Letter Sequence Response to RAI |
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Initiation
- Request, Request, Request, Request, Request, Request, Request, Request, Request, Request
- Acceptance, Acceptance, Acceptance, Acceptance
Results
Other: ML083030246, ML083330066, ML083640401, ML090220584, ML090650061, ML090720066, ML090720068, ML090830248, ML090860762, ML090930256, ML091070269, ML091170031, ML091830055, ML091880258, ML101040676, ML101050376, ML101270268, ML102010302, ML102020397, NLS2009099, SAMA Meteorological Anomaly Related to the Cooper Nuclear Station License Renewal Application
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MONTHYEARML0830302462008-09-24024 September 2008 Copper Nuclear Station, License Renewal Application, Appendix E, Environmental Report Project stage: Other ML0833300662008-12-19019 December 2008 Determination of Acceptability and Sufficiency for Docketing and Opportunity for a Hearing Regarding the Application from Nebraska Public Power District, for Renewal of the Operating License for the Cooper Nuclear Station Project stage: Other ML0901203602009-01-0909 January 2009 Safety Evaluation Report Project stage: Request ML0836404012009-01-21021 January 2009 Notice of Intent to Prepare an Environmental Impact Statement and Conduct Scoping Process for License Renewal for the Cooper Nuclear Station Unit 1 (TAC No. MD9763 and MD 9737) LTR Project stage: Other ML0906500612009-02-0202 February 2009 Letter from Nebraska State Historical Society Regarding Cooper Nuclear Station License Renewal Project stage: Other ML0907506862009-02-25025 February 2009 Scoping and Process Public Meeting Sides of February 25, 2009 Project stage: Request ML0908400622009-02-25025 February 2009 Transcript of Cooper Nuclear Station License Renewal Pubic Meeting - Evening Session, February 25, 2009, Pages 1-41 Project stage: Meeting ML0908400632009-02-25025 February 2009 Transcript of Cooper Nuclear Station License Renewal Public Meeting - Afternoon Session, Wednesday, February 25, 2009, Pages 1-33 Project stage: Meeting ML0907200662009-02-25025 February 2009 Comment (1) of James Gerweck, on Behalf of the Richardson County, Nebraska, Emergency Management Agency, Supporting CNS License Renewal Project stage: Other ML0907200682009-02-27027 February 2009 Comment (3) of Ashtin Paris, on Behalf of the City of Rock Port, Supporting Nebraska Public Power District'S Cooper Nuclear Station License Renewal Project stage: Other ML0908607622009-03-0909 March 2009 Letter from the Nebraska Department of Natural Resources the Cooper Nuclear Station License Renewal Project stage: Other ML0907200672009-03-10010 March 2009 Comment (2) of Alan Richard, on Behalf of Pawnee City Development Corporation, Supporting Renewal of License for Cooper Nuclear Station Project stage: Request ML0908302482009-04-0303 April 2009 Environmental Site Audit Regarding Cooper Nuclear Station Unit 1 License Renewal Application (TAC MD9763 and MD9737) Project stage: Other ML0902205842009-04-0303 April 2009 Proposed Review Schedule Regarding the Application from Nebraska Public Power District for Renewal of the Operating License for the Cooper Nuclear Station Project stage: Other ML0909302562009-04-0909 April 2009 Audit Plan for Aging Management Program Site Audit Regarding Cooper Nuclear Station Unit 1, License Renewal Application (Tac No. MD9737) Project stage: Other ML0909103082009-04-14014 April 2009 Summary of Public Environmental Scoping Meeting Related to the Review of the Cooper Nuclear Station, Licensed Renewal Application Project stage: Meeting ML0910702692009-04-16016 April 2009 EPA Comment on the Cooper Nuclear Station License Renewal Application Project stage: Other ML0911700312009-04-28028 April 2009 Environmental Site Audit Regarding Cooper Nuclear Station Unit 1 License Renewal Application Project stage: Other ML0909704142009-04-30030 April 2009 Summary of Site Audit Related to the Review of the License Review Application for Cooper Nuclear Station, Unit 1 Project stage: Approval ML0911905972009-05-0101 May 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application (TAC No. MD9763 and MD9737) Project stage: RAI NLS2009039, Response to Request for Additional Information for License Renewal Application - Balance-of-Plant Scoping and Screening2009-05-28028 May 2009 Response to Request for Additional Information for License Renewal Application - Balance-of-Plant Scoping and Screening Project stage: Response to RAI ML0912000172009-05-29029 May 2009 Issuance of Environmental Scoping Summary Report Associated with the Staff'S Review of the Application by the Nebraska Public Power District, for Renewal of the Operating License for Cooper Nuclear Station Unit 1 Project stage: Approval ML0917500882009-06-0101 June 2009 CNS Lr - NDEQ 2009 Ambient Network Plan Project stage: Request ML0918300552009-06-0808 June 2009 Reply from Fish and Wildlife Service on Transmission Line for Cooper Nuclear Station License Renewal Project stage: Other ML0915303162009-06-0808 June 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0917501182009-06-11011 June 2009 CNS Lr - Tornado Occurrences in Nemaha County, Ne 1950-2009 Project stage: Request ML0913803652009-06-15015 June 2009 Audit Report Regarding the Cooper Nuclear Station, Unit 1, License Renewal Application Project stage: Acceptance Review NLS2009040, Response to Request for Additional Information for License Renewal Application - Aging Management Programs2009-06-15015 June 2009 Response to Request for Additional Information for License Renewal Application - Aging Management Programs Project stage: Response to RAI NLS2009049, Response to Request for Additional Information for License Renewal Application - Section B and C2009-06-22022 June 2009 Response to Request for Additional Information for License Renewal Application - Section B and C Project stage: Response to RAI ML0916002892009-06-29029 June 2009 Request for Additional Information for Cooper Nuclear Station License Renewal Project stage: RAI ML0916002782009-06-29029 June 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI NLS2009048, Response to Request for Additional Information for License Renewal Application Severe Accident Mitigation Alternatives2009-07-0101 July 2009 Response to Request for Additional Information for License Renewal Application Severe Accident Mitigation Alternatives Project stage: Response to RAI ML0917503682009-07-0101 July 2009 Summary of Regulatory Audit Related to the Review of the License Renewal Application for Cooper Nuclear Station Project stage: Approval ML0918802582009-07-0808 July 2009 Environment Project Manager Change for the License Renewal of Cooper Nuclear Station Project stage: Other ML0918804782009-07-14014 July 2009 Request for Additional Information Project stage: RAI ML0919005022009-07-14014 July 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0918804822009-07-14014 July 2009 Request for Additional Information for the Review of Cooper Nuclear Station License Renewal Application Project stage: RAI ML0918702982009-07-16016 July 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0918703042009-07-16016 July 2009 License Renewal Request for Additional Information Project stage: RAI ML0921600842009-07-20020 July 2009 Notice of Diane Curran'S Withdrawal of Appearance Project stage: Request ML0920902762009-07-29029 July 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application (TACs MD9763 and MD9737) Project stage: RAI NLS2009055, Response to Request for Additional Information for License Renewal Application2009-07-29029 July 2009 Response to Request for Additional Information for License Renewal Application Project stage: Response to RAI NLS2009063, Response to Request for Additional Information for License Renewal Application2009-08-17017 August 2009 Response to Request for Additional Information for License Renewal Application Project stage: Response to RAI ML0919600402009-08-19019 August 2009 Summary of Regulatory Audit Related to the Review of the License Renewal Application for Cooper Nuclear Station Project stage: Approval ML0923106542009-08-28028 August 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0926500572009-09-28028 September 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0926809352009-10-0707 October 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI ML0927300142009-10-15015 October 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI NLS2009085, Response to Request for Additional Information on License Renewal Application2009-10-22022 October 2009 Response to Request for Additional Information on License Renewal Application Project stage: Response to RAI ML0929200192009-10-29029 October 2009 Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application Project stage: RAI 2009-04-09
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Category:Letter type:NLS
MONTHYEARNLS2024006, Response to Nuclear Regulatory Commission'S Request for Additional Information for Relief Request RC3-022024-01-25025 January 2024 Response to Nuclear Regulatory Commission'S Request for Additional Information for Relief Request RC3-02 NLS2024007, Emergency Plan Implementing Procedure 5.7.1, Revision 732024-01-16016 January 2024 Emergency Plan Implementing Procedure 5.7.1, Revision 73 NLS2024003, 30 Day Report - Unauthorized Disassembly of Liquid Scintillation Detector2024-01-15015 January 2024 30 Day Report - Unauthorized Disassembly of Liquid Scintillation Detector NLS2024004, Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 20232024-01-10010 January 2024 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 2023 NLS2023053, ISFSI, Supplement to Exemption Request from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-11-30030 November 2023 ISFSI, Supplement to Exemption Request from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation NLS2023050, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-11-22022 November 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation NLS2023045, Application to Revise Technical Specifications to Adopt TSTF-374, Revision to Diesel Fuel Oil Testing Program2023-11-15015 November 2023 Application to Revise Technical Specifications to Adopt TSTF-374, Revision to Diesel Fuel Oil Testing Program NLS2023051, Response to Nuclear Regulatory Commission Request for Additional Information Regarding Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements2023-10-10010 October 2023 Response to Nuclear Regulatory Commission Request for Additional Information Regarding Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements NLS2023049, 10 CFR Part 21 Report Regarding HGA Relays2023-09-0606 September 2023 10 CFR Part 21 Report Regarding HGA Relays NLS2023029, License Amendment Request to Revise Technical Specifications to Support Inspection of Diesel Fuel Oil Storage Tanks2023-09-0606 September 2023 License Amendment Request to Revise Technical Specifications to Support Inspection of Diesel Fuel Oil Storage Tanks NLS2023047, Licensee Guarantees of Payment of Deferred Premiums2023-07-26026 July 2023 Licensee Guarantees of Payment of Deferred Premiums NLS2023033, 10 CFR 50.55a Relief Request RC3-022023-06-27027 June 2023 10 CFR 50.55a Relief Request RC3-02 NLS2023039, Preparation and Scheduling of Operator Licensing Examinations2023-06-0101 June 2023 Preparation and Scheduling of Operator Licensing Examinations NLS2023038, Nebraska Public Power District 2022 Financial Report2023-05-22022 May 2023 Nebraska Public Power District 2022 Financial Report NLS2023031, Annual Radiological Environmental Report2023-05-11011 May 2023 Annual Radiological Environmental Report NLS2023017, Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements2023-05-0303 May 2023 Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements NLS2023018, Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling2023-05-0303 May 2023 Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling NLS2023030, Annual Radioactive Effluent Release Report2023-04-27027 April 2023 Annual Radioactive Effluent Release Report NLS2023007, Technical Specification Bases Changes2023-04-17017 April 2023 Technical Specification Bases Changes NLS2023027, Annual Report of Individual Exposure Monitoring2023-04-13013 April 2023 Annual Report of Individual Exposure Monitoring NLS2023021, Quality Assurance Program Changes2023-04-10010 April 2023 Quality Assurance Program Changes NLS2023020, Decommissioning Funding2023-03-29029 March 2023 Decommissioning Funding NLS2023019, Property Insurance Coverage2023-03-23023 March 2023 Property Insurance Coverage NLS2023010, Inservice Inspection OAR-1 Owner'S Activity Report for Cooper Nuclear Station2023-02-0909 February 2023 Inservice Inspection OAR-1 Owner'S Activity Report for Cooper Nuclear Station NLS2023005, Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 20222023-01-19019 January 2023 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 2022 NLS2022054, Preparation and Scheduling of Operator Licensing Examinations2023-01-0505 January 2023 Preparation and Scheduling of Operator Licensing Examinations NLS2022055, Emergency Plan, Revision 812023-01-0404 January 2023 Emergency Plan, Revision 81 NLS2022053, CNS-2022-11 Post Exam Submittal2022-11-22022 November 2022 CNS-2022-11 Post Exam Submittal NLS2022050, Notification of Revision to Cooper Nuclear Station Emergency Response Data System Data Point Library2022-11-0909 November 2022 Notification of Revision to Cooper Nuclear Station Emergency Response Data System Data Point Library NLS2022048, Management Change and Correspondence Update2022-11-0101 November 2022 Management Change and Correspondence Update NLS2022047, Core Operating Limits Report, Cycle 33, Revision 02022-10-14014 October 2022 Core Operating Limits Report, Cycle 33, Revision 0 NLS2022042, 10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2) Summary Report2022-10-0707 October 2022 10 CFR 50.59(d)(2) and 10 CFR 72.48(d)(2) Summary Report NLS2022037, Emergency Plan, Revision 80, Summary of 50.54(q) Analyses2022-08-18018 August 2022 Emergency Plan, Revision 80, Summary of 50.54(q) Analyses NLS2022035, Evacuation Time Estimate Report for Cooper Nuclear Station2022-08-16016 August 2022 Evacuation Time Estimate Report for Cooper Nuclear Station NLS2022031, Licensee Guarantees of Payment of Deferred Premiums2022-07-19019 July 2022 Licensee Guarantees of Payment of Deferred Premiums NLS2022005, Application to Revise Technical Specifications to Adopt TSTF-554, Revision 1, Revise Reactor Coolant Leakage Requirements2022-06-16016 June 2022 Application to Revise Technical Specifications to Adopt TSTF-554, Revision 1, Revise Reactor Coolant Leakage Requirements NLS2022025, Nebraska Public Power District Letter (NLS2022010) to U.S. Nuclear Regulatory Commission Dated April 5, 2022, Annual Report of Individual Exposure Monitoring2022-06-0606 June 2022 Nebraska Public Power District Letter (NLS2022010) to U.S. Nuclear Regulatory Commission Dated April 5, 2022, Annual Report of Individual Exposure Monitoring NLS2022016, Annual Radiological Environmental Report2022-05-10010 May 2022 Annual Radiological Environmental Report NLS2022020, Nebraska Public Power District, Cooper Nuclear Station, 2021 Financial Report2022-05-0202 May 2022 Nebraska Public Power District, Cooper Nuclear Station, 2021 Financial Report NLS2022014, Annual Radioactive Effluent Release Report2022-04-27027 April 2022 Annual Radioactive Effluent Release Report NLS2022010, Annual Report of Individual Exposure Monitoring2022-04-0505 April 2022 Annual Report of Individual Exposure Monitoring NLS2022009, Property Insurance Coverage2022-03-23023 March 2022 Property Insurance Coverage NLS2022011, Preparation and Scheduling of Operator Licensing Examinations2022-03-18018 March 2022 Preparation and Scheduling of Operator Licensing Examinations NLS2022004, Response to Nuclear Regulatory Commission'S Request for Additional Information Regarding Relief Request RR5-01, Revision 12022-02-0707 February 2022 Response to Nuclear Regulatory Commission'S Request for Additional Information Regarding Relief Request RR5-01, Revision 1 NLS2022003, Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 20212022-01-20020 January 2022 Annual Report of Changes and Errors in Emergency Core Cooling System Evaluation Models for 2021 NLS2021067, ISFSI - Independent Spent Fuel Storage Installation Decommissioning Funding Plan2021-12-16016 December 2021 ISFSI - Independent Spent Fuel Storage Installation Decommissioning Funding Plan NLS2021069, Withdrawal of Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements2021-12-15015 December 2021 Withdrawal of Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements NLS2021066, Response to Nuclear Regulatory Commission'S Request for Additional Information Regarding Alternative Request RI5-02, Revision 32021-12-10010 December 2021 Response to Nuclear Regulatory Commission'S Request for Additional Information Regarding Alternative Request RI5-02, Revision 3 NLS2021065, Clarification of Response to Nuclear Regulatory Commission'S Request for Additional Information for Alternative Request RS-012021-12-0606 December 2021 Clarification of Response to Nuclear Regulatory Commission'S Request for Additional Information for Alternative Request RS-01 NLS2021056, Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements2021-11-16016 November 2021 Application to Revise Technical Specifications to Adopt TSTF-551, Revise Secondary Containment Surveillance Requirements 2024-01-25
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H Nebraska Public Power District "Always there when you need us" 54.17 NLS2009092 November 16, 2009 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555-0001
Subject:
Response to Request for Additional Information for the Review of Cooper Nuclear Station License Renewal Application Cooper Nuclear Station, Docket No. 50-298, DPR-46
References:
- 1. Letter from Tam Tran, U.S. Nuclear Regulatory Commission, to Stewart B. Minahan, Nebraska Public Power District, dated October 15, 2009, "Request for Additional Information for the Review of the Cooper Nuclear Station License Renewal Application (TAC No. MD9763 and MD9737)."
- 2. Letter from Stewart B. Minahan, Nebraska Public Power District, to U.S.
Nuclear Regulatory Commission, dated September 24, 2008, "License Renewal Application" (NLS2008071).
Dear Sir or Madam:
The purpose of this letter is for the Nebraska Public Power District to respond to the Nuclear Regulatory Commission Request for Additional Information (Reference 1) regarding the Cooper Nuclear Station License Renewal Application (Reference 2). This response is provided in the Attachment to this letter.
Should you have any questions regarding this submittal, please contact David Bremer, License Renewal Project Manager, at (402) 825-5673.
COOPER NUCLEAR STATION P.O. Box 98 / Brownville, NE 68321-0098 Telephone: (402) 825-3811 / Fax: (402) 825-5211 www nppd.com
NLS2009092 Page 2 of 2 I declare under penalty of perjury that the foregoing is true and correct.
Executed on (Date)
Sincerely, Stewart B. Minahan Vice President - Nuclear and Chief Nuclear Officer
/Wv Attachment cc: Regional Administrator w/ attachment USNRC - Region IV Cooper Project Manager w/ attachment USNRC - NRR Project Directorate IV-l Senior Resident Inspector w/ attachment USNRC - CNS Nebraska Health and Human Services w/ attachment Department of Regulation and Licensure NPG Distribution w/ attachment CNS Records w/ attachment
NLS2009092 Attachment Page 1 of 4 Attachment Response to Request for Additional Information for License Renewal Application Cooper Nuclear Station, Docket No. 50-298, DPR-46 The Nuclear Regulatory Commission (NRC) Request for Additional Information (RAI) regarding the License Renewal Application is shown in italics. The Nebraska Public Power District's (NPPD) response to this RAI is shown in block font.
NRC Request: RAI B. 1.30-2 One Time Inspection -Small Bore Piping
Background
In a letter dated May 1, 2009, the staff requested additionalinformation on how the applicant plans to address volumetric inspections of socket welds in its aging managementprogram (AMP) for American Society of Mechanical Engineers (ASME) Class] small-bore piping. In a letter datedJune 15, 2009, the applicantresponded stating that, "NUREGSection XM.M35 does not explicitly addresssocket welds. Because there is no accepted industry standardmethodfor volumetric examination of socket welds, no such examinations are included in the CNS [Cooper Nuclear Station]program." The applicantgoes on to discuss the fact that a surface inspection and visual inspection (VT-2) ofASME Class 1 small-borepiping socket welds will be performed in lieu of a volumetric inspection. Finally, the applicantstated that a review of site-specific operatingexperience had been performedand that no history of cracking in Class 1 small-bore piping, including socket welds, had been identified Issue The staff does not consider the performance of surface and VT-2 inspections to be a suitable alternative to volumetric inspections as a means of detecting cracking of socket welds in ASME Class ] small-borepiping. Specifically, these types of inspections are not effective for detecting sub-surface cracks that may exist in these welds.
It is also not clear that relevant industry operatingexperience was consideredwhen the decision was made to not perform volumetric inspectionsof these socket welds. The staffperformed a cursory review of available operatingexperience and identified several examples of socket weld failures resultingfrom cracking. Since 1997, as many as 47 socket weld failures have occurred at 35 nuclearpower plants. Aging effects identified during the cause analysis was largely cracking on the inside diameter (below the visible surface of the weld) stemmingfrom intergranularstress corrosion andfatigue. At least 12 of the 47 occurrences resulted in plant scrams or other significant operationalchallenges.
NLS2009092 Attachment Page 2 of 4 Request The staff requests the applicantprovide an AMP for detecting cracking in ASME Class 1 small-bore piping, including sub-surface cracking in socket welds. As discussed in NEI 95-10, "IndustryGuidelinesfor Implementing the Requirements of 10 CFR Part54 - The License Renewal Rule," the staff also requests that a review of relevant industry operatingexperience be conducted to determine whether it changes the conclusions drawnfrom the previously performed plant-specific determinations.
NPPD Response:
To manage the effects of aging on ASME Class 1 small-bore piping, NUREG- 1801 recommends the program described in Section XI.M35, "One-Time Inspection of ASME Code Class 1 Small-Bore Piping." NPPD credits the AMP described in NUREG-1801,Section XI.M35 to manage the effects of aging on ASME Class 1 small-bore piping at Cooper Nuclear Station (CNS). The operating experience attribute of AMP XI.M35 states:
This inspection uses volumetric inspection techniques with demonstrated capability and a proven industry record to detect cracking in piping weld and base material. However, the application of the specific technique to ASME Code Class 1 small-bore piping needs to be qualified before the examination.
In summary, NUREG-1801 AMP XI.M35 recommends volumetric testing using qualified techniques with demonstrated capability to detect cracking in small-bore piping.
For socket welds, there are no volumetric inspection techniques with demonstrated capability and a proven industry record to detect cracking in piping weld and base material. This position was reaffirmed by the staff in the following passage from the Beaver Valley license renewal Safety Evaluation Report issued on June 8, 2009 (ADAMS Accession Number ML091600216):
The staff confirms that because there is no accepted method to volumetrically inspect these welds, it has accepted visual inspection of socket welds and notes that any cracks that form in these welds would initiate from the inside diameter, which would be very difficult to detect using a volumetric technique due to the configuration of the socket welds. The staff concludes that a visual inspection at operating temperature and pressure is the only practical method for inspecting these welds.
NPPD employs visual inspection at operating temperature and pressure for inspecting ASME Class 1 small-bore piping at CNS.
In response to the staff request, a review of recent industry operating experience was performed using the NRC ADAMS database. NPPD reviewed licensee event reports (LER) from ADAMS
NLS2009092 Attachment Page 3 of 4 that contained the word "socket." The review identified 70 items of which only 22 were related to cracking of Class 1 piping socket welds. These events were the result of high-cycle fatigue cracking due to vibration or weld defects during installation. Cracking due to high-cycle fatigue is the result of improper design or installation that creates an unanalyzed condition that will lead to failure of the component early in life if not corrected. It is not related to the effects of aging.
Typical industry response to cracking caused by high-cycle fatigue is to modify the design to6 prevent recurrence including using improved socket welds and changing the installation to eliminate the vibration.
The plant shutdowns required by some of these events were the result of Technical Specification requirements regarding reactor coolant system leakage even though the size of the leaks did not impact the ability of the systems to perform their design functions. None of the LERs identified stress corrosion cracking or corrosion as the cause of the cracking.
The conclusions of this review are also supported by information published by the NRC in NUREG/CR-6936, ProbabilitiesofFailureand UncertaintyEstimate Informationfor Passive Components - A LiteratureReview, May 2007. It states:
Vibration fatigue failures are normally a result of poor piping design or installation and welding practices. A relatively large share of vibration fatigue failures initiates at the fillets of socket and support attachment welds due to a high stress concentration at the juncture of the weld and base metal. Small-bore pipe socket welded vent and drain connections less than 25.4 mm (<1.0 in.) in the immediate proximity of vibration sources tend to be most susceptible to this failure mechanism (Olson 1985; EPRI 1994 Riccardella et al, 1997; Shah et al 1998).
Unlike the previously discussed mechanisms, vibration fatigue may not always lend itself to periodic inservice examinations (i.e., volumetric, surface) as a means of managing this degradation mechanism. This is especially true if the inspections occur at the normal inservice inspection frequency of once every 10 years. The nature of this mechanism is such that, generally, almost the entire fatigue life of the component is expended during the initiation phase. Once a crack initiates, failure quickly follows. Therefore, the absence of any detectable crack may not ensure reliable component performance.
This industry operating experience supports the adequacy of the inspections of small-bore piping socket welds at CNS described in response to RAI B.1.30-1. As additional clarification to the cited response to RAI B. 1.30-1, prior to 2004 NPPD experienced socket weld cracking due to high-cycle fatigue from excessive vibration that was not related to the effects of aging. That response stated that small-bore piping and socket welds are inspected in accordance with ASME Code requirements. These Code requirements take into consideration the low safety significance of small-bore piping leakage and the predominant mechanism of high-cycle fatigue (vibration).
The inspection consists of a VT-2 visual inspection during system leakage tests each refueling
NLS2009092 Attachment Page 4 of 4 outage per the requirements of IWB-2500-1, Examination Category B-P. This type of inspection has been determined sufficient for the current period of operation and approved by the NRC under 10 CFR 50.55a. Any change in the requirements for inspections of socket welds would be addressed by a change to the ASME Code which would be adopted by CNS. Current industry and site operating experience described above have identified only cracking in small-bore socket welds due to high-cycle fatigue and provides no evidence for the need to change existing requirements for inspections of socket welds.
Through the period of extended operation, NPPD will continue to implement at CNS the requirements of ASME Code Section XI as endorsed and modified by the NRC staff in 10 CFR 50.55a. This will include any future provisions for volumetric examination of small-bore socket welds when methods for such examination are developed and endorsed by the ASME Section XI Code and the NRC staff.
4 ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS© 4
ATTACHMENT 3 LIST OF REGULATORY COMMITMENTS0 Correspondence Number: NLS2009092 The following table identifies those actions committed to by Nebraska Public Power District (NPPD) in this document. Any other actions discussed in the submittal represent intended or planned actions by NPPD. They are described for information only and are not regulatory commitments. Please notify the Licensing Manager at Cooper Nuclear Station of any questions regarding this document or any associated regulatory commitments.
COMMITMENT COMMITTED DATE COMMITMENT NUMBER OR OUTAGE None I I I I PROCEDURE 0.42 REVISION 24 PAGE 19 OF 26