Text

Post-Shutdown Decommissioning Activities Report, Revision 1
	ML22293A419
Person / Time
Site:	Diablo Canyon
Issue date:	10/12/2022
From:	Zawalick M; Pacific Gas & Electric Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	DCL-22-042
	Download: ML22293A419 (49)
	v • d • e

Pacific Gas and

Electrtc Campany Maureen R. Zawalick Diablo Canyon Power Plant Vice President Mail code 104/6/608 Decomnissioning and P.O. Box 56 Technical Services Avila Beach, CA 93424

805.545.4242 Internal: 691.4242

PG&E Letter DCL-22-042

U.S. Nuclear Regulatory Commission 10 CFR 50.82(a)(4)

ATTN: Document Control Desk Washington, DC 20555-0001

Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 and 2 Diablo Canyon Power Plant, Units 1 and 2 - Post-Shutdown Decommissioning Activities Report, Revision 1

Reference:

1. PG&E Letter DCL-19-077, Diablo Canyon Power Plant, Units 1 and 2 - Post-Shutdown Decommissioning Activities Report, dated December 4, 2019 (ML19338F173)

2. PG&E Letter DCL-21-073, Notification of Changes to Post-Shutdown Decommissioning Activities Report, Site-Specific Decommissioning Cost Estimate, and Irradiated Fuel Management Plan for Diablo Canyon Power Plant, Units 1 and 2, dated October 19, 2021 (ML21293A120)

Dear Commissioners and Staff:

In Reference 1, Pacific Gas and Electric Company (PG&E) submitted Revision 0 of the Post-Shutdown Decommissioning Activities Report (PSDAR) for Diablo Canyon Power Plant (DCPP) Units 1 and 2. In Reference 1, PG&E agreed to submit an updated PSDAR to the NRC within six months following submittal of the Nuclear Decommissioning Cost Triennial Proceedings (NDCTP) to the California Public Utilities Commission (CPUC), which is on a nominal three-year frequency. The 2021 NDCTP was submitted to the CPUC on December 14, 2021. In addition, in Reference 2, PG&E notified the NRC of significant changes to the decommissioning plans for DCPP Units 1 and 2, which impact the information provided in Reference 1.

The purpose of this submittal is to provide Revision 1 of the PSDAR for DCPP Units 1 and 2. The updated PSDAR reflects PG&E's current plans for decommissioning; however, the plans may change as DCPP Units 1 and 2 progress closer to permanent cessation of operations. As required by 10 CFR 50.82(a)(7), PG&E will notify the NRC in writing, with copies sent to the State of California, before performing any decommissioning activity inconsistent with, or making any significant schedule change from, those actions and schedules described in the PSDAR, including changes that significantly increase the decommissioning cost.

A member of the STARS Alliance Callaway Diablo Canyon Palo Verde Wolf Creek Document Control Desk PG&E Letter DCL-22-042 Page 2

The enclosure contains the PSDAR, Revision 1, for DCPP Unit 1 and Unit 2.

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

Should you have any questions, please contact Mr. Philippe Soenen at (805)459-3701.

Sincerely,

Maureen R. Zawalick ___________________

Vice President, Decommissioning and Technical Services Date

Enclosure cc: Diablo Distribution cc/enc: Mahdi O. Hayes, NRC Senior Resident Inspector Samson S. Lee, NRC Senior Project Manager Scott A. Morris, NRC Region IV Administrator Gonzalo L. Perez, California Department of Health Services

A member of the STARS Alliance Callaway Diablo Canyon Palo Verde Wolf Creek Enclosure PG&E Letter DCL-22-042 Post-Shutdown Decommissioning Activities Report, Revision 1 Diablo Canyon Power Plant Unit 1 and Unit 2

Enclosure PG&E Letter DCL-22-042

POST-SHUTDOWN DECOMMISSIONING ACTIVITIES REPORT DIABLO CANYON POWER PLANT Unit 1 and Unit 2

Revision 1

August 2022 Pacific Gas and Electric Company Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

Table of Contents Table of Contents............................................................................................................. i Acronyms........................................................................................................................ iii

1. Introduction and Summary........................................................................................ 5 1.1. Introduction..................................................................................................... 5 1.2. Background..................................................................................................... 6 1.3. Summary of Decommissioning Alternatives.................................................... 7

2. Description of Planned Decommissioning Activities................................................. 9 2.1. Phase 1 - Pre-Shutdown Planning............................................................... 10 2.2. Phase 2 - Zirc Fire........................................................................................ 11 2.3. Phase 3 - Wet Storage................................................................................. 13 2.4. Phase 4 - Building Demolition...................................................................... 14 2.5. Phase 5 - Non-Independent Spent Fuel Storage Installation Site Restoration 14 2.6. Phase 6 - Independent Spent Fuel Storage Installation Operations............ 14 2.7. Phase 7 - Spent Nuclear Fuel and Greater Than Class C Storage Demolition and Restoration.......................................................................................................... 14 2.8. General Decommissioning Considerations................................................... 15 2.8.1. Site Characterization..................................................................................... 15 2.8.2. Groundwater Protection................................................................................ 17 2.8.3. Radioactive Waste Management.................................................................. 17 2.8.4. Removal of Mixed Wastes............................................................................ 18 2.8.5. Changes to Management and Staffing.......................................................... 18 2.8.6. Diablo Canyon Decommissioning Engagement Panel.................................. 19

3. Schedule of Planned Decommissioning Activities.................................................. 19

4. Estimate of Expected Decommissioning Costs and Associated Funding............... 20

5. Environmental Impacts........................................................................................... 23 5.1. Environmental Impacts of Decommissioning................................................ 24 5.1.1. Onsite and Offsite Land Use......................................................................... 24 5.1.2. Water Use..................................................................................................... 25 5.1.3. Water Quality................................................................................................ 25

Page i of iv Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 5.1.4. Air Quality..................................................................................................... 27 5.1.5. Aquatic Ecology............................................................................................ 27 5.1.6. Terrestrial Ecology........................................................................................ 28 5.1.7. Threatened and Endangered Species.......................................................... 29 5.1.8. Radiological.................................................................................................. 32 5.1.9. Radiological Accidents.................................................................................. 33 5.1.10. Occupational Issues...................................................................................... 34 5.1.11. Cost.............................................................................................................. 35 5.1.12. Socioeconomics............................................................................................ 35 5.1.13. Environmental Justice................................................................................... 35 5.1.14. Cultural, Historical, and Archaeological Resources...................................... 36 5.1.15. Aesthetic Issues............................................................................................ 40 5.1.16. Noise............................................................................................................. 40 5.1.17. Transportation............................................................................................... 41 5.1.18. Irreversible and Irretrievable Commitment of Resources.............................. 42 5.2. Environmental Impacts of License Termination - NUREG-1496.................. 42 5.3. Discussion of Decommissioning in the Final Environmental Statement........ 43 5.4. Additional Considerations............................................................................. 43 5.5. Conclusion.................................................................................................... 43

6. References............................................................................................................. 44

List of Figures None

List of Tables Table 2-1 DCPP Decommissioning Phases Summary

Table 4-1 Cost Summary from DCPP Site-Specific DCE

Table 5-1 Threatened and Endangered Species Identified Within the Vicinity of DCPP

Table 5-2 Known Cultural Resources Within the DCPP Operational Area

Page ii of iv Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Acronyms ALARA as low as reasonably achievable

BMP best management practices

C&DP cold and dark power

CARB California Air Resources Board

CEQA California Environmental Quality Act

CFR Code of Federal Regulations

CPUC California Public Utilities Commission

D&D decontaminate and dismantle

DC Diablo Canyon

DCPP Diablo Canyon Power Plant

DOE Department of Energy

EPA Environmental Protection Agency

ER environmental report

FES Final Environmental Statement

GEIS Generic Environmental Impact Statement

GTCC Greater Than Class C

HEPA high-efficiency particulate air

HSA historical site assessment

IFMP Irradiated Fuel Management Plan

ISFSI independent spent fuel storage installation

LARW low-activity radioactive waste

LTP License Termination Plan

MARSSIM Multi-Agency Radiation Survey and Site Investigation Manual

NDT nuclear decommissioning trust

Page iii of iv Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 NEPA National Environmental Policy Act

NRC Nuclear Regulatory Commission

OSHA Occupational Safety and Health Administration

PG&E Pacific Gas and Electric Company

PSDAR Post-Shutdown Decommissioning Activities Report

PWR pressurized water reactor

SFP spent fuel pool

SHPO State Historic Preservation Officers

SNF spent nuclear fuel

SSC systems, structures, and components

SSDCE site-specific decommissioning cost estimate

Page iv of iv Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

1. Introduction and Summary

1.1. Introduction In accordance with the requirements of 10 CFR 50.82(a)(4)(i), Termination of license, this report constitutes the Post-Shutdown Decommissioning Activities Report (PSDAR) for the Diablo Canyon Power Plant (DCPP). This PSDAR contains the following:

1. a description of the planned decommissioning activities along with a schedule for their accomplishment

2. a discussion that provides the reasons for concluding that the environmental impacts associated with site-specific decommissioning activities will be bounded by appropriate, previously issued environmental impact statements, except cultural, historical, and archaeological resources

As Pacific Gas and Electric Company (PG&E) is currently in the planning phase, decommissioning plans continue to evolve. In accordance with 10 CFR 50.82(a)(4)(i), as more detailed plans are developed, PG&E will verify that decommissioning activities that impact cultural, historical, and archaeological resources are bounded by previously issued environmental impact statements or seek appropriate regulatory approval if needed.

3. a summary of the site-specific decommissioning cost estimate (SSDCE) that is being submitted concurrently, including the projected cost of managing irradiated fuel and the post-decommissioning site restoration cost

The PSDAR has been developed consistent with Regulatory Guide 1.185, Standard Format and Content for Post-Shutdown Decommissioning Activities Report, (Reference 1). This report is based on currently available information and the plans discussed herein may be modified as additional information becomes available or conditions change. As required by 10 CFR 50.82(a)(7), PG&E will notify the Nuclear Regulatory Commission (NRC or Commission) in writing, with copies sent to the State of California, before performing any decommissioning activity inconsistent with, or making any significant schedule change from, those actions and schedules described in the PSDAR, including changes that significantly increase the decommissioning cost. In addition, PG&E will submit an updated PSDAR to the NRC for its review within six months following submittal of the Nuclear Decommissioning Cost Triennial Proceedings filing to the California Public Utilities Commission (CPUC), which is on a nominal three-year frequency. PG&E will provide the periodic updates to the PSDAR until 10 CFR 50 license termination.

The Irradiated Fuel Management Plan (IFMP), Revision 1, and SSDCE, Revision 1, are being submitted concurrently with the PSDAR, Revision 1. The technical, schedule, and cost information provided is consistent among these submittals.

Page 5 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

1.2. Background The two-unit DCPP consists of a pair of Westinghouse four loop pressurized water reactors (PWRs). At full capacity, Unit 1 and Unit 2 each has a thermal rating of 3,411 megawatt thermal, with corresponding gross electrical outputs of 1,190 megawatt electrical. The current facility operating licenses for DCPP expire on November 2, 2024, for Unit 1 and August 26, 2025, for Unit 2.

The DCPP site is adjacent to the Pacific Ocean in San Luis Obispo County, California, and is approximately 12 miles west-southwest of the city of San Luis Obispo. The residential community of Los Osos is approximately 8 miles north of the site. This community is in a coastal hillside area adjacent to Montana de Oro State Park. The township of Avila Beach is located down the coast at approximately 7 miles southeast of the site. The city of Morro Bay is located up the coast approximately 11 miles northwest of the site. The plant is roughly equidistant between San Francisco and Los Angeles.

The principal structures of DCPP include two containment structures, turbine building, auxiliary building, radwaste buildings, administration building, training building, maintenance building, storage tanks, intake and discharge structures, and transmission switchyards. An independent spent fuel storage installation (ISFSI) is also located at DCPP that has capacity for all spent nuclear fuel (SNF) generated through the end of the operating licenses. The Diablo Canyon (DC) ISFSI is licensed under a Part 72 site-specific license.

A brief history of the major milestones related to DCPP construction and operational history is as follows:

Unit 1 Unit 2 Construction Permit Issued April 23, 1968 December 9, 1970 Full Power - Operating License Issued November 2, 1984 August 26, 1985 Commercial Operation May 7, 1985 March 13, 1986 Operating License Expiration November 2, 2024 August 26, 2025

By letter dated November 27, 2018 (Reference 2), PG&E provided formal notification to the NRC that it intends to permanently cease power operations of DCPP on November 2, 2024, for Unit 1 and August 26, 2025, for Unit 2. Once each DCPP unit has permanently ceased operation and fuel has been permanently removed from the reactor vessel, PG&E will submit written certifications to the NRC, in accordance with 10 CFR 50.82(a)(1)(ii) and 10 CFR 50.4(b)(8) and (9). Upon docketing of the certifications required by 10 CFR 50.82(a)(1)(i) and 10 CFR 50.82(a)(1)(ii), pursuant to 10 CFR 50.82(a)(2), the 10 CFR Part 50 licenses for DCPP will no longer authorize operation of the reactors or emplacement or retention of fuel in the reactor vessels.

Page 6 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Pursuant to 10 CFR 50.51(b), "Continuation of license," the license for a facility that has permanently ceased operations continues in effect beyond the expiration date to authorize ownership and possession of the utilization facility until the Commission notifies the licensee in writing that the license has been terminated.

During the period that the license remains in effect, 10 CFR 50.51(b) requires that PG&E:

1. Take actions necessary to decommission and decontaminate the facility and continue to maintain the facility including storage, control, and maintenance of the SNF in a safe condition.

2. Conduct activities in accordance with all other restrictions applicable to the facility in accordance with NRC regulations and the 10 CFR 50 facility license.

10 CFR 50.82(a)(9) states that power reactor licensees must submit an application for termination of the license and that the application must be accompanied or preceded by a license termination plan (LTP) to be submitted for NRC approval.

1.3. Summary of Decommissioning Alternatives The NRC has evaluated the environmental impacts of three general strategies for decommissioning power reactor facilities in NUREG-0586, Final Generic Environmental Impact Statement (GEIS) on Decommissioning of Nuclear Facilities:

Supplement 1, Regarding the Decommissioning of Nuclear Power Reactors (Reference 3). The three general methods evaluated are summarized as follows:

DECON: The systems, structures, and components (SSCs) that contain radioactive contaminants are promptly removed or decontaminated to a level that permits termination of the 10 CFR 50 license shortly after cessation of operations.

SAFSTOR: After the plant is shut down and defueled, the facility is placed in a safe, stable condition and maintained in that state (safe storage). The facility is decontaminated and dismantled at the end of the storage period to levels that permit 10 CFR 50 license termination. During SAFSTOR, a facility is left intact, or may be partially dismantled, but the SNF is removed from the reactor vessel, and radioactive liquids are drained from systems and components and then processed. Radioactive decay occurs during the SAFSTOR period, thereby reducing the quantity of contamination and radioactivity that must be disposed of during decontamination and dismantlement.

ENTOMB: Radioactive SSCs are encased in a structurally long-lived substance, such as concrete. The entombed structure is appropriately maintained, and continued surveillance is carried out until the radioactivity decays to a level that permits termination of the 10 CFR 50 license.

Page 7 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

The decommissioning approach that has been selected by PG&E for DCPP is the DECON method. While some decommissioning activities would begin after the Unit 1 shutdown, the majority of decommissioning activities at the two units would begin soon after the Unit 2 shutdown and are sequenced and integrated to minimize the total cost and duration of the physical dismantling processes. DCPP decommissioning includes: permanent removal of fuel from the reactors; transfer SNF to the DC ISFSI; decontaminate and dismantle (D&D) SSCs to levels that permit license termination; and restore non-DC ISFSI site areas. In accordance with 10 CFR 50.82(a)(9), a LTP will be developed and submitted for NRC approval at least two years prior to termination of the licenses. 10 CFR 50 license termination is targeted for approximately 9.7 years after Unit 2 shutdown. After SNF and greater than Class C (GTCC) waste are transferred to the Department of Energy (DOE) for storage at a permanent offsite repository, the DC ISFSI will be decommissioned in accordance with 10 CFR 72, and the site restored (including biological monitoring),

within an additional 9 years.

The decision to transition to immediate DECON is consistent with the CPUC and stakeholder preference and is also in the best interest of PG&Es customers because the total cost of decommissioning can be reduced by direct transition to decommissioning immediately upon plant shutdown. PG&E determined that immediate transition to decommissioning is more cost-effective than the SAFSTOR strategy based on the following considerations: (1) the operating licenses are terminated earlier; (2) earlier security staff and emergency plan reductions due to security modifications and earlier transfer of SNF to the DC ISFSI; (3) benchmarking experience of other plants supports more efficient resolution of technical challenges; and (4) availability of experienced, in-house staff.

Typically, initial planning efforts detailing the decommissioning process can take 18 to 24 months after reactor shutdown before physical decommissioning begins. To support a direct transition to immediate DECON, PG&E plans to leverage the CPUCs early approval of DCPP shutdown in 2024 and 2025 to continue decommissioning planning and permitting activities from 2019 to 2024 (see Section 2.1 below). The planning would streamline the decommissioning effort, reduce decommissioning costs, and accelerate the schedule by allowing portions of physical decommissioning to begin shortly after permanent shutdown of each unit.

This also would shorten the overall decommissioning schedule. Industry experience indicates that early, detailed preparation and planning reduces the duration and cost of decommissioning while enhancing safety and efficiency (References 4 and 5).

The decommissioning approach for DCPP is described in the following sections:

Section 2.0 describes the planned decommissioning activities and the general timing of their implementation.

Section 3.0 describes the overall decommissioning schedule, including the SNF management and site restoration activities.

Page 8 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

Section 4.0 summarizes the cost estimating methodology and references the SSDCE, Revision 1, being submitted concurrently.

Section 5.0 describes the basis for concluding that the environmental impacts associated with decommissioning DCPP are bounded by the NRC GEIS related to decommissioning, except for cultural, historical, and archaeological resources. As PG&E is currently in the planning phase, decommissioning plans continue to evolve. In accordance with 10 CFR 50.82(a)(4)(i), as more detailed plans are developed, PG&E will verify that decommissioning activities that impact cultural, historical, and archaeological resources are bounded by previously issued environmental impact statements or seek appropriate regulatory approval if needed.

Section 6.0 provides a list of references.

2. Description of Planned Decommissioning Activities DCPP expects to conduct decommissioning of DCPP in the following phases presented in Table 2-1. The SSDCE is divided into phases or periods based upon major milestones within the project or significant changes in the annual projected expenditures. The following phases correspond to the seven major decommissioning periods within the SSDCE. Details for each phase are provided in the subsections that follow. While SNF management items are provided here to give a complete overall picture of decommissioning, further details are included in the IFMP.

Table 2-1: DCPP Decommissioning Phases Summary Phase Phase Title Phase Phase General Description Start Finish 1 Pre-Shutdown Nov 2010 Oct 2024 Consists of detailed planning, Planning engineering, contracting, licensing, and permitting efforts.

2 Zirc Fire Nov 2024 Feb 2027 Transitions the plant to a decommissioning configuration to support safe and efficient decommissioning. Designates the timeframe where SNF is cooling in the spent fuel pools (SFPs).

3 Wet Storage Mar 2027 Nov 2028 Designates the timeframe where SNF continues to cool in the SFPs and/or is being transferred to the DC ISFSI.

Concurrently, preparations are continuing for major D&D in the next phase.

4 Building Dec 2028 Dec 2032 Consists of D&D of radiological SSCs.

Demolition Also includes removal of several ancillary (non-radiological) structures.

Page 9 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Phase Phase Title Phase Phase General Description Start Finish 5 Non-ISFSI Jan 2033 Apr 2035 Includes demolition of non-radiological Site structures, conduct of final radiological Restoration surveys to support license termination, and restoration of non-ISFSI areas.

Period ends with 10 CFR 50 license termination.

6 ISFSI May 2035 Aug 2067 Designates the timeframe after Operations 10 CFR 50 license termination where SNF and GTCC waste are stored only at the DC ISFSI and GTCC Waste Storage Facility, respectively, and transferred to the DOE for storage at a permanent off-site repository. This period also includes biological monitoring of the plant site restoration.

7 SNF and Sep 2067 Jan 2076 Consists of removal of ISFSI and GTCC GTCC Waste Storage Facility structures, Storage conduct of final radiological surveys for Demolition ISFSI license termination, restoration of and affected areas, and biological monitoring.

Restoration

2.1. Phase 1 - Pre-Shutdown Planning As discussed in Section 1.3, PG&E plans to transition DCPP directly from operational status to DECON status upon permanent shutdown. To support this, PG&E must implement decommissioning planning activities during the final years of plant operations including the following:

Preparation, submittal, and NRC review and approval of licensing submittals that support a decommissioning site status, such as revisions to Emergency Planning procedures, Security procedures, and DCPP Technical Specifications. Early approvals will allow preparation of the approved changes into plant documentation. Once conditions are met, PG&E can immediately implement the approved changes instead of taking several months or years to develop and issue documentation changes.

Preparation, submittal, and federal, state, and local agency review and approval of permitting submittals. Federal, state, and local permits and approvals are required to perform nearly every decommissioning activity.

Through these processes, the decommissioning project will be subject to thorough environmental review as required by both the National Environmental Policy Act (NEPA) and the California Environmental Quality Act (CEQA). If activities to support permitting are not initiated and completed sufficiently in advance of plant shutdown, all decommissioning activities will

Page 10 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 be delayed awaiting receipt of permits. PG&Es goal is to have the permits necessary to begin physical decommissioning activities in hand as of plant shutdown. See Section 2.8.6 for information on the Diablo Canyon Decommissioning Engagement Panel.

Completion of site radiological characterization, which provides the basis for radiation protection, identification of contamination, assessment of potential risks, cost estimation, planning, and implementation of decommissioning (as described in Section 2.8.1).

Development of the Waste, Transportation, and the Material Management programs.

Completion of detailed engineering, planning, and approvals for modifications (as described in Section 2.2); technical evaluations of waste packaging and transportation systems for the reactor vessel and reactor vessel internals; decommissioning program and procedure development; site infrastructure development; and site demolition planning.

Execution of contracts to support physical decommissioning activities.

2.2. Phase 2 - Zirc Fire Following reactor shutdown and final defueling of the reactor vessels, several modifications are needed at DCPP to support employee safety, infrastructure needs during decommissioning, and safe and reliable cooling of the SNF in the SFPs.

These include implementing site infrastructure modifications; SNF and GTCC waste storage modifications; and site security modifications. In addition, site characterizations and chemical decontaminations will take place. Each of these activities is discussed in more detail further below.

In addition to the modifications identified above, the following significant activities are also conducted in Phase 2:

start of radiological surveys start of reactor internals segmentation and removal preparations start of containment buildings, auxiliary building, and turbine building system and area closure, which consists of preparing a building for demolition turbine building and auxiliary building abatements and removals large component removals, such as steam generators, reactor heads, reactor coolant pumps, main generators, main turbines, and other various large components that must be removed prior to demolition

Site Infrastructure Modifications (see SSDCE Figure 5-1, items 95 - 98 and 100 -

106 for schedule)

Site infrastructure modifications are changes to site facilities, civil features, utilities, and equipment that will be required to support general decommissioning activities.

Page 11 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 By developing a robust infrastructure suited to decommissioning needs, these modifications will help transition DCPP from an operational site to a decommissioning site and provide the framework to successfully execute the project.

Site infrastructure changes to support decommissioning will take place during Phases 2 - 4. These changes cover many areas, including:

facilities (such as buildings, structures, trailers, defensive positions, sheds, and ancillary facilities) civil features (such as roadways, haul routes, drainage, parking lots, storage areas, staging areas, retaining walls, pathways, walkways, stairways, fences, and gates) overhead and underground utilities and systems (such as domestic water, fire water, electrical, wastewater, telecommunications, heating, ventilation, and cooling systems, fire detection and suppression systems, public address systems, site alarm systems, information technology systems, and light stanchions) specialty equipment, systems, and facilities (such as truck scales, portal monitors, gamma radiation assay survey system, passive and active vehicle barriers, alarm stations, control rooms, security access buildings, and waste processing facilities that reduce existing concrete into rubble)

Spent Nuclear Fuel and Greater than Class C Storage Modifications (see SSDCE Figure 5-1, item 99 for schedule)

PG&E has a site-specific license for the DC ISFSI. The CPUC required PG&E to conduct an assessment for expediting SNF offload to the DC ISFSI. The results of this study demonstrated that there are currently alternate dry casks storage systems available (as compared to those currently approved for use in the DC ISFSI site-specific license) that may reduce the cooling time required in the SFPs prior to transfer to the DC ISFSI. Thus, in 2020, PG&E conducted a request-for-proposal process to select an alternate dry cask storage system. In 2022, PG&E executed a contract with Orano TN Americas (Orano) for SNF and GTCC waste dry cask storage systems. In the 2022-2024 timeframe, PG&E and Orano will perform the work necessary to prepare for implementing the new dry cask storage systems, including any regulatory actions and preparation for physical modifications to the site (to be implemented in Phase 2) to store SNF at the DC ISFSI and GTCC waste at a new GTCC Waste Storage Facility. PG&E plans to employ the NUHOMS-EOS system to store SNF at DCPP under Certificate of Compliance 1042, which will be amended via NRC licensing action with Orano in the 2022-2024 timeframe. As this contract was recently executed, the cost and schedule updates associated with the new system have not been finalized. PG&E will provide a future update to the cost and schedule information in the IFMP and PSDAR to reflect implementation of the NUHOMS-EOS system at DCPP.

Security Modifications (see SSDCE Figure 5-1, items 98 and 100 for schedule)

There are significant changes at a site during decommissioning activities. Security plans and staffing can be adjusted to reflect the site changes. After Unit 1 shutdown, PG&E plans to implement physical security modifications to improve

Page 12 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 efficiency and, ultimately, security staff reductions while still maintaining a robust decommissioning defense strategy.

Site Characterizations (see SSDCE Figure 5-1, items 13 and 14 for schedule)

The approximately 750-acre industrial portion of the DCPP site will be characterized for both radiological contamination and non-radiological contaminants of concern.

Physical sampling and analysis will occur after Unit 1 and Unit 2 are shut down.

Radiological characterization will be conducted in accordance with NUREG-1575, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM)

(Reference 6). Non-radiological hazardous characterization will be in accordance with both federal and California Environmental Protection Agency (EPA) standards.

Chemical Decontamination (see SSDCE Figure 5-1, item 16 for schedule)

PG&E evaluated various methods available for reducing the radioactive source term in contaminated systems exposed to radioactive fluids. Based on the results of this evaluation, PG&E plans to perform chemical decontamination of the reactor coolant piping, pressurizer, chemical volume and control system, and residual heat removal system to reduce worker exposure during the decommissioning work.

2.3. Phase 3 - Wet Storage This phase designates the timeframe where SNF continues to cool in the SFPs and/or is being transferred to the DC ISFSI. Concurrently, preparations are being made for major D&D in Phase 4 and alternative power sources (cold and dark power

[C&DP]) modifications are being implemented. Significant activities include:

SFP operations and maintenance completion of reactor internals segmentation and removal SNF transfer to the DC ISFSI Unit 1 GTCC waste transfer to the GTCC Waste Storage Facility completion of containment buildings, auxiliary building, and turbine building system and area closure, which consists of preparing a building for demolition start of various support buildings demolition Unit 1 and 2 reactor pressure vessel segmentation and removal begins continuation of radiological surveys C&DP modifications

Perhaps the most significant safety hazard associated with decommissioning power plants is the risk posed by personnel and equipment coming in direct contact with exposed and energized electrical circuits. Industry operating experience indicates that even a robust electrical clearance program is insufficient at managing risks associated with electrical shock or arc flash events in power plants being decommissioned and demolished. The most effective approach to manage these risks is to remove or disconnect the original power supplies from structures and components within structures before undergoing demolition. This necessitates the installation of an alternate external power supply to support decommissioning work and for selected power plant loads and lighting. This alternate power supply,

Page 13 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 referred to as C&DP, is independent of the normal plant power supply and distribution system. PG&E intends to install C&DP to enhance worker safety and reduce the risk of decommissioning activities.

Once implemented, the C&DP system will continue to evolve along with the demands for electrical power to support decommissioning activities. Initially, at least two independent power supplies will be preserved to ensure reliable cooling of the SFPs. The original existing electrical sources will meet this requirement and are planned to be in place until all SNF has been removed from the SFPs.

2.4. Phase 4 - Building Demolition This period consists of D&D of radiological SSCs and removal of several ancillary (non-radiological) structures. Significant activities include:

remainder of Unit 1 and 2 reactor pressure vessel segmentation and removal Unit 2 GTCC waste transfer to the GTCC Waste Storage Facility fuel handling building, discharge structure, intake structure, balance of site, and various support buildings system and area closure, which consists of preparing a building for demolition remainder of large component removals containment buildings, auxiliary building, fuel handling building, turbine building, discharge structure, balance of site, and various support buildings demolition partial surveys and final decontamination start portions of site restoration of the non-ISFSI areas 2.5. Phase 5 - Non-Independent Spent Fuel Storage Installation Site Restoration This phase includes demolition of non-radiological structures (i.e., site restoration),

conduct of remaining radiological status surveys to support license termination, and restoration of non-ISFSI areas.

2.6. Phase 6 - Independent Spent Fuel Storage Installation Operations This phase designates the timeframe where the 10 CFR 50 licenses have been terminated, SNF and GTCC waste are stored at the DC ISFSI (10 CFR 72 license) and GTCC Waste Storage Facility, respectively, and then are transferred to DOE for storage at a permanent off-site repository.

2.7. Phase 7 - Spent Nuclear Fuel and Greater Than Class C Storage Demolition and Restoration This phase consists of removal of ISFSI and GTCC Waste Storage Facility structures after all SNF and GTCC waste have been transferred to the DOE for storage at a permanent off-site repository, conduct of final radiological surveys for ISFSI 10 CFR 72 license termination, and restoration of affected areas.

Page 14 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 2.8. General Decommissioning Considerations As defined in 10 CFR 50.2, definitions, a major decommissioning activity is any activity that results in permanent removal of major radioactive components, permanently modifies the structure of the containment, or results in dismantling components for shipment containing GTCC waste in accordance with § 61.55 of this chapter. The following discussion provides a summary of the major decommissioning activities currently planned for DCPP decommissioning. These activities are envisioned to occur in the Wet Storage and Building Demolition phases. The schedule may be modified as conditions dictate.

Prior to starting a major decommissioning activity, the affected components will be surveyed and decontaminated, as required, in order to minimize worker exposure, and a plan will be developed for the activity. Shipping casks and other equipment necessary to conduct major decommissioning activities will be procured.

The initial major decommissioning activity inside the containment building will be the removal, packaging, and disposal of systems and components attached to the reactor to provide access and allow it to be removed.

The reactor vessel internals will be removed from the reactor vessel and segmented for packaging, transport, and disposal. Internals classified as GTCC waste will be segmented and packaged into containers similar to spent fuel canisters and transferred to the GTCC Waste Storage Facility for storage until transferred to the DOE. Segmentation and removal of the reactor vessel follows the removal of the reactor internals.

In addition to the reactor and large components discussed above, all other plant components will be removed from the containment, auxiliary, turbine, and associated support buildings, radiologically surveyed and dispositioned appropriately.

2.8.1. Site Characterization A Historical Site Assessment (HSA) was performed for the site in 2018. This investigation collected information regarding the site history from the start of operations to the present and used the following sources of information:

annual environmental reports annual effluent reports licensee event reports 10 CFR 50.75(g) files groundwater sampling data radiation survey data area and boundary locations for radiological areas corrective action reports personnel interviews

Page 15 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 The HSA identified potential non-radiological contamination (i.e., petroleum hydrocarbons, asbestos, and lead paint) and potential radioactive contamination.

Both radiological and potential non-radiological contamination warrant additional investigation as part of the site characterization plan to be performed upon plant shutdown. Based on the results of the HSA:

There are currently not any known inaccessible areas that may contain radiological contamination.

Soil remediation is assumed to be necessary to reduce (1) soil radioactive contamination to levels that meet NRCs radiological release criteria for unrestricted use and (2) non-radioactive soil contamination to levels that meet the California Department of Toxic Substances Control (governed by the California EPA) chemical cleanup standards which will comply with federal EPA water quality standards at a minimum.

Active groundwater remediation is not anticipated for DCPP, as groundwater monitoring has not identified tritium at the well that is used for a drinking water source (located up DC, away from the power block).

As mentioned in Section 2.2, during the decommissioning process, site characterization will be performed in which radiological, regulated, and hazardous wastes will be identified, categorized, and quantified. Surveys will be conducted to establish the contamination and radiation levels throughout the site.

This information will be used in developing procedures, surveys, and sampling plans to ensure that hazardous, regulated, and radiologically contaminated areas are remediated and to ensure that worker exposure during decommissioning is controlled. As D&D work proceeds, surveys will be conducted to maintain a current site characterization and to ensure that decommissioning activities are adjusted accordingly.

After completing site decommissioning activities, the final status surveys will be performed to demonstrate that the remediated portion of the site (excluding the ISFSI containing the SNF and the GTCC Waste Storage Facility containing the GTCC waste) can be released for unrestricted use and removed from the license. The site release criteria is defined by the MARSSIM protocol and is in general 25 millirem per year from all pathways. Adherence to the NRC-approved LTP and MARSSIM guidance will ensure that the surveys are conducted so that applicable regulatory criteria are satisfied.

To support planning and scheduling of reactor pressure vessel and internals segmentation activities, a waste characterization analysis was performed to develop a basis for the radionuclide isotopes and concentrations that will be present in the reactor pressure vessels and internals at the time of final shutdown for Units 1 and 2. After final shutdown, a validation of the reactor internals and reactor pressure vessel characterization analysis will be performed to ensure radioactivity estimates and plans are adequate. Using the results of this validation analysis, neutron irradiated components will be classified in accordance with 10 CFR 61, Licensing requirements for land disposal of

Page 16 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 radioactive waste. The results of the initial waste characterization analysis and validation analysis form the basis of the plans for removal, segmentation, packaging, and disposal.

2.8.2. Groundwater Protection A groundwater protection program currently exists at DCPP in accordance with the Nuclear Energy Institute Groundwater Protection Initiative (GPI 07-007). This program is directed by procedures and will continue during decommissioning.

PG&E will also continue to maintain the existing radiological decommissioning records program required by 10 CFR 50.75(g). The program is directed by procedures.

Neither the monitoring results of the groundwater protection program nor events noted in the 10 CFR 50.75(g) files indicate the presence of long-lived radionuclides in sufficient concentrations following remediation as needed to preclude unrestricted release under 10 CFR 20.1402, Radiological criteria for unrestricted use.

2.8.3. Radioactive Waste Management A major component of the decommissioning work scope for DCPP is the packaging, transportation, and disposing of primarily contaminated/activated equipment, piping, concrete, and in some cases, soil. Demolition methods and handling techniques will be selected to minimize cross-contaminating clean materials with those required to be disposed of as wastes. To minimize cross-contamination with clean materials, the clean materials will be removed first, prior to building demolition if it will be reused, recycled, or repurposed and segregated from the transportation and storage areas used for radiological or hazardous/regulated materials.

A waste management plan was developed to incorporate the most cost-effective disposal strategy, consistent with regulatory requirements and disposal/processing options for each waste type. Currently, there are three licensed facilities that can accept DCPP radiological material for disposal in the United States: Clive Disposal Facility (EnergySolutions) in Clive, Utah; Waste Control Specialists LLC in Andrews, Texas; and US Ecology in Grand View, Idaho. Each of these facilities can receive different types of radiological materials. To the extent practical, PG&E will minimize the generation of Class B/C waste in order to avoid the high cost of disposing it. Further, much of the material that is potentially contaminated is expected to have very low radiological contamination, below Class A, known as low-activity radioactive waste (LARW).

The Idaho facility is currently the most cost-effective facility available to DCPP and permitted to accept LARW waste. PG&E will attempt to segregate LARW material from material that meets the Class A criteria because it can be disposed of at nearly one-fifth the cost of Class A waste. PG&Es disposal plans for DCPP Class A, B, and C waste are provided in Table 4-4 of the SSDCE. If other licensed disposal facilities become available in the future, PG&E may elect to use

Page 17 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 them. Radioactive wastes from DCPP will be transported by licensed transporters.

There are no facilities in the United States that can receive GTCC wastes. The GTCC wastes will be packaged in containers similar to those used for packaging of SNF in order to provide for safe onsite storage and to ensure that the material is isolated from the environment. As discussed previously, GTCC waste storage was included in the request-for-proposal process for an alternate dry cask storage system. Ultimately, PG&E anticipates the GTCC wastes will be transferred to DOE or some other federally licensed final repository.

2.8.4. Removal of Mixed Wastes Mixed wastes contain both a radioactive and chemical hazard, requiring increased controls on the disposal requirements for these wastes. If mixed wastes are generated, they will be managed in accordance with applicable federal and state regulations.

If generated, mixed wastes will be transported by authorized and licensed transporters and shipped to authorized and licensed facilities. If technology, resources, and approved processes are available, the processes will be evaluated to render the mixed waste non-hazardous.

2.8.5. Changes to Management and Staffing Throughout the decommissioning process, plant management and staffing levels will be adjusted to reflect the ongoing transition of the site organization. Staffing levels and qualifications of personnel used to monitor and maintain the plant during the various periods after plant shutdown will be subject to appropriate Technical Specification and Emergency Plan requirements. The anticipated staffing levels are discussed in the SSDCE and include the following types of staff:

Project Management Project Controls Engineering Decommissioning Plant Operations Maintenance Radiation Protection Final Status Survey Security Safety Procedure Writing Training Regulatory Management

Page 18 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 2.8.6. Diablo Canyon Decommissioning Engagement Panel Stakeholders have a vested interest in the safe, effective, and efficient completion of all decommissioning activities. Stakeholders include PG&E shareholders, employees, ratepayers, local community members, local government, state regulators, and federal regulators. Stakeholder interests range from continued employment opportunities to the radiological consequences of decommissioning activities to environmental impacts of previous plant operations and the site environmental end-state condition.

In 2018, PG&E formed the Diablo Canyon Decommissioning Engagement Panel as part of an effort to engage in open and transparent dialogue with interested stakeholders on matters regarding decommissioning (e.g., SNF, emergency planning, and the environmental permitting process) and future use of the lands around DCPP. The panel functions as a volunteer-based, non-regulatory body to enhance and foster open communication, public involvement, and education on PG&Es DCPP decommissioning and future land use plans. The Diablo Canyon Decommissioning Engagement Panel is consistent with the goals outlined in NRC's 2020 report "Best Practices for Establishment and Operation of Local Community Advisory Boards Associated with Decommissioning Activities at Nuclear Power Plants."1 PG&E intends to keep the Diablo Canyon Decommissioning Engagement Panel through DCPP decommissioning.

Panel members are volunteers and are not paid by PG&E or otherwise compensated for their time. Methods of communication with/from the panel may include routine meetings, letters, administrative meetings, joint public briefings, publication of a regularly updated panel Vision Document, and an open-door policy with management.

3. Schedule of Planned Decommissioning Activities

The schedule for DCPP decommissioning is presented in Table 2-1. Detailed schedules are provided in the SSDCE, Figures 5-1 and 5-2.

Future land uses at the DCPP site are currently being evaluated and discussed with community stakeholders. The schedule conservatively assumes the D&D of all DCPP structures to meet NRCs radiological release criteria for unrestricted use. PG&E is currently evaluating the possibility of phased release of the site, but no decisions have been made regarding this approach.

1 Publicly available: https://www.nrc.gov/docs/ML2011/ML20113E857.pdf

Page 19 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

4. Estimate of Expected Decommissioning Costs and Associated Funding

10 CFR 50.82(a)(4)(i) requires the submission of a PSDAR prior to or within two years following permanent cessation of operations that contains a SSDCE, including the projected cost of managing irradiated fuel.

PG&E has prepared a SSDCE for DCPP, which also provides projected costs of managing irradiated fuel, as well as non-radiological decommissioning and other site restoration costs. The SSDCE fulfills the requirements of 10 CFR 50.82(a)(4)(i),

10 CFR 50.82(a)(8)(iii), and 10 CFR 50.75(f)(3) and SSDCE, Revision 1, is being submitted concurrent with this PSDAR, Revision 1. A summary of the annual costs associated with irradiated fuel management is provided in the IFMP, Revision 1, which is also being submitted concurrently in accordance with 10 CFR 50.54(bb).

PG&E did not rely on a generic nuclear industry decommissioning unit cost factor methodology, but instead used a dedicated team of nuclear, decommissioning, and DCPP experts to form a detailed decommissioning plan, schedule, and associated cost estimate. The SSDCE is based on cost-based and historical bid-based estimating, direct experience gained by PG&E after 10 years of full-scale decommissioning at Humboldt Bay Power Plant Unit 3, industry expertise, and benchmarking. The planning team included experts in specific fields who understand the complexity and multi-discipline requirements for a project of this scale. This included PG&E leadership, decommissioning-experienced personnel, DCPP operating plant departmental personnel, specialty contractors, and corporate legal, finance, and accounting.

Under 10 CFR 50.82(a)(8), a licensee must provide reasonable assurance that funds will be available (or financial assurance) for decommissioning (i.e., license termination) costs. The regulations also describe the acceptable methods a licensee can use to demonstrate financial assurance. Most licensees do this by funding a nuclear decommissioning trust (NDT) fund. To assure that sufficient funds will be available for decommissioning, PG&E has established separate external sinking NDT fund accounts for DCPP, Units 1 and 2. As noted in the SSDCE, sufficient funds (based on balances and earnings) are projected to be available to complete license termination. PG&E currently has more funds in the NDT for DCPP Units 1 and 2 than required to meet the minimum NRC decommissioning amount for each unit that was calculated pursuant to the requirements of 10 CFR 50.75(c).

In addition, on September 10, 2019 (Reference 16), NRC granted exemptions from 10 CFR 50.82(a)(8)(ii) and 10 CFR 50.82(a)(8)(i)(A) to allow PG&E to withdraw

$187.8 million (2017 dollars) from the Diablo Canyon NDT for decommissioning planning between now and permanent cessation of operations, instead of three percent of the generic amount specified in 10 CFR 50.75. A portion of the funds will be used for pre-planning activities associated with spent fuel management and site restoration.

Page 20 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 The cost to decommission the site, safeguard the spent fuel and GTCC waste until it can be transferred to the DOE, and restore the impacted area of the site is estimated to be $4.08 billion in 2022 dollars. The summary of the costs estimated for License Termination, Spent Fuel Management, and Site Restoration activities are presented in Table 4-1.

Page 21 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Table 4-1 Cost Summary from DCPP Site-Specific DCE (in thousands of 2022 dollars)

A I J K ID Scope Description Total Estimate License Spent Fuel Site Restoration Termination Management Unassigned Costs 1 Decommissioning Program Oversight $362,704 $286,336 $37,126 $39,242 2 Site Costs $1,432,030 $879,994 $518,889 $33,146 3 Administration and General $283,937 $214,352 $68,081 $1,503 Discrete Costs 4 Decommissioning Preparations $38,509 $38,509 $ - $ -

5 Site Infrastructure $128,500 $128,500 $ - $ -

6 Large Component Removal $167,563 $167,563 $ - $ -

7 Reactor/Internals Segmentation $403,982 $403,982 $ - $ -

8 SNF and GTCC Transfer to Onsite Storage $264,756 $ - $264,756 $ -

9 Turbine Building $100,980 $62,767 $ - $38,213 10 Auxiliary Building $200,148 $85,952 $ - $114,196 11 Containment Building $315,913 $98,408 $ - $217,505 12 Fuel Handling Building $42,605 $42,605 $ - $ -

14 Balance of Site $90,193 $26,207 $ - $63,986 15 Intake Structure $11,685 $11,685 $ - $ -

16 Discharge Structure $18,768 $5,681 $ - $13,087 18 Non-ISFSI Site Restoration $154,039 $ - $ - $154,039 20 SNF and GTCC Storage Demolition and Restoration $62,216 $ - $62,216 $ -

GRAND TOTAL $4,078,527 $2,452,541 $951,069 $674,917 Note: Costs associated with IDs 13 and 19 were moved under other IDs, and therefore, are not shown in this table.

Costs associated with ID 17 are no longer applicable, and therefore, are not shown in this table.

Page 22 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

5. Environmental Impacts To support the PSDAR environmental review, the environmental effects of decommissioning activities planned for DCPP, as currently understood, were evaluated to determine if potential environmental impacts are bounded by previously issued environmental impact statements (Reference 7). 10 CFR 50.82(a)(4)(i) requires that the PSDAR include,... a discussion that provides the reasons for concluding that the environmental impacts associated with site-specific decommissioning activities will be bounded by appropriate previously issued environmental impact statements. As noted in Regulatory Guide 1.185, the PSDAR does not need to include the analysis of the specific environmental impacts associated with decommissioning activities....the licensee must ensure that supporting documentation and analyses are available at the reactor site for inspection by the NRC Staff. Such detailed documentation and analyses are contained in the Environmental Report (ER) (Reference 7) which is available onsite for NRC review.

To determine if the estimated potential environmental impacts associated with DCPP decommissioning activities are bounded, the following previously issued NEPA reviews were relied upon:

NUREG-0586, Final Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities, Supplement 1 (termed the Decommissioning GEIS) (Reference 3)

NUREG-1496, Generic Environmental Impact Statement in Support of Rulemaking on Radiological Criteria for License Termination of NRC-Licensed Nuclear Facilities (Reference 8).

Atomic Energy Commission, Final Environmental Statement related to the Nuclear Generating Station Diablo Canyon Units 1 & 2 (Final Environmental Statement [FES], Reference 9).

As required, site-specific assessments were conducted for threatened and endangered species and environmental justice. Site-specific assessments were also performed for impacts to aquatic ecology, terrestrial ecology, and cultural and historic resources for decommissioning activities beyond the operational area. For the purpose of assessing decommissioning environmental impacts, the operational area at DCPP is defined as the area within the site boundary plus a buffer at the discharge structure and the DCPP Access Road. This area encompasses the reactors and surrounding buildings, intake and discharge structures, parking lots, laydown yards, landscape-maintained areas, and transportation infrastructure. Operational area is defined in the Decommissioning GEIS.

The levels of significance assigned to site-specific environmental impacts are classified as small, moderate, or large, as defined by NRC in the Decommissioning GEIS (Reference 3, pgs. 4-1 and 4-2).

PG&E's current decommissioning plans include consideration of an existing offsite rail yard owned by PG&E for possible transport of non-radiological and non-hazardous wastes via rail from the facility. The Pismo Beach Rail Yard is located 9 miles from the Avila Beach PG&E security gate and is the most practical location for railroad transport during DCPP decommissioning. The Pismo Beach rail spur was constructed in the

Page 23 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 early 1970s by PG&E to support construction of DCPP. It is currently used by PG&E as a staging yard with shared use of buildings and parking lot infrastructure. Based on the potential use of the facility as contingency only, PG&E will only be performing maintenance activities to support contingency use. Therefore, there are no decommissioning activities in the current plans that will have an environmental impact on the Pismo Beach Rail Yard and the planned maintenance is not included in the below environmental evaluation.

Except for the potential impacts associated with cultural, historical, and archaeological resources discussed in Section 5.1.14, PG&E has concluded that the environmental impacts associated with planned DCPP decommissioning activities are small to moderate and are bounded by the impacts addressed by previously issued NEPA reviews. The potential for moderate to large impacts were identified as part of the site-specific evaluation for cultural, historical, and archaeological resources. As PG&E is currently in the planning phase, decommissioning plans continue to evolve. In accordance with 10 CFR 50.82(a)(4)(i), as more detailed plans are developed, PG&E will verify that decommissioning activities that impact cultural, historical, and archaeological resources are bounded by previously issued environmental impact statements or seek appropriate regulatory approval if needed prior to performing the activity.

DCPPs decommissioning plans are consistent with the methods assumed by NRC in the GEIS. No unique site-specific features or unique aspects of the planned decommissioning have been identified.

5.1. Environmental Impacts of Decommissioning The following is a summary of the reasons for reaching the conclusion that the environmental impacts of decommissioning DCPP are bounded by a previously issued NEPA review, or are site-specific and small to moderate. Each environmental resource evaluated in the Decommissioning GElS is listed along with an explanation as to why PG&E concludes that either a previously issued NEPA review bounds the impacts of DCPP decommissioning on that resource, or the impacts are site-specific and small, moderate, or large.

5.1.1. Onsite and Offsite Land Use In the Decommissioning GEIS, the NRC generically determined onsite land use impacts to be small for facilities having land-use changes only within the operational area (Reference 3, page 4-9). For decommissioning that involves land use changes outside the operational area, the GEIS concluded that impacts could not be predicted generically and must be evaluated on a site-specific basis.

Onsite Land Use Onsite land is expected to be used for decommissioning activities such as laydown, staging, handling, temporary storage, processing, packaging, and shipping of waste and materials; personnel processing; and parking. PG&E has determined that onsite land to be used to support decommissioning at DCPP has been previously disturbed and decommissioning activities would not result in changes in onsite land use patterns, except to the extent that onsite land may be

Page 24 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 restored to uses that are similar to current uses of the land surrounding the site.

Hence, PG&E concludes that no new and significant information has been identified regarding onsite land use and anticipated onsite land use impacts are bounded by the Decommissioning GEIS.

Offsite Land Use PG&E's current decommissioning plans do not include offsite land use.

5.1.2. Water Use The Decommissioning GEIS observes that quantities of water required during decommissioning are trivial (Reference 3, page 4-10) compared to those used when a plant is operating. The Decommissioning GEIS mentions construction dust abatement and decontamination (flushing systems or pressure washing components) as typical decommissioning water uses. NRC asserted in Section 4.3.2 in the Decommissioning GEIS that potential impacts of decommissioning on water use at all plants are neither detectable nor destabilizing and made the generic conclusion that impacts in all cases are small.

DCPP utilizes a once-through cooling water system for plant operations whereby seawater is drawn from the Pacific Ocean through a shoreline intake structure, used to cool plant components, and discharged back to the Pacific Ocean at a second, separate shoreline location. A seawater reverse osmosis treatment unit provides the majority of freshwater for plant primary and secondary systems makeup, fire protection system supply water, and source water for the plant domestic water system supply. DCPP also has one active permitted deep well (Deep Well #2) located in DC that supplies water to the makeup water system.

PG&E expects to reduce the Pacific Ocean water and groundwater withdrawals substantially following plant shutdown. PG&E assumes the DCPP water systems will be shut down after all SNF has been transferred to the ISFSI, and that the seawater reverse osmosis treatment unit and onsite well will provide the source water for potable water and non-potable water for a variety of uses. Based purely on staffing projections, the demand for potable/domestic water at the plant will be substantially lower during decommissioning years than during operational years, but it is expected that water will also be required during decommissioning for dust abatement and decontamination. Nevertheless, PG&E expects water use during DCPP decommissioning to be much lower than water use during operational years, consistent with the statements made in the Decommissioning GEIS. PG&E concludes that onsite decommissioning water use impacts for DCPP are small and are bounded by the Decommissioning GEIS.

5.1.3. Water Quality Decommissioning activities with potential for impacting surface water quality include fuel removal, stabilization, large component removal, decontamination and dismantlement, and structure dismantlement. Stormwater runoff and accidental releases (spills) are the most likely sources of pollutants entering surface waters during decommissioning. The Decommissioning GEIS asserts that regulatory programs applicable to permitted substance releases plus the

Page 25 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 application of best management practices (BMPs) for controlling stormwater runoff and erosion will render any change in surface water quality from decommissioning activities nondetectable and nondestabilizing. With respect to groundwater, the Decommissioning GEIS noted that demolishing concrete structures and storing rubble on site could result in changes (higher alkalinity) in local water chemistry, but the nonradiological effects of such changes on water quality would be nondetectable offsite at all nuclear power plants.

If decommissioning activities require ground disturbance of more than one acre in size, PG&E will obtain storm water construction general permits which requires development of a storm water pollution prevention plan. For smaller disturbances, PG&E will implement BMPs.

Compliance with permits and implementation of erosion and sediment controls, soil stabilization practices, structural practices, and pollution prevention measures will ensure that water quality impacts from decommissioning are small and temporary. Any land-disturbing activities would be of relatively short duration, permitted and overseen by responsible regulatory agencies, and guided by BMPs. Some soil disturbed during decommissioning could be carried with storm water into Diablo Creek or the Pacific Ocean, but to reduce the likelihood, disturbed areas would be stabilized (re-contoured and re-vegetated), limiting impacts, in accordance with required permits. Once slopes are stabilized and re-vegetated, the amount of erosion and sedimentation should be greatly reduced.

Spills of hazardous materials (liquids) are potentially a larger concern, as they are a threat to both surface waters and groundwater. The DCPP Spill Prevention, Control, and Countermeasure Plan addresses management and prevention of oil releases to the environment. PG&E expects to continue its compliance with existing regulations, which require reporting of spills of hazardous materials. Also, precautions will be taken to prevent spills of hazardous materials.

Removal of DCPP structures and buildings and related earth-moving work (digging, grading, filling) has at least a limited potential to affect water quality, but these kinds of construction activities routinely take place around operating nuclear power plants and are subject to the provisions of state-issued permits.

The topography of the DCPP area precludes any connection between the onsite and offsite groundwater resources. If any localized alteration in the groundwater chemistry associated with the use of backfill were to occur, it would not impact offsite groundwater quality.

In Section 4.3.3 in the Decommissioning GEIS, NRC concluded generically that for all facilities, decommissioning impacts to surface and groundwater quality would be small. Because there is nothing about DCPPs design, location, configuration, operating history, or decommissioning plans that would alter or contradict this generic conclusion and PG&E would comply with regulatory and permit requirements to protect surface water and groundwater resources, PG&E has determined that impacts of decommissioning on water quality would be small and bounded by the analysis in the Decommissioning GEIS.

Page 26 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 5.1.4. Air Quality The Decommissioning GEIS identified decommissioning activities that may have an effect on air quality as including worker transportation to and from the site, dismantling of systems and removal of equipment, movement and open storage of material onsite, demolition of buildings and structures, shipment of material and debris to offsite locations, and operation of concrete batch plants. The NRC considered the potential for adverse impacts from these activities, the greatest of which would be fugitive dust, for the range of decommissioning plants and generically determined air quality impacts to be small.

During DCPP decommissioning, appropriate and reasonable control measures will be taken to minimize fugitive dust. The California Air Resources Board (CARB) regulates fugitive dust, requiring construction and demolition sites to prevent, reduce, and mitigate fugitive dust so that emissions do not impact the National and California Ambient Air Quality Standards attainment status (CARB Rule 402). For example, during certain decommissioning activities such as building demolition, high-efficiency particulate air (HEPA) filtrations systems will be used as required, along with a dust suppression system. In addition, methods that limit releases to the environment as required by state and federal regulations will be used to purge systems. Permits applicable to the above decommissioning activities and equipment will be maintained/obtained as required. Compliance with permits and applicable laws and regulations, will minimize the potential impacts on air quality. The exhaust from commuting and shipping vehicles could affect air quality somewhat, but the workforce during decommissioning will be smaller than those used for construction or refueling outages (see Section 5.1.12). Hence, because (1) the air quality impacts from decommissioning activities at DCPP are expected to be temporary, localized, and small in magnitude; (2) reasonable and appropriate control measures would be employed; (3) the appropriate air permits would be obtained; and (4) there is nothing about DCPPs design, location, configuration, operating history, or decommissioning plans that would alter or contradict the generic conclusion in Section 4.3.4 in the Decommissioning GEIS, PG&E concludes that air quality impacts from DCPP decommissioning activities are bounded by the analysis in the Decommissioning GEIS.

5.1.5. Aquatic Ecology Aquatic resources may be directly or indirectly impacted by decommissioning activities. Direct impacts to aquatic communities may result from shoreline or in-water construction or from dredging. Indirect impacts may result from construction-related erosion and stormwater runoff. These impacts are typically undetectable (or barely discernible) and do not destabilize any important attributes of the resources. The Decommissioning GEIS concluded generically that such decommissioning activities within the operational areas of nuclear power plants, including removal of shoreline or in-water structures, would have only minor impacts on aquatic communities, provided all appropriate BMPs are employed. Therefore, Section 4.3.5 in the Decommissioning GEIS concluded that aquatic impacts from decommissioning activities would be small. The Decommissioning GEIS further states, however, that if decommissioning Page 27 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 activities outside of the operational area are anticipated, impacts to aquatic resources cannot be predicted and must be determined through site-specific analysis.

The aquatic resources of chief concern for decommissioning impacts at DCPP are the (1) Pacific Ocean intake and discharge coves and (2) Diablo Creek which runs along a portion of the site.

PG&E will use appropriate BMPs for non-in-water structure decommissioning activities; therefore, consistent with the Decommissioning GEIS, PG&E concludes that aquatic impacts from removing onsite non-in-water structures would be small.

DCPP decommissioning will include the removal of the discharge structure at the shoreline of the Discharge Cove. Removal of this structure is currently required by PG&Es lease with the California State Lands Commission (Reference 10) and will require federal, state, and local permits and approvals and CEQA process reviews. Since the discharge structure was constructed at DCPP, many aquatic communities have established themselves on it. Removal of the discharge structure has the potential to impact existing benthic marine invertebrate communities including the federally endangered black abalone, if present, marine algae, both surface and under-story algae within the inter-tidal and sub-tidal habitat and associated fish communities. There is also the potential for indirect impacts to marine mammals, such as the federally threatened southern sea otter, California sea lion, harbor seal, and green sea turtle which have occurred in the intake cove in the past (special-status species are discussed in more detail in Section 5.1.7). During removal of the discharge structure, PG&E will follow the mitigation, minimization, and avoidance measures required by the necessary federal, state, and local permits obtained and use appropriate BMPs. Therefore, PG&E concludes that aquatic impacts from removing the discharge structure would be small and are bounded by the Decommissioning GEIS.

Existing structures will be used for barge loading activities; thus, there are no environmental impacts associated with barging infrastructure.

5.1.6. Terrestrial Ecology Section 4.3.6 of the Decommissioning GEIS maintains that "[f]or facilities where habitat disturbance is limited to operational areas, the impacts on terrestrial ecology (i.e., plant and animal communities) are not detectable or destabilizing,"

primarily because most vegetation and wildlife habitat in the operational area was removed during plant construction. NRC staff concluded that, "for such facilitiespotential impacts to terrestrial ecology are small" and no further mitigation measures are warranted. Site-specific analysis is only required of licensees when decommissioning activities are likely to occur outside of the operational area.

DCPP decommissioning activities within the operational area are bounded by those evaluated in the Decommissioning GEIS. Because PG&E will use Page 28 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 appropriate BMPs during DCPP decommissioning, consistent with the Decommissioning GEIS, PG&E concludes that terrestrial impacts from decommissioning within the operational area would be small and bounded.

5.1.7. Threatened and Endangered Species The Decommissioning GEIS lists stabilization, large component removal, decontamination and dismantlement (removal of contaminated soil), and structure dismantlement as activities with potential to impact threatened and endangered species. Section 4.3.7 in the Decommissioning GEIS did not make a generic determination on the impact of decommissioning on threatened and endangered species, noting that impacts to these species are expected to be minor and nondetectable when activities are confined to the site operational area.

Impacts are to be determined on a site-specific basis, paying particular attention to activities outside of the developed operational area. Noise and dust generation from construction activity and increased truck traffic, rather than direct impacts such as habitat destruction, are the primary concerns.

Table 5-1 presents a list of special status species that have been observed or have a high potential to occur (i.e., suitable habitat is available) in the DCPP operational area. PG&E compiled this list from several resources, including the following, and used recent species status designations from the California Department of Fish and Wildlife (Reference 11):

2004 DOE report on threatened or endangered species (Reference 12) 2006 National Marine Fisheries Service Biological Opinion on the effects of continued operation of DCPP on federally listed aquatic species (Reference 13) 2010 National Marine Fisheries Service response to NRC request for information on threatened or endangered species in the vicinity of the DCPP site (Reference 14) ongoing intertidal and shallow subtidal area benthic monitoring from prior to plant start up to present DC lands inventory studies conducted on numerous occasions from 1992 to 2012 marine and terrestrial field surveys conducted in 2020 to support DCPP decommissioning permitting efforts

Page 29 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Table 5-1 Threatened and Endangered Species Identified Within the Vicinity of DCPP1

Critical Scientific Name Common Name State Federal Habitat Status(2) Status(3) within Vicinity(1)

AMPHIBIAN SPECIES Rana draytonii California red-legged -- FT Yes frog AVIAN SPECIES Charadrius Western snowy -- FT Yes alexandrines plover Vireo bellii pusillus Least Bell¶s vireo SE )E No FISH SPECIES Acipenser medirostris Green sturgeon -- FT No Eucyclogobius Tidewater goby -- FE No newberryi Oncorhynchus kisutch Coho Salmon [south of Punta Gorda] ST FT No Oncorhynchus mykiss Steelhead )T <es Oncorhynchus Chinook salmon -- FT No tshawytscha INVERTEBRATE SPECIES Haliotis cracherodii Black abalone )E <es Helminthoglypta Morro shoulderband -- FE No walkeriana snail MAMMALIAN SPECIES Arctocephalus Guadalupe fur seal ST FT No townsendi Balaenoptera Blue whale -- FE No musculus Balaenoptera Fin whale -- FE No physalus Enhydra lutris nereis Southern sea otter )T No Megaptera Humpback whale -- FE No novaeangliae Orcinus orca.iller whale )E No Physeter Sperm whale -- FE No macrocephalus PLANT SPECIES Arctostaphylos Morro manzanita -- FT No morroensis Arenaria paludicola March sandwort SE FE No Nasturtium gambelii Gambel's watercress ST FE No

Page 30 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Critical Scientific Name Common Name State Federal Habitat Status(2) Status(3) within Vicinity(1)

REPTILIAN SPECIES Caretta caretta Loggerhead sea turtle -- FE No Chelonia mydas Green sea turtle -- FT No Dermochelys coriacea Leatherback sea -- FE Yes turtle Lepidochelys olivacea Olive Ridley¶s turtle )T No Notes

:ithin miles oI DCPP )E )ederally listed as Endangered

SE State listed as Endangered )T )ederally listed as Threatened ST State listed as Threatened

The )ES listed terrestrial and aTuatic rare, endangered, and declining species known to occur in the DCPP area

Decommissioning activities with greatest potential Ior directly and indirectly aIIecting terrestrial threatened and endangered communities include those associated with demolishing maMor reactor structures Land within the operational area is suIIicient to provide space Ior laydown yards, eTuipment or materials storage, temporary oIIices, and other decommissioning support areas or structures Current parking Iacilities have been adeTuate to support reIueling and maintenance outages through Iacility history and are assumed to be adeTuate to support decommissioning Because there is ample open space to support DCPP decommissioning operations, there would be no reason to clear any land outside oI the site operational area ThereIore, there would be no direct impacts to the habitat oI any terrestrial threatened or endangered species Decommissioning activities will be conIined to the operational area, which contains undeveloped portions adMacent to roads and Iacilities that are exposed to a Iairly constant level oI noise and human activity

During DCPP decommissioning, appropriate and reasonable control measures will be taken to minimi]e Iugitive dust, such as wetting oI soils During certain decommissioning activities such as building demolition, HEPA Iiltrations systems will be used as reTuired, along with a dust suppression system

)ederally endangered black abalone are known to occur in the intertidal ]one oI DCPP )ederally designated critical habitat is also present within the intertidal

]ones oI the coast around DCPP, including in the discharge and intake coves and along the breakwaters )ederally threatened southern sea otter and green sea turtle are also known to occur in the intake cove and discharge cove Direct and indirect impacts to these protected species may occur during demolition oI the discharge structure, including direct mortality oI individual species, as well as impacts Irom runoII, sedimentation, dust generation, or noise disturbance Measures to avoid or minimi]e impacts to threatened and endangered species

Page 31 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 within the intake cove and discharge cove would be carried out pursuant to permit conditions.

Per the Decommissioning GEIS (page 4-29), these impacts to endangered or threatened species may be detectable, but not destabilizing. Therefore, impacts to ecological resources as a result of decommissioning activities within the operational area, including threatened and endangered species, are expected to be moderate. Because the FES listed terrestrial and aquatic rare, endangered, and declining species known to occur in the DCPP area, PG&E concludes the potential impacts to threatened and endangered species are bounded by the FES.

5.1.8. Radiological The Decommissioning GEIS considered radiological doses to workers and members of the public when evaluating the potential consequences of decommissioning activities and concludes that radiological impacts of decommissioning activities are small.

Occupational Dose One conclusion of the Decommissioning GEIS is that, based on decommissioning experience, occupational dose during decommissioning is comparable to that observed during routine operations at the same or similar facilities. Therefore, PG&E evaluated DCPP operational dose data and compared it to that of other PWRs and established that DCPP operating collective dose has been below the average of U.S. PWRs. In addition, the average individual worker dose at DCPP is well below the average worker dose during operations for the decommissioning sites considered in the GEIS (Reference 3, page G-15). Similar to DCPP, the decommissioning sites evaluated in the GEIS include sites that have transitioned directly into DECON.

DCPPs current decommissioning plans fall within decontamination, dismantlement, and waste processing activities considered by the NRC in the GEIS. Thus, DCPP decommissioning collective dose is estimated to be bounded by typical decommissioning U.S. PWRs. In addition, during decommissioning PG&E plans to chemically decontaminate specific portions of the nuclear steam supply system. This chemical decontamination will reduce the radioactive source term, and therefore reduce the potential for decommissioning personnel to receive high doses from fixed contamination typically associated with corrosion or oxide products on inside surfaces of metal components and piping. During decommissioning, PG&E will maintain the as low as reasonably achievable (ALARA) Program to ensure that occupational dose is maintained ALARA and well within the 10 CFR 20 limits.

Public Dose Section 4.3.8 in the Decommissioning GEIS states that radionuclide emissions in gaseous and liquid effluents are reduced in facilities undergoing decommissioning. Given that DCPP public doses during operations were well below the NRC-established public dose limits, it is reasonable to expect that public doses during decommissioning would also be well below such limits.

Page 32 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Annual reports of environmental monitoring at DCPP for the years from 2013 through 2020 demonstrate that radioactivity levels in the offsite environment are well below the NRC established public dose limits, and controls on potential radiological releases will continue to be applied during decommissioning.

Conclusion PG&E concludes that radiological impacts of PG&E decommissioning are small for the following reasons:

The Decommissioning GEIS generic evaluation of radiological impacts applies to a typical PWR. Occupational and public dose from normal DCPP operations are like those of other PWR plants, indicating that DCPP doses are typical.

The decommissioning sites considered in the GEIS include sites that have transitioned directly into DECON.

DCPP implements administrative dose limits well below the regulatory limits and will continue to implement the ALARA Program.

DCPPs current decommissioning plans fall within decontamination, dismantlement, and waste processing activities considered by the NRC, and site-specific conditions do not represent unique conditions that would lead to a conclusion different than that reached in the Decommissioning GEIS.

Radiological impacts are considered to be undetectable and nondestabilizing, in the NEPA sense, if doses remain within regulatory limits (Reference 3, page 4-33)

During Decommissioning, PG&E plans to chemically decontaminate specific portions of the nuclear steam supply system to reduce the radioactive source term.

Therefore, PG&E concludes that the radiological impacts of DCPP decommissioning are small and bounded by the Decommissioning GEISs assessment.

5.1.9. Radiological Accidents Section 4.3.9 in the Decommissioning GEIS examined a range of radiological accidents hypothetically possible during the decommissioning period. These included anticipated operational occurrences, non-nuclear fuel-related accidents, and nuclear fuel-related accidents. NRC determined that many of these accidents had been previously analyzed in environmental reviews for the operation of the plant. The Decommissioning GEIS concludes that impacts of radiological accidents of all types applicable to decommissioning activities are small.

The anticipated operational occurrences such as those identified in the Decommissioning GEIS were considered in the FES (Reference 9, Section 7.1) for operation of DCPP. Given their potential to result in offsite doses, the Decommissioning GEIS considered SNF accidents of most concern for decommissioning. Once removed from the SFPs, however, SNF management is

Page 33 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 no longer within the scope of decommissioning environmental review because NRC evaluated the environmental impacts of continued SNF storage for all nuclear power plants in NUREG-2157, Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel, (Reference 15). Consequently, the only accidents of importance to offsite doses during decommissioning are those involving SNF in the SFP. SFP accidents would no longer be applicable after the SNF is removed from the SFPs and transferred to the ISFSI.

The most significant of the SNF accidents, in terms of consequences and probability, involves SFP drainage leading to a zirconium fire. However, the NRC, in both NUREG-2157 and the Decommissioning GEIS, determined that the risk of a zirconium fire is very low because of the very low likelihood of a zirconium fire, even though the consequences of a zirconium fire could be serious (Reference 3, page 4-43).

In the Decommissioning GEIS (Reference 3), the NRC, after reviewing existing information from licensees documents analyzing accidents from decommissioning activities and from a technical review of SFP accident risk at decommissioning nuclear power facilities, generically determined that the potential impacts of non-SNF related and of SNF-related radiological accidents resulting from decommissioning to be small. This analysis was based on the current design basis and maintaining an acceptable design and performance criteria throughout the life of the plant.

These same conditions are applicable to DCPP as a licensed plant maintaining its licensing basis and safety analysis along with the environmental impact assessment of radiological accident risk as documented in the FES (Reference 9). PG&E knows of no unique features or conditions at DCPP that would lead to a conclusion different than that reached in the Decommissioning GEIS (Reference 3). Therefore, PG&E concludes that radiological accident impacts of decommissioning activities at DCPP are bounded by those in the Decommissioning GEIS, resulting in small impacts.

5.1.10. Occupational Issues Section 4.3.10 in the Decommissioning GEIS concluded that impacts due to nonradiological occupational issues would be small for all plants based on strict adherence to NRC and Occupational Safety and Health Administration (OSHA) safety standards, practices, and procedures.

DCPP decommissioning will continue to implement an industrial safety program during decommissioning for decommissioning-related work in compliance with OSHA, NRC, California Division of Occupational Safety and Health, and PG&E requirements. For DCPP, the average incident rate falls well below that of the 2020 construction industry sectors average incident rate and compares favorably with the United States 2020 incident rate for the electrical power generation industry sector. Because the industrial safety program will be continued and would be expected to be effective in preventing occupational injuries and illnesses, decommissioning activities are expected to have a small impact on

Page 34 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 occupational issues. The DCPP decommissioning plan poses no unique hazards from what was evaluated in the Decommissioning GElS. Accordingly, PG&E concludes that anticipated impacts resulting from nonradiological occupational issues during DCPP decommissioning are small and thus bounded by the analysis in the Decommissioning GEIS.

5.1.11. Cost Section 4.3.11 of the GEIS recognizes that an evaluation of decommissioning cost is not a NEPA requirement. Therefore, a bounding analysis is not applicable. However, as required for a PSDAR, PG&E has developed a SSDCE for DCPP Units 1 and 2 that is described in Section 4.

5.1.12. Socioeconomics Section 4.3.12 in the Decommissioning GEIS evaluated changes in workforce and population, changes in local tax revenues, and changes in public services for decommissioning. NRC considered the decreases in workforce and tax payments related to the cessation of operations outside the scope of decommissioning. The Decommissioning GEIS concluded that socioeconomic impacts are neither detectable nor destabilizing and that mitigation measures are not warranted.

As DCPP ceases operation and transitions through the phases of decommissioning, an overall decrease in plant workforce and tax payments will occur. The changes during decommissioning would primarily impact San Luis Obispo County where the majority (approximately 82 percent) of the plant workforce resides and which receives the DCPP property tax payments. The largest station workforce reduction (during decommissioning) would decrease the San Luis Obispo County population by 0.91 percent. DCPP is not a significant source of tax revenue for state and local government. Plant property tax payments during operation have been approximately 4.1 percent of San Luis Obispo County. Compared with the existing property tax base, the anticipated decrease in DCPP property taxes as a result of decommissioning is likely to be small.

Based on the findings summarized above, PG&E concludes that impacts to socioeconomic resources from DCPP decommissioning would be small and thus bounded by the analysis in the Decommissioning GEIS.

5.1.13. Environmental Justice Section 4.3.13 in the Decommissioning GEIS determined environmental justice to be an environmental impact area for which no generic conclusion could be determined due to its site-specific nature. Therefore, the Decommissioning GEIS indicates that site-specific assessments for each decommissioning nuclear power plant must be prepared.

PG&E prepared a site-specific assessment of environmental justice as it relates to the effects of DCPP decommissioning. PG&E examined the geographic distribution of minority and low income populations within a 50-mile radius of the Page 35 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 DCPP site using the 2016 American Community Survey Five-Year Summary data. The results of the analysis indicate that two minorities had census block groups within the 50-mile radius with significant percentages of minority populations - (1) Hispanic, Latino, or Spanish Ethnicity, and (2) All Other Single Race Minorities - and there are three census tracts north of San Luis Obispo within the 50-mile radius that have a significant percentage of low income households.

Except for cultural, historical, and archaeological resources, PG&E determined that decommissioning impacts to all resource areas would be small to moderate, indicating the effects may noticeably alter but not destabilize any important attribute of the resource. Except for cultural, historical, and archaeological resources, because no member of the public will be substantially affected, there can be no disproportionately high and adverse impact or effects on minority and low-income populations resulting from the decommissioning of DCPP.

In Section 5.1.14, PG&E concludes that impacts to cultural, historical, and archaeological resources from decommissioning activities within the DCPP operational area would be moderate to large. PG&E will take steps, prior to commencing ground disturbing activities, to consult stakeholders on ways to minimize and/or mitigate impacts. PG&E has initiated outreach to Native Americans identified by the California Native American Heritage Commission for consultation (see Section 5.1.14 below for further details on recent ethnohistorical and genealogical research conducted for the DCPP area). PG&E expects to resolve the potential adverse effects in consultation with stakeholders, including the NRC, State Historic Preservation Officer, and consulting Northern Chumash tribes. Because the minority and low-income populations analysis did not identify American Indian or Alaskan Native (i.e., those to be impacted by cultural impacts) within the 50-mile radius with significant percentages of minority populations, and because the identified minority and low income populations are not near the DCPP area, there can be no disproportionately high and adverse impact or effects on minority and low-income populations. Based on these site-specific findings, PG&E concludes that the impacts of decommissioning DCPP on minority and low-income populations are small.

5.1.14. Cultural, Historical, and Archaeological Resources Section 4.3.14 in the GEIS determined that potential effects of decommissioning on cultural, historical, and archaeological resources would be small for all plants when the decommissioning activities are confined to the operational area.

However, impacts outside the operational area "must be determined through site-specific analysis."

PG&E anticipates that decommissioning activities will take place within the DCPP operational area.

Decades of archaeological research on the Diablo Canyon lands have provided complete systematic survey coverage of the coastal terrace, including the developed plant operational area. More recently, the Santa Barbara Museum of

Page 36 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Natural History documented an ethnohistorical and genealogical study for the DCPP area: "Descendants of Native Rancherías in the Diablo Lands Vicinity: A Northern Chumash Ethnohistorical Study." The extent of previous studies for the DCPP operational area and surrounding 6-mile radius have been established by compiling bibliographic references, previous survey reports, and archaeological site records through records searches of the California Historical Resources Information System at the Central Coastal Information Center at the University of California, Santa Barbara.

The DCPP operational area is comprised of two elements; the central area of DCPP (plant site) and a road that runs from Avila Beach to the plant site (DCPP Access Road). Although both of these areas are within the DCPP operational area, their resources will be discussed separately.

Cultural resource studies completed in the last 70+ years have identified a range of prehistoric and historic period resources on Diablo Canyon lands. In conjunction with California State Parks, PG&E has recently undertaken nomination of the Rancho Canada de los Osos y Pecho y Islay Archaeological District (Boundary Increase) (District). This District comprises 2,434 acres and includes 84 contributing archaeological sites (15 previously listed resources and 69 nominated resources) and 22 non-contributing archaeological sites along the coastal terrace within PG&Es property (including portions of the DCPP operational area) and Montana de Oro State Park, north of Avila Beach, San Luis Obispo County, California.

Of the 106 sites within the District, all but 22 sites are on Diablo Canyon lands.

Of the known sites on the Diablo Canyon lands, 16 are currently listed on the National Register of Historic Places (NRHP) as contributing elements to the District. An additional 59 sites were recommended eligible to the National Register as contributing elements of the District, although the State Historic Preservation Officer (SHPO) has not yet concurred. Another nine sites have been recommended as non-contributing sites to the District to the National Register due to a lack of significance and/or integrity. Nonetheless, all resources are managed as if they are eligible to the NRHP until demonstrated otherwise with SHPO concurrence.

Table 5-2 compiles the list of known cultural resources located within the DCPP operational area, including sites within 30 meters of the DCPP operational area Access Road.

There is a total of 22 cultural resources within the DCPP operational area, nine of which are within the plant site boundaries and thirteen within 30 meters of the DCPP Access Road (Table 5-2). Three sites, CA-SLO-59, -585, and -682/689, are bisected by the DCPP Access Road.

Known cultural resources within the plant site (CA-SLO-2/3, -61, -584, -1159, -

1160, -1161, -1162, -1163) are within the District. CA-SLO-2/3 is listed on the National Register of Historic Places and CA-SLO-584 has been destroyed as a

Page 37 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 result of the original construction of the DCPP switchyard. CA-SLO-61, -1159, -

1160, -1161, -1162, and -1163 are sites found to be contributing to the District.

Decommissioning activities within previously disturbed portions of the operational area will not impact most of the previously identified cultural resources, because PG&E intends to avoid ground disturbances during decommissioning in the areas of high archaeological sensitivity at CA-SLO-584, -1159, -1160, -1161, -1162, -

1163, and -2866 within the plant site; and CA-SLO-52, -53/62, -54/63/1411, -59, -

585, -682/689, 686, -687/916, -773, -1507, -1508, -2863, and -2867 along the DCPP Access Road. CA-SLO-2 and CA-SLO-61 are likely to experience adverse effects from planned decommissioning activities.

During initial DCPP licensing, the CA-SLO-2 site was recognized as a significant cultural resource and the Environmental Protection Plan includes specific measures to ensure preservation of the resources at this site. CA-SLO-61 was not included in the Environmental Protection Plan, but was mentioned in a letter attached to the FES. The letter was from a California State Park Archaeologist requesting that the office be kept advised of construction proposals that could impact CA-SLO-2, -61, and -584 (the only three surveyed sites at the time). Site disturbances at CA-SLO-2 and -61 during decommissioning are likely to result in destruction or alteration that would impair its significance with the potential for disinterring human remains. Therefore, PG&E concludes there is potential to have moderate to large impacts on cultural, historical, and archaeological resources. Impacts to cultural resources now listed in or determined eligible for the NRHP will be avoided where possible. Accordingly, PG&E concludes that potential impacts to cultural and historical resources from decommissioning activities within the DCPP operational area would not be bounded by a previously issued environmental impact statement. PG&E expects to resolve the potential adverse effects in consultation with stakeholders, including the NRC, State Historic Preservation Officer, and consulting Northern Chumash tribes.

Following construction of DCPP and the resulting impacts to CA-SLO-2, -61 and

-584, PG&E has responsibly managed significant cultural resources within the Diablo Canyon lands for more than 40 years. Land-disturbing activities at DCPP are reviewed in accordance with DCPP Land Stewardship guidance and the DCPP archaeological resources management plan to ensure the conservation of cultural resources. The Land Stewardship Committees guidance emphasizes preserving significant cultural resources in-place and avoiding damage to the maximum extent feasible. Complete impact avoidance is the preferred approach for National and California Register-eligible resources, as well as those with undetermined status. In instances where effects are unavoidable, PG&E has implemented prudent treatment measures to conserve the values associated with the affected resources, in consultation with affiliated communities, tribal groups, and appropriate agencies. Treatment measures include partnering with regional scholars to undertake data recovery excavations, compilation of a Pecho District radiocarbon database, updating the Pecho District National Register nomination, ethnographic documentation, development of interpretive signage, sharing

Page 38 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 research findings in the Native and archaeological community, as well as employee and trail docent education.

As PG&E is currently in the planning phase, decommissioning plans continue to evolve. In accordance with 10 CFR 50.82(a)(4)(i), as more detailed plans are developed, PG&E will assess proposed decommissioning activities that have the potential to affect cultural, historical, and archaeological resources to determine if impacts are bounded by previously issued environmental impact statements and seek appropriate regulatory approval if needed prior to performing the activity.

PG&Es assessment of the current decommissioning scope indicates impacts to two historic properties (CA-SLO-2 and -61) exceed the threshold of small as described in the GEIS and may warrant consultation. Expected impacts warrant consultation with stakeholders and mitigation to reduce the severity of impacts.

Table 5-2 Known Cultural Resources Within the DCPP Operational Area Site No. National District CA-SLO-Age Site Type Register Status1 Location Status 2/3 P Prehistoric village Listed L Plant Site 52 P Village Listed L DCPP Access Road 53/62 P Village Listed L DCPP Access Road 54/63/1411 P Village Listed L DCPP Access Road 59 P Short-term residence Eligible** C DCPP Access Road 61 P Midden Eligible* C Plant Site 584 P Short-term Destroyed NC Plant Site residential 585 P Village, ideological Listed L DCPP Access Road 682/689 P Village Listed L DCPP Access Road 686 P Short-term residence Listed L DCPP Access Road 687/916 P Long-term residence Listed L DCPP Access Road 773 P Village Not determined NA DCPP Access Road 1159 P Short-term Eligible* C Plant Site residential 1160 P Short-term Eligible* C Plant Site residential 1161 P Short-term Eligible* C Plant Site residential 1162 P Short-term Eligible* C Plant Site residential 1163 P Lithic and shell Eligible** C Plant Site scatter 1507 P Long-term residence Eligible** C DCPP Access Road 1508 P Location Eligible** C DCPP Access Road 2863 P Short-term residence Eligible** C DCPP Access Road 2866 P Location Eligible** C Plant Site 2867 P Short-term residence Eligible** C DCPP Access Road P = prehistoric

Page 39 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1

Appears to meet National Register criteria; SHPO has not yet concurred.

- Appears to meet National Register criteria as a part of a District; SHPO has not yet concurred.

1NRHP Status Codes: L = Already listed as part of the District; C = Contributing resource; NC = Noncontributing resource

5.1.15. Aesthetic Issues Section 4.3.15 in the Decommissioning GEIS singles out structure dismantlement and entombment as the only activities that may have impacts on aesthetic resources. The aesthetic impacts of decommissioning fall into two categories:

(a) impacts, such as noise, associated with decommissioning activities that are temporary and cease when decommissioning is complete and (b) the changed appearance of the site when decommissioning is complete. NRC drew the generic conclusion that for all plants, the potential impacts from decommissioning on aesthetics are small and that the removal of structures is generally considered beneficial to the aesthetics of the site.

The DCPP site is bordered on the west by the Pacific Ocean, on the east by the Irish Hills, and to the north and south by PG&E controlled lands. As a result, DCPP is viewable to the public only from two possible perspectives: Point Buchon Trail and the Pacific Ocean. The only publicly accessible, land-based area from which the DCPP facility is visible is from a short section of the Point Buchon Trail (a PG&E managed access trail north of the DCPP site), which resides on PG&E property approximately 2.2 miles north of the plant site. The DCPP site may also be somewhat visible from the Pacific Ocean from the west and south. However, the Captain of the Port of Los Angeles-Long Beach, under the authority of 33 U.S.C. 1226 and 1231, has established a Security Zone in the Pacific Ocean from surface to bottom, within a 2,000-yard radius of DCPP. No person or vessel may enter or remain in this Security Zone without permission of the Captain of the Port of Los Angeles-Long Beach. At a distance of 2,000 yards (1.14 miles) views of the DCPP site and access road are visually subordinate.

During decommissioning, the impact of noise and dust would be temporary and controlled to minimize impacts, as discussed in Sections 5.1.4 and 5.1.16. The appearance of DCPP will be altered as the buildings are dismantled. The changes in appearance would be noticeable from the Pacific Ocean and a short section of the Point Buchon Trail. During dismantlement, the visual intrusion would be temporary and would serve to reduce the aesthetic impact of the site.

Therefore, PG&E concludes that the aesthetic impact of DCPP decommissioning is small and is bounded by the Decommissioning GEIS.

5.1.16. Noise Section 4.3.16 in the Decommissioning GEIS generically examined noise during decommissioning, concluding that noise impacts would be small.

The noise levels associated with the decommissioning activities are not expected to be any more severe than during refueling outages and are not expected to present an audible intrusion on the surrounding community and environment.

Page 40 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Decommissioning activities will be primarily limited to previously disturbed land surrounding the power block and isolated from both wildlife and members of the public. Therefore, because DCPP decommissioning activities are of the type previously considered by NRC and DCPP has no site-specific conditions that would alter the NRCs prior findings, PG&E concludes that the noise impacts from decommissioning activities would be small and thus bounded by the analysis in the Decommissioning GEIS.

5.1.17. Transportation In Section 4.4.17 of the Decommissioning GEIS, the NRC states that its regulations are adequate to protect the public against unreasonable risk from the transportation of radioactive materials. Therefore, the effects of transportation of radioactive waste on public health and safety are considered to be neither detectable nor destabilizing.

Radiological: PG&E will comply with NRC and Department of Transportation regulations for shipments of radioactive waste from DCPP decommissioning.

The Decommissioning GEIS analyzes radiological shipments of waste from decommissioning and calculates incident-free doses and latent cancer fatalities to crew, the public along the route, and onlookers. The Decommissioning GEIS also calculates the collective dose for radiological accidents during transportation. The calculated impacts are closely related to the distance shipped, volumes shipped, and activity levels. The estimated volumes of radioactive waste associated with DCPP decommissioning are summarized in Table 4-3 of the SSDCE.

The waste volumes estimated per unit to be shipped are higher, but the number of shipments for each waste classification is lower than the NRC had assumed for its Decommissioning GEIS analysis. While the very low-activity and low-activity waste volume for DCPP is higher, other parameters greatly reduce worker and population exposure:

PG&E currently plans to ship a portion of radiological waste first by truck from DCPP to a nearby railyard. For these shipments, the majority of the distance to the disposal site will be traveled by rail. In addition, some of the waste will be shipped via barge and will then be trucked to the disposal facility. The NRC indicates in the Decommissioning GEIS that use of rail reduces radiological impacts by more than a factor of 10 over truck shipments (Reference 3, page 4-79) and barge shipments can reduce radiological impacts. However, there are some shipments that will be shipped via direct truck from DCPP to the disposal facility.

PG&E considered a scenario that bounds the potential distance the DCPP waste shipments would travel. In this scenario, Class A, B, and C wastes are assumed to be shipped to the farthest disposal site available for DCPP waste at Waste Control Specialists in Andrews, Texas. The shipping distance between DCPP and Waste Control Specialists in Andrews, is

Page 41 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 60 percent of the distance assumed by NRC in its Decommissioning GEIS analysis.

Nonradiological: Nonradiological impacts of transportation include increased traffic and wear and tear on area roadways. Traffic associated with decommissioning, including workers, would use the same set of local roads surrounding the plant site.

At the peak of decommissioning, the total workforce is estimated to be less than 80 percent of the workforce during plant operations, which would result in lower traffic than during operations.

The Decommissioning GEIS concludes that both nonradiological and radiological impacts of decommissioning transportation are small. No unique features or site-specific conditions are present at DCPP that would alter these NRC prior findings. Therefore, PG&E concludes that transportation impacts of DCPP decommissioning are small and thus bounded by the analysis in the Decommissioning GEIS and well within the baseline of current activities.

5.1.18. Irreversible and Irretrievable Commitment of Resources Section 4.3.18 in the Decommissioning GEIS generically concluded that the impacts of decommissioning on irreversible and irretrievable commitments of resources are small. Given that DCPP would be decommissioned to radiological standards for unrestricted release, the land will be available for other uses.

Furthermore, the materials and fuel consumed during DCPP decommissioning would be minor. The decommissioning of DCPP would generate radioactive waste and nonradiological waste requiring land disposal. Land devoted to radioactive waste disposal sites or industrial landfills was not within the scope of the Decommissioning GEIS because such commitments are addressed in the licensing documents for the disposal sites. Therefore, PG&E concludes that the impacts of DCPP decommissioning on irreversible and irretrievable commitments of resources would be small and thus bounded by the analysis in the Decommissioning GEIS.

5.2. Environmental Impacts of License Termination - NUREG-1496 A LTP for DCPP will be developed and submitted to NRC at least two years prior to the anticipated license termination date of April 2035 (as shown in the schedule in the SSDCE, Figure 5-1). The LTP will include a supplement to the DCPP PSDAR ER) describing any new information or significant environmental changes associated with the proposed termination activities. Although the LTP, including a supplement to the ER, need not be prepared and submitted until a minimum of two years prior to the anticipated license termination date, as required by 10 CFR 50.82(a)(9), the absence of any unique site-specific factors, significant groundwater contamination, unusual demographics, or impediments to achieving unrestricted release indicate that impacts resulting from DCPP license termination will be similar to those evaluated in NUREG-1496 (Reference 8).

Page 42 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 5.3. Discussion of Decommissioning in the Final Environmental Statement Applicable portions of the FES were addressed as noted in each of the topics previously summarized.

5.4. Additional Considerations The following considerations are relevant to concluding that DCPP decommissioning activities prior to license termination will not result in significant environmental impacts not previously reviewed:

continued compliance with radiological release and dose regulatory limits and adherence to plant procedures for monitoring and controlling release continued site access control to minimize or eliminate radiation release pathways to the public transport of radioactive waste in accordance with plant procedures, applicable federal regulations, and the requirements of the receiving facility continued adherence to ALARA principles during decommissioning and compliance with occupational dose limits continued compliance with applicable regulations and permit conditions for water withdrawals and wastewater discharges continued storage of SNF in accordance with license and plant procedures compliance with federal, state, and local regulations and permits for decommissioning activities

Additionally, NUREG-2157, Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel, found that the generic environmental impacts of ongoing SNF storage are small (Reference 15).

5.5. Conclusion PG&E evaluated the site-specific impacts anticipated from decommissioning of DCPP for each environmental resource area in the same manner and context as used by the NRC in its Decommissioning GEIS. This evaluation indicates that DCPP decommissioning operational area activities fall within the range of decommissioning activities considered by NRC in the Decommissioning GEIS.

There are no unique aspects of the plant or the expected decommissioning techniques that would invalidate the applicability to DCPP of the Decommissioning GEIS conclusions. The evaluation indicates that the impacts of DCPP decommissioning are bounded by the Decommissioning GEISs assessment for those environmental issues for which NRC made generic determinations.

For all areas, except cultural, historical, and archaeological resources, where a site-specific assessment was required, the anticipated impacts from DCPP decommissioning were determined to be small to moderate. The potential for moderate to large impacts were identified as part of the site-specific evaluation for cultural, historical, and archaeological resources. As PG&E is currently in the planning phase, decommissioning plans continue to evolve. In accordance with 10 CFR 50.82(a)(4)(i), as more detailed plans are developed, PG&E will verify that decommissioning activities that impact cultural, historical, and archaeological Page 43 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 resources are bounded by previously issued environmental impact statements or seek appropriate regulatory approval if needed prior to performing the activity.

With the exception noted above, the evaluation indicates that the potential impacts during decommissioning are bounded by the plants FES and Decommissioning GEIS.

6. References

1. Regulatory Guide 1.185, Standard Format and Content for Post-Shutdown Decommissioning Activities Report, Revision 1, dated June 2013 (ADAMS Accession No. ML13140A038).

2. PG&E Letter DCL-18-096, Certification of Permanent Cessation of Power Operations, dated November 27, 2018 (ADAMS Accession No. ML18331A553).

3. NUREG-0586, Supplement 1, Generic Environmental Impact Statement on Decommissioning of Nuclear Facilities, November 2002 (ADAMS Accession No. ML023470304 [Vol 1] and ML023470323 [Vol 2]).

4. EPRI Report No. 1011734, Maine Yankee Decommissioning Experience Report (1997 - 2004), 2005. Publicly accessible at: www.epri.com.

5. EPRI Report No. 1003025, Decommissioning Pre-Planning Manual, 2001.

Publicly accessible at: www.epri.com.

6. NUREG-1575, Multi-Agency Radiation Survey and Site Investigation Manual (MARSSIM), Revision 1, dated August 2000 (ADAMS Accession No. ML003761445).

7. Environmental Report, Post-Shutdown Decommissioning Activities Report, Diablo Canyon Power Plant, Revision 1, dated 2022.

8. NUREG-1496, Generic Environmental Impact Statement in Support of Rulemaking on Radiological Criteria for License Termination of NRC-Licensed Nuclear Facilities, dated July 1997 (ADAMS Accession No. ML042310492).

9. U.S. Atomic Energy Commission. Final Environmental Statement related to the Nuclear Generating Station Diablo Canyon Units 1 & 2. Directorate of Licensing, Washington, D.C. May 1973. (ADAMS Accession No. ML15043A481).

10. California State Lands Commission Lease No. PRC 9347.1 General Lease -

Industrial Use, dated June 28, 2016.

11. California Department of Fish and Wildlife. Threatened and Endangered Species: Endangered, Threatened, or Rare Plant List; Endangered, Page 44 of 45 Diablo Canyon Power Plant Post-Shutdown Decommissioning Activities Report, Revision 1 Threatened, or Rare Animal List; and Fully Protected Animals, dated January 2022. Accessed at: https://wildlife.ca.gov/Conservation/CESA.

12. U.S. Department of Energy. Threatened and Endangered Species Evaluation for Operating Commercial Nuclear Power Plants. Sackschewsky, M.R.

January 2004.

13. National Marine Fisheries Service. Endangered Species Act Section 7 Consultation, Biological Opinion, and Incidental Take Statement. National Oceanic and Atmospheric Administration. 2006.

14. National Marine Fisheries Service. Response to Request for List of Protected Species and Essential Fish Habitat Within the Area Under Evaluation for the Diablo Canyon Nuclear Power Plant, Units 1 and 2, License Renewal Application Review. National Oceanic and Atmospheric Administration, Southwest Region. May 10, 2010.

15. NUREG-2157, Volume 1, Generic Environmental Impact Statement for Continued Storage of Spent Nuclear Fuel, Final Report. Office of Nuclear Material Safety and Safeguards. September 2014. (ADAMS Accession No. ML14196A105).

16. NRC Letter, Diablo Canyon Nuclear Power Plant, Units 1 and 2 - Exemptions from the Requirements of 10 CFR Part 50, Sections 50.82(a)(8)(i)(A) and 50.82(a)(8)(ii) (EPID L-2018-LLE-0023), dated September 10, 2019 (ADAMS Accession No. ML19163A104).

Page 45 of 45

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