ML18211A322

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Staff Review of Spent Fuel Pool Evaluation Associated with Reevaluated Seismic Hazard Implementation Near-Term Task Force Recommendation 2.1: Seismic
ML18211A322
Person / Time
Site: Diablo Canyon  Pacific Gas & Electric icon.png
Issue date: 08/08/2018
From: Vega F G
Beyond-Design-Basis Management Branch
To: Welsch J M
Pacific Gas & Electric Co
Vega F G
References
EPID L-2017-JLD-0058
Download: ML18211A322 (15)
v • d • e


Text

UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Mr. James M. Welsch Vice President, Nuclear Generation and Chief Nuclear Officer Pacific Gas and Electric Company P.O. Box 56 Mail Code 104/6 Avila Beach, CA 93424 August 8, 2018

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NOS. 1 AND 2 -STAFF REVIEW OF SPENT FUEL POOL EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: SEISMIC (EPID L-2017-JLD-0058)

Dear Mr. Welsch:

The purpose of this letter is to inform Pacific Gas and Electric Company (PG&E, the licensee), of the results of the U.S. Nuclear Regulatory Commission (NRC) staff's review of the spent fuel pool (SFP) evaluation for Diablo Canyon Power Plant, Unit Nos. 1 and 2 (Diablo Canyon), 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. ML 12053A340) issued under Title 10 of the Code of Federal Regulations, 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 NRG-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 the 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) and the comparison portion of Item (4) of the 50.54(f) letter was provided by letter dated December 21, 2016 (ADAMS Accession No. ML 16341C057).

Enclosure 1, Item (9), of the 50.54(f) letter requested that, when the GMRS exceeds the SSE in the 1 to 10 Hertz frequency range, the licensee provide a seismic evaluation of the SFP. More specifically, licensees were asked to consider" ... all seismically induced failures that can lead to draining of the SFP."

J. Welsch By letter dated January 31, 2017 (ADAMS Accession No. ML 17031 A 171 ), the Nuclear Energy Institute (NEI) submitted the Electric Power Research Institute (EPRI) Report No. 3002009564 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. ML 12333A170).

The NRC endorsed the SFP Evaluation Guidance Report by letter dated February 28, 2017 (ADAMS Accession No. ML 17034A408), 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. ML 15194A015), the NRC staff stated that SFP evaluation submittals for sites with GMRS peak spectral accelerations above 0.8g were expected by December 31, 2017. By letter dated July 6, 2017 (ADAMS Accession No. ML 17177 A446), the NRC issued a generic audit plan and entered into the audit process described in Office Instruction LIC-111, "Regulatory Audits," dated December 29, 2008 (ADAMS Accession No. ML082900195), to assist in the timely and efficient closure of activities associated with the 50.54(f) letter. The Diablo Canyon site was included in the list of applicable licensees.

The staff used the audit process as described below during the SFP evaluation review. REVIEW OF LICENSEE SPENT FUEL POOL EVALUATION By letter dated December 18, 2017 (ADAMS Accession No. ML 17352A703), the licensee submitted its SFP evaluation for Diablo Canyon. 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 4.0 of the SFP Evaluation Guidance Report provides SFP evaluation criteria for plants with GMRS peak spectral accelerations greater than 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 4.0 also provides applicability criteria that enable licensees to determine if their specific conditions are within the bounds considered in developing some of the evaluation criteria in the guidance report. In its review, the staff confirmed that the SFP Evaluation Guidance Report methodology has been followed when calculating the site-specific seismic capacity of the SFP, and that Diablo Canyon's site-specific values and conditions are within the acceptable limits and bounds considered for the non-structural evaluation criteria specified in the SFP Evaluation Guidance Report. SPENT FUEL POOL STRUCTURAL EVALUATION Section 4.1 of the SFP Evaluation Guidance Report provides an SFP structural evaluation approach used to demonstrate that the SFP structure is sufficiently robust for the reevaluated seismic hazard. This approach supplements the guidance in Section 7 of the SPID and follows acceptable methods used to assess the seismic capacity of structures, systems, and components (SSCs) for nuclear power plants. In short, Sections 4.1.1 and 4.1.2 describe an acceptable method for licensees to use to calculate a site-specific seismic high confidence of J. Welsch low probability of failure (HCLPF) value for the SFP that is then compared to the site-specific GMRS. The licensee stated that the SFP structural evaluation approach presented in the SFP Evaluation Guidance Report is applicable and, as a part of the audit process, provided site-specific data to the NRC staff to confirm the stated results for Diablo Canyon. As a part of the audit process, the NRC staff reviewed the information provided in PG&E Calculation No. 128027-CA-229, "High Confidence Low Probability of Failure Capacity Evaluation of the Spent Fuel Pool," Revision 0, and confirmed that the site-specific HCLPF value calculated for Diablo Canyon's SFP followed the methodology of the SFP Evaluation Guidance Report and that the HCLPF value is greater than the GMRS. The staff concludes that SFP SSCs were appropriately evaluated and that the licensee has demonstrated that there is high confidence that the SFP structure is sufficiently robust to withstand ground motions with peak spectral accelerations up to and including the peak spectral acceleration of Diablo Canyon's GMRS. SPENT FUEL POOL NON-STRUCTURAL EVALUATION Section 4.2 of the SFP Evaluation Guidance Report provides criteria for evaluating the 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.

Additionally, page 4-11 of the SFP Evaluation Guidance Report provides a summary of the pertinent SFP non-structural parameters important to the methodology described in Section 4.2. The licensee provided a table in its letter dated December 18, 2017, demonstrating that it followed the SFP non-structural evaluation approach presented in the SFP Evaluation Guidance Report and provided site-specific data to confirm its applicability.

The staff reviewed the structural information provided, which included Diablo Canyon's site-specific attributes, against the criteria described in the SFP Evaluation Guidance Report, and confirmed that the methods and conclusions are applicable to the Diablo Canyon 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. Further, the staff concludes that the licensee demonstrated that a potential drain-down of the SFP as a result of the reevaluated seismic hazard is unlikely.

AUDIT REPORT The July 6, 2017, generic audit plan describes the NRC staffs intention to issue an audit report that summarizes and documents the NRC's regulatory audit of licensee's submittals associated with reevaluated seismic hazard analyses.

The NRC staffs Diablo Canyon audit was limited to the review of the calculation discussed above. An audit summary document is included as Enclosure 2 to this letter. CONCLUSION 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 Diablo Canyon and therefore, the licensee responded appropriately to Item (9) in Enclosure 1 of the 50.54(f) letter.

J. Welsch The NRC staff further concludes that the licensee has demonstrated an adequate margin to preclude a potential drain-down of the SFP as a result of the reevaluated seismic hazard at Diablo Canyon. If you have any questions, please contact me at (301) 415-1617 or via e-mail at Frankie.Vega@nrc.gov.

Docket Nos. 50-275 and 50-323

Enclosures:

1. Technical Review Checklist
2. NRC Staff Audit Summary cc w/encls: Distribution via Listserv Sincerely, Frant1:.~Manager Beyond-Design-Basis Management Branch Division of Licensing Projects Office of Nuclear Reactor Regulation TECHNICAL REVIEW CHECKLIST BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO SPENT FUEL POOL EVALUATIONS FOR HIGH GROUND MOTION RESPONSE SPECTRUM SITES IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION

2.1 SEISMIC

DIABLO CANYON POWER PLANT, UNIT NOS. 1 AND 2 DOCKET NOS. 50-275 AND 50-323 BACKGROUND By letter dated March 12, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12053A340), 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, under Title 10 of the Code of Federal Regulations (10 CFR), Section 50.54(f) (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 10 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 January 31, 2017 (ADAMS Accession No. ML 17031A 171 ), the Nuclear Energy Institute (NEI) submitted the Electric Power Research Institute (EPRI) Report No. 3002009564 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. The NRC endorsed the SFP Evaluation Guidance Report by letter dated February 28, 2017 (ADAMS Accession No. ML 17034A408), 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 December 18, 2017(ADAMS Accession No. ML 17352A703), Pacific Gas and Electric Company (PG&E, the licensee), provided an SFP report in response to Enclosure 1, Item (9), of the 50.54(f) letter for Diablo Canyon Power Plant, Unit Nos. 1 and 2 (Diablo Canyon). 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. The NRC staff evaluated whether the SFP Evaluation Guidance Report methodology had been followed when calculating the site-specific seismic capacity of the SFP, and that Diablo Canyon's site-specific values and conditions are within the acceptable limits and bounds considered for the structural evaluation criteria specified in the SFP Evaluation Guidance Report. The NRC staff also 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 efficiency.

The application of this staff review is limited to the SFP evaluation as part of the seismic review as part of the Near-Term Task Force (NTTF) Recommendation

2.1. Enclosure

1 NTTF Recommendation

2.1 Spent

Fuel Pool Evaluations Technical Review Checklist for Diablo Canyon Power Plant, Units 1 and 2 Site Parameters:

I. Site-Specific GMRS The licensee:

  • Used the site-specific GMRS hazard, consistent with the information in the Seismic Hazard and Screening Report (SHSR) or its update, that was evaluated and accepted in the NRC staff assessment when calculating the SFP high confidence of low probability of failure (HCLPF) value. Notes from the reviewer:

Yes 1. The NRC staff reviewed the PG&E Calculation No. 128027 -CA-229, "High Confidence Low Probability of Failure Capacity Evaluation of the Spent Fuel Pool," Revision 0, as a part of the audit process for Diablo Canyon. The staff notes that the calculation derives seismic input values for the Auxiliary Building that were ultimately generated by the NRG-accepted GMRS. See conclusion below for details. Deviation(s}

or Deficiency(ies}, and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

  • The licensee's derivation of the SFP In-Structure Response Spectra (ISRS) using the probabilistic soil-structure interaction (SSI) analysis of Auxiliary Building and seismic input values from the GMRS is reasonable for the purposes of this calculation.

Structural Parameters:

II. Seismic Design of the SFP Structure The licensee:

  • Performed site-specific calculations to demonstrate that the limiting SFP HCLPF capacity value is greater than the peak spectral acceleration of the site-specific GMRS. Notes from the reviewer:

Yes 1. The staff noted that the limiting SFP HCLPF was compared to the damped spectral acceleration at 5 Hz from the site-specific GMRS. According to the SFP evaluation guidance, licensees should compare the site-specific GMRS with the limiting SFP HCLPF in the frequency range-of-interest (e.g., 10-20 Hz). Since it appears that the GMRS was evaluated against the HCLPF at 5 Hz, the staff asked the licensee, as part of the audit process to clarify how the HCLPF vs GMRS comparison at 5 Hz was acceptable for Diablo Canyon. 2. The licensee stated that all fragility evaluations, including those associated HCLPF capacity determinations, performed in support of the Diablo Canyon Power Plant (DCPP) Seismic Probabilistic Risk Assessment Update are anchored at 5 Hz. For consistency, the HCLPF capacity determination for the SFP was also performed at 5 Hz. The licensee also stated that the ratio between the HCLPF and the GMRS spectral acceleration at any specific frequency (5 Hz or at the frequency interest described in the SFP evaluation guidance) would be the same. 3. The staff reviewed the licensees' response and agrees that the HCLPF can be defined at any specific frequency as long as the Strength Factor (Fs), used to calculate the HCLPF (HCLPFFreq=

FS x SAFreq) value, is over one. This would result in a HCLPF value greater than the site-specific GMRS. 4. The NRC staff confirmed that the licensee followed the methodology described in the SFP Evaluation Guidance Report in PG&E Calculation No. 128027-CA-229, "High Confidence Low Probability of Failure Capacity Evaluation of the Spent Fuel Pool," Revision 0, to calculate an SFP HCLPF capacity.

The resulting HCLPF value is greater than the site-specific GMRS; therefore, it is reasonable to conclude that the SFP has sufficient capacity to withstand a seismic event at least up to the GMRS without failure that would lead to a rapid drain-down.

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

No deviations or deficiencies were identified.

The NRC staff concludes that:

  • The SFP has sufficient capacity to withstand a seismic event at least up to the GMRS without failure that would lead to a rapid drain-down.

Ill. 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 Program performed in accordance with Maintenance Rule ( 10 CFR 50.65). Notes from the reviewer:

Yes 1. The licensee stated that the Auxiliary Builing, which houses the SFPs, is included in the Diablo Canyon Civil Inspection Program and referenced PG&E Departmental Administrative Procedure No. MA 1.NE1, "Maintenance Rule Monitoring Civil Implementation," Revision 6. 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 performed in accordance with Maintenance Rule (10 CFR 50.65). Non-Structural Parameters:

IV. Applicability of Piping Evaluation The licensee:

  • Stated that there are no piping penetrations attached to the SFP more than 6 feet (ft.) below the surface of the water and cited PG&E drawings (102013, 108013, 500086, 500129, 500936 and 501002). Notes from the reviewer:

Yes 1. The Licensee referenced the drawings mentioned above that included the elevations of the penetrations for the piping attached to the SFPs and stated that no penetrations are located more than 6 ft. below the water surface. Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

  • There are no piping penetrations attached to the SFP more than 6 ft. below the surface of the water. V. Ductile Behavior of SFP Gates The licensee:
  • Stated that the SFP gate is constructed from a ductile material (e.g. aluminum or stainless steel alloys). Notes from the reviewer:

Yes 1. SFP gates are constructed from stainless steel (ASTM A240, Type 304), according to PG&E Drawing 439501. This is consistent with the materials specified in the SFP Evaluation Guidance Report to ensure ductile behavior of the gates. Deviation(s) or Deficiency(ies), and Resolution:

No deviations or defioiencies were identified.

The NRC staff concludes that:

  • The SFP gates are constructed from a material expected to exhibit ductile behavior under higher seismic demands. VI. Siphoning Evaluation The licensee:
  • Stated that anti-siphoning devices are installed on piping systems 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 performed to determine the seismic adequacy of the piping is provided.
  • Stated that the piping of the SFP cooling system cannot lead to rapid drain-down due to siphoning.
  • Stated that no anti-siphoning devices are attached to 2" or smaller piping with extremely large extended operators.
  • Provided a seismic adequacy evaluation, in accordance with NP-6041, for cases where active siphoning devices are attached to 2" or smaller piping with extremely large extended operators. Yes N/A Yes Yes N/A Notes from the reviewer:
1. The licensee stated that anti-siphoning*holes are present in SFP-attached piping that could lead to siphoning of water. The staff verified that the Updated Final Safety Analysis Report (UFSAR) supports this statement (UFSAR Section 9.1.3.3).

The licensee also stated that, as part of Fukushima NTTF Recommendation

2.3 seismic

walkdowns (ADAMS Accession Nos. ML 12333A268 and ML 12333A266), the licensee visually verified the presence of these anti-siphon holes. 2. The licensee confirmed, via the audit process, that active anti-siphoning devices are not used at Diablo Canyon. Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

  • Anti-siphoning devices exist in applicable piping systems that could lead to siphoning water from the SFP.
  • Piping of the SFP cooling system is not likely to lead to rapid down due to siphoning.
  • No active anti-siphoning devices are attached to 2" or smaller piping with extremely large extended operators.

VII. Sloshing Evaluation The licensee:

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

Yes Yes Yes Yes Yes 1. SFPs dimensions (UFSAR Figure 9.1-2 and PG&E Calculation No. 128027-CA-229)

-SFP Length -37 ft. 3 in. -SFP Width -35 ft. -SFP Depth -41 ft. Deviation(s) or Deficiency(ies), and Resolution:

No deviations or deficiencies were identified.

The NRC staff concludes that:

  • SFP dimensions are bounded by the dimensions specified in the report (i.e., SFP length and width <125 ft.; SFP depth >36 ft.). VIII. Evaporation Evaluation The licensee:
  • Provided the surface area of the plant's SFP .
  • Stated that the surface area of the plant's SFP is greater than 500 ft 2
  • Provided the licensed reactor core thermal power .
  • Stated that the reactor core thermal power is less than 4,000 megawatt thermal (MW,) per unit. Notes from the reviewer:
1. Surface area of pools = 1,300 ft 2 (UFSAR Figure 9.1-2) 2. Reactor thermal power= 3,411 MW, (UFSAR Section 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.
  • The reactor core thermal power is less than 4,000 MW, per unit.

Conclusions:

Yes Yes Yes Yes Yes Yes Yes The NRC staff reviewed the licensee's SFP evaluation report. Based on its review, the NRC staff concludes that the SFP Evaluation Guidance Report methodology has been followed when calculating the site-specific seismic capacity of the SFP, and that Diablo Canyon's site-specific values and conditions are within the acceptable limits and bounds considered for the structural evaluation criteria specified in the SFP Evaluation Guidance Report. Therefore, the licensee responded appropriately to Item (9) in Enclosure 1 of the 50.54(f) letter. The NRC staff further concludes that the licensee has demonstrated an adequate margin to preclude a potential drain-down of the SFP as a result of the reevalutaed seismic hazard at Diablo Canyon.

AUDIT

SUMMARY

BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO DIABLO CANYON POWER PLANT, UNIT NOS. 1 AND 2 SPENT FUEL POOL EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: SEISMIC (EPID NO. L-2017-JLD-0058)

BACKGROUND AND AUDIT BASIS By letter dated March 12, 2012 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 12053A340), the U.S. Nuclear Regulatory Commission (NRC) issued a request for information under Title 1 O of the Code of Federal Regulations (1 O CFR), Section 50.54(f) (hereafter referred to as the 50.54(f) letter). Enclosure 1 to the 50.54(f) letter requested that licensees reevaluate the seismic hazards for their sites using present-day methods and regulatory guidance used by the NRC staff when reviewing applications for early site permits and combined licenses.

By letter dated October 27, 2015 {ADAMS Accession No. ML 15194A015), the NRC made a determination of which licensees were to perform: (1) a seismic probabilistic risk assessment (SPRA), (2) limited scope evaluations, or (3) no further actions based on a comparison of the reevaluated seismic hazard and the site's design-basis earthquake. (Note: Some plant-specific changes regarding whether an SPRA was needed or limited scope evaluations were needed at certain sites have occurred since the issuance of the October 27, 2015, letter.) By letter dated July 6, 2017 (ADAMS Accession No. ML 17177 A446), the NRC issued a generic audit plan and entered into the audit process described in Office Instruction LIC-111, "Regulatory Audits," dated December 29, 2008 (ADAMS Accession No. ML082900195), to assist in the timely and efficient closure of activities associated with the 50.54(f) letter. Diablo Canyon Power Plant, Unit Nos. 1 and 2 (Diablo Canyon) was included in the list of applicable licensees.

REGULATORY AUDIT SCOPE AND METHODOLOGY The areas of focus for the regulatory audit are the information contained in the spent fuel pool (SFP) evaluation submittal and all associated and relevant supporting documentation used in the development of the SFP evaluation including, but not limited to, methodology, process information, calculations, computer models, etc. AUDIT ACTIVITIES The Diablo Canyon audit took place at the NRC Headquarters in Rockville, MD, beginning on June 22, 2018. Personnel from Pacific Gas and Electric Company (PG&E, the licensee) participated remotely, via e-mail, from their respective offices. A list of the licensee staff and NRC staff that participated in the audit is contained in Table 1. Enclosure 2

Table 1 NRC Staff Licensee Staff Name I Title Name I Title Frankie VeQa I Project ManaQer Michael Richardson I Sr. LicensinQ EnQineer On June 22, 2018, the NRC staff requested, via e-mail, that the licensee upload PG&E Calculation No. 128027-CA-229, "High Confidence Low Probability of Failure Capacity Evaluation of the Spent Fuel Pool," Revision 0, which was the calculation that was performed to determine the high confidence low probability of failure (HCLPF) value for the SFP onto the licensee's ePortal (electronic reading room). In addition, the staff requested a series of plant drawings and procedures (detailed.below) that were referenced as part of the SFP submittal.

The licensee uploaded the requested documents onto the ePortal on June 28, 2018, as requested by the NRC staff. DOCUMENTS AUDITED

  • PG&E Departmental Administrative Procedure No. MA 1.NE1, "Maintenance Rule Monitoring Program-Civil Implementation," Revision 6;
  • PG&E Drawing No. 102013, Sheet 2, "Unit 1 -Spent Fuel Pit Cooling System," Revision 45;
  • PG&E Drawing No. 108013, Sheet 2, "Unit 2-Spent Fuel Pit Cooling System," Revision 36 PG&E Design Criteria Memorandum No. S-13, "Spent Fuel Pool Cooling System," Revision 31 ;
  • PG&E Drawing No. 500086, "Unit 1 -Mechanical, Area J & L, Plan at El. 115'-O"," Revision 16;
  • PG&E Drawing No. 500129, "Unit 1-Drainage & Fire Fighting-Auxiliary Bldg. Area J, Plan at El. 115'-0"," Revision 12;
  • PG&E Drawing No. 500936, "Unit 2-Piping and Mechanical, Area J & L, Plan at El. 115'-0"," Revision 9;
  • PG&E Drawing No. 501002, "Unit 2-Civil Drainage and Fire Fighting, Area J, Auxiliary Building, Plan at Elevation 115'-0"," Revision 7;
  • PG&E Drawing No. 439504, "Unit 1 & 2 -Civil Spent Fuel Pool Gate Details, Auxiliary Building-Area J," Revision 10;
  • PG&E Drawing No. 439501, "Unit 1 -Civil Plan & Details, Spent Fuel Pool Liner, Auxiliary Building-Area J," Revision 13;
  • PG&E Drawing No. 439533, "Unit 2-Civil Concrete Outline, Aux. Building, Elev. Area J, GW & GE," Revision 10;
  • PG&E Drawing No. 443490, "Units 1 & 2 -Concrete Outline, Section F3 -F3 & F4-F4, Auxiliary Building-Areas J & GE," Revision 8. OPEN ITEMS AND REQUEST FOR INFORMATION Following the review of the SFP HCLPF calculation, there were no open items identified by the NRC staff that required proposed closure paths, and there were no requests for information discussed or planned to be issued. DEVIATIONS FROM AUDIT PLAN There were no deviations from the July 6, 2017, generic audit plan.

AUDIT CONCLUSION The issuance of this document, containing the staff's review of the SFP evaluation submittal, concludes the SFP audit process for Diablo Canyon.

J. Welsch

SUBJECT:

DIABLO CANYON POWER PLANT, UNIT NOS. 1 AND 2 -STAFF REVIEW OF SPENT FUEL POOL EVALUATION ASSOCIATED WITH REEVALUATED SEISMIC HAZARD IMPLEMENTING NEAR-TERM TASK FORCE RECOMMENDATION 2.1: SEISMIC DATED August 8, 2018 DISTRIBUTION:

PUBLIC RidsNrrDlpPbmbResource RidsNrrDorlLpl4Resource RidsNrrLASLent Resource RidsACRS_MailCTR Resource PBMB R/F BTitus, NRR RidsNrrPMDiabloCanyonResource FVega, NRR RidsRgn4MailCenter Resource ADAMS Accession No.: ML 18211 A322

  • via e-mail OFFICE NRR/OLP/PBMB/PM NRR/OLP/PBMB/LA NRR/OLP/PBMB/BC (A) NAME FVega SLent BTitus DATE 08/07/2018 07/30/2018 08/07/2018 OFFICE NRR/OLP/PBMB/PM NAME FVega DATE 08/08/2018 OFFICIAL RECORD COPY
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