ML17277B007
| ML17277B007 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 10/10/2017 |
| From: | Steve Wyman Beyond-Design-Basis Engineering Branch |
| To: | Gardner P Northern States Power Co |
| Wyman S | |
| References | |
| Download: ML17277B007 (10) | |
Text
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. Peter A. Gardner Senior Vice President Northern States Power Company-Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362-9637 October 1 O, 2017
SUBJECT:
MONTICELLO NUCLEAR GENERATING PLANT-STAFF REVIEW OF MITIGATING STRATEGIES ASSESSMENT REPORT OF THE IMPACT OF THE REEVALUATED SEISMIC HAZARD DEVELOPED IN RESPONSE TO THE MARCH 12, 2012, 50.54(f) LETTER
Dear Mr. Gardner:
The purpose of this letter is to provide the U.S. Nuclear Regulatory Commission's (NRG) assessment of the seismic hazard mitigating strategies assessment (MSA), as described in the July 26, 2017, letter (Agencywide Documents Access and Management System (ADAMS)
Accession No. ML17208A015), submitted by Northern States Power Company - Minnesota (the licensee) doing business as Xcel Energy, for Monticello Nuclear Generating Plant (Monticello).
The NRG staff evaluated the Monticello strategies developed under Order EA-12-049 and described in Monticello's Final Integrated Plan (FIP) (ADAMS Accession No. ML17187A153).
The staff is currently reviewing Monticello's mitigating strategies and the review will be documented in a safety evaluation. The purpose of the staff's review is to ensure that the licensee has developed guidance and proposed designs which, if implemented appropriately, should adequately address the requirements of Order EA-12-049. An inspection by NRG staff will confirm compliance with the order and the inspection findings will be documented in a report and addressed in accordance with the Reactor Oversight Process. The following NRG staff review confirms that the licensee has adequately addressed the reevaluated seismic hazard within Monticello's mitigation strategies for beyond-design-basis external events.
BACKGROUND By letter dated March 12, 2012 (ADAMS Accession No. ML12053A340), the NRG issued a request for information pursuant to Title 10 of the Code of Federal Regulations (10 CFR),
Section 50.54(f) (hereafter referred to as the 50.54(f) letter). The 50.54(f) letter was issued as part of implementing lessons-learned from the accident at the Fukushima Dai-ichi nuclear power plant. Enclosure 1 to the 50.54(f) letter requested that licensees reevaluate the seismic hazard using present-day methodologies and guidance.
Concurrent with the reevaluation of seismic hazards, the NRG issued Order EA-12-049, "Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML12054A736). The order requires holders of operating power reactor licenses and construction permits issued under 10 CFR Part 50 to develop, implement, and maintain guidance and strategies to maintain or restore
core cooling, containment, and spent fuel pool cooling following a beyond-design-basis external event. In order to proceed with the implementation of Order EA-12-049, licensees used the current design basis flood and seismic hazard or the most recent flood and seismic hazard information, which may not be based on present-day methodologies and guidance, in developing their mitigation strategies.
On December 10, 2015 (ADAMS Accession No. ML16005A621), the Nuclear Energy Institute (NEI) submitted Revision 2 to NEI 12-06, including guidance for conducting MSAs using the reevaluated hazard information. The NRC subsequently endorsed NEI 12-06, Revision 2, with exceptions, clarifications, and additions, in Japan Lessons-Learned Division (JLD) interim staff guidance (ISG) JLD-ISG-2012-01, Revision 1, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events" (ADAMS Accession No. ML15357A163).
MITIGATION STRATEGIES ASSESSMENT By letter dated July 8, 2015 (ADAMS Accession No. ML15175A336), the NRC staff documented its review of the licensee's reevaluated seismic hazard, also referred to as the mitigation strategies seismic hazard information (MSSHI). The staff found that the Monticello Ground Motion Response Spectrum (GMRS) exceeds the safe shutdown earthquake (SSE) in the 1 to 10 Hertz (Hz) range and in the range above 10Hz, meriting a seismic risk evaluation, spent fuel pool evaluation and a high frequency (HF) confirmation. However, based on the NRC staff's further comparison of the GMRS to the SSE and the review of additional hazard and risk information, the NRC staff concluded, as described in letter dated October 27, 2015 (ADAMS Accession No. ML15194A015), that a seismic risk evaluation was not merited for Monticello. In addition, the staff concluded that the GMRS determined by the licensee adequately characterizes the reevaluated seismic hazard for the Monticello site.
By letter dated April 11, 2017 (ADAMS Accession No. ML17101A598), the licensee submitted a HF confirmation report for Monticello. By letter dated July 6, 2017 (ADAMS Accession No. ML17180A031 ), the NRC staff concluded, based on its review, that the licensee correctly implemented the guidance in conducting the HF confirmation for Monticello. There were 149 evaluated components that demonstrated adequate seismic capacity. There were four components that were addressed through operator actions and six components were replaced with new components having adequate seismic capacity.
By letter dated July 26, 2017 (ADAMS Accession No. ML17208A015), the licensee submitted its MSA report for Monticello. The licensee stated that the Monticello MSA was performed consistent with Appendix H of NEI 12-06, Revision 4, which describes acceptable methods for demonstrating that the reevaluated seismic hazard is addressed within the Monticello mitigation strategies for beyond-design-basis external events. Guidance document NEI 12-06, Revision 4 has not been officially endorsed at the time of this review. However, the NRC staff confirmed that the licensee's seismic hazard MSA is consistent with the guidance in Section H.4.4 of NEI 12-06, Revision 2, as endorsed by JLD-ISG-2012-01, Revision 1. Therefore, the methodology used by the licensee is acceptable to perform an assessment of the mitigation strategies that addresses the reevaluated seismic hazard.
The NRC staff performed checklist reviews of the seismic hazard MSA for Monticello. The checklists are provided as attachments to this letter. The NRC staff identified one deviation from guidance, but found that the licensee met the intent of the guidance. The staff did not
identify any deficiencies in the assessment. All evaluated components demonstrated adequate seismic capacity and no component modifications were required.
The NRC staff completed its review of the seismic hazard MSA for Monticello and concluded that sufficient information has been provided to demonstrate that the licensee's plans for the development and implementation of guidance and strategies under Order EA-12-049 appropriately address the reevaluated seismic hazard information stemming from the 50.54(f) letter.
If you have any questions, please contact me at (301) 415-3041 or via e-mail at Stephen.Wyman@nrc.gov.
Docket No. 50-263
Enclosure:
Technical Review Checklist cc w/encl: Distribution via Listserv Sincerely, Stephen Wyman, Project Manager Beyond-Design-Basis Engineering Branch Division of Licensing Projects Office of Nuclear Reactor Regulation
TECHNICAL REVIEW CHECKLIST BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO PATH FOUR MITIGATING STRATEGY ASSESSMENT MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 The NRC staff performed the following checklist review based on the July 26, 2017 (ADAMS Accession No. ML17208A015}, Mitigating Strategies Assessment (MSA) Report for Monticello.
Deviations, deficiencies, and conclusions are noted at the end of each section and an overall conclusion is provided at the end of the checklist.
I.
Background and Assessment to Mitigation Strategies Seismic Hazard Assessment (MSSHI)
This section establishes basic background and assessment to MSSHI criteria in Nuclear Energy Institute (NEI) 12-06, Appendix H.
Licensee approach to MSA:
Was the MSA conducted in accordance with NEI 12-06, Revision 2 ¥es I No as endorsed by the staff?
Was the MSA conducted using an alternate method?
Status of Order EA-12-049 Flexible Mitigation Strategy at the time of this review:
Yes-/ Ne Has the licensee submitted a Final Integrated Plan?
Yes; Ne Has the NRC staff completed a safety evaluation for the mitigation
¥es; No strategy?
Has the NRC staff confirmed compliance with Order EA-12-049 by
¥es / No successfully completing the temporary instruction (Tl}-191 inspection?
Status of MSSHI Did the licensee use the Ground Motion Response Spectra (GMRS) and Uniform Hazard Response Spectra (UHRS) as submitted in response to the 50.54(f) request for information and reviewed by the NRC staff?
Yes I Ne Enclosure Has the plant equipment relied on for FLEX strategies previously been evaluated as seismically robust to the plant safe shutdown earthquake (SSE) levels?
Is the maximum ratio of GMRS/SSE in the range of 1-10 Hertz (Hz) less than 2?
Did the licensee meet the seismic evaluation criteria described in NEI 12-06, Section H.5?
Yes/ No/ NA Yes I NG Yes /-Ne Notes from staff reviewer: The GMRS/SSE ratio is 1.49. This meets the criteria of NEI 12-06, H.5.
Deviation(s) or deficiency (ies) and Resolution: The licensee performed this MSA using NEI 12-06, Revision 4, but as of the date of performance of the MSA, only Revision 2 has been endorsed by the NRG staff. The NRG staff has determined that working to Revision 4 is acceptable because there are no substantive differences between the two revisions in the portions that are used for the MSA.
Gonsequence(s): None The NRG staff concludes:
The licensee meets the background and assessment to MSSHI criteria in NEI 12-06, Appendix H.
JI.
Expedited Seismic Evaluation Process (ESEP) Equipment Equipment used in support of the FLEX strategies has been evaluated to demonstrate seismic adequacy following the guidance in Section 5 of NEI 12-06. As stated in Appendix Hof NEI 12-06, previous seismic evaluations should be credited to the extent that they apply for the assessment of the MSSHI, including the ESEP evaluations performed in accordance with Electric Power Research Institute 3002000704.
Licensees may reference a previous ESEP submittal, submit a new or updated ESEP report, or provide other adequate justification or evaluation.
Did the licensee previously perform an ESEP?
Did the licensee provide a new or updated ESEP report with the MSA?
Yes I NG Yes/NG
¥0&/ No If the licensee did not perform ESEP, did they provide adequate justification that the expedited seismic equipment list structures, systems, and components (SSCs) are acceptable in accordance with the original guidance and in accordance with NEI 12-06 Section H.5 C10% capacity criteria?
If the licensee did not perform the ESEP, did they perform an evaluation consistent with the guidance in NEI 12-06, Section H.4.4, Steps 2 and 3, including the evaluation of FLEX components that were not previously evaluated to GMRS or 2 times the SSE?
Notes from staff reviewer: None Deviation(s) or deficiency(ies) and Resolution: None Consequence(s): None The NRC staff concludes:
- The licensee has evaluated seismic adequacy of equipment used in support of FLEX strategy consistent with the NEI 12-06, Appendix H guidance.
Ill Inherently I Sufficiently Rugged Equ1pmen Appendix H, Section 4.4 of NEI 12-06, Revision 2 documents the process and justification for inherently and sufficiently rugged SSCs.
The licensee:
Documented the inherently and sufficiently rugged SSCs consistent with the NEI 12-06 Appendix H guidance.
Yes/ No I NA Yes I No I NA Yes I Ne Yes I Ne Notes from staff reviewer: Inherently rugged items are documented in Section 2.3 of the Monticello MSA report.
Deviation(s) or deficiency(ies) and Resolution: None Consequence(s): None The NRC staff concludes:
The licensee's assessment of inherently and sufficiently rugged SSCs met the intent of the NEI 12-06, Appendix H guidance.
IV Evaluation of Components Not Covered by ESEP ESEP specifically excluded the evaluation of certain components of the FLEX strategy in an effort to provide stakeholders with near-term confidence in a plant's seismic capacity. However, licensees will be required to complete those evaluations as part of the Path 4 MSA to demonstrate compliance with the impending rule. Were the following components, not evaluated in the ESEP, evaluated as part of the MSA?:
FLEX Storage Building Non-seismic CAT I structures Operator Pathways credited in FLEX strategy Tie down of FLEX portable equipment Seismic interactions o
Masonry block wall o
Piping attached to tanks o
Flooding from non-seismically robust tanks o
Distributed systems (Piping/conduit/raceways/cable trays) o Other potential areas of interaction FLEX equipment haul paths Other equipment (list in Staff Reviewer Notes)
Did the licensee provide adequate description/documentation of the evaluation?
Notes from staff reviewer: None Deviation(s) or deficiency(ies) and Resolution: None Consequence(s): None Yes I Ne Yes/Ne Yes/ Nol NA Yes I Ne Yes I Ne Yes I Ne Yes I Ne Yes/ Ne Yes I Ne Yes I Ne Yes I Ne
¥es-/ No I-NA Yes I Ne The NRG staff concludes:
The licensee followed the NEI 12-06, Appendix H guidance in evaluating SSCs not deemed inherently rugged.
V.
Spent Fuel Pool (SFP) Cooling Per NEI 12-06, Appendix H, Section 4.4, licensees need to evaluate the adequacy of SFP cooling equipment to the GMRS. Most plants include the Order EA-12-051 SFP Level Instrument as part of the strategy.
The licensee:
- Clearly identified the SSCs and locations of the equipment that is part of the final FLEX SFP cooling strategy.
- Clearly stated the seismic design-basis (e.g. SSE) of the equipment used in the strategy.
Provided adequate description or documentation of the SFP cooling equipment's evaluation to the GMRS. Portable equipment and flexible hoses do not need to be evaluated.
Notes from staff reviewer: None Deviation(s) or deficiency(ies) and Resolution: None Consequence(s): None The NRG staff concludes:
VI.
High Frequency (HF)
Per NEI 12-06, Appendix H, Section 4.4, licensees with GMRS exceedance of the SSE above 10 Hz need to evaluate bi-stable components such as relays using the methodology described in NEI 12-06, Section H.4.2. The HF evaluation may have been submitted under separate letter or may be sent as an attachment to the MSA Report. The staff review checklist is included as an attachment to this report.
The licensee:
GMRS exceeds the SSE above 10 Hz.
Yes I Ne Yes /-NG Yes I Ne Yes I Ne Yes I Ne Yes I Ne Provided a HF evaluation as described in NEI 12-06, Section H.4.2.
Appeared to follow the guidance for the HF evaluation.
Provided results of demand vs. capacity with identification of resolutions as needed.
Yes I ~Jo/ NP.
Yes I No I NA Yes I No I NA Notes from staff reviewer: Monticello identified 101 components for the MSA HF evaluation. All components demonstrated seismic capacity greater than demand. A table with HF evaluation results was provided in the MSA report. No modifications were required.
Deviation(s) or deficiency(ies) and Resolution: None Consequence(s): None The NRC staff concludes:
The licensee's component capacity evaluation met the intent of the HF guidance.
VII.
==
Conclusions:==
Yes /-Ne The NRC staff assessed the licensee's implementation of the MSA guidance for Monticello.
Based on its review, the NRC staff concludes that the licensee's implementation of the MSA meets the intent of the guidance. The staff concludes that through the implementation of the MSA guidance, the licensee identified and evaluated the seismic capacity of the mitigating strategies equipment to ensure functionality will be maintained following a seismic event up to the GMRS. As noted in the review checklist, the staff identified one deviation (for which the licensee still meets the intent of the guidance) and no exceptions taken from the guidance. The licensee did not identify any necessary equipment modifications or changes to the strategy.
In summary, the NRC staff has reviewed the seismic hazard MSA for Monticello. The NRC staff concludes that sufficient information has been provided to demonstrate that the licensee's plans for the development and implementation of guidance and strategies under Order EA-12-049 appropriately address the reevaluated seismic hazard information stemming from the 50.54(f) letter.
ML172778007 SWyman, NRR BTitus, NRR EBowman, NRR MShams, NRR CWolf, OCA OFFICE NRR/DLP/PBEB/PM NRR/DLP/PBMB/LA NRR/DLP/PBEB/BC NAME SWyman (BTitus for)
SLent TBrown DATE 10/10/17 10/4/17 10/5/17 OFFICE NRR/DLP/PBEB/PM NAME SWyman (BTitus for)
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