ML22210A007
| ML22210A007 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 07/28/2022 |
| From: | Mahesh Chawla Plant Licensing Branch IV |
| To: | Maysam A Energy Northwest |
| References | |
| L-2022-LLA-0023 | |
| Download: ML22210A007 (4) | |
Text
From:
Chawla, Mahesh Sent:
Thursday, July 28, 2022 5:20 PM To:
Maysam, Al Cc:
Garcia, Richard M.; Wilk, Mark; Hilsmeier, Todd; Bucholtz, Kristy; Tetter, Keith; Neuhausen, Alissa; Hyslop, JS; Vasavada, Shilp; Iqbal, Naeem; Dinh, Thinh
Subject:
Draft - Additional audit question - Columbia Generating Station - Regulatory audit question for LAR to revise TS to adopt TSTF-505, Revision 2 (EPID L-2022-LLA-0023)
Attachments:
Draft audit question regarding SPRA mean values_28Jul2022.docx Mr. Maysam, By letter dated February 3, 2022 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML22034A992), Energy Northwest (the licensee) submitted a license amendment request for Columbia Generating Station (Columbia). The proposed amendment would modify Columbias Technical Specification requirements to permit the use of risk-informed completion times in accordance with Technical Specifications Task Force (TSTF)
Traveler TSTF-505, Provide Risk-Informed Extended Completion Times - RITSTF
[Risk-Informed TSTF] Initiative 4b, Revision 2.
On March 18, 2022 (ML22068A234), the U.S. Nuclear Regulatory Commission (NRC) staff issued an audit plan that conveyed intent to conduct a regulatory audit to support its review of the subject license amendment request. In the audit plan, the NRC staff requested an electronic portal setup and provided a list of documents to be added to the portal. In a letter dated July 6, 2022 (ML22165A296), NRC transmitted a list of audit questions.
The NRC staff has additional draft audit question attached for the upcoming audit from 8/1/22 through 8/4/22. Please include this in the discussion during the audit. Thanks Sincerely, Mahesh Chawla, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission ph: 301-415-8371 Docket No. 50-397 OFFICE DORL/LPL4/PM DORL/LPL4/BC NAME MChawla JDixon-Herrity DATE 7/28/22 7/28/22
Hearing Identifier:
NRR_DRMA Email Number:
1733 Mail Envelope Properties (SA1PR09MB84153BB9AED3D3A4BC91324BF1969)
Subject:
Draft - Additional audit question - Columbia Generating Station - Regulatory audit question for LAR to revise TS to adopt TSTF-505, Revision 2 (EPID L-2022-LLA-0023)
Sent Date:
7/28/2022 5:19:41 PM Received Date:
7/28/2022 5:19:41 PM From:
Chawla, Mahesh Created By:
Mahesh.Chawla@nrc.gov Recipients:
"Garcia, Richard M." <rmgarcia@energy-northwest.com>
Tracking Status: None "Wilk, Mark" <mark.wilk@pnnl.gov>
Tracking Status: None "Hilsmeier, Todd" <Todd.Hilsmeier@nrc.gov>
Tracking Status: None "Bucholtz, Kristy" <Kristy.Bucholtz@nrc.gov>
Tracking Status: None "Tetter, Keith" <Keith.Tetter@nrc.gov>
Tracking Status: None "Neuhausen, Alissa" <Alissa.Neuhausen@nrc.gov>
Tracking Status: None "Hyslop, JS" <JS.Hyslop@nrc.gov>
Tracking Status: None "Vasavada, Shilp" <Shilp.Vasavada@nrc.gov>
Tracking Status: None "Iqbal, Naeem" <Naeem.Iqbal@nrc.gov>
Tracking Status: None "Dinh, Thinh" <Thinh.Dinh@nrc.gov>
Tracking Status: None "Maysam, Al" <amaysam@energy-northwest.com>
Tracking Status: None Post Office:
SA1PR09MB8415.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 1547 7/28/2022 5:19:41 PM Draft audit question regarding SPRA mean values_28Jul2022.docx 18340 Options Priority:
Normal Return Notification:
No Reply Requested:
No Sensitivity:
Normal Expiration Date:
Regulatory Basis:
Section 2.3 of Regulatory Guide (RG) 1.174, Revision 3, An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis (ADAMS Accession No. ML17317A256), describes acceptability of a probabilistic risk assessment (PRA). The PRA analysis used to support an application is measured in terms of its appropriateness with respect to scope, level of detail, conformance with the technical elements, and plant representation. RG 1.200, Revision 2 (ADAMS Accession No. ML090410014),
provides detailed guidance on technical acceptability of a PRA used to support risk-informed applications.
In Attachment 2 of the CGS 10 CFR 50.69 LAR, dated November 9, 2022 (ADAMS Accession No. ML21314A224), states the SPRA point estimate for LERF as 5.16E-06 per year and the response to Audit Item APLA-02 of the CGS 10 CFR 50.69 supplement, dated May 10, 2022 (ADAMS Accession No. ML22130A591), states the SPRA mean for LERF as 4.3E-06 per year.
The NRC staff notes that the mean seismic LERF (SLERF) is lower than the point estimate by 8.6E-07 per year and the supplemental response provided no justification for the mean value being lower than the point estimate by seventeen percent. The NRC staffs experience reviewing SPRAs mean values and point estimates are appreciably different with the mean value higher than the point estimate. Enclosure 2 of the April 28, 2020, CSG - Staff Review of Seismic Risk (ADAMS Accession No. ML20076A547), the seismic CDF mean value of 4.83E-05 per year was provided by the licensee with the point estimate value at 2.0E-05 per year and a seismic LERF mean value of 1.58E-05 per year with the associated point estimate of 8.8E-06 per year. The mean values provided in the April 28, 2020, seismic assessment is 142 and 80 percent higher than the point estimates for CDF and LERF respectively.
Audit Question:
Based on above observations, please address the following:
a) Provide the seismic mean CDF and LERF values for the CGS SPRA model. Include in this discussion how the seismic mean values compare to its associated point estimates.
b) If the comparison in part (a) demonstrates the mean values are either slightly higher (e.g., less than 20 percent) or lower than the point estimates, provide justification that the calculation of the mean values is reasonable.
c) Alternatively to parts (a) and (b), provide updated seismic CDF and LERF mean values.
Include in this discussion justification that the calculation of the mean values is reasonable.
d) Using either the mean seismic values in part (a) or updated values in part (c),
demonstrate how the CGS total CDF and LERF mean values (internal events/flooding, fire, and seismic) meet RG 1.174 threshold requirements of 1E-04 per year for CDF and 1E-05 per year for LERF.