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Category:Letter type:WO
MONTHYEARWO 23-0002, Operating Corp., Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-0082023-12-26026 December 2023 Operating Corp., Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-008 WO 23-0014, Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations2023-05-17017 May 2023 Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations WO 23-0009, Financial Protection Levels2023-03-31031 March 2023 Financial Protection Levels WO 22-0056, Operating Corporations Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-0082022-12-19019 December 2022 Operating Corporations Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-008 WO 22-0021, Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report2022-08-29029 August 2022 Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report WO 22-0015, Generation Station - Guarantee of Payment of Deferred Premiums2022-05-0606 May 2022 Generation Station - Guarantee of Payment of Deferred Premiums WO 22-0011, Operating Corp., Financial Protection Levels2022-03-29029 March 2022 Operating Corp., Financial Protection Levels WO 22-0007, Response to NRC Regulatory Issue Summary 2022-01, Preparation and Scheduling of Operator Licensing Examinations2022-03-0909 March 2022 Response to NRC Regulatory Issue Summary 2022-01, Preparation and Scheduling of Operator Licensing Examinations WO 21-0064, Operating Corporation, Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-0082021-12-29029 December 2021 Operating Corporation, Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-008 WO 21-0031, (Wcgs), Supplement to One-Time Request for Exemption from the Biennial Emergency Preparedness2021-08-12012 August 2021 (Wcgs), Supplement to One-Time Request for Exemption from the Biennial Emergency Preparedness WO 21-0027, One-Time Request for Exemption from the Biennial Emergency Preparedness2021-07-29029 July 2021 One-Time Request for Exemption from the Biennial Emergency Preparedness WO 21-0015, License Amendment Request (LAR) for Revision to the Emergency Plan2021-05-25025 May 2021 License Amendment Request (LAR) for Revision to the Emergency Plan WO 21-0020, Operating Corp - Guarantee of Payment of Deferred Premiums2021-05-0707 May 2021 Operating Corp - Guarantee of Payment of Deferred Premiums WO 21-0019, Operating Corp Response to NRC Regulatory Issue Summary 2021-01, Preparation and Scheduling of Operator Licensing Examinations2021-04-14014 April 2021 Operating Corp Response to NRC Regulatory Issue Summary 2021-01, Preparation and Scheduling of Operator Licensing Examinations WO 21-0014, Financial Protection Levels2021-03-30030 March 2021 Financial Protection Levels WO 21-0010, Submittal of Revision 34 to Updated Safety Analysis Report2021-03-11011 March 2021 Submittal of Revision 34 to Updated Safety Analysis Report WO 21-0002, Notification of Readiness for Supplemental Inspection 927232021-01-28028 January 2021 Notification of Readiness for Supplemental Inspection 92723 WO 20-0058, Operating Corporation'S Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-0082020-12-23023 December 2020 Operating Corporation'S Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-008 WO 20-0050, License Amendment Request to Revise Technical Specification 3.6.3 and Surveillance Requirement 3.6.3.1 to Allow Use of a Blind Flange2020-11-10010 November 2020 License Amendment Request to Revise Technical Specification 3.6.3 and Surveillance Requirement 3.6.3.1 to Allow Use of a Blind Flange WO 20-0040, Corrected Revision 33 of the Wolf Creek Generating Station Updated Safety Analysis Report2020-07-23023 July 2020 Corrected Revision 33 of the Wolf Creek Generating Station Updated Safety Analysis Report WO 20-0048, Request for Notice of Enforcement Discretion for Technical Specifications 3.8.1, AC Sources - Operating2020-06-30030 June 2020 Request for Notice of Enforcement Discretion for Technical Specifications 3.8.1, AC Sources - Operating WO 20-0047, Guarantee of Payment of Deferred Premiums2020-05-0707 May 2020 Guarantee of Payment of Deferred Premiums WO 20-0029, License Amendment Request to Revise Specification 5.5.16 for Permanent Extension of Type a and Type C Leak Rate Test Frequencies2020-04-20020 April 2020 License Amendment Request to Revise Specification 5.5.16 for Permanent Extension of Type a and Type C Leak Rate Test Frequencies WO 20-0024, Financial Protection Levels2020-03-31031 March 2020 Financial Protection Levels WO 19-0059, Docket No. 50-482: Wolf Creek Nuclear Operating Corporation'S Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-0082019-12-23023 December 2019 Docket No. 50-482: Wolf Creek Nuclear Operating Corporation'S Summary of Actions Implemented for EA-18-165, Confirmatory Order, NRC Inspection Report 05000482/2019010 and NRC Investigation Report 4-2018-008 WO 19-0033, License Amendment Request for Revision to Technical Specification 3.7.5, Auxiliary Feedwater (AFW) System2019-08-29029 August 2019 License Amendment Request for Revision to Technical Specification 3.7.5, Auxiliary Feedwater (AFW) System WO 19-0031, Supplement 1 to Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules, Revision 42019-08-0808 August 2019 Supplement 1 to Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules, Revision 4 WO 19-0011, Financial Protection Levels2019-03-27027 March 2019 Financial Protection Levels WO 19-0013, Supplement to Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules, Revision 42019-03-11011 March 2019 Supplement to Application to Revise Technical Specifications to Adopt TSTF-529, Clarify Use and Application Rules, Revision 4 WO 18-0045, Submittal of Response to Requests for Additional Information (RAI) Regarding License Amendment Request (LAR) for Revision to the Emergency Plan2018-11-19019 November 2018 Submittal of Response to Requests for Additional Information (RAI) Regarding License Amendment Request (LAR) for Revision to the Emergency Plan WO 18-0047, Timeline for Response to RAI for License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term2018-11-15015 November 2018 Timeline for Response to RAI for License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term WO 18-0044, Clean Revised Technical Specification Pages for License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term2018-11-15015 November 2018 Clean Revised Technical Specification Pages for License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term WO 18-0036, Operating Corporation (WCNOC) - Notification of Readiness for Supplemental Inspection2018-08-15015 August 2018 Operating Corporation (WCNOC) - Notification of Readiness for Supplemental Inspection WO 18-0034, Operating Corp., Additional Supplement to License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term2018-08-0909 August 2018 Operating Corp., Additional Supplement to License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of Alternative Source Term WO 18-0031, Inservice Inspection (ISI) Program Relief Request from the Requirements of American Society of Mechanical Engineers (ASME) Code Case N-666-1, Weld Overlay of Class 1, 2, and 3 Socket Welded Connections, Section XI, Division 12018-07-23023 July 2018 Inservice Inspection (ISI) Program Relief Request from the Requirements of American Society of Mechanical Engineers (ASME) Code Case N-666-1, Weld Overlay of Class 1, 2, and 3 Socket Welded Connections, Section XI, Division 1 WO 18-0016, License Amendment Request for Revision to the Emergency Plan2018-05-0909 May 2018 License Amendment Request for Revision to the Emergency Plan WO 18-0014, Response to NRC Regulatory Issue Summary 2018-02, Preparation and Scheduling of Operator Licensing Examinations2018-04-16016 April 2018 Response to NRC Regulatory Issue Summary 2018-02, Preparation and Scheduling of Operator Licensing Examinations WO 18-0015, Financial Assurance Requirements for Decommissioning Nuclear Power Reactors 10 CFR 50.75(f)(1)2018-04-0505 April 2018 Financial Assurance Requirements for Decommissioning Nuclear Power Reactors 10 CFR 50.75(f)(1) WO 18-0004, Response to Request for Additional Information Re License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of ...2018-01-15015 January 2018 Response to Request for Additional Information Re License Amendment Request to Revise Technical Specifications to Transition to Westinghouse Core Design and Safety Analysis Including Adoption of ... WO 17-0093, License Amendment Request (LAR) for Revision to the Emergency Plan2017-12-19019 December 2017 License Amendment Request (LAR) for Revision to the Emergency Plan WO 17-0092, Request for Regulatory Conference (EA-17-149)2017-11-0808 November 2017 Request for Regulatory Conference (EA-17-149) WO 17-0065, Submittal of LER 17-S01-00 for Wolf Creek Nuclear Operating Corp., Regarding Contraband Introduced Into the Protected Area Boundary2017-10-10010 October 2017 Submittal of LER 17-S01-00 for Wolf Creek Nuclear Operating Corp., Regarding Contraband Introduced Into the Protected Area Boundary WO 17-0042, Operating Corporation Supplement to RAI Response Regarding Adopting New EAL Scheme2017-04-26026 April 2017 Operating Corporation Supplement to RAI Response Regarding Adopting New EAL Scheme WO 17-0041, Supplement to Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report2017-04-20020 April 2017 Supplement to Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report WO 17-0033, Response to NRC Regulatory Issue Summary 2017-03, Preparation and Scheduling of Operator Licensing Examinations.2017-04-17017 April 2017 Response to NRC Regulatory Issue Summary 2017-03, Preparation and Scheduling of Operator Licensing Examinations. WO 17-0023, Submittal of Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report2017-03-27027 March 2017 Submittal of Technical Specification 5.6.8 - Post Accident Monitoring (PAM) Report WO 17-0026, Errata for License Amendment Request for Transition to Westinghouse Core Design and Safety Analyses2017-03-22022 March 2017 Errata for License Amendment Request for Transition to Westinghouse Core Design and Safety Analyses WO 17-0013, Response to Request for Additional Information Regarding License Amendment Request for Adopting Revised Emergency Action Level Scheme2017-03-16016 March 2017 Response to Request for Additional Information Regarding License Amendment Request for Adopting Revised Emergency Action Level Scheme WO 17-0009, Revision 30 to Updated Safety Analysis Report2017-03-0909 March 2017 Revision 30 to Updated Safety Analysis Report WO 16-0068, Docket No. 50-482: Request for Regulatory Conference2016-12-21021 December 2016 Docket No. 50-482: Request for Regulatory Conference 2023-05-17
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W6LF CREEK 'NUCLEAR OPERATING CORPORATION June 30, 2011 Russell A. Smith Plant Manager WO 11-0033 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555
Reference:
Letter WO 11-0018, dated April 9, 2011, from R. A. Smith, WCNOC, to USNRC
Subject:
Docket No. 50-482: Cancellation of Licensee Event Report 2011-001-00, "Potential for a CVCS Through-Weld Leak to Affect Reactor Coolant System Inventory After a Loss of Coolant Accident" Gentlemen:
The purpose of this letter is to notify the Nuclear Regulatory Commission (NRC) of the cancellation of Wolf Creek Generating Station (WCGS) Licensee Event Report (LER) 2011-001-00, "Potential for a CVCS Through-Weld Leak to Affect Reactor Coolant System Inventory After a Loss of Coolant Accident." The cancellation of this LER is consistent with the guidance in NUREG-1022, Revision 2, "Event Reporting Guidelines 10 CFR 50.72 and 50.73," Sections 2.8 and 5.1.2.
The Reference reported the potential for a through-weld leak in the Chemical Volume and Control System (CVCS) to affect Reactor Coolant System (RCS) inventory under 10 CFR 50.73(a)(2)(v)(D) as a condition that could have prevented fulfillment of a safety function needed to mitigate the consequences of an accident. This condition was also reported under 10 CFR 50.73(a)(2)(ix)(A) as a single cause that could have prevented fulfillment of the safety functions of trains or channels in different systems.
To ensure that the reactor core would have been protected following a Loss of Coolant Accident (LOCA), Wolf Creek Nuclear Operating Corporation (WCNOC) reviewed current documentation and performed an additional evaluation to determine whether the Emergency Core Cooling System (ECCS) would have been capable of performing its core cooling function with the identified CVCS through-weld leak. This evaluation was documented in the Basic Engineering Disposition (BED) for sub-work order (SWO) 11-336634-006.
The evaluation determined that the uncracked portion of the socket weld had sufficient remaining strength to withstand design loadings for faulted conditions and pressure boundary structural integrity was maintained in the degraded condition. Because the weld would have remained intact through a 12-hour mission time, the integrated leakage over 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> would have been a small fraction (approximately two percent) of the margin on RWST/containment recirculation sump inventory. Therefore, the through-weld leak in the CVCS would not have prevented the ECCS from performing its specified safety function after a LOCA.
P.O. Box 411 / Burlington, KS 66839 / Phone: (620) 364-8831 An Equal Opportunity Employer M/F/HC/VET
WO 11-0033 Page 2 of 3 Calculation AN-95-021, "Determination of the ECCS Flow Rates During the Recirculation Phases," determined that a single Residual Heat Removal (RHR) pump is capable of delivering more than 1,200 gallons-per-minute (gpm) directly to one of the two RCS cold legs when the RCS is depressurized and one of the RHR cross-tie valves (EJ-HV8716A/B) is isolated. For a postulated small break LOCA, the RCS pressures are expected to remain greater than the RHR pump output pressure for a longer period of time than for a large-break LOCA. At the time the Refueling Water Storage Tank (RWST) inventory is depleted and the RHR pump is required to switch to take suction from the containment sump, the RCS pressure may still exceed the RHR pump cut-in pressure of approximately 150 pounds-per-square-inch-gauge (psig).
Under these conditions, the RHR pump would have to be operated in a piggy-back mode with a centrifugal charging pump (CCP) and/or a safety injection pump (SIP) to deliver ECCS flow to the core. However, procedure EMG ES-1 1, "Post LOCA Cooldown and Depressurization,"
directs plant operators to initiate the post-LOCA cooldown and depressurization process in a timely fashion. The BED for SWO 11-336634-006 documented the conclusion from Performance Improvement Request 2002-1967 that, during the recirculation phase of ECCS operations, the RHR pumps are sufficient to maintain the plant in a safe condition after the initial 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> of injection and that the CCPs and SIPs are not required after the RCS is depressurized to the RHR pump cut-in conditions.
With the RCS pressures being decreased to the RHR pump cut-in conditions, a single RHR pump can provide more than 250 gpm flow directly to one of the RCS cold legs as determined in calculation SA-90-003, "Determination of Safety Injection Flowrates for Mode 4 Shutdown LOCA." Thus, operating with a single RHR pump can provide more than sufficient ECCS flow for long-term core cooling 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> after initiation of a small break LOCA event. Based on the above discussion, the 12-hour mission time established for the CCP or SIP is adequate for either a design basis large break LOCA or a small break LOCA.
WCNOC used this 12-hour mission time to determine the potential impact of the CVCS through-weld leak after a small break LOCA. From the rate of 0.02 gpm, the total loss over the 12-hour period is approximately 14.4 gallons. To have a high confidence that the total leakage in 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> is bounded by this evaluation, an estimate of the amount that the leak rate could increase was made. The as-found crack had a length on the outer diameter (OD) surface of the weld of approximately 0.25 inches with an approximate ID length of 1.1 inches. The evaluation assumes that in the 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> following the LOCA the length of the crack at the OD surface will grow in length to match the crack length at the ID surface of approximately 1.1 inches. The increased crack length is also assumed to increase the width of the crack opening thus increasing the leak rate.
Increasing the length of the OD crack to equal the length of the ID crack would increase the crack opening area by approximately a factor of 20 times the initial crack opening area. This evaluation also assumed that flow erosion would increase the flow area by an additional factor of 10. Assuming a linear rate of increase, the average leak rate would be approximately 100 times the initial leak rate. This gives an estimated total leakage from the cracked weld during the 12-hour post LOCA operation of 1,440 gallons.
When the RWST volume level reaches the first low-level indication (LOLO-1), the RHR pumps automatically switch to draw suction from the containment sumps. At this point, the minimum transfer allowance is available in the containment sumps and this volume is used to calculate the Net Positive Suction Head (NPSH) for the RHR pumps. When the RWST volume reaches
WO 11-0033 Page 3 of 3 the second low-level indication (LOLO-2), the containment spray pumps are also manually switched to draw suction from the containment sumps.
The volume of water from the RWST that is transferred to the containment sumps between LOLO-1 and LOLO-2 is at least 72,492 gallons and this amount is not required to maintain NPSH for the RHR pumps during the recirculation phase. At the time of discovering the through-wall leak, there was approximately 16,048 gallons additional volume in the RWST.
Therefore, the 72,492 and the 16,048 (total of 88,540) gallons of inventory represents a margin in the capacity of the RWST and the assumed maximum loss of 1,440 gallons represents a two percent decrease in this margin. The two percent decrease in this margin would not affect the suction capability of the RHR pumps. In addition, assuming this leak rate is continuous (not isolated or repaired) for the 30-day required long term cooling, the excess volume in the recirculation sump inventory would not be exhausted.
Based on this evaluation, WCNOC determined that this condition does not meet the criteria for reporting under 10 CFR 50.73 and LER 2011-001-00 is being cancelled. This letter contains no commitments. If you have any questions concerning this matter, please contact me at (620) 364-4156, or Mr. Gautam Sen at (620) 364-4175.
Sincerely Russell A. Smith RAS/rlt cc: E. E. Collins (NRC)
J. R. Hall (NRC)
G. B. Miller (NRC)
Senior Resident Inspector (NRC)