1 Diablo Canyon Independent Spent Fuel Storage Installation

1 Diablo Canyon Independent Spent Fuel Storage Installation (ISFSI) Dry Fuel Management Topics Jearl Strickland Interim Leader, Technical Services PG&E June 21, 2016

Topics • Status of Independent Spent Fuel Storage Installation (ISFSI) pad construction • Update on the long range fuel transfer to the ISFSI • Update of activities related to the potential for external corrosion of multi-purpose canisters (MPCs) in storage 2

ISFSI Facility Construction • Design capacity for the ISFSI is 138 HI-STORM casks. These arranged on 7 pads of 20 locations each • First two pads constructed 2005 -2007 • Beginning 2009, loaded casks placed on these pads • Five additional pads constructed in 2014 • Initial use in 2016 • No issues of note during construction 3

Completed ISFSI Storage Pads 4

Dry Fuel Storage Plan 2009 - 2025 • To maintain compliance with NRC requirements, four older fuel assemblies must surround each newer fuel assembly. • As there are 193 assemblies in the reactor core, 772 assemblies must be maintained in the spent fuel pool to accommodate the core offload. • DCPP strategy is to approach the 772 limit in 2016, and maintain at that level going forward. • Final state for the spent fuel pool is to be emptied approximately 10 years after final shutdown when the decay heat level has reached the allowable value for the cask license. 5

Dry Fuel Storage Statistics 6 Used Fuel Outage (UFO) History & Projections Start Finish Casks from Unit 1/2 UFO 1 6/11/2009 8/17/2009 8/0 UFO 2 5/3/2010 7/10/2010 0/8 UFO 3 1/16/2012 3/17/2012 3/4 UFO 4 8/5/2013 10/1/2013 3/3 UFO 5 5/25/2015 7/5/2015 5/3 UFO 6 8/8/2016 11/6/2016 6/6 UFO 7 6/4/2018 8/25/2018 4/5 UFO 8 5/18/2020 8/8/2020 4/4 UFO 9 8/1/2022 10/29/2022 4/4

Spent Fuel Locations 7 Unit 1 SFP : 972 assemblies

7 32 46 2 32 93 8 33 72 3 33 58 9 34 38 4 35 84 0 35 33 5 36 80 2 36 49 8 37 60 4 38 06 1 38 37 7 39 16 2 39 32 9 40 33 0 40 55 5 40 12 9 41 68 0 41 90 6 41 08 72 42 8 1 42 85 3 42 38 6 42 14 8 43 87 3 43 73 5 44 24 0 44 12 1 44 34 7 44 13 8 45 34 3 45 52 62 7 31 Assemblies in Spent Fuel Storage Pool Unit 1 SFP 1400 1200 1000 800 600 400 200 0 8

MPC Potential for External Corrosion Activities Primary mechanism for external corrosion is chlorideinduced stress corrosion cracking when canisters of susceptible material and tensile stresses reach an external temperature that facilitates a corrosive environment. Industry is collaborating with U. S. NRC on resolving this issue (ref. RIRP N-10 -01). 2015 EPRI. All Rights Reserved. 9

MPC Potential for External Corrosion Activities PG&E continues to actively support EPRI and NEI efforts on this issue. • April 28, 2016: NRC met with industry representatives and interested stakeholders to discuss closure of the chloride induced stress corrosion cracking Regulatory Issue Resolution Protocol (RIRP). • NEI and NRC expect formal closure of the RIRP within the next few weeks. • NEI, NRC, and EPRI representatives recapped milestones in improved understanding of the potential for stress corrosion cracking of welded stainless steel canisters. 10

MPC Potential for External Corrosion Activities EPRI Program Timeline 11

12 Thank You Jearl Strickland