ML22256A200
| ML22256A200 | |
| Person / Time | |
|---|---|
| Site: | Columbia  |
| Issue date: | 09/13/2022 |
| From: | Mahesh Chawla Plant Licensing Branch IV |
| To: | Collis T Energy Northwest |
| References | |
| L-2022-LLA-0023 | |
| Download: ML22256A200 (3) | |
Text
From:
Chawla, Mahesh Sent:
Tuesday, September 13, 2022 12:41 PM To:
Collis, Tracey M.
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:
APLC Q1 Followup.docx Ms Collis, 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.
A regulatory audit was conducted from 8/1/22 through 8/4/22. In a letter dated July 6, 2022 (ML22165A296), NRC transmitted a list of audit questions. Following the audit, the licensee provided responses to the audit questions on the electronic portal. The NRC staff has reviewed the responses and has additional follow up questions. The NRC staff would like to hold a teleconference to discuss these questions. Please let us know when you are available to discuss these questions with the NRC staff. 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 9/13/22 9/13/22
Hearing Identifier:
NRR_DRMA Email Number:
1775 Mail Envelope Properties (SA1PR09MB8415FEDBFC4A9273A6258A38F1479)
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:
9/13/2022 12:41:08 PM Received Date:
9/13/2022 12:41:08 PM From:
Chawla, Mahesh Created By:
Mahesh.Chawla@nrc.gov Recipients:
"Collis, Tracey M." <tmcollis@energy-northwest.com>
Tracking Status: None Post Office:
SA1PR09MB8415.namprd09.prod.outlook.com Files Size Date & Time MESSAGE 1438 9/13/2022 12:41:08 PM APLC Q1 Followup.docx 21442 Options Priority:
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APLC Q1 Follow-up Question:
In the response to APLC Question 1, the licensee discovered that the truncation limit has a significant impact on the mean SLERF value. The licensee also found that the mean solution is sensitive to the number of cutsets processed by ACUBE since the tool is not capable of processing the full solution. Therefore, the SLERF mean value reported in the licensees response was based on only 15,000 out of more than 70,000 cutsets processed by ACUBE.
Based on this approach, the licensee demonstrated that calculated mean SLERF with truncation at zero increases from 4.30E-6/yr to 8.35E-6/yr. Based on the difference between the point estimate and uncertainty mean for the cutsets processed by ACUBE, the licensee proposed the mean SLERF as 20 percent higher than the point estimate, which results in 6.19E-6/yr. In addition, the licensee also reported calculated mean SCDF from the zero truncation analysis as 2.95E-5/yr.
The NRC staff has the following discussion items related to the licensees response:
- a. Please explain (1) what is meant by zero truncation, and (2) the cause of the significant change in results with zero truncation (e.g., the change in the number of quantified cutsets).
- b. In the licensees SPRA Quantification (SPRA-2-QU-0001 Rev. 6), the initial truncation limit for determining the point estimate was selected based on a detailed study. Please explain, with justification, whether the truncation limit of 1E-12 per year for the SPRA point estimates needs to be decreased. The justification should identify any impact on the TSTF-505 and 10 CFR 50.69 applications (e.g., potential change in categorization outcome for 50.69 or changes in RICT durations). If the initial truncation limit for the SPRA point estimates needs to be decreased, provide the new truncation limit and resulting point estimates, demonstrating that the point estimates do not change significantly.