IR 05000285/2012010
| ML12146A163 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 05/24/2012 |
| From: | Bannister D J Omaha Public Power District |
| To: | Document Control Desk, NRC Region 4 |
| References | |
| EA-12-023, IR-12-010, LIC-12-0051 | |
| Preceding documents: |
|
| Download: ML12146A163 (13) | |
Text
Omaha Public Power 444 South 16 111 Street Mall Omaha , NE 68102-2247 LlC-12-0051 , May 24,2012 u.s. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001 References1. Docket Number 50-285 2Letter from OPPD (D. J. Bannister)
to NRC Document Co n trol Desk (DCD) dated October 27,2011 (LlC-11-01 06) Letter from NRC (A. Vegel) to OPPD (D. J. Bannister)
dated March 12, 2012 (N RC-12-0022)(EA-12-023) Letter from OPPD (D. J. Bannister)
to NRC Document Control Desk (DCD) dated March 22, 2012 (UC-12-0030) Letter from NRC (E. E. Collins) to OPPD (D. J. Bannister)
dated April 10, 2012 (EA-12-023)
6Letter from OPPD (D. J. Bannister)
to NRC D ocument Control Desk (DCD) dated May 9,2012 (LlC-12-0068)
NRC Inspection Report 05000285/2012010, Reply to a Notice of Violation (NOV); EA-12-023 In Reference 5, the Nuclear Regulatory Commission (NRC) transmitted a Red Finding and a Notice of Violation (NOV) to the Omaha Public Power District (OPPD). This Red finding , involved the failure to ensure that the General l Electric AKD-5 480 Vac electrical switchgear design requirements were properly implemented and maintained through proper maintenance, modification, and design activities along with the failure to implement and maintain in effect all provisions of the fire protection program. OPPD periormed an initial root cause analysis to determine the causes of the switchgear fire and develop associated corrective actions. However, to ensure a complete understanding of the causes of the fire an independent third party analysis was periormed. The original due date for the response to EA-12-023 was May 10, 2012. In orde r to complete the third party analysis and report the results in the response to EA-12-023, a 14 day extension was requested and granted by Mr. Jeff Clark of the Region IV NRC staff. The basis for the extension is provided in Reference 6. Pursuant to 10 CFR 2.201, OPPD admits the violations occurred and a response to the NOV is provided in the enclosure to this letter. OPPD recognizes the potential safety , importance of fires; therefore, the prevention of fires is of the utmost importance to OPPD. Actions have been completed to bring OPPD into compliance with the specific deficiencies in station procedures, equipment and training as U. S. Nuclear Regulatory Commission LlC-12-0051 May 24,2012 Page 2 identified in Heference 5. Additional actions are planned to address deficiencies in station human performance, safety culture and problem identification and resolutio This letter contains regulatory commitments that are summarized on the last page of the enclosur If you should have any questions, please contact m D. J. Bannister Site Vice President and CNO Enclosure DJB/rmc c: E. E. Collins , Jr., NRC Regional Administrator, Region IV L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector UC-12-0051 Enclosure Page 1 REPLY TO A NOTICE OF VIOLATION Omaha Public Power District Docket No. 50-285 Fort Calhoun Station License No. DPR-40 EA-12-023 During an NRC Inspection conducted from September 12, 2011' to February 29,2012 , violations of NRC requirements were identifie In accordance with the NRC Enforcement Policy, the violations are listed below: 10 CFR Part 50, Appendix B, Criterion III', "Design Control," requires, in part that: (1) design changes, including field changes, be subject to design control measures commensurate with those applied to the original design; (2) measures be established to assure that appl'icable regulatory requirements and the design basis for safety-related structures, systems and components are correctly translated into specifications, drawings, procedures, and instructions; and (3) these measures assure that a p propriate quality standards are specified and included in design documents and that deviations from such standards are controlle Contrary to the above requirement, from November 2009 to June 7, 2011, the licensee failed to ensure that design changes were subject to design control measures commensurate with those applied to the original design; fai'led to assure that applicable regulatory requirements and the design bas , i s for related structures, systems, and components were correctly translated into drawings , procedures, and instructions; and fai'led to ensure that these measures assured that appropriate quality standards were specified and included in the design document Specifically, design reviews, work planning and instructions for a modification to install new 480 Vac load center b reakers faile d to ensure that the cradle adapter assemblies had low resistance connections with the switchgear bus bars by establishing a proper fit and requiring low resistance connections to assure that design basis requirements were maintained. 10 CFR Part 50, Appendix B, Criterion XVI, "Corrective Action , " requires in part , that measures be established to assure that conditions adverse to quality such as failures, defective material and equipment, and non conformances are promptly identified and correcte In the case of signif l icant conditions adverse to quality, the measures shall assure that the cause of the condition is determined and corrective action taken to preclude repetitio Contrary to the above requirement, from May 22, 2008, to June 7, 2011, the licensee failed to assure that the cause of the significant condition advise to quality was determined and corrective action was taken to preclude repetitio Specifically, the licensee failed to ensure that their preventative maintenance program for the safety-related 480 Vac electrical power distribution system was LlC-12-0051 Enclosure Page 2 adequate to ensure proper cleaning of conductors, proper torqueing of bolted conductor or bus bar connections, and adequate inspection guidance for abnormal connection temperatures. In 2008, the licensee identified that preventative maintenance procedure EM-PM-EX-1200, "Inspection and Maintenance of Model AKO-5 Low Voltage Switchgear," was less than adequate as a result of a root cause analysis for the failure of bus-tie breaker BT-1 B3A to close on demand and loss of bus 1 B3A The licensee categorized this failure as a significant condition adverse to quality. The analysis concluded that breaker 1 B3A had high resistance connections which occurred as a result of both procedure deficiencies and inadequate implementation resulting in the failure to remove dirt and hardened grease from electrical connection The licensee implemented corrective actions to address these procedural deficiencies; however the corrective actions were inadequate to prevent high resistance connections in load center 1 B4A due to the presence of hardened grease and oxidatio The procedure did not contain adequate guidance for torqueing bolted connections or measuring abnormal connection temperatures due to loose electrical connections in the bus compartment of the switchgear. L'icense Condition 3.0, "Fire Protection Program," requires, in part, that the licensee implement and mainta i n in effect all provisions of the approved Fire Protection Program as described in the Updated Safety Analysis Report and as approved in NRC safety evaluation reports. Section 9.11.1 of the Updated Safety Analysis Report describes the fire protection system design basis and states, in part, that the design basis of the fire protection systems includes commitments to 10 CFR Part 50, Appendix R, Section III.G. "Fire protection of safe shutdown capability,"Section III.G.1.a., requires, in part, that fire protection features be provided for structures, systems, and components important to safe shutdown, and that these features be capable of limiting fire damage so that one train of systems necessary to achieve and maintain hot shutdown conditions is free of fire damage. Contrary to the above requirement, from November 2009, to June 7, 2011, the licensee failed to implement and maintain in effect all provisions of the approved Fire Protection Program. Specifically, the licensee failed to ensure that design reviews for electrical protection and train separation of the 480 Vac electrical power distribution system were adequate to ensure that a fire in load center 1 B4A would not adversely affect operation of redundant safe shutdown equipment in load center 1 B3A, such that one train of systems necessary to achieve and maintain hot shutdown conditions were free of fire damage. Combustion products from the fire in load center 1 B4A migrated across normally open bus-tie breaker BT -1 B4A into the non-segregated bus duct, shorting all three electrical phases. The non-segregated bus ducting electrically connected load center 1 B4A with the Island Bus 1 B3A-4A and, through normally closed tie breaker BT-1 B3A, to the redundant safe shutdown trai LlC-12-0051 Enclosure Page 3 These violations are associated with a Red Significance Determination Process finding, OPPD Response -NOV A 1. Reason for the Violation Due to aging issues and the lack of spare parts, a total of twelve original 480 Vac General E'lectric (GE) AK-50 circuit breakers were replaced during the 2009 FCS refueling outage. The GE AK-50 circuit breakers were rep'laced because they were approximately 40 years old. The twelve circuit breakers were replaced on nine 480 Vac safety-related switchgear buses. The GE original equipment was replaced with Square D circuit breakers supplied through Nuclear Logistics Incorporated (NLI). The original GE AK-50 circuit breakers racked into the circuit breaker cubicles making direct insertion onto the bus stabs. The switchgear was manufactured with welded aluminum bus work transitioning to welded aluminum to copper bus stabs. The original copper bus stabs were supplied with a silver contact area of approximately one inch that the original GE AK-50 circ u it breaker finger clusters made electrical contact. For most environments the silver plating provides a higher conductive material to maintain a high quality electrical connection for long periods of time. The Square D circuit breakers were not an exact replacement for the GE equipment; therefore, a cradle assembly was utilized to ensure that the Square D equipment would match-up to the GE switchgea The cradle assembly consists of finger cl'usters that engage the bus bars on the back of the GE switchgear, and has stabs on the circu it brea k er side of the cradle assembly that accept the circuit breaker finger clusters. The replacement circuit breaker finger clusters that engage the bus bars were longer than the original circuit breaker finger clusters and did not engage the silver-plated area of the bus stabs. The circuit breaker finger clusters engaged the bus bar in a contact area of hardened grease which is the most likely cause of a high resistance connection at the stab to finger interfac The high resistance connection overheated the finger cluster resulting in bus grounding and phase-to-phase shortin An analysis determined that the root cause of the f i re in the 480 Vac bus 1 B4A was the FCS design process failed to identify critical parameters and interfaces such as the silver plating contact area on the switchgear cubicle bus stabs, and the critical differences in dimensions that impact the cradle alignment with the circuit breaker cubicle when specifications for the replacement for the original GE AK-50 circuit breakers were developed. The analysis also identified the foNowing contributing causes:
L1C-12-0051 Enclosure Page 4 Design engineers had limited knowledge of GE AKD-5 switchgear which resulted in over-reliance on vendor knowl'edge and skill. A modification procedure lacks requirements to identify and compare critical design requirements for the use of operating experience criteria. The design change specifications did not consider the partial plating of the switchgear stabs, resulting in the replacement circuit breaker cradles engaging the bus stabs at the edge of and beyond the silver-plated contact area. As-'Ieft resistance readings from the I , ine to load s i de of the switchgear finger cluster engagement following circuit breaker replacement were not confirme . Corrective Steps Taken and the Results Achieved Appl'icable modification procedures were revised to include requirements for the identification of critical interface characteristics during the design process. Applicable modification procedures were revised to include requirements for expanding the operating experience search criteria to include both internal and external applicable documents. The AKD-5 switchgear bus bar engagement area for the replacement 480 Vac circuit breaker finger clusters were silver plated to ensure full engagement of the finger clusters. The 12 replacement circuit breaker cradles were adjusted to ensure that the circuit breaker finger clusters engaged the silver-plated area. The finger cluster to bus bar engagement was confirmed through acceptable as-left resistance readings of the line to load side connections of the applicable swi l tchgear. 3. Corrective Steps T h at Will be Taken Switchgear and circuit breaker training will be included in the engineering initial and continuing training programs by September 3,2012. A trending program that evaluates resistance measurements of the finger cluster to bus bar engagement line to load side connections of applicable switchgear during preventative maintenance activities will be developed by September 15, 2012. 4. Date When Full Compliance Will be Achieved Based on the completion of required revisions to appropriate modification procedures and physical changes to the affected 480 Vac switchgear buses, OPPD is currently in complianc LlC-12-0051 Enclosure Page 5 OPPD Response -NOV B 1. Reason for the Vio'lation The FCS 480 Vac electrical distribution system consists of n ine switchgear buses that power safety-related equipment required for the operation of the plant. The switchgear is GE AKD-5 480 Vac switchgear that was installed during construction of FCS and has been in service for approximately 40 years. The switchgear was manufactured with welded aluminum bus work transitioning to welded aluminum to copper bus stabs that are tipped with approximately one inch of sliver plating. The original copper bus stabs were su p plied with a silver contact area of approximately one inch that the original GE AK circuit breaker finger clusters make electrical contact. For most environments the silver plating provides a higher conductive material to maintain a high quality electrical connection for long periods of time. To ensure the reliability of the switchgear, periodic preventative maintenance (PM) actions (e.g., cleaning , bolt torqueing, connection resistance checks , etc.) must be performed . From 1997 to the present, the PM procedure for the inspection and maintenance of mode l AKD-5 480 Vac switchgear contained ins t ruct i ons to clean and inspect the bus side of the switchgear; however, the FCS PM strategy has not included the bus side inspections of the switchgea The switchgear design is such that access to the bus compartment of the switchgear is extremely diff i cult and F CS PM procedures did not contain sufficient instructions to remove the switchgear bus compartment inspection covers. The electrical maintenance department incorrectly
'interpreted the lack of instructions to mean that bus compartment maintenance was not required and maintenance was performed only in accessible areas of the switchgea The requirement to periodically inspect the bus compartment has been opposed due to these switchgear access restriction The reason for the violation is a procedural gap between the vendor and industry recommended cleaning, inspection, and testing recommendation OPPD instituted Reliability Centered Maintenance (RCM) in 1991. RCM performed a rigorous of the vendor recommended maintenance at the task level. RCM used Failure Modes Effect A n alysis to look at how the equipment could fail. RCM then used the vendor manual to create a PM program designed to prevent the failure modes identifie In 2006, OPPD began to use the Equipment Reliability Optimization Program (EROP) to institute changes to the PM program to improve the reliability of critical equipment, including circuit breaker The EROP established critical equipment and determined maintenance frequencies by using industry best practice This review was conducted at a high l evel and did not review specific tasks required to accomplish the high level PM objective Subsequent reviews and the EROP failed to identify task level vendor recommendation LlC-12-0051 Enclasure Page 6 Previaus carrect , ive actians far bus tie circuit breaker BT-1 B3A failing to. clase i n 2008 did nat cansider procedure changes to. require switchgear panel remaval, nar were design changes made to. aUaw easier access to. the bus side af the switchgea An analysis af the FCS PI&R culture issues cancluded that flawed mental madels, misguided beliefs and misplaced values have driven, influenced, and permitted the misalignment af the individual, leader, and arganizatianal behaviars (narms) needed far effective and timely detectian, evaluatian, and correctian af perfarmance deficiencie The FCS organizatianal values regarding PI&R preclude a improving culture and learning environmen The analysis also. cancluded that: The FCS arganizatian has nat cansistently displayed the leadership and aversight skills necessary to. reinfarce expectatians and to. hold persannel accauntable for successful campletian af PI&R activities. Organizatianal leadership has designated persannel , to. perfarm and approve cause analyses withaut ensuring thase individuals have sufficient skills and knawledge to. perfarm cause analyses and to. plan salutians using a systematic methad. Significant events and equipment failures have recurred indicating weaknesses in cause analysis and timely and effective problem resalutian. Previaus carrective actian plan steps were nat develaped using a systematic change management process to. assure the right mental madel was being implemented from the start and to. assure the fallaw-through manitaring and caaching was incorporated to. anchar the desired PI&R behaviars in the field. Statian effectiveness reviews are nat canducted in a manner and to. a depth that assures that carrective actians for precluding problem repetitian have been institutianalize . Corrective Steps Taken and the Results Achieved GE 480 Vac AKO-5 switchgear was madified to. add access panels that allaw far the safe inspectian and cleaning af the AKO-5 switchgear buses. The GE 480 Vac AKO-5 switchgear bus PM procedure was revised to. include instructians for the cleaning af conductars, proper tarqueing of bolted canductor ar bus bar cannections, and inspection guidance for abnarmal connectian temperatu res. PM tasks that included the cleaning of conductors and proper tarqueing of baited canductar and bus bar cannectians were campleted for the GE AKD-5 480 Vac switchgear buses. The FCS corrective actian process was revised and implemente This program provides enhanced expectations far the FCS PI&R cultur LlC-12-0051 Enclosure Page 7 Prior to implementation of the revised corrective action process, FCS site wide training was provided for Condition Report Owners, Corrective Action Review Group members, Root Cause Analysts, Corrective Action Review Board members, Daily Screening Team members, etc. This training provided the "right picture" expectations for effectively app J ying the mental models, beliefs, values and behaviors needed for the effective and timely detection, evaluat i on, and correction of performance deficiencies. Training was provided to FCS leaders to provide the "right picture" expectations for effectively applying the mental models, beliefs, values and behaviors needed for the effective and timely detection, evaluation, and correction of p erformance deficiencies. Additional corrective actions and effectiveness reviews on PI&R culture improvements are being tracked through the FCS corrective action program. 3. Corrective Steps That Will be Taken A trending program that evaluates testing resistance measurements of the finger cluster to bus bar engagement line to load side connections of applicable switchgear du r ing preventative maintenance activities will be developed by September 15, 2012. 4. Date When Full Compliance Will be Achieved Based on the revision to the 480 Vac PM procedures and the completion of the affected 480 Vac bus PM activities, OPPD is currently in complianc LlC-12-0051 Enclosure Page 8 OPPD Response -NOV C 1. Reason for the Violation On June 7, 2011, while in mode 5 (refueling shutdown condition), a fire in 480 Vac I l oad center 1 B4A resulted in a loss of power to loads supplied from the 1 B4A load center, as well as a trip of the main supply circu l i t breaker to load center 1 B3A which is associated with the redundant train of safety-related 480 Vac power to FCS. T his was a violation of the requirements of 10 CFR 50, Appendix R, Section 1 11I..G.1.a, "Fire Protection of Safe Shutdown Capability," which requires, in part, that one train of systems necessary to achieve and maintain hot shutdown conditions be free of fire damage. During normal plant operation, 480 Vac load center main and appropriate bus tie circuit breakers are expected to remain closed to provide 480 Vac power to their associated buses. In the event of a fault on the associated bus, a load center main or bus tie circuit breaker should open to isolate the fault without opening the next circuit breaker upstream, i.e., the circuit breakers should coordinate to isolate the fault by preserving power to loads not directly impacted by the fault. The original main and bus tie GE AK-50 circuit breakers were equipped with oil dashpot ove r current trip devices. Due to reliability concerns, the oil dashpots were replaced with GE RMS 9 solid state overcurrent trip devices in 1993. Due to spurious operation of these trip devices, they were replaced with Westinghouse Amptector trip devices in 1996. Reliability improved with the Amptector trip devices; however, due to aging concerns, the circuit breakers were replaced with Square D Masterpact NW circuit breakers equipped with Micrologic overcurrent trip units in the 2009 modificatio Extensive analysis and vendor testing of the 1 B3A main and bus tie circuit breakers that were in-service at the time of the june 7, 2011, 1 B4A fire was performe The circuit breakers were tested in a configuration to replicate field conditions at the time of the fire as c'losely as possibl Approximately 12,500 amps were applied into both circuit breakers to simulate a fault. If the circuit breakers are properly coord i nated , the bus tie circuit breaker should open in approximately 0.3 seconds and the main circuit breaker should remain closed. Contrary to expectations, the main circuit breaker tripped in 0.05 seconds and the bus tie circuit breaker did not open which indicated that the circuit breakers would not coordinate when subjected to fault current. The Square D Masterpact NW circuit breaker Micrologic overcurrent trip units contain an optional Zone Selective Interlock (ZSI) that when used, allow adjacent circuit breakers to communicate with each other to minimize opening time during a fault. The ZSI feature is not part of the FCS design and was not available in the original GE circu i t breaker The consequence of not disabling the ZSI feature of LlC-12-0051 Enclosure Page 9 the main circuit breaker is that the circuit breaker will open when it senses the fault current with no intentional time delay (i.e., the main circuit breaker will trip instantaneously before the bus tie circuit breaker).
An inspection of the 1 B3A main circuit breaker wire jumpers revealed that the reason the 1 B3A main circuit breaker opened was that wire jumpers were not properly configured to disable the lSI, thus allowing the main circuit breaker to open during the 1 B4A fire instead of the 1 B3A bus tie circuit breaker. Vendor documents state that the Masterpact NW breakers are supplied with the lSI feature disable However, the cause analysis concluded that the 1 B3A circuit breaker/cradle assembly was received at FCS without the lSI feature properly disable Vendor factory acceptance testing, FCS receipt inspection, and post modification testing of the new circuit breakers failed to identify the wired jumper error on circuit breaker/cradle assembly 1 B3A, because the test module used to perform the acceptance testing bypassed the lSI zone feature . Additionally, the FCS design change process does not provide guidance to evaluate design features of new components in regard to the possibility that they may adversely affect required performance characteristics if not properly installe The following items contributed to the inadvertent tripping of 1 B3A main circuit breaker: Detailed standards for performing and documenting wire/continuity checks for new wiring do not exist. A questioning attitude by FCS personnel was not employed concerning the details of the operation of the replacement Masterpact NW circuit breakers. The Masterpact NW circuit breaker vendor manual does not clearly state the consequences of not disabling the lSI. 2. Corrective Steps Taken and the Results Achieved The 1 B3A circuit breaker lSI was disabled and the circuit breaker returned to service. The remaining 11 Masterpact NW main and bus tie circuit breaker wired jumpers were inspected and the lSI on these circuit breakers were found to be correctly disabled . Since the lSI on the remaining 11 Masterpact NW circuit breakers were properly disabled, the potential for the opening of other redundant safety-related circuit breakers did not exist at the hme of the 1 B4A fire. Circuit breaker maintenance procedures were revised to verify that the appropriate lSI remain disable LlC-12-0051 Enclosure Page 10 3. Corrective Steps That Will be Taken Appropriate design control procedures will' be revised to require FCS personnel to contrast features of new equipment with the original equipment including a consideration of potential adverse impact of new features on required performance characteristics; require modifications to test in the built condition whenever possible; and document critical parameters within the design change process. Th l is will be completed by June 15, 2012. Modifications of equipment supplied by Nuclear Logistics, Incorporated, will be reviewed to determine if they contain wiring errors that testing would not have identified . This will be completed by June 29,2012. Appropriate procedures will be revised to provide instructions for verifying new wiring installations by July 11, 2012. Lessons learned from this event will be incorporated into the design engineering risk and rigor procedure by August 15, 2012. A case study that identifies the specif , i cs of this event and reinforces the use of the human performance toolbox will be developed and provided to appropriate FCS personnel by September 15, 2012. A review of modifications that were created/implemented within a selected nine-month window will be performed to determine if failure modes introduced by features that were not part of original equipment could have been introduced will be comp'l eted by April 15,2013. A review of modifications that were created/implemented within a month window will be performed to determine if failure modes introduced by features that were not part of the original equipment could have been introduced will be completed by January 15, 2014. 4. Date When Full Compliance WiU be Achieved Based on the identification and correction of the w i ring error in circuit breaker 1 B3A, OPPD is currently in complianc LlC-12-0051 Enclosure Page 11 Regulatory Commitments Commitment Due Date CR Number Switchgear and circuit breaker training will be included in the engineering initial and continuing training program September 3, 2012 2011-5414 A trending program that evaluates testing resistance measurements of the line to load side connections of applicable switchgear during preventative maintenance activities will be develope September 15, 2012 2011-5414 Appropriate design control procedures will be revised to require FCS personne l to contrast features of new equipment with the orig l inal equipment including a cons.ideration of potential adverse impact of new features on required performance characteristics; require modifications to test in the as-built condition whenever possible, and document critical parameters within the design change process. June 15, 2012 2011-6621 Modifications of equipment supplied by Nuclear Logistics, Incorporated, will be reviewed to determine if they contain wiring errors that testing would not have identifie June 29, 2012 2011-6621 Appropriate procedures will be revised to provide instructions for verifying new wiring installations. July 11,2012 2011-6621 Lessons learned from this event will be incorporated into the design engineering risk and rigor procedur August 15, 2012 2011-6621 A case study that identifies the specifics of this event and reinforces the use of the human performance toolbox be developed and provided to appropriate FCS personne September 15, 2012 2011-6621 A review of modifications that were created/implemented within a selected nine month window will be performed to determine if failure modes introduced by features that were not part of original equipment could have been introduced will be complete April 15, 2013 2011-6621 A review of modifications that were created/implemented within a selected 18-month window will be performed to determine if failure modes introduced by features that were not part of original equipment could have been introduced will be complete January 15, 2014 2011-6621