Pacific Gas and Electric Company®

March 6, 2014

PG&E Letter DIL-14-003

Barry S. Allen Site Vice President

Diablo Canyon Power Plant Mail Code 104/6 P. 0. Box 56 Avila Beach, CA 93424

805.545.4888 Internal: 691.4888 Fax: 805.545.6445

ATTN: Document Control Desk 10 CFR 72.48 Director, Division of Spent Fuel Storage and Transportation Office of Nuclear Material Safety and Safeguards U.S. Nuclear Regulatory Commission Washington, DC 20555-0001

Materials License No. SNM-2511, Docket No. 72-26 Diablo Canyon Independent Spent Fuel Storage Installation 10 CFR 72.48 Report of Changes. Tests. and Experiments for March 1, 2012, to February 28, 2014

Dear Commissioners and Staff:

Pursuant to 10 CFR 72.48, "Changes, Tests, and Experiments," Pacific Gas and Electric Company (PG&E) is enclosing the 10 CFR 72.48 report for the Diablo Canyon Independent Spent Fuel Storage Installation (ISFSI), for March 1, 2012, through February 28, 2014. In accordance with 10 CFR 72.48(d)(2), the report provides a summary of all1 0 CFR 72.48 evaluations performed during this period.

Evaluations performed in accordance with 10 CFR 72.48 are performed as part of PG&E's licensing basis impact evaluation (LBIE) process. Because the LBIE process is used to perform reviews for compliance with regulations in addition to 10 CFR 72.48, some LBIEs do not include a 10 CFR 72.48 evaluation and are not included in this report.

The Plant Staff Review Committee has reviewed the LBIEs in the enclosure and has concurred that the changes do not require prior NRC approval and do not require change·s to the Diablo Canyon ISFSI Technical Specifications.

PG&E makes no regulatory commitments (as defined by NEI 99-04) in this letter.

If you have any questions regarding this submittal, please contact Mr. Thomas R. Baldwin, Regulatory Services Manager, at (805) 545-4720.

Sincerely,

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance

Callaway • Comanche Peak • Diablo Canyon • Palo Verde • Wolf Creek

Document Control Desk March 6, 2014 Page 2

WRLS/6980/64053230

Enclosure cc: Diablo Canyon Distribution cc/enc: Marc L. Dapas, NRC Region IV

John M. Goshen, NMSS Project Manager

PG&E Letter DIL-14-003

Thomas R. Hipschman, NRC Senior Resident Inspector

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance

Callaway • Comanche Peak • Diablo Canyon • Palo Verde • Wolf Creek

PG&E Letter DIL-14-003 Enclosure

Page 1 of 5

10 CFR 72.48 Report of Changes, Tests, and Experiments for

March 1, 2012, through February 28, 2014

Pacific Gas and Electric Company Diablo Canyon Independent Spent Fuel Storage Installation

Docket No. 72-26

LBIE 2013-020, Diablo Canyon ISFSI Campaign 4 Changes

PG&E Letter DIL-14-003 Enclosure

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Reference Document No. Design Change Package (DCP) 1000024951, Rev. 0 Reference Document Title: Diablo Canyon Independent Spent Fuel Storage

Installation (DCISFSI) Campaign 4 Changes

Activity Description This DCP proposed changes to the fourth campaign of the DCISFSI. This DCP incorporates two new safety analyses that demonstrate the loaded storage overpack, anchorage embedded support structure and ISFSI storage pad remain functional in the event of a partial loss of anchor stud pre-tension in a loaded storage overpack, and if the storage overpacks are loaded onto a storage pad using an alternate placement sequence than the original storage pad design. The partial loss of pre-tension analysis was requested in response to DCISFSI operating experience (OE) in order to have a documented analysis of the condition. The alternate placement sequence analysis is necessary to place in-service casks as far away from upcoming 2014 pad construction as possible for radiological (i.e. - ALARA) and security purposes.

The alternate analyses supplement the existing design bases storage pad analyses but use computer code SAP2000 nonlinear version 7.1 0 instead of ANSYS to model the physical configuration.

Summary of Evaluation The adverse elements from the licensing basis screen results from the introduction of an alternate analysis or method of evaluation to perform the structural analyses.

While the analyses assumed that the pre-tension was lost in the anchor studs to invoke the highest seismic demand, these analyses are not bases for removing the original design basis requirement to pre-tension the anchor studs. Dry fuel storage operations will continue to pre-tension the anchor studs using the same process as originally licensed.

The new analyses for partial loss of anchor stud pre-tension and storage pad seismic design cask placement sequencing use a modified methodology to that described in DCISFSI Final Safety Analysis Report Update (UFSAR) Section 8.2.1.2, "Earthquake Accident Analysis," in that these alternate non-linear analyses use computer code SAP2000 instead of ANSYS to model the configuration. SAP2000 and ANSYS are each commercially available and competitive finite-element analysis modeling software products. The use of SAP2000 to examine the non-linear seismic performance of the DCISFSI storage pad has been reviewed and approved by NRC in the original license application.

Review of the new analyses, also performed by the same entity and engineer as the original pad sliding analysis that used the Diablo Canyon ISFSI Long Period (ILP) earthquake spectra, finds that the guidance in NRC SFST-ISG-21 was followed. The new model was derived and carefully bench marked against the design basis model to ensure that the benchmark results were essentially the same (i.e. -within the margin of error). The benchmarking is documented in the DCP.

PG&E Letter DIL-14-003 Enclosure

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LBIE 2013-020, Diablo Canyon ISFSI Campaign 4 Changes Reference Document No. Design Change Package (DCP) 1000024951, Rev. 0 Reference Document Title: Diablo Canyon Independent Spent Fuel Storage

Installation (DCISFSI) Campaign 4 Changes Continued ...

The results of the partial loss of pre-tension analysis are used as input to the alternate cask placement sequence analysis.

The DCISFSI licensing bases require the use of the ILP seismic spectra for conditions such as the sliding of masses. Thus, these two new analyses are using the appropriate site-specific seismic input spectra to examine the realistic response and resultant stresses in the structures. A review of margin in the DCP from the calculations documents that all margins are the same as, or more conservative than the previous results.

Therefore, the new analyses for partial loss of anchor stud pre-tension and storage pad seismic design cask placement sequencing do not result in a departure from a method of evaluation described in the UFSAR used in establishing the design bases or in the safety analyses.

Based on results of the evaluation in LBIE 2013-020 and per the criteria in 10 CFR 72.48, the proposed change did not require prior NRC approval.

LBIE 2013-031, Diablo MPC Inspection Reference Document No. HPP-920-1

PG&E Letter DIL-14-003 Enclosure

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Reference Document Title: Diablo Canyon MPC Inspection for Salt Deposition

Activity Description This activity was a one-time field inspection of a portion of the exterior surfaces (shell and lid) of a loaded multipurpose canister (MPC) within a preselected storage overpack at the Diablo Canyon Independent Spent Fuel Storage Installation (DCISFSI). The inspection nondestructively collected surface temperature data, and any surface mineral deposits that were present during storage operations. The data collection tooling accessed the interior of the overpack to MPC gap through the temporary removal of one overpack lid outlet vent screen and gamma shield. This activity is not described in the DCISFSI Final Safety Analysis Report Update (UFSAR) and the performance of it adversely affects the thermal, shielding and structural design functions. This activity supported industry research needs that were not described or anticipated when the DCISFSI license application was originally submitted.

This inspection activity facilitates a Nuclear Energy Institute industry effort with the United States (U.S.) NRC under a Regulatory Issue Resolution Protocol N-10-01 that, in conjunction with an Electric Power Research Institute project, gathers industry field data from several ISFSI sites susceptible to potential chloride-induced stress corrosion cracking of MPCs as described in U.S.NRC Information Notice 2012-20.

Summary of Evaluation The adverse elements from the licensing basis screen results from the affected design functions and lack of description in the UFSAR.

The following questions were addressed in the evaluation. Questions 1 through 7 were answered "No." Question 8 was marked N/A as evaluation methodologies are not involved.

Q1: This activity does not result in more than a minimal increase in the frequency of occurrence of the Chapter 8 accidents because the activity is not a precursor to any of the events and the effects of the activity are bounded by analyses for normal operations.

02: This activity does not result in more than a minimal increase in the likelihood of occurrence of a malfunction of a system, structure, or component (SSC) important to safety previously evaluated in the UFSAR because all of the effects have been evaluated and determined to be negligible.

Q3: This activity does not result in more than a minimal increase in the consequences of an accident previously evaluated in the UFSAR because the activity is not an initiator of any accidents and the effects are bounded by the DCISFSI UFSAR analyses of record.

Continued ...

LBIE 2013-031, Diablo MPC Inspection Reference Document No. HPP-920-1

PG&E Letter DIL-14-003 Enclosure

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Reference Document Title: Diablo Canyon MPC Inspection for Salt Deposition Q4: This activity does not result in more than a minimal increase in the consequences of a malfunction of an SSC important to safety previously evaluated in the UFSAR because there are no malfunctions affected and no new malfunctions are introduced.

Q5: This activity does not create the possibility of an accident of a different type than any previously evaluated in the UFSAR because the MPC and overpack are able to exchange decay heat during the inspection such that no credible accident of a different type is created and the activity does not introduce equipment that could fail and initiate an accident.

Q6: This activity does not create a possibility for a malfunction of an SSC important to safety with a different result than any previously evaluated in the UFSAR because the activity does not introduce any changes to the storage system SSCs that are capable of causing a malfunction with a different result, the activity restores the configuration of the storage system to its original configuration such that no new malfunctions are introduced, and the activity is bounded by the DCISFSI UFSAR analyses of record.

Q7: This activity does not result in a design basis limit for a fission product barrier as described in the UFSAR being exceeded or altered because the effect on the overpack heat removal system performance during the short duration proposed activity is negligible, the peak cladding temperature and MPC pressure remain within limits and are bounded by the DCISFSI UFSAR analyses of record.

Based on results of the evaluation in LBIE 2013-020 and per the criteria in 1 0 CFR 72.48, the proposed change did not require prior NRC approval.