ML24135A018
| ML24135A018 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 05/13/2024 |
| From: | Robert Kuntz NRC/NRR/DORL/LPL3 |
| To: | Nicely K Exelon Generation Co |
| Kuntz R | |
| References | |
| Download: ML24135A018 (3) | |
Text
From:
Robert Kuntz Sent:
Monday, May 13, 2024 9:52 AM To:
Nicely, Ken M.:(Exelon Nuclear)
Subject:
DRAFT Request for Additional Information RE: Quad Cities TSTF-505 amendment
Dear Ken Nicely,
By letter dated June 8, 2023 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML23159A249), as supplemented by letters dated March 19 (ML24096B782), April 5 (ML24102A242), and May 10, 2024 (ML24131A079), Constellation Energy Generation, LLC (Constellation, the licensee) submitted a license amendment requests (LAR) for Quad Cities Nuclear Power Station (Quad Cities), Units 1 and 2. The proposed amendment would modify Renewed License Nos. DPR-29 and DPR-30, and the Technical Specifications (TSs) to adopt Technical Specifications Task Force (TSTF) Traveler TSTF-505, Revision 2, Provide Risk-Informed Extended Completion Times, RITSTF [Risk-Informed Technical Specification Task Force] Initiative 4b (ML18183A493).
The NRC staff has determined that additional information is needed to support its review. The attached is the NRC staffs draft request for additional information (RAI). If Constellation requires clarification on the attached draft RAI contact me to schedule a clarification discussion.
If no clarification is required, then the attached draft RAI will be considered a final RAI and the NRC staff expect a response 30 days from this message. If you have any questions, contact me.
Robert Kuntz Senior Project Manager NRC/NRR/DORL/LPL3 (301) 415-3733 DRAFT REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUESTS 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:
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.
Hearing Identifier:
NRR_DRMA Email Number:
2502 Mail Envelope Properties (SJ0PR09MB10897CD0F98437D3BEBCDB38299E22)
Subject:
DRAFT Request for Additional Information RE Quad Cities TSTF-505 amendment Sent Date:
5/13/2024 9:52:02 AM Received Date:
5/13/2024 9:52:00 AM From:
Robert Kuntz Created By:
Robert.Kuntz@nrc.gov Recipients:
"Nicely, Ken M.:(Exelon Nuclear)" <ken.nicely@constellation.com>
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