View source for RS-16-052, Response to NRC Requests for Additional Information, Set 15, Dated February 16, 2016 Related to the License Renewal Application

{{Adams
| number = ML16056A232
| issue date = 02/25/2016
| title = Response to NRC Requests for Additional Information, Set 15, Dated February 16, 2016 Related to the License Renewal Application
| author name = Gallagher M
| author affiliation = Exelon Generation Co, LLC
| addressee name = 
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000373, 05000374
| license number = NPF-011, NPF-018
| contact person = 
| case reference number = RS-16-052, TAC MF5346, TAC MF5347
| document type = Letter type:RS, Response to Request for Additional Information (RAI)
| page count = 13
| project = TAC:MF5346, TAC:MF5347
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:Michael P. Gallaghe r Vice President.
License Renewal Exelon Generation Exelon Nuclear 200 Exelon Way RS-16-052 Kennett Square. PA 19348 610 765 5958 Office 610 765 5956 Fax www.exeloncorp.com michaelp.gallagher@exeloncorp.com 10 CFR 50 10 CFR 51 10 CFR 54 February 25, 2016 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington , DC 20555-0001 

==Subject:==
References
: LaSalle County Station, Units 1 and 2 Facility Operat i ng License Nos. NPF-11 and NPF-18 NRC Docket Nos. 50-373 and 50-37 4 Response to NRC Requests for Additional Information , Set 15, dated February 16, 2016 related to the LaSalle County Station , Units 1 and 2, License Renewal Application (TAC Nos. MF5347 and MF5346) 1. Letter from Michael P. Gallagher, Exelon Generation Company LLC (Exelon), to NRC Document Control Desk, dated December 9 , 2014, " Application for Renewed Operating Licenses" 2. Letter from Jeffrey S. Mitchell , US NRC to Michael P. Gallagher , Exelon, dated February 16, 2016, "Requests for Additional Information for the Review of the LaSalle County Station, Units 1 and 2 License Renewal Application 
-Set 15 (TAC Nos. MF5347 and MF5346)" In Reference 1, Exelon Generation Company, LLC (Exelon) submitted the License Renewal Application (LRA) for the LaSalle County Station (LSCS), Units 1 and 2. In Reference 2 , the NRC requested additional information to support staff review of the LRA. The Enclosure contains the response to these requests for additional information. There are no new or revised regulatory commitments contained in this letter. If you have any questions , please contact Mr. John Hufnagel , Licensing Lead, LaSalle License Renewal Project, at 610-765-5829.
February 25, 2016 U.S. Nuclear Regulatory Commission Page 2 I declare under penalty of perjury that the foregoing is true and correct. Executed on O) *JS'-20/b Respectfully, Vice President 
-License Renewal Projects Exelon Generation Company, LLC 

==Enclosure:==
Response to Set 15 Requests for Additional Information cc: Regional Administrator 
-NRC Region Ill NRC Project Manager (Safety Review), NRR-DLR NRC Project Manager (Environmental Review), NRR-DLR NRC Project Manager, NRR-DORL-LaSalle County Station NRC Senior Resident Inspector, LaSalle County Station Illinois Emergency Management Agency -Division of Nuclear Safety RS-16-052 Enclosure Page 1 of 11 Enclosure Response to Set 15 Requests for Additional Information related to the  LaSalle County Station (LSCS) License Renewal Application (LRA)
RAI B.2.1.4-1 RAI B.2.1.7-3b

RS-16-052 Enclosure Page 2 of 11 RAI B.2.1.4-1 

==Background:==
During the IP-71002, "License Renewal Inspection," at LaSalle County Station, Units 1 and 2 (LSCS), NRC inspectors reviewed Exelon Proc edure ER-AB-331, Revision 14, "BWR Internals Program Management."  This procedure addresses changes to the enhanced visual examination (EVT-1) requirements in boiling water reactor vessel and internals project (BWRVIP)-03, "Reactor Pressure Vessel and Internals Examination Requirements."    of Exelon Procedure ER-AB-331, "Exelon Position on EVT-1 Implementation,"
states that changes relating to limitations on the allowable viewing angle have reduced the effective weld coverage to zero percent in some cases. It also states that "EVT-1 inspections of required welds and components that yield an effective coverage of zero percent meet the BWRVIP inspection requirements," because "the BWRVIP guidelines impose no minimum required effective inspection coverage" for EVT-1 examinations. As noted in the Aging Management Program (AMP) Audit report, dated September 22, 2015, ER-AB-331 is used by the BWR Vessel ID Attachment Welds and BWR Vessel Internals AMPs. The examination requirements for American Society of Mechanical Engineers (ASME) Section XI, for Category B-N-2 only refers to "accessible welds," and does not reference a specific figure for examination surface or volume, which could be interpreted as not being a "defined surface or volume" and therefore, not being subject to the ASME Code requirement for "essentially 100 percent coverage."  However, the staff's Final License Renewal Safety Evaluation Report for BWRVIP-48 (included with BWRVIP-48-A, under BWRVIP Inspection Guidelines) states "The examination volumes are limited to the attachment weld and the adjacent heat-affected regions of the vessel clad."  Based on the statement in the staff's safety evaluation, the accessible welds and the adjacent heat-affected regions of the vessel clad associated with BWR Vessel ID Attachment Welds program are considered a "defined surface or volume."  Therefore, it is the staff's expectation that examinations performed on the accessible welds will yield essentially 100 percent coverage, which the staff considers to be 90 percent or greater coverage. BWRVIP is one of the issue programs (IPs) included in NEI 03-08, Rev. 2, "Guideline for Management of Materials Issues."  As stated in NEI 03-08, "All utilities shall adopt applicable IP work products in accordance with the expected level of implementation, or provide an appropriate justification for any deviations." Issue: Although not addressed in BWRVIP guidelines, the staff's expectation is that the examination coverage of inspections performed for AMPs based on BWRVIP guidance (i.e., Generic Aging Lessons Learned (GALL) Report AMP XI.M4 "BWR Vessel ID Attachment Welds,") would be in accordance with the ASME Code. Because some BWRVIP guidelines do not address minimum required effective examination coverage, it is unclear to the staff whether limited coverage (i.e., less than 90 percent) is considered a deviation from the BWRVIP's expected level of implementation. In that regard, it is also unclear to the staff whether examination coverage of zero percent meets the BWRVIP's expected level of implementation. Based on this, crediting weld inspections that do not meet essentially 100 percent coverage (i.e., at least 90 percent of RS-16-052 Enclosure Page 3 of 11 the accessible weld), without disposition or justification, is inconsistent with the staff's expectation for implementation of the BWRVIP-based programs during the period of extended operation.
Request: 1. For the vessel ID attachment welds that include guidelines associated with the BWRVIP and rely on EVT-1 examinations, provide a summary of the locations where EVT-1 examinations are performed, indicate whether Alloy 182 welds are included, and the percent coverage for these examinations that can be qualified in accordance with the latest revision of BWRVIP-03. 2. For vessel ID attachment weld locations, where examination coverage is expected to be less than 90 percent during the period of extended operation, provide the technical basis regarding the limited inspection coverage, and its adequacy to detect aging degradation prior to loss of intended function(s). 3. For vessel ID attachment welds, provide a summary of the operating experience related to detected flaws, and the results of any flaw analyses, or other evaluations that may offer insights into flaw sizes that can be tolerated. 4. Describe how inspection results that credit EVT-1 examinations (for vessel ID attachment welds) with minimal coverage (i.e., essentially zero percent coverage) will be documented and justified during the period of extended operation. 5. State whether deviation reports will be submitted for inspection results for vessel attachment welds that credit examinations with limited coverage (e.g., less than 90 percent of accessible welds). If deviation reports will not be submitted, justify how the BWRVIP will provide adequate oversight of the effectiveness of the BWR Vessel ID Attachment Welds.
Exelon Response 1. The following tables provide a summary of the locations where EVT-1 examinations were performed for the LaSalle Unit 1 and Unit 2 vessel ID attachment welds in accordance with BWRVIP-48-A. Table 1 provides a summary of EVT-1 examination coverage of vessel ID attachment welds for Unit 1. Table 2 provides a summary of EVT-1 examination coverage of vessel ID attachment welds for Unit 2. All examinations were performed in accordance with the latest revision of BWRVIP-03 at the time of the examination. BWRVIP-03, Revision 10 implemented a requirement that the angle of inspection must not exceed 30 degrees from perpendicular to the examination surface to meet the qualification requirements of EVT-1.
Prior to the implementation of BWRVIP-03, Revision 10, the angle of inspection could be as much as 60 degrees from perpendicular to the surface, the same as required for ASME Code Section XI VT-1 examinations. This change was made to enhance the EVT-1 examination method to better identify tight cracks that are characteristic of intergranular stress corrosion cracking (IGSCC). For a visual examination to be qualified as EVT-1, requirements for surface cleanliness and limitations on camera scanning speed must also be met. EVT-1 invokes the same requirement as VT-1, as defined in current ASME Code Section XI, for demonstration of character resolution.
RS-16-052 Enclosure Page 4 of 11 BWRVIP-03, Revision 10 was implemented for the first time at LaSalle for the Unit 2 refueling outage in 2009 and for the Unit 1 refueling outage in 2010. The following 

tables provide EVT-1 examination coverage for examinations performed prior to 2009, and also from 2009 through 2015, showing the decrease in EVT-1 coverage that resulted from the more restrictive angle of inspection that was implemented in 2009. Visual examinations are performed on the entire (100 percent) accessible surface of the vessel ID attachment weld, however only the percentage of the entire (accessible +
inaccessible) weld surface and adjacent base metal, where the examination requirements for EVT-1 can be met, is reported as the percentage of examination coverage. The accessible surface of the weld where not all of the EVT-1 examination requirements can be met is visually examined by a qualified NDE (Non-Destructive Examination) specialist, in accordance with site procedures and the guidance within BWRVIP-48-A and BWRVIP-03. For example, if a weld is 10 inches long and 9 inches of the weld is accessible for visual examination, and the examination requirements for EVT-1 can only be met for 7 inches of the weld, then 70 percent is reported as the EVT-1 examination coverage. The remaining accessible 2 inches is visually examined, but not to EVT-1 requirements.
TABLE 1  Unit 1 BWR Vessel ID Atta chment Weld Examinations Vessel ID Attachment Weld Location Exams 2004 through 2008 Exams 2009 through 2015 Number of EVT-1 weld exams Average EVT-1 Coverage Number of EVT-1 weld exams Average EVT-1 Coverage Minimum EVT-1 Coverage Core Spray Piping Brackets 8 88% 4 65% 65% Jet Pump Riser Braces  30 99% 18 74% 70% Steam Dryer Support Brackets 8 100% None performed; Next examinations are  scheduled in 2016  Feedwater Sparger Brackets 14 69% None performed; Next examinations are scheduled in 2016  Total / Overall Average 60 91% 22 72% NA 

RS-16-052 Enclosure Page 5 of 11 TABLE 2  Unit 2 BWR Vessel ID Atta chment Weld Examinations Vessel ID Attachment Weld Location Exams 2004 through 2008 Exams 2009 through 2015 Number of EVT-1 weld exams Average EVT-1 Coverage Number of EVT-1 weld exams Average EVT-1 Coverage Minimum EVT-1 Coverage Core Spray Piping Brackets 10 86% 8 64% 60% Jet Pump Riser Braces 22 92% 10 70% 70% Steam Dryer Support Brackets 4 100% 4 96% 90% Feedwater Sparger Brackets 12 73% 12 53% 30% Total / Overall Average 48 87% 34 66% NA EVT-1 examination coverages of less than 100 percent are caused by physical interferences or component geometry such that the camera used for visual examination cannot be positioned close enough or within the required angle of inspection to the examination surface. The data shows that prior to 2009, qualified EVT-1 examination coverage averaged approximately 89 percent of the entire weld surface for the vessel ID attachment welds; whereas from 2009 to 2015, EVT-1 qualified examination coverage averaged approximately 68 percent. This reduc tion was caused by the EVT-1 required angle of inspection being reduced from 60 degrees to 30 degrees. In all cases the entire accessible weld surface was visually examined. Review of available records indicates that most of the LaSalle vessel ID attachment welds that are examined using the EVT-1 examination method are at least partially fabricated with Alloy 182 material that is susceptible to IGSCC. The EVT-1 examination method was developed to provide more effective visual examination that can detect tight cracks that are characteristic of IGSCC in reactor internal welds.
: 2. If the qualification requirements for the EVT-1 examination method remain unchanged during the period of extended operation, then the EVT-1 examination coverages for vessel ID attachment welds are expected to be consistent with those reported for the period of 2009 through 2015, as shown in Tables 1 and 2. The technical bases for limited EVT-1 examination coverage (less than 90 percent of the entire weld surface) being adequate to detect aging degradation prior to loss of intended function are as follows:
RS-16-052 Enclosure Page 6 of 11 GALL Report AMP XI.M4, Element 4, Detection of Aging Effects, recommends examination in accordance with ASME Section XI, Subsection IWB, Examination Category B-N-2, supplemented with the inspection guidelines within BWRVIP-48-A and BWRVIP-03. ASME Section XI, Table IWB-2500-1, Examination Category B-N-2 requires examination of the accessible reactor vessel interior attachment welds. VT-1 is to be performed on attachment welds within the beltline and VT-3 is to be performed on welds outside the beltline. Section XI, IWA-2200(c) states that when performing "... examination on a component with a defined surface or volume, essentially 100% of the defined volume shall be examined. Essentially 100% coverage is achieved when the applicable examination coverage is greater than 90%; however ..."   This 90 percent coverage requirement does not apply to ASME Code inspection of the vessel ID attachment welds since the "Examination Requirements/Figure No."
column in Table IWB-2500-1, Exam Category B-N-2 for vessel ID attachment welds, does not refer to a figure that defines the surface or volume; and instead it states that the "accessible welds" are required to be examined. Therefore, ASME Code requires 100 percent examination coverage of the surface of the vessel ID attachment welds that is accessible when using the specified visual examination method (i.e., VT-1 only or VT-3 only). LaSalle is committed to implement the examination requirements for vessel ID attachment welds in accordance with BWRVIP-48-A and BWRVIP-03. Since the examination methods directed for use in BWRVIP-48-A and BWRVIP-03 for some of the vessel ID attachment welds are different than those specified within ASME Code Section XI (i.e., EVT-1 instead of VT-1 or VT-3), Exelon applied for, and on April 30, 2008 was granted relief in accordance with 10 CFR 50.55(a), from certain ASME Code requirements. LaSalle is currently authorized to perform these examinations in accordance with BWRVIP-48-A and BWRVIP-03 as an alternate to certain ASME Code requirements. BWRVIP-48-A requires a different examination method for certain vessel ID attachment welds, but does not address required examination coverage for the welds. For EVT-1 examinations, the current revision (Revision 18) of BWRVIP-03, Section 2.5, "Generic Standards for Visual Inspection of Reactor Pressure Vessel Internals, Components, and Associated Repairs," subsection 6.4.1, which applies to visual examination of reactor internal components and welds, states "The area of interest for components shall consist of all accessible surfaces of the component."  Subsection 6.4.1 continues to clarify that for welds the area of interest includes adjacent base metal. Since the BWRVIP examination coverage requirement is "The area of interest for components shall consist of all accessible surfaces of the component,"
and the ASME Code examination coverage requirement is "accessible welds," the examination coverage requirement is the same; that is, accessible surfaces. Therefore, BWRVIP-48-A and BWRVIP-03 do not change the examination coverage requirement from ASME Code Section XI requirements that are discussed above. However, as noted above, the examination methods directed for use in BWRVIP-48-A and BWRVIP-03 for certain vessel ID attachment welds are different, that is EVT-1, than those specified within ASME Code Section XI, which is VT-1 or VT-3. The EVT-1 examination method was developed to provide a more effective visual RS-16-052 Enclosure Page 7 of 11 examination to detect tight cracks that are characteristic of IGSCC in reactor internal welds. BWRVIP-03 and the procedure used to perform EVT-1 at LaSalle require examination of the entire (100 percent) accessible examination surface; however only the percentage of the entire (accessible + inaccessible) weld surface where the examination requirements for EVT-1 can be met is reported as the percentage of examination coverage. The accessible weld surface where not all the EVT-1 examination can be met is visually examined by a qualified NDE specialist. Since EVT-1 has been demonstrated to be more effective at detecting tight cracks that are characteristic of IGSCC, it is specified within BWRVIP-48-A as the examination method for vessel ID attachment welds that are most susceptible to IGSCC. The examination is performed by a NDE specialist qualified to at least Level II, independently reviewed by a qualified Level II or III NDE specialist, and oversight is provided by an Exelon representative. The training and qualification standards required for the examiner and independent reviewer provide assurance that the proper EVT-1 examination coverage is documented in accordance with procedure requirements. In summary, although limited EVT-1 examination coverage (less than 90 percent of the entire weld surface) may be reported for some vessel ID attachment welds; those examinations are adequate to detect aging degradation prior to loss of intended function.
The EVT-1 method is the nuclear industry standard for visual examination to detect IGSCC cracks. The implementing procedures for EVT-1 examination require visual examination of the entire accessible weld surface and qualifying the EVT-1 examination to the maximum extent practical coverage. Although LaSalle implements a NRC-approved ASME Code alternative for the current 10-year inservice inspection interval to perform examinations of vessel ID attachment welds in accordance with BWRVIP-48-A in lieu of ASME Code requirements, the alternative involves implementing a more effective visual examination method for certain welds and the ASME Code Section XI requirement to inspect the accessible welds is met. 3. Cracking indications have not been detected in any LaSalle Unit 1 or Unit 2 vessel ID attachment welds during their operating history. Therefore, there have not been any flaw analyses or other evaluations performed to determine the maximum flaw sizes that can be tolerated. There also has not been any operating experience of cracking caused by IGSCC in vessel ID attachment welds within the domestic BWR fleet. As discussed within BWRVIP-48-A, there was one domestic BWR that detected cracking in a steam dryer support bracket that was caused by fatigue. The causes of that event did not have generic implications for other BWRs. The following guidance for evaluating flaws detected in vessel ID attachment welds is provided in BWRVIP-48-A. If cracking is detected in a vessel ID attachment weld, the flaw would be evaluated using the acceptance criteria within ASME Section XI, IWB-3140 and the examination standards within ASME Section XI, IWB-3520. If the acceptance criteria for the flaw are not met, then the flaw would be evaluated in accordance with ASME Section XI, IWB-3600 for acceptability, which includes RS-16-052 Enclosure Page 8 of 11 determining the maximum allowable flaw size at the flaw location and comparing that to the existing flaw, including flaw growth. 4. LaSalle operating experience, as summarized in Tables 1 and 2, indicates that EVT-1 examinations of vessel ID attachment welds with essentially zero percent coverage have not been credited in the past, and are not expected to occur or be credited during the period of extended operation. Exelon has revised the referenced procedure ER-AB-331 to delete discussion of the possibility of zero percent EVT-1 examination coverage being acceptable. The procedure has been revised to require that when EVT-1 or VT-1 method is specified, the entire accessible surface of the weld or components is to be visually examined and the specified method (EVT-1 or VT-1) is to be performed to the maximum extent practical given the qualifications requirements for the specified visual examination method. This is consistent with the current revision of BWRVIP-03 (Revision 18) and the implementing procedure us ed at LaSalle for EVT-1 examination of vessel internals. The procedure has been revised to clarify that if a visual examination of a reactor internal component results in zero percent EVT-1 examination coverage, the condition would be entered into the corrective action program and evaluated for whether a BWRVIP deviation report would be required. As shown in Tables 1 and 2 above, the minimum historical EVT-1 coverage is 30 percent for a Unit 2 feedwater sparger 

attachment weld and the average EVT-1 examination coverages are approximately 68 percent for vessel ID attachment welds. Therefore, it is not expected that any EVT-1 examinations of vessel ID attachment welds would approach essentially zero percent examination coverage during the period of extended operation. 5. As discussed in NEI 03-08, Revision 2, BWRVIP deviation reports are required to be submitted if "mandatory" or "needed" work product elements are not being implemented consistent with the intent of the BWRVIP guidance. Exelon implementing procedures require submittal of deviation reports consistent with this guidance. It is expected that during the period of extended operation, the EVT-1 examination coverages will be typical of those reported in Table 1 and 2 above. The LaSalle implementing procedures for 

performing visual examination of reactor vessel internals require that when EVT-1 or VT-1 method is specified, the entire (100 percent) accessible surface of the weld or components is to be visually examined and the specified method (EVT-1 or VT-1) is to be performed to the maximum extent practical given the qualifications requirements for specified visual examination method. This is consistent with BWRVIP-48-A and the current revision of BWRVIP-03 (Revision 18). The BWRVIP provides adequate oversight of the effectiveness of the BWR Vessel ID Attachment Welds aging management program by utilizing INPO to review the implementation of the overall BWRVIP program as discussed in NEI 03-08 Revision 2.
The BWRVIP program includes aging management of the vessel ID attachment welds as defined in BWRVIP-48-A and BWRVIP-03. Specific activities include participation in periodic comprehensive on-site assessments of program implementation, monitoring, review and analysis of industry operating experience, and providing industry updates to the industry on trends in performance in implementing the program. Also, the results of reactor in-vessel examinations are provided to the BWRVIP following each refueling outage.
RS-16-052 Enclosure Page 9 of 11 RAI B.2.1.7-3b 

==Background:==
By letters dated June 25, 2015, and September 15, 2015, Exelon responded to requests for additional information (RAIs) B.2.1.7-3 and B.2.1.7-3a regarding limited examination coverage for inspections of welds associated with the BWR Stress Corrosion Cracking AMP and NRC Generic Letter (GL) 88-01. Exelon's responses indicate that additional inspections to compensate for limited examination coverage are not necessary to manage cracking due to intergranular stress corrosion cracking during the period of extended operation. As discussed in the initial RAI, GL 88-01 states, "Examinations performed under the Scope of this letter should comply with the applicable Edition and Addenda of the ASME Code, Section XI, as specified in paragraph (g), 'Inservice Inspection (ISI) Requirements' of 10 CFR 50.55a, Codes and Standards, or as otherwise approved by the NRC."  In addition, the required volume for ASME Code examinations is defined as more than 90 percent of the specified volume. Based on information from LSCS's docketed ISI reports, the examination coverage for a number of GL 88-01 welds is only 50 percent. Although the staff-approved BWRVIP-75-A, "Technical Basis for Revisions to Generic Letter 88-01 Inspection Schedules," allows for modifications to the inspection extent and schedule described in GL 88-01, the modification to the inspection extent only applies to the number of welds being inspected, not the extent of examination coverage. BWRVIP-75-A does not specifically address the minimum required effective examination coverage. Issue: Although not explicitly addressed in BWRVIP-75-A, the staff's expectation has been that the examination coverage of inspections performed for AMPs consistent with GALL Report AMP XI.M7 "BWR Stress Corrosion Cracking," would be the same as that required by the ASME Code (i.e., greater than 90 percent). BWRVIP-75-A includes a discussion about the sampling percentages from ASME Section XI Inspection requirements and notes that ASME Section XI has been the ISI mechanism for assuring a robust reactor coolant system boundary and an adequate level of plant safety. Crediting weld inspections that do not meet the required ASME Code examination coverage without specific documented justification is inconsistent with the staff's expectation for implementation of the BWR Stress Corrosion Cracking program, during the period of extended operation. Since a minimum extent of effective examination coverage is not specified in BWRVIP-75-A, it is unclear to the staff what percentage of examination volume coverage Exelon considers as "inspected" for a weld examination that will be credited under the BWR Stress Corrosion Cracking program. Although Exelon has not considered additional weld inspections as being necessary to compensate for limited examination coverage, it is unclear to the staff that sufficient bases will be documented and independently reviewed to justify the limited examination coverage, where less than 90 percent of a weld has been examined. The staff considers sufficient bases, as information comparable to that which would be included in a relief request, had the inspection been an ASME Code examination.
RS-16-052 Enclosure Page 10 of 11 Request: 1. State the minimum percentage of weld volume examination coverage for a single weld to be considered "inspected" under the BWR Stress Corrosion Cracking program, during the period of extended operation. If the minimum examination volume coverage percentage for crediting a weld as "inspected" is less than 90 percent, provide the technical basis to show that "adequate levels of piping integrity and reliability" will be achieved, as discussed in GL 88-01. 2. For each inspection performed under the BWR Stress Corrosion Cracking program, which will credit weld examinations with less than 90 percent coverage (during the period of extended operation),  a. state whether documentation will be available onsite that provides the justification for the limitation, and whether the documentation will be independently reviewed 

to validate the justification, b. if documentation discussed in a) above will not be available, identify the controls that will be established to justify the limited weld examinations.
Exelon Response
: 1. The minimum percentage of weld volume examination coverage for a single weld to be considered "inspected" under the current GL 88-01 program and BWR Stress Corrosion Cracking program during the period of extended operation is greater than 90 percent, unless the bases for accepting the limited coverage is evaluated and documented. As discussed in the response to RAI B.2.1.7-3a, all volumetric examinations under the BWR Stress Corrosion Cracking program are performed using current Performance Demonstration Initiative (PDI) methods and procedures. For certain weld configurations, due to the specific contour of the weld or other interferences to the equipment used to perform the examination, the PDI method can only provide qualified and reliable examination results for a limited examination volume of the weld that may be less than or equal to 90 percent. For welds with less than or equal to 90 percent examination coverage to be considered "inspected" during the period of extended operation under the BWR Stress Corrosion Cracking program, the condition will be evaluated as discussed below. The current Exelon implementing procedure for inservice inspection of welds requires generation of a corrective action issue report with related documentation and disposition for weld examinations that have limited examination coverage (i.e., less than or equal to 90 percent). If the examination is credited to meet ASME Section XI Inservice Inspection requirements, then the procedure also requires justifying the adequacy of the limited examination coverage in a relief request from ASME Code Section XI inservice inspection requirements. The procedure also specifies actions to ensure that the examination coverage is maximized to the extent practical. The procedure will be revised to improve clarity for the extent of evaluation required when examination coverage is less than or equal to 90 percent for weld examinations that are only credited under the BWR Stress Corrosion Cracking program (i.e., not credited to meet ASME Code Section XI requirements). This guidance will require performing an Engineering Technical Evaluation that includes content comparable with that which would be RS-16-052 Enclosure Page 11 of 11 included in a relief request, had the inspection been an ASME Code examination. Welds with less than or equal to 90 percent coverage, that are examined to the maximum examination coverage attainable using the PDI methods and procedures, may be considered "inspected" under the BWR Stress Corrosion Cracking program if the Engineering Technical Evaluation provides a documented bases that is comparable with the content of a relief request, had the inspection been an ASME Code examination. 2. a. For each weld examination performed during the period of extended operation under the BWR Stress Corrosion Cracking program, which will credit examinations with less than or equal to 90 percent coverage, documentation will be available onsite that provides the justification for the limitation. As discussed in the response to request 1 above, if the weld examination is also credited to meet ASME Code Section XI inservice inspection requirements, a relief request from ASME Code requirements that provides the justification for the limitation will be submitted for NRC approval. For weld examinations that are only credited under the BWR Stress Corrosion Cracking program, an Engineering Technical Evaluation will provide the justification for the limited examination coverage as adequate to credit the weld examination. Procedural guidance for Engineering Technical Evaluations requires safety-related Engineering Technical Evaluations to be independently reviewed and maintained as permanent plant records. Since 

all welds examined under the BWR Stress Corrosion Cracking program are safety-related, the Engineering Technical Evaluations that provide the justification for the limited examination coverage will be independently reviewed, retained, and available for onsite review. b. As discussed in the response to request 2a, the documentation that provides the justification for the limited examination coverage being adequate to credit the weld examination during the period of extended operation will be available as a permanent plant record.}}