ML16291A021

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

ML16291A021
Person / Time
Site:	Dresden
Issue date:	11/08/2016
From:	Frankie Vega Japan Lessons-Learned Division
To:	Bryan Hanson Exelon Generation Co, Exelon Nuclear
Vega F, NRR/JLD 415-1617
References
CAC MF3877, CAC MF3878
Download: ML16291A021 (13)

Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 November 08, 2016 Mr. Bryan C. Hanson Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 605

SUBJECT:

DRESDEN NUCLEAR POWER STATION, UNITS 2 AND 3 - STAFF REVIEW OF SPENT FUEL POOL EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1 (CAC NOS. MF3877 AND MF3878)

Dear Mr. Hanson:

The purpose of this letter is to inform Exelon Generation Company, LLC (Exelon, the licensee) of the results of the U.S. Nuclear Regulatory Commission (NRC) staff's review of the spent fuel pool (SFP) evaluation for Dresden Nuclear Power Station, Units 2 and 3 (Dresden), 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 1O 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 April 27, 2015 (ADAMS Accession No. ML15097A519). 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."

B.Hanson 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 August 31 , 2016 (ADAMS Accession No. ML16244A801 ), Exelon submitted its SFP evaluation for Dresden 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 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.

The NRC 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

B.Hanson evaluation criteria are applicable to the Dresden 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 Dresden site. Therefore, the staff concludes that the licensee acceptably 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 NRC staff reviewed Exelon '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 Dresden and therefore, Exelon responded appropriately to Item 9 in Enclosure 1 of the NRC's 50.54(f) letter.

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

Sincerely, Franki Vega.Z:-:anager Hazards Management Branch Japan Lessons-Learned Division Office of Nuclear Reactor Regulation Docket Nos. 50-237 and 50-249

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 DRESDEN NUCLEAR POWER STATION. UNITS 2 AND 3 DOCKET NOS. 50-237 AND 50-249 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 10 of the Code of Federal Regulations (10 CFR) , Section 50.54(f), "Conditions of License" (hereafter referred to as the "50.54(f) letter"). 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 1O 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 0.8g (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. Licensee deviations from the SFP Evaluation Guidance should be discussed in their SFP evaluation submittal.

By letter dated August 31 , 2016 (ADAMS Accession No. ML16244A801), Exelon Generation Company, LLC (Exelon , the licensee) provided an SFP report in a response to Enclosure 1, Item 9, of the 50.54(f) letter, for the Dresden Nuclear Power Station, Units 2 and 3 (Dresden).

The NRC staff performed its review of the licensee's submittal to assess whether the licensee responded appropriately to Item 9 in Enclosure 1 of the 50.54(f) letter. A multidisciplinary team 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 Enclosure

reevaluated GMRS hazard levels, and confirmed that the requested information in response to Item 9 of the 50.54(f) letter was provided.

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 Dresden Nuclear Power Station, Units 2 and 3 (Dresden)

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= 0.59g (ADAMS Accession No. ML14091A012).

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 SSE with a PGA of at least 0.1g. Yes

Notes from the reviewer:

1. The NRC staff confirmed that the SFP is housed in the reactor building which was designed to the SSE with PGA of 0.20g (SHSR, Section 3.1 and Updated Final Safety Analysis Report (UFSAR) , Section 9.1 .2.2).

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 0.1g.

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:

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

3. The staff confirmed that the structural load path from the foundation to the SFP consists of reinforced concrete shear walls, slabs, and framing members (UFSAR Section 9.1 .2.2.3)

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.

Yes

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

IV. SFP Structure Included in the Civil Inspection Program Perlormed 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 (1 O 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 (10 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. Yes Notes from the reviewer:

1. The licensee stated that following piping are attached to the SFP: fuel pool gates drain line and the fuel pool cooling system. The fuel pool gates drain line was classified as safety related up to the first isolation valve and was evaluated to the SSE. The fuel pool cooling system was classified as non-safety related and its seismic design was reviewed to NRC's Systematic Evaluation Program (SEP) - "Seismic Design Consideration" and meet the requirements of Regulatory Guide 1.29 "Seismic Design Classification for Nuclear Power Plants".

2. Even though it was not explicitly stated that the SFP cooling system was evaluated to the SSE, it was reviewed under NRC's SEP and met RG 1.29 which assessed the seismic capabilities of the piping system. NRC staff concludes that the information provided was sufficient to confirm applicability of the piping evaluation in Section 3.2 of the SFP evaluation guidance.

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

No deviations or deficiencies were identified.

The NRC staff concludes that:

• 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-6041, for cases where active siphoning devices are attached to 2" or No 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. In addition, the licensee stated that all penetrations into the SFP are located above a fixed height from the bottom such that there must always be a safe level of water above the fuel.

2. UFSAR Section 9.1.3.3 confirms that openings in the two spent fuel pool cooling system return lines were designed to act as anti-syphon devices.

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

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 Yes 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.

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 0.1g.

Notes from the reviewer:

1. Verified the SFP dimensions (UFSAR Section 9.1 .2.2.3):

- SFP Length - 41 ft.

- SFP Width - 33 ft.

- SFP Depth - 39 ft.

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

• Stated that the reactor core thermal power is less than 4,000 Yes MW1per unit.

Notes from the reviewer:

1. Surface area of pool = 1,353 ft 2

2. Reactor thermal power= 2,957 MW1(Unit 2 and 3, UFSAR Section 1.1.1);

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

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

==

Conclusions:==

The NRC staff reviewed Exelon '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 Dresden and therefore Exelon responded appropriately to Item 9 in Enclosure 1 of the 50.54(f) letter.

ML16291A021 *via e-mail OFFICE NRR/JLD/JHMB/PM NRR/JLD/LA NRR/JLD/JHMB/BC(A)

NAME FVega SLent GBowman (BTitus for)

DATE 11/03/2016 10/18/2016 11/08/2016 OFFICE NRR/JLD/JHMB/PM NAME FVega DATE 11/08/2016