ML23318A472
| ML23318A472 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 11/14/2023 |
| From: | David Helker Constellation Energy Generation |
| To: | Office of Nuclear Reactor Regulation, Document Control Desk |
| References | |
| TSTF-59-A | |
| Download: ML23318A472 (1) | |
Text
200 Exelon Way Kennett Square, PA 19348 www.ConstellationEnergy.com 10 CFR 50.90 November 14, 2023 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Calvert Cliffs Nuclear Power Plant, Units 1 and 2 Renewed Facility Operating License Nos. DPR-53 and DPR-69 NRC Docket Nos. 50-317 and 50-318
Subject:
Supplement to License Amendment Request to Adopt TSTF-59-A References
- 1. License Amendment Request to Adopt TSTF-59-A, Incorporate
[Combustion Engineering] NPSD-994 Recommendations into the [Safety Injection Tanks] Specification, Revision 1, dated June 13, 2023 (ADAMS Accession No. ML23164A170)
- 2. U.S. Nuclear Regulatory Commission (NRC) email to Constellation Energy Generation, LLC (CEG), Acceptance review for Calvert Cliffs TSTF-59A (EPID L-2023-LLA-0091), dated June 30, 2023 In accordance with 10 CFR 50.90, Application for amendment of license, construction permit, or early site permit, Constellation Energy Generation, LLC (CEG) requested approval of changes to Renewed Facility Operating License Nos. DPR-53 and DPR-69 for Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CCNPP) in the Reference 1 submittal on June 13, 2023. The NRC accepted the license amendment request for review on June 30, 2023.
CEG is providing a supplement to the Reference 1 submittal to document a discussion of the CCNPP Probabilistic Risk Assessment (PRA) models technical acceptability and an evaluation of the risk associated with the proposed TS changes based on the current revision, Revision 3, of Regulatory Guide 1.174, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis.
The supplemental risk information is provided in the attachment to this letter.
CEG has reviewed the information supporting a finding of no significant hazards consideration, and the environmental consideration, that were previously provided to the NRC in the Reference 1 submittal. CEG has concluded that the information provided in this supplement does not affect the bases for concluding that the proposed license amendments do not involve a significant hazards consideration under the standards set forth in 10 CFR 50.92. In addition, CEG has concluded that the information in this supplemental letter 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 amendments.
This letter and its attachment contain no regulatory commitments.
Supplement to License Amendment Request to Adopt TSTF-59-A November 14, 2023 Page 2 In accordance with 10 CFR 50.91, "Notice for public comment; State consultation,"
paragraph (b), CEG is notifying the State of Maryland of this supplement by transmitting a copy of this letter and its attachment to the designated State Official.
Should you have any questions concerning this supplement, please contact Ms. Wendi E.
Para at Wendi.Para@Constellation.com or at (267) 533-5208.
I declare under penalty of perjury that the foregoing is true and correct. Executed on the 14th day of November 2023.
Respectfully, David P. Helker Sr. Manager - Licensing Constellation Energy Generation, LLC
Attachment:
Risk Information Supporting the License Amendment Request to Adopt TSTF-59-A cc:
USNRC Region I, Regional Administrator USNRC Senior Resident Inspector, Calvert Cliffs Nuclear Power Plant USNRC Project Manager, NRR - Calvert Cliffs Nuclear Power Plant S. Seaman, State of Maryland
Attachment:
Risk Information Supporting the License Amendment Request to Adopt TSTF-59-A Page 1 of 3 1.0 PRA TECHNICAL ACCEPTABILITY The Calvert Cliffs Nuclear Power Plant, Units 1 and 2 (CCNPP) Probabilistic Risk Assessment (PRA) models quality are acceptable for this application based on the NRC's approval of the CCNPP Risk-Informed Completion Time (RICT) license amendment request (Reference 3.1).
The CCNPP PRA models satisfy the technical acceptability guidance of RG 1.200 (Reference 3.2); and the models have an acceptable periodic update and review process. As stated in Reference 3.1:
"Based on the NRC staffs review of the licensee's submittal and assessments, the NRC staff concludes that the Calvert Cliffs PRA models for internal events (including internal flooding) and fire events used to implement the RICT program satisfy the guidance of RG 1.200. The NRC staff based this conclusion on the findings that the PRA models conform sufficiently to the applicable industry PRA standards for internal events (including internal flooding) and fires at an appropriate capability category, considering the licensee's acceptable disposition of the peer review and NRC staff review findings.
The NRC staff finds the licensee's PRA acceptable to support the RICT program because the licensee has (1) reviewed the PRA using endorsed guidance and adequately resolved all identified issues, and (2) established a periodic update and review process to update the PRA and associated [Configuration Risk Management Program] model to incorporate changes made to the plant and PRA methods and data consistent with the RICT program 2.0 RISK ANALYSIS Per the risk analysis performed for this change (Reference 3.3), the safety injection tanks (SITs) are of low risk significance in the CCNPP PRA models (henceforth referred to as the PRA model). In the PRA model, the SITs are only required to mitigate large loss-of-coolant-accident (LOCA) events, and the frequency of large LOCA initiating events is 6.05E-06. The success criterion is 2-of-4 SITs injecting into intact cold legs.
The SITs are not credited in the Fire PRA, as no fire scenarios lead to a large LOCA.
The risk from external events is insignificant. Any seismic event sufficiently challenging to cause a large LOCA will also fail the refueling water storage tank (RWST). As the RWST is required for all LOCA mitigation, there would be no change in risk from seismic events due to the unavailability of a SIT, required for large LOCAs. High wind events do not drive a large LOCA.
Other external hazards are screened or shown to not to be a significant consideration for the Risk Informed Completion Time (RICT) license amendment.
2.1 Analysis Since the frequency of the large LOCA events is very low, and the duration of the completion time extension is only 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, a bounding and simplified approach is used to calculate incremental conditional core damage probability (ICCDP) and incremental conditional large early release probability (ICLERP).
A bounding ICCDP and ICLERP are calculated by multiplying the large LOCA initiating event by the 24-hour scaling factor. This is a conservative approach, as it assumes that any large LOCA event that occurs during a one-hour SIT unavailability goes straight to core damage and large early release.
Attachment:
Risk Information Supporting the License Amendment Request to Adopt TSTF-59-A Page 2 of 3 The scaling factor to adjust annualized initiating event frequency to the 24-hour Technical Specification (TS) Completion Time (CT) is:
1 day/365.25 days = 2.74E-03 The bounding ICCDP and ICLERP calculation is:
- 24-hour factor = 6.05E-06
- 2.74E-03 = 1.66E-08 Compared to the RG 1.177 (Reference 3.4) acceptance criteria:
1.66E-08 ICCDP < 1E-06 1.66E-08 ICLERP < 1E-07 2.2 Uncertainty For this simplified analysis, two sources of potential uncertainty are identified:
- 1) There is uncertainty with the LOCA break frequencies. If the frequencies are doubled, the proposed TS CT change still meets the RG 1.177 acceptance criteria for a "very small change" in core damage frequency (CDF) and large early release frequency (LERF).
1.66E-08
- 2 = 3.31E-08 << 1E-06 and <<1E-07
- 2) The SIT Limiting Condition for Operation (LCO) may be applied more than once during the year. Assuming four, 24-hour instances of entry into the LCO during a year, the cumulative total of the TS CT change still meets the RG 1.177 acceptance criteria for a very small change for CDF and LERF.
1.66E-08
- 4 = 6.62E-08 << 1E-06 and <<1E-07 2.3 Conclusion As discussed in the NRC's approval of the CCNPP RICT license amendment request (Reference 3.1), CCNPPs total CDF and LERF meet the 1E-04/year CDF and 1E-05/year criteria of RG 1.174 (Reference 3.5).
Using a conservative and bounding analysis, the proposed TS CT change to LCO 3.5.1B is acceptable when compared to RG 1.177. Using the bounding calculation, ICCDP is less than 1E-06/year and ICLERP is less than 1E-07/year.
The change in CDF of <1.0E-07 per year also is within the very small change acceptance guideline published in Regulatory Guide 1.174.
Attachment:
Risk Information Supporting the License Amendment Request to Adopt TSTF-59-A Page 3 of 3
3.0 REFERENCES
3.1 NRC Letter to Exelon Generation Company, LLC, "Calvert Cliffs Nuclear Power Plant, Units 1 and 2-Issuance of Amendment Nos. 326 and 304 to Add Risk-Informed Completion Time Program (EPID L-2016-LLA-0001)," (ADAMS Accession No. ML18270A130), October 30, 2018.
3.2 NRC Regulatory Guide 1.200, "An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities," Revision 2, March 2009.
3.3 CA-LAR-018, Calvert Cliffs Nuclear Power Plant, "Risk Assessment to Support TSTF-59-A Supplemental Letter," Revision 0, November 2023.
3.4 Regulatory Guide 1.177, "Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," January 2021.
3.5 Regulatory Guide 1.174, Revision 3, "An Approach For Using Probabilistic Risk Assessment In Risk-Informed Decisions On Plant-Specific Changes To The Licensing Basis," January 2018.