RS-24-053, Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, Provide Risk-Informed
| ML24158A301 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 06/06/2024 |
| From: | Humphrey M Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| RS-24-053 | |
| Download: ML24158A301 (1) | |
Text
4300 Winfield Road Warrenville, IL 60555 630 657 2000 Office 10 CFR 50.90 RS-24-053 June 6, 2024 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Quad Cities Nuclear Power Station, Units 1 and 2 Renewed Facility Operating License Nos. DPR-29 and DPR-30 NRC Docket Nos. 50-254 and 50-265
Subject:
Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b"
References:
- 1. Letter from P. R. Simpson (Constellation Energy Generation LLC) to U.S.
NRC, "License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b,'" dated June 8, 2023 (ADAMS Accession No. ML23159A249)
- 2. Email from R. Kuntz (U.S. NRC) to K. Nicely (Constellation Energy Generation, LLC), "Request for Additional Information RE: Quad Cities TSTF-505 amendment," dated May 13, 2024 (ADAMS Accession No. ML24135A018)
In Reference 1, Constellation Energy Generation, LLC (CEG) requested an amendment to Renewed Facility Operating License Nos. DPR-29 and DPR-30 for Quad Cities Nuclear Power Station (QCNPS) Units 1 and 2. The proposed amendment would modify the Technical Specifications requirements to permit the use of Risk Informed Completion Times in accordance with TSTF-505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b."
The NRC requested additional information that is needed to support review of the proposed amendment in Reference 2. In response to this request, CEG is providing the attached information.
CEG has reviewed the information supporting the finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the NRC in Reference 1.
The additional information provided in this submittal does not affect the bases for concluding that the proposed license amendment does not involve a significant hazards consideration. In
June 6, 2024 U.S. Nuclear Regulatory Commission Page 2 addition, the information provided in this submittal does not affect the bases for concluding that neither an environmental impact statement nor an environmental assessment needs to be prepared in connection with the proposed amendment.
CEG is notifying the State of Illinois of this supplement to a previous application for a change to the operating license by sending a copy of this letter and its attachments to the designated State Official in accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"
paragraph (b).
There are no regulatory commitments contained in this letter. Should you have any questions concerning this letter, please contact Mr. Ken Nicely at (779) 231-6119.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 6th day of June 2024.
Respectfully, Mark Humphrey Sr. Manager Licensing Constellation Energy Generation, LLC
Attachment:
Response to APLA Request for Additional Information cc:
Regional Administrator - NRC Region III NRC Senior Resident Inspector - QCNPS NRC Project Manager, NRR - QCNPS Illinois Emergency Management Agency - Division of Nuclear Safety
- Humphrey, Mark D.
Digitally signed by Humphrey, Mark D.
Date: 2024.06.06 06:40:41
-05'00'
ATTACHMENT Quad Cities Nuclear Power Station Docket Nos. 50-254 and 50-265 Facility Operating License Nos. DPR-29 and DPR-30 Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF 505, Revision 2, "Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b" Response to APLA Request for Additional Information
QCNPS Request to Adopt TSTF-505 Attachment Response to APLA Request for Additional Information Page 1 of 3 Docket Nos. 50-254 and 50-265 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATIONS TO ADOPT TSTF-505, REVISION 2 CONSTELLATION ENERGY GENERATION, LLC QUAD CITIES NUCLEAR POWER STATION, UNITS 1 AND 2 DOCKET NOS. 50-254 AND 50-265 APLA RAI 02.01 - Sources of PRA Model Uncertainty RG 1.200, Revision 3, "Acceptability of Probabilistic Risk Assessment [PRA] Results for Risk-Informed Activities" (ML090410014) states in part "NRC [Nuclear Regulatory Commission]
reviewers, [will] focus their review on key assumptions and areas identified by peer reviewers as being of concern and relevant to the application." The NRC Staff evaluates the acceptability of the PRA for each new risk-informed application and as discussed in RG 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk Informed Decisions on Plant Specific Changes to the Licensing Basis," (ML100910006) which recognizes that the acceptable technical adequacy of risk analyses necessary to support regulatory decision-making may vary with the relative weight given to the risk assessment element of the decision-making process. The NRC staff notes that the calculated results of the PRA are used directly to calculate a risk informed completion time (RICT) which subsequently determines how long systems, structures, and components (SSCs) (both individual SSCs and multiple, unrelated SSCs) controlled by technical specifications can remain inoperable. Therefore, the PRA results are given a very high weight in a Technical Specification (TS) Task Force (TSTF) Traveler, TSTF-505 Revision 2, "Provide Risk-Informed Extended Completion Times, RITSTF [Risk-Informed Technical Specification Task Force] Initiative 4b" (ML18183A493) application. This is consistent with the guidance in Section 2.3.4 of Nuclear Energy Institute (NEI) 06-09-A, "Risk-Informed Technical Specifications Initiative 4b Risk-Managed Technical Specifications (RMTS) Guidelines," Revision 0-A (ML12286A322) that sensitivity studies should be performed on the base model prior to initial implementation of the RICT program on uncertainties that could potentially impact the results of RICT calculations and that sensitivity studies should be used to develop appropriate compensatory management actions (RMAs).
The response to APLA RAI 02.b provided by letter dated March 19, 2024 (ML24079A122) states an updated sensitivity study that increased the large drywell containment failure causes loss of injection by a factor of two on selected RICT cases. The RAI response states that based on the sensitivity results, the RICT calculations are insensitive to this source of uncertainty and that no additional risk RMAs are required. However, the NRC staff notes that the sensitivity study for TS 3.5.1.B, one low pressure coolant injection (LPCI) or one core spray (CS) subsystem inoperable, results in a 31.7 percent decrease in the RICT estimated allowed outage time. It is unclear to the NRC staff whether the conclusion of the sensitivity study is consistent with the guidance of Section 2.3.4 of NEI 06-09. Considering this, provide the following:
QCNPS Request to Adopt TSTF-505 Attachment Response to APLA Request for Additional Information Page 2 of 3 Docket Nos. 50-254 and 50-265 a) Provide an explanation of the conservatisms, if any, in the Quad Cities PRA model that justifies that the conclusion of the impact of this source of uncertainty on TS 3.5.1.B RICT is consistent with the guidance of Section 2.3.4 of NEI 06-09. Include in this discussion that the uncertainty related to post-drywell failure reactor vessel injection has an inconsequential impact on the RICT calculations.
b) If, in response to part a), it cannot be justified that the conditional probability of failure of primary containment, i.e., drywell, failure has an inconsequential impact on the estimated RICTs, then identify potential additional contingencies or actions that can compensate for this uncertainty.
Constellation Response to APLA RAI 02.01 a) As discussed in the March 19, 2024, response letter (i.e., Reference 1), the scenario defined by TS 3.5.1.B (i.e., one LPCI subsystem inoperable OR one Core Spray subsystem inoperable) is conservatively modeled to include guaranteed failure of reactor pressure vessel (RPV) injection following a large drywell containment failure. An examination of the cutsets was performed and the results used as input to the process to develop risk management actions (RMAs) for consideration, as discussed in 2 of Reference 2. RMAs that compensate for the uncertainty and which could be considered are discussed in Response b, below.
b) For TS 3.5.1.B, one LPCI subsystem inoperable OR one Core Spray subsystem inoperable, additional RMAs may include:
Verify alignment and defer planned maintenance or testing activities on the redundant LPCI or Core Spray subsystem, and associated support equipment. Treat those systems as protected equipment.
Defer planned maintenance or testing that affects the reliability of those safety systems that provide defense-in-depth, such as drywell or torus venting. If testing or maintenance activities must occur, a review of the potential risk impact should be performed.
Minimize activities on the switchyard, SW, and RHRSW systems.
Briefing of on-shift Operations crew concerning restoring BOP support, including any compensatory measures established, and review of the appropriate abnormal operating procedures for a LOOP and SBO (QCOA 6100-03, QCOA 6100-04).
Briefing of on-shift Operations crew concerning DG alignment and AC bus crossties, including any compensatory measures established, and review of the appropriate operating procedures (QCOP 6600-16, QCOP 6620-17).
Briefing of on-shift Operations crew concerning containment high pressure scenarios, including any compensatory measures established, and review of the appropriate operating procedures (QGA 200, QCOP 1600-13).
QCNPS Request to Adopt TSTF-505 Attachment Response to APLA Request for Additional Information Page 3 of 3 Docket Nos. 50-254 and 50-265 Implement 10 CFR 50.65(a)(4) fire-specific RMAs associated with the LPCI and/or Core Spray subsystems.
References
- 1. Letter from M. D. Humphrey (Constellation Energy Generation, LLC) to U.S. NRC, "Response to Request for Additional Information Related to License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b,'"
dated March 19, 2024 (ADAMS Accession No. ML24079A122)
- 2. Letter from P. R. Simpson (Constellation Energy Generation, LLC) to U.S. NRC, "License Amendment Request to Revise Technical Specifications to Adopt Risk Informed Completion Times TSTF-505, Revision 2, 'Provide Risk-Informed Extended Completion Times - RITSTF Initiative 4b,'" dated June 8, 2023 (ADAMS Accession No. ML23159A249)