the excessive clearances between the dryer and dryer guide rods, and was cited as one of the two apparent causes in the ACE for the May 2005 events. These condi tions indicate two missed opportunities: The potential for installation alignment issues was recognized after the "ovality" was identified but corrective actions were not successful in preventing the lift event. The potential for internal metal stresses induced from the "ovality" was not formally addressed in the DDR, FDDR, EACE, or EC's reviewed during this RCA. 
Several root cause analysis techniques were used in this investigation. Initially, an Event and Causal Factor Chart (Att. 1) was created to document the known sequence of events, and conditions. This document was used to identify an initial strategy and direction, including the decision to divide the concerns into three issues (Dryer Skirt Crack, Dryer End Plate Crack, and Lifting Lug Concerns). The investigation team then used Failure Modes and Effects Analysis (FMEA) to identify potential failure modes. These potential failure modes were documented on a Complex Troubleshooting Failure Mode Tree (FMT) (ref. MA-AA-716-004, Att.2 pages 3 and 4). Each failure mode was then broken down into potential causes with associated validation and action steps. These actions were then prioritized according to the probability of the failure mode being a causal factor and the availability of data (some validation steps were able to be completed early in the investigation while others required additional time for analysis). The FMTs for Event 1 and Event 2 appear in this report as attachments 5& 6 respectively.
 
The Lifting Lug Concerns were later determined to be a separate issue from the Dryer Cracking and transferred from the scope of this RCA to EACE AR# 471848-05. For this reason the FMT related to the lifting lug issues is not included as an attachment to this RCA. Similarly, as the Q2R18 dryer inspections continued, and additional issues were identified, the Latch Box Cracking near the 220° azimuth was added to the RCA scope as Event 3 based on a potential linkage to the other two issues. A new FMT was not created for this event because it was evident that the analysis and strategy used for Event 1 (Skirt Crack) and Event 2 (End Vane Bank Crack) were appropriate and bounding for Event 3 (Latch Box Crack).
Page 13 of 43 IV. Analysis:
The FMT charts identified a set of low probability and higher probability failure modes.
Several root cause analysis tec hniques were used in this invest igation. Initially, an Event and Causal Factor Chart (Att. 1) was created to document the known sequence of events, and conditions. This document was used to identify an initial strategy and direction, including the decision to divide the concerns into three issues (Dryer Skirt Crack, Dryer End Plate Crack, and Lifting Lug Concerns). The investigation team then used Failure Modes and Effects Analysis (FMEA) to identify potential failure modes. These potential failure modes were documented on a Comp lex Troubleshooting Failure Mode Tree (FMT) (ref. MA-AA-716-004, Att.2 pages 3 and 4). Each failure mode was then broken down into potential causes with associated validation and action steps. These actions were then prioritized according to the probability of the failure mode being a causal factor and the availability of data (some validation steps were able to be completed early in the investigation while others required additional time for analysis). The FMT's for Event 1 and Event 2 appear in this report as attachme nts 5& 6 respectively. The Lifting Lug Concerns were later determin ed to be a separate issue from the Dryer Cracking and transferred from the scope of this RCA to EACE AR# 471848-05. For this reason the FMT related to the lifting lug issues is not included as an attachment to this RCA. Similarly, as the Q2R18 dryer inspectio ns continued, and addi tional issues were identified, the Latch Box Cracking near the 220° azimuth was added to the RCA scope as Event 3 based on a potential linkage to the ot her two issues. A new FMT was not created for this event because it was evident that the analysis and strategy used for Event 1 (Skirt Crack) and Event 2 (End Vane Bank Crack) were appropriate and bounding for Event 3 (Latch Box Crack). The FMT charts identified a set of low probability and higher probability failure modes. The lower probability items were set aside allowing a focus on the higher probability items which included: Design related issues where the analysis used might have underestimated the loads the replacement dyers would be subject to, and also underestimated the stress conditions resulting from the skirt base cutouts. Design related issues that effected the resulting "lift event". Fabrication errors, which resulted in the skirt base ring ovality. Installation damage resulting from the "lift event".
The lower probability items were set aside allowing a focus on the higher probability items which included:
* Design related issues where the analysis used might have underestimated the loads the replacement dyers would be subject to, and also underestimated the stress conditions resulting from the skirt base cutouts.
* Design related issues that effected the resulting lift event.
* Fabrication errors, which resulted in the skirt base ring ovality.
* Installation damage resulting from the lift event.
These probable failures modes were reviewed using additional RCA tools such as:
These probable failures modes were reviewed using additional RCA tools such as:
TapRoot, Cause and Effect Analysis, and Ba rrier Analysis. The RCA also utilized a significant amount of technical analysis including metallurgical testing of samples of the U-2 Dryer skirt and baseplate, and computerized structural an alysis. This analysis is described in more detail below:
TapRoot, Cause and Effect Analysis, and Barrier Analysis. The RCA also utilized a significant amount of technical analysis including metallurgical testing of samples of the U-2 Dryer skirt and baseplate, and computerized structural analysis. This analysis is described in more detail below:
Page 13 of 43


Page 14 of 43 A. Structural Analysis Summary:
A. Structural Analysis Summary:
Detailed finite element models of the dryer skirt and other dryer components were developed or upgraded. Multiple elastic and inelastic finite element analyses were run to simulate the conditions that would have caused the observed deformations. These simulations were used as sensitivity evaluati ons such that some postulated loadings could be eliminated (i.e., if the loads and stresses resulting from some scenarios couldn't have caused the observed deformation, the scenario could be eliminated). Some of these analyses were used to approximate the material condition resulting from these events and to assess the extent of the possible degradation.
Detailed finite element models of the dryer skirt and other dryer components were developed or upgraded. Multiple elastic and inelastic finite element analyses were run to simulate the conditions that would have caused the observed deformations. These simulations were used as sensitivity evaluations such that some postulated loadings could be eliminated (i.e., if the loads and stresses resulting from some scenarios couldnt have caused the observed deformation, the scenario could be eliminated). Some of these analyses were used to approximate the material condition resulting from these events and to assess the extent of the possible degradation.
: 1. The original full steam dryer finite element model contained a super element for the submerged portion of the skirt and water. The skirt in the super element did not have the detail of the base plate cut outs or gussets located on either side of the cutout. A local solid 3D detailed finite element model was created for analysis of the failure location. The analysis validated that the cut out modeling was not significant in determining the skirt stresses & modal response. (Ref. 29)
: 1. The original full steam dryer finite element model contained a super element for the submerged portion of the skirt and water. The skirt in the super element did not have the detail of the base plate cutouts or gussets located on either side of the cutout. A local solid 3D detailed finite element model was created for analysis of the failure location.
The analysis validated that the cut out modeling was not significant in determining the skirt stresses & modal response. (Ref. 29)
: 2. More detailed elastic-plastic analysis of the skirt cutout and gusset areas at 140° was completed. This analysis predicted 17.3% strain at the top of the gusset in the skirt panel.
: 2. More detailed elastic-plastic analysis of the skirt cutout and gusset areas at 140° was completed. This analysis predicted 17.3% strain at the top of the gusset in the skirt panel.
Strain at the edge of the gusset in the cut out was 4%, which corresponds to 55-60 ksi using elastic-plastic analysis. (Ref. 21)
Strain at the edge of the gusset in the cut out was 4%, which corresponds to 55-60 ksi using elastic-plastic analysis. (Ref. 21) This analysis also estimated the amount of loading needed to cause the observed deformation from the list event to be 47,000 pounds.
This analysis also estimated the amount of loading needed to cause the observed deformation from the list event to be 47,000 pounds. 3. An analysis was completed to estima te the corresponding reduction in the fatigue stress limits in the 140 azimuth Dryer Skirt Crack as a result of the lifting event. Excerpts from this analysis repo rt (Ref. 40) appears below:
: 3. An analysis was completed to estimate the corresponding reduction in the fatigue stress limits in the 140° azimuth Dryer Skirt Crack as a result of the lifting event.
" - given the higher plastic strain and complementary increase in strength of the deformed base ring location, the expected fatigue endurance properties would be significantly reduced due to mean stress e ffects. This effect can be calculated directly from the equations used by Ma njoine, et al [Ref. 41 of this RCA].
Excerpts from this analysis report (Ref. 40) appears below:
Although the region of interest was cold wo rked by the installa tion event [referred to as the "lifting event" in other sections of this RCA], the evaluation of the mean stress effect was performed based on the fatigue properties of annealed material.
given the higher plastic strain and complementary increase in strength of the deformed base ring location, the expected fatigue endurance properties would be significantly reduced due to mean stress effects. This effect can be calculated directly from the equations used by Manjoine, et al [Ref. 41 of this RCA].
Therefore, the evaluation should be viewed in qualitative rather than quantitative terms. For conservatism, the loading was considered as stress controlled in the determination of the mean stress effect, i.e. the range of Pl + Pb +Q was assumed to exceed 27.2 ksi. The impact of an assumed residual (mean) stress of 60 ksi  
Although the region of interest was cold worked by the installation event [referred to as the lifting event in other sections of this RCA], the evaluation of the mean stress effect was performed based on the fatigue properties of annealed material.
Therefore, the evaluation should be viewed in qualitative rather than quantitative terms. For conservatism, the loading was considered as stress controlled in the determination of the mean stress effect, i.e. the range of Pl + Pb +Q was assumed to exceed 27.2 ksi. The impact of an assumed residual (mean) stress of 60 ksi would be a 30% reduction in the allowable while the assumption of a 70 ksi yield strength to represent the local mean stress would reduce the allowable by 50%.
These levels of reduction in fatigue properties are very likely given the deformation and the constraint imposed by the several intersecting welds present at the base ring cut out corner-solid gusset-skirt region where crack initiation occurred.
In summary, the plastic deformation would be expected to lead to a high residual mean stress. Consistent with the understanding of fatigue behavior in the presence Page 14 of 43


would be a 30% reduction in the allowable while the assumption of a 70 ksi yield strength to represent the local mean stress would reduce the allowable by 50%.
of high mean stresses, the fatigue endurance limit would be reduced. Based on the conservative evaluation, the reduction in endurance limit would be expected to be a maximum of 50%.
These levels of reduction in fatigue properties are very likely given the deformation and the constraint imposed by the several intersecting welds present at the base ring cut out corner-solid gusset-skirt region where crack initiation occurred."
: 3. Hydrodynamic and acoustic loading on the dryer were re-evaluated. Ref. 21 noted that the turbulent water loads acting on the dryer skirt were not analytically evaluated, but the skirt is in a relatively quiet region near the vessel wall. This indicates that any loading on the skirt from the feedwater flow and separator flow will be a turbulent buffeting from the mixing of these flow streams below the skirt. Since the replacement dryer skirt design should be more able to resist these turbulent loads (replacement dryers used 3/8 thick vs.
"In summary, the plastic deformation would be expected to lead to a high residual mean stress. Consistent with the understan ding of fatigue behavi or in the presence Page 15 of 43 of high mean stresses, the fatigue endurance limit would be reduced. Based on the conservative evaluation, the reduction in endurance limit w ould be expected to be a maximum of 50%."
1/4 thick plate and the drain channel design/fabrication moved the weld away from the discontinuity), it can be concluded that the water loading on the replacement dryer skirt would not present any fatigue issues.
: 3. Hydrodynamic and acoustic loading on the dr yer were re-evaluated. Ref. 21 noted that the turbulent water loads acting on the dryer skirt were not analytically evaluated, but the skirt is in a relatively quiet region near the vessel wall. This indicates that any loading on the skirt from the feedwater flow and separator flow will be a turbulent buffeting from the mixing of these flow streams below the skirt. Since the replacement dryer skirt design should be more able to resist these turbulent loads (replacement dryers used 3/8" thick vs.
The July 2005 report on QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis Based on Measured EPU Conditions (Ref. 35) was reviewed and it was noted that there are additional hydrodynamic loads, assessed to be too low to be of consequence. An acoustic load frequency at 155 Hz appears on the strain gauges and accelerometers and based on the magnitude of the response in power spectral densities is the most dominant mode in the reactor. This mode has been attributed to the Electromatic relief valve (ERV) stub tube resonance and is included in the load basis for the analysis.
1/4" thick plate and the drain channel design/fabrication moved the weld away from the discontinuity), it can be concluded that the water loading on the replacement dryer skirt would not present any fatigue issues. The July 2005 report on "QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis Based on Measured EPU Conditions (Ref. 35) was reviewed and it was noted that there are additional hydrodynamic loads, assessed to be too low to be of consequence. An acoustic load frequency at 155 Hz appears on the strain gauges and accelerometers and based on the magnitude of the response in power spectral densities is the most dominant mode in the reactor. This mode has been attributed to the Electromatic relief valve (ERV) stub tube resonance and is included in the load basis for the analysis. Further modal analysis concludes that the failed skirt does not have modes in the low frequency range. This means that while the loads may be impacting the dryer, they are not driving structural resonan ces. In addition, these frequenc ies would affect the entire dryer, not just the skirt panel. This results in a conclusion that these loads are not a causal factor in this RCA.
Further modal analysis concludes that the failed skirt does not have modes in the low frequency range. This means that while the loads may be impacting the dryer, they are not driving structural resonances. In addition, these frequencies would affect the entire dryer, not just the skirt panel. This results in a conclusion that these loads are not a causal factor in this RCA.
: 4. A detailed stress analysis of the drye r lifting event was completed (Ref. 36). The analysis report concluded: "In this analysis the lifting forces we re applied unevenly in various configurations on the full dryer finite element model in order to assess if the lifting event could have caused crack initiation in the vane ba nk end plates and/or latch box. The results indicate that no lifting cases could initiate a crack in either the inner vane bank end plates or latch box corner."
: 4. A detailed stress analysis of the dryer lifting event was completed (Ref. 36). The analysis report concluded: In this analysis the lifting forces were applied unevenly in various configurations on the full dryer finite element model in order to assess if the lifting event could have caused crack initiation in the vane bank end plates and/or latch box. The results indicate that no lifting cases could initiate a crack in either the inner vane bank end plates or latch box corner.
B. Follow-up Inspections Summary
B. Follow-up Inspections Summary
: 1. The inside of the dryer skirt at the 20° azimuth where previous damage from impact with the separator guide rods had been noted were re-inspected and evaluated. This evaluation concluded that the damage was small with no deformation of the base ring. While the minor damaged was repaired, the conclusion remains that impact in this area was not a causal factor in any of the cracking events in the scope of this RCA.
: 1. The inside of the dryer skirt at the 20° azimuth where previous damage from impact with the separator guide rods had been noted were re-inspected and evaluated. This evaluation concluded that the damage was small with no deformation of the base ring.
: 2. The inside diameter of the dryer skirt ri ng was re-inspected and evaluated at the 140°, 220° and 320° areas. The 140 ° area already requ ired repair of the identified skirt and base ring cracking. The 220° area had a sim ilar amount of base ring and skirt plate deformation as the 140° area, but no observable cracking. The similar deformation was Page 16 of 43 the major factor in the decision to cut out and replace the deformed material at the 220° area despite no observable cracking (Ref
While the minor damaged was repaired, the conclusion remains that impact in this area was not a causal factor in any of the cracking events in the scope of this RCA.
: s. 27 & 32). The 320° area had gusset deformation less than half that at the 140° location, and no ID skirt or base ring deformation so this area was analyzed to leave "as is". 
: 2. The inside diameter of the dryer skirt ring was re-inspected and evaluated at the 140°,
220° and 320° areas. The 140 ° area already required repair of the identified skirt and base ring cracking. The 220° area had a similar amount of base ring and skirt plate deformation as the 140° area, but no observable cracking. The similar deformation was Page 15 of 43


the major factor in the decision to cut out and replace the deformed material at the 220° area despite no observable cracking (Refs. 27 & 32). The 320° area had gusset deformation less than half that at the 140° location, and no ID skirt or base ring deformation so this area was analyzed to leave as is.
C. Metallurgical Analysis Summary:
C. Metallurgical Analysis Summary:
Cut out samples of the cracked areas of the dryer skirt were sent out to GE's metallurgical labs at Vallecitos, CA. The purpose for the testing was to determine the  
Cut out samples of the cracked areas of the dryer skirt were sent out to GEs metallurgical labs at Vallecitos, CA. The purpose for the testing was to determine the following:
 
following:
: 1. Site of crack initiation
: 1. Site of crack initiation
: 2. Mode of crack propagation
: 2. Mode of crack propagation
: 3. Material characteristics germane to the investigation
: 3. Material characteristics germane to the investigation
: 4. Likely cause of cracking The results of these examinations were documented in "GE-NE-0000-0052-9666, QC U-2 Replacement Steam Dryer Metallurgical Evaluation" (Ref. 19). In addition GE completed a separate evaluation of the Transgranular Stress Corrosion Cracking (TGSCC) identified in these metallurgical samples in the report listed as reference 16 to this RCR. Excerpts of the Executive Summary and selected sections from the metallurgical report is report are reproduced below:
: 4. Likely cause of cracking The results of these examinations were documented in GE-NE-0000-0052-9666, QC U-2 Replacement Steam Dryer Metallurgical Evaluation (Ref. 19). In addition GE completed a separate evaluation of the Transgranular Stress Corrosion Cracking (TGSCC) identified in these metallurgical samples in the report listed as reference 16 to this RCR.
Executive Summary of GE Metallurgical Evaluation (Ref. 19)
Excerpts of the Executive Summary and selected sections from the metallurgical report is report are reproduced below:
:  During inspection of the replacement steam dryer at Quad Cities Unit 2 during Q2R18, cracking was observed in the skir t and base plate at the 140 degree location. Samples were removed from th e dryer and sent to GE's Vallecitos Nuclear Center for further evaluation.
Executive Summary of GE Metallurgical Evaluation (Ref. 19):
Visual examination of the samples showed a relatively smooth straight fracture in the skirt plate, consistent with a fatigue mechanism. Examination of the sample taken from the base plate to skirt plate weld confirmed the fatigue cracking mode. No evidence of ductile tearing (i.e., overload) was found. Near the inner diameter (ID) of the base plate, the fracture exhibited slight twisting, which suggests there was a torsional component to the loading by the time the crack progressed to the  
During inspection of the replacement steam dryer at Quad Cities Unit 2 during Q2R18, cracking was observed in the skirt and base plate at the 140 degree location. Samples were removed from the dryer and sent to GEs Vallecitos Nuclear Center for further evaluation.
Visual examination of the samples showed a relatively smooth straight fracture in the skirt plate, consistent with a fatigue mechanism. Examination of the sample taken from the base plate to skirt plate weld confirmed the fatigue cracking mode.
No evidence of ductile tearing (i.e., overload) was found. Near the inner diameter (ID) of the base plate, the fracture exhibited slight twisting, which suggests there was a torsional component to the loading by the time the crack progressed to the ID. The cracking appeared to have initiated in the base plate region and progressed upward into the skirt plate. Although no clear initiation site could be identified, the fracture most likely initiated near the OD of the base plate.
Optical metallographic examination of the skirt plate-to-base plate weld cross sections showed two key features: (1) the root areas of the ID and OD welds contained lack of penetration; and (2) transgranular, branched cracking characteristic of transgranular stress corrosion cracking (TGSCC) initiated from the root area and propagated into the skirt and base plate in both the 140 and 220 degree sections. Neither feature, however, could be identified as an initiator of the Page 16 of 43


ID. The cracking appeared to have in itiated in the base plate region and progressed upward into the skirt plate.
observed fatigue cracking. Some increase in hardness was noted in the skirt plate, consistent with the observed deformation. The material chemistries were consistent with austenitic stainless steels.
Although no clear initia tion site could be identified, the fracture most likely ini tiated near the OD of the base plate. Optical metallographic examination of the skirt plate-to-base plate weld cross sections showed two key features: (1) the root areas of the ID and OD welds contained lack of penetration; and (2) transgranular, branched cracking characteristic of transgranular stress corrosion cracking (TGSCC) initiated from the root area and propagated into the skir t and base plate in both the 140 and 220 degree sections. Neither feature, however, c ould be identified as an initiator of the Page 17 of 43 observed fatigue cracking. Some increase in hardness was noted in the skirt plate, consistent with the observed deformation. The material chemistries were consistent with austenitic stainless steels. Based on the observations, the material failed by mechanical fatigue, initiated towards the OD of the base plate region. Given the deformation observed in the samples examined, the stresses introduced into the cut-out region by bending and the location of the cracking, it is likely that the lifti ng event contributed to the observed failure. Excepts from Discussion Section of GE Metallurgical Evaluation (Ref. 19):
Based on the observations, the material failed by mechanical fatigue, initiated towards the OD of the base plate region. Given the deformation observed in the samples examined, the stresses introduced into the cut-out region by bending and the location of the cracking, it is likely that the lifting event contributed to the observed failure.
Subsequent SEM (Scanning Electron Microscopy) examination of the fracture surface confirmed the transgranular nature of the cracking, consistent with fatigue. All regions that were examined were consistent with a fatigue cracking mechanism, with no evidence of ductile overload found. Some lack of penetration was noted in the weld root, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. Inclusions in the weld root were also identified; based on the EDS [Energy Dispersive Spectroscopy] analysis, these inclusions most likely resulted from the original welding process, and were not associated with the failure. Optical metallography confirmed that the we lds were fabricated with at least two passes, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. In additi on, lack of penetration in the weld root was observed in all of the six cross sections examined. Optical metallography also confirmed that the material was in a solution annealed condition, with some evidence of strain hardening in the base plate, as determined by microhardness. The areas of apparent strain hardening are consistent with the deformation from the lifting event. The cracking mode was transgranular with small secondary cracks, consistent with a fatigue mechanism. One additional observation was the presence of transgranular cracking in the weld root region of both the 140 and 220 samples. Given the branched nature, along with the presence of multiple indications in both the skirt and base plate regions, the most likely cause is TGSCC. TGSCC re quires three factors to be present:   (1) wetted environment; (2) aggressive species (e.g., halogens); and (3) stress. Wetted environment
Excepts from Discussion Section of GE Metallurgical Evaluation (Ref. 19):
: At the 140 degree location, th e weld root crevice was exposed to the environment Aggressive species: Given that the partial penetration weld was made by a flux-core process and weld fluxes typically c ontain fluorides for fluidity and wetting, the presence of fluorine in the weld r oot is not unexpect ed. In addition, the manufacturer of the weld flux confirmed that approximately 3% fluorine was present in the welding flux.
Subsequent SEM (Scanning Electron Microscopy) examination of the fracture surface confirmed the transgranular nature of the cracking, consistent with fatigue. All regions that were examined were consistent with a fatigue cracking mechanism, with no evidence of ductile overload found. Some lack of penetration was noted in the weld root, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. Inclusions in the weld root were also identified; based on the EDS [Energy Dispersive Spectroscopy]
Stress: Significant stress would be present from welding. [The deformation from the lifting event was also a source of stress.]  
analysis, these inclusions most likely resulted from the original welding process, and were not associated with the failure.
Optical metallography confirmed that the welds were fabricated with at least two passes, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. In addition, lack of penetration in the weld root was observed in all of the six cross sections examined. Optical metallography also confirmed that the material was in a solution annealed condition, with some evidence of strain hardening in the base plate, as determined by microhardness.
The areas of apparent strain hardening are consistent with the deformation from the lifting event. The cracking mode was transgranular with small secondary cracks, consistent with a fatigue mechanism.
One additional observation was the presence of transgranular cracking in the weld root region of both the 140 and 220 ° samples. Given the branched nature, along with the presence of multiple indications in both the skirt and base plate regions, the most likely cause is TGSCC. TGSCC requires three factors to be present:
(1) wetted environment; (2) aggressive species (e.g., halogens); and (3) stress.
Wetted environment: At the 140 degree location, the weld root crevice was exposed to the environment Aggressive species: Given that the partial penetration weld was made by a flux-core process and weld fluxes typically contain fluorides for fluidity and wetting, the presence of fluorine in the weld root is not unexpected. In addition, the manufacturer of the weld flux confirmed that approximately 3% fluorine was present in the welding flux.
Stress: Significant stress would be present from welding. [The deformation from the lifting event was also a source of stress.]
Page 17 of 43


Page 18 of 43 Since all three factors are present, TGSCC is the most likely cause of the observed transgranular, branched cracki ng in the weld root. Two factors, however, indicate that TGSCC did not contribute to initiation of the fatigue cracking: (1) On the fracture face, the transgranular cracking was consistent with fatigue. There were some secondary cracks, but no major network of secondary branched cracking that would characterize a TGSCC crack was found, and (2) the initiation region (see Figure 3-3(b) in Ref. 19) does not appear to be in the root of the weld. The directional features indi cate initiation on the OD surface. The laboratory examination confirmed that the primary fracture was one of mechanical fatigue; however, the exact in itiating location could not be identified.
Since all three factors are present, TGSCC is the most likely cause of the observed transgranular, branched cracking in the weld root. Two factors, however, indicate that TGSCC did not contribute to initiation of the fatigue cracking: (1) On the fracture face, the transgranular cracking was consistent with fatigue. There were some secondary cracks, but no major network of secondary branched cracking that would characterize a TGSCC crack was found, and (2) the initiation region (see Figure 3-3(b) in Ref. 19) does not appear to be in the root of the weld. The directional features indicate initiation on the OD surface. The laboratory examination confirmed that the primary fracture was one of mechanical fatigue; however, the exact initiating location could not be identified.
Key Conclusions from GE Metallurgical Analysis The GE metallurgical analysis proved to be a key component in this RCA. While the exact initiation mechanism of the dryer skirt plate could not be identified, the results did eliminate several of the potential failure mechanisms, and supported a determination of most probable causes.
Key Conclusions from GE Metallurgical Analysis The GE metallurgical analysis proved to be a key component in this RCA. While the exact initiation mechanism of the dryer skirt plate could not be identified, the results did eliminate several of the potential failure mechanisms, and supported a determination of most probable causes. This included the conclusions below:
This included the conclusions below:
: 1. Skirt plate cracking is consistent with fatigue cracking.
: 1. Skirt plate cracking is cons istent with fatigue cracking. 2. There is no evidence of ductile tearing. 3. Cracking appears to have initiated in the base plate region and then propagated into the skirt plate. 4. The fracture most likely initiated near the OD of the base plate. 5. TGSCC was observed in samples from both the 140 and 220 regions, but in neither case was the TGSSC identified as an initiator of the fatigue cracking. 6. Deformed areas exhibited some increase in metal hardness.
: 2. There is no evidence of ductile tearing.
: 3. Cracking appears to have initiated in the base plate region and then propagated into the skirt plate.
: 4. The fracture most likely initiated near the OD of the base plate.
: 5. TGSCC was observed in samples from both the 140° and 220° regions, but in neither case was the TGSSC identified as an initiator of the fatigue cracking.
: 6. Deformed areas exhibited some increase in metal hardness.
: 7. Material chemistries were consistent with austenitic stainless steel.
: 7. Material chemistries were consistent with austenitic stainless steel.
D. Interview Summaries:
D. Interview Summaries:
Interviews were completed with a number of key positions associated with this RCA. This included personnel from: Exelon Reactor Services, GE Installation, and GE Design personnel. A summary of the information from these interviews appears below:
Interviews were completed with a number of key positions associated with this RCA.
A. Reactor Services: 1. Use of Crane Load Cell Scoreboard:
This included personnel from: Exelon Reactor Services, GE Installation, and GE Design personnel. A summary of the information from these interviews appears below:
Originally installed as a corrective action from an OPEX event where a Dryer was attempted to be removed with only 3 of 4 hold-downs unlatched. Typical use of the scoreboard is that the weight of the component will be known and significant deviations will indicate a potential hang up of the load.
A. Reactor Services:
Page 19 of 43 If a significant change in expected load displayed occurs the "Technical Director" (TD) would be monitoring the display and would signal an emergency stop. For the Dryer installation the TD's were GE Supervisors. The Signal person for the load moves was typically a Venture Boilermaker assigned to the GE crew. Would an available scoreboard have made a difference in this event? Unsure - The Dryer lifting rigs are all metal com ponents so any increase in load would occur very quickly, likely before a response could be made by a lift crew, even in slow speeds. In other lifts where synthe tic lifting slings are used, the response time might be longer. (In this case, ther e is a potential that a load cell change could be responded to when the dryer metal starts to deform, and possibly before the deformation would become permanent.) The load cell display has been unreliable since installation. Several outages included lifts made where the scoreboard was inoperable.
: 1. Use of Crane Load Cell Scoreboard:
: 2. Dryer Issues: What are the "key points" in a Dryer lift (term noted in several IR's associated with this event)? A: Aligning the Dryer guides with the guide rods, and the interface between the RPV lugs and the Dryer support ring are considered key  
* Originally installed as a corrective action from an OPEX event where a Dryer was attempted to be removed with only 3 of 4 hold-downs unlatched.
 
* Typical use of the scoreboard is that the weight of the component will be known and significant deviations will indicate a potential hang up of the load.
points of this lift now and historically. Rx. Services was aware that the full-lengt h guide channels that existed on the old dryer no longer existed on the new dryers. Rx. Services had limited formal involveme nt with the design of the new dryers (i.e., did not participate in the project team). Rx. Services personnel signed off on the new design because they believed that it could be made to work with some additional care. They also were aware that GE personnel would supervise the initial Dryer insertion and that modifications would be made if needed to support successful installation and removal of the replacement dryers. (Some of the fit up issues would need to be field verified especially during the first installation). Initial insertion of the new dryer allo wed for a person to be located in the Refueling bulkhead to assist in alignment.
Page 18 of 43
This option will not be available in future lifts because they will be done underwater for dose control.
* If a significant change in expected load displayed occurs the Technical Director (TD) would be monitoring the display and would signal an emergency stop.
* For the Dryer installation the TDs were GE Supervisors.
* The Signal person for the load moves was typically a Venture Boilermaker assigned to the GE crew.
* Would an available scoreboard have made a difference in this event? Unsure -
The Dryer lifting rigs are all metal components so any increase in load would occur very quickly, likely before a response could be made by a lift crew, even in slow speeds. In other lifts where synthetic lifting slings are used, the response time might be longer. (In this case, there is a potential that a load cell change could be responded to when the dryer metal starts to deform, and possibly before the deformation would become permanent.)
* The load cell display has been unreliable since installation. Several outages included lifts made where the scoreboard was inoperable.
: 2. Dryer Issues:
* What are the key points in a Dryer lift (term noted in several IRs associated with this event)? A: Aligning the Dryer guides with the guide rods, and the interface between the RPV lugs and the Dryer support ring are considered key points of this lift now and historically.
* Rx. Services was aware that the full-length guide channels that existed on the old dryer no longer existed on the new dryers.
* Rx. Services had limited formal involvement with the design of the new dryers (i.e., did not participate in the project team).
* Rx. Services personnel signed off on the new design because they believed that it could be made to work with some additional care. They also were aware that GE personnel would supervise the initial Dryer insertion and that modifications would be made if needed to support successful installation and removal of the replacement dryers. (Some of the fit up issues would need to be field verified especially during the first installation).
* Initial insertion of the new dryer allowed for a person to be located in the Refueling bulkhead to assist in alignment. This option will not be available in future lifts because they will be done underwater for dose control.
B. GE Personnel:
B. GE Personnel:
Dryer Project Installation Personnel
Dryer Project Installation Personnel
: 1. What was included in the pre-job brief for this evolution? A: The pre-job brief prior to the initial dryer move focused on the movement from the refuel floor to the vessel, since this was an abnormal m ove and resulted in various load path issues. It also included di scussion of the dryer clearan ce issues and that the dryer Page 20 of 43 design was different and would require significant monitoring while being installed. 2. What process document covered this lift (procedure, traveler, etc.)?  A: The traveler provided the direction for initial installation of the dryer - Rev. 0 for the initial move and Rev. 1 for the final installation following modifications. The removal for modifications was performe d per the station reactor disassembly procedure. 3. What were considered "key points" in this lift?  Were they formally documented?
: 1. What was included in the pre-job brief for this evolution? A: The pre-job brief prior to the initial dryer move focused on the movement from the refuel floor to the vessel, since this was an abnormal move and resulted in various load path issues. It also included discussion of the dryer clearance issues and that the dryer Page 19 of 43
A: There were hold points when the drye r base ring was at 6-inches above the RPV lugs and again when the mounting block was 6-inches above the RPV lugs. 4. Why was the inoperable load cell scoreboard considered acceptable?  A: It is not unusual for load cell/displays to be ma lfunctioning at various plants.
Dryer Project Design Personnel The Dryer design was changed from full-length channels was to accommodate relocating the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. To be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channels on the outside of the skir
: t. Full-length guide rod channels previously integral to the skirt could no longer remain. The replacement dryer design uses a 4-point contact design which also minimizes weight increase. The new dryers are more structural ly robust through the use of heavier material. The increased weight has to be maintained within the structural capabilities of the existi ng RPV dryer support lugs. This installation hardware is consistent with the design of newer GE BWR's. There has been no experience of a similar "Lift Event" in these newer BWR's. The ovality event was noted as a factor in degrading the alignment of this QC U-2 replacement Dryer.   
 
Page 21 of 43 V. Evaluation:
This evaluation section is organized as follows: A. Table of all Causal Factors that this RCA concluded influenced this event. B. Additional discussion of the basis for cause determination.
 
C. Discussion of other event conditions th at were evaluated as potential causal factors, but rejected, how they were eliminated as causal factors, and their final disposition (no action required, addressed in "Programmatic/Organizational Issues, addressed in "Other Issues" section) The final section C is needed because th is RCA required extensive technical and analytical review and in some cases, cause determinations relied on elimination of other causes to support the RCA conclusion of root and contributing causes.
A. Table of Causal Factors Problem Statement Cause (describe the cause and identify whether it is a root cause or contributing cause) Basis for Cause Determination Event 1: Crack & deformation of dryer base plate and skirt
 
identified in
 
Q2R18. CF1a:  Lift Event- Design factors:
: 1) New dryer skirt base ring had cutouts to fit around RPV support
 
lugs, previous design had full
 
length channels.
: 2) New dryer has two dryer guide slots at top and bottom of skirt vs:
 
full-length channel in old design.
Root Cause Event 1: Crack & deformation of dryer base plate and skirt
 
identified in
 
Q2R18. CF1b. Lift Event - Fabrication: Ovality Results in Looser Installation Clearances -
 
Distortion/ovality of dryer base plate further degraded alignment
 
control provided by dryer guide
 
slots. Root Cause Note:  The basis for cause determination is  similar for CF1a, & CF2b and are combined below: Root cause supporting analysis concluded that the skirt region cracking would not have initiated had the Q2P03 dryer lift event not occurred. Lift event resulted from changes in dryer installation hardware, not from personnel errors during dryer removal. Tolerances between the dryer guide rod slots & guide rods allows for rotational movement of dryer resulting in skirt base plate cutouts not aligned with RPV
 
support lugs. Tolerance in guide components was further degraded by ovality issue.
See Evaluation of Lifting Event Causal Factors CF1a, CF1b (section after this table) for more details on basis.
Event 1: Crack &
deformation of
 
dryer base plate and skirt
 
identified in CF2: Disposition of damage from Q2P03 lift event concluded "use
 
as is". GE FDDR, and site
 
review concluded:
 
FDDR accepted condition as-is but did not fully evaluate the material effects of the damage (focus on fit issues). Assumed damage occurred in low stress Page 22 of 43 Problem Statement Cause (describe the cause and identify whether it is a root cause or contributing cause) Basis for Cause Determination Q2R18. Modify base ring for separator guide rods Run for 1 cycle  Repair/modify base ring for RPV Lugs in Q2R18 Contributing Cause regions. Inspections limited to visual & PT in the outside diameter areas. No detailed inspection of inside diameter. Since follow-up analysis in this RCA did not identify an exact initiation mechanism for the cracking, a more detailed analysis
 
during Q2P03 is unlikely to have changed the outcome. (For this reason, this issue is
 
considered a contributing cause rather
 
than a root cause). Retained as a contributing cause because of small possibility that more detailed inspections could have detected cracks in the skirt or base plate, specifically on inner diameter areas.
See "CF2:  Disposition of Lifting Event Prior to Start-up from Q2P03"  (Second section after this table) for more details on basis.
Event 1: Crack &
deformation of
 
dryer base plate and skirt
 
identified in
 
Q2R18. CF3: Analysis - Operating Cycle Impacts  Contributing Cause Operating pressure oscillation loads from MSL acoustics resulted in skirt base ring stresses that when combined with the
 
reduced fatigue endurance caused by the plastic deformation from the lift event, was adequate to initiate and propagate
 
cracking. Considered a causal factor in crack initiation and propagation but not a root cause because analysis has concluded that the operating loads are not sufficient to
 
initiate cracking on their own. Att. 4 of this RCA presents a comparison of the U-2 pressure sensor data with the areas that experienced damage, which
 
supports the conclusion that operating cycle impacts were not initiating factors or root causes to this event.
Event 2: Crack found in vane bank of "E" bank CF4 - Cracking in Gusset 19 of Vane Bank "E" End Plate Near the 320 Location - most The basis for the cause determination is photographic observation by the root cause team and GE's evaluation Page 23 of 43 Problem Statement Cause (describe the cause and identify whether it is a root cause or contributing cause) Basis for Cause Determination near 320  azimuth  probably due to assembly, and residual welding stresses, minimal weld thickness, proximity to a weld-stop (stress riser) and the presence of
 
operating vibration loads Root Cause (Reference 17). The "Lift Event" was rejected as a causal factor for this event using a detailed stress analysis  (Reference 36)
Event 3:  Latch
 
Box Crack at 220 azimuth CF5 - Cracking in the 220 Latch Box - Per Ref. 18, the most likely cause of the cracking is fatigue
 
cracking, the presence of a weld
 
end discontinuity and likely high weld residual stress at the corner
 
location.
Root Cause The basis for the cause determination is the analysis and evaluation discussed in Reference 18, which concludes that the


most likely cause of the cracking is the  
design was different and would require significant monitoring while being installed.
: 2. What process document covered this lift (procedure, traveler, etc.)? A: The traveler provided the direction for initial installation of the dryer - Rev. 0 for the initial move and Rev. 1 for the final installation following modifications. The removal for modifications was performed per the station reactor disassembly procedure.
: 3. What were considered key points in this lift? Were they formally documented?
A: There were hold points when the dryer base ring was at 6-inches above the RPV lugs and again when the mounting block was 6-inches above the RPV lugs.
: 4. Why was the inoperable load cell scoreboard considered acceptable? A: It is not unusual for load cell/displays to be malfunctioning at various plants.
Dryer Project Design Personnel
* The Dryer design was changed from full-length channels was to accommodate relocating the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. To be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channels on the outside of the skirt. Full-length guide rod channels previously integral to the skirt could no longer remain.
* The replacement dryer design uses a 4-point contact design which also minimizes weight increase. The new dryers are more structurally robust through the use of heavier material. The increased weight has to be maintained within the structural capabilities of the existing RPV dryer support lugs.
* This installation hardware is consistent with the design of newer GE BWRs.
There has been no experience of a similar Lift Event in these newer BWRs.
* The ovality event was noted as a factor in degrading the alignment of this QC U-2 replacement Dryer.
Page 20 of 43


presence of a weld end discontinuity and  
V. Evaluation:
This evaluation section is organized as follows:
A. Table of all Causal Factors that this RCA concluded influenced this event.
B. Additional discussion of the basis for cause determination.
C. Discussion of other event conditions that were evaluated as potential causal factors, but rejected, how they were eliminated as causal factors, and their final disposition (no action required, addressed in Programmatic/Organizational Issues, addressed in Other Issues section)
The final section C is needed because this RCA required extensive technical and analytical review and in some cases, cause determinations relied on elimination of other causes to support the RCA conclusion of root and contributing causes.
A. Table of Causal Factors Cause (describe the cause and identify Problem Statement    whether it is a root cause or contributing            Basis for Cause Determination cause)
Event 1: Crack &      CF1a: Lift Event- Design                    Note: The basis for cause determination is deformation of        factors:                                    similar for CF1a, & CF2b and are combined dryer base plate      1) New dryer skirt base ring had            below:
and skirt              cutouts to fit around RPV support
* Root cause supporting analysis concluded identified in          lugs, previous design had full                  that the skirt region cracking would not Q2R18.                length channels.                                have initiated had the Q2P03 dryer lift
: 2) New dryer has two dryer guide                event not occurred.
slots at top and bottom of skirt vs:
* Lift event resulted from changes in dryer full-length channel in old design.              installation hardware, not from personnel Root Cause                                      errors during dryer removal.
Event 1: Crack &      CF1b. Lift Event - Fabrication:
* Tolerances between the dryer guide rod deformation of        Ovality Results in Looser                      slots & guide rods allows for rotational dryer base plate      Installation Clearances -                      movement of dryer resulting in skirt base and skirt              Distortion/ovality of dryer base                plate cutouts not aligned with RPV identified in          plate further degraded alignment                support lugs.
Q2R18.                control provided by dryer guide
* Tolerance in guide components was slots.                                          further degraded by ovality issue.
Root Cause                                  See Evaluation of Lifting Event Causal Factors CF1a, CF1b (section after this table) for more details on basis.
Event 1: Crack &      CF2: Disposition of damage from
* FDDR accepted condition as-is but did deformation of        Q2P03 lift event concluded use                not fully evaluate the material effects of dryer base plate      as is. GE FDDR, and site                      the damage (focus on fit issues).
and skirt              review concluded:
* Assumed damage occurred in low stress identified in Page 21 of 43


likely high weld residual stress at the  
Cause (describe the cause and identify Problem Statement  whether it is a root cause or contributing              Basis for Cause Determination cause)
 
Q2R18.
corner location. The "Lift Event" was rejected as a causal factor for this event using a detailed stress analysis  (Reference 36)
* Modify base ring for                      regions.
separator guide rods
* Inspections limited to visual & PT in the
* Run for 1 cycle                            outside diameter areas. No detailed
* Repair/modify base ring for                inspection of inside diameter.
RPV Lugs in Q2R18
* Since follow-up analysis in this RCA did not identify an exact initiation mechanism Contributing Cause                              for the cracking, a more detailed analysis during Q2P03 is unlikely to have changed the outcome. (For this reason, this issue is considered a contributing cause rather than a root cause).
* Retained as a contributing cause because of small possibility that more detailed inspections could have detected cracks in the skirt or base plate, specifically on inner diameter areas.
See CF2: Disposition of Lifting Event Prior to Start-up from Q2P03 (Second section after this table) for more details on basis.
Event 1: Crack &    CF3: Analysis - Operating Cycle
* Operating pressure oscillation loads from deformation of      Impacts                                        MSL acoustics resulted in skirt base ring dryer base plate                                                    stresses that when combined with the and skirt                                                          reduced fatigue endurance caused by the identified in      Contributing Cause plastic deformation from the lift event, Q2R18.                                                              was adequate to initiate and propagate cracking.
* Considered a causal factor in crack initiation and propagation but not a root cause because analysis has concluded that the operating loads are not sufficient to initiate cracking on their own.
* Att. 4 of this RCA presents a comparison of the U-2 pressure sensor data with the areas that experienced damage, which supports the conclusion that operating cycle impacts were not initiating factors or root causes to this event.
Event 2: Crack      CF4 - Cracking in Gusset 19 of
* The basis for the cause determination is found in vane      Vane Bank E End Plate Near                    photographic observation by the root bank of E bank    the 320° Location - most                        cause team and GEs evaluation Page 22 of 43


Cause (describe the cause and identify Problem Statement    whether it is a root cause or contributing          Basis for Cause Determination cause) near 320 °            probably due to assembly, and                (Reference 17).
azimuth                residual welding stresses,
* The Lift Event was rejected as a causal minimal weld thickness,                      factor for this event using a detailed stress proximity to a weld-stop (stress              analysis (Reference 36) riser) and the presence of operating vibration loads Root Cause Event 3: Latch        CF5 - Cracking in the 220° Latch
* The basis for the cause determination is Box Crack at          Box - Per Ref. 18, the most likely            the analysis and evaluation discussed in 220° azimuth          cause of the cracking is fatigue              Reference 18, which concludes that the cracking, the presence of a weld              most likely cause of the cracking is the end discontinuity and likely high            presence of a weld end discontinuity and weld residual stress at the corner            likely high weld residual stress at the location.                                    corner location.
Root Cause
* The Lift Event was rejected as a causal factor for this event using a detailed stress analysis (Reference 36)
B. Discussion of the Basis for Cause Determination for Three RCA Events.
B. Discussion of the Basis for Cause Determination for Three RCA Events.
Event 1: Crack & deformation of dryer base plate and skirt.
Event 1: Crack & deformation of dryer base plate and skirt.
: 1. CF1a, CF1b: - Lifting Event Causal Factors A. Lifting Event: The May 2005 "Lifting Event" where the dryer was damaged from impact of the skirt base ring with the RPV lugs was a causal factor that contributed to the dryer cracks discovered in Q2R18. An apparent cause evaluation (ACE) was completed and approved in May 2005. This RCA reviewed this ACE and determined it to be an appropriate starting point for further analysis to determine why the event occurred.
: 1. CF1a, CF1b: - Lifting Event Causal Factors A. Lifting Event: The May 2005 Lifting Event where the dryer was damaged from impact of the skirt base ring with the RPV lugs was a causal factor that contributed to the dryer cracks discovered in Q2R18. An apparent cause evaluation (ACE) was completed and approved in May 2005. This RCA reviewed this ACE and determined it to be an appropriate starting point for further analysis to determine why the event occurred.
 
The ACE (AR 334383) concluded:
The ACE (AR 334383) concluded:  
Two apparent causes were identified for this ACE. First, lack of clearance between the Dryer base ring plate and the Separator guide rods resulted in damage to the ring plate and shifting of the Dryer that caused minor damage to two of the seismic support blocks. Second, excessive clearance between the Dryer guide rods and the Dryer (guide slots) allowed the Dryer to move enough that the close tolerance notches in the Dryer skirt base ring plate no longer aligned with the RPV dryer hold-down lugs. This allowed the ring plate to catch on the underside of the lugs and result in deformation of the ring plate in three areas.
"Two apparent causes were identified for this ACE. First, lack of clearance between the Dryer base ring plate and the Separator guide rods resulted in damage to the ring plate and shifting of the Dryer that caused minor damage to two of the seismic support blocks. Second, excessive clearance between the Dryer guide rods and the Dryer (guide slots) allowed the Dryer to move enough that the close tolerance notches in the Dryer skirt base ring plate no longer aligned with the RPV dryer hold-down lugs. This allowed the ring plate to catch on the underside of the lugs and result in deformation of the ring plate in three areas
Page 23 of 43
."
Page 24 of 43 This RCA considers the lack of clearance between the dryer skirt base ring and the separator guide rods to be an initiating event, but not a causal factor because the dryer is designed to be installed and removed as many times as needed to support plant operations. The interference with the separator guide rod was the reason for dryer removal in this case, but not the reason for the lift event. Therefore the next level of "Why" focused on the excessive clearance with the guide rods, and the close tolerances between the skirt base ring notches and the RPV lugs.
This RCA did consider the possibility that the cause of the impact was related to human performance issues with the crew removing the Dryer in Q2P03. This consideration arose from the fact that the U-2 Dryer was installed without damage twice during Q2P03, and removed once during Q2R18.  (The Q2R18 removal was under the same


configuration and close tolerances as Q2P03 since the modifications to improve this condition had not been completed yet). Information from interviews with personnel involved in the successful moves of the U-2 dryer, support a position that while the dryer can physically be removed under the configura tion existing in Q2P03, the tolerances are such that an unacceptable risk of impact exists even with a reasonable measure of care. This information coupled with the results of the previously approved ACE led to a conclusion that the causal factors of the lift event were more related to the hardware clearance issues than crew human performance. Therefore the RCA pursued a "Cause and Effect Analysis" on the changes to desi gn of the dryer insta llation hardware which resulted in the increased clearance with the guide rods, and the clos e tolerances between the skirt base ring notches and the RPV lugs noted in the ACE.  
This RCA considers the lack of clearance between the dryer skirt base ring and the separator guide rods to be an initiating event, but not a causal factor because the dryer is designed to be installed and removed as many times as needed to support plant operations. The interference with the separator guide rod was the reason for dryer removal in this case, but not the reason for the lift event. Therefore the next level of Why focused on the excessive clearance with the guide rods, and the close tolerances between the skirt base ring notches and the RPV lugs.
This RCA did consider the possibility that the cause of the impact was related to human performance issues with the crew removing the Dryer in Q2P03. This consideration arose from the fact that the U-2 Dryer was installed without damage twice during Q2P03, and removed once during Q2R18. (The Q2R18 removal was under the same configuration and close tolerances as Q2P03 since the modifications to improve this condition had not been completed yet). Information from interviews with personnel involved in the successful moves of the U-2 dryer, support a position that while the dryer can physically be removed under the configuration existing in Q2P03, the tolerances are such that an unacceptable risk of impact exists even with a reasonable measure of care.
This information coupled with the results of the previously approved ACE led to a conclusion that the causal factors of the lift event were more related to the hardware clearance issues than crew human performance. Therefore the RCA pursued a Cause and Effect Analysis on the changes to design of the dryer installation hardware which resulted in the increased clearance with the guide rods, and the close tolerances between the skirt base ring notches and the RPV lugs noted in the ACE.
Cause & Effects Analysis - Design Changes to Dryer Installation Hardware (CF1a)
: 1. What were the changes?
Dryer Guide Device Clearance: The previous dryer had two guide channels that ran the outside length of the dryer. Once the channel was engaged onto the RPV dryer guide rods, little movement occurred as the dryer was installed into the RPV. Similarly, these full-length channels allowed for less movement when the dryer was removed, when compared to the new dryer design that uses dryer guide slots at the top and bottom of the Dryer Skirt. On the replacement steam dryer there are only 4 points of contact between the dryer and guide rods: - two at 0 and 180° on the base ring, and: -two at 0 and 180° on the mid-support ring. When the mid-support ring is not engaged with the dryer guide rods (i.e, the support ring is higher than the top of the upper dryer guide rod brackets),
there are only 2 points of contact between the dryer and guide rods, at 0 and 180° on the base plate. Stated another way, only when the dryer base plate is 2 or more below the bottom of the RPV dryer support bracket (vessel lugs) will there be 4 points of contact.
Thus, there are only 2 points of contact between the dryer and guide rods any time the dryer base plate is at the same elevation as the RPV dryer support brackets (vessel lugs).
The dryer is therefore much less constrained in terms of the dryer/guide rod interface in the replacement design than it was in the original design, especially when the dryer base plate is at the same elevation as the RPV dryer support brackets (vessel lugs).
Skirt Base Ring Cutouts for RPV Support Lugs: The previous dryer used a channel mechanism to allow the dryer skirt to pass along the 4 RPV lugs. The new dryer design had cutouts at the skirt base ring that were nominally 4 inches wide to fit around a RPV Page 24 of 43


Cause & Effects Analysis - Design Changes to Dryer Installation Hardware (CF1a) 1. What were the changes? Dryer Guide Device Clearance:  The previous dryer had two guide channels that ran the outside length of the dryer. Once the ch annel was engaged onto the RPV dryer guide rods, little movement occurred as the dryer was installed into the RPV. Similarly, these full-length channels allowed for less movement when the dryer was removed, when compared to the new dryer design that uses dr yer guide slots at the top and bottom of the Dryer Skirt. On the replacement steam dryer there are only 4 points of contact between the dryer and guide rods
lug that is 3 inches wide. This allowed a one-inch margin (one half inch on each side) to install the dryer onto the RPV lugs.
:  - two at 0 and 180 on the base ring, and:  -two at 0 and 180 on the mid-support ring. When the mid-support ring is not engaged w ith the dryer guide rods (i.e, the support ring is higher than the top of the upper dryer guide rod brackets), there are only 2 points of contact between the dryer and guide rods, at 0 and 180 on the base plate. Stated another way, only when the dryer base plate is 2" or more below the bottom of the RPV dryer support br acket (vessel lugs) will there be 4 points of contact.
Thus, there are only 2 points of contact be tween the dryer and guide rods any time the dryer base plate is at the same elevation as the RPV dryer support brackets (vessel lugs). The dryer is therefore much less constrained in terms of the dryer/guide rod interface in the replacement design than it was in the orig inal design, especially when the dryer base plate is at the same elevation as the RP V dryer support brackets (vessel lugs).
Skirt Base Ring Cutouts for RPV Support Lugs
:  The previous dryer used a channel mechanism to allow the dryer skirt to pass along the 4 RPV lugs. The new dryer design had cutouts at the skirt base ring that were nominally 4 in ches wide to fit around a RPV Page 25 of 43 lug that is 3 inches wide. This allowed a one-inch margin (one half inch on each side) to install the dryer onto the RPV lugs.
: 2. Why were the changes made?
: 2. Why were the changes made?
The new dryer installation project was comp leted to address past experiences with structural damage to the old dryer during operation at Extended Power Uprate (EPU) conditions. The new dryer was an original equipment manufacturer (OEM) replacement of a more structurally robust designed dryer. The reas on the design was changed from full-length channels was to accommodate a change to relocate the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. Since the OD of the dryer had to remain the same diameter so as to be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channe ls on the outside of the skirt. The full-length guide rod channels that were previously an integral part of th e skirt thus could no longer remain integral to the sk irt. It was decided to not incorporate the full-length guide rod channels into the replacement dryer design and instead use the 4 points of contact design so as to minimize the weight increase of the replacement dryer. (As the dryer is made more structurally robust, the weight increases as heavier material is used, and the increased weight had to be maintained within the structural capabilities of the RPV dryer support lugs.)
The new dryer installation project was completed to address past experiences with structural damage to the old dryer during operation at Extended Power Uprate (EPU) conditions. The new dryer was an original equipment manufacturer (OEM) replacement of a more structurally robust designed dryer. The reason the design was changed from full-length channels was to accommodate a change to relocate the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. Since the OD of the dryer had to remain the same diameter so as to be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channels on the outside of the skirt. The full-length guide rod channels that were previously an integral part of the skirt thus could no longer remain integral to the skirt. It was decided to not incorporate the full-length guide rod channels into the replacement dryer design and instead use the 4 points of contact design so as to minimize the weight increase of the replacement dryer. (As the dryer is made more structurally robust, the weight increases as heavier material is used, and the increased weight had to be maintained within the structural capabilities of the RPV dryer support lugs.)
: 3. Why were the potential adverse consequences to the installation hardware changes missed?   Barrier Analysis: The barriers expected to prevent adverse consequences from this design change included:
: 3. Why were the potential adverse consequences to the installation hardware changes missed?
Barrier Analysis: The barriers expected to prevent adverse consequences from this design change included:
: a. A design product provided by the vendor designer where all potential adverse consequences associated with the change are addressed.
: a. A design product provided by the vendor designer where all potential adverse consequences associated with the change are addressed.
: b. Review and approval of the vendor provided product by Exelon design personnel using the process defined in CC-AA-10, "Configuration Control Process Description" and ot her associated procedures. c. Review of the design product by the end user (in this case Reactor Services) to determine if there any adverse installati on concerns created by the design change.
: b. Review and approval of the vendor provided product by Exelon design personnel using the process defined in CC-AA-10, Configuration Control Process Description and other associated procedures.
In this case the vendor providing the design pr oduct is GE, who was also the Original Equipment Manufacturer (OEM).
: c. Review of the design product by the end user (in this case Reactor Services) to determine if there any adverse installation concerns created by the design change.
Interviews with a GE design person indicated the use of slots versus channels was considered an acceptable option based on trouble free application of this design in the dryers of more recent vintages of GE BWR's. The GE designer believes that the use of slots in the new dryer was, and is acceptable, but in the case the QC2 dryer, was further degraded by the "ovality" fabrication issue.
In this case the vendor providing the design product is GE, who was also the Original Equipment Manufacturer (OEM). Interviews with a GE design person indicated the use of slots versus channels was considered an acceptable option based on trouble free application of this design in the dryers of more recent vintages of GE BWRs. The GE designer believes that the use of slots in the new dryer was, and is acceptable, but in the case the QC2 dryer, was further degraded by the ovality fabrication issue.
Site design personnel review efforts were focused on structural factors, the instrumentation unique to this particular dryer, and similar technical items. The design engineers have little "hands on" experi ence with dryer inst allation. The Exelon Engineering Change (EC) review process acco unts for this gap in hands on experience by using cross discipline reviews from personnel who do have this experience. In this design change, the end user, Reactor Serv ices completed Att.
Site design personnel review efforts were focused on structural factors, the instrumentation unique to this particular dryer, and similar technical items. The design engineers have little hands on experience with dryer installation. The Exelon Engineering Change (EC) review process accounts for this gap in hands on experience by using cross discipline reviews from personnel who do have this experience. In this design change, the end user, Reactor Services completed Att. 10F of CC-AA-102, Page 25 of 43
10F of CC-AA-102, Page 26 of 43 "Configuration Change Review Checklist for Use by Other Departments" indicating they understood and accepted the impact of this change on their department. Follow-up interviews with GE and Exelon Reactor Servic es personnel indicated that the change in installation hardware, and re sulting closer installation tolerances, was a well-known issue. These personnel believed the change could be accommodated with additional care during installation. One example of this a dditional care was that during the initial installation, personnel were in the reactor refueling cavity bu lkhead to closely watch the lowering load. This option was known to not be available in future Dryer installations since they are performed unde r water after the dryer has been exposed to operating conditions that elevate the radi ological dose rates. The intent was to determine if the dryer could be successfully installed despite these tighter tolerances, and pursue modifications if needed for future installations. This evaluation concluded that for these cha nges to the dryer instal lation hardware:   OEM (GE) personnel had provided the design for use in the Exelon EC process. The design change process had been fo llowed as specified in the governing procedures. Appropriate "end user" personnel (in this case Reactor Services) had been included in the design change review. These Reactor Services personnel had significant experience. Despite these factors, unanticipated negative consequences occurred, that were associated with these design changes.
 
Configuration Change Review Checklist for Use by Other Departments indicating they understood and accepted the impact of this change on their department. Follow-up interviews with GE and Exelon Reactor Services personnel indicated that the change in installation hardware, and resulting closer installation tolerances, was a well-known issue. These personnel believed the change could be accommodated with additional care during installation. One example of this additional care was that during the initial installation, personnel were in the reactor refueling cavity bulkhead to closely watch the lowering load. This option was known to not be available in future Dryer installations since they are performed under water after the dryer has been exposed to operating conditions that elevate the radiological dose rates. The intent was to determine if the dryer could be successfully installed despite these tighter tolerances, and pursue modifications if needed for future installations.
This evaluation concluded that for these changes to the dryer installation hardware:
* OEM (GE) personnel had provided the design for use in the Exelon EC process.
* The design change process had been followed as specified in the governing procedures.
* Appropriate end user personnel (in this case Reactor Services) had been included in the design change review.
* These Reactor Services personnel had significant experience.
Despite these factors, unanticipated negative consequences occurred, that were associated with these design changes.
This evaluation pursued the organizational and programmatic factors that had influenced these negative results. At this point in this RCA, it was known that causal factors associated with this event shared some similarities with those of another recently approved RCA, an investigation of Electromatic Relief Valve Solenoid Failures (Ref.
This evaluation pursued the organizational and programmatic factors that had influenced these negative results. At this point in this RCA, it was known that causal factors associated with this event shared some similarities with those of another recently approved RCA, an investigation of Electromatic Relief Valve Solenoid Failures (Ref.
38). A review of the corrective actions associated with the ERV RCA identified that several of these actions would be well positioned to address the weaknesses identified in this RCA. Additionally, a second RCA "QC2 Replacement Steam Dryer Impact on Fuel Analysis Results" (Ref. 37) was reviewed. This RCA was completed in May 2005 when it was determined that the replacement dryers would not meet the design requirement for differential pressure (dP). This RCA contained corrective actions intended to reduce the probability of negative consequences associated with major design changes and projects. Corrective actions will be needed to prevent recurrence of the dryer lifting event specific to the RCA (since dryer removal will occur each future refuel ing cycle). Actions will also be needed to address the organizational and programmatic issues that allowed the negative design change consequences to occur. The subsequent section, "IX. Corrective Actions to Prevent Recurrence", and "X. Corrective Actions", presents corrective actions associated with the lifting event. Section "XII. Programmatic/ Organizational Issues" details the corrective actions to address the more global concern related to preventing unanticipated negative outcomes of design changes.  
38). A review of the corrective actions associated with the ERV RCA identified that several of these actions would be well positioned to address the weaknesses identified in this RCA.
Additionally, a second RCA QC2 Replacement Steam Dryer Impact on Fuel Analysis Results (Ref. 37) was reviewed. This RCA was completed in May 2005 when it was determined that the replacement dryers would not meet the design requirement for differential pressure (dP). This RCA contained corrective actions intended to reduce the probability of negative consequences associated with major design changes and projects.
Corrective actions will be needed to prevent recurrence of the dryer lifting event specific to the RCA (since dryer removal will occur each future refueling cycle). Actions will also be needed to address the organizational and programmatic issues that allowed the negative design change consequences to occur. The subsequent section, IX. Corrective Actions to Prevent Recurrence, and X. Corrective Actions, presents corrective actions associated with the lifting event. Section XII. Programmatic/ Organizational Issues details the corrective actions to address the more global concern related to preventing unanticipated negative outcomes of design changes.
Page 26 of 43


Page 27 of 43 CF1b: Cause & Effects Analysis - Fabrication Induced Ovality The additional movement and reduced toleran ces allowed by new installation hardware in the QC U-2 dryer was further degraded by a fabrication problem which resulted in the skirt being approximately 2 inches out of r ound ("ovality issue"). Th e orientation of the out of round position further allowed additional movement between the dryer guide slots and the RPV guide rods. The concern related to the ovality impacting installation clearances was recognized. The DDR (Ref.
CF1b: Cause & Effects Analysis - Fabrication Induced Ovality The additional movement and reduced tolerances allowed by new installation hardware in the QC U-2 dryer was further degraded by a fabrication problem which resulted in the skirt being approximately 2 inches out of round (ovality issue). The orientation of the out of round position further allowed additional movement between the dryer guide slots and the RPV guide rods. The concern related to the ovality impacting installation clearances was recognized. The DDR (Ref. 7) resolving the ovality issue noted -
: 7) resolving the ovality issue noted - "Dimensional analysis of the as-built hardware indicates that the dryer will fit in the vessel. Clearances normally available have been compromised, so additional guidance constraints will be placed in the lower guide block, to limit misalignment and assist in installation." The additional guidance constraints were in fact installed as documented in Ref. 9. These constraints helped reduce potential movement between the dryer and the vessel wall, but did not have any impact on lateral movement. It is believed that this lateral movement contributed to the "lift even t" by allowing the drye r to rotate about one inch due to the slop between the dryer guide slots rods and the RP V dryer guide rods. This minimal rotation contributed to the drye r skirt base cutouts for the RPV lugs, being out of alignment with the RPV lugs, which allowed for the skirt base plate to impact on the bottom of the reactor lugs as the dryer was being lifted out of the reactor vessel. Note: Att. 7 contains more detailed descriptions and pictures regarding the movement of and damage to the U-2 Dryer during the Lifting Event.
Dimensional analysis of the as-built hardware indicates that the dryer will fit in the vessel. Clearances normally available have been compromised, so additional guidance constraints will be placed in the lower guide block, to limit misalignment and assist in installation. The additional guidance constraints were in fact installed as documented in Ref. 9. These constraints helped reduce potential movement between the dryer and the vessel wall, but did not have any impact on lateral movement. It is believed that this lateral movement contributed to the lift event by allowing the dryer to rotate about one inch due to the slop between the dryer guide slots rods and the RPV dryer guide rods.
CF2: Disposition of Lifting Event Prior to Start-up from Q2P03 Given that this RCA concludes that damage from the May 2005 (Q2P03) lifting event was a primary causal factor for the cracking identified during Q2R18 inspections, and the damage from this event was a known issue, it is logical to conclude that this disposition was a "missed opportunity" to prevent the dryer skirt cracking. This section describes the evaluation performed for potential causal factors associated with the reviews completed after the lifting event that occurred. The table below describes the major reviews and milestones that occurred, dur ing and shortly after Q2P03.
This minimal rotation contributed to the dryer skirt base cutouts for the RPV lugs, being out of alignment with the RPV lugs, which allowed for the skirt base plate to impact on the bottom of the reactor lugs as the dryer was being lifted out of the reactor vessel.
Q2P03 Lift Event Follow-up Decision Timeline Date Time Event 5/11/05 2300 (approx.)
Note: Att. 7 contains more detailed descriptions and pictures regarding the movement of and damage to the U-2 Dryer during the Lifting Event.
Lift event occurred 05/12/05 0156 OCC notified 05/12/05 0700 Prompt Investigation Initiated (Ref. 4) 05/12/05 NA Exelon comment matrix for review of FDDR RMCN 06243 notes need to assess:
CF2: Disposition of Lifting Event Prior to Start-up from Q2P03 Given that this RCA concludes that damage from the May 2005 (Q2P03) lifting event was a primary causal factor for the cracking identified during Q2R18 inspections, and the damage from this event was a known issue, it is logical to conclude that this disposition was a missed opportunity to prevent the dryer skirt cracking. This section describes the evaluation performed for potential causal factors associated with the reviews completed after the lifting event that occurred. The table below describes the major reviews and milestones that occurred, during and shortly after Q2P03.
: 1. "cold work and/or residual stress in the weld." 2. "magnitude of the plastic strain to determine the Page 28 of 43 potential susceptibility."
Q2P03 Lift Event Follow-up Decision Timeline Date           Time         Event 5/11/05       2300         Lift event occurred (approx.)
05/13/05 ~0700 (prior to install) Liquid Penetrant testing performed on selected damaged and/or repaired areas of Dryer (Ref. 1) 05/13/05  0710 Dryer Repaired, Modified and set into the RPV 05/13/05 0900 (assumed) Prompt Approved by MRC. 05/13/05 NA FDDR RMCN06245 Issued by GE to Resolve Lift Event Damage. Implemented under Exelon WO
05/12/05       0156         OCC notified 05/12/05       0700         Prompt Investigation Initiated (Ref. 4) 05/12/05       NA           Exelon comment matrix for review of FDDR RMCN 06243 notes need to assess:
: 1. cold work and/or residual stress in the weld.
: 2. magnitude of the plastic strain to determine the Page 27 of 43


742798-1 (Ref. 8) 05/14/05 NA PORC approval of EC 351168- Rev.2- incorporating FDDR RMCN 06243 into the Exelon EC process. 05/16/05 0345 U-2 Start-Up from Q2P03 05/24/05 NA Exelon Corporation concurrence letter for FDDR RMCN 06243 issued. (Ref. 30) 05/25/05 NA ACE on Lifting Event Approved by MRC (Ref. 2)
potential susceptibility.
05/13/05      ~0700          Liquid Penetrant testing performed on selected (prior to      damaged and/or repaired areas of Dryer install)      (Ref. 1) 05/13/05      0710          Dryer Repaired, Modified and set into the RPV 05/13/05      0900          Prompt Approved by MRC.
(assumed) 05/13/05      NA            FDDR RMCN06245 Issued by GE to Resolve Lift Event Damage. Implemented under Exelon WO 742798-1 (Ref. 8) 05/14/05     NA             PORC approval of EC 351168- Rev.2- incorporating FDDR RMCN 06243 into the Exelon EC process.
05/16/05     0345           U-2 Start-Up from Q2P03 05/24/05     NA             Exelon Corporation concurrence letter for FDDR RMCN 06243 issued. (Ref. 30) 05/25/05     NA             ACE on Lifting Event Approved by MRC (Ref. 2)
This RCA reached the following conclusions regarding the Q2P03 assessments of the lifting event:
This RCA reached the following conclusions regarding the Q2P03 assessments of the lifting event:
: 1. There was no evidence of any formal review (HU-AA-1212, or similar process) to specify what areas of the Dryer areas were to be inspected after the lift event. Non-destructive examination (NDE) personnel performed liquid penetrant examinations of damaged and or repaired ar eas at the direction of GE refuel floor supervision. (Ref. 1) These examinations included outside diameter areas, no inner diameter areas were inspected. 2. Only anecdotal evidence of evaluation of cold work or elastic strain impacts could be found. Personnel who were involved in the review of the GE FDDR (Ref. 8) recalled discussions of these topics, and conclusions that the ductile nature of stainless steel, and low stresses in the skirt/baseplate regions, made future problems unlikely. This RCA found no documented, formally reviewed structural analysis reports or evaluations comp leted prior to restart from Q2P03.
: 1. There was no evidence of any formal review (HU-AA-1212, or similar process) to specify what areas of the Dryer areas were to be inspected after the lift event.
Formal structural analyses (Ref. 29&36), and metallurgical evaluations (Ref. 19), were completed as part of this RCA. Because these analyses could not identify the exact initiation mechanism of cracking, a detailed analysis during Q2P03 is unlikely to have changed the outcome, (formal analysis would have concluded the uni t could be restarted without major replacement of dryer skirt components). For this reason, the weaknesses associated with the Q2P03 lifting event disposition are not considered a root cause to this event. The weaknesses are retained as a contributing cause because more detailed Page 29 of 43 inspections could have detected cracks in the skirt or base plate, specifically on the inner diameter areas. In addition, more detailed inspections in the inner diameter regions would have better identified the magnitude of the deformation, which may have resulted in a different conclusion of corrective actions needed.
Non-destructive examination (NDE) personnel performed liquid penetrant examinations of damaged and or repaired areas at the direction of GE refuel floor supervision. (Ref. 1) These examinations included outside diameter areas, no inner diameter areas were inspected.
Event 2: Crack found in vane bank of "E" bank near 320 azimuth The basis for the determination of minimal weld thickness, proximity to a weld-stop (stress riser) is photographic observation by the Quad Cities root cause team. Reference 17, Figure 1, last image, shows that the weld buildup is smaller than adjacent portions of the weld and also shows the weld-stop. Additionally, hood assembly and weld residual stresses may have been produced due to the alignment of 6 vane panels in the "E" hood and the weld shrinkage when welding the hood panels and gussets to the vane panel end plates and trough. (This results from differential thermal e xpansion and contraction that occur from the temperature difference between the weld bead and the cooler base metal.)
: 2. Only anecdotal evidence of evaluation of cold work or elastic strain impacts could be found. Personnel who were involved in the review of the GE FDDR (Ref. 8) recalled discussions of these topics, and conclusions that the ductile nature of stainless steel, and low stresses in the skirt/baseplate regions, made future problems unlikely. This RCA found no documented, formally reviewed structural analysis reports or evaluations completed prior to restart from Q2P03.
Formal structural analyses (Ref. 29&36), and metallurgical evaluations (Ref. 19), were completed as part of this RCA. Because these analyses could not identify the exact initiation mechanism of cracking, a detailed analysis during Q2P03 is unlikely to have changed the outcome, (formal analysis would have concluded the unit could be restarted without major replacement of dryer skirt components). For this reason, the weaknesses associated with the Q2P03 lifting event disposition are not considered a root cause to this event. The weaknesses are retained as a contributing cause because more detailed Page 28 of 43
 
inspections could have detected cracks in the skirt or base plate, specifically on the inner diameter areas. In addition, more detailed inspections in the inner diameter regions would have better identified the magnitude of the deformation, which may have resulted in a different conclusion of corrective actions needed.
Event 2: Crack found in vane bank of E bank near 320° azimuth The basis for the determination of minimal weld thickness, proximity to a weld-stop (stress riser) is photographic observation by the Quad Cities root cause team. Reference 17, Figure 1, last image, shows that the weld buildup is smaller than adjacent portions of the weld and also shows the weld-stop. Additionally, hood assembly and weld residual stresses may have been produced due to the alignment of 6 vane panels in the E hood and the weld shrinkage when welding the hood panels and gussets to the vane panel end plates and trough. (This results from differential thermal expansion and contraction that occur from the temperature difference between the weld bead and the cooler base metal.)
These factors are postulated to, in the presence of operating vibration loads, have initiated the crack.
These factors are postulated to, in the presence of operating vibration loads, have initiated the crack.
Event 3: Latch Box Crack at 220 azimuth The basis for the cause determination is Reference 18, which notes "that the crack appeared to have initiated at the corner where one latch box to skirt panel weld either began or ended. Also, the weld end appears to have a discontinuity in the form of a small crater. It is well known that the beginning or end of a weld bead could have some discontinuities that could serve as a fatigue crack initiation site. The other contributing factor could be the corner location where the two welds are mee ting that could produce high fit up stress at that location. The presence of high weld residual stress could lower the fatigue stress threshold and may result in th e initiation of a fatigue crack. Therefore, it is concluded that the most likely cause of the cracking is the presence of weld end discontinuity and likely high weld re sidual stress at corner location."
Event 3: Latch Box Crack at 220° azimuth The basis for the cause determination is Reference 18, which notes that the crack appeared to have initiated at the corner where one latch box to skirt panel weld either began or ended. Also, the weld end appears to have a discontinuity in the form of a small crater. It is well known that the beginning or end of a weld bead could have some discontinuities that could serve as a fatigue crack initiation site. The other contributing factor could be the corner location where the two welds are meeting that could produce high fit up stress at that location. The presence of high weld residual stress could lower the fatigue stress threshold and may result in the initiation of a fatigue crack. Therefore, it is concluded that the most likely cause of the cracking is the presence of weld end discontinuity and likely high weld residual stress at corner location.
Page 29 of 43


Page 30 of 43 C. Discussion of Evaluation of "Other Conditions" Conditions in the table below were determined to not be CF's for this event, but warrant additional discussion for clarity purposes, and to ensure priority issues are resolved even if they did not contribute to these events. The table summarizes these events. For some of the more complex issues, a more detailed discussion appears at th e end of the table.
C. Discussion of Evaluation of Other Conditions Conditions in the table below were determined to not be CFs for this event, but warrant additional discussion for clarity purposes, and to ensure priority issues are resolved even if they did not contribute to these events. The table summarizes these events. For some of the more complex issues, a more detailed discussion appears at the end of the table.
Condition Description Issues, Basis, Resolution C.1: Crane load cell unavailable. Effect of not having load cell display available was not effectively resolved prior to the lifting evolution. RCA inconclusive if load cell could have prevented event but there are clear oppor tunities to enhance the use of this barrier in future. CA's specified in "Other" Section (More detailed discussion appears at the end of this table.) C.2: Finite Element Model Did Not Include Detail For New Dryer Design Below Water Line RCA determined extensive issues in configuration control between the as built replacement dryers and the GE analysis model (one example - base plate cut-outs were not included in analysis model). Structural analysis associated with the RCA determined that this lack of configuration control did not contribute significantly to this event (Ref. 29) (More detailed discussion appears at the end of this table.)
Condition Description               Issues, Basis, Resolution C.1: Crane load cell unavailable.
C.3: Metal Stress Inducing Factors - Design: Used super element model for new dryer  
* Effect of not having load cell display available was not effectively resolved prior to the lifting evolution.
* RCA inconclusive if load cell could have prevented event but there are clear opportunities to enhance the use of this barrier in future.
* CAs specified in Other Section (More detailed discussion appears at the end of this table.)
C.2: Finite Element Model Did
* RCA determined extensive issues in configuration Not Include Detail For New              control between the as built replacement dryers and Dryer Design Below Water Line            the GE analysis model (one example - base plate cut-outs were not included in analysis model).
* Structural analysis associated with the RCA determined that this lack of configuration control did not contribute significantly to this event (Ref. 29)
(More detailed discussion appears at the end of this table.)
C.3: Metal Stress Inducing
* Base plate and skirt gusset load concentration not Factors - Design: Used super             modeled.
element model for new dryer
* Model assumed full penetration welds for the base design.                                  plate to skirt, while the design and fabrication installed partial penetration welds.
* Analysis model did not include cutouts in the skirt base plate.
* Structural analysis associated with the RCA determined that this lack of detailed analysis did not contribute significantly to this event (Ref. 29)
C.4. Metal Stress Inducing
* Stress induced in the dryer skirt & skirt base plate due Factors - Fabrication: Distortion/      to two halves of dryer being force fit together, ovality of dryer base plate              resulting in ovality of the skirt and skirt base plate.
* Stress contribution to skirt cracking would be limited to elastic distortion of the base ring.
* Impact of residual stresses was not specifically Page 30 of 43


design. Base plate and skirt gusset load concentration not modeled. Model assumed full penetration welds for the base plate to skirt, while the de sign and fabrication installed partial penetration welds. Analysis model did not include cutouts in the skirt base plate. Structural analysis associated with the RCA determined that this lack of detailed analysis did not contribute significantly to this event (Ref. 29) C.4. Metal Stress Inducing Factors - Fabrication: Distortion/
Condition Description             Issues, Basis, Resolution analyzed in Q2P03 because skirt is a low stress region.
ovality of dryer base plate Stress induced in the dryer sk irt & skirt base plate due to two halves of dryer being force fit together, resulting in ovality of the skirt and skirt base plate. Stress contribution to skirt cracking would be limited to elastic distortion of the base ring. Impact of residual stresses was not specifically Page 31 of 43 Condition Description Issues, Basis, Resolution analyzed in Q2P03 because skirt is a low stress region. A follow-up evaluation associated with this RCA (Ref. 33) was completed and concluded that the small plastic strain and residual st resses directly attributable to the ovality issue did not contribute to the observed  
* A follow-up evaluation associated with this RCA (Ref. 33) was completed and concluded that the small plastic strain and residual stresses directly attributable to the ovality issue did not contribute to the observed cracking.
 
(More detailed discussion appears at the end of this table.)
cracking. (More detailed discussion appears at the end of this table.)
C.5: Structural - Fabrication:
C.5: Structural - Fabrication:
Welding of base plate to dryer
* Dryer material sample showed a lack of weld Welding of base plate to dryer        penetration at skirt and base plate connection skirt showed lack of penetration.
 
* Metallugical Analysis completed for this RCA concluded that the lack of penetration was not completely unexpected for this type of weld. This analysis also concluded that this issue was not a causal factor for the observed cracking.
skirt showed lack of penetration. Dryer material sample showed a lack of weld penetration at skirt a nd base plate connection Metallugical Analysis completed for this RCA concluded that the lack of penetration was not completely unexpected for this type of weld. This  
* More detailed discussion and excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous Analysis section of this report and are not repeated here.
 
analysis also concluded that this issue was not a causal factor for the observed cracking. More detailed discussion a nd excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous "Analysis" section of this report and are not repeated here.
C.6: Structural - Fabrication:
C.6: Structural - Fabrication:
Use of halide containing weld
* Dryer material samples from both the 140° and 220° Use of halide containing weld        regions indicated a presence of TGSCC.
 
wire coupled with cracking
wire coupled with cracking allowed SCC initiation. Dryer material samples from both the 140 and 220 regions indicated a presence of TGSCC. Metallurgical Analysis completed for this RCA concluded that the TGSCC wa s not an initiating factor for the observed fatigue cracking. TGSCC in the 140 region was more extensive than the 220 region. It is believed this condition was caused by the water introduced to the area after the fatigue cracking occurred in the 140 area. More detailed discussion a nd excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous "Analysis" section of this report and are not repeated here.
* Metallurgical Analysis completed for this RCA allowed SCC initiation.              concluded that the TGSCC was not an initiating factor for the observed fatigue cracking. TGSCC in the 140° region was more extensive than the 220° region. It is believed this condition was caused by the water introduced to the area after the fatigue cracking occurred in the 140° area.
 
* More detailed discussion and excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous Analysis section of this report and are not repeated here.
Page 32 of 43 C.1: Crane Load Cell Display Unavailable Allowing Excess Forces On Dryer The Reactor Building Overhead Crane (RBOC) is provided with a load cell that will sense the weight on the crane hook with an output signal to a crane power interlock switch. The set point of this switch is 250,000 lbs (125 ton), equal to the rated crane capacity. The load cell signal also provides input to a digi tal readout, which if properly calibrated, will provide the accurate weight of a lifted load. There is a primary readout on the control unit located on the crane trolley, which cannot be viewed remotely. There is, however, a secondary display that can be viewed from the crane operator's cab as well as the refueling floor. During the review of the Steam Dryer lift event on May 12, 2005 (Q2P03) it was determined that this lift was performed w ith a non-functioning digital readout display from the load cell (secondary display).  (Note:  The 125-ton cran e power interlock was functional, only the display function was inoperable). Procedure QCMM 5800-05 "Reactor Building Overhead Crane Utilization", Step 3.3.1 states:
Page 31 of 43
"if the - readout does not display any digits, WRITE a Work Request for repair.
This does not render it inoperable if all view angles around th e lift can be verified to ensure no interferences are encountered."
 
There is no evidence that a Work Request (WR) or an Issue Report (IR) was initiated at this time, however, a prior request was initiated on 4/21/05 (AR# 327007). This request (WR# 176082) was closed to WO# 805641-02 for calibration of the lo ad cell and repair of the digital readout, which was completed on 5/16/05, approximately 4 days after the dryer lift event.
Per discussion with the contracted crane maintenance vendo r, it is understood that the digital readout will provide accurate indication of a slight change in load ( 200 lbs) on the crane hook, which would be in dicative of a load hang-up.
It is also understood that monitoring of the load could easily be accomplished by using a dedicated person to watch the display for any increase in load indication. This person would be located near the signalman, thereby being within sight of the crane operator without di stracting either the signalman or the crane operator from their re spective load handling responsibilities. The person monitoring the load display can terminate the lift at any time a change in load is observed.
Based on the speed of the hoist in slow speed (< 2ft/min.)
and reasonable reaction times by the load monitor and the operator, it is expected that the li ft could be suspended with a minimal amount of load on the contac t points due to hang-up of the load.
The ACE conducted at the time of the event (Ref. 2) concluded that since the rigging is a "metal to metal" contact throughout, any load cell deviations would be instantaneous and would not allow for operator action to prev ent possible consequences -"  This RCA, however concludes that had the load cell sec ondary readout been functioning and a dedicated person assigned to monitor and halt operation of the cran e at a predefined criteria the damage could have been minimized. The finite element analysis conducted to estimate the force necessary to permanently deform the skirt base ring 3/4 of an inch would be around 47,000 lbs.
Since the load cell can sense load differences as small as 200 lbs
., and the the skirt base plate would deflect Page 33 of 43 in an elastic manner at some lesser force befo re it would plastically deform to the 3/4 inch deflection, the lift could have been stopped prior to any permanent deflection. During interviews, it was evident that the lack of a functioning load cell display had become an expected norm and the procedure had been written to allow the use of the RBOC without the load cell functi onal. It is also reasonable to conclude that with the heightened sensitivity to the dryer cleara nces due to the changes in design and to fabrication problems (ovality), that more emphasis should have been placed on the operation of the load cell. 
 
C.2 Finite Element Model Did Not Include Adequate Detail For New Dryer Design A potential failure mode that was identified and subsequently rejected, was that the finite element model for the dryer could be inadequate for the new dryer design. If this allowed an inadequate margin condition to exist without the model showing the problem, then a design inadequacy would go undetected. The evidence indicates that the cracks occurred primarily because of residual stresses associated with the dryer lift / impact event. Normally, the dryer modeling would not be used to ensure margin to mis-handling events, except possibly in very low dimensional clearance margin conditions such as th is (where a user error is likely).
During RCA, several vulnerabilities were di scovered, which the dryer model was not detailed enough to detect. One example is th at the gussets placed adjacent to the notches in the base plate, could cause ring deflection(s) to be transferred to the skirt panels, allowing a cyclic loading. A second example wa s that the cutouts for the RPV lugs were not modeled. This prevented the opportunity to detect local stress conditions that may be present in the skirt or base ring in the vicinity of the cutout. Since the model did not detail these conditions, additional detailed finite element modeling was needed to better evaluate this po ssible cause. Additional detailed finite element analysis (FEA) completed in a GE report titled "Quad Cities Unit 2 Replacement Steam Dryer Analysis, Detailed Stress Analysis of Skirt Base


Plate Cutouts and Gussets." (Ref. 29) concluded that:
C.1: Crane Load Cell Display Unavailable Allowing Excess Forces On Dryer The Reactor Building Overhead Crane (RBOC) is provided with a load cell that will sense the weight on the crane hook with an output signal to a crane power interlock switch. The set point of this switch is 250,000 lbs (125 ton), equal to the rated crane capacity. The load cell signal also provides input to a digital readout, which if properly calibrated, will provide the accurate weight of a lifted load. There is a primary readout on the control unit located on the crane trolley, which cannot be viewed remotely. There is, however, a secondary display that can be viewed from the crane operators cab as well as the refueling floor.
During the review of the Steam Dryer lift event on May 12, 2005 (Q2P03) it was determined that this lift was performed with a non-functioning digital readout display from the load cell (secondary display). (Note: The 125-ton crane power interlock was functional, only the display function was inoperable). Procedure QCMM 5800-05 Reactor Building Overhead Crane Utilization, Step 3.3.1 states:
if the  readout does not display any digits, WRITE a Work Request for repair.
This does not render it inoperable if all view angles around the lift can be verified to ensure no interferences are encountered.
There is no evidence that a Work Request (WR) or an Issue Report (IR) was initiated at this time, however, a prior request was initiated on 4/21/05 (AR# 327007). This request (WR# 176082) was closed to WO# 805641-02 for calibration of the load cell and repair of the digital readout, which was completed on 5/16/05, approximately 4 days after the dryer lift event.
Per discussion with the contracted crane maintenance vendor, it is understood that the digital readout will provide accurate indication of a slight change in load ( 200 lbs) on the crane hook, which would be indicative of a load hang-up. It is also understood that monitoring of the load could easily be accomplished by using a dedicated person to watch the display for any increase in load indication. This person would be located near the signalman, thereby being within sight of the crane operator without distracting either the signalman or the crane operator from their respective load handling responsibilities. The person monitoring the load display can terminate the lift at any time a change in load is observed.
Based on the speed of the hoist in slow speed (< 2ft/min.) and reasonable reaction times by the load monitor and the operator, it is expected that the lift could be suspended with a minimal amount of load on the contact points due to hang-up of the load.
The ACE conducted at the time of the event (Ref. 2) concluded that since the rigging is a metal to metal contact throughout, any load cell deviations would be instantaneous and would not allow for operator action to prevent possible consequences  This RCA, however concludes that had the load cell secondary readout been functioning and a dedicated person assigned to monitor and halt operation of the crane at a predefined criteria the damage could have been minimized.
The finite element analysis conducted to estimate the force necessary to permanently deform the skirt base ring 3/4 of an inch would be around 47,000 lbs. Since the load cell can sense load differences as small as 200 lbs., and the the skirt base plate would deflect Page 32 of 43


"The analysis results show that the eff ect of the cutout on the skirt response is insignificant and the original stress analysis without this detail is adequate. In  
in an elastic manner at some lesser force before it would plastically deform to the 3/4 inch deflection, the lift could have been stopped prior to any permanent deflection.
 
During interviews, it was evident that the lack of a functioning load cell display had become an expected norm and the procedure had been written to allow the use of the RBOC without the load cell functional. It is also reasonable to conclude that with the heightened sensitivity to the dryer clearances due to the changes in design and to fabrication problems (ovality), that more emphasis should have been placed on the operation of the load cell.
addition, the fatigue stress levels at the cutout in the base ring for all configurations (original, as found, and repair design) are very low compared with the endurance limit of 13.6 ksi -" "The inelastic analysis results show that the lug/base plate impact resulted in significant levels of irreversible plastic deformation that could have contributed to crack initiation due to a combination of residual stress inherent in plastically deformed structures and flow-induced vibratory stresses."
C.2 Finite Element Model Did Not Include Adequate Detail For New Dryer Design A potential failure mode that was identified and subsequently rejected, was that the finite element model for the dryer could be inadequate for the new dryer design. If this allowed an inadequate margin condition to exist without the model showing the problem, then a design inadequacy would go undetected.
The evidence indicates that the cracks occurred primarily because of residual stresses associated with the dryer lift / impact event. Normally, the dryer modeling would not be used to ensure margin to mis-handling events, except possibly in very low dimensional clearance margin conditions such as this (where a user error is likely).
During RCA, several vulnerabilities were discovered, which the dryer model was not detailed enough to detect. One example is that the gussets placed adjacent to the notches in the base plate, could cause ring deflection(s) to be transferred to the skirt panels, allowing a cyclic loading. A second example was that the cutouts for the RPV lugs were not modeled. This prevented the opportunity to detect local stress conditions that may be present in the skirt or base ring in the vicinity of the cutout. Since the model did not detail these conditions, additional detailed finite element modeling was needed to better evaluate this possible cause.
Additional detailed finite element analysis (FEA) completed in a GE report titled Quad Cities Unit 2 Replacement Steam Dryer Analysis, Detailed Stress Analysis of Skirt Base Plate Cutouts and Gussets. (Ref. 29) concluded that:
The analysis results show that the effect of the cutout on the skirt response is insignificant and the original stress analysis without this detail is adequate. In addition, the fatigue stress levels at the cutout in the base ring for all configurations (original, as found, and repair design) are very low compared with the endurance limit of 13.6 ksi The inelastic analysis results show that the lug/base plate impact resulted in significant levels of irreversible plastic deformation that could have contributed to crack initiation due to a combination of residual stress inherent in plastically deformed structures and flow-induced vibratory stresses.
The conclusions of this analysis supports elimination of lack of detail in the FEA as a potential cause, and supports the RCA position that stresses from the lifting event were causal factors in Event 1.
The conclusions of this analysis supports elimination of lack of detail in the FEA as a potential cause, and supports the RCA position that stresses from the lifting event were causal factors in Event 1.
Page 34 of 43 C.4. Metal Stress Inducing Factors - Distorti on/ovality of dryer ba se plate (Ref 33) GE completed additional analysis of this c ondition in support of this RCA. Excerpts of this analysis appear below, which support a position that stresses from ring ovality did not contribute to the events in this RCA:
Page 33 of 43


Given the sequence of events, it is reasona ble to conclude, as stated in the DDR disposition, that the distortion of the base ring was a consequence of welding the additional supports into the upper steam dryer structure. Weld shrinkage between the dryer banks could have transmitted a load into the skirt tending to make the structure, including the base ring, slightly oval. However, when considering the potential effects of this distortion relative to the fa ilure observed at the 140&#xba; location, there are two important points. Fi rst, it should be recognized that, at 247 inches diameter and only one inch thick, the base ring is a relatively flexible component. Two inches deviation in a 247 inch diameter is only about 0.8% diametral distortion, which represents neither significant working of the material nor residual stress. In fact, a large fraction of this projected maximum distortion of 0.8% is elastic rather than plastic deformation. Circumferential strain, which would be more indicative of permanent plastic deformation, is essentially a net of zero since the diameter is approximately the same amount undersize 90 degrees from the oversize points. In any ev ent BWRVIP-84* allows up to 2.5% permanent plastic strain for the purpo ses of straightening stainless steel components. The plastic strain attributable to the diametral distortion is much less than this limit.
C.4. Metal Stress Inducing Factors - Distortion/ovality of dryer base plate (Ref 33)
The second consideration is th at the failure occurred at the 140&#xba; azimuth, which is approximately midway between the minimum and maximum diameters. Therefore, the failure occurred near a neutral point where the diametral distortion and stress would be minimal. However, it is recognized that in this region, especially in the cutout in the base ring, the balance be tween the oversize diameter and the undersize diameter would tend to produce some amount of bending of the ring. This produced some incremental amount of torsional load in the cutout region that would be additive to the overall stress applied in the failure location. Nevertheless, it is concluded the small plastic st rain and residual stress directly attributable to the observed diametral deviation had no role in the failure.
GE completed additional analysis of this condition in support of this RCA. Excerpts of this analysis appear below, which support a position that stresses from ring ovality did not contribute to the events in this RCA:
Given the sequence of events, it is reasonable to conclude, as stated in the DDR disposition, that the distortion of the base ring was a consequence of welding the additional supports into the upper steam dryer structure. Weld shrinkage between the dryer banks could have transmitted a load into the skirt tending to make the structure, including the base ring, slightly oval. However, when considering the potential effects of this distortion relative to the failure observed at the 140&#xba; location, there are two important points. First, it should be recognized that, at 247 inches diameter and only one inch thick, the base ring is a relatively flexible component. Two inches deviation in a 247 inch diameter is only about 0.8%
diametral distortion, which represents neither significant working of the material nor residual stress. In fact, a large fraction of this projected maximum distortion of 0.8% is elastic rather than plastic deformation. Circumferential strain, which would be more indicative of permanent plastic deformation, is essentially a net of zero since the diameter is approximately the same amount undersize 90 degrees from the oversize points. In any event BWRVIP-84* allows up to 2.5%
permanent plastic strain for the purposes of straightening stainless steel components. The plastic strain attributable to the diametral distortion is much less than this limit.
The second consideration is that the failure occurred at the 140&#xba; azimuth, which is approximately midway between the minimum and maximum diameters.
Therefore, the failure occurred near a neutral point where the diametral distortion and stress would be minimal. However, it is recognized that in this region, especially in the cutout in the base ring, the balance between the oversize diameter and the undersize diameter would tend to produce some amount of bending of the ring. This produced some incremental amount of torsional load in the cutout region that would be additive to the overall stress applied in the failure location. Nevertheless, it is concluded the small plastic strain and residual stress directly attributable to the observed diametral deviation had no role in the failure.
Page 34 of 43


Page 35 of 43 VI. Extent of Condition:
VI. Extent of Condition:
Cause being addressed Extent of Condition Review CF1a - Guide Channels Not Used in New Dryer  
Cause being addressed                           Extent of Condition Review CF1a - Guide Channels     The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam Not Used in New Dryer     dryers also do not use channels. The modification to the Quad Cities Design                    Unit 2 (QC2) dryer of wider base ring slots has been incorporated into the design of these three dryers and the attention required during lift to the possibility of hanging up the dryer base ring on the dryer (RPV) support lugs has been communicated to Dresden, and will be communicated to the industry through the OPEX process.
CF1b - Ovality Results in The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam Looser Installation      dryers were/are constructed in two halves, shipped and welded Clearances                together at J. T. Cullen. Measurements showed that the dryer skirt was oval following the welding. The looseness caused by the ovality is postulated to be an element in the dryer removal event. The lessons learned regarding rigging and welding to prevent the dryer from becoming oval have been incorporated in the fabrication of these three dryers.
CF2: Analysis &          The evaluations, examinations and analyses performed immediately Inspections of Damage    after the dryer lift event in Q2P03 did not have sufficient rigor. As from Q2P03 lift event    noted in the Evaluation section, it is likely that these weaknesses, concluded use as is. GE especially in the analysis area, would not have changed the outcome FDDR, and site review    of the event, however there is some finite possibility of a missed concluded:                opportunity to prevent this event from this CF. The Programmatic/
Organizational issues associated with this CF are unlikely to be
* Modify base ring for  repeated in dryer components, given the limited population of similar separator guide rods  dryers, but there are extent of condition concerns related to other RCA
* Run for 1 cycle      reports reviewed as part of this analysis. Several corrective actions
* Repair/modify base    recently initiated in these other RCA are well aligned with this CF, ring for RPV Lugs in  and should be expected to have a positive impact on this concern.
Q2R18                These items will be addressed in more detail in the subsequent Corrective Actions section of this report.
CF3 - Data Collection    Vibrations are present to a degree in all the Units. They are measured From Instrumented Dryer  and used in the analyses or compared to analyzed levels.
Acoustic Loading @ 150    Consequently this should not be an issue for other stations / units.
Hz CF4 - Issue 2: Bank E  Section 1 of Reference 19 reads in part: Following the discovery of End Plate Cracking        cracking <in Gusset 19>, all remaining locations were inspected. All of the other gussets were found to be acceptable with no evidence of cracking. Therefore, it is concluded that this is an isolated incident.
CF5 - Issue 3: Steam      Latch box protectors have been installed under EC 351167, Rev. 1 for Dryer Latch Box Cracking  Unit 1 and EC 348286, Rev. 0 for Unit 2. No other latch boxes were found cracked during these installations.
Page 35 of 43


Design The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam dryers also do not use channels. The modification to the Quad Cities
VII. Risk Assessment:
Plant-specific risk Basis for Determination consequence Industrial Safety -    Although the load cell display was not functioning, the circuitry does not Minimal Risk          allow a lift of over 125 tons nominal. Given the safety factor of 5 required for the crane and other lifting members, the members would have been able to withstand the load up to the crane lift cutout without failing.
Nuclear Safety -      Dryer component cracking could result in lost parts. Various lost parts Minimal Risk          analyses have been performed in the past (most recently for a steam dryer 94 lb. lifting lug for Unit 1 and a steam dryer 9 x 6 plate for Unit 2). The most significant consequence has been determined to be a risk to production. No risks to nuclear safety have been found. Additionally, the Quad Cities Risk Management Expert and the Corporate Model Owner have reviewed the Steam Dryer Gusset Cracking Condition (IR 473034), the Steam Dryer Skirt Cracking Condition (IR 472321) and GE-NE-0000-0052-6385-R0, Lost Parts Analysis for Dryer Lifting Lug and Dryer Skirt Panel Unit 1, to provide support for the PRA modeling. Basically, the risk assessment review found the risk increase associated with these conditions to be minimal and not risk significant, as documented in Reference 26.
Regulatory Impact      There is Regulatory Impact from the standpoint that the Station has assured
- Minimal Risk        the Regulator that a more robust dryer has been installed, that the loading on the dryer is understood, the dryer has been shown analytically to be able to withstand the loading and that there should be no cracking of the dryer.
However, dryer cracking was found during Q2R18, resulting in a decrease in the credibility of the Station with the Regulator. Note that the dryers are non-safety related, seismically designed. Due to the location of the cracking and the measure strain hardening of the dryer material, the cause of the cracking is judged to be the lift event. Inspection of the Unit 1 dryer during Q1M19 determined that this undamaged dryer did not have cracking comparable to the Unit 2 dryer supporting the conclusion that the dryers were designed adequate to withstand the loads (minus a lifting event) as committed to the Regulators.
Production / Cost -    Based on the following, there is minimal likelihood of recurrence of this dryer Minimal Risk          cracking event:
: a. GEs root cause analysis of the dryer 140&deg; skirt cracking, Reference 21, identifies the lift event and consequent material strain hardening as the probable cause,
: b. Dryer analysis using measured vibration loads and confirmed using strain gages shows that the dryer is able to withstand the operating loadings and
: c. The Unit 1 dryer (without a lift event) as-found condition following approximately 10 months of operation, about 1/2 that time at EPU power levels, was acceptable and as expected.
Page 36 of 43


Unit 2 (QC2) dryer of wider base ring slots has been incorporated into the design of these three dryers and the attention required during lift to the possibility of "hanging up" the dryer base ring on the dryer (RPV) support lugs has been communicated to Dresden, and will be communicated to the industry through the OPEX process. CF1b - Ovality Results in Looser Installation  
VIII. Previous Events:
Previous Events                                      Previous Event Review None                          Many OPEX reports were found that identified cracking and most of them identified flow induced vibration or undersized welds as the cause. No case was found of dryer damage due to or during lifting of the dryer.
IX. Corrective Actions to Prevent Recurrence (CAPRs):
Corrective Action to Prevent Recurrence Root Cause Being Addressed                                                      Owner              Due Date (CAPR)
CF1a - Guide Channels        CAPR 1 - Modifications to improve              Completed            Completed Not Used in New Dryer        installation hardware on U-2 Dryer                                    during Q2R18 Design                        [i.e., increased lead-in on dryer mounting blocks, install lug spacer blocks, etc.] - EC 348286, Rev. 1 CAPR 2 - Modifications to improve installation hardware on U-1 Dryer
{i.e., enlarging base ring RPV lug                                    Completed Completed cutouts) - EC 351167, Rev. 1                                          during Q1R18 CF1b - Ovality Results in     CAPR 3 - Modifications to improve              Completed            Completed Looser Installation           installation hardware on U-2 Dryer                                    during Q2R18 Clearances                    [i.e., guide rod block extension] - EC 348286, Rev. 1 CF4- Vane Bank E End        CAPR 4 - Analysis to justify leave              Completed            Completed Plate crack, caused by        as is position (Ref. 17).                                          during Q2R18 little metal between end plates, and proximity to a weld transition (stress riser).
CF5- Latch Box cracking      CAPR 5 - Repair to this area. - EC              Completed            Completed at 220&deg;, caused by high      348286, Rev. 1                                                        during Q2R18 residual weld stress from weld end discontinuity and corner location.
Page 37 of 43


Clearances The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam dryers were/are constructed in two halves, shipped and welded together at J. T. Cullen. Measurements showed that the dryer skirt was oval following the welding. Th e looseness caused by the ovality is postulated to be an element in the dryer removal event. The lessons
X. Corrective Actions:
 
Cause Being Addressed     Corrective Action (CA) or Action Item (ACIT)     Owner               Due Date CF2: Analysis &               This RCA concluded that recently            See ATT. 9          See Att. 9 Inspections of Damage         approved corrective actions for a from Q2P03 lift event         RCA related to Quad Cities concluded use as is.       Electromatic Relief Valve Solenoid (Lack of rigor in analysis,  Actuator Failures (Ref. 38) are limited follow-up            well aligned with CF2 for this RCA, inspections.)                and are appropriate corrective actions for this RCA. The corrective actions are comprehensive, and will establish revised programmatic controls to ensure additional rigor is applied to situations similar to the Lifting Event.
learned regarding rigging and welding to prevent the dryer from becoming oval have been incorporated in the fabrication of these three
These corrective actions are provided as ATT. 9 to this RCA.
 
CF3 - Operating Loads on       Unit 2 - Install Acoustic Side               Complete            Completed Dryers During EPU              Branches (ASBs) to reduce vibration                               during Q2R18 Conditions                    levels - EC 359004, Rev. 1 Unit 1 - Install Acoustic Side               A8452DEM            AT 435858-Branches (ASBs) to reduce vibration                               37 due levels - EC 359006, Rev. 1                                       05/26/2006 XI. Effectiveness Reviews (EFRs):
dryers. CF2: Analysis &
CAPR / CA being addressed               Effectiveness Review Action             Owner             Due Date CAPR 1 & 3 -                     Remove and re-install the U-2                Rx. services.      Q2R19 Modifications to improve         replacement dryer during Q2R19.                                  May 2008 installation hardware on U-2     Verify that available clearances are Dryer [i.e., increased lead-in   acceptable to prevent damage during on dryer mounting blocks,       future dryer installation and removal install lug spacer blocks,       activities. The U-2 dryer was modified etc.] - EC 348286, Rev. 1       with improved installation hardware in Q2R18. The U-2 Dryer is slightly different from U-1 due to the ovality issue. This action will validate the effectiveness of CAPR 1 & 3.
Inspections of Damage from Q2P03 lift event
AT 472321 - XX (est. after RCA approval)
 
Page 38 of 43
concluded "use as is". GE
 
FDDR, and site review
 
concluded:
 
Modify base ring for separator guide rods Run for 1 cycle  Repair/modify base ring for RPV Lugs in
 
Q2R18  The evaluations, examinations and analyses performed immediately after the dryer lift event in Q2P03 did not have sufficient rigor. As noted in the Evaluation section, it is likely that these weaknesses, especially in the analysis area, would not have changed the outcome of the event, however there is some finite possibility of a missed
 
opportunity to prevent this event from this CF. The Programmatic/ Organizational issues associated wi th this CF are unlikely to be repeated in dryer components, given the limited population of similar dryers, but there are extent of cond ition concerns related to other RCA reports reviewed as part of this analysis. Several corrective actions recently initiated in these other RCA are well aligned with this CF, and should be expected to have a positive impact on this concern.
These items will be addressed in more detail in the subsequent
 
Corrective Actions section of this report.
CF3 - Data Collection From Instrumented Dryer
 
Acoustic Loading @ 150 Hz Vibrations are present to a degree in all the Units. They are measured and used in the analyses or compared to analyzed levels.
Consequently this should not be an issue for other stations / units.
CF4 - Issue 2:  Bank "E" End Plate Cracking Section 1 of Reference 19 reads in part: "Following the discovery of cracking <in Gusset 19>, all remaini ng locations were inspected. All of the other gussets were found to be acceptable with no evidence of cracking."  Therefore, it is concluded that this is an isolated incident.
CF5 - Issue 3: Steam Dryer Latch Box Cracking Latch box protectors have been installed under EC 351167, Rev. 1 for Unit 1 and EC 348286, Rev. 0 for Unit 2. No other latch boxes were found cracked during th ese installations.
Page 36 of 43 VII. Risk Assessment:
Plant-specific risk consequence Basis for Determination Industrial Safety - Minimal Risk Although the load cell display was not functioning, the circ uitry does not allow a lift of over 125 tons nominal.
Given the safety factor of 5 required for the crane and other lifting members, the members would have been able to withstand the load up to the cr ane lift cutout without failing. Nuclear Safety - Minimal Risk Dryer component cracking could result in lost parts. Various lost parts analyses have been performed in the past (most recently for a steam dryer 94 lb. lifting lug for Unit 1 and a steam dryer 9" x 6" plate for Unit 2). The most significant consequence has been determined to be a risk to production. No risks to nuclear safety have been found. Additionally, the Quad Cities Risk Management Expert and the Corporat e Model Owner have reviewed the Steam Dryer Gusset Cracking Conditi on (IR 473034), the Steam Dryer Skirt Cracking Condition (IR 472321) and GE-NE-0000-0052-6385-R0, Lost Parts Analysis for Dryer Lifting Lug and Dryer Skirt Panel Unit 1, to provide support for the PRA modeling. Basically, the risk assessment review found the risk increase associated with these conditions to be minimal and not risk significant, as documented in Reference 26.
Regulatory Impact - Minimal Risk There is Regulatory Impact from the standpoint that the Station has assured the Regulator that a more robust dryer has been installed, that the loading on the dryer is understood, the dr yer has been shown analytically to be able to withstand the loading and that there should be no cracking of the dryer.
However, dryer cracking was found during Q2R18, resulting in a decrease in the credibility of the Station with the Regulator. Note that the dryers are non-safety related, seismically designed. Due to the location of the cracking and the measure strain hardening of the dryer material, the cause of the cracking is judged to be the lift event. Inspec tion of the Unit 1 dryer during Q1M19 determined that this undamaged dryer did not have cracking comparable to the Unit 2 dryer supporting the conclusi on that the dryers were designed adequate to withstand the loads (minus a lifting event) as committed to the Regulators.
Production / Cost -
Minimal Risk Based on the following, there is minimal lik elihood of recurren ce of this dryer cracking event:  a. GE's root cause analysis of th e dryer 140&deg; skirt cracking, Reference 21, identifies the lift event and consequent material strain hardening as the probable cause,  b. Dryer analysis using measured vibra tion loads and confirmed using strain gages shows that the dryer is able to withstand the operating loadings and c. The Unit 1 dryer (without a lift event) as-found condition following approximately 10 months of operation, about 1/2 that time at EPU power levels, was acceptable and as expected.
Page 37 of 43 VIII. Previous Events:
Previous Events Previous Event Review None Many OPEX reports were found th at identified cracking and most of them identified flow induced vibr ation or undersized welds as the cause. No case was found of dryer damage due to or during lifting of the dryer.
IX. Corrective Actions to Prevent Recurrence (CAPRs)
:    Root Cause Being Addressed Corrective Action to Prevent Recurrence (CAPR) Owner Due Date CF1a - Guide Channels Not Used in New Dryer Design CAPR 1 -  Modifications to improve installation hardware on U-2 Dryer
[i.e., increased lead-in on dryer
 
mounting blocks, in stall lug spacer blocks, etc.] - EC 348286, Rev. 1 CAPR 2 - Modifications to improve installation hardware on U-1 Dryer
 
{i.e., enlarging base ring RPV lug cutouts) - EC 351167, Rev. 1 Completed
 
Completed Completed during Q2R18
 
Completed during Q1R18 CF1b - Ovality Results in Looser Installation
 
Clearances CAPR 3 - Modifications to improve installation hardware on U-2 Dryer
 
[i.e., guide rod block extension] - EC
 
348286, Rev. 1 Completed Completed during Q2R18 CF4- Vane Bank "E" End
 
Plate crack, caused by little metal between end plates, and proximity to a weld transition (stress riser). CAPR 4 - Analysis to justify leave "as is" position (Ref. 17). 
 
Completed
 
Completed during Q2R18
 
CF5- Latch Box cracking at 220 , caused by high residual weld stress from weld end discontinuity and
 
corner location. CAPR 5 - Repair to this area. - EC 348286, Rev. 1
 
Completed
 
Completed during Q2R18
 
Page 38 of 43 X. Corrective Actions:
Cause Being Addressed Corrective Action (CA) or Action Item (ACIT) Owner Due Date CF2: Analysis & Inspections of Damage from Q2P03 lift event  
 
concluded "use as is".
(Lack of rigor in analysis, limited follow-up
 
inspections.)   This RCA concluded that recently approved corrective actions for a RCA related to "Quad Cities Electromatic Relief Valve Solenoid
 
Actuator Failures-"  (Ref. 38) are well aligned with CF2 for this RCA, and are appropriate corrective actions for this RCA. The corrective actions are comprehensive, and will establish revised programmatic controls to  
 
ensure additional rigor is applied to situations similar to the Lifting Event.
These corrective actions are provided  
 
as ATT. 9 to this RCA. See ATT. 9 See Att. 9 CF3 - Operating Loads on Dryers During EPU Conditions Unit 2 - Install Acoustic Side Branches (ASBs) to reduce vibration levels - EC 359004, Rev. 1  
 
Unit 1 - Install Acoustic Side Branches (ASBs) to reduce vibration levels - EC 359006, Rev. 1 Complete    A8452DEM Completed during Q2R18 AT 435858-37 due 05/26/2006 XI. Effectiveness Reviews (EFRs):
CAPR / CA being addressed Effectiveness Review Action Owner Due Date CAPR 1 & 3 - Modifications to improve  
 
installation hardware on U-2  
 
Dryer [i.e., increased lead-in on dryer mounting blocks, install lug spacer blocks, etc.] - EC 348286, Rev. 1 Remove and re-install the U-2 replacement dryer during Q2R19.
Verify that available clearances are acceptable to prevent damage during future dryer installation and removal activities. The U-2 dryer was modified with improved installation hardware in  
 
Q2R18. The U-2 Dryer is slightly  
 
different from U-1 due to the "ovality" issue. This action will validate the effectiveness of CAPR 1 & 3. AT 472321 - XX (est. after RCA approval)
Rx. services. Q2R19  May 2008 
 
Page 39 of 43 CAPR 2 - Modifications to improve installation
 
hardware on U-1 Dryer
 
{i.e., enlarging base ring
 
RPV lug cutouts) - EC
 
351167, Rev. 1 Remove and re-install the U-1 replacement dryer during Q1M19. The U-1 dryer was previously modified with improved installation hardware in
 
May 2005. This action will validate effectiveness of CAPR 2 by demonstrating that the dryer can be removed and installed without damage. Rx. services Completed in Q1M19:  No dryer removal or installation problems encountered.
Validates major RCA conclusions regarding cause of  3 cracking events in the
 
U-2 Dryer.  (CF's 1a & 1b-
 
for Event 1,  CF4 for Event
 
2, CF5 for Event 3)  Inspection of the U-1 replacement dryer during Q1M19 concluded:
: 1)  U-1 does not exhibit the skirt-cracking present on U-2 during Q2R18 which supports the position of this RCA that the U-2 lifting event was the
 
cause for the skirt cracking.
: 2) No evidence Vane Bank or Latch Box cracking  which supports position that Events 1 & 2 of this RCA do not
 
represent generic design weaknesses or
 
operating cycle concerns for the replacement dryers.
Programs Engineering Completed Q1M19:  Confirmed no similar damage to U-1 Dryer  (Ref. 39)
 
CAPR 4 - Analysis to justify leaving Vane Bank "E" cracking "as is" (Ref.
 
17). Future inspections in Vane Bank "E" area during next U-2 outage to verify condition remains acceptable to leave
 
as is. AT 472321 - XX (est. after RCA approval)
A8451NESPR During Q2R19
[5/31/2008]
CAPR 5 - Repair to Latch Box cracking at 220 - EC 348286, Rev. 1 Future inspections in Latch Box area during next U-2 outage to verify repair completed in Q2R18 was successful in


CAPR 2 - Modifications to        Remove and re-install the U-1              Rx. services        Completed in Q1M19: No dryer improve installation            replacement dryer during Q1M19. The                            removal or hardware on U-1 Dryer            U-1 dryer was previously modified                              installation
{i.e., enlarging base ring      with improved installation hardware in                        problems encountered.
RPV lug cutouts) - EC            May 2005. This action will validate 351167, Rev. 1                  effectiveness of CAPR 2 by demonstrating that the dryer can be removed and installed without damage.
Validates major RCA              Inspection of the U-1 replacement          Programs            Completed Engineering        Q1M19:
conclusions regarding cause      dryer during Q1M19 concluded:                                  Confirmed no of 3 cracking events in the      1) U-1 does not exhibit the skirt-                            similar damage to U-2 Dryer. (CFs 1a & 1b-                                                                      U-1 Dryer cracking present on U-2 during Q2R18 for Event 1, CF4 for Event      which supports the position of this (Ref. 39) 2, CF5 for Event 3)              RCA that the U-2 lifting event was the cause for the skirt cracking.
: 2) No evidence Vane Bank or Latch Box cracking which supports position that Events 1 & 2 of this RCA do not represent generic design weaknesses or operating cycle concerns for the replacement dryers.
CAPR 4 - Analysis to            Future inspections in Vane Bank E        A8451NESPR          During justify leaving Vane Bank        area during next U-2 outage to verify                          Q2R19 E cracking as is (Ref.      condition remains acceptable to leave                          [5/31/2008]
17).                            as is.
AT 472321 - XX (est. after RCA approval)
CAPR 5 - Repair to Latch        Future inspections in Latch Box area      A8451NESPR          During Box cracking at 220&deg; - EC        during next U-2 outage to verify repair                        Q2R19 348286, Rev. 1                  completed in Q2R18 was successful in                          [5/31/2008]
preventing future cracking.
preventing future cracking.
AT 472321 - XX (est. after RCA approval)
AT 472321 - XX (est. after RCA approval)
A8451NESPR During Q2R19 [5/31/2008]
XII. Programmatic/Organizational Issues:
XII. Programmatic/Organizational Issues:
This RCA identified two programmatic/organizational issues:
This RCA identified two programmatic/organizational issues:
A. The original disposition of the lifti ng event in Q2P03 (May 2005) lacked rigor, and was potentially a missed opportunity to prevent the dryer skirt cracking. B. Multiple examples of unanticipated negative consequences from the replacement dryer design.
A. The original disposition of the lifting event in Q2P03 (May 2005) lacked rigor, and was potentially a missed opportunity to prevent the dryer skirt cracking.
Page 40 of 43 Item A, the original disposition of the lifti ng event, has been extensively discussed in previous sections of this RCA since it is considered a contributing cause to these events (CF2). As such, there is no need for additiona l clarifying discussion in this section. Item B, related to unanticipated negative consequences of the replacement dryer design change, will be discussed in more detail to provide specific examples and to clarify the impacts of this issue. Both issues are included in the table at the end of this section, which summarizes the issue and associated corrective actions.
B. Multiple examples of unanticipated negative consequences from the replacement dryer design.
Unanticipated Negative Design Consequences
Page 39 of 43
:  This RCA noted several examples of negative consequences from the design of the replacement dryer. This includes: 1. Separator guide rod interfere nce with the dr yer skirt ring.
This issue resulted when the replacement dryer design did not ensure that fit-up problems did not exist. This issue became an initiating factor for the lifting event. 2. The change in dryer installation hardware from full-length guide channels to guide slots and base ring cutouts was a causal factor (CF1a) for the lifting event. This issue resulted when the potential nega tive consequences of the design change were not identified despite completing the requirements of the design change process, and associated cross disciple reviews. 3. The initial response to the ovality issue included a modification to install guide rod spacer blocks (Ref. 9) to address clearance concerns. This initial modification was completed prior to dryer installati on, but was insufficient to prevent the ovality problem from becoming a causal f actor (CF1b) for the lifting event. 4. The replacement dryer differential pressure (dP) did not match the design specified value. This issue was the s ubject of a separate RCA - Ref. 37. The unexpectedly low dP of the replacement dryer dP had negative impacts of:  a) Increased complexity and costs associated with fuel analysis for subsequent
 
operating cycles, and  b) Degraded mois ture carryover performance from the new dryers.        The number of unanticipated negative consequences from the replacement dryer design clearly demonstrate a programmatic and organi zational weakness. Th e consequences of these items clearly warra nt corrective action. As noted in the "Evaluati on" section, the issue of unanticipated negative design consequences identified in this RCA shared some similarities with two other RCA's:  Electromatic Relief Valve Solenoid Failures (Ref. 38). QC2 Replacement Steam Dryer Impact on Fuel Analysis Results" (Ref. 37)  A review of the corrective actions associated with these RCA's identified that several of the items in progress would be well positioned to address the issue identified in this RCA.
Page 41 of 43 Attachment 9, section B., lists these corre ctive actions already tracked by AT's under Refs. 37 & 38. In September of 2005 a Common Cause Analysis (CCA) was completed on modifications (AR 317566) which identified a need to improve the effectiveness of inter-departmental reviews associated with the design change process. Corrective actions associated with the CCA were implemented in fall 2005, so they would not have impacted the events of this RCA, which occurred in May 2005. A follow-up action is recommended to perform an effectiveness review of the CCA corrective action implementation to determine if they have been successful in improving the use of the inter-departmental reviews in identifying and avoiding unanticipated ne gative consequences of design changes.
Section B of the table below summarizes the intent of the actions in progress from the other RCA's and lists the actions to be tracked under this RCA.
Programmatic and Organizational Weaknesses Corrective Action (CA) or Action Item (ACIT) Owner Due Date Item A: Review & Disposition of Lifting Event Damage
 
During Q2P03 As noted in the previous Corrective Actions section, this CF will be addressed by recently approved corrective actions associated with the
 
ERV Actuator RCA. These actions are intended to improve the application of formal decision-making
 
processes under conditions similar to the lift event in this RCA. Formal decision making processes will enhance the level of rigor. These actions are listed in Att. 9, Section A of this RCA. See ATT. 9 See ATT. 9 Page 42 of 43 Programmatic and Organizational Weaknesses Corrective Action (CA) or Action Item (ACIT) Owner Due Date Item B:  Unanticipated Negative Design Consequences Similar issues identified and tracked under other RCA's  (Refs. 37 & 38) are listed in Att. 9. These CA's are expected to improve the effectiveness of inter-departmental reviews of design changes, and to improve the coordination of major modifications that become Exelon projects. New CA's specific to this RCA are listed below.
: 1. Quad Cities to implement Rev. 1 of HU-AA-1212, "Technical Task Risk/ Rigor Assessment-" which includes guidance on how to select what type of third-party review(s) are required.
: 2. Design Eng. to complete an effectiveness review (EFR) of the corrective actions (CA's) implemented from CCA 317566.
The overall intent of this EFR is to determine if the CA's have improved the use of the inter-departmental reviews in identifying
 
and avoiding unanticipated negative


consequences of design changes.   (An example directly from this RCA would be: More detailed Reactor Services review
Item A, the original disposition of the lifting event, has been extensively discussed in previous sections of this RCA since it is considered a contributing cause to these events (CF2). As such, there is no need for additional clarifying discussion in this section. Item B, related to unanticipated negative consequences of the replacement dryer design change, will be discussed in more detail to provide specific examples and to clarify the impacts of this issue.
& challenge to ensure the design is usable for dryer installation activities.)   See ATT. 9
Both issues are included in the table at the end of this section, which summarizes the issue and associated corrective actions.
Unanticipated Negative Design Consequences:
This RCA noted several examples of negative consequences from the design of the replacement dryer. This includes:
: 1. Separator guide rod interference with the dryer skirt ring. This issue resulted when the replacement dryer design did not ensure that fit-up problems did not exist. This issue became an initiating factor for the lifting event.
: 2. The change in dryer installation hardware from full-length guide channels to guide slots and base ring cutouts was a causal factor (CF1a) for the lifting event.
This issue resulted when the potential negative consequences of the design change were not identified despite completing the requirements of the design change process, and associated cross disciple reviews.
: 3. The initial response to the ovality issue included a modification to install guide rod spacer blocks (Ref. 9) to address clearance concerns. This initial modification was completed prior to dryer installation, but was insufficient to prevent the ovality problem from becoming a causal factor (CF1b) for the lifting event.
: 4. The replacement dryer differential pressure (dP) did not match the design specified value. This issue was the subject of a separate RCA - Ref. 37. The unexpectedly low dP of the replacement dryer dP had negative impacts of: a)
Increased complexity and costs associated with fuel analysis for subsequent operating cycles, and b) Degraded moisture carryover performance from the new dryers.
The number of unanticipated negative consequences from the replacement dryer design clearly demonstrate a programmatic and organizational weakness. The consequences of these items clearly warrant corrective action.
As noted in the Evaluation section, the issue of unanticipated negative design consequences identified in this RCA shared some similarities with two other RCAs:
* Electromatic Relief Valve Solenoid Failures (Ref. 38).
* QC2 Replacement Steam Dryer Impact on Fuel Analysis Results (Ref. 37)
A review of the corrective actions associated with these RCAs identified that several of the items in progress would be well positioned to address the issue identified in this RCA.
Page 40 of 43


A8400PM -QDCDW AT 472321
Attachment 9, section B., lists these corrective actions already tracked by ATs under Refs. 37 & 38.
- XX (ACIT)
In September of 2005 a Common Cause Analysis (CCA) was completed on modifications (AR 317566) which identified a need to improve the effectiveness of inter-departmental reviews associated with the design change process. Corrective actions associated with the CCA were implemented in fall 2005, so they would not have impacted the events of this RCA, which occurred in May 2005. A follow-up action is recommended to perform an effectiveness review of the CCA corrective action implementation to determine if they have been successful in improving the use of the inter-departmental reviews in identifying and avoiding unanticipated negative consequences of design changes.
A8452 NESDP  AT 472321
Section B of the table below summarizes the intent of the actions in progress from the other RCAs and lists the actions to be tracked under this RCA.
- XX (ACIT) (est. after RCA approval)      See ATT. 9  
Programmatic and Organizational Corrective Action (CA) or Action Item (ACIT)     Owner          Due Date Weaknesses Item A: Review & Disposition       As noted in the previous Corrective            See ATT. 9        See ATT. 9 of Lifting Event Damage            Actions section, this CF will be During Q2P03                      addressed by recently approved corrective actions associated with the ERV Actuator RCA.
These actions are intended to improve the application of formal decision-making processes under conditions similar to the lift event in this RCA. Formal decision making processes will enhance the level of rigor. These actions are listed in Att.
9, Section A of this RCA.
Page 41 of 43


07/31/06  
Programmatic and Organizational Corrective Action (CA) or Action Item (ACIT)              Owner            Due Date Weaknesses Item B: Unanticipated              Similar issues identified and tracked under            See ATT. 9            See ATT. 9 other RCAs (Refs. 37 & 38) are listed in Negative Design Att. 9. These CAs are expected to improve Consequences                        the effectiveness of inter-departmental reviews of design changes, and to improve the coordination of major modifications that become Exelon projects. New CAs specific to this RCA are listed below.
: 1. Quad Cities to implement Rev. 1 of HU-AA-1212, Technical Task Risk/ Rigor                    A8400PM -
07/31/06 Assessment which includes guidance on                QDCDW how to select what type of third-party                  AT 472321 review(s) are required.                                - XX (ACIT)
: 2. Design Eng. to complete an effectiveness review (EFR) of the corrective actions                  A8452                11/17/06 (CAs) implemented from CCA 317566.                    NESDP The overall intent of this EFR is to determine AT 472321 if the CAs have improved the use of the
                                                                                            - XX (ACIT) inter-departmental reviews in identifying              (est. after RCA and avoiding unanticipated negative                    approval) consequences of design changes.
(An example directly from this RCA would be: More detailed Reactor Services review
                                    & challenge to ensure the design is usable for dryer installation activities.)
XIII. Other Issues:
Other Issues identified during  Corrective Action (CA) or Action Item Owner                  Due Date investigation                          (ACIT)
: 1. Crane load cell unavailable      a. Evaluate methods to improve              Rx. Services              11/10/06 during Lifting Event                the use of the load cell as a method of early detection of load          AT 472321 -
hang up. This needs to include            XX (ACIT) establishing expected load values,          (est. after RCA and abort criteria when pre-                approval) established thresholds are reached. These methods should be incorporated in to QCMM 5800-05, or other suitable Page 42 of 43


11/17/06  XIII. Other Issues:
Other Issues identified during   Corrective Action (CA) or Action Item Owner          Due Date investigation                            (ACIT) documents. These methods should also discuss appropriate contingencies if the load cell is unavailable, and suitable management review and approval levels for invoking these contingencies. Results of this evaluation should be presented to MRC for closure.
Other Issues identified during investigation Corrective Action (CA) or Action Item (ACIT) Owner Due Date 1. Crane load cell unavailable during Lifting Event
: 2. Crane load cell unavailable       b. Evaluate historical reliability      Plant            09/29/06 during Lifting Event                 of RB Overhead Crane Load cell          Engineering.
: a. Evaluate methods to improve the use of the load cell as a method of early detection of load
display. Determine if actions for      AT 472321 -
improving future reliability are        XX (ACIT) (est.
after RCA warranted. Present results of this      approval) evaluation to PHC for closure.
XIV. Communications Plan: Preliminary NER and OPEX information has already been provided for communication within Exelon and the Nuclear Industry. Final communication actions are being tracked by the AT items below:
Lessons Learned to be Communicated        Communication Plan Action              Owner          Due Date Provide NER to share lessons 472321-09                              A8430TP          06/01/06 learned within Exelon Provide an OPEX to share lessons learned with the rest of     472321-10                              A8401OPEX        06/08/06 the industry Page 43 of 43


"hang up". This needs to include establishing expected load values, and abort criteria when pre-
Lifting Eye (1 of 4)
Lifting Rod (1 of 4)
Mounting Block for Latch Assembly (1 of 4)
Dryer Guide Slots Skirt Base Ring Skirt                                              Dryer Support Ring Drain Channel Cut-Out for RPV Lug (1 of 4)
Figure 1: Steam Dryer


established thresholds are reached. These methods should be incorporated in to QCMM
Separator Guide Rod Cutout              0o (2 Locations) 320o                            20o      40o 5/16 Bend RPV Lug Cutout (4 Locations) 270o                                                            90o 220o                o                    140o 200 180o 5/8 Bend 3/4 Bend Impact on RPV Dryer Support Lug Figure 2 Steam Dryer Plan - Impact Locations


5800-05, or other suitable Rx. Services AT 472321 -
Design & Analyses of                 Fabrication of New Steam Dryer                 Fabrication - Upper & Lower                          Installation - Dryer is Lowered New Steam Dryer                         Upper & Lower Halves                         Halves Welded Together                                Into QC2 Reactor Vessel 2004-2005                            @ U. S. Tool & Die                               @ J. T. Cullen                                       WO 00732708-01             A Prior to March 2005                                March 2005                                              5/11/2005 Dryer Loading is High                A Large Amount of Welding                    Laser measurement of assembled Cycle Flow Induced                    is Required to be Performed                  dryer determines base plate is                         Guides on the dryer support ring Vibrations                      to Assemble the Dryer Parts                  approx. 2 inches out of round                       impact the RPV Dryer Support Lugs 4/4/2005                                   on the way down & bend the spacer blocks.
XX (ACIT)  (est. after RCA approval)  11/10/06 Page 43 of 43 Other Issues identified during investigation Corrective Action (CA) or Action Item (ACIT) Owner Due Date documents. These methods should also discuss appropriate contingencies if the load cell is
GE Used Super-Element to                 Weld NDE Records Lost for Model Skirt Below Water                   300 welds - Consequently,        CF1b Line - Detail of Lower Skirt             Needed to use Reduced Weld Area Not Developed                       Capacity for Analysis          Results in Looser                    Results in                    Dryer base ring hits steam Installation                  Increased Residual              separator guide rods. Dryer can Hardware Clearances                      Stress                      not be lowered any further.
 
Planned Full Penetration Weld Revised to Partial Penetration Plus Fillet Weld On Both Sides of Skirt Plate                                                       DDR 431002828-027 (Ref. 7) Dispositions the Nonconformance Use-As-Is with Additional Guidance Constraints Added to the Lower Guide Block.
unavailable, and suitable management review and approval
CF1a Guide Channels Not Used in New Dryer Design GE issued FDI 085 to install new guide rod spacer blocks and gusset supports.
 
5/4/2005 Cut Out For RPV Dryer Support Lug Judged Acceptable Based On Low Stress in Model ATT. 1: 472321-02 Root Cause Report Effect and Casual Factor (E&CF) Chart                     Att. Page 1
levels for invoking these contingencies. Results of this evaluation should be presented to MRC for closure. 2. Crane load cell unavailable during Lifting Event
: b. Evaluate historical reliability
 
of RB Overhead Crane Load cell display. Determine if actions for improving future reliability are
 
warranted. Present results of this
 
evaluation to PHC for closure.
Plant Engineering.
AT 472321 -
XX (ACIT) (est. after RCA approval)  09/29/06 XIV. Communications Plan
:  Preliminary NER and OPEX information has already been provided for communication within Ex elon and the Nuclear Industry. Final communication actions are being tracked by the AT items below:
Lessons Learned to be Communicated Communication Plan Action Owner Due Date Provide NER to share lessons learned within Exelon 472321-09 A8430TP 06/01/06 Provide an OPEX to share lessons learned with the rest of the industry 472321-10 A8401OPEX 06/08/06
 
Skir tSkirt Base Ring Dryer Support Ring Lifting Eye (1 of 4)Cut-Out for RPV Lug
 
(1 of 4) Drain Channel Figure 1: Steam Dryer Lifting Rod
 
(1 of 4) Dryer Guide SlotsMounting Block fo r Latch Assembl y (1 of 4)
 
20 o 200 o 140 o 40 o 220 o 320 o 0 o 180 o 90 o 270 o Separator Guide Rod Cutout (2 Locations)
RPV Lug Cutout (4 Locations)
Figure 2 Steam Dryer Plan - Impact Locations 3/4" Bend 5/8" Bend 5/16" Bend Impact on RPV
 
Dryer Support Lug
 
ATT. 1: 472321-02 Root Ca use Report Effect and Casu al Factor (E&CF) Chart Att. Page 1
Fabrication of New Steam Dryer Upper & Lower Halves @ U. S. Tool & Die Prior to March 2005 Fabrication - Upper & Lower Halves Welded Together 
@ J. T. Cullen March 2005 DDR 431002828-027 (Ref. 7) Dispositions the Nonconformance "Use-As-Is" with Additional Guidance Constraints Added to the Lower Guide Block. Weld NDE Records Lost for 300 welds - Consequently, Needed to use Reduced Wel dCapacity for Analysis Installation - Dryer is Lowered Into QC2 Reactor Vessel WO 00732708-01 5/11/2005 Guides on the dryer support ring impact the RPV Dryer Support Lugs on the way down & bend the spacer blocks. A Dryer base ring hits steam separator guide rods. Dryer can not be lowered any further. Laser measurement of assembled dryer determines base plate is approx. 2 inches out of round 4/4/2005 GE issued FDI 085 to install new guide rod spacer blocks and gusset supports.
5/4/2005  Design & Analyses of  New Steam Dryer 2004-2005 GE Used Super-Element to Model Skirt Below Water Line - Detail of Lower Skirt Area Not Developed Planned Full Penetration Weld Revised to Partial Penetration Plus Fillet Weld On Both Sides of Skirt Plate Dryer Loading is High Cycle Flow Induced Vibrations Cut Out For RPV Dryer Support Lug Judged Acceptable Based On Low Stress in Model Results in Increased Residual S tr ess Results in Looser Installation Hardware ClearancesA Large Amount of Welding is Required to be Performed to Assemble the Dryer PartsGuide Channels Not Used in New Dryer Design CF1 a CF1 b ATT. 1: 472321-02 Root Ca use Report Effect and Casu al Factor (E&CF) Chart Att. Page 2                               


Installation - Decision made    Disposition of Dryer    Operating Cycle: U2 @          Removal of Dryer from to remove dryer from vessel    Installation Issue and    EPU Power Level                vessel in Q2R18 A            5/12/2005                  Damage            (2800-2900 MWth)                      3/28/2006 5/21/05 to 12/30/05 Event 2                        Event 3 AR 473034: Dryer                    AR 475369:
CF3                            Event 1                  Cracking in Gusset                  Steam Dryer While removing dryer                            CF2                                                          AR 472321:                                                        Cracking in 19 of Vane Bank E from vessel, the dryer base                                                                                      Steam Dryer                                                    220&deg; Latch Box Data Collection From                                                        End Plate Near the ring hangs up on the                                                                                        Lower Skirt vessel dryer support lugs.                                      Instrumented Dryer                                                            320&deg; Location.
ACE, GE FDDR, and                Acoustic Loading @ 150                          Cracked @ 140&deg; analysis concluded to:                      Hz                                      Location
* Modify base ring for separator guide rods RB Overhead Crane was
* Run for 1 cycle used w/o functioning
* Repair/modify base ring                                    4/2006: No Cracking load cell.            for RPV Lugs in Q2R18                                    Identified at 220o Skirt Most probable cause is having Location (Similar very little weld metal between Deformation) or 320o the End Plates, proximity to a Location (Less Deformation)
Weld Transition (Stress Riser)
When the dryer became stuck,                                                                                                            and the Presence of Operating the crane was required to                                                                                                                    Vibration Loads place a force onto the dryer that caused an audible noise. Extent of NDE and Evaluation Lacked                                            4/2006: Metallurgical Rigor for Disposition of                                    Evaluation results of Boat Samples show the crack was                        CF4 Damage due to High Cycle Fatigue IR 334383: Dryer Base Ring found damaged.                                                                                                                                              Inspections note weld end 5/12/2005                                                                                                                                                discontinuity near the area Metallurgical Evaluation                                                    of cracking. Most of Skirt to Base Plate                                                probable cause is high Weld shows Lack of                                                    residual weld stress from Fusion                                                        weld end discontinuity and corner location.
ACE 334383-03:
ACE 334383-03:
New Dryer Design: Did Not Consider Separator Guide Rods Did Not Adequately Address Fit-Up 5/25/2005 IR 334383: Dryer Base Ring found damaged.
New Dryer Design:
5/12/2005 While removing dryer from vessel, the dryer base ring hangs up on the vesseldryersupportlugs.
* Did Not Consider                                                                       Metallurgical Evaluation                                        CF5 Separator Guide Rods                                                                 of Skirt to Base Plate Joint
RB Overhead Crane was used w/o functioning load cell.
* Did Not Adequately                                                                       Identified Transgranular Address Fit-Up                                                                                 Cracking 5/25/2005 ATT. 1: 472321-02 Root Cause Report Effect and Casual Factor (E&CF) Chart                      Att. Page 2
A ACE, GE FDDR, and analysis concluded to: Modify base ring for separator guide rods Run for 1 cycle  Repair/modify base ring for RPV Lugs in Q2R18 Data Collection From Instrumented Dryer Acoustic Loading @ 150 Hz Event 1 AR 472321: Steam Dryer Lower Skirt Cracked @ 140 Location 4/2006: Metallurgical Evaluation results of Boat Samples show the crack was due to High Cycle Fatigue Metallurgical Evaluation of Skirt to Base Plate Weld shows Lack of Fusion Installation - Decision made to remove dryer from vessel 5/12/2005 Disposition of Dryer Installation Issue and Damage  Operating Cycle:  U2 @
  - Event Timeline:
EPU Power Level  (2800-2900 MWth) 5/21/05 to 12/30/05 Removal of Dryer from vessel in Q2R18 3/28/2006 4/2006: No Cracking Identified at 220 o Skirt Location (Similar Deformation) or 320 o Location (Less Deformation)Metallurgical Evaluation of Skirt to Base Plate Joint Identified Transgranular Cracking Extent of NDE and Evaluation Lacked Rigor for Disposition o f Damage Event 2  AR 473034:  Dryer Cracking in Gusset 19 of Vane Bank "E" End Plate Near  the 320 Location.
DATE         EVENT/ ACTION               SOURCE                       COMMENTS DOCUMENT(S)
Most probable cause is having very little weld metal between the End Plates, proximity to a Weld Transition (Stress Riser) and the Presence of Operating Vibration Loads When the dryer became stuck, the crane was required to place a force onto the dryer thatcausedanaudiblenoise.
Prior to Upper and lower halves of
Event 3 AR 475369: Steam Dryer Cracking in 220 Latch Box CF2 CF3 CF4  Inspections note weld end discontinuity near the area of cracking. Most probable cause is high residual weld stress from weld end discontinuity and corner location.
* NR - common        None 3/2005    dryer are fabricated at U.S. information.
CF5 ATT. Page 3 Attachment 2 - Event Timeline:
Tool and Die in Pittsburgh, PA 3/2005   Upper and lower halves of
DATE EVENT/ ACTION SOURCE DOCUMENT(S) COMMENTS Prior to 3/2005 Upper and lower halves of dryer are fabricated at U.S. Tool and Die in Pittsburgh, PA NR - common information. None 3/2005 Upper and lower halves of dryer are welded together at J. T. Cullen, Fulton, IL NR - common information None 4/4/2005 Washington Group begins laser measurements of Assembled Dryer at J. T.  
* NR - common        None dryer are welded together     information at J. T. Cullen, Fulton, IL 4/4/2005 Washington Group begins
 
* Integrated Steam  None laser measurements of         Dryer Project J.T.
Cullen Integrated Steam Dryer Project J.T.
Assembled Dryer at J. T.       Cullen Cullen                         Fabrication Facility Daily Activity Sheet 4/14/2005 QC2 Dryer Base plate is
Cullen Fabrication  
* DDR 431002828-     Disposition provided 4/25/2005, approximately 2 inches out    027                states, Clearances normally of round.
 
* EC 351168          available have been compromised, so additional guidance constraints will be placed on the lower guide block to limit misalignment and assist in installation.
Facility Daily Activity Sheet None 4/14/2005 QC2 Dryer Base plate is approximately 2 inches out
5/4/2005 GE issues FDI to install
 
* FDI 0085           Modification of replacement steam new guide rod spacer                              dryer to install additional guidance blocks and gusset supports.                      constraints 5/11/2005 Lower Dryer into Vessel
of round. DDR 431002828-027 EC 351168 Disposition provided 4/25/2005,   states, "Clearances normally available have been compromised, so additional guidance constraints will be placed on the lower guide block to limit misalignment and assist in installation." 5/4/2005 GE issues FDI to install new guide rod spacer blocks and gusset supports.FDI 0085 Modification of replacement steam dryer to install "additional guidance constraints" 5/11/2005 Lower Dryer into Vessel WO 00732708-01 5/11/2005  
* WO 00732708-01 5/11/2005 Guides on the dryer support
 
* WO 00732708-01 ring impacted the RPV
Guides on the dryer support ring impacted the RPV Dryer Support Lugs on the way down & bent the spacer blocks WO 00732708-01AR 334383 FDDR RMCN 06252  5/11/2005 Hit Steam Separator Guide Rod with Dryer Base Ring - Dryer could not be lowered  
* AR 334383 Dryer Support Lugs on the
 
* FDDR RMCN way down & bent the           06252 spacer blocks 5/11/2005 Hit Steam Separator Guide
any further WO 00732708-01AR 334348 FDDR RMCN 06243 Separator Guide Rod Interference Root Cause Summary (Report Number AI10139)Apparent Cause Evaluation (ACE) 334348 Apparent Cause per ACE: 1. Lack of clearance between dryer base ring and separator guide rods due to wider skirt base ring plate (same OD, smaller ID). 2. Excessive clearance between dryer guide rods and the dryer. Root Cause Investigation (AR 00330331-03) was supposed to address Steam Dryer design (but did not). Poor Design was only cause Corrective Action per ACE: Modify dryer per EC 348286 (see 26A6787 Rev. 2 3/7/06) 5/12/2005 Decision made to remove dryer from vessel  WO 00732708-01
* WO 00732708-01 Apparent Cause per ACE:
 
Rod with Dryer Base Ring -
ATT. Page 4 DATE EVENT/ ACTION SOURCE DOCUMENT(S) COMMENTS 5/12/2005 While removing dryer from vessel the dryer base ring hung up on the vessel dryer support lugs - "Lift Event" WO 00732708-01AR 334383 FDDR RMCN 06245 Prompt Inv. Report  Apparent Cause Evaluation (ACE) Performed under AR 334348 5/13/2005 Reinstallation of dryer into vessel. WO 00732708-01 5/16/2005 Repair of the Reactor Building Overhead Crane
* AR 334348 Dryer could not be lowered
 
* FDDR RMCN         1. Lack of clearance between dryer any further                    06243                  base ring and separator guide
Load Cell WO 00805641-02 5/16/2005 Q2C18 Operated at EPU and Pre-EPU power levels NR - common information 3/28/2006 U-2 Steam Dryer Lifting Lugs Rotated WO 00794824-01AR 471848 INR Q2R18-IVVI-06-01 Operability Eval.  # EC 360272 Op. Eval. scope included IR's:
* Separator Guide        rods due to wider skirt base ring Rod Interference        plate (same OD, smaller ID).
 
Root Cause        2. Excessive clearance between Summary (Report        dryer guide rods and the dryer.
471848 / 472321 / 473034 / 473344 3/28/2006 Removal of dryer from vessel. WO 00794824-01 3/29/2006 U-2 Steam Dryer Lower Skirt Cracked @ 140  WO 00794824-01AR 472321 INR Q2R18-IVVI-06-02 Root Cause Investigation Requested
Number AI10139)
 
* Apparent Cause
"Event 1" 3/30/2006 U-2 Indications Identified on Steam Dryer Gusset WO 00794824-01AR 473034 INR Q2R18-IVVI-06-04 "Event 2" 4/05/2006 U-2 Steam Crack at 220 Latch Box  WO 00794824-01AR 475369 INR Q2R18-IVVI-06-29 "Event 3"
* Root Cause Investigation (AR Evaluation (ACE)          00330331-03) was supposed 334348                    to address Steam Dryer design (but did not).
 
* Poor Design was only cause Corrective Action per ACE:
ATT. Page 5 Attachment 3 - References Ref. # Document Reference Number Title / Description 1 WO 00732708-01 EC 351168 Replace Unit-2 Steam Dryer Per EC 351168 2 AR 334383 May 2005, ACE on Q2P03 Dryer Lifting Event 3 FDDR RMCN 06252 GE disposition of steam dryer interferences between the vessel steam dryer support lug and the lug spacer block. 4 AR 334348 May 2005 Prompt Investigation of Q2P03 Dryer Lifting Event 5 FDDR RMCN 06243 GE disposition of Steam Separator Guide Rod Interference with the Base Ring of the Steam Dryer Skirt. 6  GE Report Number AI10139 GE Root Cause Summary: Separator Guide Rod Interference  7 DDR 431002828-027 GE Disposition of "Ovality" Issue:  Steam Dryer Final Dimension Approximately 2 Inches Out of Round. 8 FDDR RMCN 06245 GE disposition of May 2205, Q2P03 Lift Event 9 FDI 0085, Rev. 0 and Rev. 1 Engineering requirements and instructions for the modifications of the replacement steam dryer to be installed at QC Unit 2 prior to the Q2P03 dryer replacement outage.
* Modify dryer per EC 348286 (see 26A6787 Rev. 2 3/7/06) 5/12/2005 Decision made to remove
(Modified Jack Bolts, Installed Guide Rod Spacer Blocks, and
* WO 00732708-01 dryer from vessel ATT. Page 3
 
Gusset Supports.) 10 AR 472321 Q2R18 Identified Crack In The U2 Steam Dryer Skirt.
("Event 1" of this RCA.) 11 INR Q2R18-IVVI-06-02 Steam Dryer Skirt @135 Degrees  (Note: Most Later References Specify 140) 12 AR 473034 Q2R18 IVVI - Indication s on Steam Dryer Gusset  (E-Bank End Plate Crack).  ("Event 2" of this RCA.) 13 INR Q2R18-IVVI-06-04 Steam Dryer Bank E ID 14 AR 475369 Q2R18 Identified 220 Degree Latch Box Crack ("Event 3" of this RCA) 15 INR Q2R18-IVVI-06-29 220 Degree Latch Box Crack 16 GENE 0000-0053-1962 GE Review of Transgranular Stress Corrosion Cracking in Skirt to Base Weld Root Area 17 GE-NE-0000-0052-9728 GE Evaluation of the Bank E Drying Vane End Plate Crack
("Event 2" of this RCA.)
18 GE-NE-0000-0053-0232 QC U-2 Replacement Steam Dryer Analysis Evaluation of Latch Box Cracking and Fatigue Impact of Swing Arm & Latch Protector Welds  ("Event 3" of this RCA) 19  GE-NE-0000-0052-9666 QC U-2 Replacement Steam Dryer Metallurgical Evaluation ATT. Page 6 Ref. # Document Reference Number Title / Description 20  GE-NE-0000-0052-6385-RO Lost Parts Analysis for Potential Lost Dryer Lifting Eye and Dryer Skirt Panel Quad Cities U-1 


21 GE-NE-0000-0053-2926 Root Cause Analysis for QC2 Steam Dryer 140 Skirt Cracking  ("Event 1" of this RCA) 22  DDR dated 02/20/2005 Dryer Support Ring 3/8" Out of Flat due to Welding Distortion.
DATE          EVENT/ ACTION                SOURCE                    COMMENTS DOCUMENT(S) 5/12/2005 While removing dryer from
23 GE LFW0505-2, May 20, 2005, DRF
* WO 00732708-01    Apparent Cause Evaluation (ACE) vessel the dryer base ring
* AR 334383        Performed under AR 334348 hung up on the vessel dryer
* FDDR RMCN support lugs - Lift Event    06245
* Prompt Inv.
Report 5/13/2005 Reinstallation of dryer into
* WO 00732708-01 vessel.
5/16/2005 Repair of the Reactor
* WO 00805641-02 Building Overhead Crane Load Cell 5/16/2005 Operated at EPU and Pre-Q2C18    EPU power levels              NR - common information 3/28/2006 U-2 Steam Dryer Lifting
* WO 00794824-01    Op. Eval. scope included IRs:
Lugs Rotated
* AR 471848
* INR Q2R18-IVVI-  471848 / 472321 / 473034 / 473344 06-01
* Operability Eval.
                                          # EC 360272 3/28/2006 Removal of dryer from
* WO 00794824-01 vessel.
3/29/2006 U-2 Steam Dryer Lower
* WO 00794824-01    Root Cause Investigation Requested Skirt Cracked @ 140&deg;
* AR 472321
* INR Q2R18-IVVI-  Event 1 06-02 3/30/2006 U-2 Indications Identified on
* WO 00794824-01    Event 2 Steam Dryer Gusset
* AR 473034
* INR Q2R18-IVVI-06-04 4/05/2006 U-2 Steam Crack at 220&deg;
* WO 00794824-01    Event 3 Latch Box
* AR 475369
* INR Q2R18-IVVI-06-29 ATT. Page 4
  - References Ref. Document                                  Title / Description
#    Reference Number 1    WO 00732708-01      Replace Unit-2 Steam Dryer Per EC 351168 EC 351168 2    AR 334383          May 2005, ACE on Q2P03 Dryer Lifting Event 3    FDDR RMCN          GE disposition of steam dryer interferences between the vessel 06252              steam dryer support lug and the lug spacer block.
4    AR 334348          May 2005 Prompt Investigation of Q2P03 Dryer Lifting Event 5    FDDR RMCN          GE disposition of Steam Separator Guide Rod Interference 06243              with the Base Ring of the Steam Dryer Skirt.
6      GE Report Number  GE Root Cause Summary: Separator Guide Rod Interference AI10139 7    DDR 431002828-      GE Disposition of Ovality Issue: Steam Dryer Final 027                Dimension Approximately 2 Inches Out of Round.
8    FDDR RMCN          GE disposition of May 2205, Q2P03 Lift Event 06245 9    FDI 0085, Rev. 0    Engineering requirements and instructions for the and Rev. 1          modifications of the replacement steam dryer to be installed at QC Unit 2 prior to the Q2P03 dryer replacement outage.
(Modified Jack Bolts, Installed Guide Rod Spacer Blocks, and Gusset Supports.)
10    AR 472321          Q2R18 Identified Crack In The U2 Steam Dryer Skirt.
(Event 1 of this RCA.)
11    INR Q2R18-IVVI-    Steam Dryer Skirt @135 Degrees 06-02               (Note: Most Later References Specify 140&deg;)
12    AR 473034          Q2R18 IVVI - Indications on Steam Dryer Gusset (E-Bank End Plate Crack). (Event 2 of this RCA.)
13    INR Q2R18-IVVI-    Steam Dryer Bank E ID 06-04 14    AR 475369          Q2R18 Identified 220 Degree Latch Box Crack (Event 3 of this RCA) 15    INR Q2R18-IVVI-    220 Degree Latch Box Crack 06-29 16    GENE 0000-0053-    GE Review of Transgranular Stress Corrosion Cracking in 1962                Skirt to Base Weld Root Area 17    GE-NE-0000-0052-    GE Evaluation of the Bank E Drying Vane End Plate Crack 9728                (Event 2 of this RCA.)
18    GE-NE-0000-0053-    QC U-2 Replacement Steam Dryer Analysis Evaluation of 0232                Latch Box Cracking and Fatigue Impact of Swing Arm &
Latch Protector Welds (Event 3 of this RCA) 19    GE-NE-0000-0052-    QC U-2 Replacement Steam Dryer Metallurgical Evaluation 9666 ATT. Page 5


0000-0034-3781 Quad Cities U-1&2 Replacement Dryer Skirt Cutouts: (Discusses modifications n eeded to both U-1 and U-2 replacement dryers as a result of Q2P03 Issues.) 24 GE Transmittal No.
Ref. Document                                  Title / Description
JXD4E-023 dated  
#    Reference Number 20  GE-NE-0000-0052- Lost Parts Analysis for Potential Lost Dryer Lifting Eye and 6385-RO            Dryer Skirt Panel Quad Cities U-1 GE-NE-0000-0053- Root Cause Analysis for QC2 Steam Dryer 140&deg; Skirt 21  2926              Cracking (Event 1 of this RCA) 22  DDR dated          Dryer Support Ring 3/8 Out of Flat due to Welding 02/20/2005        Distortion.
23  GE LFW0505-2,      Quad Cities U-1&2 Replacement Dryer Skirt Cutouts:
May 20, 2005, DRF (Discusses modifications needed to both U-1 and U-2 0000-0034-3781    replacement dryers as a result of Q2P03 Issues.)
24   GE Transmittal No. As-Built Dimensional Analysis, QC-2 Steam Dryer (Report JXD4E-023 dated   describing why the U-2 Replacement Dryer will fit in the 4/28/2005          vessel despite the ovality issue) 25  GE-NE-0000-0034- Replacement Steam Dryer Reactor Vessel Bracket Stress 4803-02            Report for Quad Cities 1,2 and Dresden 2,3, April 2005.
RM Documentation Risk Assessment for IR 473034 and IR 472321, Steam Dryer 26  No. SA-1477        Gusset Cracking and Steam Dryer Skirt Cracking, Assignment 03 Root Cause Report.
27  GENE 0000-0052- GE Steam Dryer - Recommendation for Repairs at 220 &deg; &
8407 & 8408        320&deg; Locations (2 documents - same topic) 28  FDDR              Q2R18 Addition of Dryer Guide Rod Block Extensions RMCN08436 29  GE-NE-0000-0053- QC U-2 Replacement Steam Dryer Analysis Detailed Stress 2910              Analysis of Skirt Base Plate Cutout and Gussets, April 2006 30  Exelon-ENG-DRY- Exelon Concurrence with GE Resolution of U-2 Steam Dryer 099CR              Collision Damage. Dated May 24, 2005.
31  GENE-0000-0052- Q2R18 Steam Dryer ID Welds Flaw Evaluation, April 2006.
7988 Rev. 2 32  FDDR              Ring and Skirt Assembly, dated 04/05/06. (Specifications RMCN08404          and drawings for repair to 220&deg; area.)
33  GENE 0000-0053- QC2 Steam Dryer - Base Ring Diametral Distortion 0605-1            (April 2006 re-assessment of ovality issue) 34  GENE 0000-0053- QC2 Steam Dryer Repair Crevice Assessment (Discussion of 0606              acceptability of skirt plate repairs using backing rings).
35  GENE 0000-0043- QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis 3105-01-P          Based on Measured EPU Conditions (July 2005) 36  GE-NE-0000-0053- QC U-2 Replacement Steam Dryer Analysis Detailed Stress 2456-P            Analysis of Dryer Lifting (April 2006) 37  AR 330331          RCA: QC2 Replacement Steam Dryer Impact on Fuel Analysis Results 38  AR 435858          RCA: Electromatic Relief Valve Solenoid Actuator Failures due to failure to correct the source of the MSL vibrations 39  EC 360876          Review of Q1M19 Critical Steam Dryer Inspection Findings ATT. Page 6


4/28/2005 As-Built Dimensional Analysis, QC-2 Steam Dryer (Report describing why the U-2 Replacement Dryer will fit in the vessel despite the ovality issue) 25 GE-NE-0000-0034-4803-02 Replacement Steam Dryer Reactor Vessel Bracket Stress Report for Quad Cities 1,2 and Dresden 2,3", April 2005.  
Ref. Document                                    Title / Description
 
#   Reference Number 40   GENE 0000-0053-     Request for Additional Information: QC U-2 Dryer Inspection, 2954, Revision 1    Start-up & Power Ascension Plan - RAI 9 (b):
26 RM Documentation No. SA-1477 Risk Assessment for IR 473034 and IR 472321, Steam Dryer Gusset Cracking and Steam Dryer Skirt Cracking, Assignment 03 Root Cause Report. 27 GENE 0000-0052-8407 & 8408 GE Steam Dryer - Recommendation for Repairs at 220  & 320 Locations (2 documents - same topic) 28 FDDR RMCN08436 Q2R18 Addition of Dryer Guide Rod Block Extensions 29 GE-NE-0000-0053-2910 QC U-2 Replacement Steam Dryer Analysis Detailed Stress Analysis of Skirt Base Plate Cutout and Gussets, April 2006 30 Exelon-ENG-DRY-099CR Exelon Concurrence with GE Resolution of U-2 Steam Dryer Collision Damage. Dated May 24, 2005.
Discussion of the corresponding reduction in the fatigue stress limits in the Dryer Skirt Crack.
31 GENE-0000-0052-7988 Rev. 2 Q2R18 Steam Dryer ID Welds Flaw Evaluation, April 2006.
41   Ref. 3 used in GENE Manjoine, M.J. and Tome, R.E., "Proposed Design Criteria for 0000-0053-2954,      High Cycle Fatigue of Austenitic Stainless Steels,"
32 FDDR RMCN08404 "Ring and Skirt Assembly", dated 04/05/06.  (Specifications and drawings for repair to 220 area.) 33 GENE 0000-0053-0605-1 QC2 Steam Dryer - Base Ring Diametral Distortion (April 2006 re-assessment of ovality issue) 34 GENE 0000-0053-0606 QC2 Steam Dryer Repair Crevice Assessment  (Discussion of acceptability of skirt plate repairs using backing rings). 35 GENE 0000-0043-3105-01-P QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis Based on Measured EPU Conditions (July 2005) 36 GE-NE-0000-0053-2456-P QC U-2 Replacement Steam Dryer Analysis Detailed Stress Analysis of Dryer Lifting (April 2006) 37 AR 330331 RCA:  "QC2 Replacement Steam Dryer Impact on Fuel Analysis Results" 38  AR 435858 RCA:  "Electromatic Reli ef Valve Solenoid Actuator Failures due to failure to correct the source of the MSL vibrations -"  39 EC 360876 Review of Q1M19 Critical Steam Dryer Inspection Findings
Rev. 1 - RCA Ref. 40 (above)
 
International Conference on Advances in Life Prediction Methods, ASME, 1983, pp. 51-57.
ATT. Page 7 Ref. # Document Reference Number Title / Description 40 GENE 0000-0053-2954, Revision 1 Request for Additional Informati on: QC U-2 Dryer Inspection, Start-up & Power Ascension Plan - RAI 9 (b):  
ATT. Page 7
 
: Comparison of QC 2 Replacement Steam Dryer Pressure Sensor Data with Q2R18 Dryer Damage.
Discussion of the corresponding redu ction in the fatigue stress limits in the Dryer Skirt Crack.  
Reason For Evaluation / Scope:
 
Note: The references in this attachment refer to the items listed on the final page of this attachment, not the RCA Report references listed in Att. 3 Quad Cities Unit 2 (Q2) new steam dryer was installed in May 2005 under EC 351168 (Ref. 1). During installation of the new steam dryer, AR 334348 (Ref. 2) identified that the new steam dryer would not sit in the dryer guides properly. The dryer was repaired and the skirt base plate deflection was documented in GE Traveler (Ref. 3). The skirt base plate deflection at the 1400 AZ location is 3/4, at 2200 AZ location: 5/8, and at 3200 location: 5/16. At the 400 AZ location, no plastic deformation of the skirt base plate was noted. At 1400 AZ, the skirt base plate cutout plastically deformed 3/4 downward with visible inside diameter (ID) deformation and skirt panel with dimple at top of gusset. At 2200 AZ, the skirt base plate was deformed 5/8 downward with visible ID deformation and no evidence of dimpling. At 3200 AZ, the skirt base plate was deformed 5/16 downward with imperceptible plastic ID deformation Q2 steam dryer is instrumented with strain gages, pressure sensors, and accelerometers.
41 Ref. 3 used in GENE 0000-0053-2954, Rev. 1 - RCA Ref. 40 (above) Manjoine, M.J. and Tome, R.E., "Proposed Design Criteria for High Cycle Fatigue of Austenitic Stainless Steels," International Conference on Advances in Life Prediction Methods, ASME, 1983, pp. 51-57.  
GE Specification 26A6395 (Ref. 4), sheets 15, 16, 17, and 18 provides the sensor locations with respect to the Dryer orientation in the reactor vessel and its relative elevations. During unit start up testing to full power, AR 347867 (Ref. 5) identified that various strain gages and accelerometers were failing. After completion of the testing, Q2 ran at full power for > 200 days before coming down for a planned refueling outage (Q2R18).
 
Further, inspection of the steam dryer in Q2R18 indicated damage to the dryer skirt (AR 472321) (Ref. 6) and dryer lifting lugs rotated (AR 471848) (Ref. 7). The #7 skirt panel and base plate at cutout cracked after ~200 days of EPU operation. At 25 Hz, the skirt base plate and the skirt panel #7 have undergone 4.3e08 cycles Purpose of this evaluation is to a) review Q2 start up test data and compare it with the damage seen on the steam dryer skirt at locations close to the main steam lines (MSL) and b) to see whether the as-built/as-installed dryer with known damage to the skirt base plate could affect the pressure distribution in the steam space external to the dryer and affect the main steam line frequency patterns at the full load operation of the unit.
ATT. Page 8 Attachment 4: Comparison of QC 2 Replacement Steam Dryer Pressure Sensor Data with Q2R18 Dryer Damage
. Reason For Evaluation / Scope:
Note: The references in this attachment refer to the items listed on the final page of this attachment, not the RCA Report references listed in Att. 3
 
Quad Cities Unit 2 (Q2) new steam dryer was installed in May 2005 under EC 351168 (Ref. 1). During installation of the new steam dryer, AR 334348 (Ref. 2) identified that the new steam dryer would not sit in the drye r guides properly. The dryer was repaired and the skirt base plate deflection was documented in GE Traveler (Ref. 3). The skirt base plate deflection at the 140 0 AZ location is 3/4", at 220 0 AZ location: 5/8", and at 320 0 location: 5/16". At the 40 0 AZ location, no plastic deformati on of the skirt base plate was noted. At 140 0 AZ, the skirt base plate cutout plastically deformed 3/4" downward with visible inside diameter (ID) deformation and skirt panel with dimple at top of gusset. At 220 0 AZ, the skirt base plate was deformed 5/8" downward with visible ID deformation and no evidence of dimpling. At 320 0 AZ, the skirt base plate was deformed 5/16" downward with imperceptible plastic ID deformation  
 
Q2 steam dryer is instrumented with strain gages, pressure sensors, and accelerometers.
GE Specification 26A6395 (Ref. 4), sheet s 15, 16, 17, and 18 provides the sensor locations with respect to the Dryer orientation in the reactor vessel and its relative elevations. During unit start up testing to full power, AR 34 7867 (Ref. 5) identified that various strain gages and accelerometers were failing. After completion of the testing, Q2 ran at full power for > 200 days before coming down for a planned refueling outage (Q2R18).
 
Further, inspection of the steam dryer in Q2R18 indicated damage to the dryer skirt (AR 472321) (Ref. 6) and dryer lifting lugs rotated (AR 471848) (Ref. 7). The #7 skirt panel and base plate at cutout cr acked after ~200 days of EPU operation. At 25 Hz, the skirt base plate and the skirt panel #7 have undergone 4.3e08 cycles  
 
Purpose of this evaluation is to a) review Q2 start up test data and compare it with the damage seen on the steam dryer skirt at locations close to the main steam lines (MSL) and b) to see whether the as-built/as-installed dryer with known damage to the skirt base plate could affect the pressure distribution in the steam space external to the dryer and affect the main steam line frequency patterns at the fu ll load operation of the unit.
Detailed Evaluation:
Detailed Evaluation:
The new steam dryer orientation was taken from reference 4, sheet 17. Drawing M-3121 (Ref. 8) identifies main steam line nozzle orie ntation. It should be noted that "A" MS nozzle at 70 0 is closest to 40 0 dryer skirt base plate cutout. Similarly, "B" MS nozzle at 110 0 is closest to 140 0 dryer skirt base plate cutout; "C" MS nozzle at 250 0 is closest to 220 0 dryer skirt base plate cutout; and "D" MS nozzle at 290 0 is closest to 320 0 dryer skirt base plate cutout.
The new steam dryer orientation was taken from reference 4, sheet 17. Drawing M-3121 (Ref. 8) identifies main steam line nozzle orientation. It should be noted that A MS nozzle at 700 is closest to 400 dryer skirt base plate cutout. Similarly, B MS nozzle at 1100 is closest to 1400 dryer skirt base plate cutout; C MS nozzle at 2500 is closest to 2200 dryer skirt base plate cutout; and D MS nozzle at 2900 is closest to 3200 dryer skirt base plate cutout.
ATT. Page 9  Following Table shows the pressure sensors located external to the steam dryer, MSL locations, and other pertinent data. Also, Document Number AM-2005-012 (Ref. 9) shows actual pressure data taken from Quad Cities Unit 2 start up testing. This pressure
ATT. Page 8
 
data is used in developing the overall evaluation.
 
*Q2 dryer pressure sensor locations: P3 A hood, opposite "B" MS nozzle. P22, P24, & P25 skirt below "B" MS nozzle. P12 A hood, opposite A MS nozzle. P20 F hood, opposite 'C" MS nozzle. P21 F hood, opposite D MS nozzle. P15 & P17, hood Closure Plate- B & C hoods.
TABLE  No.        1 Main Steam Line (Ref. 8) A A B B C D 2 MSL Azimuth 70 0 70 0 110 0 110 0 220 0 290 0 3 Dryer Skirt Base Plate Cutout Location 40 0 40 0 140 0 140 0 220 0 320 0 4 Initial Skirt Base Plate Damage  None None 3/4 Inch 3/4 Inch 5/8 Inch 5/16 Inch 5 External Pressure Sensors on Dryer P12 N/A P3 N/A P20 P21 6 External Pressure Sensors on Dryer Skirt above Water


Line N/A P25 N/A P22 N/A N/A 7 Min. Pressure, psi (Ref. 9) -2.069 -1.270 -1.887 -1.379 -1.613 -2.261 8 Max. Pressure, psi (Ref. 9) 1.907 1.166 1.817 1.243 1.588 2.099 9 Pressure, psi 3.976 2.436 3.704 2.622 3.201 4.360 10 RMS Pressure Measured, psi (Ref. 9) 0.69 0.344 0.631 0.422 0.499 0.883 11 ERV(s) on MSL   2-0203-3B & 2-0203-3E  2-0203-3C 2-0203-3D 12 ARs on ERV None 435838 435838 430555 and 435838   Conclusions/Recommendations:
Following Table shows the pressure sensors located external to the steam dryer, MSL locations, and other pertinent data. Also, Document Number AM-2005-012 (Ref. 9) shows actual pressure data taken from Quad Cities Unit 2 start up testing. This pressure data is used in developing the overall evaluation.
a) Review of reference 4 shows pressure sensor locations on the dryer from higher to lower elevation in the following order: P1, P 2, P3, P22, and P24. Further review of this reference shows that the pressure sensors P3, P6, P9, P12, P15, and P17 are located 65" below the top of Bank "A". Review of the pressure data from reference 9 for these sensors indicate that pressure reduces when moving downward and when moving away from steam nozzles. Pressure at 140 0 location (P3) is lowe r than pressure at 70 0 or 290 0 ATT. Page 10 locations (P12 and PP21). Skirt pressures are lower than hood pressures as seen from pressure sensor data of P22, P25, P3, and P12. Steam pressure measured at the skirt (P25 and P22) is lower by order of two when compared with the pressures measured at the hood (P12 and P3). Further, the Table shows that steam pressure will be highest for the "D" MSL nozzle, then "A", "B" and the lowest steam pressure will be at "C" MSL nozzle. (i.e., Pressure loads closer to "D" & "A" steam nozzles are greater than the "B" & "C" steam nozzles). 
*Q2 dryer pressure sensor locations:
* P3 A hood, opposite B MS nozzle.
* P22, P24, & P25 skirt below B MS nozzle.
* P12 A hood, opposite A MS nozzle.
* P20 F hood, opposite C MS nozzle.
* P21 F hood, opposite D MS nozzle.
* P15 & P17, hood Closure Plate- B & C hoods.
TABLE No.
1    Main Steam Line (Ref. 8)      A        A          B          B          C              D 2    MSL Azimuth                  700      700        1100        1100        2200            2900 3    Dryer Skirt Base Plate        400      400        1400        1400        2200            3200 Cutout Location 4    Initial Skirt Base Plate    None    None      3/4 Inch      3/4 Inch    5/8 Inch        5/16 Inch Damage 5    External Pressure Sensors    P12      N/A         P3        N/A          P20            P21 on Dryer 6    External Pressure Sensors    N/A      P25         N/A       P22         N/A             N/A on Dryer Skirt above Water Line 7   Min. Pressure, psi         -2.069   -1.270     -1.887     -1.379     -1.613         -2.261 (Ref. 9) 8   Max. Pressure, psi           1.907   1.166       1.817     1.243       1.588           2.099 (Ref. 9) 9     Pressure, psi             3.976   2.436       3.704     2.622       3.201           4.360 10   RMS Pressure Measured,       0.69     0.344       0.631     0.422       0.499           0.883 psi (Ref. 9) 11   ERV(s) on MSL                                 2-0203-3B &             2-0203-3C      2-0203-3D 2-0203-3E 12   ARs on ERV                   None               435838                 435838         430555 and 435838 Conclusions/Recommendations:
a) Review of reference 4 shows pressure sensor locations on the dryer from higher to lower elevation in the following order: P1, P2, P3, P22, and P24. Further review of this reference shows that the pressure sensors P3, P6, P9, P12, P15, and P17 are located 65 below the top of Bank A. Review of the pressure data from reference 9 for these sensors indicate that pressure reduces when moving downward and when moving away from steam nozzles. Pressure at 1400 location (P3) is lower than pressure at 700 or 2900 ATT. Page 9


b) Based on the pressure data, it can be concluded that alt hough the dryer skirt base plate at 320 0 AZ has a 5/16" bend and the highest meas ured pressure (P21 = 4.63 psi), no crack was found. However, at 140 0 AZ, the dryer skirt base pl ate has highest bend (3/4") and lower measured pressure (P3 = 3.704 psi), yet a large crack in the skirt plate # 7 was noted. Therefore, it can be concluded that pressure oscillations al one could not be the primary cause of the crack ini tiation and/or propagation.  
locations (P12 and PP21). Skirt pressures are lower than hood pressures as seen from pressure sensor data of P22, P25, P3, and P12. Steam pressure measured at the skirt (P25 and P22) is lower by order of two when compared with the pressures measured at the hood (P12 and P3). Further, the Table shows that steam pressure will be highest for the D MSL nozzle, then A, B and the lowest steam pressure will be at C MSL nozzle. (i.e., Pressure loads closer to D & A steam nozzles are greater than the B &
 
C steam nozzles).
Further, review of Quad Cities Unit 2 Electromatic Relief Valve (ERV) ARs indicate that ERV 2-0203-3D on "D" MSL has seen more damage than 2-0203-3B and 2-0203-3E on "B" MSL and 2-0203-3C on "C" MSL. However, ERVs on "B" and "C" MSLs also have seen some failures. This evaluation confirms the conclusion reached in Report AM-2005-014 (Ref. 10) which states that "Tables 1 and 2 seem to provide reasonable results in that the normalized flow through Main Steam Lines "A" and "D" are higher than "B" and "C" for both units. This is expected since the "A" and "D" Lines are the shorter Main Steam  
b) Based on the pressure data, it can be concluded that although the dryer skirt base plate at 3200 AZ has a 5/16 bend and the highest measured pressure (P21 = 4.63 psi), no crack was found. However, at 1400 AZ, the dryer skirt base plate has highest bend (3/4) and lower measured pressure (P3 = 3.704 psi), yet a large crack in the skirt plate # 7 was noted. Therefore, it can be concluded that pressure oscillations alone could not be the primary cause of the crack initiation and/or propagation.
 
Further, review of Quad Cities Unit 2 Electromatic Relief Valve (ERV) ARs indicate that ERV 2-0203-3D on D MSL has seen more damage than 2-0203-3B and 2-0203-3E on B MSL and 2-0203-3C on C MSL. However, ERVs on B and C MSLs also have seen some failures. This evaluation confirms the conclusion reached in Report AM-2005-014 (Ref. 10) which states that Tables 1 and 2 seem to provide reasonable results in that the normalized flow through Main Steam Lines A and D are higher than B and C for both units. This is expected since the A and D Lines are the shorter Main Steam Lines.
Lines."     


==References:==
==References:==
: 1) EC 351168, Rev. 2: Unit 2 Steam Dryer Replacement.
: 1) EC 351168, Rev. 2: Unit 2 Steam Dryer Replacement.
: 2) AR 334348: PSU - Steam Dryer would not set all the way down. 3) GE Traveler, Project KCZKU, Trav eler No. KCZKU-Base Ring Deflection. 4) GENE Design Specification 26A6395, Rev. 2: Dryer Vibration Instrumentation 5) AR 347867: New steam Dryer Strain Gages/Accelerometers are failing. 6) AR 472321: PSU Q2R18 Crack in the U2 Steam Dryer Skirt. 7) AR 471848: PSU Q2R18 U-2 Steam Dryer Lifting Lugs Rotated. 8) QC Drawing M-3121, Rev F: In-service Inspection Isometric Reactor Vessel 9) Document Number: AM-2005-012, Rev 0 An Assessment of the Uncertainty in the Application of the Modified 930 MWe Acoustic Circuit Model Predictions For the Replacement Quad Cities Units 1 and 2 Steam Dryers. 10) Report AM-2005-014, Rev. 0, dated July 20, 2005: Quad Cities Unit 2 New Steam Dryer Outage Startup Test Report.
: 2) AR 334348: PSU - Steam Dryer would not set all the way down.
Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 11 
: 3) GE Traveler, Project KCZKU, Traveler No. KCZKU-Base Ring Deflection.
 
: 4) GENE Design Specification 26A6395, Rev. 2: Dryer Vibration Instrumentation
Event 1. Crack/deformation of Dryer Skirt Ring near 140 Azimuth  - INR Q2R18-IVVI-06-02 Design flaw Operating conditions caused mechanical damage  Fabrication errors or material deficiency Damage during installation activities PROBLEM STATEMENT:FAILURE MODE 1 FAILURE MODE 2 FAILURE MODE 4 FAILURE MODE 3  Operating conditions (chemistry or flow pattern) FAILURE MODE 5 Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 12  Failure Mode No. 1  Description  Design Flaw Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A 
: 5) AR 347867: New steam Dryer Strain Gages/Accelerometers are failing.
 
: 6) AR 472321: PSU Q2R18 Crack in the U2 Steam Dryer Skirt.
Finite element model error allowed unacceptable stress level to be accepted RIGOR (A, B, C, D, N/A)  D
: 7) AR 471848: PSU Q2R18 U-2 Steam Dryer Lifting Lugs Rotated.
 
: 8) QC Drawing M-3121, Rev F: In-service Inspection Isometric Reactor Vessel
Validate model IAW GE method requirements
: 9) Document Number: AM-2005-012, Rev 0 An Assessment of the Uncertainty in the Application of the Modified 930 MWe Acoustic Circuit Model Predictions For the Replacement Quad Cities Units 1 and 2 Steam Dryers.
 
: 10) Report AM-2005-014, Rev. 0, dated July 20, 2005: Quad Cities Unit 2 New Steam Dryer Outage Startup Test Report.
Independent review or model output
ATT. Page 10
 
Model valid
 
Review confirms
: 1) Validated
: 2) Validated
 
GE RCA -
complete  Rich Hall -
complete B  Incorrect tolerances to allow
 
for:  1) fit-up
: 2) heat-up/operational movement  RIGOR (A, B, C, D, N/A)  D
: 1) Determine the role of Design in the known impact of new dryer with RPV lugs, and separator guide pins. Structural analysis and metallurgical testing to determine if this initiated crack.
: 2) Review for evidence of rubbing of components due to expansion or operational forces.
: 1) Impact had
 
role in crack
 
initiation.
: 2)  No evidence.
: 1) Confirmed as
 
a CF.
: 2) No evidence.
 
RCA - complete
 
RCA - complete
 
Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 13  Failure Mode No. 1  Description  Design Flaw Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual C 
 
Inadequate load definition caused localized high stress during design operating conditions RIGOR (A, B, C, D, N/A)  D
 
Review of model for design margin preventing plastic deformation 
 
No plastic
 
deformation predicted
 
Confirmed
 
GE RCA -
complete  D 
 
FDDR RMCN 06243 incorrectly allowed use of the machined ring slot with strength reduced more than
 
assumed  RIGOR (A, B, C, D, N/A)  D
 
Confirm conclusions of FDDR RMCN 06243 that amount of metal removed still leaves adequate strength per design requirements including
 
dynamic loads a) How did the load redistribute b) What material impacts when grinding (GE materials, what impact fatigue life for comp that exceeded 0.2% plastic strain)
Note:  Unless metallurgical analysis specifies the
 
presence of IGSSC, grinding and machining are
 
not a CF. 


Material strength adequate   
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 PROBLEM STATEMENT:
Event 1. Crack/deformation of Dryer Skirt Ring near 140&deg; Azimuth - INR Q2R18-IVVI-06-02 FAILURE          FAILURE                    FAILURE                    FAILURE          FAILURE MODE 1          MODE 2                    MODE 3                    MODE 4            MODE 5 Operating conditions                Fabrication          Damage during          Operating Design flaw    caused                errors or material          installation        conditions mechanical                deficiency                activities      (chemistry or damage                                                              flow pattern)
ATT. Page 11


Confirmed as not an initiating event.   
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 1            Description Design Flaw Results                    Owner
                                                                                      *Expected results are based on system        Status operation as designed, not as failed Cause(s)                          Validation/Action Steps                    Expected                  Actual RIGOR (A, B, C, D, N/A) D Finite element model error    Validate model IAW GE method requirements          Model valid            1) Validated    GE RCA -
allowed unacceptable stress                                                                                                complete A level to be accepted            Independent review or model output                  Review confirms        2) Validated Rich Hall -
complete RIGOR (A, B, C, D, N/A) D Incorrect tolerances to allow for:
: 1) fit-up                1) Determine the role of Design in the known        1) Impact had          1) Confirmed as RCA - complete impact of new dryer with RPV lugs, and separator    role in crack          a CF.
B
: 2) heat-up/operational    guide pins. Structural analysis and metallurgical   initiation.
movement              testing to determine if this initiated crack.
: 2) Review for evidence of rubbing of components    2) No evidence.        2) No evidence. RCA - complete due to expansion or operational forces.
ATT. Page  12


GE RCA - complete
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 1            Description Design Flaw Results                    Owner
                                                                                    *Expected results are based on system        Status operation as designed, not as failed Cause(s)                            Validation/Action Steps                  Expected                  Actual RIGOR (A, B, C, D, N/A) D Inadequate load definition    Review of model for design margin preventing      No plastic              Confirmed        GE RCA -
C caused localized high stress    plastic deformation                              deformation                              complete during design operating                                                          predicted conditions RIGOR (A, B, C, D, N/A) D FDDR RMCN 06243                Confirm conclusions of FDDR RMCN 06243 that      Material strength      Confirmed as      GE RCA -
incorrectly allowed use of    amount of metal removed still leaves adequate    adequate                not an initiating complete the machined ring slot with    strength per design requirements including                                event.
strength reduced more than    dynamic loads assumed                            a) How did the load redistribute b) What material impacts when grinding (GE D                                          materials, what impact fatigue life for comp that exceeded 0.2% plastic strain)
Note: Unless metallurgical analysis specifies the presence of IGSSC, grinding and machining are not a CF.
ATT. Page 13


Att. 5 - Event 1: Failure Mode Tree   Ref: MA-AA-716-004 Att.2 ATT. Page 14  Failure Mode No. 2  
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 2        


== Description:==
== Description:==
Operating conditions (mechanical)
Operating conditions (mechanical)
Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A 
Results                   Owner
 
                                                                                      *Expected results are based on system       Status operation as designed, not as failed Cause(s)                         Validation/Action Steps                     Expected                 Actual RIGOR (A, B, C, D, N/A) D Low quality steam output at Confirm mechanical load from moisture carry-         Adequate                No moisture    RCA screened as A
Low quality steam output at the steam separator causes high moisture momentum load to dryer RIGOR (A, B, C, D, N/A)  D
the steam separator causes  over is less than the design limit for dryer         margin exists          carryover      low probability.
 
high moisture momentum      components including the cyclic effect of 0.3 Hz                             concerns load to dryer                core power cycles.                                                           identified. Closed RIGOR (A, B, C, D, N/A) D Transient event              Review cycle history curve for SRV or BPV           No blowdown or          Review of power RCA screened as ADS/TG blowdown and          transients and confirm that transient loads do not   transient loads in      history did not low probability.
Confirm mechanical load from moisture carry-over is less than the design limit for dryer components including the cyclic effect of 0.3 Hz core power cycles.  
rapid pressure change or    exceed internal load limit and dryer lift limit     excess of limits        identify any B
 
dryer overload                                                                                            transients of concern.        Closed Single MSIV closure at      Review cycle history curve for asymmetric MSL       Steady-state or power causing an            flows or higher single MSL flow noise               transient asymmetric load                                                                  asymmetrics insignificant ATT. Page 14
Adequate margin exists
 
No moisture
 
carryover concerns identified.
 
RCA screened as
 
low probability.
Closed B 
 
Transient event ADS/TG blowdown and rapid pressure change or dryer overload
 
Single MSIV closure at
 
power causing an asymmetric load RIGOR (A, B, C, D, N/A) D
 
Review cycle history curve for SRV or BPV transients and confirm that transient loads do not exceed internal load limit and dryer lift limit  
 
Review cycle history curve for asymmetric MSL flows or higher single MSL flow noise  
 
No blowdown or transient loads in excess of limits
 
Steady-state or
 
transient asymmetrics insignificant  
 
Review of power history did not identify any transients of
 
concern. 
 
RCA screened as
 
low probability.
 
Closed
 
Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 15  Failure Mode No. 2  Description  Operating conditions (mechanical)
Refer to Attachment 4 for examples of risk and rigor determination for steps below Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual C 
 
Cyclic power loads induce high cycle fatigue MSL resonance
 
RR bistable flow power
 
swings cause cycle dryer load  RIGOR (A, B, C, D, N/A)  D
 
Evaluate MSL flow swings causing cyclic loading
 
of total dryer dP to induce fatigue 
 
Power changes from sitting with RR bistable flow
 
Fatigue load has
 
large margin
 
Fatigue load has
 
large margin
 
Closed
 
RCA screened as
 
low probability based on factors including evaluation in 
 
Att. 8
 
Closed  D Power/Flow Anomaly
 
High subcooling causes low core exit quality
 
High Flow Control Line (FCL) causes high core dP RIGOR (A, B, C, D, N/A)  D
 
Compare core average exit quality (CAEQ) to
 
previous cycles (moisture carryover)
Compare FCL for cycle to previous cycles
 
CAEQ change from previous cycles minimal
 
Closed
 
RCA screened as
 
low probability.
 
Closed
 
Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 16  Failure Mode No. 3  Description  Fabrication error or material deficiencies Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A 
 
Distortion/ovality of Cullen fit-up and weld of base to skirt  RIGOR (A, B, C, D, N/A)  D
: 1. Calculate the loads imposed by fit-up with as-built ovality.  (GE to address this in analysis)
: 2. Determine impact of ovality in reducing clearances and influencing lift event.
: 1. No loads exceed design
 
limits. 2. Ovality impact of reduced clearance is a


CF.   
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 2          Description Operating conditions (mechanical)
Refer to Attachment 4 for examples of risk                        Results                    Owner and rigor determination for steps below        *Expected results are based on system        Status operation as designed, not as failed Cause(s)                          Validation/Action Steps                  Expected                  Actual RIGOR (A, B, C, D, N/A) D RCA screened as Cyclic power loads induce    Evaluate MSL flow swings causing cyclic loading    Fatigue load has        Closed        low probability high cycle fatigue          of total dryer dP to induce fatigue                large margin                          based on factors including C
MSL resonance                                                                                                        evaluation in Power changes from sitting with RR bistable flow   Fatigue load has                      Att. 8 RR bistable flow power                                                          large margin swings cause cycle dryer load                                                                                                                  Closed RIGOR (A, B, C, D, N/A) D Power/Flow Anomaly          Compare core average exit quality (CAEQ) to        CAEQ change            Closed        RCA screened as previous cycles (moisture carryover)              from previous                        low probability.
High subcooling causes low                                                      cycles minimal D
core exit quality            Compare FCL for cycle to previous cycles Closed High Flow Control Line (FCL) causes high core dP ATT. Page 15


Confirmed as not a CF Confirmed as a
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 3              Description Fabrication error or material deficiencies Results                      Owner
 
                                                                                          *Expected results are based on system          Status operation as designed, not as failed Cause(s)                            Validation/Action Steps                      Expected                  Actual RIGOR (A, B, C, D, N/A) D
CF
: 1. GE RCA -
: 1. GE RCA -
complete
Distortion/ovality of Cullen    1. Calculate the loads imposed by fit-up with as-    1. No loads            Confirmed as not  complete fit-up and weld of base to          built ovality. (GE to address this in analysis)  exceed design          a CF A skirt                                                                                  limits.
: 2. RCA team -
: 2. Determine impact of ovality in reducing            2. Ovality impact      Confirmed as a    2. RCA team -
complete B Incorrect or substandard
clearances and influencing lift event.            of reduced              CF                complete clearance is a CF.
 
RIGOR (A, B, C, D, N/A) D Incorrect or substandard        Confirm that materials match the design requests     1. Records              1. Confirmed      GE analysis -
materials were used or supplier errors or process control failures RIGOR (A, B, C, D, N/A) D
materials were used or          and that sub component supplier                       confirm proper                            complete supplier errors or process      certifications/procurement records                   materials and control failures                                                                      controls B
 
: 2. Metallurgical       2. GE testing analysis                indicates that the confirms no            materials are material                consistent with deficiency.            drawings and CMTRs.
Confirm that materials match the design requests and that sub component supplier  
ATT. Page 16
 
certifications/procurement records
: 1. Records
 
confirm proper
 
materials and controls
: 2. Metallurgical  
 
analysis confirms no material deficiency.
: 1. Confirmed
: 2. GE testing indicates that the  
 
materials are consistent with drawings and  
 
CMTRs.
GE analysis -
complete
 
Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 17  Failure Mode No. 3  Description  Fabrication error or material deficiencies Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual C 
 
Incorrect component fabrication or techniques RIGOR (A, B, C, D, N/A)  D
 
Confirm dryer fabrication records match
 
approved processes
 
No discrepancies identified as CFs.
 
DDR reviews no issues as CFs problems.
 
Summary review
 
completed. RCA screened as low probability.
 
Closed  D    Incorrect fabrication
 
sequence  RIGOR (A, B, C, D, N/A)  D Confirm fabrication sequences did not cause interim overstresses such as unsupported spans, temporary jacking etc.
 
No discrepancies identified as
 
CFs. DDR reviews no issues as CFs
 
problems.


RCA screened as  
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 3            Description Fabrication error or material deficiencies Results                  Owner
                                                                                    *Expected results are based on system      Status operation as designed, not as failed Cause(s)                        Validation/Action Steps                    Expected                  Actual RIGOR (A, B, C, D, N/A) D Incorrect component          Confirm dryer fabrication records match          No                      DDR reviews no Summary review fabrication or techniques    approved processes                                discrepancies          issues as CFs  completed. RCA C                                                                                  identified as          problems.      screened as low CFs.                                  probability.
Closed RIGOR (A, B, C, D, N/A) D Incorrect fabrication        Confirm fabrication sequences did not cause      No                      DDR reviews no RCA screened as D sequence                        interim overstresses such as unsupported spans,  discrepancies          issues as CFs  low probability.
temporary jacking etc.                            identified as          problems.
CFs.
Closed ATT. Page 17


low probability.  
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 4            Description Damage during installation Results                      Owner
                                                                                      *Expected results are based on system          Status operation as designed, not as failed Cause(s)                          Validation/Action Steps                      Expected                  Actual RIGOR (A, B, C, D, N/A) D                                                                    1&2. GE RCA complete Interference/overload          1. Calculate the loads on the skirt ring, gusset,  No overstress          No stresses cause excess load    skirt panel                                        during lifting          determination of  3. Vallecitos during lift                                                                        incident                overstress, but  complete A
: 2. Confirm dryer internal loads with single point                          lifting event Uneven lift loads              hung up and weight distributed does not          No overstress          impacts on        Rich Hall (ITPR) concentrate load localized    overstress skirt ring                              during                  material is most  Complete area at 140&deg; location causes                                                      installation            probable distortion                    3. Metallurgical analysis of dryer materials.      activities              initiating event.
RIGOR (A, B, C, D, N/A) D Rotation/torsion applied      Obtain description of manual rotation used,      Torsion induced        Torsion induced  RCA screened as during installation caused    calculate possible torsion loads                    loads were              loads were        low probability.
localized overstress                                                              minimal                minimal B
Closed ATT. Page 18


Closed Att. 5 - Event 1: Failure Mode Tree   Ref: MA-AA-716-004 Att.2 ATT. Page 18  Failure Mode No. 4 Description Damage during installation Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A   
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 4           Description Damage during installation Results                   Owner
                                                                                    *Expected results are based on system       Status operation as designed, not as failed Cause(s)                         Validation/Action Steps                     Expected                 Actual RIGOR (A, B, C, D, N/A) D Uneven weight distribution    Calculate loads/flex caused by sitting on 2 RPV    No gusset or            Confirmed    GE RCA while sitting on 2 RPV lugs   lugs                                              skirt ring                            complete caused load concentration                                                        overstressed C
exceeding limits              (Note: Considered a lower priority analysis unless other analysis is inconclusive).
RIGOR (A, B, C, D, N/A) D                          Load cell              Not a CF inoperable is not                    Site RCA -
RB Crane load cell visual    Determine impact of inoperable load cell on lift  a CF but                              complete display not working during    event.                                            included in dryer installation.                                                              Other section.
D ATT. Page 19


Interference/overload stresses cause excess load during lift 
Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 5            Description Operating Conditions (chemistry or flow)
Results                  Owner
                                                                                  *Expected results are based on system      Status operation as designed, not as failed Cause(s)                          Validation/Action Steps                  Expected                  Actual RIGOR (A, B, C, D, N/A) D Core design issues, power      Compare core operating conditions to as named  No discrepancy          Closed        RCA screened as distribution increased local  service conditions                              between design                        low probability.
moisture but was damaged                                                      and operation A
by moisture momentum Closed RIGOR (A, B, C, D, N/A) D Steam separator local          Inspect steam separator for blocked flow path  No blocked              Closed        RCA screened as blockage caused uneven                                                        separator tubes                      low probability.
loading (increased flow in B
part, decreased other)
Closed ATT. Page 20


Uneven lift loads concentrate load localized area at 140&deg; location causes distortion RIGOR (A, B, C, D, N/A) D
Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 PROBLEM STATEMENT:
: 1. Calculate the loads on the skirt ring, gusset, skirt panel
Event 2:  Crack was found in adjacent vane  bank end plates (in the E vane  bank near 320&deg; of the Dryer)
: 2. Confirm dryer internal loads with single point "hung up" and weight distributed does not
Ref: IVVI-06-04 FAILURE        FAILURE                FAILURE                  FAILURE      FAILURE MODE 1         MODE 2                  MODE 3                  MODE 4        MODE 5 Installation/
Fabrication    Inadequate                Material              Operational      Removal Defect        Design                  Defect                Conditions  In Overload/
Overstress Condition ATT. Page 21


overstress skirt ring
Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 1                Description Fabrication Defect Results                       Owner
: 3. Metallurgical analysis of dryer materials.
                                                                                                  *Expected results are based on system operation as   Status designed, not as failed Cause(s)                               Validation/Action Steps                         Expected                     Actual RIGOR (A, B, C, D, N/A) D High stress condition or            Inspect failed area visually for location or            No crack                  Potential CF:          GE RCA -
 
stress riser created by             indication of any crack initiation or defect             initiation site or         INR Page 2 last         Complete inappropriate weld or other                                                                  defect identified          picture shows a A fabrication error                                                                                                          location where there is very little weld material and this point appears to be the initiation site for the crack*
No overstress during lifting incident No overstress
 
during installation activities
 
No determination of overstress, but lifting event
 
impacts on material is most
 
probable initiating event.
1&2. GE RCA complete
: 3. Vallecitos complete Rich Hall (ITPR)
 
Complete B
Rotation/torsion applied during installation caused localized overstress RIGOR (A, B, C, D, N/A)  D
 
Obtain description of "manual rotation" used, calculate possible torsion loads
 
Torsion induced
 
loads were
 
minimal Torsion induced
 
loads were
 
minimal RCA screened as
 
low probability.
 
Closed
 
Att. 5 - Event 1: Failure Mode Tree   Ref: MA-AA-716-004 Att.2 ATT. Page 19  Failure Mode No. 4  Description Damage during installation Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual C 
 
Uneven weight distribution while sitting on 2 RPV lugs caused load concentration exceeding limits RIGOR (A, B, C, D, N/A)  D
 
Calculate loads/flex caused by sitting on 2 RPV
 
lugs  (Note:  Considered a lower priority analysis unless other analysis is inconclusive).
 
No gusset or
 
skirt ring overstressed
 
Confirmed 
 
GE RCA complete  D    RB Crane load cell visual display not working during
 
dryer installation.
RIGOR (A, B, C, D, N/A)  D Determine impact of inoperable load cell on lift
 
event.
Load cell inoperable is not a CF but included in
 
"Other" section.
Not a CF  Site RCA - complete Att. 5 - Event 1:  Failure Mode Tree  Ref: MA-AA-716-004 Att.2 ATT. Page 20  Failure Mode No. 5  Description  Operating Conditions (chemistry or flow)
Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A 
 
Core design issues, power distribution increased local moisture but was damaged by moisture momentum RIGOR (A, B, C, D, N/A) D
 
Compare core operating conditions to as named service conditions
 
No discrepancy
 
between design and operation
 
Closed
 
RCA screened as
 
low probability.
 
Closed
 
B    Steam separator local blockage caused uneven loading (increased flow in part, decreased other)
RIGOR (A, B, C, D, N/A)  D Inspect steam separator for blocked flow path
 
No blocked separator tubes
 
Closed
 
RCA screened as
 
low probability.
 
Closed 
 
Att. 6 - Event 2:  Failure Mode Tree  Ref: MA-AA-716-004 Att. 2 ATT. Page 21 
 
Event 2:  Crack was found in adjacent vane bank end plates (in the "E" vane bank near 320of the Dryer) Ref:  IVVI-06-04 Fabrication Defect  Inadequate Design  Material Defect  Operational Conditions PROBLEM STATEMENT: FAILURE MODE 5 Installation/ Removal  In Overload/ Overstress Condition  FAILURE  MODE 4  FAILURE MODE 3  FAILURE MODE 2  FAILURE MODE 1 Att. 6 - Event 2:  Failure Mode Tree  Ref: MA-AA-716-004 Att. 2 ATT. Page 22  Failure Mode No. 1  Description  Fabrication Defect Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A 
 
High stress condition or stress riser created by  
 
inappropriate weld or other
 
fabrication error RIGOR (A, B, C, D, N/A)  D
 
Inspect failed area visu ally for location or indication of any crack initiation or defect  
 
No crack initiation site or defect identified
 
Potential CF:
INR Page 2 last picture shows a  
 
location where there is very little weld material and this  
 
point appears to be the initiation site for the  
 
crack*    
 
GE RCA -
Complete
* Based on these inspection results, it can be concluded that having very little weld metal between the end plates at gusset 19 contributed to the initiation and propagation of the crack in this location. This incomplete weld combined with hood assembly fit-up and weld shrinkage stresses, and the deformation and loading associated with the interferences during dryer removal are the most probable cause of the crack initiation that would then have been driven to its current size by operating vibration loads.
* Based on these inspection results, it can be concluded that having very little weld metal between the end plates at gusset 19 contributed to the initiation and propagation of the crack in this location. This incomplete weld combined with hood assembly fit-up and weld shrinkage stresses, and the deformation and loading associated with the interferences during dryer removal are the most probable cause of the crack initiation that would then have been driven to its current size by operating vibration loads.
Att. 6 - Event 2:  Failure Mode Tree  Ref: MA-AA-716-004 Att. 2 ATT. Page 23    Failure Mode No. 2  Description  Inadequate Design Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A  Crack occurred in area
ATT. Page   22
 
subjected to overstress (Finite Element Analysis


Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 2            Description Inadequate Design Results                          Owner
                                                                                          *Expected results are based on system operation as      Status designed, not as failed Cause(s)                              Validation/Action Steps                      Expected                      Actual Crack occurred in area          RIGOR (A, B, C, D, N/A) D                              Stress is within          Confirmed subjected to overstress                                                                allowable limits                                  GE RCA A (Finite Element Analysis          Stress analysis to identify loading/stresses in area                                                      complete.
incorrect)
incorrect)
RIGOR (A, B, C, D, N/A)  D
Failure Mode No. 3          
 
Stress analysis to identify loading/stresses in area
 
Stress is within allowable limits
 
Confirmed
 
GE RCA complete.
Failure Mode No. 3  


== Description:==
== Description:==
Material Defect Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A
Material Defect Results                           Owner
Defects in plate material
                                                                                          *Expected results are based on system operation as     Status designed, not as failed Cause(s)                             Validation/Action Steps                       Expected                     Actual RIGOR (A, B, C, D, N/A) D Defects in plate material                                                              Failure not due            Closed                  RCA screened as created stress riser or highly  Inspect plate for evidence of fracture initiation     to material                                        low probability.
 
A localized stress                location, fretting or fatigue                         defect Closed ATT. Page 23
created stress riser or highly localized stress RIGOR (A, B, C, D, N/A) D
 
Inspect plate for evidence of fracture initiation  
 
location, fretting or fatigue  
 
Failure not due to material
 
defect  
 
Closed  
 
RCA screened as


low probability.
Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 4          
 
Closed Att. 6 - Event 2: Failure Mode Tree   Ref: MA-AA-716-004 Att. 2 ATT. Page 24    Failure Mode No. 4  


== Description:==
== Description:==
Operational Conditions Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A Operating conditions caused vibrations that exceeded the  
Operational Conditions Results                           Owner
 
                                                                                    *Expected results are based on system operation as     Status designed, not as failed Cause(s)                           Validation/Action Steps                   Expected                     Actual Operating conditions caused     RIGOR (A, B, C, D, N/A) D                        Operating                                          RCA screened as vibrations that exceeded the                                                     conditions were            Closed                  low probability.
design capabilities of the  
A design capabilities of the       Verify appropriate operating conditions were      appropriately vane bank end plate            modeled in analysis                              modeled                                            Closed Failure Mode No. 5            Description Installation/Removal in Overload/Overstress Condition Results                          Owner
 
                                                                                    *Expected results are based on system operation as      Status designed, not as failed Cause(s)                          Validation/Action Steps                    Expected                      Actual Excessive loads were placed    RIGOR (A, B, C, D, N/A) D                        The load was on the vane bank end plates                                                      within the design Analysis                        GE RCA complete A when the Steam Dryer was        Determine the load that was applied to the vane  limits of the vane concludes this is resting on the Steam            bank end plate during the incident.              bank end plate             not a CF.
vane bank end plate RIGOR (A, B, C, D, N/A) D
Separator Guide Rods Excessive loads were placed    RIGOR (A, B, C, D, N/A) D                         The load was              Analysis on the vane bank end plates                                                      within the design concluded this is                GE RCA B when the Steam Dryer was        Determine the load that was applied to the vane  limits of the vane not a CF                        complete stuck on the RPV lugs          bank end plate during the incident.              bank end plate ATT. Page 24


Verify appropriate operating conditions were
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
 
modeled in analysis
 
Operating conditions were
 
appropriately
 
modeled Closed RCA screened as low probability.
 
Closed    Failure Mode No. 5  Description  Installation/Rem oval in Overload/Overstress Condition Results *Expected results are based on system operation as designed, not as failed Owner Status Cause(s) Validation/Action Steps Expected Actual A Excessive loads were placed on the vane bank end plates when the Steam Dryer was resting on the Steam
 
Separator Guide Rods RIGOR (A, B, C, D, N/A)  D
 
Determine the load that was applied to the vane
 
bank end plate during the incident. 
 
The load was within the design limits of the vane
 
bank end plate
 
Analysis concludes this is
 
not a CF.
 
GE RCA complete  B Excessive loads were placed on the vane bank end plates when the Steam Dryer was
 
stuck on the RPV lugs RIGOR (A, B, C, D, N/A)  D
 
Determine the load that was applied to the vane
 
bank end plate during the incident.
The load was within the design limits of the vane
 
bank end plate Analysis concluded this is
 
not a CF GE RCA complete Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 25


==Background:==
==Background:==
During the initial installation of the Quad Cities Unit 2 dryer, the dryer became "hung up" on the dryer lugs. During the initial dryer placement, it was discovered that the dryer base plate interfered with the separator guide rods. As a result, the dryer was removed to allow the base plate to be modified to prevent the interference. During the lift, the dryer base plate became hung up on the dryer lugs. The interference resulted in damage to the dryer lugs a nd local yielding of the dryer base plate.  
During the initial installation of the Quad Cities Unit 2 dryer, the dryer became hung up on the dryer lugs. During the initial dryer placement, it was discovered that the dryer base plate interfered with the separator guide rods. As a result, the dryer was removed to allow the base plate to be modified to prevent the interference.
 
During the lift, the dryer base plate became hung up on the dryer lugs. The interference resulted in damage to the dryer lugs and local yielding of the dryer base plate.
Evaluation: There are four dryer support lugs on the ID of the reactor vessel and four guide slots in the dryer base plate. The guide slots are intended to allow the dryer base plate to move by the dryer support lugs duri ng lowering and lifting. The support lugs and guide slots are located at 40 , 140 , 220 , and 320 azimuths around the ID of the reactor vessel and the OD of the drye r base plate, respectively.  
Evaluation: There are four dryer support lugs on the ID of the reactor vessel and four guide slots in the dryer base plate. The guide slots are intended to allow the dryer base plate to move by the dryer support lugs during lowering and lifting. The support lugs and guide slots are located at 40&deg;, 140&deg;, 220&deg;, and 320&deg; azimuths around the ID of the reactor vessel and the OD of the dryer base plate, respectively.
 
The dryer base plate and the reactor vessel lugs were examined following the incident (Ref. Work Order # 732708-01). The base plate was found deformed (i.e. - bent) downward at the 140&deg;, the 220&deg;, and the 320&deg; locations. The 40&deg; dryer location was not damaged. The base plate near the 140&deg; guide slot location was bent down by 3/4 inch, the 220&deg; was bent down by 5/8 inch, and the 320&deg; was bent down by 5/16 inch. The base plate near the 140&deg; was bent on the right hand side, when looking at the dryer, and the other two locations were bent on the left hand side when looking at the dryer. This is shown schematically in Figure 1.
The dryer base plate and the reactor vessel lugs were examined following the incident (Ref. Work Order # 732708-01). The base plate was found deformed (i.e. - bent) downward at the 140 , the 220 , and the 320 locations. The 40 dryer location was not damaged. The base plate near the 140 guide slot location was bent down by 3/4 inch, the 220 was bent down by 5/8 inch, and the 320 was bent down by 5/16 inch. The base plate near the 140 was bent on the right hand side, when looking at the dryer, and the other two locations were bent on the left hand side when looking at the dryer. This is shown schematically in Figure 1.  
The videotape of the in vessel dryer support lug inspection was reviewed and stills extracted as shown in figures 1 through 12 below. The 40&deg; lug (Figure 3) had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID, even though the dryer base plate at this location was not damaged. The support lug located at 140&deg; (Figure 4) also had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID. The 220&deg; (Figures 5 and 6) and 320&deg; (Figures 7 and 8) support lugs were damaged on the lower left hand corner. The worst deformations were on the 220&deg; and 140&deg; location.
 
The design of the base plate cutouts and the dryer guide rod slot would allow the dryer to rotate and potentially allow the cutout gussets to impact the dryer support lugs. Based on the geometry of the vessel lugs and the base plate cutouts, it does not seem reasonable that the dryer would impact two lugs on the right side and the other two on the left side.
The videotape of the in vessel dryer support lug inspection was reviewed and stills extracted as shown in figures 1 through 12 below. The 40 lug (Figure 3) had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID, even though the dryer base plate at this location was not damaged. The support lug located at 140 (Figure 4) also had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID. The 220 (Figures 5 and 6) and 320 (Figures 7 and 8) support lugs were damaged on the lower left hand corner. The worst deformations were on the 220 and 140 location.
This conclusion would lead to the possibility that there were two different impacts, or events. However, based on discussion with individuals who were present, there was only one impact event. That is, the dryer was not lowered or rotated and then lifted again.
The design of the base plate cutouts and the dryer guide rod slot would allo w the dryer to rotate and potentially allow the cutout gussets to impact the dryer support lugs. Based on the geometry of the vessel lugs and the base plate cutouts, it does not seem reasonable that the dryer would impact two lugs on the right side and the other two on the left side. This conclusion would lead to the possibility that there were two different impacts, or events. However, based on discussion with individuals who were present, there was only one impact event. That is, the dryer was not lowered or rotated and then lifted again. This leads to the possibility of multiple impacts during a single event.  
This leads to the possibility of multiple impacts during a single event.
 
The as-built elevation of the top of the dryer support lugs is excerpted from the reactor vessel as-built drawing (CBI drawing 69-4824) and is provided in Table 1.
The as-built elevation of the top of the dryer support lugs is excerpted from the reactor vessel as-built drawing (CBI drawing 69-4824) and is provided in Table 1.
Att 7:  Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 25
Attachment page 26  Lug Azimuth Location As-Built Elevation 40 616 - 13/16 " 140 617 - 1/32 " 220 616 - 11/16 " 320 616 - 13/16 "
Table 1 Dryer Support Lug As-Built Elevation (Measured from the support skirt)
This drawing indicates that the lowest lug is the 220 lug, and the highest is the 140 lug. This assumes that they are all approximately the same length. The data indicates that the 220 lug is 11/32" (0.344") below the 140 degree lug. Also, the 40 and the 320 lugs are 7/32" (0.219") below the 140 lug. As can be seen in figures 7 through 11, the lugs were also damaged when the dryer was lowered into the reactor vessel. This damage indicates that the combination of dryer support lug as-built location and size combined with the dryer base plate cutout as-built location and size, and the as-built clearances between the dryer guide pins and guide slots, resulted in a lack of clearance and interference between the dryer support lugs and the cutouts when lowering the load. Since a review of all of the as-built locations and sizes and combinations thereof is difficult and yields results that are subject to the stacking of multiple accuracies, it is sufficient t note that the potential for the interference exists based on the evidence of damage to the lugs from lowering the load.


A plausible sequence of events can be established using the evidence of damage to the dryer support lugs and the drye r base plate and the as-built elevations of the bottom of the dryer support lugs. It cannot be established that this is the exact sequence of events, but only that this is a likely scenario that is coincidental with the established facts.
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Since the 220 dryer support lug is the lowest lug, it is presumed that the dryer base plate cutout contacted this lug first. (Note the c ontact point for all of the interferences would be the gusset plate that is located on the either side of the base plate cutout.) Also, since the dryer contacted the left si de of the lug, the dryer is ro tated clockwise when looking down from the crane. The initial impact on this lug is supported by the lower elevation and fact that the damage to the dryer support lug at his location was the worst for all of the support lugs (See figures 3 and 4). It is not necessarily supported by the amount of damage to the dryer base plate.  
Lug Azimuth Location                                As-Built Elevation 40                                        616 - 13/16 140                                        617 - 1/32 220                                        616 - 11/16 320                                        616 - 13/16 Table 1 Dryer Support Lug As-Built Elevation (Measured from the support skirt)
This drawing indicates that the lowest lug is the 220&deg; lug, and the highest is the 140&deg; lug.
This assumes that they are all approximately the same length. The data indicates that the 220&deg; lug is 11/32 (0.344) below the 140 degree lug. Also, the 40&deg; and the 320&deg; lugs are 7/32 (0.219) below the 140&deg; lug.
As can be seen in figures 7 through 11, the lugs were also damaged when the dryer was lowered into the reactor vessel. This damage indicates that the combination of dryer support lug as-built location and size combined with the dryer base plate cutout as-built location and size, and the as-built clearances between the dryer guide pins and guide slots, resulted in a lack of clearance and interference between the dryer support lugs and the cutouts when lowering the load. Since a review of all of the as-built locations and sizes and combinations thereof is difficult and yields results that are subject to the stacking of multiple accuracies, it is sufficient t note that the potential for the interference exists based on the evidence of damage to the lugs from lowering the load.
A plausible sequence of events can be established using the evidence of damage to the dryer support lugs and the dryer base plate and the as-built elevations of the bottom of the dryer support lugs. It cannot be established that this is the exact sequence of events, but only that this is a likely scenario that is coincidental with the established facts.
Since the 220&deg; dryer support lug is the lowest lug, it is presumed that the dryer base plate cutout contacted this lug first. (Note the contact point for all of the interferences would be the gusset plate that is located on the either side of the base plate cutout.) Also, since the dryer contacted the left side of the lug, the dryer is rotated clockwise when looking down from the crane. The initial impact on this lug is supported by the lower elevation and fact that the damage to the dryer support lug at his location was the worst for all of the support lugs (See figures 3 and 4). It is not necessarily supported by the amount of damage to the dryer base plate.
The dryer would continue to be lifted as it yielded both the support lug and the dryer base plate at the 200&deg; location. Once the dryer had been lifted approximately 1/16, the dryer would contact the 320&deg; location at the left hand side of the lug. The dryer also should have impacted the 40&deg; lug on the left hand side, however it did not. This can be explained by reviewing figures 7 and 8.
Attachment page 26


The dryer would continue to be lifted as it yielded both the support l ug and the dryer base plate at the 200 location. Once the dryer had been lifted approximately 1/16", the dryer would contact the 320 location at the left hand side of the lug. The dryer also should have impacted the 40 lug on the left hand side, howe ver it did not. This can be explained by review ing figures 7 and 8.  
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Note that the damage to the 40&deg; lug when lowering the load occurred on the right hand side of the lug. This indicates that when the dryer is positioned such that it passes by all of the lugs, it is closer to the right hand side of the 40&deg; lug. Therefore, the largest clearance between the 40&deg; dryer support lug and the dryer base plate cutout would be on the left hand side of the lug. Then, if the dryer is rotated clockwise, it may not impact the left hand side of the 40&deg; lug since that is the side of the greatest clearance.
Once the dryer base plate contacts the 320&deg; support lug, the load is shared between the base plate locations at 220&deg; and 320&deg;. This would help to limit the amount of base plate deformation at the 220&deg; location. The dryer would continue to lift and possibly rotate such that the 220&deg; to 320&deg; section of the dryer would be lower than the 40&deg; to 140&deg; side.
The dryer released from the 220 and 320&deg; lugs and swung, or tilted, while rotating back counter clockwise. During the tilt or swing, the dryer impacted the support lugs at 40 and 140 degrees. The release mechanism is supported by the edge displacement damage to the 320&deg; lug, which makes it appear that the dryer slid laterally away from the lug, causing material on the lug to move downward (Figures 5 and 6). As stated previously, the dryer, once it was free to swing, impacted the lower right edge of both the 40 and 140&deg; support lugs. The dryer impacted the lower part of the 140 degree support lug and impacted only the edge of the 40 degree lug. The reason the dryer impacted below the 140&deg; support lug is due to the higher elevation of the lug and the tilting of the dryer. The dryer scraped the lower right hand side of the 40&deg; vessel support lug (Figure 1) because that lug is slightly higher than the 140&deg; support lug. That is, the dryer did not wedge under the 40&deg; lug because of the lower elevation versus the 140&deg; lug, but it did hit the edge of the lug, as seen in Figure 1.
Conclusions Based on this evaluation, the following summarizes the interference event that occurred during the initial dryer installation:
: 1. Dryer base plate guide slots impact multiple dryer support lugs during the initial lowering into position.
: 2. Dryer base plate interferes with the separator guide pins and cannot be placed in final position. This causes the dryer to be lifted to facilitate modifications.
: 3. Dryer is rotated clockwise during the lift (slightly, less than 1 inch).
: 4. Dryer base plate guide slot gusset interferes with dryer support lug at the 220&deg; location. This results in a 1/2 high by 3/8 wide damaged area in the dryer support lug and a 5/8 inch downward deflection of the base plate.
: 5. Dryer base plate guide slot gusset interferes with dryer support lug at the 320&deg; location. This results in part of the dryer support lug being sheared off and the dryer base plate deflection of 5/16.
: 6. Dryer tilts noticeably along the 0 and 180&deg; axis, prior to releasing from the lugs.
: 7. Dryer releases, swinging back towards 220 and 320&deg; location.
Attachment page 27


Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 27 Note that the damage to the 40 lug when lowering the load occurred on the right hand side of the lug. This indicates that when th e dryer is positioned such that it passes by all of the lugs, it is closer to the right hand side of the 40 lug. Therefore, the largest clearance between the 40 dryer support lug and the dryer base plate cutout would be on the left hand side of the lug. Then, if the dr yer is rotated clockwise, it may not impact the left hand side of the 40 lug since that is the side of the greatest clearance.
: 8. Dryer rotates and swings into the 140 and 40&deg; lug.
Once the dryer base plate contacts the 320 support lug, the load is shared between the base plate locations at 220 and 320. This would help to limit the amount of base plate deformation at the 220 location. The dryer would conti nue to lift and possibly rotate such that the 220 to 320 section of the dryer would be lower than the 40 to 140 side. The dryer released from the 220 and 320 lugs and swung, or tilte d, while rotating back counter clockwise. During the tilt or swing, the dryer impacted the support lugs at 40 and 140 degrees. The release mechanism is supported by the edge displacement damage to the 320 lug, which makes it appear that the dr yer slid laterally away from the lug, causing material on the lug to move downward (F igures 5 and 6). As stated previously, the dryer, once it was free to swing, impacted the lower right edge of both the 40 and 140 support lugs. The dryer impacted the lo wer part of the 140 degree support lug and impacted only the edge of the 40 degree lug. The reason the dryer impacted below the 140 support lug is due to the higher elevation of the lug and the tilting of the dryer. The dryer scraped the lower right hand side of the 40 vessel support lug (Figure 1) because that lug is slightly higher than the 140 support lug. That is, the dryer did not wedge under the 40 lug because of the lower elevation versus the 140 lug, but it did hit the edge of the lug, as seen in Figure 1.
: 9. Dryer impacts the 140&deg; lug below the right lower edge of the lug.
Conclusions Based on this evaluation, the following summarizes the interference event that occurred during the initial dryer installation: 1. Dryer base plate guide slots impact multiple dryer support lugs during the initial lowering into position. 2. Dryer base plate interferes with the separator guide pins and cannot be placed in final position. This causes the dryer to be lifted to facilitate modifications. 3. Dryer is rotated clockwise during the lift (slightly, less than 1 inch). 4. Dryer base plate guide slot gusset interferes with dryer support lug at the 220 location. This results in a 1/2" high by 3/8" wide damaged area in the dryer support lug and a 5/8 inch downward deflection of the base plate. 5. Dryer base plate guide slot gusset interferes with dryer support lug at the 320 location. This results in part of the dryer support lug being sheared off and the dryer base plate deflection of 5/16". 6. Dryer tilts noticeably along the 0 and 180 axis, prior to releasing from the lugs. 7. Dryer releases, swinging back towards 220 and 320 location.
: 10. This impact results in a sharp crease in the dryer support lug and the formation of an edge on the base plate gusset. The corner of the 140&deg; lug is pushed in and partially shears off.
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
: 11. During the tilt/rotation, the dryer impacts the right bottom corner of the 40&deg; lug, shearing off the corner.
Attachment page 28 8. Dryer rotates and swi ngs into the 140 and 40 lug. 9. Dryer impacts the 140 lug below the right lo wer edge of the lug. 10. This impact results in a sharp crease in the dryer support lug and the formation of an edge on the base plate gusset. The corner of the 140 lug is pushed in and partially shears off. 11. During the tilt/rotation, the dryer impacts the right bottom corner of the 40 lug, shearing off the corner. 12. The dryer lift is completed without further incident.
: 12. The dryer lift is completed without further incident.
Attachment page 28


Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 29    20 o 200 o 140 o 40 o 220 o 320 o 0 o 180 o 90 o 270 o Separator Guide Rod Cutout (2 Locations)
Separator Guide Rod Cutout               0o (2 Locations) 320o                                        20o      40o 5/16 Bend RPV Lug Cutout (4 Locations) 270o                                                                                  90o 220o                o                                  140o 200 180o 5/8 Bend 3/4 Bend Impact on RPV Dryer Support Lug Figure 1 Steam Dryer Plan - Impact Locations Attachment page 29
RPV Lug Cutout (4 Locations)
Figure 1 Steam Dryer Plan - Impact Locations 3/4" Bend 5/8" Bend 5/16" Ben dImpact on RPV Dryer Support Lug


Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 30  Figure 2 General Relationship Between Dryer Cracking (Top), Dryer Guide Slot Cutout at 140 Degrees (Center), and Dryer Support Lug at 140 Degrees (Bottom)
Figure 2 General Relationship Between Dryer Cracking (Top), Dryer Guide Slot Cutout at 140 Degrees (Center), and Dryer Support Lug at 140 Degrees (Bottom)
Att 7:  Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 30
Attachment page 31    Figure 3 Damage to 40 Degree Lug, Lower Right Hand Corner Damaged During Impact Figure 4 Damage To 140 Degree Lug, Lower Right Hand Corner Damaged Due to Major Impact  Lower right hand


corner indicates scraping damage Lower right hand corner damage due to impact o f dryer Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 32  Figure 5 Damage To 220 Degree Lug, Lower left hand Corner Figure 6 Damage To 220 Degree Lug, Lower left hand Corner (View from Bottom)
Lower right hand corner indicates scraping damage Figure 3 Damage to 40 Degree Lug, Lower Right Hand Corner Damaged During Impact Lower right hand corner damage due to impact of dryer Figure 4 Damage To 140 Degree Lug, Lower Right Hand Corner Damaged Due to Major Impact Attachment page 31
Lower left hand corner damage indicates dryer stuck below support lug Same damage as viewed from the bottom of the lug Att 7:  Dryer to Dryer Lug Impact Analysis (Lifting Event)
Attachment page 33  Figure 7 Damage to 320 Degree Lug, Lower Left Hand Corner Figure 8 Damage to 320 Degree Lug, Lower Left Hand Corner (View From Bottom) Damage to lower left hand corner


due to dryer. Note some damage indication is from top to bottom. Same damage as p revious figure, seen from the bottom of the lug.
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Lower left hand corner damage indicates dryer stuck below support lug Figure 5 Damage To 220 Degree Lug, Lower left hand Corner Same damage as viewed from the bottom of the lug Figure 6 Damage To 220 Degree Lug, Lower left hand Corner (View from Bottom)
Attachment page 34    Figure 9 Damage to Right Hand Side of 40 D egree Lug, Due to Base Plate When Lowering Damage to
Attachment page 32


right hand  
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Damage to lower left hand corner due to dryer. Note some damage indication is from top to bottom.
Figure 7 Damage to 320 Degree Lug, Lower Left Hand Corner Same damage as previous figure, seen from the bottom of the lug.
Figure 8 Damage to 320 Degree Lug, Lower Left Hand Corner (View From Bottom)
Attachment page 33


side of lug, too low to  
Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)
Damage to right hand side of lug, too low to be caused by spacer block.
Figure 9 Damage to Right Hand Side of 40 Degree Lug, Due to Base Plate When Lowering Attachment page 34


be caused
Att. 8: Q2R18 INR Resolution Matrix*
Current                                                                  Proposed Resolution IR      INR Number        Rev                              Title                                        (Not Final)                          Resolution Document            EC 471848 Q2R18-IVVI-06-01      0      Steam Dryer Lifting Lugs at 45, 135, 225, &315 Deg Repair Per FDDR RMCN08456                  WO 681384-01, FDDR RMCN08456 Rev B          360356 472321 Q2R18-IVVI-06-02      0      Steam Dryer Skirt at 135 Deg                          Repair Per FDDR RMCN08382              WO 681384-01, FDDR RMCN08382 Rev A          360356 474814 Q2R18-IVVI-06-03      3      Jet Pump 05 (WD-1)                                    JCO - Possibly replace Q2R19          GENE-0000-0052-9152 R0                      360359 473034 Q2R18-IVVI-06-04      1      Steam Dryer SD-BE-V12-2H, SD-BE-V11-2H                Accept As Is                          GENE-0000-0052-9728 R0                      360356 475009 Q2R18-IVVI-06-05      0      Jet Pump 08 (WD-1)                                    JCO - Possibly replace Q2R19          GENE-0000-0052-9152 R0                      360359 473344 Q2R18-IVVI-06-06      0      Steam Dryer Internal Weld SD-BF-V06-2H-ID              Accept As Is w/future inspection / LPA GE-NE-0000-0052-7988-R0                    360356 473619 Q2R18-IVVI-06-07      0      Steam Separator Upper Support Ring Gusset              Accept As Is w/future inspection      GENE-0000-0052-8398-R0                      360359 473615 Q2R18-IVVI-06-08      0      Steam Dryer Internal Weld SD-BD-V06-2H-ID              Accept As Is w/future inspection / LPA GE-NE-0000-0052-7988-R0                    360356 473622 Q2R18-IVVI-06-09      1      Steam Separator Shroud Head Bolt 14 and 35            Rotate and perform VT-3                Video files 481701, 481101, 481301, 481401  360359 473626 Q2R18-IVVI-06-10      0      Steam Dryer Internal Weld SD-BB-V04-2H-ID              Accept As Is w/future inspection      GE-NE-0000-0052-7988-R0                    360356 473923 Q2R18-IVVI-06-11      1      Steam Dryer Internal Debris                            Accept As Is w/future inspection / LPA Lost Parts Analysis EC 360467              360356 473871 Q2R18-IVVI-06-12      0      Steam Dryer Internal Area (Separator Guide Cutout) Increase clearance FDDR RMCN088242        WO 681384-01, FDDR RMCN08242 Rev A          360356 473839 Q2R18-IVVI-06-13      0      Separator Lower Support Ring Gusset                    Accept As Is w/future inspection      GENE-0000-0052-8398-R0                      360359 474491 Q2R18-IVVI-06-14      0      Jet Pump 10 Wedge Assembly                            Accept As Is w/future inspection      GENE-0000-0052-9152 R0                      360359 474070 Q2R18-IVVI-06-15      0      Jet Pump 07 Wedge Assembly                            Replace swing gate as planned          WO 823272-01                                360359 473844 Q2R18-IVVI-06-16      0      Feedwater Sparger End Bracket                          Planned Tack Weld per FDI 0194        GE-NE-0000-0052-8396-R0                    360359 474064 Q2R18-IVVI-06-17      0      Shroud Repair Yoke at 290 Degrees                      Accept As Is - Installed condition    GE-NE-0000-0052-8402-R0                    360359 474485 Q2R18-IVVI-06-18      0      Dryer General Visual (220 to 320 Degrees)              NRI - No action required              IR 474497 comments                          360356 474497 Q2R18-IVVI-06-19      0      Feedwater Sparger 13&16 Degree End Bracket & Pin Planned Tack Weld per FDI 0194              GE-NE-0000-0052-8396-R0                    360359 474501 Q2R18-IVVI-06-20      0      Steam Dryer Skirt Baseplate at 220 Degrees            Repair Per FDDR RMCN08242              WO 681384-01, FDDR RMCN08404 Rev A          360356 475003 Q2R18-IVVI-06-21      0      Steam Dryer WSL @ 220 Degrees                          No Action Required - unchanged        IR 475003 comments                          360356 475328 Q2R18-IVVI-06-22      0      CS Lower Elbow to Shroud Pipe 290 Degree Azimuth Inspect next RFO                            INR Exelon Level III review                360359 474514 Q2R18-IVVI-06-23      0      Steam Dryer Base Plate Distortion at 320 Degrees No change- Accept As Is                      EC 360356                                  360356 474517 Q2R18-IVVI-06-24      0      Steam Dryer Surface Anomalies at SD-SKT-V11-ID NRI - No action required                      IR 474517 comments                          360356 474977 Q2R18-IVVI-06-25      0      Shroud Head Flange Ring Segment (EDM Hole)            Accept As Is - Previously eval'd      GENE-771-110-0595 R0                        360359 475862 Q2R18-IVVI-06-26      0      Core Support Flange Ring OD                            Accept As Is w/future inspection      GENE-771-110-0595 (May 1995)                360359 475332 Q2R18-IVVI-06-27      0      Shroud Head Flange Ring OD                            Accept As Is                          GENE-0000-0053-0964-R1                      360359 475339 Q2R18-IVVI-06-28      1      Steam Dryer WSLs @ 40, 140 and 320 Degrees            No Action Required - unchanged        IR 475339 comments                          360356 475369 Q2R18-IVVI-06-29      0      Steam Dryer Indication, SD-LB-03-W1 OD @ 220 DegRepair per FDDR RMCN08435                    WO 681384-01, FDDR RMCN08435 Rev A          360356 476654 Q2R18-IVVI-06-30      0      RPV Jet Pump Annulus FME                              Remove FME                            Lost Parts Analysis EC 360467              360359 476657 Q2R18-IVVI-06-31      1      Steam Dryer Exit Plenum Perforated Plate              Accept As Is                          GENE-0000-0053-0964-R0                      360356 477326 Q2R18-IVVI-06-32      0      CS Sparger S3c Drain (two plugs missing tack welds) Accept As Is                              GENE-0000-0053-0964-R0                      360359 N/A  Q2R18-IVVI-06-33      0      Tie Rod Loose and Missing Nuts (As designed)          NRI - No action required              INR - Future reference only. Mention in EC. 360359 476540 None - IR only                SHB #9 suspect based on UT criteria                    Accept As Is w/future inspection      IR, GE Letter DRF B13-01903-8              360359
* The highlighted items are specifically included in the scope of RCR 472321 Attachment page 35


by spacer block.
Att. 9: CAs to Address Programmatic/ Organizational Issues A. CAs from ERV RCA (Ref. 38) aligned with Q2R18 Steam Dryer RCA CF. 2
Att. 8:  Q2R18 INR Resolution Matrix*IRINR Number Current RevTitle Proposed Resolution(Not Final)Resolution DocumentEC471848Q2R18-IVVI-06-010Steam Dryer Lifting Lugs at 45, 135, 225, &315 DegRepair Per FDDR RMCN08456WO 681384-01, FDDR RMCN08456 Rev B 360356472321Q2R18-IVVI-06-020Steam Dryer Skirt at 135 DegRepair Per FDDR RMCN08382WO 681384-01, FDDR RMCN08382 Rev A 360356 474814Q2R18-IVVI-06-033Jet Pump 05 (WD-1)JCO - Possibly replace Q2R19GENE-0000-0052-9152 R0360359 473034Q2R18-IVVI-06-041Steam Dryer SD-BE-V12-2H, SD-BE-V11-2HAccept As IsGENE-0000-0052-9728 R0360356 475009Q2R18-IVVI-06-050Jet Pump 08 (WD-1)JCO - Possibly replace Q2R19GENE-0000-0052-9152 R0360359 473344Q2R18-IVVI-06-060Steam Dryer Internal Weld SD-BF-V06-2H-IDAccept As Is w/future inspection / LPAGE-NE-0000-0052-7988-R036 0356473619Q2R18-IVVI-06-070Steam Separator Upper Support Ring GussetAccept As Is w/future inspectionGENE-0000-0052-8398-R0360359 473615Q2R18-IVVI-06-080Steam Dryer Internal Weld SD-BD-V06-2H-IDAccept As Is w/future inspection / LPAGE-NE-0000-0052-7988-R036 0356473622Q2R18-IVVI-06-091Steam Separator Shroud Head Bolt 14 and 35Rotate and perform VT-3Video files 481701, 481101, 481301, 481401360359473626Q2R18-IVVI-06-100Steam Dryer Internal Weld SD-BB-V04-2H-IDAccept As Is w/future inspectionGE-NE-0000-0052-7988-R0360356 473923Q2R18-IVVI-06-111Steam Dryer Internal DebrisAccept As Is w/future inspection / LPALost Parts Analysis EC 360467360356 473871Q2R18-IVVI-06-120Steam Dryer Internal Area (Separator Guide Cutout)Increase clearance FDDR RMCN088242WO 681384-01, FDDR RMCN08242 Rev A 360356473839Q2R18-IVVI-06-130Separator Lower Support Ring GussetAccept As Is w/future inspectionGENE-0000-0052-8398-R0360359 474491Q2R18-IVVI-06-140Jet Pump 10 Wedge AssemblyAccept As Is w/future inspectionGENE-0000-0052-9152 R0360359 474070Q2R18-IVVI-06-150Jet Pump 07 Wedge AssemblyReplace swing gate as plannedWO 823272-01360359 473844Q2R18-IVVI-06-160Feedwater Sparger End BracketPlanned Tack Weld per FDI 0194GE-NE-0000-0052-8396-R0360359 474064Q2R18-IVVI-06-170Shroud Repair Yoke at 290 DegreesAccept As Is - Installed conditionGE-NE-0000-0052-8402-R0360359 474485Q2R18-IVVI-06-180Dryer General Visual (220 to 320 Degrees)NRI - No action requiredIR 474497 comments360356 474497Q2R18-IVVI-06-190Feedwater Sparger 13&16 Degree End Bracket & Pi nPlanned Tack Weld per FDI 0194GE-NE-0000-0052-8396-R0360359474501Q2R18-IVVI-06-200Steam Dryer Skirt Baseplate at 220 DegreesRepair Per FDDR RMCN08242WO 681384-01, FDDR RMCN08404 Rev A 36 0356475003Q2R18-IVVI-06-210Steam Dryer WSL @ 220 DegreesNo Action Required - unchangedIR 475003 comments360356 475328Q2R18-IVVI-06-220CS Lower Elbow to Shroud Pipe 290 Degree Azimut hInspect next RFOINR Exelon Level III review360359474514Q2R18-IVVI-06-230Steam Dryer Base Plate Distortion at 320 DegreesNo change- Accept As IsEC 360356360356 474517Q2R18-IVVI-06-240Steam Dryer Surface Anomalies at SD-SKT-V11-IDNRI - No action requiredIR 474517 comments360356 474977Q2R18-IVVI-06-250Shroud Head Flange Ring Segment (EDM Hole)Accept As Is - Previously eval'dGENE-771-110-0595 R0360359 475862Q2R18-IVVI-06-260Core Support Flange Ring ODAccept As Is w/future inspectionGENE-771-110-0595 (May 1995)360359 475332Q2R18-IVVI-06-270Shroud Head Flange Ring ODAccept As IsGENE-0000-0053-0964-R1360359 475339Q2R18-IVVI-06-281Steam Dryer WSLs @ 40, 140 and 320 DegreesNo Action Required - unchangedIR 475339 comments360356 475369Q2R18-IVVI-06-290Steam Dryer Indication, SD-LB-03-W1 OD @ 220 De gRepair per FDDR RMCN08435WO 681384-01, FDDR RMCN08435 Rev A 360356476654Q2R18-IVVI-06-300RPV Jet Pump Annulus FMERemove FMELost Parts Analysis EC 360467360359 476657Q2R18-IVVI-06-311Steam Dryer Exit Plenum Perforated PlateAccept As IsGENE-0000-0053-0964-R0360356 477326Q2R18-IVVI-06-320CS Sparger S3c Drain (two plugs missing tack welds
)Accept As IsGENE-0000-0053-0964-R0360359N/AQ2R18-IVVI-06-330Tie Rod Loose and Missing Nuts (As designed)NRI - No action requiredINR - Future reference only. Mention in EC.360359476540None - IR onlySHB #9 suspect based on UT criteriaAccept As Is w/future inspectionIR, GE Letter DRF B13-01903-8360359
* The highlighted items are specifically included in the scope of RCR  472321 Attachment page 35 Att. 9: CA's to Address Programmatic/ Organizational Issues Attachment Page  36 A. CA's from ERV RCA (Ref. 38) alig ned with Q2R18 Steam Dryer RCA CF. 2


===Background===
==Background:==
:  CF #3 to ERV RCA: Organizational effectiveness and decision-making.  
CF #3 to ERV RCA: Organizational effectiveness and decision-making.


==
==
Description:==
Description:==
The organizational contributors taken in aggregate demonstrate weaknesses in managing information, over-reliance on contractor-performed analysis, and applying a systematic approach to decision making for complex high-risk situations.
The organizational contributors taken in aggregate demonstrate weaknesses in managing information, over-reliance on contractor-performed analysis, and applying a systematic approach to decision making for complex high-risk situations.
Causes Being Addressed Corrective Action (CA) or Action Item (ACIT)) Owner Due Date CF#3 Organizational effectiveness and decision-making. Provide training to Corporate Engineering personnel on the requirement and application of OP-AA-106-101-1006 for complex decision-making (CA# 23 revises OP-AA-106-101-1006).
Causes Being         Corrective Action (CA) or Action Item (ACIT))             Owner     Due Date Addressed CF#3                 Provide training to Corporate Engineering personnel on    A8081      9/20/2006 Organizational       the requirement and application of OP-AA-106-101-          TRLS effectiveness and     1006 for complex decision-making (CA# 23 revises OP-decision-making.     AA-106-101-1006).
Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process.
CA #20 CF#3                  Provide training to Quad Cities Engineering personnel     A8461      9/02/2006 Organizational        on the requirement and application of OP-AA-106-101-       ESPT effectiveness and    1006 for complex decision-making (CA# 23 revises OP-decision-making.      AA-106-101-1006).
Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process.
Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process.
CA #20 A8081 TRLS 9/20/2006 CF#3 Organizational effectiveness and decision-making.
CA #21 CF#3- from Ref. 38   Update HU-AA-1212 Technical Task Risk/Rigor               A8053VP    6/16/2006 Organizational        Assessment, Pre-Job Brief, Independent Third Party         BWR effectiveness and    Review, And Post-Job Brief to provide a link to OP-AA-     (BRWRD) decision-making.      101-1006 for complex engineering decisions and/or products which involve historical data, repeat equipment failure, risk and complex analysis.
Provide training to Quad Cities Engineering personnel on the requirement and application of OP-AA-106-101-1006 for complex decision-making (CA# 23 revises OP-AA-106-101-1006).
CA #22 CF#3- from Ref. 38   Training CRCs shall evaluate the need of providing         A8068EN    6/16/2006 Organizational        training to Exelon FLSs and above on the use and           DES effectiveness and    application of OP-AA-106-101-1006.
 
decision-making.
Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process. CA #21 A8461 ESPT 9/02/2006 CF#3- from Ref. 38 Organizational effectiveness and decision-making.
ACIT #4 CF#3- from Ref. 38   Submit update to OP-AA-106-101-1006 Operational And       A8068EN    6/30/2006 Organizational        Technical Decision Making Process Attachment B,           DES effectiveness and    Recognize Conditions to include lessons learned from decision-making.      the ERV root cause and documentation of all personnel involved in the final product.
Update HU-AA-1212 Technical Task Risk/Rigor Assessment, Pre-Job Brief, Independent Third Party Review, And Post-Job Brief to provide a link to OP-AA-101-1006 for complex engineering decisions and/or products which involve historical data, repeat equipment failure, risk and complex analysis.  
 
CA #22 A8053VP BWR (BRWRD) 6/16/2006 CF#3- from Ref. 38 Organizational effectiveness and decision-making.
Training CRCs shall evaluate the need of providing training to Exelon FLSs and above on the use and application of OP-AA-106-101-1006.
ACIT #4 A8068EN DES 6/16/2006 CF#3- from Ref. 38 Organizational effectiveness and decision-making.
Submit update to OP-AA-106-101-1006 Operational And Technical Decision Making Process Attachment B, "Recognize Conditions" to include lessons learned from the ERV root cause and documentation of all personnel involved in the final product.
Closure to include new assignment for processing of procedure change to Operations peer group.
Closure to include new assignment for processing of procedure change to Operations peer group.
CA #23 A8068EN DES 6/30/2006
CA #23 Attachment Page 36
 
Att. 9:  CA's to Address Programmatic/ Organizational Issues Attachment Page 37 B. CA's from ERV Actuator RCA (Ref.
: 38) & Replacement Dryer Fuel Impacts RCA (Ref. 37) aligned with Q2R18 Steam Dryer RCA - "Negative Design Impacts "
Causes Being Addressed Corrective Action (CA) or Action Item (ACIT)) Owner Due Date CF#3 - from Ref. 38 Organizational effectiveness and decision-making.
Change the design input requirements to include upfront challenges to analysis and assumptions as part of the design review. The documents include CC-AA-103-1003 Owner's Acceptance Review Of External Configuration Change Packages and CC-AA-309 Control of Design Analysis. These front-end challenges shall be applied to all design changes and modifications independent of level. 
 
CA #25 A8068ENDES 7/28/2006 CAPR3 - from Ref. 37 Revise HU-AA-1212, "Technical Task Risk/Rigor Assessment-" to include guidance on how to select what type of third-party review(s) are required. AT#: 330331-21 (complete)
Revision issued by NCS. complete CAPR4- from Ref. 37 Revise PC-AA-1008, "Issue Chartering". Add step 4.3.3.2 to require project teams - in the project scoping phase - to review all CC-AA-102 attachments in order to determine


scope additions and affected organizations. AT#: 281476-07 NCS A8070PM 08/31/06 ACIT6- from Ref. 37 Evaluate the results of this root cause investigation for inclusion in the Project Management TAC.
Att. 9: CAs to Address Programmatic/ Organizational Issues B. CAs from ERV Actuator RCA (Ref. 38) & Replacement Dryer Fuel Impacts RCA (Ref. 37) aligned with Q2R18 Steam Dryer RCA - Negative Design Impacts Causes Being Addressed      Corrective Action (CA) or              Owner          Due Date Action Item (ACIT))
Specifically, investigate training project managers on how to identify  
CF#3 - from Ref. 38          Change the design input                A8068ENDES      7/28/2006 Organizational effectiveness requirements to include upfront and decision-making.        challenges to analysis and assumptions as part of the design review. The documents include CC-AA-103-1003 Owners Acceptance Review Of External Configuration Change Packages and CC-AA-309 Control of Design Analysis. These front-end challenges shall be applied to all design changes and modifications independent of level.
CA #25 CAPR3 - from Ref. 37        Revise HU-AA-1212, Technical Task Risk/Rigor Assessment to        Revision issued complete include guidance on how to select      by NCS.
what type of third-party review(s) are required. AT#: 330331-21 (complete)
CAPR4- from Ref. 37          Revise PC-AA-1008, Issue Chartering. Add step 4.3.3.2 to require project teams - in the project  NCS A8070PM     08/31/06 scoping phase - to review all CC-AA-102 attachments in order to determine scope additions and affected organizations. AT#: 281476-07 ACIT6- from Ref. 37         Evaluate the results of this root cause investigation for inclusion in the Project Management TAC.                 NCS A8070PM    Complete Specifically, investigate training project managers on how to identify which departments to include on a project and when. AT#: 330331-22 Attachment Page 37


which departments to include on a project and when. AT#: 330331-22 NCS A8070PM Complete
ATTACHMENT 14 - of LS-AA-125-1001 (ATT. 10 of specific RCA 472321)
Root Cause Report Quality Checklist Page 1 of 2 A.        Critical Content Attributes                                                          YES NO
: 1. Is the condition that requires resolution adequately and accurately identified?          X
: 2. Are inappropriate actions and equipment failures (causal factors) identified?            X
: 3. Are the causes accurately identified, including root causes and contributing causes?      X
: 4. Are there corrective actions to prevent recurrence identified for each root cause and do  X they tie DIRECTLY to the root cause? AND, are there corrective actions for contributing cause and do they tie DIRECTLY to the contributing cause?
: 5. Have the root cause analysis techniques been appropriately used and documented?          X
: 6. Was an Event and Causal Factors Chart properly prepared?                                  X
: 7. Does the report adequately and accurately address the extent of condition in accordance  X with the guidance provided in Attachment 3 of LS-AA-125-1003, Reference 4.3?
: 8. Does the report adequately and accurately address plant specific risk consequences?      X
: 9. Does the report adequately and accurately address programmatic and organizational        X issues?
: 10. Have previous similar events been evaluated? Has an Operating Experience database        X search been performed to determine whether the problem was preventable if industry experience had been adequately implemented?
B.        Important Content Attributes
: 1. Are all of the important facts included in the report?                                    X
: 2. Does the report explain the logic used to arrive at the conclusions?                      X
: 3. If appropriate, does the report explain what root causes were considered, but eliminated  X from further consideration and the bases for their elimination from consideration?
: 4. Does the report identify contributing causes, if applicable?                              X
: 5. Is it clear what conditions the corrective actions are intended to create?                X
: 6.      Are there unnecessary corrective actions that do not address the      root causes    X or contributing causes?
: 7.      Is the timing for completion of each corrective action commensurate with the        X importance or risk associated with the issue?
Att. page 38


Att. page  38 ATTACHMENT 14 - of LS-AA-125-1001  (ATT. 10 of specific RCA 472321)
ATTACHMENT 14 Root Cause Report Quality Checklist Page 2 of 2 C.     Miscellaneous Items                                                                 YES   NO
Root Cause Report Quality Checklist Page 1 of 2 A. Critical Content Attributes YES NO 1. Is the condition that requires resolution adequately and accurately identified?
: 1. Did an individual who is qualified in Root Cause Analysis prepare the report?           X
X  2. Are inappropriate actions and equipment failures (causal factors) identified?
: 2. Does the Executive Summary adequately and accurately describe the significance of the   X event, the event sequence, root causes, corrective actions, reportability, and previous events?
X  3. Are the causes accurately identified, including root causes and contributing causes?
: 3. Do the corrective actions include an effectiveness review for corrective actions to     X prevent recurrence?
X  4. Are there corrective actions to prevent recurrence identified for each root cause and do they tie DIRECTLY to the root cause?  AND, are there corrective actions for contributing cause and do they tie DIRECTLY to the contributing cause?
: 4. Were ALL corrective actions entered and verified to be in Action Tracking?                   *
X  5. Have the root cause analysis techniques been appropriately used and documented?
: 5. Are the format, composition, and rhetoric acceptable (grammar, typographical errors,   x spelling, acronyms, etc.)?
X  6. Was an Event and Causal Factors Chart properly prepared?
* New AT items are created by CAP organization after MRC approval of RCA.
X  7. Does the report adequately and accurately address the extent of condition in accordance with the guidance provided in Attachment 3 of LS-AA-125-1003, Reference 4.3?
Att. page 39}}
X  8. Does the report adequately and accurately address plant specific risk consequences?
X  9. Does the report adequately and accurately address programmatic and organizational issues? X  10. Have previous similar events been evaluated? Has an Operating Experience database search been performed to determine whether the problem was preventable if industry experience had been adequately implemented?
X  B. Important Content Attributes
: 1. Are all of the important facts included in the report?
X  2. Does the report explain the logic used to arrive at the conclusions?
X  3. If appropriate, does the report explain what root causes were considered, but eliminated from further consideration and the bases for their elimination from consideration?
X  4. Does the report identify contributing causes, if applicable?
X  5. Is it clear what conditions the corrective actions are intended to create?
X  6. Are there unnecessary corrective actions that do not address the        root causes or contributing causes?
X  7. Is the timing for completion of each corrective action commensurate with the importance or risk associated with the issue?
X Att. page  39 ATTACHMENT 14 Root Cause Report Quality Checklist Page 2 of 2 C. Miscellaneous Items YES NO 1. Did an individual who is qualified in Root Cause Analysis prepare the report?
X  2. Does the Executive Summary adequately and accurately describe the significance of the event, the event sequence, root causes, corrective actions, reportability, and previous events? X  3. Do the corrective actions include an effectiveness review for corrective actions to prevent recurrence?
X  4. Were ALL corrective actions entered and verified to be in Action Tracking?
* 5. Are the format, composition, and rhetoric acceptable (grammar, typographical errors, spelling, acronyms, etc.)?
x
* New AT items are created by CAP orga nization after MRC approval of RCA.}}

Revision as of 18:19, 23 November 2019

2006/05/16-QC2 Steam Dryer Inspection Root Cause Report 3/29/06
ML061420307
Person / Time
Site: Quad Cities Constellation icon.png
Issue date: 05/16/2006
From: Dan Collins
Plant Licensing Branch III-2
To:
Maitri Banerjee X2277
References
%dam200606 LS-AA-125-1001
Download: ML061420307 (84)
v • d • e


Text

LS-AA-125-1001 Revision 5 Title: Q2R18 Concerns Related to Steam Dryer Unit(s): Quad Cities Unit 2 Event Date: 03/29/2006 Event Time:

Action Tracking Item Number: 472321-03 Report Date: 05/16/2006 Sponsoring Manager: Tim Hanley, Exelon Nuclear Corporate Manager Exelon Corporation Investigators & Exelon Contracted Contributors:

Roger Armitage & Steve Boline, Quad Cities RC Team Leads Alan Lewis, Quad Cities Engineering (RC Investigator Qualified)

Bhausaheb Shete, Dresden Engineering (RC Investigator Qualified)

Karl Adlon, Quad Cities Engineering Joe Sipek, Dresden Engineering Programs Manager Jeff Miller, Clinton Engineering Programs Manager Chris Cooney, Kennett Square Engineering Dave Haberkorn, Quad Cities Operations Matt Dreyfuss, Kennett Square Engineering Bill McDonald, LaSalle Engineering Pete Shier, Byron Engineering Guy DeBoo, SME Exelon Engineering, Cantera David Melear, Engineer, ILD Inc.

Robert Stackenborghs, Engineer, ILD Inc.

General Electric Corporation (GE) Investigation Team (see Ref. 21 for full list):

Robert Gamble, SME GE RC Team Rowland Linford, GE RC Team Lead N:\PUBLIC\Quad Cities Q2R18 Dryer\!Final RCA Docs\!!RCR Dryer Final no Att.doc

Table of Contents Section Page I. Executive Summary 3-4 II. Condition Statement 5 III. Event Description 6-12 IV. Analysis 13-20 V. Evaluation A. Table of Causal Factors 21 B. Discussion of Basis for Cause Determination 23 C. Discussion of Evaluation of Other Conditions 30 VI. Extent of Condition 35 VII. Risk Assessment 36 VIII. Previous Events 37 IX. Corrective Actions to Prevent Recurrence 37 X. Corrective Actions 38 XI. Effectiveness Reviews 38 XII. Programmatic/Organizational Issues 39 XIII. Other Issues 42 XIV. Communication Plan 43 Figures:

1. General Steam Dryer Configuration F. 1
2. Schematic of Steam Dryer of Base Ring to RPV Lug Orientation F. 2 Attachments:

A. 1-2

1. Event and Causal Factors Chart A. 3-4
2. Event Timeline A. 5-7
3. References A. 8-10
4. Comparison: QC 2 Replacement Dryer Pressure Sensor Data with Q2R18 Dryer Damage.
5. Failure Mode Tree - Dryer Skirt Crack/Deformation A. 11-20
6. Failure Mode Tree - Dryer End Plate Cracks A. 21-24
7. Dryer Lift Event Description and Pictures A. 25-34
8. Table of Q2R18 INRs/IRs A. 35 9: CAs from ERV Actuator RCA Aligned with CF2 of Q2R18 A. 36-37 Steam Dryer RCA 10: Root Cause Quality Checklist A. 38-39 Page 2 of 43

I. Executive Summary:

During the planned in-vessel visual inspection (IVVI) of the Quad Cities Unit 2 (U-2) reactor steam dryer at the beginning of refueling outage Q2R18, a crack was discovered in the dryer skirt at the 140° azimuth location. At the completion of all dryer inspections, cracks were discovered at various locations in the dryer assembly including the dryer skirt base ring, a vane bank end plate, chevron plates, and a latch box. Several of these cracks occurred in areas adjacent to one of the two areas most severely deformed during removal of the dryer in May 2005.

This Root Cause Analysis (RCA) investigation scope was focused on determining the causes of the dryer assembly cracking in the dryer skirt plate, the vane bank endplate, and the latch box assembly.

RCA investigation into the events associated with the design, fabrication, installation and operation of the steam dryer identified a series of factors that, when taken in aggregate, are the causes for the formation of the identified cracks. The causes for each of the three cracks included in the scope of this RCA is summarized below:

1. Steam Dryer Lower Skirt Crack at 140°: The root cause for this cracking is related to deformation caused when the dryer skirt base ring caught on the reactor pressure vessel (RPV) dryer support lugs in May 2005 (referred to as the lifting event). The exact mechanism of initiation of the cracks could not be determined, however the RCA concludes that this event introduced significant plastic strains that reduced the materials fatigue endurance properties. When combined with the cyclic loadings that the dryer experiences during normal operation, fatigue cracking propagated through the skirt base ring and into the dryer skirt panels. The lifting event occurred as a result of changes in design of the installation hardware used in the replacement dryer. This change in installation hardware is considered a root cause.

These changes, combined with widened installation clearances introduced during dryer fabrication (referred to as ovality) allowed for enough movement for the dryer to become damaged on the RPV support lugs during removal. The widened installation clearance introduced from fabrication ovality is also considered a root cause for the dryer skirt cracking.

2. Cracking in Gusset 19 of Vane Bank E at 320°: Root cause is: having very little weld metal between the end plates, proximity to a weld transition (Stress Riser), fabrication stresses due to hood assembly and weld shrinkage, and the presence of operating vibration loads.
3. Cracking in Latch Box at 220°: Root cause is: high residual weld stress from weld end discontinuity and the corner location.

Corrective actions include:

  • Repair of the most severely damaged portions of the dryer skirt and base plate near the 140° azimuth.
  • Replacement of skirt and base plate material in the 220° azimuth area, which did not exhibit cracking but was considered to have similar potential crack initiating factors as the 140° azimuth areas.
  • Modification of the dryer base plate to reduce the potential for future lifting events.
  • Modification of the dryer guide slots to reduce the potential for future lifting events.
  • Repair of the crack in the dryer latch box at the 220° azimuth.

Page 3 of 43

  • Evaluation of the visual indications (crack) in the bank E drying vane end plate. Evaluation concluded that there was adequate justification for continued operation of the steam dryer without repair of the cracking at the gusset to vane bank end plate locations (Ref. 17)
  • Modified main steam relief valve branch lines with acoustic side branches to reduce dryer cyclic loads.

An extent of condition review included inspections of other susceptible areas of the steam dryer. All dryer cracking was reviewed in accordance with IVVI program requirements regarding actions required prior to restart from Q2R18, and appropriate inspections in future outages. The key analysis documents for these determinations are listed in Attachment 8 of this RCA. No other degradation similar to the three events in the scope of this RCA was identified. Analyses completed by General Electric (GE) and reviewed by Exelon determined that without the additional stresses and material degradation resulting from the May 2005 lifting event, the operational loads were not sufficient to initiate cracking in the U-2 dryer skirt plate. Therefore, similar cracking of the Unit 2 dryer is not expected to occur in the future.

In addition, the Unit 1 steam dryer, which did not experience either fabrication ovality or installation lifting events, did not exhibit similar cracking when inspected in the Q1M19 outage in May 2006.

The steam dryer degradation was not reportable, however the issue has been discussed with the Nuclear Regulatory Commission (NRC). A risk assessment of the identified condition was performed and determined the consequences of this event had minimal impact on reactor safety. Although unanticipated structural cracking was identified in the dryer, the cracking did not represent an increase in risk to nuclear safety or off-site dose consequences. A Probabilistic Risk Assessment (PRA) evaluation found this event to be non-risk significant.

Page 4 of 43

II. Condition Statement:

During the planned IVVI in Q2R18, the RPV steam dryer was removed from the vessel and inspected.

Initial inspection revealed a branching crack in the dryer lower skirt area approximately 6 feet in total length at the 140° azimuth location (Refs. 10&11). Subsequent inspections also identified cracking in the steam dryer vane bank end plate in the E bank (Refs. 12&13), and a crack in the lower right corner of one dryer latch box (Refs. 14&15). These three conditions form the specific investigation scope requiring resolution in this RCA, and are referred to in subsequent sections of the RCA as:

Event 1: Steam Dryer Lower Skirt Cracking near the 140° azimuth, identified in AR 472321472321

Event 2: Steam Dryer Cracking in Gusset 19 of Vane Bank E End Plate near the 320° azimuth, identified in AR 473034473034

Event 3: Steam Dryer Cracking in Latch Box near the 220° azimuth, identified in AR 475369475369

Additional dryer cracking was identified during Q2R18, and although not specifically included in the scope of this RCA, all dryer cracking was reviewed and dispositioned in accordance with IVVI program requirements. Specifically, actions required prior to restart from Q2R18 were completed, and appropriate inspections in future outages were specified. The key analysis documents for these determinations are listed in Att. 8 of this RCA.

Consequences & Significance: The dryer is a passive non-safety related component, however, it must remain structurally intact to preclude introduction of loose material into plant systems such that no safety-related systems, structures or components are prevented from performing their design basis safety function. Additionally, the dryer skirt must function as a boundary to maintain the basis for reactor water level sensing and protective actuations. At the time of discovery, all dryer components, including the skirt, remained constrained within the dryer envelope and therefore, there was no safety significance to this event.

This report focuses on the equipment failure, the failure modes, and causal factors for the identified dryer issues. The failure of the skirt plate has the potential to generate debris, for which a lost part evaluation (Ref. 20 is the Lost Parts Evaluation for this condition) was completed for Unit 1 impacts.

This event is not considered a recurring problem since the Unit 2 dryer is a newly installed replacement.

OPEX reviews have not identified previous history with large cracking in dryer skirt plate material similar to that identified in Q2R18. Quad Cities Unit 1 has a similarly designed installed replacement dryer and Dresden Units 2 & 3 have similar replacement dryers that are not yet installed. These three additional dryers will be considered for extent of condition in this RCA.

Page 5 of 43

III. Event

Description:

Note: This event description provides a chronological narrative of the sequence of events as they apply to this RCA. This section also includes Notes intended to highlight the significance of the information as it applies to the subsequent Analysis and Evaluation sections. Additional items included in this RCA report, which may assist in general understanding of the events, include:

Att. 1: Event and Causal Factors Chart.

Att. 2: Event Timeline Table.

Att. 3: List of References.

Fig. 1: General Steam Dryer Configuration Fig. 2: Schematic of Steam Dryer Base Ring to RPV Lug Orientation 2004 - Early 2005 Following several previous Quad Cities outages in which steam dryers were found with failed or degraded dryer elements, a decision was made to purchase and install new steam dryers in both units.

The steam dryer was fabricated and assembled at U.S. Tool and Die in Pittsburgh, PA under the direction of GE. Due to transportation limitations, the steam dryer could not be shipped in one piece in the required timeframe. This required that the dryer be fabricated as two assemblies that were shipped separately and then assembled locally.

Note: During the design and fabrication of the new Quad Cities steam dryers, several issues imposed constraints on the delivery of the first dryer for Quad Cities. Manufacturing delays necessitated that the dryer originally intended for Quad Cities U-1 installation during Q1R18, be delivered for installation in Unit 2 during Q2P03.

March 2005 The Unit 2 replacement steam dryer upper half (vane banks and support ring) and the skirt assembly were welded together at J. T. Cullen in Fulton, IL.

3/30/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 0 was signed by the Reactor Services department representative.

Note: This was the initial end users review in the Exelon design process. This review is considered a cross discipline review and a barrier to prevent negative impacts of design changes. This review was documented after dryer fabrication was almost complete. This topic is discussed further in the evaluation section.

3/31/05 Inspection of the dryer at J.T. Cullen following assembly determined that the as-built dryer dimensions were outside the expected design tolerances. The diameter measured across the 0°-180° orientation measured 245, while the 90°-270° orientation measured 249. Welding distortion was noted as the cause. Laser measurements of the assembled dryer were conducted and confirmed that QC2 dryer base was approximately 2 inches out of round.

Note: Subsequent sections of this RCA refer to this as the ovality issue.

Page 6 of 43

4/25/05 GE Deviation Disposition Request (DDR) 431002828-27 (Ref. 7) was approved, accepting the dimensions of the base plate as-is. Investigation determined the dimensional deficiencies resulted from welding performed at J. T. Cullen, which resulted in distortion of the dryer mid-support ring, skirt and base plate. The DDR noted that the dryer will fit in the vessel despite this ovality. Normal clearances were compromised so additional guidance constraints were placed in the lower guide block to limit misalignment and assist in installation.

Notes: 1. The additional constraints noted above are the guide rod spacer blocks installed under Field Disposition Instruction (FDI) 0085 (Ref. 9)

2. This DDR addressed the dimensional issues due to the ovality but did not address potential residual stresses in the dryer as a result of this distortion.

4/26/05 The U-2 replacement dryer was transported to the station and subsequently moved to the reactor building refueling floor.

4/26/05 Exelon Nuclear Fuels determined that the replacement dryer dP will be less than the original dryer (original dryer dP was nominally 0.3 psid versus an expected dP of 0.1 psid on the replacement dryer).

This change has an impact on Minimum Critical Power Ratio Operating Limit, and on the ASME overpressure results. Root cause analysis on these issues is assigned under IR 330331 (Ref. 37).

Note: The subsequent RCA concluded: the root cause of the event was a lack of information on the project team regarding the sensitivity of non-structural analyses to the dryer dP value.

5/4/05 The Configuration Change Review Checklist (CC-AA-102 Attachment 10F) for the dryer modification EC351168 Revision 1 was signed by the Reactor Services department representative.

Note: This was a second users review in the Exelon design process. This review is considered a cross discipline review and a barrier to prevent negative impacts of design changes. This topic is discussed further in the evaluation section. This review was documented after the dryer was already fabricated and staged on the Quad Cities Refueling floor.

05/07/05 Unit 2 shutdown for Q2P03 for the main purpose of installing the replacement dryer.

5/11/05 During initial installation in the U-2 reactor vessel an interference was encountered that prevented setting the dryer onto RPV dryer support lugs. At approximately 2.5 above the dryer support lugs, the overhead crane cables went slack and the dryer assembly shifted towards North (approximately 110° azimuth). The dryer was lifted and the vessel area inspected without identifying the source of the interference. Upon restart of the descent, the dryer again stopped and shifted towards North.

The dryer was raised slightly to allow further detailed inspection. A camera inspection inside the skirt revealed that the inner diameter of the dryer skirt base plate was interfering with the steam separator Page 7 of 43

guide rods. Although the overall outer diameter of the dryer assembly was not changed by the new design (Ref. 1), the skirt inner diameter is smaller with the base plate protruding farther towards the center of the dryer than the original design. This resulted in the interference with the separator guide rods, with the skirt base plate contacting the two guide rods located at the 20° and 200° azimuths.

Installation activities were stopped and the Outage Control Center (OCC) was notified of the issue, and discussions were initiated to determine resolution of this problem.

Note: The U-2 replacement dryer exhibited limited clearance between the RPV dryer support lugs and the cutouts provided in the base plate ring. As the dryer is lowered, the skirt base plate must pass all four of the support lugs. The width of a support lug is 3 inches, while the width of the base plate cutout provided is 4-inches, leaving a nominal 1/2 clearance on each side of the lug. This presented a known challenge and plans were to use additional care to field verify that acceptable clearance existed, or modify the clearances as needed. While the dryer was lowered into the RPV for the first time, the GE Product Line Manager was stationed in the reactor cavity to monitor the clearances. It was confirmed during this initial lowering that the clearance between the base ring cutout and RPV lugs was small, but the dryer had been installed without incident until the interference with the separator guide rods was identified.

5/12/05 When the interference between the separator support rods and the base plate was identified and the dryer could not be installed, it was decided that the dryer would be removed from the RPV to allow modification of the base plate. The OCC recovery and action plan for the dryer removal discussed the tight clearance issue with the oncoming crew. Instructions were provided to the oncoming refuel floor crew performing the dryer lift to watch the RPV lug clearance very closely due to the tight clearance.

During the lift for removal of the dryer, the base plate impacted the vessel support lugs despite the increased scrutiny, including performing the lift slowly, as evidenced by multiple stops. Att. 7 describes in detail the sequence for the base plate contact with the RPV support lugs. At the time of this dryer lift, the load cell display for the overhead crane was not functional (overload cutout circuits were functional), so there was no ability to estimate the impact load based on floor observations. Workers reported visual evidence of a high load on the lift cables from the noise and rapid cable movement when the load sprung free. When the dryer was set on the decontamination pad, visual damage to the base plate was evident and the OCC was notified.

Inspection of the base plate showed a downward deflection/distortion in the dryer base plate from its normal flat horizontal shape. These downward bends were recorded as 3/4 at the 140° location, 5/8 at the 220° location, and 5/16 at the 320° location (Ref. 1).

A detailed discussion of what occurred during this Lift Event, along with pictures of the damage are provided in Att. 7.

5/13/05 Prompt Investigation Report 334348 (Ref.4) on the dryer damage was performed and presented to MRC on 5/13/05. This report reviewed the sequence of events, and detailed the observed damage as follows:

1. Marks on the bottom of the base plate at the 20° position
2. Mark (burr) on the inside of the base plate at the 220° position
3. At the 40° and 140° positions, seismic shim blocks were noted to have shifted and were scratched
4. Raised metal on 3 clearance slots Page 8 of 43
5. Wear on one RPV support lug Items 1 through 3 were believed to have occurred when the dryer shifted towards North as it contacted the separator guide rod. The prompt investigation described conflicts or problems with:
1. Original tolerances did not allow the separator guide pins to clear the ID of the dryer base plate.
2. Traveler Package KCZKU-INSTALL-1 stated that special care should be taken to verify no interferences exist, as well as the need to maintain the dryer level and to watch the overhead crane load cell for deviations
3. The overhead crane load cell was not functioning.

This prompt investigation concluded that the base plate damage was caused by interference with the separator guide rods and RPV support lugs.

Note: The prompt investigation addressed the fact that the dryer could not set into place due to contact with the separator guide rods. It noted that the cause of the damage was not known at this time (this was handed off to the subsequent ACE). The prompt did not discuss the effects of the damage to the dryer from the lifting event.

5/15/05 To eliminate the interference between the separator guide rods and the skirt/base plate, cutouts were provided in the dryer skirt and the base plate at the 20o and 200o azimuth locations. (WO732708-01 / GE Field Deviation Disposition Request (FDDR) RMCN06243, Ref. 29). The cutout of the partial penetration weld was seal welded at the cutout and examined via PT exam.

The damage to the base plate was evaluated and found acceptable by GE, an independent third party review, and Exelon for use-as-is (Ref. 1 & 8). FDDR RMCN 06245 included instructions for the material cleanup and disposition of the as-left deformations. The indications caused by the contact with the RPV lugs during the dryer removal were removed from the metal surfaces of the dryer and examined via PT exam prior to reinstalling the dryer in the reactor vessel.

Note: This RCA reviewed this FDDR, and the supporting documentation, and noted a lack of detail in documenting both the inspection and analysis activities completed to resolve this issue.

Because this RCA concluded that the transient imposed on the base plate and dryer skirt was a causal factor for the subsequent cracks during operation, it must be concluded that the Q2P03 review (May 2005) was a missed opportunity to determine the actual state of the dryer. This topic is discussed in more detail in the Evaluation section.

5/16/05 Unit 2 was started up and operated at EPU and pre-EPU power levels during the remainder of the fuel cycle. No apparent complications to Unit 2 operation due to steam dryer issues were observed during this operating cycle, and the dryer cracking condition was not evident until reactor disassembly for Q2R18 in March 2006.

5/25/05 An ACE (Ref. 2) for the steam dryer lifting event was completed and approved on this date. This RCA reviewed this ACE in detail following the identification of cracking in Q2R18. The results of this review are discussed in the Evaluation section.

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This ACE also noted the fact that the crane load cell was not working at the time of the May 2005 dryer lifting event, concluding that that this was not a significant factor in the apparent cause. (Note: The load cell was repaired May 16, 2005 prior to placing the dryer back into the vessel (WO 805641-02)).

A GE Root Cause Analysis (Ref. 6) was provided on 5/25/05. This report determined that the cause of the interference between the base plate and the steam separator guide pins was that the dryer design process did not ensure that fit-up problems did not exist. This occurred because the Computer Aided Design (CAD) model was not adequately developed. The GE RCA noted that several GE design engineers had initially identified the potential for interference at the separator guide pins, but had failed to revisit the concern prior to completion of the dryer design.

3/28/06 U-2 shutdown for refueling outage Q2R18. While performing IVVI during Q2R18, the cracks were discovered on the steam dryer that led to the initiation of this RCA. The scope of this RCA includes (references noted are for the original Exelon Corrective Action Process (CAP) Issue Report (IR) numbers, and the GE Indication Notification Report (INR) numbers):

Event 1- The large crack in the dryer skirt at the 140° azimuth (Ref. 10, 11)

Event 2- Dryer E bank end plate crack at 320° azimuth. (Ref. 12, 13)

Event 3- Latch Box crack at 220° azimuth. (Ref. 14, 15)

In addition, all four steam dryer lifting eyes were discovered out-of-position, with one lifting eye exhibiting thread damage to the lifting rod. This issue was originally in the scope of this RCA, but it was determined that the lifting eye concerns were not related to the dryer cracking issues. For this reason, the lifting eye issue was removed from the RCA scope, and transferred for evaluation as a separate Equipment Apparent Cause Evaluation (EACE) (AR# 471848-05). A summary of the results of this EACE appears below:

Summary EACE 471848-05: Dryer Lifting Lug Rotation Apparent cause: The design of the lifting eye retention method was inadequate to ensure positive engagement. The design provided no ability for ensuring adequate alignment. The recess was located on the lifting rod, which was contained within the threaded connection once the lifting eye was threaded on. The design relied entirely on external orientation of the lifting eyes, which provided no positive verification. In addition, the dimensions of the recess provided minimal opportunity for successful engagement.

Corrective Actions:

1. Modify/Install design of Quad Cities Unit 2 Steam Dryer Lifting Eyes to provide more robust anti-rotation. (Completed before start-up from Q2R18)
2. Modify/Install design of Quad Cities Unit 1 Steam Dryer Lifting Eyes per EC 360571.

(Scheduled for completion during Q1M19 in spring 2006).

3. Similar corrective actions will be completed on the Dresden replacement dryers prior to installation.

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Identification of Missed Opportunities:

This RCA used the information presented in this event description (and the associated Event and Causal Factors chart in Att. 1) to identify potential issues and missed opportunities for earlier detection, or prevention of the three events in the scope of the RCA. These items are listed below and became the subject of more detailed analysis described in the next section.

Missed Opportunities for Earlier Detection or Prevention of Dryer Cracking:

1. Inadequate inspection of the May 2005 damage: Actions were identified in Ref. 1 & 8 to perform a liquid penetrant test (PT) of adjacent welds. The Field Deviation Disposition Request [FDDR]

(Ref. 8) was not clear in identifying specific welds to be inspected - it just specified, all adjacent welds in the areas that were distorted shall be subjected to PT examination. Interviews with QC personnel determined that only adjacent welds on the outside diameter (OD) of the skirt were PT examined. The weld between the vertical skirt plate and the horizontal base plate on the ID of the skirt was not examined either visually or via PT. This was a missed opportunity to determine the integrity of the base material and weld integrity on the skirt inside diameter (ID) and thus we cannot conclusively eliminate the skirt ID as a crack initiation site. The lack of inspection of the ID of the skirt also eliminated the potential to find the dimpled section of the skirt at the 140 and 220° locations which may have led to further analysis of the residual stress placed on the metal.

2. Inadequate disposition of May 2005 damage: In the original dryer design effort, the lower skirt hardware was included in the modeling as a super element. That is, because the as-designed load conditions on the dryer skirt are typically low and the size of the finite element model was already excessively large, the skirt details below the water line were not included in the finite element calculations with fine nodal granularity. The entire lower area is modeled as a lumped mass and stiffness matrices in the finite element calculations. This is appropriate if the service conditions stay inside the assumed as-designed bounds. However, once this portion of the unit had been subject to permanent, localized damage, a rigorous evaluation would have considered whether the dryer was subject to future degradation. This was not specifically included in the disposition of the damaged area.
3. Deficiencies in Design Change Development: A fundamental change in the design of the dryer caused the outer diameter of the dryer shell skirt plate to be reduced, in order that the drain channels could be on the exterior of the dryer assembly. (Note that the outer diameter of the horizontal skirt base plate was the same. The vertical skirt shell plate was reduced.) Exterior drain channels were used in an effort to reduce minor cracking commonly experienced in the area of internal drain channels in earlier designed BWR steam dryers. In addition, because the more robust replacement dryers were heavier, the designers looked for non-structural areas where weight could be reduced. For these reasons, the original design use of 2 continuous guide channels for both of the dryer guide rods, and (4) guide channels for the RPV support lugs were eliminated. These channels were each changed from being a continuous vertical guide path along the height of the dryer skirt, to being two-point (top and bottom) alignment connections (Dryer guide slots for alignment with the RPV guide rods), and Base Ring cutouts to pass through the RPV support lugs. The original guide channels for the RPV support lugs had the same 4 wide clearance as the new dryers base plate notches. The implication of this is that the tight tolerance on the rotational alignment is enforced at all axial positions during movement. It is this enforcement of rotational alignment that was compromised by the removal of the guide Page 11 of 43

channels. The 4 wide notches in the base plate only enforce this alignment while the base plate is at the elevation of the RPV lugs, setting up the potential for misalignment at other dryer elevations. This, in conjunction with the small clearance (the RPV lugs are 3 wide, so the average clearance is 1/2 on each side) increase the probability that an impact would occur, by making a higher demand on the users to obtain the simultaneous alignment without impact. Thus a negative consequence of the revised dryer design sacrificed a tolerant and self-correcting configuration for a less tolerant configuration that invited interferences.

4. Fabrication Ovality Issues: Fabrication deficiencies had already been identified prior to the May 2005 lift event. These deficiencies resulted during the welding of the two halves of the QC2 dryer at J. T. Cullen. This assembly process resulted in distortion of the dryer mid-support ring, skirt and base plate.

The distorted as-built dryer base plate condition was identified, evaluated and addressed prior to shipping the dryer to Quad Cities under a Deviation Disposition Request (DDR) (Ref. 7).

Corrective measures were taken to prevent this distortion in the assembly of the subsequent dryer assemblies (QC 1 dryer). The distorted QC2 dryer was evaluated and accepted for use, with actions to install additional guidance constraints on the lower guide blocks. (Refs.7&9). This evaluation focused on vessel clearances for installation and removal of the dryer but did not address potential for induced stresses on the dryer components resulting from the distortion.

Despite the completion of these corrective actions to accommodate installation and removal of the distorted QC2 dryer, the assembly distortion still contributed to the excessive clearances between the dryer and dryer guide rods, and was cited as one of the two apparent causes in the ACE for the May 2005 events. These conditions indicate two missed opportunities:

  • The potential for installation alignment issues was recognized after the ovality was identified but corrective actions were not successful in preventing the lift event.
  • The potential for internal metal stresses induced from the ovality was not formally addressed in the DDR, FDDR, EACE, or ECs reviewed during this RCA.

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IV. Analysis:

Several root cause analysis techniques were used in this investigation. Initially, an Event and Causal Factor Chart (Att. 1) was created to document the known sequence of events, and conditions. This document was used to identify an initial strategy and direction, including the decision to divide the concerns into three issues (Dryer Skirt Crack, Dryer End Plate Crack, and Lifting Lug Concerns). The investigation team then used Failure Modes and Effects Analysis (FMEA) to identify potential failure modes. These potential failure modes were documented on a Complex Troubleshooting Failure Mode Tree (FMT) (ref. MA-AA-716-004, Att.2 pages 3 and 4). Each failure mode was then broken down into potential causes with associated validation and action steps. These actions were then prioritized according to the probability of the failure mode being a causal factor and the availability of data (some validation steps were able to be completed early in the investigation while others required additional time for analysis). The FMTs for Event 1 and Event 2 appear in this report as attachments 5& 6 respectively.

The Lifting Lug Concerns were later determined to be a separate issue from the Dryer Cracking and transferred from the scope of this RCA to EACE AR# 471848-05. For this reason the FMT related to the lifting lug issues is not included as an attachment to this RCA. Similarly, as the Q2R18 dryer inspections continued, and additional issues were identified, the Latch Box Cracking near the 220° azimuth was added to the RCA scope as Event 3 based on a potential linkage to the other two issues. A new FMT was not created for this event because it was evident that the analysis and strategy used for Event 1 (Skirt Crack) and Event 2 (End Vane Bank Crack) were appropriate and bounding for Event 3 (Latch Box Crack).

The FMT charts identified a set of low probability and higher probability failure modes.

The lower probability items were set aside allowing a focus on the higher probability items which included:

  • Design related issues where the analysis used might have underestimated the loads the replacement dyers would be subject to, and also underestimated the stress conditions resulting from the skirt base cutouts.
  • Design related issues that effected the resulting lift event.
  • Fabrication errors, which resulted in the skirt base ring ovality.
  • Installation damage resulting from the lift event.

These probable failures modes were reviewed using additional RCA tools such as:

TapRoot, Cause and Effect Analysis, and Barrier Analysis. The RCA also utilized a significant amount of technical analysis including metallurgical testing of samples of the U-2 Dryer skirt and baseplate, and computerized structural analysis. This analysis is described in more detail below:

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A. Structural Analysis Summary:

Detailed finite element models of the dryer skirt and other dryer components were developed or upgraded. Multiple elastic and inelastic finite element analyses were run to simulate the conditions that would have caused the observed deformations. These simulations were used as sensitivity evaluations such that some postulated loadings could be eliminated (i.e., if the loads and stresses resulting from some scenarios couldnt have caused the observed deformation, the scenario could be eliminated). Some of these analyses were used to approximate the material condition resulting from these events and to assess the extent of the possible degradation.

1. The original full steam dryer finite element model contained a super element for the submerged portion of the skirt and water. The skirt in the super element did not have the detail of the base plate cutouts or gussets located on either side of the cutout. A local solid 3D detailed finite element model was created for analysis of the failure location.

The analysis validated that the cut out modeling was not significant in determining the skirt stresses & modal response. (Ref. 29)

2. More detailed elastic-plastic analysis of the skirt cutout and gusset areas at 140° was completed. This analysis predicted 17.3% strain at the top of the gusset in the skirt panel.

Strain at the edge of the gusset in the cut out was 4%, which corresponds to 55-60 ksi using elastic-plastic analysis. (Ref. 21) This analysis also estimated the amount of loading needed to cause the observed deformation from the list event to be 47,000 pounds.

3. An analysis was completed to estimate the corresponding reduction in the fatigue stress limits in the 140° azimuth Dryer Skirt Crack as a result of the lifting event.

Excerpts from this analysis report (Ref. 40) appears below:

given the higher plastic strain and complementary increase in strength of the deformed base ring location, the expected fatigue endurance properties would be significantly reduced due to mean stress effects. This effect can be calculated directly from the equations used by Manjoine, et al [Ref. 41 of this RCA].

Although the region of interest was cold worked by the installation event [referred to as the lifting event in other sections of this RCA], the evaluation of the mean stress effect was performed based on the fatigue properties of annealed material.

Therefore, the evaluation should be viewed in qualitative rather than quantitative terms. For conservatism, the loading was considered as stress controlled in the determination of the mean stress effect, i.e. the range of Pl + Pb +Q was assumed to exceed 27.2 ksi. The impact of an assumed residual (mean) stress of 60 ksi would be a 30% reduction in the allowable while the assumption of a 70 ksi yield strength to represent the local mean stress would reduce the allowable by 50%.

These levels of reduction in fatigue properties are very likely given the deformation and the constraint imposed by the several intersecting welds present at the base ring cut out corner-solid gusset-skirt region where crack initiation occurred.

In summary, the plastic deformation would be expected to lead to a high residual mean stress. Consistent with the understanding of fatigue behavior in the presence Page 14 of 43

of high mean stresses, the fatigue endurance limit would be reduced. Based on the conservative evaluation, the reduction in endurance limit would be expected to be a maximum of 50%.

3. Hydrodynamic and acoustic loading on the dryer were re-evaluated. Ref. 21 noted that the turbulent water loads acting on the dryer skirt were not analytically evaluated, but the skirt is in a relatively quiet region near the vessel wall. This indicates that any loading on the skirt from the feedwater flow and separator flow will be a turbulent buffeting from the mixing of these flow streams below the skirt. Since the replacement dryer skirt design should be more able to resist these turbulent loads (replacement dryers used 3/8 thick vs.

1/4 thick plate and the drain channel design/fabrication moved the weld away from the discontinuity), it can be concluded that the water loading on the replacement dryer skirt would not present any fatigue issues.

The July 2005 report on QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis Based on Measured EPU Conditions (Ref. 35) was reviewed and it was noted that there are additional hydrodynamic loads, assessed to be too low to be of consequence. An acoustic load frequency at 155 Hz appears on the strain gauges and accelerometers and based on the magnitude of the response in power spectral densities is the most dominant mode in the reactor. This mode has been attributed to the Electromatic relief valve (ERV) stub tube resonance and is included in the load basis for the analysis.

Further modal analysis concludes that the failed skirt does not have modes in the low frequency range. This means that while the loads may be impacting the dryer, they are not driving structural resonances. In addition, these frequencies would affect the entire dryer, not just the skirt panel. This results in a conclusion that these loads are not a causal factor in this RCA.

4. A detailed stress analysis of the dryer lifting event was completed (Ref. 36). The analysis report concluded: In this analysis the lifting forces were applied unevenly in various configurations on the full dryer finite element model in order to assess if the lifting event could have caused crack initiation in the vane bank end plates and/or latch box. The results indicate that no lifting cases could initiate a crack in either the inner vane bank end plates or latch box corner.

B. Follow-up Inspections Summary

1. The inside of the dryer skirt at the 20° azimuth where previous damage from impact with the separator guide rods had been noted were re-inspected and evaluated. This evaluation concluded that the damage was small with no deformation of the base ring.

While the minor damaged was repaired, the conclusion remains that impact in this area was not a causal factor in any of the cracking events in the scope of this RCA.

2. The inside diameter of the dryer skirt ring was re-inspected and evaluated at the 140°,

220° and 320° areas. The 140 ° area already required repair of the identified skirt and base ring cracking. The 220° area had a similar amount of base ring and skirt plate deformation as the 140° area, but no observable cracking. The similar deformation was Page 15 of 43

the major factor in the decision to cut out and replace the deformed material at the 220° area despite no observable cracking (Refs. 27 & 32). The 320° area had gusset deformation less than half that at the 140° location, and no ID skirt or base ring deformation so this area was analyzed to leave as is.

C. Metallurgical Analysis Summary:

Cut out samples of the cracked areas of the dryer skirt were sent out to GEs metallurgical labs at Vallecitos, CA. The purpose for the testing was to determine the following:

1. Site of crack initiation
2. Mode of crack propagation
3. Material characteristics germane to the investigation
4. Likely cause of cracking The results of these examinations were documented in GE-NE-0000-0052-9666, QC U-2 Replacement Steam Dryer Metallurgical Evaluation (Ref. 19). In addition GE completed a separate evaluation of the Transgranular Stress Corrosion Cracking (TGSCC) identified in these metallurgical samples in the report listed as reference 16 to this RCR.

Excerpts of the Executive Summary and selected sections from the metallurgical report is report are reproduced below:

Executive Summary of GE Metallurgical Evaluation (Ref. 19):

During inspection of the replacement steam dryer at Quad Cities Unit 2 during Q2R18, cracking was observed in the skirt and base plate at the 140 degree location. Samples were removed from the dryer and sent to GEs Vallecitos Nuclear Center for further evaluation.

Visual examination of the samples showed a relatively smooth straight fracture in the skirt plate, consistent with a fatigue mechanism. Examination of the sample taken from the base plate to skirt plate weld confirmed the fatigue cracking mode.

No evidence of ductile tearing (i.e., overload) was found. Near the inner diameter (ID) of the base plate, the fracture exhibited slight twisting, which suggests there was a torsional component to the loading by the time the crack progressed to the ID. The cracking appeared to have initiated in the base plate region and progressed upward into the skirt plate. Although no clear initiation site could be identified, the fracture most likely initiated near the OD of the base plate.

Optical metallographic examination of the skirt plate-to-base plate weld cross sections showed two key features: (1) the root areas of the ID and OD welds contained lack of penetration; and (2) transgranular, branched cracking characteristic of transgranular stress corrosion cracking (TGSCC) initiated from the root area and propagated into the skirt and base plate in both the 140 and 220 degree sections. Neither feature, however, could be identified as an initiator of the Page 16 of 43

observed fatigue cracking. Some increase in hardness was noted in the skirt plate, consistent with the observed deformation. The material chemistries were consistent with austenitic stainless steels.

Based on the observations, the material failed by mechanical fatigue, initiated towards the OD of the base plate region. Given the deformation observed in the samples examined, the stresses introduced into the cut-out region by bending and the location of the cracking, it is likely that the lifting event contributed to the observed failure.

Excepts from Discussion Section of GE Metallurgical Evaluation (Ref. 19):

Subsequent SEM (Scanning Electron Microscopy) examination of the fracture surface confirmed the transgranular nature of the cracking, consistent with fatigue. All regions that were examined were consistent with a fatigue cracking mechanism, with no evidence of ductile overload found. Some lack of penetration was noted in the weld root, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. Inclusions in the weld root were also identified; based on the EDS [Energy Dispersive Spectroscopy]

analysis, these inclusions most likely resulted from the original welding process, and were not associated with the failure.

Optical metallography confirmed that the welds were fabricated with at least two passes, which is consistent with the partial penetration weld geometry specified for the skirt to base plate weld. In addition, lack of penetration in the weld root was observed in all of the six cross sections examined. Optical metallography also confirmed that the material was in a solution annealed condition, with some evidence of strain hardening in the base plate, as determined by microhardness.

The areas of apparent strain hardening are consistent with the deformation from the lifting event. The cracking mode was transgranular with small secondary cracks, consistent with a fatigue mechanism.

One additional observation was the presence of transgranular cracking in the weld root region of both the 140 and 220 ° samples. Given the branched nature, along with the presence of multiple indications in both the skirt and base plate regions, the most likely cause is TGSCC. TGSCC requires three factors to be present:

(1) wetted environment; (2) aggressive species (e.g., halogens); and (3) stress.

Wetted environment: At the 140 degree location, the weld root crevice was exposed to the environment Aggressive species: Given that the partial penetration weld was made by a flux-core process and weld fluxes typically contain fluorides for fluidity and wetting, the presence of fluorine in the weld root is not unexpected. In addition, the manufacturer of the weld flux confirmed that approximately 3% fluorine was present in the welding flux.

Stress: Significant stress would be present from welding. [The deformation from the lifting event was also a source of stress.]

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Since all three factors are present, TGSCC is the most likely cause of the observed transgranular, branched cracking in the weld root. Two factors, however, indicate that TGSCC did not contribute to initiation of the fatigue cracking: (1) On the fracture face, the transgranular cracking was consistent with fatigue. There were some secondary cracks, but no major network of secondary branched cracking that would characterize a TGSCC crack was found, and (2) the initiation region (see Figure 3-3(b) in Ref. 19) does not appear to be in the root of the weld. The directional features indicate initiation on the OD surface. The laboratory examination confirmed that the primary fracture was one of mechanical fatigue; however, the exact initiating location could not be identified.

Key Conclusions from GE Metallurgical Analysis The GE metallurgical analysis proved to be a key component in this RCA. While the exact initiation mechanism of the dryer skirt plate could not be identified, the results did eliminate several of the potential failure mechanisms, and supported a determination of most probable causes. This included the conclusions below:

1. Skirt plate cracking is consistent with fatigue cracking.
2. There is no evidence of ductile tearing.
3. Cracking appears to have initiated in the base plate region and then propagated into the skirt plate.
4. The fracture most likely initiated near the OD of the base plate.
5. TGSCC was observed in samples from both the 140° and 220° regions, but in neither case was the TGSSC identified as an initiator of the fatigue cracking.
6. Deformed areas exhibited some increase in metal hardness.
7. Material chemistries were consistent with austenitic stainless steel.

D. Interview Summaries:

Interviews were completed with a number of key positions associated with this RCA.

This included personnel from: Exelon Reactor Services, GE Installation, and GE Design personnel. A summary of the information from these interviews appears below:

A. Reactor Services:

1. Use of Crane Load Cell Scoreboard:
  • Originally installed as a corrective action from an OPEX event where a Dryer was attempted to be removed with only 3 of 4 hold-downs unlatched.
  • Typical use of the scoreboard is that the weight of the component will be known and significant deviations will indicate a potential hang up of the load.

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  • If a significant change in expected load displayed occurs the Technical Director (TD) would be monitoring the display and would signal an emergency stop.
  • For the Dryer installation the TDs were GE Supervisors.
  • The Signal person for the load moves was typically a Venture Boilermaker assigned to the GE crew.
  • Would an available scoreboard have made a difference in this event? Unsure -

The Dryer lifting rigs are all metal components so any increase in load would occur very quickly, likely before a response could be made by a lift crew, even in slow speeds. In other lifts where synthetic lifting slings are used, the response time might be longer. (In this case, there is a potential that a load cell change could be responded to when the dryer metal starts to deform, and possibly before the deformation would become permanent.)

  • The load cell display has been unreliable since installation. Several outages included lifts made where the scoreboard was inoperable.
2. Dryer Issues:
  • What are the key points in a Dryer lift (term noted in several IRs associated with this event)? A: Aligning the Dryer guides with the guide rods, and the interface between the RPV lugs and the Dryer support ring are considered key points of this lift now and historically.
  • Rx. Services was aware that the full-length guide channels that existed on the old dryer no longer existed on the new dryers.
  • Rx. Services had limited formal involvement with the design of the new dryers (i.e., did not participate in the project team).
  • Rx. Services personnel signed off on the new design because they believed that it could be made to work with some additional care. They also were aware that GE personnel would supervise the initial Dryer insertion and that modifications would be made if needed to support successful installation and removal of the replacement dryers. (Some of the fit up issues would need to be field verified especially during the first installation).
  • Initial insertion of the new dryer allowed for a person to be located in the Refueling bulkhead to assist in alignment. This option will not be available in future lifts because they will be done underwater for dose control.

B. GE Personnel:

Dryer Project Installation Personnel

1. What was included in the pre-job brief for this evolution? A: The pre-job brief prior to the initial dryer move focused on the movement from the refuel floor to the vessel, since this was an abnormal move and resulted in various load path issues. It also included discussion of the dryer clearance issues and that the dryer Page 19 of 43

design was different and would require significant monitoring while being installed.

2. What process document covered this lift (procedure, traveler, etc.)? A: The traveler provided the direction for initial installation of the dryer - Rev. 0 for the initial move and Rev. 1 for the final installation following modifications. The removal for modifications was performed per the station reactor disassembly procedure.
3. What were considered key points in this lift? Were they formally documented?

A: There were hold points when the dryer base ring was at 6-inches above the RPV lugs and again when the mounting block was 6-inches above the RPV lugs.

4. Why was the inoperable load cell scoreboard considered acceptable? A: It is not unusual for load cell/displays to be malfunctioning at various plants.

Dryer Project Design Personnel

  • The Dryer design was changed from full-length channels was to accommodate relocating the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. To be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channels on the outside of the skirt. Full-length guide rod channels previously integral to the skirt could no longer remain.
  • The replacement dryer design uses a 4-point contact design which also minimizes weight increase. The new dryers are more structurally robust through the use of heavier material. The increased weight has to be maintained within the structural capabilities of the existing RPV dryer support lugs.
  • This installation hardware is consistent with the design of newer GE BWRs.

There has been no experience of a similar Lift Event in these newer BWRs.

  • The ovality event was noted as a factor in degrading the alignment of this QC U-2 replacement Dryer.

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V. Evaluation:

This evaluation section is organized as follows:

A. Table of all Causal Factors that this RCA concluded influenced this event.

B. Additional discussion of the basis for cause determination.

C. Discussion of other event conditions that were evaluated as potential causal factors, but rejected, how they were eliminated as causal factors, and their final disposition (no action required, addressed in Programmatic/Organizational Issues, addressed in Other Issues section)

The final section C is needed because this RCA required extensive technical and analytical review and in some cases, cause determinations relied on elimination of other causes to support the RCA conclusion of root and contributing causes.

A. Table of Causal Factors Cause (describe the cause and identify Problem Statement whether it is a root cause or contributing Basis for Cause Determination cause)

Event 1: Crack & CF1a: Lift Event- Design Note: The basis for cause determination is deformation of factors: similar for CF1a, & CF2b and are combined dryer base plate 1) New dryer skirt base ring had below:

and skirt cutouts to fit around RPV support

  • Root cause supporting analysis concluded identified in lugs, previous design had full that the skirt region cracking would not Q2R18. length channels. have initiated had the Q2P03 dryer lift
2) New dryer has two dryer guide event not occurred.

slots at top and bottom of skirt vs:

  • Lift event resulted from changes in dryer full-length channel in old design. installation hardware, not from personnel Root Cause errors during dryer removal.

Event 1: Crack & CF1b. Lift Event - Fabrication:

  • Tolerances between the dryer guide rod deformation of Ovality Results in Looser slots & guide rods allows for rotational dryer base plate Installation Clearances - movement of dryer resulting in skirt base and skirt Distortion/ovality of dryer base plate cutouts not aligned with RPV identified in plate further degraded alignment support lugs.

Q2R18. control provided by dryer guide

  • Tolerance in guide components was slots. further degraded by ovality issue.

Root Cause See Evaluation of Lifting Event Causal Factors CF1a, CF1b (section after this table) for more details on basis.

Event 1: Crack & CF2: Disposition of damage from

  • FDDR accepted condition as-is but did deformation of Q2P03 lift event concluded use not fully evaluate the material effects of dryer base plate as is. GE FDDR, and site the damage (focus on fit issues).

and skirt review concluded:

  • Assumed damage occurred in low stress identified in Page 21 of 43

Cause (describe the cause and identify Problem Statement whether it is a root cause or contributing Basis for Cause Determination cause)

Q2R18.

  • Modify base ring for regions.

separator guide rods

  • Inspections limited to visual & PT in the
  • Run for 1 cycle outside diameter areas. No detailed
  • Repair/modify base ring for inspection of inside diameter.

RPV Lugs in Q2R18

  • Since follow-up analysis in this RCA did not identify an exact initiation mechanism Contributing Cause for the cracking, a more detailed analysis during Q2P03 is unlikely to have changed the outcome. (For this reason, this issue is considered a contributing cause rather than a root cause).
  • Retained as a contributing cause because of small possibility that more detailed inspections could have detected cracks in the skirt or base plate, specifically on inner diameter areas.

See CF2: Disposition of Lifting Event Prior to Start-up from Q2P03 (Second section after this table) for more details on basis.

Event 1: Crack & CF3: Analysis - Operating Cycle

  • Operating pressure oscillation loads from deformation of Impacts MSL acoustics resulted in skirt base ring dryer base plate stresses that when combined with the and skirt reduced fatigue endurance caused by the identified in Contributing Cause plastic deformation from the lift event, Q2R18. was adequate to initiate and propagate cracking.
  • Considered a causal factor in crack initiation and propagation but not a root cause because analysis has concluded that the operating loads are not sufficient to initiate cracking on their own.
  • Att. 4 of this RCA presents a comparison of the U-2 pressure sensor data with the areas that experienced damage, which supports the conclusion that operating cycle impacts were not initiating factors or root causes to this event.

Event 2: Crack CF4 - Cracking in Gusset 19 of

  • The basis for the cause determination is found in vane Vane Bank E End Plate Near photographic observation by the root bank of E bank the 320° Location - most cause team and GEs evaluation Page 22 of 43

Cause (describe the cause and identify Problem Statement whether it is a root cause or contributing Basis for Cause Determination cause) near 320 ° probably due to assembly, and (Reference 17).

azimuth residual welding stresses,

  • The Lift Event was rejected as a causal minimal weld thickness, factor for this event using a detailed stress proximity to a weld-stop (stress analysis (Reference 36) riser) and the presence of operating vibration loads Root Cause Event 3: Latch CF5 - Cracking in the 220° Latch
  • The basis for the cause determination is Box Crack at Box - Per Ref. 18, the most likely the analysis and evaluation discussed in 220° azimuth cause of the cracking is fatigue Reference 18, which concludes that the cracking, the presence of a weld most likely cause of the cracking is the end discontinuity and likely high presence of a weld end discontinuity and weld residual stress at the corner likely high weld residual stress at the location. corner location.

Root Cause

  • The Lift Event was rejected as a causal factor for this event using a detailed stress analysis (Reference 36)

B. Discussion of the Basis for Cause Determination for Three RCA Events.

Event 1: Crack & deformation of dryer base plate and skirt.

1. CF1a, CF1b: - Lifting Event Causal Factors A. Lifting Event: The May 2005 Lifting Event where the dryer was damaged from impact of the skirt base ring with the RPV lugs was a causal factor that contributed to the dryer cracks discovered in Q2R18. An apparent cause evaluation (ACE) was completed and approved in May 2005. This RCA reviewed this ACE and determined it to be an appropriate starting point for further analysis to determine why the event occurred.

The ACE (AR 334383334383 concluded:

Two apparent causes were identified for this ACE. First, lack of clearance between the Dryer base ring plate and the Separator guide rods resulted in damage to the ring plate and shifting of the Dryer that caused minor damage to two of the seismic support blocks. Second, excessive clearance between the Dryer guide rods and the Dryer (guide slots) allowed the Dryer to move enough that the close tolerance notches in the Dryer skirt base ring plate no longer aligned with the RPV dryer hold-down lugs. This allowed the ring plate to catch on the underside of the lugs and result in deformation of the ring plate in three areas.

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This RCA considers the lack of clearance between the dryer skirt base ring and the separator guide rods to be an initiating event, but not a causal factor because the dryer is designed to be installed and removed as many times as needed to support plant operations. The interference with the separator guide rod was the reason for dryer removal in this case, but not the reason for the lift event. Therefore the next level of Why focused on the excessive clearance with the guide rods, and the close tolerances between the skirt base ring notches and the RPV lugs.

This RCA did consider the possibility that the cause of the impact was related to human performance issues with the crew removing the Dryer in Q2P03. This consideration arose from the fact that the U-2 Dryer was installed without damage twice during Q2P03, and removed once during Q2R18. (The Q2R18 removal was under the same configuration and close tolerances as Q2P03 since the modifications to improve this condition had not been completed yet). Information from interviews with personnel involved in the successful moves of the U-2 dryer, support a position that while the dryer can physically be removed under the configuration existing in Q2P03, the tolerances are such that an unacceptable risk of impact exists even with a reasonable measure of care.

This information coupled with the results of the previously approved ACE led to a conclusion that the causal factors of the lift event were more related to the hardware clearance issues than crew human performance. Therefore the RCA pursued a Cause and Effect Analysis on the changes to design of the dryer installation hardware which resulted in the increased clearance with the guide rods, and the close tolerances between the skirt base ring notches and the RPV lugs noted in the ACE.

Cause & Effects Analysis - Design Changes to Dryer Installation Hardware (CF1a)

1. What were the changes?

Dryer Guide Device Clearance: The previous dryer had two guide channels that ran the outside length of the dryer. Once the channel was engaged onto the RPV dryer guide rods, little movement occurred as the dryer was installed into the RPV. Similarly, these full-length channels allowed for less movement when the dryer was removed, when compared to the new dryer design that uses dryer guide slots at the top and bottom of the Dryer Skirt. On the replacement steam dryer there are only 4 points of contact between the dryer and guide rods: - two at 0 and 180° on the base ring, and: -two at 0 and 180° on the mid-support ring. When the mid-support ring is not engaged with the dryer guide rods (i.e, the support ring is higher than the top of the upper dryer guide rod brackets),

there are only 2 points of contact between the dryer and guide rods, at 0 and 180° on the base plate. Stated another way, only when the dryer base plate is 2 or more below the bottom of the RPV dryer support bracket (vessel lugs) will there be 4 points of contact.

Thus, there are only 2 points of contact between the dryer and guide rods any time the dryer base plate is at the same elevation as the RPV dryer support brackets (vessel lugs).

The dryer is therefore much less constrained in terms of the dryer/guide rod interface in the replacement design than it was in the original design, especially when the dryer base plate is at the same elevation as the RPV dryer support brackets (vessel lugs).

Skirt Base Ring Cutouts for RPV Support Lugs: The previous dryer used a channel mechanism to allow the dryer skirt to pass along the 4 RPV lugs. The new dryer design had cutouts at the skirt base ring that were nominally 4 inches wide to fit around a RPV Page 24 of 43

lug that is 3 inches wide. This allowed a one-inch margin (one half inch on each side) to install the dryer onto the RPV lugs.

2. Why were the changes made?

The new dryer installation project was completed to address past experiences with structural damage to the old dryer during operation at Extended Power Uprate (EPU) conditions. The new dryer was an original equipment manufacturer (OEM) replacement of a more structurally robust designed dryer. The reason the design was changed from full-length channels was to accommodate a change to relocate the drain channels from the inside of the dryer skirt to the outside of the dryer skirt. Since the OD of the dryer had to remain the same diameter so as to be able to fit in the vessel, the skirt diameter was reduced to make room for the drain channels on the outside of the skirt. The full-length guide rod channels that were previously an integral part of the skirt thus could no longer remain integral to the skirt. It was decided to not incorporate the full-length guide rod channels into the replacement dryer design and instead use the 4 points of contact design so as to minimize the weight increase of the replacement dryer. (As the dryer is made more structurally robust, the weight increases as heavier material is used, and the increased weight had to be maintained within the structural capabilities of the RPV dryer support lugs.)

3. Why were the potential adverse consequences to the installation hardware changes missed?

Barrier Analysis: The barriers expected to prevent adverse consequences from this design change included:

a. A design product provided by the vendor designer where all potential adverse consequences associated with the change are addressed.
b. Review and approval of the vendor provided product by Exelon design personnel using the process defined in CC-AA-10, Configuration Control Process Description and other associated procedures.
c. Review of the design product by the end user (in this case Reactor Services) to determine if there any adverse installation concerns created by the design change.

In this case the vendor providing the design product is GE, who was also the Original Equipment Manufacturer (OEM). Interviews with a GE design person indicated the use of slots versus channels was considered an acceptable option based on trouble free application of this design in the dryers of more recent vintages of GE BWRs. The GE designer believes that the use of slots in the new dryer was, and is acceptable, but in the case the QC2 dryer, was further degraded by the ovality fabrication issue.

Site design personnel review efforts were focused on structural factors, the instrumentation unique to this particular dryer, and similar technical items. The design engineers have little hands on experience with dryer installation. The Exelon Engineering Change (EC) review process accounts for this gap in hands on experience by using cross discipline reviews from personnel who do have this experience. In this design change, the end user, Reactor Services completed Att. 10F of CC-AA-102, Page 25 of 43

Configuration Change Review Checklist for Use by Other Departments indicating they understood and accepted the impact of this change on their department. Follow-up interviews with GE and Exelon Reactor Services personnel indicated that the change in installation hardware, and resulting closer installation tolerances, was a well-known issue. These personnel believed the change could be accommodated with additional care during installation. One example of this additional care was that during the initial installation, personnel were in the reactor refueling cavity bulkhead to closely watch the lowering load. This option was known to not be available in future Dryer installations since they are performed under water after the dryer has been exposed to operating conditions that elevate the radiological dose rates. The intent was to determine if the dryer could be successfully installed despite these tighter tolerances, and pursue modifications if needed for future installations.

This evaluation concluded that for these changes to the dryer installation hardware:

  • OEM (GE) personnel had provided the design for use in the Exelon EC process.
  • The design change process had been followed as specified in the governing procedures.
  • Appropriate end user personnel (in this case Reactor Services) had been included in the design change review.
  • These Reactor Services personnel had significant experience.

Despite these factors, unanticipated negative consequences occurred, that were associated with these design changes.

This evaluation pursued the organizational and programmatic factors that had influenced these negative results. At this point in this RCA, it was known that causal factors associated with this event shared some similarities with those of another recently approved RCA, an investigation of Electromatic Relief Valve Solenoid Failures (Ref.

38). A review of the corrective actions associated with the ERV RCA identified that several of these actions would be well positioned to address the weaknesses identified in this RCA.

Additionally, a second RCA QC2 Replacement Steam Dryer Impact on Fuel Analysis Results (Ref. 37) was reviewed. This RCA was completed in May 2005 when it was determined that the replacement dryers would not meet the design requirement for differential pressure (dP). This RCA contained corrective actions intended to reduce the probability of negative consequences associated with major design changes and projects.

Corrective actions will be needed to prevent recurrence of the dryer lifting event specific to the RCA (since dryer removal will occur each future refueling cycle). Actions will also be needed to address the organizational and programmatic issues that allowed the negative design change consequences to occur. The subsequent section, IX. Corrective Actions to Prevent Recurrence, and X. Corrective Actions, presents corrective actions associated with the lifting event.Section XII. Programmatic/ Organizational Issues details the corrective actions to address the more global concern related to preventing unanticipated negative outcomes of design changes.

Page 26 of 43

CF1b: Cause & Effects Analysis - Fabrication Induced Ovality The additional movement and reduced tolerances allowed by new installation hardware in the QC U-2 dryer was further degraded by a fabrication problem which resulted in the skirt being approximately 2 inches out of round (ovality issue). The orientation of the out of round position further allowed additional movement between the dryer guide slots and the RPV guide rods. The concern related to the ovality impacting installation clearances was recognized. The DDR (Ref. 7) resolving the ovality issue noted -

Dimensional analysis of the as-built hardware indicates that the dryer will fit in the vessel. Clearances normally available have been compromised, so additional guidance constraints will be placed in the lower guide block, to limit misalignment and assist in installation. The additional guidance constraints were in fact installed as documented in Ref. 9. These constraints helped reduce potential movement between the dryer and the vessel wall, but did not have any impact on lateral movement. It is believed that this lateral movement contributed to the lift event by allowing the dryer to rotate about one inch due to the slop between the dryer guide slots rods and the RPV dryer guide rods.

This minimal rotation contributed to the dryer skirt base cutouts for the RPV lugs, being out of alignment with the RPV lugs, which allowed for the skirt base plate to impact on the bottom of the reactor lugs as the dryer was being lifted out of the reactor vessel.

Note: Att. 7 contains more detailed descriptions and pictures regarding the movement of and damage to the U-2 Dryer during the Lifting Event.

CF2: Disposition of Lifting Event Prior to Start-up from Q2P03 Given that this RCA concludes that damage from the May 2005 (Q2P03) lifting event was a primary causal factor for the cracking identified during Q2R18 inspections, and the damage from this event was a known issue, it is logical to conclude that this disposition was a missed opportunity to prevent the dryer skirt cracking. This section describes the evaluation performed for potential causal factors associated with the reviews completed after the lifting event that occurred. The table below describes the major reviews and milestones that occurred, during and shortly after Q2P03.

Q2P03 Lift Event Follow-up Decision Timeline Date Time Event 5/11/05 2300 Lift event occurred (approx.)

05/12/05 0156 OCC notified 05/12/05 0700 Prompt Investigation Initiated (Ref. 4) 05/12/05 NA Exelon comment matrix for review of FDDR RMCN 06243 notes need to assess:

1. cold work and/or residual stress in the weld.
2. magnitude of the plastic strain to determine the Page 27 of 43

potential susceptibility.

05/13/05 ~0700 Liquid Penetrant testing performed on selected (prior to damaged and/or repaired areas of Dryer install) (Ref. 1) 05/13/05 0710 Dryer Repaired, Modified and set into the RPV 05/13/05 0900 Prompt Approved by MRC.

(assumed) 05/13/05 NA FDDR RMCN06245 Issued by GE to Resolve Lift Event Damage. Implemented under Exelon WO 742798-1 (Ref. 8) 05/14/05 NA PORC approval of EC 351168- Rev.2- incorporating FDDR RMCN 06243 into the Exelon EC process.

05/16/05 0345 U-2 Start-Up from Q2P03 05/24/05 NA Exelon Corporation concurrence letter for FDDR RMCN 06243 issued. (Ref. 30) 05/25/05 NA ACE on Lifting Event Approved by MRC (Ref. 2)

This RCA reached the following conclusions regarding the Q2P03 assessments of the lifting event:

1. There was no evidence of any formal review (HU-AA-1212, or similar process) to specify what areas of the Dryer areas were to be inspected after the lift event.

Non-destructive examination (NDE) personnel performed liquid penetrant examinations of damaged and or repaired areas at the direction of GE refuel floor supervision. (Ref. 1) These examinations included outside diameter areas, no inner diameter areas were inspected.

2. Only anecdotal evidence of evaluation of cold work or elastic strain impacts could be found. Personnel who were involved in the review of the GE FDDR (Ref. 8) recalled discussions of these topics, and conclusions that the ductile nature of stainless steel, and low stresses in the skirt/baseplate regions, made future problems unlikely. This RCA found no documented, formally reviewed structural analysis reports or evaluations completed prior to restart from Q2P03.

Formal structural analyses (Ref. 29&36), and metallurgical evaluations (Ref. 19), were completed as part of this RCA. Because these analyses could not identify the exact initiation mechanism of cracking, a detailed analysis during Q2P03 is unlikely to have changed the outcome, (formal analysis would have concluded the unit could be restarted without major replacement of dryer skirt components). For this reason, the weaknesses associated with the Q2P03 lifting event disposition are not considered a root cause to this event. The weaknesses are retained as a contributing cause because more detailed Page 28 of 43

inspections could have detected cracks in the skirt or base plate, specifically on the inner diameter areas. In addition, more detailed inspections in the inner diameter regions would have better identified the magnitude of the deformation, which may have resulted in a different conclusion of corrective actions needed.

Event 2: Crack found in vane bank of E bank near 320° azimuth The basis for the determination of minimal weld thickness, proximity to a weld-stop (stress riser) is photographic observation by the Quad Cities root cause team. Reference 17, Figure 1, last image, shows that the weld buildup is smaller than adjacent portions of the weld and also shows the weld-stop. Additionally, hood assembly and weld residual stresses may have been produced due to the alignment of 6 vane panels in the E hood and the weld shrinkage when welding the hood panels and gussets to the vane panel end plates and trough. (This results from differential thermal expansion and contraction that occur from the temperature difference between the weld bead and the cooler base metal.)

These factors are postulated to, in the presence of operating vibration loads, have initiated the crack.

Event 3: Latch Box Crack at 220° azimuth The basis for the cause determination is Reference 18, which notes that the crack appeared to have initiated at the corner where one latch box to skirt panel weld either began or ended. Also, the weld end appears to have a discontinuity in the form of a small crater. It is well known that the beginning or end of a weld bead could have some discontinuities that could serve as a fatigue crack initiation site. The other contributing factor could be the corner location where the two welds are meeting that could produce high fit up stress at that location. The presence of high weld residual stress could lower the fatigue stress threshold and may result in the initiation of a fatigue crack. Therefore, it is concluded that the most likely cause of the cracking is the presence of weld end discontinuity and likely high weld residual stress at corner location.

Page 29 of 43

C. Discussion of Evaluation of Other Conditions Conditions in the table below were determined to not be CFs for this event, but warrant additional discussion for clarity purposes, and to ensure priority issues are resolved even if they did not contribute to these events. The table summarizes these events. For some of the more complex issues, a more detailed discussion appears at the end of the table.

Condition Description Issues, Basis, Resolution C.1: Crane load cell unavailable.

  • Effect of not having load cell display available was not effectively resolved prior to the lifting evolution.
  • RCA inconclusive if load cell could have prevented event but there are clear opportunities to enhance the use of this barrier in future.
  • CAs specified in Other Section (More detailed discussion appears at the end of this table.)

C.2: Finite Element Model Did

  • RCA determined extensive issues in configuration Not Include Detail For New control between the as built replacement dryers and Dryer Design Below Water Line the GE analysis model (one example - base plate cut-outs were not included in analysis model).
  • Structural analysis associated with the RCA determined that this lack of configuration control did not contribute significantly to this event (Ref. 29)

(More detailed discussion appears at the end of this table.)

C.3: Metal Stress Inducing

  • Base plate and skirt gusset load concentration not Factors - Design: Used super modeled.

element model for new dryer

  • Analysis model did not include cutouts in the skirt base plate.
  • Structural analysis associated with the RCA determined that this lack of detailed analysis did not contribute significantly to this event (Ref. 29)

C.4. Metal Stress Inducing

  • Stress induced in the dryer skirt & skirt base plate due Factors - Fabrication: Distortion/ to two halves of dryer being force fit together, ovality of dryer base plate resulting in ovality of the skirt and skirt base plate.
  • Stress contribution to skirt cracking would be limited to elastic distortion of the base ring.
  • Impact of residual stresses was not specifically Page 30 of 43

Condition Description Issues, Basis, Resolution analyzed in Q2P03 because skirt is a low stress region.

  • A follow-up evaluation associated with this RCA (Ref. 33) was completed and concluded that the small plastic strain and residual stresses directly attributable to the ovality issue did not contribute to the observed cracking.

(More detailed discussion appears at the end of this table.)

C.5: Structural - Fabrication:

  • Dryer material sample showed a lack of weld Welding of base plate to dryer penetration at skirt and base plate connection skirt showed lack of penetration.
  • Metallugical Analysis completed for this RCA concluded that the lack of penetration was not completely unexpected for this type of weld. This analysis also concluded that this issue was not a causal factor for the observed cracking.
  • More detailed discussion and excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous Analysis section of this report and are not repeated here.

C.6: Structural - Fabrication:

  • Dryer material samples from both the 140° and 220° Use of halide containing weld regions indicated a presence of TGSCC.

wire coupled with cracking

  • Metallurgical Analysis completed for this RCA allowed SCC initiation. concluded that the TGSCC was not an initiating factor for the observed fatigue cracking. TGSCC in the 140° region was more extensive than the 220° region. It is believed this condition was caused by the water introduced to the area after the fatigue cracking occurred in the 140° area.
  • More detailed discussion and excerpts of Ref. 19, the GE Metallurgical Analysis were included in the previous Analysis section of this report and are not repeated here.

Page 31 of 43

C.1: Crane Load Cell Display Unavailable Allowing Excess Forces On Dryer The Reactor Building Overhead Crane (RBOC) is provided with a load cell that will sense the weight on the crane hook with an output signal to a crane power interlock switch. The set point of this switch is 250,000 lbs (125 ton), equal to the rated crane capacity. The load cell signal also provides input to a digital readout, which if properly calibrated, will provide the accurate weight of a lifted load. There is a primary readout on the control unit located on the crane trolley, which cannot be viewed remotely. There is, however, a secondary display that can be viewed from the crane operators cab as well as the refueling floor.

During the review of the Steam Dryer lift event on May 12, 2005 (Q2P03) it was determined that this lift was performed with a non-functioning digital readout display from the load cell (secondary display). (Note: The 125-ton crane power interlock was functional, only the display function was inoperable). Procedure QCMM 5800-05 Reactor Building Overhead Crane Utilization, Step 3.3.1 states:

if the readout does not display any digits, WRITE a Work Request for repair.

This does not render it inoperable if all view angles around the lift can be verified to ensure no interferences are encountered.

There is no evidence that a Work Request (WR) or an Issue Report (IR) was initiated at this time, however, a prior request was initiated on 4/21/05 (AR# 327007). This request (WR# 176082) was closed to WO# 805641-02 for calibration of the load cell and repair of the digital readout, which was completed on 5/16/05, approximately 4 days after the dryer lift event.

Per discussion with the contracted crane maintenance vendor, it is understood that the digital readout will provide accurate indication of a slight change in load ( 200 lbs) on the crane hook, which would be indicative of a load hang-up. It is also understood that monitoring of the load could easily be accomplished by using a dedicated person to watch the display for any increase in load indication. This person would be located near the signalman, thereby being within sight of the crane operator without distracting either the signalman or the crane operator from their respective load handling responsibilities. The person monitoring the load display can terminate the lift at any time a change in load is observed.

Based on the speed of the hoist in slow speed (< 2ft/min.) and reasonable reaction times by the load monitor and the operator, it is expected that the lift could be suspended with a minimal amount of load on the contact points due to hang-up of the load.

The ACE conducted at the time of the event (Ref. 2) concluded that since the rigging is a metal to metal contact throughout, any load cell deviations would be instantaneous and would not allow for operator action to prevent possible consequences This RCA, however concludes that had the load cell secondary readout been functioning and a dedicated person assigned to monitor and halt operation of the crane at a predefined criteria the damage could have been minimized.

The finite element analysis conducted to estimate the force necessary to permanently deform the skirt base ring 3/4 of an inch would be around 47,000 lbs. Since the load cell can sense load differences as small as 200 lbs., and the the skirt base plate would deflect Page 32 of 43

in an elastic manner at some lesser force before it would plastically deform to the 3/4 inch deflection, the lift could have been stopped prior to any permanent deflection.

During interviews, it was evident that the lack of a functioning load cell display had become an expected norm and the procedure had been written to allow the use of the RBOC without the load cell functional. It is also reasonable to conclude that with the heightened sensitivity to the dryer clearances due to the changes in design and to fabrication problems (ovality), that more emphasis should have been placed on the operation of the load cell.

C.2 Finite Element Model Did Not Include Adequate Detail For New Dryer Design A potential failure mode that was identified and subsequently rejected, was that the finite element model for the dryer could be inadequate for the new dryer design. If this allowed an inadequate margin condition to exist without the model showing the problem, then a design inadequacy would go undetected.

The evidence indicates that the cracks occurred primarily because of residual stresses associated with the dryer lift / impact event. Normally, the dryer modeling would not be used to ensure margin to mis-handling events, except possibly in very low dimensional clearance margin conditions such as this (where a user error is likely).

During RCA, several vulnerabilities were discovered, which the dryer model was not detailed enough to detect. One example is that the gussets placed adjacent to the notches in the base plate, could cause ring deflection(s) to be transferred to the skirt panels, allowing a cyclic loading. A second example was that the cutouts for the RPV lugs were not modeled. This prevented the opportunity to detect local stress conditions that may be present in the skirt or base ring in the vicinity of the cutout. Since the model did not detail these conditions, additional detailed finite element modeling was needed to better evaluate this possible cause.

Additional detailed finite element analysis (FEA) completed in a GE report titled Quad Cities Unit 2 Replacement Steam Dryer Analysis, Detailed Stress Analysis of Skirt Base Plate Cutouts and Gussets. (Ref. 29) concluded that:

The analysis results show that the effect of the cutout on the skirt response is insignificant and the original stress analysis without this detail is adequate. In addition, the fatigue stress levels at the cutout in the base ring for all configurations (original, as found, and repair design) are very low compared with the endurance limit of 13.6 ksi The inelastic analysis results show that the lug/base plate impact resulted in significant levels of irreversible plastic deformation that could have contributed to crack initiation due to a combination of residual stress inherent in plastically deformed structures and flow-induced vibratory stresses.

The conclusions of this analysis supports elimination of lack of detail in the FEA as a potential cause, and supports the RCA position that stresses from the lifting event were causal factors in Event 1.

Page 33 of 43

C.4. Metal Stress Inducing Factors - Distortion/ovality of dryer base plate (Ref 33)

GE completed additional analysis of this condition in support of this RCA. Excerpts of this analysis appear below, which support a position that stresses from ring ovality did not contribute to the events in this RCA:

Given the sequence of events, it is reasonable to conclude, as stated in the DDR disposition, that the distortion of the base ring was a consequence of welding the additional supports into the upper steam dryer structure. Weld shrinkage between the dryer banks could have transmitted a load into the skirt tending to make the structure, including the base ring, slightly oval. However, when considering the potential effects of this distortion relative to the failure observed at the 140º location, there are two important points. First, it should be recognized that, at 247 inches diameter and only one inch thick, the base ring is a relatively flexible component. Two inches deviation in a 247 inch diameter is only about 0.8%

diametral distortion, which represents neither significant working of the material nor residual stress. In fact, a large fraction of this projected maximum distortion of 0.8% is elastic rather than plastic deformation. Circumferential strain, which would be more indicative of permanent plastic deformation, is essentially a net of zero since the diameter is approximately the same amount undersize 90 degrees from the oversize points. In any event BWRVIP-84* allows up to 2.5%

permanent plastic strain for the purposes of straightening stainless steel components. The plastic strain attributable to the diametral distortion is much less than this limit.

The second consideration is that the failure occurred at the 140º azimuth, which is approximately midway between the minimum and maximum diameters.

Therefore, the failure occurred near a neutral point where the diametral distortion and stress would be minimal. However, it is recognized that in this region, especially in the cutout in the base ring, the balance between the oversize diameter and the undersize diameter would tend to produce some amount of bending of the ring. This produced some incremental amount of torsional load in the cutout region that would be additive to the overall stress applied in the failure location. Nevertheless, it is concluded the small plastic strain and residual stress directly attributable to the observed diametral deviation had no role in the failure.

Page 34 of 43

VI. Extent of Condition:

Cause being addressed Extent of Condition Review CF1a - Guide Channels The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam Not Used in New Dryer dryers also do not use channels. The modification to the Quad Cities Design Unit 2 (QC2) dryer of wider base ring slots has been incorporated into the design of these three dryers and the attention required during lift to the possibility of hanging up the dryer base ring on the dryer (RPV) support lugs has been communicated to Dresden, and will be communicated to the industry through the OPEX process.

CF1b - Ovality Results in The Quad Cities Unit 1 and Dresden Units 2 and 3 replacement steam Looser Installation dryers were/are constructed in two halves, shipped and welded Clearances together at J. T. Cullen. Measurements showed that the dryer skirt was oval following the welding. The looseness caused by the ovality is postulated to be an element in the dryer removal event. The lessons learned regarding rigging and welding to prevent the dryer from becoming oval have been incorporated in the fabrication of these three dryers.

CF2: Analysis & The evaluations, examinations and analyses performed immediately Inspections of Damage after the dryer lift event in Q2P03 did not have sufficient rigor. As from Q2P03 lift event noted in the Evaluation section, it is likely that these weaknesses, concluded use as is. GE especially in the analysis area, would not have changed the outcome FDDR, and site review of the event, however there is some finite possibility of a missed concluded: opportunity to prevent this event from this CF. The Programmatic/

Organizational issues associated with this CF are unlikely to be

  • Modify base ring for repeated in dryer components, given the limited population of similar separator guide rods dryers, but there are extent of condition concerns related to other RCA
  • Run for 1 cycle reports reviewed as part of this analysis. Several corrective actions
  • Repair/modify base recently initiated in these other RCA are well aligned with this CF, ring for RPV Lugs in and should be expected to have a positive impact on this concern.

Q2R18 These items will be addressed in more detail in the subsequent Corrective Actions section of this report.

CF3 - Data Collection Vibrations are present to a degree in all the Units. They are measured From Instrumented Dryer and used in the analyses or compared to analyzed levels.

Acoustic Loading @ 150 Consequently this should not be an issue for other stations / units.

Hz CF4 - Issue 2: Bank E Section 1 of Reference 19 reads in part: Following the discovery of End Plate Cracking cracking <in Gusset 19>, all remaining locations were inspected. All of the other gussets were found to be acceptable with no evidence of cracking. Therefore, it is concluded that this is an isolated incident.

CF5 - Issue 3: Steam Latch box protectors have been installed under EC 351167, Rev. 1 for Dryer Latch Box Cracking Unit 1 and EC 348286, Rev. 0 for Unit 2. No other latch boxes were found cracked during these installations.

Page 35 of 43

VII. Risk Assessment:

Plant-specific risk Basis for Determination consequence Industrial Safety - Although the load cell display was not functioning, the circuitry does not Minimal Risk allow a lift of over 125 tons nominal. Given the safety factor of 5 required for the crane and other lifting members, the members would have been able to withstand the load up to the crane lift cutout without failing.

Nuclear Safety - Dryer component cracking could result in lost parts. Various lost parts Minimal Risk analyses have been performed in the past (most recently for a steam dryer 94 lb. lifting lug for Unit 1 and a steam dryer 9 x 6 plate for Unit 2). The most significant consequence has been determined to be a risk to production. No risks to nuclear safety have been found. Additionally, the Quad Cities Risk Management Expert and the Corporate Model Owner have reviewed the Steam Dryer Gusset Cracking Condition (IR 473034), the Steam Dryer Skirt Cracking Condition (IR 472321) and GE-NE-0000-0052-6385-R0, Lost Parts Analysis for Dryer Lifting Lug and Dryer Skirt Panel Unit 1, to provide support for the PRA modeling. Basically, the risk assessment review found the risk increase associated with these conditions to be minimal and not risk significant, as documented in Reference 26.

Regulatory Impact There is Regulatory Impact from the standpoint that the Station has assured

- Minimal Risk the Regulator that a more robust dryer has been installed, that the loading on the dryer is understood, the dryer has been shown analytically to be able to withstand the loading and that there should be no cracking of the dryer.

However, dryer cracking was found during Q2R18, resulting in a decrease in the credibility of the Station with the Regulator. Note that the dryers are non-safety related, seismically designed. Due to the location of the cracking and the measure strain hardening of the dryer material, the cause of the cracking is judged to be the lift event. Inspection of the Unit 1 dryer during Q1M19 determined that this undamaged dryer did not have cracking comparable to the Unit 2 dryer supporting the conclusion that the dryers were designed adequate to withstand the loads (minus a lifting event) as committed to the Regulators.

Production / Cost - Based on the following, there is minimal likelihood of recurrence of this dryer Minimal Risk cracking event:

a. GEs root cause analysis of the dryer 140° skirt cracking, Reference 21, identifies the lift event and consequent material strain hardening as the probable cause,
b. Dryer analysis using measured vibration loads and confirmed using strain gages shows that the dryer is able to withstand the operating loadings and
c. The Unit 1 dryer (without a lift event) as-found condition following approximately 10 months of operation, about 1/2 that time at EPU power levels, was acceptable and as expected.

Page 36 of 43

VIII. Previous Events:

Previous Events Previous Event Review None Many OPEX reports were found that identified cracking and most of them identified flow induced vibration or undersized welds as the cause. No case was found of dryer damage due to or during lifting of the dryer.

IX. Corrective Actions to Prevent Recurrence (CAPRs):

Corrective Action to Prevent Recurrence Root Cause Being Addressed Owner Due Date (CAPR)

CF1a - Guide Channels CAPR 1 - Modifications to improve Completed Completed Not Used in New Dryer installation hardware on U-2 Dryer during Q2R18 Design [i.e., increased lead-in on dryer mounting blocks, install lug spacer blocks, etc.] - EC 348286, Rev. 1 CAPR 2 - Modifications to improve installation hardware on U-1 Dryer

{i.e., enlarging base ring RPV lug Completed Completed cutouts) - EC 351167, Rev. 1 during Q1R18 CF1b - Ovality Results in CAPR 3 - Modifications to improve Completed Completed Looser Installation installation hardware on U-2 Dryer during Q2R18 Clearances [i.e., guide rod block extension] - EC 348286, Rev. 1 CF4- Vane Bank E End CAPR 4 - Analysis to justify leave Completed Completed Plate crack, caused by as is position (Ref. 17). during Q2R18 little metal between end plates, and proximity to a weld transition (stress riser).

CF5- Latch Box cracking CAPR 5 - Repair to this area. - EC Completed Completed at 220°, caused by high 348286, Rev. 1 during Q2R18 residual weld stress from weld end discontinuity and corner location.

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X. Corrective Actions:

Cause Being Addressed Corrective Action (CA) or Action Item (ACIT) Owner Due Date CF2: Analysis & This RCA concluded that recently See ATT. 9 See Att. 9 Inspections of Damage approved corrective actions for a from Q2P03 lift event RCA related to Quad Cities concluded use as is. Electromatic Relief Valve Solenoid (Lack of rigor in analysis, Actuator Failures (Ref. 38) are limited follow-up well aligned with CF2 for this RCA, inspections.) and are appropriate corrective actions for this RCA. The corrective actions are comprehensive, and will establish revised programmatic controls to ensure additional rigor is applied to situations similar to the Lifting Event.

These corrective actions are provided as ATT. 9 to this RCA.

CF3 - Operating Loads on Unit 2 - Install Acoustic Side Complete Completed Dryers During EPU Branches (ASBs) to reduce vibration during Q2R18 Conditions levels - EC 359004, Rev. 1 Unit 1 - Install Acoustic Side A8452DEM AT 435858-Branches (ASBs) to reduce vibration 37 due levels - EC 359006, Rev. 1 05/26/2006 XI. Effectiveness Reviews (EFRs):

CAPR / CA being addressed Effectiveness Review Action Owner Due Date CAPR 1 & 3 - Remove and re-install the U-2 Rx. services. Q2R19 Modifications to improve replacement dryer during Q2R19. May 2008 installation hardware on U-2 Verify that available clearances are Dryer [i.e., increased lead-in acceptable to prevent damage during on dryer mounting blocks, future dryer installation and removal install lug spacer blocks, activities. The U-2 dryer was modified etc.] - EC 348286, Rev. 1 with improved installation hardware in Q2R18. The U-2 Dryer is slightly different from U-1 due to the ovality issue. This action will validate the effectiveness of CAPR 1 & 3.

AT 472321 - XX (est. after RCA approval)

Page 38 of 43

CAPR 2 - Modifications to Remove and re-install the U-1 Rx. services Completed in Q1M19: No dryer improve installation replacement dryer during Q1M19. The removal or hardware on U-1 Dryer U-1 dryer was previously modified installation

{i.e., enlarging base ring with improved installation hardware in problems encountered.

RPV lug cutouts) - EC May 2005. This action will validate 351167, Rev. 1 effectiveness of CAPR 2 by demonstrating that the dryer can be removed and installed without damage.

Validates major RCA Inspection of the U-1 replacement Programs Completed Engineering Q1M19:

conclusions regarding cause dryer during Q1M19 concluded: Confirmed no of 3 cracking events in the 1) U-1 does not exhibit the skirt- similar damage to U-2 Dryer. (CFs 1a & 1b- U-1 Dryer cracking present on U-2 during Q2R18 for Event 1, CF4 for Event which supports the position of this (Ref. 39) 2, CF5 for Event 3) RCA that the U-2 lifting event was the cause for the skirt cracking.

2) No evidence Vane Bank or Latch Box cracking which supports position that Events 1 & 2 of this RCA do not represent generic design weaknesses or operating cycle concerns for the replacement dryers.

CAPR 4 - Analysis to Future inspections in Vane Bank E A8451NESPR During justify leaving Vane Bank area during next U-2 outage to verify Q2R19 E cracking as is (Ref. condition remains acceptable to leave [5/31/2008]

17). as is.

AT 472321 - XX (est. after RCA approval)

CAPR 5 - Repair to Latch Future inspections in Latch Box area A8451NESPR During Box cracking at 220° - EC during next U-2 outage to verify repair Q2R19 348286, Rev. 1 completed in Q2R18 was successful in [5/31/2008]

preventing future cracking.

AT 472321 - XX (est. after RCA approval)

XII. Programmatic/Organizational Issues:

This RCA identified two programmatic/organizational issues:

A. The original disposition of the lifting event in Q2P03 (May 2005) lacked rigor, and was potentially a missed opportunity to prevent the dryer skirt cracking.

B. Multiple examples of unanticipated negative consequences from the replacement dryer design.

Page 39 of 43

Item A, the original disposition of the lifting event, has been extensively discussed in previous sections of this RCA since it is considered a contributing cause to these events (CF2). As such, there is no need for additional clarifying discussion in this section. Item B, related to unanticipated negative consequences of the replacement dryer design change, will be discussed in more detail to provide specific examples and to clarify the impacts of this issue.

Both issues are included in the table at the end of this section, which summarizes the issue and associated corrective actions.

Unanticipated Negative Design Consequences:

This RCA noted several examples of negative consequences from the design of the replacement dryer. This includes:

1. Separator guide rod interference with the dryer skirt ring. This issue resulted when the replacement dryer design did not ensure that fit-up problems did not exist. This issue became an initiating factor for the lifting event.
2. The change in dryer installation hardware from full-length guide channels to guide slots and base ring cutouts was a causal factor (CF1a) for the lifting event.

This issue resulted when the potential negative consequences of the design change were not identified despite completing the requirements of the design change process, and associated cross disciple reviews.

3. The initial response to the ovality issue included a modification to install guide rod spacer blocks (Ref. 9) to address clearance concerns. This initial modification was completed prior to dryer installation, but was insufficient to prevent the ovality problem from becoming a causal factor (CF1b) for the lifting event.
4. The replacement dryer differential pressure (dP) did not match the design specified value. This issue was the subject of a separate RCA - Ref. 37. The unexpectedly low dP of the replacement dryer dP had negative impacts of: a)

Increased complexity and costs associated with fuel analysis for subsequent operating cycles, and b) Degraded moisture carryover performance from the new dryers.

The number of unanticipated negative consequences from the replacement dryer design clearly demonstrate a programmatic and organizational weakness. The consequences of these items clearly warrant corrective action.

As noted in the Evaluation section, the issue of unanticipated negative design consequences identified in this RCA shared some similarities with two other RCAs:

  • Electromatic Relief Valve Solenoid Failures (Ref. 38).
  • QC2 Replacement Steam Dryer Impact on Fuel Analysis Results (Ref. 37)

A review of the corrective actions associated with these RCAs identified that several of the items in progress would be well positioned to address the issue identified in this RCA.

Page 40 of 43

Attachment 9, section B., lists these corrective actions already tracked by ATs under Refs. 37 & 38.

In September of 2005 a Common Cause Analysis (CCA) was completed on modifications (AR 317566317566 which identified a need to improve the effectiveness of inter-departmental reviews associated with the design change process. Corrective actions associated with the CCA were implemented in fall 2005, so they would not have impacted the events of this RCA, which occurred in May 2005. A follow-up action is recommended to perform an effectiveness review of the CCA corrective action implementation to determine if they have been successful in improving the use of the inter-departmental reviews in identifying and avoiding unanticipated negative consequences of design changes.

Section B of the table below summarizes the intent of the actions in progress from the other RCAs and lists the actions to be tracked under this RCA.

Programmatic and Organizational Corrective Action (CA) or Action Item (ACIT) Owner Due Date Weaknesses Item A: Review & Disposition As noted in the previous Corrective See ATT. 9 See ATT. 9 of Lifting Event Damage Actions section, this CF will be During Q2P03 addressed by recently approved corrective actions associated with the ERV Actuator RCA.

These actions are intended to improve the application of formal decision-making processes under conditions similar to the lift event in this RCA. Formal decision making processes will enhance the level of rigor. These actions are listed in Att.

9, Section A of this RCA.

Page 41 of 43

Programmatic and Organizational Corrective Action (CA) or Action Item (ACIT) Owner Due Date Weaknesses Item B: Unanticipated Similar issues identified and tracked under See ATT. 9 See ATT. 9 other RCAs (Refs. 37 & 38) are listed in Negative Design Att. 9. These CAs are expected to improve Consequences the effectiveness of inter-departmental reviews of design changes, and to improve the coordination of major modifications that become Exelon projects. New CAs specific to this RCA are listed below.

1. Quad Cities to implement Rev. 1 of HU-AA-1212, Technical Task Risk/ Rigor A8400PM -

07/31/06 Assessment which includes guidance on QDCDW how to select what type of third-party AT 472321 review(s) are required. - XX (ACIT)

2. Design Eng. to complete an effectiveness review (EFR) of the corrective actions A8452 11/17/06 (CAs) implemented from CCA 317566. NESDP The overall intent of this EFR is to determine AT 472321 if the CAs have improved the use of the

- XX (ACIT) inter-departmental reviews in identifying (est. after RCA and avoiding unanticipated negative approval) consequences of design changes.

(An example directly from this RCA would be: More detailed Reactor Services review

& challenge to ensure the design is usable for dryer installation activities.)

XIII. Other Issues:

Other Issues identified during Corrective Action (CA) or Action Item Owner Due Date investigation (ACIT)

1. Crane load cell unavailable a. Evaluate methods to improve Rx. Services 11/10/06 during Lifting Event the use of the load cell as a method of early detection of load AT 472321 -

hang up. This needs to include XX (ACIT) establishing expected load values, (est. after RCA and abort criteria when pre- approval) established thresholds are reached. These methods should be incorporated in to QCMM 5800-05, or other suitable Page 42 of 43

Other Issues identified during Corrective Action (CA) or Action Item Owner Due Date investigation (ACIT) documents. These methods should also discuss appropriate contingencies if the load cell is unavailable, and suitable management review and approval levels for invoking these contingencies. Results of this evaluation should be presented to MRC for closure.

2. Crane load cell unavailable b. Evaluate historical reliability Plant 09/29/06 during Lifting Event of RB Overhead Crane Load cell Engineering.

display. Determine if actions for AT 472321 -

improving future reliability are XX (ACIT) (est.

after RCA warranted. Present results of this approval) evaluation to PHC for closure.

XIV. Communications Plan: Preliminary NER and OPEX information has already been provided for communication within Exelon and the Nuclear Industry. Final communication actions are being tracked by the AT items below:

Lessons Learned to be Communicated Communication Plan Action Owner Due Date Provide NER to share lessons 472321-09 A8430TP 06/01/06 learned within Exelon Provide an OPEX to share lessons learned with the rest of 472321-10 A8401OPEX 06/08/06 the industry Page 43 of 43

Lifting Eye (1 of 4)

Lifting Rod (1 of 4)

Mounting Block for Latch Assembly (1 of 4)

Dryer Guide Slots Skirt Base Ring Skirt Dryer Support Ring Drain Channel Cut-Out for RPV Lug (1 of 4)

Figure 1: Steam Dryer

Separator Guide Rod Cutout 0o (2 Locations) 320o 20o 40o 5/16 Bend RPV Lug Cutout (4 Locations) 270o 90o 220o o 140o 200 180o 5/8 Bend 3/4 Bend Impact on RPV Dryer Support Lug Figure 2 Steam Dryer Plan - Impact Locations

Design & Analyses of Fabrication of New Steam Dryer Fabrication - Upper & Lower Installation - Dryer is Lowered New Steam Dryer Upper & Lower Halves Halves Welded Together Into QC2 Reactor Vessel 2004-2005 @ U. S. Tool & Die @ J. T. Cullen WO 00732708-01 A Prior to March 2005 March 2005 5/11/2005 Dryer Loading is High A Large Amount of Welding Laser measurement of assembled Cycle Flow Induced is Required to be Performed dryer determines base plate is Guides on the dryer support ring Vibrations to Assemble the Dryer Parts approx. 2 inches out of round impact the RPV Dryer Support Lugs 4/4/2005 on the way down & bend the spacer blocks.

GE Used Super-Element to Weld NDE Records Lost for Model Skirt Below Water 300 welds - Consequently, CF1b Line - Detail of Lower Skirt Needed to use Reduced Weld Area Not Developed Capacity for Analysis Results in Looser Results in Dryer base ring hits steam Installation Increased Residual separator guide rods. Dryer can Hardware Clearances Stress not be lowered any further.

Planned Full Penetration Weld Revised to Partial Penetration Plus Fillet Weld On Both Sides of Skirt Plate DDR 431002828-027 (Ref. 7) Dispositions the Nonconformance Use-As-Is with Additional Guidance Constraints Added to the Lower Guide Block.

CF1a Guide Channels Not Used in New Dryer Design GE issued FDI 085 to install new guide rod spacer blocks and gusset supports.

5/4/2005 Cut Out For RPV Dryer Support Lug Judged Acceptable Based On Low Stress in Model ATT. 1: 472321-02 Root Cause Report Effect and Casual Factor (E&CF) Chart Att. Page 1

Installation - Decision made Disposition of Dryer Operating Cycle: U2 @ Removal of Dryer from to remove dryer from vessel Installation Issue and EPU Power Level vessel in Q2R18 A 5/12/2005 Damage (2800-2900 MWth) 3/28/2006 5/21/05 to 12/30/05 Event 2 Event 3 AR 473034: Dryer AR 475369:

CF3 Event 1 Cracking in Gusset Steam Dryer While removing dryer CF2 AR 472321: Cracking in 19 of Vane Bank E from vessel, the dryer base Steam Dryer 220° Latch Box Data Collection From End Plate Near the ring hangs up on the Lower Skirt vessel dryer support lugs. Instrumented Dryer 320° Location.

ACE, GE FDDR, and Acoustic Loading @ 150 Cracked @ 140° analysis concluded to: Hz Location

  • Modify base ring for separator guide rods RB Overhead Crane was
  • Run for 1 cycle used w/o functioning
  • Repair/modify base ring 4/2006: No Cracking load cell. for RPV Lugs in Q2R18 Identified at 220o Skirt Most probable cause is having Location (Similar very little weld metal between Deformation) or 320o the End Plates, proximity to a Location (Less Deformation)

Weld Transition (Stress Riser)

When the dryer became stuck, and the Presence of Operating the crane was required to Vibration Loads place a force onto the dryer that caused an audible noise. Extent of NDE and Evaluation Lacked 4/2006: Metallurgical Rigor for Disposition of Evaluation results of Boat Samples show the crack was CF4 Damage due to High Cycle Fatigue IR 334383: Dryer Base Ring found damaged. Inspections note weld end 5/12/2005 discontinuity near the area Metallurgical Evaluation of cracking. Most of Skirt to Base Plate probable cause is high Weld shows Lack of residual weld stress from Fusion weld end discontinuity and corner location.

ACE 334383-03:

New Dryer Design:

  • Did Not Consider Metallurgical Evaluation CF5 Separator Guide Rods of Skirt to Base Plate Joint
  • Did Not Adequately Identified Transgranular Address Fit-Up Cracking 5/25/2005 ATT. 1: 472321-02 Root Cause Report Effect and Casual Factor (E&CF) Chart Att. Page 2

- Event Timeline:

DATE EVENT/ ACTION SOURCE COMMENTS DOCUMENT(S)

Prior to Upper and lower halves of

  • NR - common None 3/2005 dryer are fabricated at U.S. information.

Tool and Die in Pittsburgh, PA 3/2005 Upper and lower halves of

  • NR - common None dryer are welded together information at J. T. Cullen, Fulton, IL 4/4/2005 Washington Group begins
  • Integrated Steam None laser measurements of Dryer Project J.T.

Assembled Dryer at J. T. Cullen Cullen Fabrication Facility Daily Activity Sheet 4/14/2005 QC2 Dryer Base plate is

  • DDR 431002828- Disposition provided 4/25/2005, approximately 2 inches out 027 states, Clearances normally of round.
  • EC 351168 available have been compromised, so additional guidance constraints will be placed on the lower guide block to limit misalignment and assist in installation.

5/4/2005 GE issues FDI to install

  • FDI 0085 Modification of replacement steam new guide rod spacer dryer to install additional guidance blocks and gusset supports. constraints 5/11/2005 Lower Dryer into Vessel
  • FDDR RMCN way down & bent the 06252 spacer blocks 5/11/2005 Hit Steam Separator Guide

Rod with Dryer Base Ring -

  • FDDR RMCN 1. Lack of clearance between dryer any further 06243 base ring and separator guide
  • Separator Guide rods due to wider skirt base ring Rod Interference plate (same OD, smaller ID).

Root Cause 2. Excessive clearance between Summary (Report dryer guide rods and the dryer.

Number AI10139)

  • Apparent Cause
  • Root Cause Investigation (AR Evaluation (ACE) 00330331-03) was supposed 334348 to address Steam Dryer design (but did not).
  • Poor Design was only cause Corrective Action per ACE:
  • Modify dryer per EC 348286 (see 26A6787 Rev. 2 3/7/06) 5/12/2005 Decision made to remove

DATE EVENT/ ACTION SOURCE COMMENTS DOCUMENT(S) 5/12/2005 While removing dryer from

  • FDDR RMCN support lugs - Lift Event 06245
  • Prompt Inv.

Report 5/13/2005 Reinstallation of dryer into

5/16/2005 Repair of the Reactor

  • WO 00805641-02 Building Overhead Crane Load Cell 5/16/2005 Operated at EPU and Pre-Q2C18 EPU power levels NR - common information 3/28/2006 U-2 Steam Dryer Lifting

Lugs Rotated

  • Operability Eval.
  1. EC 360272 3/28/2006 Removal of dryer from

3/29/2006 U-2 Steam Dryer Lower

  • WO 00794824-01 Root Cause Investigation Requested Skirt Cracked @ 140°

- References Ref. Document Title / Description

  1. Reference Number 1 WO 00732708-01 Replace Unit-2 Steam Dryer Per EC 351168 EC 351168 2 AR 334383334383 May 2005, ACE on Q2P03 Dryer Lifting Event 3 FDDR RMCN GE disposition of steam dryer interferences between the vessel 06252 steam dryer support lug and the lug spacer block.

4 AR 334348334348 May 2005 Prompt Investigation of Q2P03 Dryer Lifting Event 5 FDDR RMCN GE disposition of Steam Separator Guide Rod Interference 06243 with the Base Ring of the Steam Dryer Skirt.

6 GE Report Number GE Root Cause Summary: Separator Guide Rod Interference AI10139 7 DDR 431002828- GE Disposition of Ovality Issue: Steam Dryer Final 027 Dimension Approximately 2 Inches Out of Round.

8 FDDR RMCN GE disposition of May 2205, Q2P03 Lift Event 06245 9 FDI 0085, Rev. 0 Engineering requirements and instructions for the and Rev. 1 modifications of the replacement steam dryer to be installed at QC Unit 2 prior to the Q2P03 dryer replacement outage.

(Modified Jack Bolts, Installed Guide Rod Spacer Blocks, and Gusset Supports.)

10 AR 472321472321 Q2R18 Identified Crack In The U2 Steam Dryer Skirt.

(Event 1 of this RCA.)

11 INR Q2R18-IVVI- Steam Dryer Skirt @135 Degrees 06-02 (Note: Most Later References Specify 140°)

12 AR 473034473034 Q2R18 IVVI - Indications on Steam Dryer Gusset (E-Bank End Plate Crack). (Event 2 of this RCA.)

13 INR Q2R18-IVVI- Steam Dryer Bank E ID 06-04 14 AR 475369475369 Q2R18 Identified 220 Degree Latch Box Crack (Event 3 of this RCA) 15 INR Q2R18-IVVI- 220 Degree Latch Box Crack 06-29 16 GENE 0000-0053- GE Review of Transgranular Stress Corrosion Cracking in 1962 Skirt to Base Weld Root Area 17 GE-NE-0000-0052- GE Evaluation of the Bank E Drying Vane End Plate Crack 9728 (Event 2 of this RCA.)

18 GE-NE-0000-0053- QC U-2 Replacement Steam Dryer Analysis Evaluation of 0232 Latch Box Cracking and Fatigue Impact of Swing Arm &

Latch Protector Welds (Event 3 of this RCA) 19 GE-NE-0000-0052- QC U-2 Replacement Steam Dryer Metallurgical Evaluation 9666 ATT. Page 5

Ref. Document Title / Description

  1. Reference Number 20 GE-NE-0000-0052- Lost Parts Analysis for Potential Lost Dryer Lifting Eye and 6385-RO Dryer Skirt Panel Quad Cities U-1 GE-NE-0000-0053- Root Cause Analysis for QC2 Steam Dryer 140° Skirt 21 2926 Cracking (Event 1 of this RCA) 22 DDR dated Dryer Support Ring 3/8 Out of Flat due to Welding 02/20/2005 Distortion.

23 GE LFW0505-2, Quad Cities U-1&2 Replacement Dryer Skirt Cutouts:

May 20, 2005, DRF (Discusses modifications needed to both U-1 and U-2 0000-0034-3781 replacement dryers as a result of Q2P03 Issues.)

24 GE Transmittal No. As-Built Dimensional Analysis, QC-2 Steam Dryer (Report JXD4E-023 dated describing why the U-2 Replacement Dryer will fit in the 4/28/2005 vessel despite the ovality issue) 25 GE-NE-0000-0034- Replacement Steam Dryer Reactor Vessel Bracket Stress 4803-02 Report for Quad Cities 1,2 and Dresden 2,3, April 2005.

RM Documentation Risk Assessment for IR 473034 and IR 472321, Steam Dryer 26 No. SA-1477 Gusset Cracking and Steam Dryer Skirt Cracking, Assignment 03 Root Cause Report.

27 GENE 0000-0052- GE Steam Dryer - Recommendation for Repairs at 220 ° &

8407 & 8408 320° Locations (2 documents - same topic) 28 FDDR Q2R18 Addition of Dryer Guide Rod Block Extensions RMCN08436 29 GE-NE-0000-0053- QC U-2 Replacement Steam Dryer Analysis Detailed Stress 2910 Analysis of Skirt Base Plate Cutout and Gussets, April 2006 30 Exelon-ENG-DRY- Exelon Concurrence with GE Resolution of U-2 Steam Dryer 099CR Collision Damage. Dated May 24, 2005.

31 GENE-0000-0052- Q2R18 Steam Dryer ID Welds Flaw Evaluation, April 2006.

7988 Rev. 2 32 FDDR Ring and Skirt Assembly, dated 04/05/06. (Specifications RMCN08404 and drawings for repair to 220° area.)

33 GENE 0000-0053- QC2 Steam Dryer - Base Ring Diametral Distortion 0605-1 (April 2006 re-assessment of ovality issue) 34 GENE 0000-0053- QC2 Steam Dryer Repair Crevice Assessment (Discussion of 0606 acceptability of skirt plate repairs using backing rings).

35 GENE 0000-0043- QC U-2 Replacement Steam Dryer Stress and Fatigue Analysis 3105-01-P Based on Measured EPU Conditions (July 2005) 36 GE-NE-0000-0053- QC U-2 Replacement Steam Dryer Analysis Detailed Stress 2456-P Analysis of Dryer Lifting (April 2006) 37 AR 330331330331 RCA: QC2 Replacement Steam Dryer Impact on Fuel Analysis Results 38 AR 435858435858 RCA: Electromatic Relief Valve Solenoid Actuator Failures due to failure to correct the source of the MSL vibrations 39 EC 360876 Review of Q1M19 Critical Steam Dryer Inspection Findings ATT. Page 6

Ref. Document Title / Description

  1. Reference Number 40 GENE 0000-0053- Request for Additional Information: QC U-2 Dryer Inspection, 2954, Revision 1 Start-up & Power Ascension Plan - RAI 9 (b):

Discussion of the corresponding reduction in the fatigue stress limits in the Dryer Skirt Crack.

41 Ref. 3 used in GENE Manjoine, M.J. and Tome, R.E., "Proposed Design Criteria for 0000-0053-2954, High Cycle Fatigue of Austenitic Stainless Steels,"

Rev. 1 - RCA Ref. 40 (above)

International Conference on Advances in Life Prediction Methods, ASME, 1983, pp. 51-57.

ATT. Page 7

Comparison of QC 2 Replacement Steam Dryer Pressure Sensor Data with Q2R18 Dryer Damage.

Reason For Evaluation / Scope:

Note: The references in this attachment refer to the items listed on the final page of this attachment, not the RCA Report references listed in Att. 3 Quad Cities Unit 2 (Q2) new steam dryer was installed in May 2005 under EC 351168 (Ref. 1). During installation of the new steam dryer, AR 334348334348(Ref. 2) identified that the new steam dryer would not sit in the dryer guides properly. The dryer was repaired and the skirt base plate deflection was documented in GE Traveler (Ref. 3). The skirt base plate deflection at the 1400 AZ location is 3/4, at 2200 AZ location: 5/8, and at 3200 location: 5/16. At the 400 AZ location, no plastic deformation of the skirt base plate was noted. At 1400 AZ, the skirt base plate cutout plastically deformed 3/4 downward with visible inside diameter (ID) deformation and skirt panel with dimple at top of gusset. At 2200 AZ, the skirt base plate was deformed 5/8 downward with visible ID deformation and no evidence of dimpling. At 3200 AZ, the skirt base plate was deformed 5/16 downward with imperceptible plastic ID deformation Q2 steam dryer is instrumented with strain gages, pressure sensors, and accelerometers.

GE Specification 26A6395 (Ref. 4), sheets 15, 16, 17, and 18 provides the sensor locations with respect to the Dryer orientation in the reactor vessel and its relative elevations. During unit start up testing to full power, AR 347867347867(Ref. 5) identified that various strain gages and accelerometers were failing. After completion of the testing, Q2 ran at full power for > 200 days before coming down for a planned refueling outage (Q2R18).

Further, inspection of the steam dryer in Q2R18 indicated damage to the dryer skirt (AR 472321472321 (Ref. 6) and dryer lifting lugs rotated (AR 471848471848 (Ref. 7). The #7 skirt panel and base plate at cutout cracked after ~200 days of EPU operation. At 25 Hz, the skirt base plate and the skirt panel #7 have undergone 4.3e08 cycles Purpose of this evaluation is to a) review Q2 start up test data and compare it with the damage seen on the steam dryer skirt at locations close to the main steam lines (MSL) and b) to see whether the as-built/as-installed dryer with known damage to the skirt base plate could affect the pressure distribution in the steam space external to the dryer and affect the main steam line frequency patterns at the full load operation of the unit.

Detailed Evaluation:

The new steam dryer orientation was taken from reference 4, sheet 17. Drawing M-3121 (Ref. 8) identifies main steam line nozzle orientation. It should be noted that A MS nozzle at 700 is closest to 400 dryer skirt base plate cutout. Similarly, B MS nozzle at 1100 is closest to 1400 dryer skirt base plate cutout; C MS nozzle at 2500 is closest to 2200 dryer skirt base plate cutout; and D MS nozzle at 2900 is closest to 3200 dryer skirt base plate cutout.

ATT. Page 8

Following Table shows the pressure sensors located external to the steam dryer, MSL locations, and other pertinent data. Also, Document Number AM-2005-012 (Ref. 9) shows actual pressure data taken from Quad Cities Unit 2 start up testing. This pressure data is used in developing the overall evaluation.

  • Q2 dryer pressure sensor locations:
  • P3 A hood, opposite B MS nozzle.
  • P22, P24, & P25 skirt below B MS nozzle.
  • P12 A hood, opposite A MS nozzle.
  • P20 F hood, opposite C MS nozzle.
  • P21 F hood, opposite D MS nozzle.
  • P15 & P17, hood Closure Plate- B & C hoods.

TABLE No.

1 Main Steam Line (Ref. 8) A A B B C D 2 MSL Azimuth 700 700 1100 1100 2200 2900 3 Dryer Skirt Base Plate 400 400 1400 1400 2200 3200 Cutout Location 4 Initial Skirt Base Plate None None 3/4 Inch 3/4 Inch 5/8 Inch 5/16 Inch Damage 5 External Pressure Sensors P12 N/A P3 N/A P20 P21 on Dryer 6 External Pressure Sensors N/A P25 N/A P22 N/A N/A on Dryer Skirt above Water Line 7 Min. Pressure, psi -2.069 -1.270 -1.887 -1.379 -1.613 -2.261 (Ref. 9) 8 Max. Pressure, psi 1.907 1.166 1.817 1.243 1.588 2.099 (Ref. 9) 9 Pressure, psi 3.976 2.436 3.704 2.622 3.201 4.360 10 RMS Pressure Measured, 0.69 0.344 0.631 0.422 0.499 0.883 psi (Ref. 9) 11 ERV(s) on MSL 2-0203-3B & 2-0203-3C 2-0203-3D 2-0203-3E 12 ARs on ERV None 435838 435838 430555 and 435838 Conclusions/Recommendations:

a) Review of reference 4 shows pressure sensor locations on the dryer from higher to lower elevation in the following order: P1, P2, P3, P22, and P24. Further review of this reference shows that the pressure sensors P3, P6, P9, P12, P15, and P17 are located 65 below the top of Bank A. Review of the pressure data from reference 9 for these sensors indicate that pressure reduces when moving downward and when moving away from steam nozzles. Pressure at 1400 location (P3) is lower than pressure at 700 or 2900 ATT. Page 9

locations (P12 and PP21). Skirt pressures are lower than hood pressures as seen from pressure sensor data of P22, P25, P3, and P12. Steam pressure measured at the skirt (P25 and P22) is lower by order of two when compared with the pressures measured at the hood (P12 and P3). Further, the Table shows that steam pressure will be highest for the D MSL nozzle, then A, B and the lowest steam pressure will be at C MSL nozzle. (i.e., Pressure loads closer to D & A steam nozzles are greater than the B &

C steam nozzles).

b) Based on the pressure data, it can be concluded that although the dryer skirt base plate at 3200 AZ has a 5/16 bend and the highest measured pressure (P21 = 4.63 psi), no crack was found. However, at 1400 AZ, the dryer skirt base plate has highest bend (3/4) and lower measured pressure (P3 = 3.704 psi), yet a large crack in the skirt plate # 7 was noted. Therefore, it can be concluded that pressure oscillations alone could not be the primary cause of the crack initiation and/or propagation.

Further, review of Quad Cities Unit 2 Electromatic Relief Valve (ERV) ARs indicate that ERV 2-0203-3D on D MSL has seen more damage than 2-0203-3B and 2-0203-3E on B MSL and 2-0203-3C on C MSL. However, ERVs on B and C MSLs also have seen some failures. This evaluation confirms the conclusion reached in Report AM-2005-014 (Ref. 10) which states that Tables 1 and 2 seem to provide reasonable results in that the normalized flow through Main Steam Lines A and D are higher than B and C for both units. This is expected since the A and D Lines are the shorter Main Steam Lines.

References:

1) EC 351168, Rev. 2: Unit 2 Steam Dryer Replacement.
2) AR 334348: PSU - Steam Dryer would not set all the way down.
3) GE Traveler, Project KCZKU, Traveler No. KCZKU-Base Ring Deflection.
4) GENE Design Specification 26A6395, Rev. 2: Dryer Vibration Instrumentation
5) AR 347867: New steam Dryer Strain Gages/Accelerometers are failing.
6) AR 472321: PSU Q2R18 Crack in the U2 Steam Dryer Skirt.
7) AR 471848: PSU Q2R18 U-2 Steam Dryer Lifting Lugs Rotated.
8) QC Drawing M-3121, Rev F: In-service Inspection Isometric Reactor Vessel
9) Document Number: AM-2005-012, Rev 0 An Assessment of the Uncertainty in the Application of the Modified 930 MWe Acoustic Circuit Model Predictions For the Replacement Quad Cities Units 1 and 2 Steam Dryers.
10) Report AM-2005-014, Rev. 0, dated July 20, 2005: Quad Cities Unit 2 New Steam Dryer Outage Startup Test Report.

ATT. Page 10

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 PROBLEM STATEMENT:

Event 1. Crack/deformation of Dryer Skirt Ring near 140° Azimuth - INR Q2R18-IVVI-06-02 FAILURE FAILURE FAILURE FAILURE FAILURE MODE 1 MODE 2 MODE 3 MODE 4 MODE 5 Operating conditions Fabrication Damage during Operating Design flaw caused errors or material installation conditions mechanical deficiency activities (chemistry or damage flow pattern)

ATT. Page 11

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 1 Description Design Flaw Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Finite element model error Validate model IAW GE method requirements Model valid 1) Validated GE RCA -

allowed unacceptable stress complete A level to be accepted Independent review or model output Review confirms 2) Validated Rich Hall -

complete RIGOR (A, B, C, D, N/A) D Incorrect tolerances to allow for:

1) fit-up 1) Determine the role of Design in the known 1) Impact had 1) Confirmed as RCA - complete impact of new dryer with RPV lugs, and separator role in crack a CF.

B

2) heat-up/operational guide pins. Structural analysis and metallurgical initiation.

movement testing to determine if this initiated crack.

2) Review for evidence of rubbing of components 2) No evidence. 2) No evidence. RCA - complete due to expansion or operational forces.

ATT. Page 12

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 1 Description Design Flaw Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Inadequate load definition Review of model for design margin preventing No plastic Confirmed GE RCA -

C caused localized high stress plastic deformation deformation complete during design operating predicted conditions RIGOR (A, B, C, D, N/A) D FDDR RMCN 06243 Confirm conclusions of FDDR RMCN 06243 that Material strength Confirmed as GE RCA -

incorrectly allowed use of amount of metal removed still leaves adequate adequate not an initiating complete the machined ring slot with strength per design requirements including event.

strength reduced more than dynamic loads assumed a) How did the load redistribute b) What material impacts when grinding (GE D materials, what impact fatigue life for comp that exceeded 0.2% plastic strain)

Note: Unless metallurgical analysis specifies the presence of IGSSC, grinding and machining are not a CF.

ATT. Page 13

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 2

Description:

Operating conditions (mechanical)

Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Low quality steam output at Confirm mechanical load from moisture carry- Adequate No moisture RCA screened as A

the steam separator causes over is less than the design limit for dryer margin exists carryover low probability.

high moisture momentum components including the cyclic effect of 0.3 Hz concerns load to dryer core power cycles. identified. Closed RIGOR (A, B, C, D, N/A) D Transient event Review cycle history curve for SRV or BPV No blowdown or Review of power RCA screened as ADS/TG blowdown and transients and confirm that transient loads do not transient loads in history did not low probability.

rapid pressure change or exceed internal load limit and dryer lift limit excess of limits identify any B

dryer overload transients of concern. Closed Single MSIV closure at Review cycle history curve for asymmetric MSL Steady-state or power causing an flows or higher single MSL flow noise transient asymmetric load asymmetrics insignificant ATT. Page 14

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 2 Description Operating conditions (mechanical)

Refer to Attachment 4 for examples of risk Results Owner and rigor determination for steps below *Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D RCA screened as Cyclic power loads induce Evaluate MSL flow swings causing cyclic loading Fatigue load has Closed low probability high cycle fatigue of total dryer dP to induce fatigue large margin based on factors including C

MSL resonance evaluation in Power changes from sitting with RR bistable flow Fatigue load has Att. 8 RR bistable flow power large margin swings cause cycle dryer load Closed RIGOR (A, B, C, D, N/A) D Power/Flow Anomaly Compare core average exit quality (CAEQ) to CAEQ change Closed RCA screened as previous cycles (moisture carryover) from previous low probability.

High subcooling causes low cycles minimal D

core exit quality Compare FCL for cycle to previous cycles Closed High Flow Control Line (FCL) causes high core dP ATT. Page 15

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 3 Description Fabrication error or material deficiencies Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D
1. GE RCA -

Distortion/ovality of Cullen 1. Calculate the loads imposed by fit-up with as- 1. No loads Confirmed as not complete fit-up and weld of base to built ovality. (GE to address this in analysis) exceed design a CF A skirt limits.

2. Determine impact of ovality in reducing 2. Ovality impact Confirmed as a 2. RCA team -

clearances and influencing lift event. of reduced CF complete clearance is a CF.

RIGOR (A, B, C, D, N/A) D Incorrect or substandard Confirm that materials match the design requests 1. Records 1. Confirmed GE analysis -

materials were used or and that sub component supplier confirm proper complete supplier errors or process certifications/procurement records materials and control failures controls B

2. Metallurgical 2. GE testing analysis indicates that the confirms no materials are material consistent with deficiency. drawings and CMTRs.

ATT. Page 16

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 3 Description Fabrication error or material deficiencies Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Incorrect component Confirm dryer fabrication records match No DDR reviews no Summary review fabrication or techniques approved processes discrepancies issues as CFs completed. RCA C identified as problems. screened as low CFs. probability.

Closed RIGOR (A, B, C, D, N/A) D Incorrect fabrication Confirm fabrication sequences did not cause No DDR reviews no RCA screened as D sequence interim overstresses such as unsupported spans, discrepancies issues as CFs low probability.

temporary jacking etc. identified as problems.

CFs.

Closed ATT. Page 17

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 4 Description Damage during installation Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D 1&2. GE RCA complete Interference/overload 1. Calculate the loads on the skirt ring, gusset, No overstress No stresses cause excess load skirt panel during lifting determination of 3. Vallecitos during lift incident overstress, but complete A
2. Confirm dryer internal loads with single point lifting event Uneven lift loads hung up and weight distributed does not No overstress impacts on Rich Hall (ITPR) concentrate load localized overstress skirt ring during material is most Complete area at 140° location causes installation probable distortion 3. Metallurgical analysis of dryer materials. activities initiating event.

RIGOR (A, B, C, D, N/A) D Rotation/torsion applied Obtain description of manual rotation used, Torsion induced Torsion induced RCA screened as during installation caused calculate possible torsion loads loads were loads were low probability.

localized overstress minimal minimal B

Closed ATT. Page 18

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 4 Description Damage during installation Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Uneven weight distribution Calculate loads/flex caused by sitting on 2 RPV No gusset or Confirmed GE RCA while sitting on 2 RPV lugs lugs skirt ring complete caused load concentration overstressed C

exceeding limits (Note: Considered a lower priority analysis unless other analysis is inconclusive).

RIGOR (A, B, C, D, N/A) D Load cell Not a CF inoperable is not Site RCA -

RB Crane load cell visual Determine impact of inoperable load cell on lift a CF but complete display not working during event. included in dryer installation. Other section.

D ATT. Page 19

Att. 5 - Event 1: Failure Mode Tree Ref: MA-AA-716-004 Att.2 Failure Mode No. 5 Description Operating Conditions (chemistry or flow)

Results Owner

  • Expected results are based on system Status operation as designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Core design issues, power Compare core operating conditions to as named No discrepancy Closed RCA screened as distribution increased local service conditions between design low probability.

moisture but was damaged and operation A

by moisture momentum Closed RIGOR (A, B, C, D, N/A) D Steam separator local Inspect steam separator for blocked flow path No blocked Closed RCA screened as blockage caused uneven separator tubes low probability.

loading (increased flow in B

part, decreased other)

Closed ATT. Page 20

Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 PROBLEM STATEMENT:

Event 2: Crack was found in adjacent vane bank end plates (in the E vane bank near 320° of the Dryer)

Ref: IVVI-06-04 FAILURE FAILURE FAILURE FAILURE FAILURE MODE 1 MODE 2 MODE 3 MODE 4 MODE 5 Installation/

Fabrication Inadequate Material Operational Removal Defect Design Defect Conditions In Overload/

Overstress Condition ATT. Page 21

Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 1 Description Fabrication Defect Results Owner

  • Expected results are based on system operation as Status designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D High stress condition or Inspect failed area visually for location or No crack Potential CF: GE RCA -

stress riser created by indication of any crack initiation or defect initiation site or INR Page 2 last Complete inappropriate weld or other defect identified picture shows a A fabrication error location where there is very little weld material and this point appears to be the initiation site for the crack*

  • Based on these inspection results, it can be concluded that having very little weld metal between the end plates at gusset 19 contributed to the initiation and propagation of the crack in this location. This incomplete weld combined with hood assembly fit-up and weld shrinkage stresses, and the deformation and loading associated with the interferences during dryer removal are the most probable cause of the crack initiation that would then have been driven to its current size by operating vibration loads.

ATT. Page 22

Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 2 Description Inadequate Design Results Owner

  • Expected results are based on system operation as Status designed, not as failed Cause(s) Validation/Action Steps Expected Actual Crack occurred in area RIGOR (A, B, C, D, N/A) D Stress is within Confirmed subjected to overstress allowable limits GE RCA A (Finite Element Analysis Stress analysis to identify loading/stresses in area complete.

incorrect)

Failure Mode No. 3

Description:

Material Defect Results Owner

  • Expected results are based on system operation as Status designed, not as failed Cause(s) Validation/Action Steps Expected Actual RIGOR (A, B, C, D, N/A) D Defects in plate material Failure not due Closed RCA screened as created stress riser or highly Inspect plate for evidence of fracture initiation to material low probability.

A localized stress location, fretting or fatigue defect Closed ATT. Page 23

Att. 6 - Event 2: Failure Mode Tree Ref: MA-AA-716-004 Att. 2 Failure Mode No. 4

Description:

Operational Conditions Results Owner

  • Expected results are based on system operation as Status designed, not as failed Cause(s) Validation/Action Steps Expected Actual Operating conditions caused RIGOR (A, B, C, D, N/A) D Operating RCA screened as vibrations that exceeded the conditions were Closed low probability.

A design capabilities of the Verify appropriate operating conditions were appropriately vane bank end plate modeled in analysis modeled Closed Failure Mode No. 5 Description Installation/Removal in Overload/Overstress Condition Results Owner

  • Expected results are based on system operation as Status designed, not as failed Cause(s) Validation/Action Steps Expected Actual Excessive loads were placed RIGOR (A, B, C, D, N/A) D The load was on the vane bank end plates within the design Analysis GE RCA complete A when the Steam Dryer was Determine the load that was applied to the vane limits of the vane concludes this is resting on the Steam bank end plate during the incident. bank end plate not a CF.

Separator Guide Rods Excessive loads were placed RIGOR (A, B, C, D, N/A) D The load was Analysis on the vane bank end plates within the design concluded this is GE RCA B when the Steam Dryer was Determine the load that was applied to the vane limits of the vane not a CF complete stuck on the RPV lugs bank end plate during the incident. bank end plate ATT. Page 24

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Background:

During the initial installation of the Quad Cities Unit 2 dryer, the dryer became hung up on the dryer lugs. During the initial dryer placement, it was discovered that the dryer base plate interfered with the separator guide rods. As a result, the dryer was removed to allow the base plate to be modified to prevent the interference.

During the lift, the dryer base plate became hung up on the dryer lugs. The interference resulted in damage to the dryer lugs and local yielding of the dryer base plate.

Evaluation: There are four dryer support lugs on the ID of the reactor vessel and four guide slots in the dryer base plate. The guide slots are intended to allow the dryer base plate to move by the dryer support lugs during lowering and lifting. The support lugs and guide slots are located at 40°, 140°, 220°, and 320° azimuths around the ID of the reactor vessel and the OD of the dryer base plate, respectively.

The dryer base plate and the reactor vessel lugs were examined following the incident (Ref. Work Order # 732708-01). The base plate was found deformed (i.e. - bent) downward at the 140°, the 220°, and the 320° locations. The 40° dryer location was not damaged. The base plate near the 140° guide slot location was bent down by 3/4 inch, the 220° was bent down by 5/8 inch, and the 320° was bent down by 5/16 inch. The base plate near the 140° was bent on the right hand side, when looking at the dryer, and the other two locations were bent on the left hand side when looking at the dryer. This is shown schematically in Figure 1.

The videotape of the in vessel dryer support lug inspection was reviewed and stills extracted as shown in figures 1 through 12 below. The 40° lug (Figure 3) had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID, even though the dryer base plate at this location was not damaged. The support lug located at 140° (Figure 4) also had a corner deformation on the right hand side of the lug, when looking at the lug from the vessel ID. The 220° (Figures 5 and 6) and 320° (Figures 7 and 8) support lugs were damaged on the lower left hand corner. The worst deformations were on the 220° and 140° location.

The design of the base plate cutouts and the dryer guide rod slot would allow the dryer to rotate and potentially allow the cutout gussets to impact the dryer support lugs. Based on the geometry of the vessel lugs and the base plate cutouts, it does not seem reasonable that the dryer would impact two lugs on the right side and the other two on the left side.

This conclusion would lead to the possibility that there were two different impacts, or events. However, based on discussion with individuals who were present, there was only one impact event. That is, the dryer was not lowered or rotated and then lifted again.

This leads to the possibility of multiple impacts during a single event.

The as-built elevation of the top of the dryer support lugs is excerpted from the reactor vessel as-built drawing (CBI drawing 69-4824) and is provided in Table 1.

Attachment page 25

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Lug Azimuth Location As-Built Elevation 40 616 - 13/16 140 617 - 1/32 220 616 - 11/16 320 616 - 13/16 Table 1 Dryer Support Lug As-Built Elevation (Measured from the support skirt)

This drawing indicates that the lowest lug is the 220° lug, and the highest is the 140° lug.

This assumes that they are all approximately the same length. The data indicates that the 220° lug is 11/32 (0.344) below the 140 degree lug. Also, the 40° and the 320° lugs are 7/32 (0.219) below the 140° lug.

As can be seen in figures 7 through 11, the lugs were also damaged when the dryer was lowered into the reactor vessel. This damage indicates that the combination of dryer support lug as-built location and size combined with the dryer base plate cutout as-built location and size, and the as-built clearances between the dryer guide pins and guide slots, resulted in a lack of clearance and interference between the dryer support lugs and the cutouts when lowering the load. Since a review of all of the as-built locations and sizes and combinations thereof is difficult and yields results that are subject to the stacking of multiple accuracies, it is sufficient t note that the potential for the interference exists based on the evidence of damage to the lugs from lowering the load.

A plausible sequence of events can be established using the evidence of damage to the dryer support lugs and the dryer base plate and the as-built elevations of the bottom of the dryer support lugs. It cannot be established that this is the exact sequence of events, but only that this is a likely scenario that is coincidental with the established facts.

Since the 220° dryer support lug is the lowest lug, it is presumed that the dryer base plate cutout contacted this lug first. (Note the contact point for all of the interferences would be the gusset plate that is located on the either side of the base plate cutout.) Also, since the dryer contacted the left side of the lug, the dryer is rotated clockwise when looking down from the crane. The initial impact on this lug is supported by the lower elevation and fact that the damage to the dryer support lug at his location was the worst for all of the support lugs (See figures 3 and 4). It is not necessarily supported by the amount of damage to the dryer base plate.

The dryer would continue to be lifted as it yielded both the support lug and the dryer base plate at the 200° location. Once the dryer had been lifted approximately 1/16, the dryer would contact the 320° location at the left hand side of the lug. The dryer also should have impacted the 40° lug on the left hand side, however it did not. This can be explained by reviewing figures 7 and 8.

Attachment page 26

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Note that the damage to the 40° lug when lowering the load occurred on the right hand side of the lug. This indicates that when the dryer is positioned such that it passes by all of the lugs, it is closer to the right hand side of the 40° lug. Therefore, the largest clearance between the 40° dryer support lug and the dryer base plate cutout would be on the left hand side of the lug. Then, if the dryer is rotated clockwise, it may not impact the left hand side of the 40° lug since that is the side of the greatest clearance.

Once the dryer base plate contacts the 320° support lug, the load is shared between the base plate locations at 220° and 320°. This would help to limit the amount of base plate deformation at the 220° location. The dryer would continue to lift and possibly rotate such that the 220° to 320° section of the dryer would be lower than the 40° to 140° side.

The dryer released from the 220 and 320° lugs and swung, or tilted, while rotating back counter clockwise. During the tilt or swing, the dryer impacted the support lugs at 40 and 140 degrees. The release mechanism is supported by the edge displacement damage to the 320° lug, which makes it appear that the dryer slid laterally away from the lug, causing material on the lug to move downward (Figures 5 and 6). As stated previously, the dryer, once it was free to swing, impacted the lower right edge of both the 40 and 140° support lugs. The dryer impacted the lower part of the 140 degree support lug and impacted only the edge of the 40 degree lug. The reason the dryer impacted below the 140° support lug is due to the higher elevation of the lug and the tilting of the dryer. The dryer scraped the lower right hand side of the 40° vessel support lug (Figure 1) because that lug is slightly higher than the 140° support lug. That is, the dryer did not wedge under the 40° lug because of the lower elevation versus the 140° lug, but it did hit the edge of the lug, as seen in Figure 1.

Conclusions Based on this evaluation, the following summarizes the interference event that occurred during the initial dryer installation:

1. Dryer base plate guide slots impact multiple dryer support lugs during the initial lowering into position.
2. Dryer base plate interferes with the separator guide pins and cannot be placed in final position. This causes the dryer to be lifted to facilitate modifications.
3. Dryer is rotated clockwise during the lift (slightly, less than 1 inch).
4. Dryer base plate guide slot gusset interferes with dryer support lug at the 220° location. This results in a 1/2 high by 3/8 wide damaged area in the dryer support lug and a 5/8 inch downward deflection of the base plate.
5. Dryer base plate guide slot gusset interferes with dryer support lug at the 320° location. This results in part of the dryer support lug being sheared off and the dryer base plate deflection of 5/16.
6. Dryer tilts noticeably along the 0 and 180° axis, prior to releasing from the lugs.
7. Dryer releases, swinging back towards 220 and 320° location.

Attachment page 27

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

8. Dryer rotates and swings into the 140 and 40° lug.
9. Dryer impacts the 140° lug below the right lower edge of the lug.
10. This impact results in a sharp crease in the dryer support lug and the formation of an edge on the base plate gusset. The corner of the 140° lug is pushed in and partially shears off.
11. During the tilt/rotation, the dryer impacts the right bottom corner of the 40° lug, shearing off the corner.
12. The dryer lift is completed without further incident.

Attachment page 28

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Separator Guide Rod Cutout 0o (2 Locations) 320o 20o 40o 5/16 Bend RPV Lug Cutout (4 Locations) 270o 90o 220o o 140o 200 180o 5/8 Bend 3/4 Bend Impact on RPV Dryer Support Lug Figure 1 Steam Dryer Plan - Impact Locations Attachment page 29

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Figure 2 General Relationship Between Dryer Cracking (Top), Dryer Guide Slot Cutout at 140 Degrees (Center), and Dryer Support Lug at 140 Degrees (Bottom)

Attachment page 30

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Lower right hand corner indicates scraping damage Figure 3 Damage to 40 Degree Lug, Lower Right Hand Corner Damaged During Impact Lower right hand corner damage due to impact of dryer Figure 4 Damage To 140 Degree Lug, Lower Right Hand Corner Damaged Due to Major Impact Attachment page 31

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Lower left hand corner damage indicates dryer stuck below support lug Figure 5 Damage To 220 Degree Lug, Lower left hand Corner Same damage as viewed from the bottom of the lug Figure 6 Damage To 220 Degree Lug, Lower left hand Corner (View from Bottom)

Attachment page 32

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Damage to lower left hand corner due to dryer. Note some damage indication is from top to bottom.

Figure 7 Damage to 320 Degree Lug, Lower Left Hand Corner Same damage as previous figure, seen from the bottom of the lug.

Figure 8 Damage to 320 Degree Lug, Lower Left Hand Corner (View From Bottom)

Attachment page 33

Att 7: Dryer to Dryer Lug Impact Analysis (Lifting Event)

Damage to right hand side of lug, too low to be caused by spacer block.

Figure 9 Damage to Right Hand Side of 40 Degree Lug, Due to Base Plate When Lowering Attachment page 34

Att. 8: Q2R18 INR Resolution Matrix*

Current Proposed Resolution IR INR Number Rev Title (Not Final) Resolution Document EC 471848 Q2R18-IVVI-06-01 0 Steam Dryer Lifting Lugs at 45, 135, 225, &315 Deg Repair Per FDDR RMCN08456 WO 681384-01, FDDR RMCN08456 Rev B 360356 472321 Q2R18-IVVI-06-02 0 Steam Dryer Skirt at 135 Deg Repair Per FDDR RMCN08382 WO 681384-01, FDDR RMCN08382 Rev A 360356 474814 Q2R18-IVVI-06-03 3 Jet Pump 05 (WD-1) JCO - Possibly replace Q2R19 GENE-0000-0052-9152 R0 360359 473034 Q2R18-IVVI-06-04 1 Steam Dryer SD-BE-V12-2H, SD-BE-V11-2H Accept As Is GENE-0000-0052-9728 R0 360356 475009 Q2R18-IVVI-06-05 0 Jet Pump 08 (WD-1) JCO - Possibly replace Q2R19 GENE-0000-0052-9152 R0 360359 473344 Q2R18-IVVI-06-06 0 Steam Dryer Internal Weld SD-BF-V06-2H-ID Accept As Is w/future inspection / LPA GE-NE-0000-0052-7988-R0 360356 473619 Q2R18-IVVI-06-07 0 Steam Separator Upper Support Ring Gusset Accept As Is w/future inspection GENE-0000-0052-8398-R0 360359 473615 Q2R18-IVVI-06-08 0 Steam Dryer Internal Weld SD-BD-V06-2H-ID Accept As Is w/future inspection / LPA GE-NE-0000-0052-7988-R0 360356 473622 Q2R18-IVVI-06-09 1 Steam Separator Shroud Head Bolt 14 and 35 Rotate and perform VT-3 Video files 481701, 481101, 481301, 481401 360359 473626 Q2R18-IVVI-06-10 0 Steam Dryer Internal Weld SD-BB-V04-2H-ID Accept As Is w/future inspection GE-NE-0000-0052-7988-R0 360356 473923 Q2R18-IVVI-06-11 1 Steam Dryer Internal Debris Accept As Is w/future inspection / LPA Lost Parts Analysis EC 360467 360356 473871 Q2R18-IVVI-06-12 0 Steam Dryer Internal Area (Separator Guide Cutout) Increase clearance FDDR RMCN088242 WO 681384-01, FDDR RMCN08242 Rev A 360356 473839 Q2R18-IVVI-06-13 0 Separator Lower Support Ring Gusset Accept As Is w/future inspection GENE-0000-0052-8398-R0 360359 474491 Q2R18-IVVI-06-14 0 Jet Pump 10 Wedge Assembly Accept As Is w/future inspection GENE-0000-0052-9152 R0 360359 474070 Q2R18-IVVI-06-15 0 Jet Pump 07 Wedge Assembly Replace swing gate as planned WO 823272-01 360359 473844 Q2R18-IVVI-06-16 0 Feedwater Sparger End Bracket Planned Tack Weld per FDI 0194 GE-NE-0000-0052-8396-R0 360359 474064 Q2R18-IVVI-06-17 0 Shroud Repair Yoke at 290 Degrees Accept As Is - Installed condition GE-NE-0000-0052-8402-R0 360359 474485 Q2R18-IVVI-06-18 0 Dryer General Visual (220 to 320 Degrees) NRI - No action required IR 474497 comments 360356 474497 Q2R18-IVVI-06-19 0 Feedwater Sparger 13&16 Degree End Bracket & Pin Planned Tack Weld per FDI 0194 GE-NE-0000-0052-8396-R0 360359 474501 Q2R18-IVVI-06-20 0 Steam Dryer Skirt Baseplate at 220 Degrees Repair Per FDDR RMCN08242 WO 681384-01, FDDR RMCN08404 Rev A 360356 475003 Q2R18-IVVI-06-21 0 Steam Dryer WSL @ 220 Degrees No Action Required - unchanged IR 475003 comments 360356 475328 Q2R18-IVVI-06-22 0 CS Lower Elbow to Shroud Pipe 290 Degree Azimuth Inspect next RFO INR Exelon Level III review 360359 474514 Q2R18-IVVI-06-23 0 Steam Dryer Base Plate Distortion at 320 Degrees No change- Accept As Is EC 360356 360356 474517 Q2R18-IVVI-06-24 0 Steam Dryer Surface Anomalies at SD-SKT-V11-ID NRI - No action required IR 474517 comments 360356 474977 Q2R18-IVVI-06-25 0 Shroud Head Flange Ring Segment (EDM Hole) Accept As Is - Previously eval'd GENE-771-110-0595 R0 360359 475862 Q2R18-IVVI-06-26 0 Core Support Flange Ring OD Accept As Is w/future inspection GENE-771-110-0595 (May 1995) 360359 475332 Q2R18-IVVI-06-27 0 Shroud Head Flange Ring OD Accept As Is GENE-0000-0053-0964-R1 360359 475339 Q2R18-IVVI-06-28 1 Steam Dryer WSLs @ 40, 140 and 320 Degrees No Action Required - unchanged IR 475339 comments 360356 475369 Q2R18-IVVI-06-29 0 Steam Dryer Indication, SD-LB-03-W1 OD @ 220 DegRepair per FDDR RMCN08435 WO 681384-01, FDDR RMCN08435 Rev A 360356 476654 Q2R18-IVVI-06-30 0 RPV Jet Pump Annulus FME Remove FME Lost Parts Analysis EC 360467 360359 476657 Q2R18-IVVI-06-31 1 Steam Dryer Exit Plenum Perforated Plate Accept As Is GENE-0000-0053-0964-R0 360356 477326 Q2R18-IVVI-06-32 0 CS Sparger S3c Drain (two plugs missing tack welds) Accept As Is GENE-0000-0053-0964-R0 360359 N/A Q2R18-IVVI-06-33 0 Tie Rod Loose and Missing Nuts (As designed) NRI - No action required INR - Future reference only. Mention in EC. 360359 476540 None - IR only SHB #9 suspect based on UT criteria Accept As Is w/future inspection IR, GE Letter DRF B13-01903-8 360359

  • The highlighted items are specifically included in the scope of RCR 472321 Attachment page 35

Att. 9: CAs to Address Programmatic/ Organizational Issues A. CAs from ERV RCA (Ref. 38) aligned with Q2R18 Steam Dryer RCA CF. 2

Background:

CF #3 to ERV RCA: Organizational effectiveness and decision-making.

==

Description:==

The organizational contributors taken in aggregate demonstrate weaknesses in managing information, over-reliance on contractor-performed analysis, and applying a systematic approach to decision making for complex high-risk situations.

Causes Being Corrective Action (CA) or Action Item (ACIT)) Owner Due Date Addressed CF#3 Provide training to Corporate Engineering personnel on A8081 9/20/2006 Organizational the requirement and application of OP-AA-106-101- TRLS effectiveness and 1006 for complex decision-making (CA# 23 revises OP-decision-making. AA-106-101-1006).

Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process.

CA #20 CF#3 Provide training to Quad Cities Engineering personnel A8461 9/02/2006 Organizational on the requirement and application of OP-AA-106-101- ESPT effectiveness and 1006 for complex decision-making (CA# 23 revises OP-decision-making. AA-106-101-1006).

Complex engineering decisions which involve historical data, repeat equipment failure, risk and complex analysis shall require the use of OP-AA-106-101-1006 Operational And Technical Decision Making Process.

CA #21 CF#3- from Ref. 38 Update HU-AA-1212 Technical Task Risk/Rigor A8053VP 6/16/2006 Organizational Assessment, Pre-Job Brief, Independent Third Party BWR effectiveness and Review, And Post-Job Brief to provide a link to OP-AA- (BRWRD) decision-making. 101-1006 for complex engineering decisions and/or products which involve historical data, repeat equipment failure, risk and complex analysis.

CA #22 CF#3- from Ref. 38 Training CRCs shall evaluate the need of providing A8068EN 6/16/2006 Organizational training to Exelon FLSs and above on the use and DES effectiveness and application of OP-AA-106-101-1006.

decision-making.

ACIT #4 CF#3- from Ref. 38 Submit update to OP-AA-106-101-1006 Operational And A8068EN 6/30/2006 Organizational Technical Decision Making Process Attachment B, DES effectiveness and Recognize Conditions to include lessons learned from decision-making. the ERV root cause and documentation of all personnel involved in the final product.

Closure to include new assignment for processing of procedure change to Operations peer group.

CA #23 Attachment Page 36

Att. 9: CAs to Address Programmatic/ Organizational Issues B. CAs from ERV Actuator RCA (Ref. 38) & Replacement Dryer Fuel Impacts RCA (Ref. 37) aligned with Q2R18 Steam Dryer RCA - Negative Design Impacts Causes Being Addressed Corrective Action (CA) or Owner Due Date Action Item (ACIT))

CF#3 - from Ref. 38 Change the design input A8068ENDES 7/28/2006 Organizational effectiveness requirements to include upfront and decision-making. challenges to analysis and assumptions as part of the design review. The documents include CC-AA-103-1003 Owners Acceptance Review Of External Configuration Change Packages and CC-AA-309 Control of Design Analysis. These front-end challenges shall be applied to all design changes and modifications independent of level.

CA #25 CAPR3 - from Ref. 37 Revise HU-AA-1212, Technical Task Risk/Rigor Assessment to Revision issued complete include guidance on how to select by NCS.

what type of third-party review(s) are required. AT#: 330331-21 (complete)

CAPR4- from Ref. 37 Revise PC-AA-1008, Issue Chartering. Add step 4.3.3.2 to require project teams - in the project NCS A8070PM 08/31/06 scoping phase - to review all CC-AA-102 attachments in order to determine scope additions and affected organizations. AT#: 281476-07 ACIT6- from Ref. 37 Evaluate the results of this root cause investigation for inclusion in the Project Management TAC. NCS A8070PM Complete Specifically, investigate training project managers on how to identify which departments to include on a project and when. AT#: 330331-22 Attachment Page 37

ATTACHMENT 14 - of LS-AA-125-1001 (ATT. 10 of specific RCA 472321)

Root Cause Report Quality Checklist Page 1 of 2 A. Critical Content Attributes YES NO

1. Is the condition that requires resolution adequately and accurately identified? X
2. Are inappropriate actions and equipment failures (causal factors) identified? X
3. Are the causes accurately identified, including root causes and contributing causes? X
4. Are there corrective actions to prevent recurrence identified for each root cause and do X they tie DIRECTLY to the root cause? AND, are there corrective actions for contributing cause and do they tie DIRECTLY to the contributing cause?
5. Have the root cause analysis techniques been appropriately used and documented? X
6. Was an Event and Causal Factors Chart properly prepared? X
7. Does the report adequately and accurately address the extent of condition in accordance X with the guidance provided in Attachment 3 of LS-AA-125-1003, Reference 4.3?
8. Does the report adequately and accurately address plant specific risk consequences? X
9. Does the report adequately and accurately address programmatic and organizational X issues?
10. Have previous similar events been evaluated? Has an Operating Experience database X search been performed to determine whether the problem was preventable if industry experience had been adequately implemented?

B. Important Content Attributes

1. Are all of the important facts included in the report? X
2. Does the report explain the logic used to arrive at the conclusions? X
3. If appropriate, does the report explain what root causes were considered, but eliminated X from further consideration and the bases for their elimination from consideration?
4. Does the report identify contributing causes, if applicable? X
5. Is it clear what conditions the corrective actions are intended to create? X
6. Are there unnecessary corrective actions that do not address the root causes X or contributing causes?
7. Is the timing for completion of each corrective action commensurate with the X importance or risk associated with the issue?

Att. page 38

ATTACHMENT 14 Root Cause Report Quality Checklist Page 2 of 2 C. Miscellaneous Items YES NO

1. Did an individual who is qualified in Root Cause Analysis prepare the report? X
2. Does the Executive Summary adequately and accurately describe the significance of the X event, the event sequence, root causes, corrective actions, reportability, and previous events?
3. Do the corrective actions include an effectiveness review for corrective actions to X prevent recurrence?
4. Were ALL corrective actions entered and verified to be in Action Tracking? *
5. Are the format, composition, and rhetoric acceptable (grammar, typographical errors, x spelling, acronyms, etc.)?
  • New AT items are created by CAP organization after MRC approval of RCA.

Att. page 39

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