ML14195A034
| ML14195A034 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 07/16/2014 |
| From: | Michael Balazik Japan Lessons-Learned Division |
| To: | Heacock D Dominion Nuclear Connecticut |
| Balazik M, NRR/JLD, 415-2856 | |
| References | |
| Download: ML14195A034 (5) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. David A. Heacock President and Chief Nuclear Officer Dominion Nuclear Connecticut, Inc.
lnnsbrook Technical Center 5000 Dominion Boulevard Glen Allen, VA 23060-6711 July 16, 2014
SUBJECT:
MILLSTONE POWER STATION, UNIT 2-REQUEST FOR ADDITIONAL INFORMATION ASSOCIATED WITH NEAR-TERM TASK FORCE RECOMMENDATION 2.1, SEISMIC HAZARD AND SCREENING REPORT
Dear Mr. Heacock:
By letter dated March 31, 2014, to the Nuclear Regulatory Commission (NRC) (Agencywide Documents and Management System (ADAMS) Accession No. ML14092A417), Dominion Nuclear Connecticut, Inc., (the licensee), submitted for NRC review the Seismic Hazard and Screening Report, Response to NRC Request for Information Pursuant to 10 CFR 50.54(f)
Regarding Recommendation 2.1 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident for Millstone Power Station (Millstone), Units 2 and 3.
The NRC staff has reviewed the information provided for Millstone, Units 2 and 3, and has determined that additional information is required to complete the review. Enclosed is a request for additional information (RAI) related to the plant's Individual Plant Examination for External Events. As discussed with your staff during a recent phone call, the NRC staff requests that you respond no later than August 15, 2014.
If you have any questions related to the enclosed RAis or the requested submission date, please contact me at 301-415-2856 or via e-mail at michael.balazik@nrc.gov.
Docket No. 50-336
Enclosure:
Request for Additional Information cc w/encl: Distribution via Listserv Michael Balazik, Project M nager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation
REQUEST FOR ADDITIONAL INFORMATION NEAR-TERM TASK FORCE RECOMMENDATION 2.1.
SEISMIC HAZARD AND SCREENING REPORT DOMINION NUCLEAR CONNECTICUT. INC.
MILLSTONE POWER STATION. UNIT 2 DOCKET NO. 50-336 On March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued a request for information pursuant to Title 10 of the Code of Federal Regulations, Part 50 (10 CFR),
Section 50.54(f) (hereafter referred to as the 50.54 (f) letter) (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340). The purpose of the request was to gather information concerning, in part, the seismic hazards at operating reactor sites and to enable the NRC staff to determine whether licenses should be modified, suspended, or revoked. To respond to the 50.54(f) letter, Dominion Nuclear Connecticut (Dominion, the licensee) committed to follow the Electric Power Research Institute (EPRI)
Report, "Seismic Evaluation Guidance: Screening, Prioritization and Implementation Details (SPID) for the Resolution of Fukushima Near-Term Task Force Recommendation 2.1:
Seismic," (ADAMS Accession No. ML12333A170) as supplemented by the EPRI Report, "Seismic Evaluation Guidance: Augmented Approach for the Resolution of Fukushima Near-Term Task Force (NTTF) Recommendation 2.1: Seismic" (referred to as the Expedited Approach) (ADAMS Accession No. ML13102A142). Dominion submitted the re-evaluated seismic hazards (ADAMS Accession No. ML14092A417) for Millstone Power Station (Millstone), Units 2 and 3, in March 2014. The NRC staff conducted the screening and prioritization review of the submittal by assessing Dominion's screening evaluation and hazard analysis utilizing the endorsed SPID guidance. Accordingly, during the NRC screening and prioritization process, the staff identified that a determination could not be made and interactions with the licensee were needed to reach resolution. The staff identified Millstone, Unit 2 (MPS2), as a "conditional screen-in" for the purposes of prioritizing and conducting additional evaluations. On May 9, 2014, the NRC staff issued a letter (ADAMS Accession No. ML14111A147) documenting the NRC staff's screening results.
In accordance with the SPID and Expedited Approach guidance, the re-evaluated seismic hazard determines if additional seismic risk evaluations are warranted for a plant. The SPID guidance provides criteria for a plant with ground motion response spectra (GMRS) above the safe shutdown earthquake, but bounded by the Individual Plant Examination for External Events (IPEEE) capacity spectrum. To use the IPEEE capacity spectrum to screen out of conducting a seismic risk evaluation, the licensee needed to demonstrate the adequacy of Millstone's IPEEE evaluation by meeting the criteria in the SPID. If the IPEEE capacity is greater than the GMRS in the 1-10Hz range, the plant screens out of conducting a seismic risk.
The following additional information is requested to support the NRC's final screening determination for Millstone, Unit 2, based on IPEEE adequacy:
Enclosure After reviewing IPEEE Adequacy Evaluation and IPEEE High Confidence of a Low Probability of Failure (HCLPF) spectra (IHS) Development part of the Seismic Hazard and Screening Report for Millstone, Unit 2, herein called Appendix B, and the earlier IPEEE submittal for Millstone, Unit 2, the NRC staff has two requests for additional information.
The information will be reviewed by the NRC staff as part of the NRC staff evaluation of the IPEEE adequacy and, if needed, to support a follow-on audit of the items addressed in the requests.
- 1. As part of Appendix B, the licensee submitted a Peer-Review report which reviewed the HCLPF capacity calculations used in the IPEEE Seismic Margin Analysis (SMA). Table 2 of the Peer-Review report lists 6 components for which the HCLPF peak ground acceleration (PGA) in the IPEEE report for Millstone, Unit 2, is less that the plant HCLPF of 0.25g as shown in the table below (herein all HCLPFs are defined in terms of a 5-percent damping NUREG/CR-0098 rock spectral shape with the referred to PGA).
In agreement with the licensee submittal, Table 2 of the Peer-Review report describes how failure of three of those six structures, systems, and components (SSC) no longer affects the plant HCLPF and indicates that after a modification the revised HCLPF for another SSC increased to 0.29g. These components are the first four components in the table below.
The conclusion of the Peer-Review report is that once the licensee satisfactorily completes the actions listed in the notes column of the table below for the Battery Racks 081 and 082 and for the Chilled Water Surge Tank, the plant leveiiPEEE HCLPF can be considered to be the NUREG/CR-0098 spectral shape (5-percent damping) anchored at 0.25g PGA.
sse SSe HeLPF Notes Table 3.2-3 S&A IPEEE report Calculation Sheets 22S3-2-2 RSST 0.19 0.19 Failure of enclosure no longer Feeder Breaker affects the plant HCLPF (after a plant modification)
Block Wall 7.8 near 0.051 0.051 Failure does affect plant HCLPF Inverter 5 Inverter 5 Failure does affect plant HCLPF 120V AC Panel VR11 0.17 0.17 Following modifications the and VR21 calculated HCLPF is 0.29g Battery Racks DB1 0.13 0.061 Dominion will locate and and DB2 (Battery existing HCLPF calculation or 201A 201 B) reconstitute a calculation to confirm that the HCLPF capacity is greater than 0.25g Chilled Water Surge 0.22 0.136 Dominion will locate and Tank existing HCLPF calculation or reconstitute a calculation to confirm that the HCLPF capacity is greater than 0.25g In Appendix B (Section B5.6, page B-24), the licensee states that subsequently to the Peer-Review report field walkdowns and evaluations were performed to reconstitute the HCLPF calculations for these two SSCs (Battery Racks DB1 and DB1, and the Chilled Water Surge Tank). The conclusion in page B-24 of Appendix B is that the HCLPF capacity for each of these SSCs remains greater than or equal to the plant HCLPF capacity of 0.25g through modifications previously performed and/or evaluation of the as-built configuration. Appendix B refers to Dominion Engineering Technical Evaluation ETE-CEM-2014-0001 (Reference B7.27 of Appendix B) for the documentation of the evaluation of these two SSCs.
The new evaluations and related modifications result in an increase of the HCLPF for the two SSCs that are significant for the safety assessment, the Battery Racks DB1 and DB1, and the Chilled Water Surge Tank. However, these evaluations and modifications were not part of the IPEEE documentation previously reviewed by the NRC staff and were not part of the evaluations reviewed in the Peer-Review Report in Appendix B. To understand the details, scope and inputs for these new evaluations and related modifications for these two SSCs, the NRC staff requests:
- a. A detailed description of the methods and inputs for the new evaluations including how the new evaluations differed from the earlier evaluations for the MPS2 IPEEE, how the SSCs configurations changed from previously made modifications, and how the understanding of the as-built conditions changed from the earlier evaluations.
- b. A detailed description of the modifications to these SSCs, if any.
- 2. Table 7.1-1, Opportunities for Safety Enhancements, of the IPEEE submittal for MPS2 lists two SSCs identified as "items to be resolved". It is written in Table 7.1-1 that these two items are on the USI A-46 Safe Shutdown Equipment List and were being tracked under USI A-46. It is also written in Table 7.1-1 that the IPEEE program would support resolution of these items by providing relative risk significance of this issue in relation to all other USI A-46 issues. One of these two items was resolved with the Near Term Task Force 2.3 walkdowns. The remaining item is concerning air operated valve 2-CHW-11, which has a heavy yoke that is independently braced.
The NRC staff requests the following:
- a. Detailed description on how was this item was resolved and what is its safety significance, if any, in terms of the plant IPEEE HCLPF of 0.25g.
ML14195A034 MBalazik, NRR RidsNrrPMMillstone Resource RidsNrrLASLent Resource
- concurrence via e-mail OFFICE NRRIJLD/JHMB/PM NRRIDORL/LPL 1-1/PM* NRRIJLD/JHMB/LA NRRIJLD/JHMB/BC NAME MBalazik MThadani Slent SWhaley DATE 07/14/14 07/15/14 07/14/14 07/16/14