ML16335A176

Staff Review of Spent Fuel Pool Evaluation Associated with Reevaluated Seismic Hazard Implementing Near-Term Task Force Recommendation 2.1

ML16335A176
Person / Time
Site:	Monticello
Issue date:	12/08/2016
From:	Frankie Vega Japan Lessons-Learned Division
To:	Gardner P Northern States Power Company, Minnesota
Vega F, NRR/JLD 415-1617
References
CAC MF3958
Download: ML16335A176 (14)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 December 8, 2016 Mr. Peter A. Gardner Site Vice President Northern States Power Company -

Minnesota Monticello Nuclear Generating Plant 2807 West County Road 75 Monticello, MN 55362-9637

SUBJECT:

MONTICELLO NUCLEAR GENERATING PLANT- STAFF REVIEW OF SPENT FUEL POOL EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1 (CAC NO. MF3958)

Dear Mr. Gardner:

The purpose of this letter is to inform Northern States Power Company, a Minnesota Corporation (NSPM, the licensee), of the results of the U.S. Nuclear Regulatory Commission (NRC) staff's review of the spent fuel pool (SFP) evaluation for Monticello Nuclear Generating Plant (Monticello), which was submitted in response to Item 9 of Enclosure 1 of the NRC's March 12, 2012, request for information (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340), issued under Title 10 of the Code of Federal Regulations Part 50, Section 50.54(f) (hereafter referred to as the 50.54(f) letter). The NRC staff concludes that the licensee's assessment was performed consistent with the NRC-endorsed SFP Evaluation Guidance Report and that the licensee has provided sufficient information to complete the response to Item 9 of the 50.54(f) letter.

BACKGROUND On March 12, 2012, the NRC issued a 50.54(f) letter 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 seismic hazards at their sites using present-day methodologies and guidance. Enclosure 1, Item 4, of the 50.54(f) letter requested that licensees perform a comparison of the ground motion response spectrum (GMRS) and the safe shutdown earthquake (SSE). The staff's assessment of the information provided in response to Items 1-3 and 5-7 of the 50.54(f) letter is provided by letter dated July 8, 2015 (ADAMS Accession No. ML15175A336). Enclosure 1, Item 9, of the 50.54(f) letter requested that, when the GMRS exceeds the SSE in the 1 to 1O Hertz frequency range, a seismic evaluation be made of the SFP. More specifically, plants were asked to consider" ... all seismically induced failures that can lead to draining of the SFP."

P. Gardner By letter dated February 23, 2016 (ADAMS Accession No. ML16055A021 ), the Nuclear Energy Institute (NEI) staff submitted Electric Power Research Institute (EPRI) Report No. 3002007148 entitled, "Seismic Evaluation Guidance: Spent Fuel Pool Integrity Evaluation" (SFP Evaluation Guidance Report). The SFP Evaluation Guidance Report provides criteria for evaluating the seismic adequacy of an SFP to the reevaluated GMRS hazard levels. This report supplements the guidance in EPRI Report 1025287, "Seismic Evaluation Guidance: Screening, Prioritization and Implementation Details (SPID)" (ADAMS Accession No. ML12333A170), for plants where the GMRS peak spectral acceleration is less than or equal to 0.8g (low GMRS sites). The NRC endorsed the SFP Evaluation Guidance Report by letter dated March 17, 2016 (ADAMS Accession No. ML15350A158), as an acceptable method for licensees to use when responding to Item 9 in Enclosure 1 of the 50.54(f) letter.

By letter dated October 27, 2015 (ADAMS Accession No. ML15194A015), the NRC staff stated that SFP evaluation submittals for low GMRS sites are expected by December 31, 2016.

REVIEW OF LICENSEE SPENT FUEL POOL EVALUATION By letter dated October 28, 2016 (ADAMS Accession No. ML16302A246), the licensee submitted its SFP evaluation for Monticello for NRC review. The NRC staff assessed the licensee's implementation of the SFP Evaluation Guidance Report through the completion of a reviewer checklist, which is included as an enclosure to this letter.

TECHNICAL EVALUATION Section 3.0 of the SFP Evaluation Guidance Report develops SFP evaluation criteria for plants with GMRS peak spectral acceleration less than or equal to 0.8g. These criteria address SFP structural elements (e.g., floors, walls, and supports); non-structural elements (e.g.,

penetrations); seismically-induced SFP sloshing; and water losses due to heat-up and boil-off.

Section 3.0 also provides applicability criteria, which will enable licensees to determine if their site-specific conditions are within the bounds considered in developing the evaluation criteria for this report. The staff's review consists of confirming that these SFP site-specific conditions are within the bounds considered for the evaluation criteria specified in the SFP Evaluation Guidance Report.

1.1 Spent Fuel Pool Structural Evaluation Section 3.1 of the SFP Evaluation Guidance Report provides a SFP structural evaluation approach used to demonstrate that the SFP structure is sufficiently robust against the reevaluated seismic hazard. This approach supplements the guidance in Section 7 of the SPID and followed acceptable methods used to assess the seismic capacity of structures, systems, and components (SSCs) for nuclear power plants as documented in EPRI NP-6041, "A Methodology for Assessment of Nuclear Plant Seismic Margin, Revision 1." Table 3-2 of the SFP Evaluation Guidance Report (reproduced from Table 2.3 of EPRI NP-6041) provides the structural screening criteria to assess the SFPs and their supporting structures.

The licensee stated that it followed the SFP structural evaluation approach presented in the SFP Evaluation Guidance Report and provided site-specific data to confirm its applicability.

P. Gardner The NRG staff reviewed the structural information provided, which included the requested site-specific data in Section 3.3 of the SFP Evaluation Guidance Report, and confirmed that the evaluation criteria are applicable to the Monticello site. The staff concludes that SFP SSCs were appropriately evaluated and screened based on the seismic capacity criteria in EPRI NP-6041, and that the licensee has demonstrated that the SFP structure is sufficiently robust and can withstand ground motions with peak spectral acceleration less than or equal to 0.8g.

1.2 Spent Fuel Pool Non-Structural Evaluation Section 3.2 of the SFP Evaluation Guidance Report provides criteria for evaluating the non-structural aspects of the SFP, such as piping connections, fuel gates, and anti-siphoning devices, as well as SFP sloshing and heat up and boil-off of SFP water inventory. Specifically, Table 3-4 of the SFP Evaluation Guidance Report provides a summary of the SFP non-structural evaluation criteria derived in Section 3.2, along with applicability criteria to demonstrate that site-specific conditions are suitable for applying the evaluation criteria.

The licensee stated that it followed the SFP non-structural evaluation approach presented in the guidance report and provided site-specific data to confirm its applicability. The staff reviewed the non-structural information provided, which included the requested site-specific data in Table 3-4 of the SFP Evaluation Guidance Report, and confirmed that the evaluation criteria are applicable to the Monticello site. Therefore, the staff concludes that the licensee adequately evaluated the non-structural considerations for SSCs whose failure could lead to potential drain-down of the SFP due to a seismic event.

CONCLUSION The NRG staff reviewed the licensee's SFP evaluation report. Based on its review, the NRG staff concludes that the licensee's implementation of the SFP integrity evaluation met the criteria of the SFP Evaluation Guidance Report for Monticello and therefore, the licensee responded appropriately to Item 9 in Enclosure 1 of the NRC's 50.54(f) letter.

P. Gardner If you have any questions, please contact me at (301) 415-1617 or via e-mail at Frankie.Vega@nrc.gov.

Sincerely, v

Frankie Vega, Project Manager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket No. 50-263

Enclosure:

Technical Review Checklist cc w/encl: Distribution via Listserv

TECHNICAL REVIEW CHECKLIST BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO SPENT FUEL POOL EVALUATIONS FOR LOW GROUND MOTION RESPONSE SPECTRUM SITES IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1 SEISMIC MONTICELLO NUCLEAR GENERATING PLANT DOCKET NO. 50-263 BACKGROUND By letter dated March 12, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML12053A340), the U.S. Nuclear Regulatory Commission (NRC) issued a request for information to all power reactor licensees and holders of construction permits in active or deferred status, pursuant to Title 1O of the Code of Federal Regulations (1 O CFR), Section 50.54(f), "Conditions of Licenses" (hereafter referred to as the "50.54(f) letter). Enclosure 1 of the 50.54(f) letter requests addressees to reevaluate the seismic hazard at their site using present-day methods and guidance for licensing new nuclear power plants, and identify actions to address or modify, as necessary, plant components affected by the reevaluated seismic hazards. Enclosure 1, Item 4, of the 50.54(f) letter requested that licensees perform a comparison of the ground motion response spectrum (GMRS) with the safe shutdown earthquake (SSE). Enclosure 1, Item 9, requests that, when the GMRS exceeds the SSE in the 1 to 1O Hertz (Hz) frequency range, a seismic evaluation be made of the spent fuel pool (SFP).

More specifically, plants were asked to consider" ... all seismically induced failures that can lead to draining of the SFP."

Additionally, by letter dated February 23, 2016 (ADAMS Accession No. ML16055A021 ), the Nuclear Energy Institute (NEI) submitted Electric Power Research Institute (EPRI) Report No. 3002007148 entitled, "Seismic Evaluation Guidance: Spent Fuel Pool Integrity Evaluation" (SFP Evaluation Guidance Report). The SFP Evaluation Guidance Report supports the completion of SFP evaluations for sites with reevaluated seismic hazard exceedance in the 1 to 10 Hz frequency range. Specifically, the SFP Evaluation Guidance Report addressed those sites where the GMRS peak spectral acceleration (Sa) is less than or equal to 0.89 (low GMRS sites). The NRC endorsed the SFP Evaluation Guidance Report by letter dated March 17, 2016 (ADAMS Accession No. ML15350A158), as an acceptable method for licensees to use when responding to Item 9 in Enclosure 1 of the 50.54(f) letter. Licensee deviations from the SFP Evaluation Guidance should be discussed in their SFP evaluation submittal.

By letter dated October 28, 2016 (ADAMS Accession No. ML16302A246), Northern States Power Company, a Minnesota Corporation (NSPM, the licensee), doing business as Xcel Energy, provided an SFP report in a response to Enclosure 1, Item 9, of the 50.54(f) letter, for the Monticello Nuclear Generating Plant (Monticello). The NRC staff performed its review of the licensee's submittal to assess whether the licensee responded appropriately to Item 9 in of the 50.54(f) letter. The NRC staff checked whether the site-specific parameters are within the bounds of the criteria considered in the SFP Evaluation Guidance Report, verified the SFP's seismic adequacy to withstand the reevaluated GMRS hazard levels, and confirmed that the requested information in response to Item 9 of the 50.54(f) letter was provided.

Enclosure

A review checklist was used for consistency and scope. The application of this staff review is limited to the SFP evaluation as part of the seismic review of low GMRS sites as part of the Near-Term Task Force (NTTF) Recommendation 2.1.

NTTF Recommendation 2.1 Spent Fuel Pool Evaluations Technical Review Checklist for Monticello Nuclear Generating Plant (Monticello)

Site Parameters:

I. Site-Specific GMRS The licensee:

• Provided the site-specific GMRS consistent with the information Yes provided in the Seismic Hazard and Screening Report (SHSR), or its update, and evaluated by the staff in its staff assessment.

• Stated that the GMRS peak Sa is less than or equal to 0.8g for any Yes frequency.

Notes from the reviewer:

1. The NRC staff confirmed that the site-specific peak Sa= 0.339g (SHSR - ADAMS Accession No. ML14136A289).

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes:

• The site-specific GMRS peak Sa at any frequency is less than 0.8g . Yes

• The licensee's GMRS used in this evaluation is consistent with the Yes information provided in the SHSR.

Structural Parameters:

II. Seismic Design of the SFP Structure The licensee:

• Specified the building housing the SFP. Yes

• Specified the plant's peak ground acceleration (PGA). Yes

• Stated that the building housing the SFP was designed using an Yes SSE with a PGA of at least 0.1 g.

Notes from the reviewer:

1. The NRC staff confirmed that the SFP is housed in the reactor building which was seismically designed to the site SSE with a PGA of 0.12g (SHSR Section 3.1 and Updated Final Safety Analysis Report (UFSAR, Section 12.2.1 ).

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

• The structure housing the SFP was designed using an SSE with a Yes PGA of at least 0.1 g.

Ill. Structural Load Path to the SFP The licensee:

• Provided a description of the structural load path from the Yes foundation to the SFP.

• Performed screening based on EPRI NP-6041 Table 2-3 screening Yes criteria.

Notes from the reviewer:

1. The staff verified the structural load path to the SFP.

2. The staff confirmed that the structural load path to the SFP consists of reinforced concrete shear walls, reinforced concrete frames and structural steel frame elements.

(UFSAR Section 12.2.2.1.1 ).

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

• Licensee appropriately described the structural load path to the Yes SFP.

• Structures were appropriately screened based on the screening Yes criteria in EPRI NP-6041.

IV. SFP Structure Included in the Civil Inspection Program Performed in Accordance with Maintenance Rule The licensee:

• Stated that the SFP structure is included in the Civil Inspection Yes Program performed in accordance with Maintenance Rule (10 CFR 50.65).

Notes from the reviewer:

None Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

• The SFP structure is included in the Civil Inspection Program Yes performed in accordance with Maintenance Rule (1 O CFR 50.65).

Non-Structural Parameters:

V. Applicability of Piping Evaluation The licensee:

• Stated that piping attached to the SFP is evaluated to the SSE. No Notes from the reviewer:

1. The licensee did not state that the piping attached to the SFP up to the first valve was evaluated to the SSE. The licensee stated that no piping attached to the SFP is attached in such way that would cause a rapid drain-down of the SFP in the event of a postulated piping failure following a seismic event. Table 2.5.2 of the SFP evaluation provides a detailed description of all pipes associated with the SFP. For each specific SFP associated piping, the licensee described that, given their location and configuration (penetrations encountered at high elevations relative to the bottom of the SFP), any piping failure due to a seismic event is not postulated to cause a rapid drain-down of the SFP.

2. The staff reviewed the information provided regarding the location of the piping systems and its penetrations. All of these penetrations are located near the SFP normal water level. In addition, the staff considered how a oioina failure could potentially affect the overall assumptions described in the SFP evaluation guidance regarding the sloshing and boil-off analyses and calculated water losses. Given the stated piping elevations, any water loss due to a potential piping failure is expected to be less than the water loss calculated from seismically induced sloshing. Therefore, the NRC staff concludes that the bounding conditions in the SFP evaluation guidance are met, because the initial SFP water loss from a potential piping break would not exceed the potential water losses already considered for seismically induced sloshing.

3. Based on the review of the justification provided by the licensee regarding the location and configuration of piping associated with the SFP, NRC staff concludes that the information provided was sufficient to confirm applicability of the piping evaluation in Section 3.2 of the SFP guidance.

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

• The piping attached to the SFP is evaluated to the SSE. No

• Failure of piping attached to the SFP is not likely to result in rapid Yes drain-down as defined in the SFP evaluation guidance.

• Applicability criteria specified in Table 3-4 of SFP evaluation Yes guidance have been met.

VI. Siphoning Evaluation The licensee:

• Stated that anti-siphoning devices are installed on piping systems Yes that could lead to siphoning inventory from the SFP.

• In cases where anti-siphoning devices were not included on the applicable piping, a description documenting the evaluation N/A performed to determine the seismic adequacy of the piping is provided.

• Stated that the piping of the SFP cooling system cannot lead to rapid No drain down due to siphoning.

• Provided a seismic adequacy evaluation, in accordance with NP-N/A 6041 , for cases where active siphoning devices are attached to 2" or smaller piping with extremely large extended operators.

• Stated that no anti-siphoning devices are attached to 2" or smaller Yes piping with extremely large extended operators.

Notes from the reviewer:

1. The licensee stated that anti-siphoning devices are installed on all SFP piping that could lead to siphoning. Table 2.6.2 of the SFP evaluation provided a description of all the SFP piping that required anti-siphoning devices.

2. Licensee stated that no active anti-siphoning devices are attached to 2" or smaller piping with extremely large extended operator.

3. Piping of the SFP cooling system is not likely to lead to rapid draindown due to siphoning.

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes:

• Anti-siphoning devices exist in applicable piping systems that could lead to siphoning water from the SFP.

• No active anti-siphoning devices are attached to 2" or smaller piping Yes with extremely large extended operators.

• Applicability criteria specified in Table 3-4 of SFP evaluation Yes guidance have been met.

Yes VII. Sloshing Evaluation The licensee:

• Specified the SFP dimensions (length, width, and depth) . Yes

• Specified that the SFP dimensions are bounded by the dimensions Yes specified in the report (i.e. SFP length and width <125ft.; SFP depth >36ft.).

• Stated that the peak Sa in the frequency range less than 0.3 Hz is Yes less than 0.1 g.

Notes from the reviewer:

1. SFP dimensions:

- SFP Length - 40 ft.

- SFP Width - 26 ft.

- SFP Depth - 37 ft. 9 in.

2. The staff confirmed in the SHSR that the peak Sa in the frequency range less than 0.3 Hz is less than 0.1 g (SHSR).

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes:

• SFP dimensions are bounded by the dimensions specified in the Yes report (i.e. SFP length and width <125ft.; SFP depth >36ft.).

• The peak Sa in the frequency range less than 0.3 Hz is less than Yes 0.1g.

• Applicability criteria specified in Table 3-4 of SFP evaluation Yes guidance have been met.

VIII. Evaporation Evaluation The licensee:

• Provided the surface area of the plant's SFP . Yes

• Stated that the surface area of the plant's SFP is greater than Yes 500 ft 2

• Provided the licensed reactor core thermal power. Yes Yes

• Stated that the reactor core thermal power is less than 4,000 MW, per unit.

Notes from the reviewer:

1. Surface area of pool= 1,040 ft2

2. Reactor thermal power= 2,004 MW, (UFSAR Section 3.01 );

Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes:

• The surface area of the plant's SFP is greater than 500 ft 2 . Yes

• The reactor core thermal power is less than 4,000 MW1 per unit. Yes Yes

• Applicability criteria specified in Table 3-4 of SFP evaluation guidance have been met.

==

Conclusions:==

The NRC staff reviewed the licensee's SFP evaluation report. Based on its review, the NRC staff concludes that the licensee's implementation of the SFP integrity evaluation met the criteria of the SFP Evaluation Guidance Report for Monticello and therefore the licensee responded appropriately to Item 9 in Enclosure 1 of the 50.54(f) letter.

ML16335A176 *via e-mail OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRR/JLD/JHMB/BC(A)

NAME FVega Slent GBowman DATE 12/08/2016 11/30/2016 12/08/2016 OFFICE NRR/JLD/JHMB/PM NAME FVega DATE 12/08/2016