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Category:Letter type:RS
MONTHYEARRS-23-121, Sixth Ten-Year Interval Inservice Testing Program2023-11-30030 November 2023 Sixth Ten-Year Interval Inservice Testing Program RS-23-119, Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information2023-11-10010 November 2023 Supplemental Information Letter for Part 73 Exemption Request - Responses to Request for Confirmatory Information RS-23-107, Relief Request I5R-22, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval2023-11-0808 November 2023 Relief Request I5R-22, Inservice Inspection Program Relief Request Regarding Examination Coverage for the Fifth Inservice Inspection Interval RS-23-102, Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation2023-10-16016 October 2023 Request for Exemption from Enhanced Weapons, Firearms Background Checks, and Security Event Notifications Implementation RS-23-097, Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans2023-10-12012 October 2023 Constellation Energy Generation, LLC, Advisement of Leadership Changes and Submittal of Updated Standard Practice Procedures Plans RS-23-071, Application to Adopt TSTF-564, Safety Limit MCPR2023-08-30030 August 2023 Application to Adopt TSTF-564, Safety Limit MCPR RS-23-080, Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs2023-08-30030 August 2023 Constellation Energy Generation, LLC, Application to Revise Technical Specifications to Adopt TSTF-264-A, Revision 0, 3.3.9 and 3.3.10 - Delete Flux Monitors Specific Overlap Requirement SRs RS-23-077, Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations2023-06-16016 June 2023 Response to NRC Regulatory Issue Summary 2023-01, Preparation and Scheduling of Operator Licensing Examinations RS-23-078, Supplement to License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times2023-06-16016 June 2023 Supplement to License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times RS-23-042, Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling2023-05-25025 May 2023 Application to Revise Technical Specifications to Adopt TSTF-580, Provide Exception from Entering Mode 4 with No Operable RHR Shutdown Cooling RS-23-070, Supplement to License Amendment Request Regarding Transition to GNF3 Fuel2023-05-16016 May 2023 Supplement to License Amendment Request Regarding Transition to GNF3 Fuel RS-23-057, Supplement to License Amendment Request Regarding Transition to GNF3 Fuel2023-04-17017 April 2023 Supplement to License Amendment Request Regarding Transition to GNF3 Fuel RS-23-049, Constellation Energy Generation, LLC, Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations2023-03-23023 March 2023 Constellation Energy Generation, LLC, Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations RS-23-041, Response to Request for Additional Information for Alternative Request RV-23H2023-03-14014 March 2023 Response to Request for Additional Information for Alternative Request RV-23H RS-23-045, Constellation Energy Generation, LLC Submittal of Fitness for Duty Performance Data Reports for 2022 Per 10 CFR 26.717(c) & 10 CFR 26.2032023-02-28028 February 2023 Constellation Energy Generation, LLC Submittal of Fitness for Duty Performance Data Reports for 2022 Per 10 CFR 26.717(c) & 10 CFR 26.203 RS-23-003, Constellation Energy Generation, LLC, Summary of Changes to Quality Assurance Topical Report, NO-AA-10, and Decommissioning Quality Assurance Program, NO-DC-102023-01-31031 January 2023 Constellation Energy Generation, LLC, Summary of Changes to Quality Assurance Topical Report, NO-AA-10, and Decommissioning Quality Assurance Program, NO-DC-10 RS-23-004, Response to Request for Additional Information Regarding Transition to GNF3 Fuel License Amendment Request2023-01-23023 January 2023 Response to Request for Additional Information Regarding Transition to GNF3 Fuel License Amendment Request RS-22-126, Constellation Energy Generation, LLC - Request to Use Provisions of a Later Edition of the ASME Boiler and Pressure Vessel Code, Section XI2022-11-30030 November 2022 Constellation Energy Generation, LLC - Request to Use Provisions of a Later Edition of the ASME Boiler and Pressure Vessel Code, Section XI RS-22-121, Notice of Intent to Pursue Subsequent License Renewal Applications2022-11-0909 November 2022 Notice of Intent to Pursue Subsequent License Renewal Applications RS-22-117, Response to Request for Additional Information License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies2022-11-0303 November 2022 Response to Request for Additional Information License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies RS-22-116, Submittal of Relief Requests Associated with the Sixth Inservice Testing Interval2022-11-0101 November 2022 Submittal of Relief Requests Associated with the Sixth Inservice Testing Interval RS-22-115, Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors2022-10-19019 October 2022 Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors RS-22-092, Nine and Quad Cities - Application to Revise Primary Containment Isolation Instrumentation Technical Specifications in Accordance with TSTF-306, Revision 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration2022-10-0303 October 2022 Nine and Quad Cities - Application to Revise Primary Containment Isolation Instrumentation Technical Specifications in Accordance with TSTF-306, Revision 2, Add Action to LCO 3.3.6.1 to Give Option to Isolate the Penetration RS-22-066, License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times2022-08-25025 August 2022 License Amendment Request to Revise Technical Specification 3.1.4, Control Rod Scram Times RS-22-065, License Amendment Request Regarding Transition to GNF3 Fuel2022-08-18018 August 2022 License Amendment Request Regarding Transition to GNF3 Fuel RS-22-093, Advisement of Leadership Changes for Constellation Energy Generation, LLC and Submittal of Updated Standard Practice Procedures Plans2022-08-18018 August 2022 Advisement of Leadership Changes for Constellation Energy Generation, LLC and Submittal of Updated Standard Practice Procedures Plans RS-22-101, Response to Request for Additional Information Related to Relief Request I6R-01 Associated with the Sixth Inservice Inspection Interval2022-08-10010 August 2022 Response to Request for Additional Information Related to Relief Request I6R-01 Associated with the Sixth Inservice Inspection Interval RS-22-099, Submittal of Upcoming Sixth Inservice Inspection Interval Relief Requests I6R-09 and I6R-102022-07-19019 July 2022 Submittal of Upcoming Sixth Inservice Inspection Interval Relief Requests I6R-09 and I6R-10 RS-22-082, Defueled Safety Analysis Report Update, Revision 112022-06-22022 June 2022 Defueled Safety Analysis Report Update, Revision 11 RS-22-080, Withdrawal and Proposed Alternative I6R-08 Associated with Code Case N-921 for Sixth Inservice Inspection Intervals2022-06-0909 June 2022 Withdrawal and Proposed Alternative I6R-08 Associated with Code Case N-921 for Sixth Inservice Inspection Intervals RS-22-064, License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies with Proposed Change to Technical Specifications Section 4.3.12022-06-0808 June 2022 License Amendment Request Regarding New Fuel Storage Vault and Spent Fuel Storage Pool Criticality Methodologies with Proposed Change to Technical Specifications Section 4.3.1 RS-22-051, Constellation Energy Generation, LLC - Update to Correspondence Addressees and Service Lists2022-04-12012 April 2022 Constellation Energy Generation, LLC - Update to Correspondence Addressees and Service Lists RS-22-049, Constellation Energy Generation, LLC, Supplemental Information to Correct Typographical Errors in Constellation'S Application to Revise Technical Specifications to Adopt TSTF-541 Revision 2, Add Exceptions to Surveillance Requirements for2022-04-0404 April 2022 Constellation Energy Generation, LLC, Supplemental Information to Correct Typographical Errors in Constellation'S Application to Revise Technical Specifications to Adopt TSTF-541 Revision 2, Add Exceptions to Surveillance Requirements for V RS-22-046, Relief Requests Associated with the Sixth Inservice Inspection Interval2022-03-25025 March 2022 Relief Requests Associated with the Sixth Inservice Inspection Interval RS-22-045, Constellation Energy Generation, LLC, Response to NRC Regulatory Issue Summary 2022-01, Preparation and Scheduling of Operator Licensing Examinations2022-03-25025 March 2022 Constellation Energy Generation, LLC, Response to NRC Regulatory Issue Summary 2022-01, Preparation and Scheduling of Operator Licensing Examinations RS-22-042, Report on Status of Decommissioning Funding for Shutdown Reactors2022-03-23023 March 2022 Report on Status of Decommissioning Funding for Shutdown Reactors RS-22-027, Constellation, Response to Request for Additional Information Regarding Application to Revise Technical Specifications to Adopt TSTF-541 Revision 2, Add Exceptions to Surveillance Requirements for Valves and Dampers Locked in the Actuated2022-02-23023 February 2022 Constellation, Response to Request for Additional Information Regarding Application to Revise Technical Specifications to Adopt TSTF-541 Revision 2, Add Exceptions to Surveillance Requirements for Valves and Dampers Locked in the Actuated P RS-22-023, Constellation Energy Generation, LLC, Executed Trust Fund Agreement Amendment and Subordinate Trust Agreement2022-02-23023 February 2022 Constellation Energy Generation, LLC, Executed Trust Fund Agreement Amendment and Subordinate Trust Agreement RS-22-019, Constellation Energy Generation, LLC - Update to Correspondence Addressees and Service Lists2022-02-16016 February 2022 Constellation Energy Generation, LLC - Update to Correspondence Addressees and Service Lists RS-22-015, Notification of Completion of License Transfer and Request to Continue Processing Pending NRC Actions Previously Requested by Exelon Generation Company, LLC2022-02-0101 February 2022 Notification of Completion of License Transfer and Request to Continue Processing Pending NRC Actions Previously Requested by Exelon Generation Company, LLC RS-21-009, Proposed Relief Request Associated with Code Case N-9212022-01-18018 January 2022 Proposed Relief Request Associated with Code Case N-921 RS-22-004, Supplement to Application to Adopt TSTF-554, Revision 1, Revise Reactor Coolant Leakage Requirements2022-01-0404 January 2022 Supplement to Application to Adopt TSTF-554, Revision 1, Revise Reactor Coolant Leakage Requirements RS-21-121, Proposed Changes to Decommissioning Trust Agreements and Master Terms2021-12-15015 December 2021 Proposed Changes to Decommissioning Trust Agreements and Master Terms RS-21-114, Request for Exemption from 10 CFR 2.109(b)2021-10-28028 October 2021 Request for Exemption from 10 CFR 2.109(b) RS-21-110, Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors2021-10-19019 October 2021 Annual Report of Emergency Core Cooling System Evaluation Model Changes and Errors RS-21-103, Updated Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations for Byron Station and Dresden Nuclear Power Station2021-09-28028 September 2021 Updated Report on Status of Decommissioning Funding for Reactors and Independent Spent Fuel Storage Installations for Byron Station and Dresden Nuclear Power Station RS-21-097, Withdrawal of Certification of Permanent Cessation of Power Operations for Dresden Nuclear Power Station, Units 2 and 3, and Previously Submitted Licensing Actions in Support of Decommissioning2021-09-15015 September 2021 Withdrawal of Certification of Permanent Cessation of Power Operations for Dresden Nuclear Power Station, Units 2 and 3, and Previously Submitted Licensing Actions in Support of Decommissioning RS-21-091, Implementation of Insider Threat Program Requirements Associated with the Voluntary Security Clearance Program and Advisement of Leadership Changes2021-09-13013 September 2021 Implementation of Insider Threat Program Requirements Associated with the Voluntary Security Clearance Program and Advisement of Leadership Changes RS-21-086, Supplement to Request for Exemptions from Portions of 10 CFR 50.47 and 10 CFR 50, Appendix E2021-08-23023 August 2021 Supplement to Request for Exemptions from Portions of 10 CFR 50.47 and 10 CFR 50, Appendix E RS-21-078, Response to Request for Additional Information for Application to Revise Technical Specification to Adopt TSTF-582, Reactor Pressure Vessel Water Inventory Control (RPV WIC) Enhancements, and TSTF-583-T, TSTF-582 Diesel2021-08-19019 August 2021 Response to Request for Additional Information for Application to Revise Technical Specification to Adopt TSTF-582, Reactor Pressure Vessel Water Inventory Control (RPV WIC) Enhancements, and TSTF-583-T, TSTF-582 Diesel 2023-08-30
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ExeI en S.
Exelon Generation www.exeloncorp.com NEuclea 4300 Winfield Road Warrenville, IL 60555 RS-04-166 October 29, 2004 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Facility Operating License Nos. DPR-1 9 and DPR-25 NRC Docket Nos. 50-237 and 50-249
Subject:
Main SteaM Safety Valve Setpoint Tolerances and Tolerance Uncertainty Treatmenf Methodology
References:
- 1. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S. NRC, "Request for Technical Specifications Changes Related to Main Steam Safety Valve Operability Requirements," dated October 10, 2002
- 2. Letter from M. Banerjee CU. S. NRC) to C. M. Crane (Exelon Generation Company, LLC), "Dresden Nuclear Power Station, Units 2 and 3 - Issuance of Amendments for Main Steam Safety Valve Technical Specifications (TAC Nos. MB6537 and MB6538)," dated July 30, 2004
- 3. Letter from P. R. Simpson (Exelon Generation Company, LLC) to U. S. NRC, "Additional Information Regarding Request for Technical Specifications Changes Related to Main Steam Safety Valve Operability Requirements,"
dated July 8, 2004 In Reference 1, Exelon Generation Company, LLC (EGC) requested changes to the Technical Specifications (TS) of Facility Operating License Nos. DPR-1 9 and DPR-25 for Dresden Nuclear Power Station (DNPS), Units 2 and 3. The proposed changes increased the number of main steam safety valves (MSSVs) required to be operable from eight to nine. The NRC approved the proposed changes in Reference 2.
As described in Reference 2, DNPS operating experience indicates that the as-found lift setpoints of the MSSVs and Target Rock safety/relief valves (S/RVs) have deviated from the TS tolerance limit of plus or minus one percent multiple times. As such, the NRC's approval of the proposed changes included additional conditions that were added to the license to affect resolution of the issue of valve lift setpoint drift beyond the TS tolerance value. One of the additional conditions stated "Exelon shall submit, for NRC approval, values for the safety valve and safety/relief valve setpoint tolerances and the tolerance uncertainty treatment methodology
October 29, 2004 U. S. Nuclear Regulatory Commission Page 2 applied to the main steam safety valve and safety/relief valve setpoint test data by October 29, 2004." This letter provides the requested information.
Generally, safety valve drift is considered as a fixed percentage of the setpoint. In application in safety analysis codes, this drift allowance is generally used additively and uniformly to a valve or group of valves with the same setpoint. With groups of valves, assuming all of them drift to the highest possible setpoint is a very conservative approach.
However, to support approval of the Reference 1 amendment request, EGC used this approach in an American Society of Mechanical Engineers (ASME) overpressure analysis, and the results were submitted to the NRC in Reference 3. The ASME overpressure analysis was performed using valve setpoint tolerances that were determined using a 95/95 statistical analysis as described in NUREG-1475, "Applying Statistics." Using the 95/95 methodology, EGC determined that the setpoint tolerances based on actual valve performance were 2.2 percent for the MSSVs and 4.1 percent for the S/RVs. As stated above, assuming all of the valves drift to the highest possible setpoint is a very conservative approach.
EGC has performed a Monte Carlo statistical analysis of the MSSV networks to determine an upper tolerance limit that more accurately predicts the distribution of pressures that result in the valves opening. The intent of the analysis was to demonstrate a statistically based technically valid alternative to traditional deterministically applied setpoint drift, which assumes that all of the valves drift to the highest possible setpoint. The one-time Monte Carlo statistical analysis was performed using actual as-found MSSV and S/RV test data. The Monte Carlo analysis of the valve network shows that valve opening for a group of valves with the same setpoint will display a distribution, with some valves opening at lower pressures and some opening at higher pressures. The characterization of valve opening was selected such that the distribution bounds 95 percent of the actual as-found MSSV and S/RV test data to ensure that the result is conservative and bounds the majority of the data.
The results of the Monte Carlo analysis conclude that the actual MSSV setpoint drift data does not support the current TS upper tolerance limit of one percent on all valves. This conclusion is largely driven by the penalty associated with performing a statistical analysis on a small population of data points (i.e., each DNPS unit has only one S/RV that is tested once per cycle).
However, the use of Monte Carlo based valve network response suggests that the anticipated valve network performance, based on 95 percentile criteria, is very close to the deterministic case with all valves drifted one percent high. Specifically, the analysis shows that the amount of main steam pressure/flow relieved through the valve network modeled for the Monte Carlo analysis (i.e., using actual MSSV and S/RV as-found test data) exceeds the amount of main steam pressure/flow relieved when an upper tolerance of 1.5 percent is applied to all valves.
Although the analysis does not support the current TS upper tolerance limit of one percent on all valves, the anticipated transient without scram peak pressure and ASME overpressure analyses have been performed assuming upper tolerances greater than 1.5 percent for each DNPS unit.
EGC is currently evaluating potential design modifications that would increase the MSSV and S/RV relief capacity in order to regain margin that was lost as a result of implementing extended power uprate and more efficient reactor core designs. The MSSV and S/RV setpoint tolerances are also being evaluated in conjunction with the potential design modifications. Therefore, the setpoint tolerance selected for the planned TS amendment request may not be 1.5 percent.
October 29, 2004 U. S. Nuclear Regulatory Commission Page 3 However, in light of EGC's evaluations to date that are based on actual as-found test data, the upper limit setpoint tolerance requested in the future TS amendment request will be greater than or equal to 1.5 percent.
The license amendment request and supporting analyses will be performed in accordance with General Electric Nuclear Energy licensing topical report NEDC-31753P, "BWROG In-Service Pressure Relief Technical Specification Revision Licensing Topical Report," to support the future TS amendment request. This licensing topical report was previously reviewed and approved by the NRC as documented in a safety evaluation dated March 8, 1993, and provided the basis for NRC approval of TS amendments for several other boiling water reactors.
Should you have any questions concerning this letter, please contact Mr. Kenneth M. Nicely, at (630) 657-2803.
R spectfully, Patrick R. Simpson Manager - Licensing
Attachment:
Calculation MWMECH-04-004, "Monte Carlo Analysis of Dr 2&3-and QC 1&2 MSSV Network Using Pooled Data and Design Methodology Approach,"
Revision 0 cc: Regional Administrator - NRC Region IlIl NRC Senior Resident Inspector- Dresden Nuclear Power Station