ML21222A119
| ML21222A119 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 08/12/2021 |
| From: | Dennis Galvin NRC/NRR/DORL/LPL4 |
| To: | Gerry Powell South Texas |
| Galvin D | |
| References | |
| EPID L 2021-LLA-0004 | |
| Download: ML21222A119 (5) | |
Text
August 12, 2021 LICENSEE:
STP Nuclear Operating Company FACILITY:
South Texas Project, Units 1 and 2
SUBJECT:
SUMMARY
OF JULY 26, 2021, MEETING WITH STP NUCLEAR OPERATING COMPANY REGARDING A LICENSE AMENDMENT REQUEST TO REVISE THE MODERATOR TEMPERATURE COEFFICIENT SURVEILLANCE REQUIREMENTS FOR SOUTH TEXAS PROJECT, UNITS 1 AND 2 (EPID L-2021-LLA-0004)
On July 26, 2021, an observation meeting, conducted as a webinar, was held between the U.S. Nuclear Regulatory Commission (NRC) staff and representatives of the STP Nuclear Operating Company (the licensee). Staff from Westinghouse Electric Company, LLC and the Pressurized Water Reactors Owners Group (PWROG) and member organizations also attended. The purpose of the meeting was to discuss a proposed supplement to the license amendment request (LAR) submitted January 13, 2021 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML21014A213) regarding South Texas Project, Units 1 and 2 (STP). The proposed amendments would modify Technical Specification (TS)
Surveillance Requirements (SRs) 4.1.1.3.a and b. and TS 6.9.1.6.b. This change is being proposed to revise the beginning of life and end of life moderator temperature coefficient (MTC)
SRs to allow the use of a calculated value instead of a measurement to verify the MTC limits are met. The meeting notice and agenda, dated July 15, 2021, are available in ADAMS at Accession No. ML21196A413. A list of attendees is enclosed.
The licensee presented informational slides at the meeting, which can be found in ADAMS at Accession No. ML21203A270. During the meeting, the licensee provided background information on the revised MTC SRs, other measurements that collaborate the prediction of the MTC, and how analytical codes are already used in SRs. The licensee and the NRC staff discussed each of these topics.
The NRC provided feedback on several issues to consider in a potential supplement to the LAR.
The licensee has proposed that the calculated value used to verify the MTC limits are met would be determined using an NRC-approved neutronics analysis model. NRC staff noted that the neutronics analysis models were not explicitly reviewed and approved for this purpose.
The licensee used data from the past 20 years of fleet operating experience to quantify MTC uncertainty. This approach effectively pools the data from the fleet (which includes different fuel types, plant types, and different neutronics analysis models) into a single population to determine the uncertainty applied for a specific plant. The licensee indicated that the pooling approach is needed because there is insufficient plant specific data to justify an useable uncertainty value. The NRC staff indicated that the pooling approach had some statistical flaws. Several potential solutions were discussed:
o PWROG staff suggested increasing the uncertainty value from pooling the fleet data to encompass all previously measured data.
o The NRC staff suggested performing statistical analysis to demonstrate how the mean and standard deviation based on fleet data could be applied to STP.
o The NRC staff noted having a requirement to measure the MTC every few cycles, rather than removing the requirement to measure the MTC, may be a way to reduce the technical justification needed to make a reasonable assurance finding.
The NRC staff observed that, comparable to the existing footnote on SR 4.1.1.3.b, the TSs may need to specify the method and criteria for using a calculated value in place of measuring the MTC.
The NRC staff expressed concern about the applicability of the proposed approach and supporting data to other licensing basis changes that affect the core design. NRC staff suggested that the licensee include applicability limitations. which would ensure that its approach would provide comparable assurance to measurement.
The NRC staff noted that a substantive discussion of the process described by the licensee in its presentation, and its limits, would need to be submitted on the docket in order for NRC staff to perform a formal review.
As part of the presentation, the licensee suggested that other surveillances could be used as surrogate measures to provide assurance that the MTC is within the TS limit.
NRC staff recommended that STP provide a stronger quantitative justification that these alternate surveillances, along with their associated acceptance criteria, would be sufficient to support the overall reasonable assurance finding that the MTC will be within the limit.
The NRC staff also indicated that due to the anticipated change in scope from the original LAR, either a new review would likely need to be opened or the schedule extended, with the particular approach dependent on the actual supplement.
The licensee indicated that it would consider the issues raised by the NRC staff and would get back to the NRC staff on its path forward.
No members of the public attended the meeting. No regulatory decisions or commitments were made at the meeting. Additionally, the NRC staff did not receive Public Meeting Feedback forms.
Please direct any inquiries to me at 301-415-6256 or by e-mail at Dennis.Galvin@nrc.gov.
/RA/
Dennis J. Galvin, Project Manager Plant Licensing Branch IV Division of Operator Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-498 and 50-499
Enclosure:
List of Attendees cc: Listserv
Enclosure LIST OF ATTENDEES JULY 26, 2021, MEETING REGARDING A LICENSE AMENDMENT REQUEST TO REVISE THE MODERATOR TEMPERATURE COEFFICIENT SURVEILLANCE REQUIREMENT STP NUCLEAR OPERATING COMPANY SOUTH TEXAS PROJECT, UNITS 1 AND 2 U.S. Nuclear Regulatory Commission R. Beaton D. Galvin M. Hamm N. Jordan J. Kaizer S. Krepel A. Rau W. Richards STP Nuclear Operating Company K. Aucoin W. Brost N. Hall T. Hammons D. Richards F. Yilmaz Westinghouse/PWROG J. Andrachek J. Laird M. Grider Dominion Energy/PWROG B. Mount Duke Energy/PWROG S. Thomas
- by e-mail concurrence OFFICE NRR/DORL/LPL4/PM*
NRR/DORL/LPL4/LA*
NRR/DSS/SNSB/BC*
NAME DGalvin PBlechman SKrepel DATE 8/12/2021 8/12/2021 8/10/2021 OFFICE NRR/DSS/STSB/BC(A)*
NRR/DORL/LPL4/BC*
NRR/DORL/LPL4/PM*
NAME NJordan JDixon-Herrity DGalvin DATE 8/8/2021 8/12/2021 8/12/2021