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MONTHYEARML1109006702011-03-30030 March 2011 Relief Request RR-04-11 Implementation of a Risk-Informed Inservice Inspection Program Based on ASME Code Case N-716 Project stage: Request ML1115401192011-06-0303 June 2011 RAI for Millstone 2 RR-04-11 Project stage: RAI ML1115908902011-06-14014 June 2011 Request for Additional Information Regarding Relief Request for Implementation of a Risk-Informed Inservice Inspection Program Project stage: RAI ML11179A0252011-06-23023 June 2011 Request for Additional Information Regarding Relief Request RR-04-11, Implementation of a Risk-Informed Inservice Inspection Program Based on ASME Code Case N-716 for the Fourth 10-Year Inspection Interval Project stage: Request ML12020A2432012-01-12012 January 2012 Supplement to Relief Request RR-04-11, Implementation of a Risk-Informed Inservice Inspection Program Based on ASME Code Case N-716 Project stage: Supplement ML1208004332012-03-27027 March 2012 Issuance of Relief Request RR-04-11 Regarding Risk-Informed Inservice Inspection Program Project stage: Approval 2011-06-23
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Category:Letter
MONTHYEARIR 05000336/20240022024-08-13013 August 2024 Integrated Inspection Report 05000336/2024002 and 05000423/2024002 IR 05000336/20244412024-08-0606 August 2024 Supplemental Inspection Report 05000336/2024441 and 05000423/2024441 and Follow-Up Assessment Letter (Cover Letter Only) ML24212A0742024-08-0505 August 2024 Request for Withholding Information from Public Disclosure - Millstone Power Station, Unit No. 3, Proposed Alternative Request IR-4-13 to Support Steam Generator Channel Head Drain Modification ML24211A1712024-07-25025 July 2024 Associated Independent Spent Fuels Storage Installation, Revision to Emergency Plan - Report of Change IR 05000336/20244032024-07-22022 July 2024 Information Request for the Cybersecurity Baseline Inspection, Notification to Perform Inspection 05000336/2024403 and 05000423/2024403 IR 05000336/20245012024-07-0101 July 2024 Emergency Preparedness Biennial Exercise Inspection Report 05000336/2024501 and 05000423/2024501 ML24180A0932024-06-28028 June 2024 Readiness for Additional Inspection: EA-23-144 IR 05000336/20240102024-06-26026 June 2024 Biennial Problem Identification and Resolution Inspection Report 05000336/2024010 and 05000423/2024010 ML24178A2422024-06-25025 June 2024 2023 Annual Report of Emergency Core Cooling System (ECCS) Model, Changes Pursuant to the Requirements of 10 CFR 50.46 ML24177A2792024-06-20020 June 2024 Preparation and Scheduling of Operator Licensing Examinations ML24170B0532024-06-10010 June 2024 DOM-NAF-2-P/NP-A, Revision 0.5, Reactor Core Thermal-Hydraulics Using the VIPRE-D Computer Code ML24165A1292024-06-0505 June 2024 ISFSI, 10 CFR 50.59 Annual Change Report for 2023 Annual Regulatory Commitment Change Report for 2023 ML24128A2772024-06-0404 June 2024 Issuance of Amendment No. 290 to Revise TSs for Reactor Core Safety Limits, Fuel Assemblies, and Core Operating Limits Report for Use of Framatome Gaia Fuel (EPID L-2023-LLA-0074) (Non-Proprietary) ML24151A6482024-06-0303 June 2024 Changes in Reactor Decommissioning Branch Project Management Assignments for Some Decommissioning Facilities ML24109A0032024-05-21021 May 2024 Issuance of Amendment No. 289 to Revise Technical Specifications to Use Framatome Loss of Coolant Accident Evaluation Methodologies for Establishing Core Operating Limit (EPID L-2023-LLA-0065) (Non-Proprietary) ML24110A0562024-05-21021 May 2024 Exemption from the Requirements of 10 CFR Part 50, Section 50.46, and Appendix K Regarding Use of M5 Cladding Material (EPID L-2023-LLE-0013) (Letter) ML24141A2432024-05-20020 May 2024 Response to Request for Additional Information Regarding Alloy 600 Aging Management Program Submittal Related to License Renewal Commitment No. 15 ML24142A0952024-05-20020 May 2024 End of Cycle 22 Steam Generator Tube Inspection Report IR 05000336/20240012024-05-14014 May 2024 Integrated Inspection Report 05000336/2024001 and 05000423/2024001 and Apparent Violation ML24123A2042024-05-0202 May 2024 Pre-Decisional Replay to EA-23-144 ML24123A1222024-04-30030 April 2024 Inservice Inspection Program - Owners Activity Report, Refueling Outage 22 IR 05000336/20244012024-04-30030 April 2024 Security Baseline Inspection Report 05000336/2024401 and 05000423/2024401 (Cover Letter Only) IR 05000336/20244402024-04-25025 April 2024 Special Inspection Follow-Up Report 05000336/2024440 and 05000423/2024440 and Preliminary Finding(S) of Greater than Very Low Significance and NRC Investigation Report No. 1-2024-001 (Cover Letter Only) ML24116A1742024-04-24024 April 2024 Annual Radiological Environmental Operating Report ML24114A2662024-04-24024 April 2024 Submittal of 2023 Annual Radioactive Effluent Release Report IR 05000336/20234022024-01-30030 January 2024 Security Baseline Inspection Report 05000336/2023402 and 05000423/2023402 (Cover Letter Only) ML24030A7522024-01-30030 January 2024 Technical Specification Bases Pages ML23341A0172024-01-12012 January 2024 Issuance of Amendment No. 288 Revision to Applicability Term for Reactor Coolant System Heatup and Cooldown Pressure-Temperature Limitations Figures IR 05000336/20234402024-01-11011 January 2024 Special Inspection Report 05000336/2023440 and 05000423/2023440 (Cover Letter Only) ML24004A1052024-01-0404 January 2024 Request for Information for a Biennial Problem Identification and Resolution Inspection; Inspection Report 05000336/2024010 & 05000423/2024010 ML23361A0942023-12-21021 December 2023 Response to Request for Additional Information Regarding Proposed License Amendment Request to Revise Technical Specifications for Reactor Core Safety Limits, Fuel Assemblies and Core Operating Limits Report . ML23361A0312023-12-20020 December 2023 Intent to Pursue Subsequent License Renewal ML23283A3052023-12-20020 December 2023 Review of Appendix F to DOM-NAF2, Qualification of the Framatome ORFEO-GAIA and ORFEO-NMGRID CHF Correlations in the Dominion Energy VIPRE-D Computer Code (EPID L-2022-LLT-0003) (Nonproprietary) ML23352A0202023-12-18018 December 2023 Senior Reactor and Reactor Operator Initial License Examinations ML23334A2242023-11-30030 November 2023 Request for Exemption from Enhanced Weapons Firearms Background Checks, and Security Event Notifications Implementation ML23324A4222023-11-20020 November 2023 Reactor Vessel Internals Inspections Aging Management Program Submittal Related to License Renewal Commitment 13 ML23324A4302023-11-20020 November 2023 Alloy 600 Aging Management Program Submittal Related to License Renewal Commitment 15 ML23317A2702023-11-13013 November 2023 Core Operating Limits Report, Cycle 23 IR 05000336/20230032023-11-0606 November 2023 Integrated Inspection Report 05000336/2023003 and 05000423/2023003 ML23298A1652023-10-26026 October 2023 Requalification Program Inspection IR 05000336/20234202023-10-0404 October 2023 Security Inspection Report 05000336/2023420 and 05000423/2023420 ML23230A0502023-10-0202 October 2023 5 of the Quality Assurance Topical Report - Review of Program Changes ML23226A0052023-09-26026 September 2023 Issuance of Amendment No. 287 Supplement to Spent Fuel Pool Criticality Safety Analysis IR 05000245/20230012023-09-19019 September 2023 Safstor Inspection Report 05000245/2023001 IR 05000336/20230102023-09-0808 September 2023 Commercial Grade Dedication Report 05000336/2023010 and 05000423/2023010 IR 05000336/20230052023-08-31031 August 2023 Updated Inspection Plan for Millstone Power Station, Units 2 and 3 (Report 05000336/2023005 and 05000423/2023005) ML23248A2132023-08-30030 August 2023 Response to Request for Additional Information Regarding Proposed License Amendment Request to Revise the Applicability Term for Reactor Coolant System Heatup and Cooldown Pressure-Temperature. 2024-08-06
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Dominion Nuclear Connecticut, Inc.
5000 Dominion Boulevard, Glen Allen, Virginia 23060 ,ikominioniif Web Address: www.dom.com January 12, 2012 U.S. Nuclear Regulatory Commission Serial No. 11-109A Attention: Document Control Desk NLOSNVDC RO Washington, DC 20555 Docket No. 50-336 License No. DPR-65 DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION UNIT 2 SUPPLEMENT TO RELIEF REQUEST RR-04-1 1, IMPLEMENTATION OF A RISK-INFORMED INSERVICE INSPECTION PROGRAM BASED ON ASME CODE CASE N-716 By letter dated March 30, 2011, Dominion Nuclear Connecticut, Inc. (DNC) requested authorization to implement a Millstone Power Station Unit 2 (MPS2) risk-informed inservice inspection (RI-ISI) program based on the American Society of Mechanical Engineers Code Case N-716. Following this submittal, additional fire protection piping was identified that had previously screened out of the MPS2 probabilistic risk assessment (PRA) model. This piping, which is part of the fire suppression system in the MPS2 auxiliary building cable vault, may contribute sufficient risk to be considered high safety significant and will be conservatively included in the MPS2 RI-ISI program until a flow rate analysis and PRA model update are performed.
The information provided in this letter does not affect the conclusions of the significant hazards consideration presented in the March 30, 2011 DNC letter.
If you have any questions regarding this supplement, please contact Wanda Craft at (804) 273-4687.
Sincerely, J. .P e Viq esident - Nuclear Engineering
Attachment:
Supplemental Information for Proposed Relief Request RR-04-1 1, Implementation of a Risk-Informed Inservice Inspection Program Based on ASME Code Case N-716
Serial No. 11-109A Docket Nos. 50-336 Relief Request RR-04-11 Page 2 of 2 Commitments made in this letter:
- 1. None cc: U.S. Nuclear Regulatory Commission Region I 475 Allendale Road King of Prussia, PA 19406-1415 C. J. Sanders Project Manager - Millstone Power Station U.S. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Mail Stop 08-B3 Rockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station
Serial No. 11-109A ATTACHMENT SUPPLEMENTAL INFORMATION FOR PROPOSED RELIEF REQUEST RR-04-11, IMPLEMENTATION OF A RISK-INFORMED INSERVICE INSPECTION PROGRAM BASED ON ASME CODE CASE N-716 DOMINION NUCLEAR CONNECTICUT, INC.
MILLSTONE POWER STATION UNIT 2
Serial No. 11-109A Attachment, Page 1 of 2 SUPPLEMENTAL INFORMATION FOR PROPOSED RELIEF REQUEST RR-04-1t, IMPLEMENTATION OF A RISK-INFORMED INSERVICE INSPECTION PROGRAM BASED ON ASME CODE CASE N-716 By letter dated March 30, 2011, Dominion Nuclear Connecticut, Inc. (DNC) requested authorization to implement a Millstone Power Station Unit 2 (MPS2) risk-informed inservice inspection (RI-ISI) program based on the American Society of Mechanical Engineers (ASME) Code Case N-716. Following this submittal, additional fire protection piping was identified that had previously screened out of the MPS2 probabilistic risk assessment (PRA) model. This piping, which is part of the fire suppression system in the MPS2 auxiliary building cable vault, may contribute sufficient risk to be considered high safety significant (HSS) and will be conservatively included in the MPS2 RI-ISI program until a flow rate analysis and PRA model update are performed.
The cable vault fire suppression system consists of two headers, one 4" header and one 6" header that feed a series of 3", 2.5", 2" and 1"lines which terminate at sprinkler nozzle heads designed to suppress a cable tray fire. The cable vault has ventilation ducts in the floor which lead to the battery rooms below. In the MPS2 PRA model, if a flood occurred in the cable vault and water flowed into the ventilation ducts, it could eventually fail both direct current (DC) buses and result in core damage. The cable vault has flooding mitigation features designed to preclude these consequences.
These features include a floor drain system, berms around the ventilation ducts, and a gap under a door through which water can flow out of the room. However, if a pipe break of sufficient size occurred, these features may not allow sufficient time to mitigate the flood.
Postulated failure of the 6" and 4" headers, or the 3" fire protection piping require detailed analysis to assess the pipe failure frequencies and the capacity of the cable vault flooding mitigation systems. As a conservative measure, until the flowrate analysis is completed and the PRA model is updated, the identified fire protection piping will be treated as HSS. Additional inspections determined by the guidelines of Code Case N-716 will be added to the RI-ISI schedule and will be performed within the ten year interval. Following completion of the flow rate analysis and PRA model update, the cable vault fire protection piping confirmed as HSS will be incorporated into the RI-ISI program as part of the normal update process. The periodic update process for the RI-ISI program is documented in-house and available for review by the NRC.
To ensure that the MPS2 internal flooding PRA model has captured the flood scenarios which could contribute significantly to core damage frequency (CDF) and large early release frequency (LERF) and impact the scope of the RI-ISI program, an independent review was performed of the plant areas that, if flooded, would result in a HSS flood scenario. A walkdown of these areas was performed to identify the flooding sources, propagation paths, and flood mitigation features. The internal flooding model was then reviewed to verify these flooding scenarios were included.
Serial No. 11-109A Attachment, Page 2 of 2 In addition to the fire protection piping in the cable vault, one additional pipe segment was identified that was not included in the internal flooding model used in development of the proposed RI-ISI Program. This fire protection piping segment is located in the turbine building cable vault. A flooding event resulting from a failure of this piping segment would not contribute significantly-to CDF or LERF because there would be adequate time for operators to mitigate the flood from this source.