ML24102A199

Motion by Beyond Nuclear and the Sierra Club to Amend Their Contention 3 Regarding Failure to Consider Environmental Impacts of Climate Change

ML24102A199
Person / Time
Site:	North Anna
Issue date:	04/11/2024
From:	Curran D Beyond Nuclear, Harmon, Curran, Harmon, Curran, Spielberg & Eisenberg, LLP, Sierra Club
To:	Atomic Safety and Licensing Board Panel
SECY RAS
References
RAS 56989, 50-338-SLR-2, 50-339-SLR-2
Download: ML24102A199 (0)

Text

UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD

)

In the Matter of

)

Virginia Electric Power Co.

)

Docket Nos. 50-338/339 SLR North Anna Power Station Units 1 & 2

)

April 11, 2024

____________________________________)

MOTION BY BEYOND NUCLEAR AND THE SIERRA CLUB TO AMEND THEIR CONTENTION 3 REGARDING FAILURE TO CONSIDER ENVIRONMENTAL IMPACTS OF CLIMATE CHANGE I.

INTRODUCTION Pursuant to 10 C.F.R. § 2.309(c), Petitioners Beyond Nuclear, Inc. (Beyond Nuclear) and the Sierra Club, Inc. (Sierra Club) hereby seek leave to amend their Contention 3 to cite a recent report by the General Accounting Office (GAO): GAO-106326, Nuclear Power Plants:

NRC Should Take Actions to Fully Consider the Potential Effects of Climate Change (April 2024) (GAO-106326 or the GAO Report). A copy of GAO-106326 (GAO Report) is attached as Attachment A.1 The GAO prepared GAO-106326 in response to a Congressional request to review the climate resilience of energy infrastructures.2 The report focuses on nuclear power plants resilience to climate change and examines: (1) how climate change is expected to affect 1 Contention 3 was submitted on March 28, 2024 as part of Petitioners Hearing Request in this proceeding for review of Virginia Electric Power Co.s (VEPCOs) subsequent license renewal (SLR) application to the U.S. Nuclear Regulatory Commission (NRC or Commission).

See Hearing Request and Petition to Intervene by Beyond Nuclear and the Sierra Club (submitted March 28, 2924 and corrected April 8, 2024). Petitioners citations to the Hearing Request are to the Corrected Hearing Request). Contention 3 is supported by the Declaration of Jeffrey T.

Mitman (March 27, 2024) (Mitman Declaration).

2 Id. at 2.

2 nuclear power plants and (2) what actions NRC has taken to address the risks to nuclear power plants from climate change.3 To prepare its report, GAO officials interviewed NRC officials, officials of other related agencies such as the Federal Emergency Management Agency (FEMA) and the National Oceanic and Atmospheric Administration (NOAA), as well as representatives of the nuclear industry.4 In addition, GAO reviewed government data bases and reports on natural hazards and used these data to identify nuclear power plants that may be affected by natural hazards.5 Finally, GAO reviewed NRC regulations, guidance documents, and reports in order to examine NRCs actions to address risks to nuclear power plants from climate change.6 Section II below reproduces Contention 3 as initially submitted.Section III proposes language to amend the Basis Statement for Contention 3. In Section IV, Petitioners address the criteria in 10 C.F.R. § 2.309(c)(i)-(iii) for establishing good cause to submit contentions after the initial deadline for hearing requests.Section V contains Petitioners conclusion.

II.

CONTENTION 3 Contention 3 (Draft SEIS fails to address the effects of climate change on accident risk) states as follows:

A. Statement of Contention The Draft SEIS fails to satisfy NEPA or NRC implementing regulation 10 C.F.R. § 51.71 because it does not address the effects of climate change on accident risk. No such discussion can be found in Section 3.11.6.9 or Appendix F. To the contrary, the NRC asserts that the effects of climate change are outside the scope of the NRC staffs SLR review.26 In support of this assertion, the NRC claims to consider climate-related information in its licensing reviews and ongoing oversight.27 But this is exactly the kind 3 Id.

4 Id.

5 Id. at 2-4.

6 Id. at 4.

3 of blindered reasoning that was rejected in State of New York. The fact that NRC plans to address climate change risks in the future does not excuse the agency from addressing the risks as they are understood at this time. Only if the NRC can say that the effects of climate change are so small as to be remote and speculative can it avoid addressing those effects in its environmental review.28 And the Executive Branch of the U.S.

government, including CEQ and other federal agencies, has stated in no uncertain terms that climate change poses a current and future threat to critical infrastructure that should be addressed now in NEPA reviews and all other decision-making processes.29 Further, as set forth in Mr. Mitmans Declaration, the Draft SEIS failure to address climate change impacts on accident risk constitutes a significant deficiency because climate change demonstrably affects the frequency and intensity of some external events and therefore has the potential to significantly increase accident risks. Moreover, the frequency and intensity of climate change effects are increasing over time.30 Mr. Mitman also presents an illustration of how the reasonably foreseeable increase in the frequency and volume of flooding could significantly increase the risk of a serious accident at NAPS.31 This is just one example of the increased accident risk that can be reasonably expected due to climate change and that should be addressed in the Draft SEIS.

B.

Basis Statement Petitioners rely for this contention on Mr. Mitmans Declaration and the legal authorities cited above in Section III. In particular, Petitioners rely on State of New York v.

NRC, 681 F.3d at 478 (reasonable assurance findings do not excuse NEPA compliance unless probability of impacts is so low as to dismiss the potential consequences of such a failure.). In addition, Petitioners rely on the CEQ guidance discussed above in Section III.C. While this guidance is not binding on the NRC, it should be given substantial deference. State of New York v. NRC, 681 F.3d at 476 (citing Andrus v. Sierra Club, 442 U.S. 347, 358 (1979)).7 III.

REQUEST TO AMEND BASIS STATEMENT FOR CONTENTION Petitioners propose to amend Section B, the Basis Statement for Contention 3, by adding the following discussion of GAO-106326 that support Contention 3:

A recently-issued report by the GAO, GAO-106326, contains the following observations and conclusions that support Petitioners Contention 3:

7 Corrected Hearing Request at 16-17 (footnotes omitted),

4

• Based on available data, GAO-106326 confirms Petitioners assertion that the effects on climate change are significant and reasonably foreseeable for NAPS and other reactors:

o Forty-seven nuclear plants, including North Anna Power Station (NAPS), are located in areas with exposure to either Category 4 or 5 hurricane storm surge or high food hazards.8 NAPS is identified in the report as vulnerable to a high flood hazard.9 o Commercial nuclear power plants in the U.S., including NAPS, were licensed and built an average of 42 years ago, and weather patterns and climate-related risks to their safety and operations have changed since their construction.10 o The National Climate Assessment (NCA) predicts that climate change will exacerbate flooding and other climate change-related hazards.11 GAO finds that

[a]cross all regions of the United States, extremes, including heat, drought, flooding, wildfire, and hurricanes, are becoming more frequent and/or severe, with a cascade of effects in every part of the country.12

• GAO-106326 confirms Petitioners assertion that the NRC does not systematically address the effects of climate change on nuclear reactors in license renewal decisions:

8 Id. at 18.

9 Id. at 19, Figure 6.

10 Id. at 39.

11 Id. at 18. As discussed in GAO-106326 at page 3 and n.2, the NCA, most recently conducted in 2023, is a product of the U.S. Global Change Research Program.

12 Id. at 40.

5 o The NRC does not use climate projections data to identify and assess risk in either its initial licensing process or its license renewal process.13 o The NRC admits that it does not evaluate the safety significance of climate change in its licensing and license renewal reviews.14

• GAO-106326 confirms Petitioners assertion that the NRC did not fully consider the effects of climate change on nuclear reactors in its post-Fukushima safety reviews.15

• GAO-106326 demonstrates that NRCs refusal to consider the effects of climate change on reactor accident risks is not based on any technical evaluation of the reasonably foreseeable environmental impacts of climate change:

o NRC officials believe that historical data, rather than climate projections data, are reliable and sufficient for developing an adequate margin of safety for plants.16 o But NRC has not conducted an assessment to demonstrate this is the case.17

• The NRCs failure to fully address the effects of climate change on reactor safety in its regulatory process raises significant safety and environmental concerns:

Without incorporating the best available information into its licensing and oversight processes, it is unclear whether the safety margins for nuclear power plants established during the licensing period - in most cases over 40 years ago -

are adequate to address the risks that climate change poses to plants.18 13 Id. at 34-36. See also id. at 39 (NRC does not use climate projections data to identify and assess risk as part of the safety reviews it conducts or the probabilistic risk assessments it reviews during the initial licensing process.).

14 Id. at 34-36.

15 Id. at 36.

16 Id. See also id. at 40 (response to NRC comments on the draft report).

17 Id.

18 Id. at 39.

6 While GAO-106326 describes this concern in terms of reactor safety rather than environmental impacts, it is relevant to the NRCs environmental review because accident risks are a lawful subject of that review.19 Further, as GAO notes, the NRCs statutory mandate includes protection of the environment.20 As observed by GAO, however, the only aspect of climate change that is addressed in the NRCs environmental reviews for license renewal is the effect of greenhouse emissions associated with the life cycle of nuclear reactors.21 IV.

PETITIONERS SATISFY THE GOOD CAUSE STANDARD FOR THIS FILING.

Petitioners respectfully submit that they satisfy the good cause standard in 10 C.F.R. § 2.309(c)(i)-(iii) for their amended contention as follows:

(i)

The information upon which the filing is based was not previously available.

The GAO Report on which Petitioners base their amended contention was not available until April 2, 2024. Petitioners are unaware of any previous review, prepared by a federal government agency that is independent of the NRC, that specifically addressed the effects of climate change on nuclear reactors and whether the NRC has addressed those effects in its licensing and re-licensing decisions.

(ii)

The information upon which the filing is based is materially different from information previously available.

The information presented in GAO-106326 is materially different from information previously available. As discussed above, Petitioners are unaware of any previous review, prepared by a federal government agency that is independent of the NRC, that specifically 19 See State of New York, 681 F.3d at 478.

20 Id. at 1.

21 Id. at 36 n.54.

7 addressed the effects of climate change on nuclear reactors and whether the NRC has addressed those effects in its licensing and re-licensing decisions.

(iii)

The filing has been submitted in a timely fashion based on the availability of the subsequent information.

As established in the Atomic Safety and Licensing Boards Initial Prehearing Order (April 4, 2024), a contention submitted within thirty days after the information on which it is based becomes available is considered timely.22 GAOs website shows that GAO-106326 was released to the public on April 2, 2024.23 Therefore Petitioners Amended Contention3 has been submitted in a timely fashion.

V.

CONCLUSION For the foregoing reasons, Petitioners request to amend their Contention 3 should be granted.

Respectfully submitted,

__/signed electronically by/___

Diane Curran Harmon, Curran, Spielberg, & Eisenberg, L.L.P.

1725 DeSales Street N.W., Suite 500 Washington, D.C. 20036 240-393-9285 dcurran@harmoncurran.com April 11, 2024 22 Id. at 4 n.10.

23 https://www.gao.gov/reports-testimonies?page=1.

ATTACHMENT A GAO-106326, Nuclear Power Plants: NRC Should Take Actions to Fully Consider the Potential Effects of Climate Change (April 2024)

NUCLEAR POWER PLANTS NRC Should Take Actions to Fully Consider the Potential Effects of Climate Change Report to Congressional Requesters April 2024 GAO-24-106326 United States Government Accountability Office

United States Government Accountability Office Highlights of GAO-24-106326, a report to congressional requesters April 2024 NUCLEAR POWER PLANTS NRC Should Take Actions to Fully Consider the Potential Effects of Climate Change What GAO Found Climate change is expected to exacerbate natural hazardsincluding heat, drought, wildfires, flooding, hurricanes, and sea level rise. In addition, climate change may affect extreme cold weather events. Risks to nuclear power plants from these hazards include loss of offsite power, damage to systems and equipment, and diminished cooling capacity, potentially resulting in reduced operations or plant shutdowns.

Examples of Natural Hazards that May Pose Risks to Nuclear Power Plants The Nuclear Regulatory Commission (NRC) addresses risks to the safety of nuclear power plants, including risks from natural hazards, in its licensing and oversight processes. Following the tsunami that led to the 2011 accident at Japans Fukushima Dai-ichi nuclear power plant, NRC took additional actions to address risks from natural hazards. These include requiring safety margins in reactor designs, measures to prevent radioactive releases should a natural hazard event exceed what a plant was designed to withstand, and maintenance of backup equipment related to safety functions.

However, NRCs actions to address risks from natural hazards do not fully consider potential climate change effects. For example, NRC primarily uses historical data in its licensing and oversight processes rather than climate projections data. NRC officials GAO interviewed said they believe their current processes provide an adequate margin of safety to address climate risks.

However, NRC has not conducted an assessment to demonstrate that this is the case. Assessing its processes to determine whether they adequately address the potential for increased risks from climate change would help ensure NRC fully considers risks to existing and proposed plants. Specifically, identifying any gaps in its processes and developing a plan to address them, including by using climate projections data, would help ensure that NRC adopts a more comprehensive approach for assessing risks and is better able to fulfill its mission to protect public health and safety.

View GAO-24-106326. For more information, contact Frank Rusco at (202) 512-3841 or ruscof@gao.gov.

Why GAO Did This Study NRC licenses and regulates the use of nuclear energy to provide reasonable assurance of adequate protection of public health and safety, to promote the common defense and security, and to protect the environment. Like all energy infrastructure, nuclear power plants can be affected by disruptions from natural hazards, some of which are likely to be exacerbated by climate change. Most commercial nuclear plants in the United States were built in the 1960s and 1970s, and weather patterns and climate-related risks to these plants have changed since their construction.

GAO was asked to review the climate resilience of energy infrastructure. This report examines (1) how climate change is expected to affect nuclear power plants and (2) NRC actions to address risks to nuclear power plants from climate change. GAO analyzed available federal data and reviewed regulations, agency documents, and relevant literature. GAO interviewed officials from federal agencies, including NRC, the Department of Energy, and the National Oceanic and Atmospheric Administration, and knowledgeable stakeholders from industry, academia, and nongovernmental organizations. GAO also conducted site visits to two plants.

What GAO Recommends GAO is making three recommendations, including that NRC assess whether its existing processes adequately address climate risks and develop and implement a plan to address any gaps identified. NRC said the recommendations are consistent with actions that are either underway or under development.

Page i GAO-24-106326 Nuclear Power Plants Letter 1

Background

5 Climate Change Is Expected to Exacerbate Natural Hazards That Pose Risks to Nuclear Power Plants 13 NRCs Actions to Address Risks to Nuclear Power Plants from Natural Hazards Do Not Fully Consider the Potential Effects of Climate Change 27 Conclusions 39 Recommendations for Executive Action 40 Agency Comments and Our Evaluation 40 Appendix I Objectives, Scope, and Methodology 42 Appendix II Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise 49 Appendix III Nuclear Power Plant Exposure to Selected Natural Hazards 54 Appendix IV Comments from the Nuclear Regulatory Commission 65 Appendix V GAO Contact and Staff Acknowledgments 67 Tables Table 1: Potential Exposure to Current and Future Hazards at Operating Nuclear Power Plants 55 Table 2: Potential Exposure to Current and Future Hazards at Shutdown Nuclear Power Plants 62 Figures Figure 1: Map of Operating and Shutdown Nuclear Power Plants by U.S. Census Region 6

Contents

Page ii GAO-24-106326 Nuclear Power Plants Figure 2: Nuclear Power Plant Components and Operations for a Pressurized Water Reactor 8

Figure 3: Measures Consistent with the Nuclear Regulatory Commissions (NRC) Defense-in-Depth Approach 12 Figure 4: Examples of Natural Hazards that May Pose Risks to Nuclear Power Plants 13 Figure 5: Nuclear Power Plants Located in Areas with Exposure to No/Low, Moderate, and High/Very High Wildfire Hazard Potential 17 Figure 6: Nuclear Power Plants Located in Areas with High and Moderate Flood Hazard 20 Figure 7: Nuclear Power Plants Located in Areas with Exposure to Storm Surges from Category 4 and Category 5 Hurricanes 22 Figure 8: Nuclear Power Plants in the National Oceanic and Atmospheric Administration (NOAA) Coastal Regions and Projected Sea Level Rise in 2050 24 Figure 9: Timeline of Selected Nuclear Regulatory Commission (NRC) and Industry Actions after the Fukushima Dai-ichi Accident in 2011 30 Figure 10: Examples of the Diverse and Flexible Coping Strategies (FLEX) and Strategic Alliance for FLEX Emergency Response (SAFER) Center Equipment 34

Page iii GAO-24-106326 Nuclear Power Plants Abbreviations FLEX Diverse and Flexible Coping Strategies NCA National Climate Assessment NOAA National Oceanic and Atmospheric Administration NRC Nuclear Regulatory Commission POANHI Process for the Ongoing Assessment of Natural Hazard Information SAFER Strategic Alliance for FLEX Emergency Response This is a work of the U.S. government and is not subject to copyright protection in the United States. The published product may be reproduced and distributed in its entirety without further permission from GAO. However, because this work may contain copyrighted images or other material, permission from the copyright holder may be necessary if you wish to reproduce this material separately.

Page 1 GAO-24-106326 Nuclear Power Plants 441 G St. N.W.

Washington, DC 20548 April 2, 2024 The Honorable Joe Manchin III Chairman Committee on Energy and Natural Resources United States Senate The Honorable Tom Carper Chairman Committee on Environment and Public Works United States Senate Since 1990, nuclear energy has accounted for about 20 percent of the electricity generated in the United States. In 2022, nuclear energy provided nearly half of our nations carbon-free electricity, making it the largest domestic source of carbon-free energy. Nuclear power plants emit no carbon dioxide during operations and, unlike many sources of renewable energy, typically operate around the clock, producing on average above 90 percent of their generating capacity.

However, nuclear power plants can be affected by natural hazards including heat, drought, wildfires, flooding, hurricanes, sea level rise, and extreme cold weather eventssome of which are expected to be exacerbated by climate change, with effects varying by region. Most commercial nuclear power plants in the United States were licensed and built in the 1960s and 1970s, and the risks to plants safety and operations from natural hazards have changed since their construction.

The Nuclear Regulatory Commission (NRC) is responsible for regulating the civilian use of radioactive materials to promote the nations common defense and security, provide reasonable assurance of adequate protection of public health and safety, and protect the environment. As electricity demand in the United States is expected to continue to grow over the coming decades, Congress and others are turning to nuclear power as one means of meeting the increased demand while reducing carbon emissions. For example, in recent years, Congress has provided incentives for the continued operation of existing nuclear power plants Letter

Page 2 GAO-24-106326 Nuclear Power Plants and for the construction of new plants, which, if licensed, could operate into the next century.1 You asked us to review the climate resilience of energy infrastructure.

This report focuses on nuclear power plants resilience to climate change and examines (1) how climate change is expected to affect nuclear power plants and (2) what actions NRC has taken to address the risks to nuclear power plants from climate change.

To address both objectives, we interviewed officials from NRC headquarters and its four regional offices, NRC resident inspectors, and officials from the Department of Energyincluding the Office of Nuclear Energy and the Idaho National Laboratorythe Federal Energy Regulatory Commission, the Federal Emergency Management Agency, the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Forest Service. In addition, we interviewed a nongeneralizable sample of nine stakeholders knowledgeable about nuclear power plant operations and safety, climate change, and resilience measures. We also visited two selected nuclear power plantsPalo Verde Nuclear Generating Station in Buckeye, Arizona, and Turkey Point Nuclear Generating Station in Homestead, Floridaand interviewed plant staff and NRC resident inspectors at these plants. We selected these plants because of their exposure to a variety of natural hazards that may be exacerbated by climate change and regional diversity. Findings from selected stakeholder interviews and site visits are not generalizable to all stakeholders and sites.

To examine how climate change is expected to affect nuclear power plants, we conducted a literature review of articles and reports related to the effects of climate change on nuclear power plants. On the basis of this method, we identified and used 36 articles to support the findings in our report. We also reviewed the fourth and fifth U.S. Global Change 1NRC has efforts underway to support the licensing of advanced nuclear reactors nuclear fission reactors that may offer significant improvements over the most recent generation of nuclear fission reactors and may involve first-of-a-kind designswhich, according to NRC officials, contribute to climate resilience by supporting an alternative to fossil-fuel-based power plants. For more information on NRCs licensing of advanced nuclear reactors, see GAO, Nuclear Power: NRC Needs to Take Additional Actions to Prepare to License Advanced Reactors, GAO-23-105997 (Washington, D.C.: July 27, 2023).

Page 3 GAO-24-106326 Nuclear Power Plants Research Programs National Climate Assessments (NCA),2 federal data on natural hazards, and prior GAO reports.

Additionally, we identified and obtained national-level data sets from relevant federal agencies for six of the seven natural hazards identified by the NCA and our literature review as likely to be exacerbated by climate change: extreme heat, extreme cold, wildfires, flooding, storm surge from hurricanes, and sea level rise.3 For heat, cold, and sea level rise, we used data that are based on climate scenarios. For heat and cold, we analyzed the projected exposure of nuclear power plants to those hazards.4 For wildfires, hurricane storm surge, and flooding, we used data that are based on current and past conditions.5 We assessed the reliability of the data sources used and found the data to be sufficiently reliable for the purposes of our reporting objectives. For more detailed information on our scope and methodology, and the steps we took to assess the reliability of the data used in this report, see appendix I. For more detail on data sources used in this report, see appendix II.

In addition, we obtained NRC data on the location of all 54 operating U.S.

nuclear power plants as well as on the 21 shutdown nuclear power plants 2U.S. Global Change Research Program, Fifth National Climate Assessment, (Washington, D.C.: 2023); U.S. Global Change Research Program, Impacts, Risks, and Adaptation in the United States: Fourth National Climate Assessment, vol. II (Washington, D.C.: 2018).

3To identify and select national-level data sets, we used information from the NCA. The fifth NCA was released on November 14, 2023, after we had obtained and analyzed the hazard data sets. We reviewed relevant sections from the fifth NCA and did not identify major differences in the predicted or projected trends for the selected natural hazards. We did not analyze drought data because we were unable to identify national-level geospatial data that was both relevant to nuclear power plants and sufficiently reliable for our purposes.

4To analyze projected exposure to heat and cold hazards, we used data from the fourth NCA on the projected exposure to maximum and minimum temperatures by the midcentury (i.e., 2036-2065). We selected data using the projected change by the midcentury time frame under both a low-and high-emission scenario to show the range of potential projected change to selected natural hazards. The midcentury time frame was selected because it captures potential hazard effects during the period in which most U.S.

nuclear power plants are likely to remain operational.

5To analyze exposure to floods, we used 2023 data from the Federal Emergency Management Agency that categorize flood exposure as a high, moderate, minimal, other, or unknown flood hazard. To analyze exposure to hurricane storm surge, we used NOAA data on storm surge exposure from Category 1 hurricanes (the lowest possible category) and Category 4 or 5 hurricanes (the highest possible categories) to show a range of potential climate change effects. To analyze exposure to wildfires, we used 2023 data from the U.S. Forest Service on wildfire hazard potential.

Page 4 GAO-24-106326 Nuclear Power Plants that have spent nuclear fuel stored onsite in spent fuel pools or in dry cask storage.6 We analyzed these data using mapping software to identify nuclear power plants located in areas that may be affected by selected natural hazards. We determined that the data were sufficiently reliable for the purposes of our reporting objectives.

To examine NRCs actions to address risks to nuclear power plants from climate change, we reviewed relevant laws and regulations; agency guidance and documents, including NRCs 2022-2026 Strategic Plan; NRC office instructions; and the NRC inspection manual on adverse weather protection.7 We also reviewed GAOs Standards for Internal Control in the Federal Government.8 We conducted this performance audit from November 2022 to April 2024 in accordance with generally accepted government auditing standards.

Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe that the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives.

6When a company decides to shut down a nuclear power plant permanently, the facility must be decommissioned by safely removing it from service and reducing residual radioactivity to a level that permits release of the property and termination of the operating license. NRC regulates the decommissioning a nuclear power plant and any spent nuclear fuel that will remain on site. See 10 C.F.R. pt. 20, subpt. E; 10 C.F.R. §§ 50.75, 50.82, 51.53, 51.95. For the purposes of this report, we use the term shutdown to refer to plants at various stages of decommissioning, including those in the process of decommissioning and those already decommissioned, with spent nuclear fuel stored onsite. Spent nuclear fuel is the fuel that has been removed from commercial nuclear power reactors after it has been used to produce electricity. Spent nuclear fuel is initially stored immersed in pools of water designed to cool and isolate it from the environment. Water circulates in the pools to remove the heat generated from the radioactive decay. Industry practice has been to store the spent nuclear fuel in these pools for at least 5 years or until the fuel has cooled enough to be transferred to dry cask storage. Dry cask storage consists of a steel canister that holds the fuel assemblies, protected by an outer cask made of steel and concrete designed to cool the fuel and provide shielding from its radiation. We also obtained data on the location of the two Strategic Alliance for FLEX Emergency Response (SAFER) centers that maintain emergency equipment that can be provided to plants as a backup to the plants onsite primary backup equipment.

7NRC, Strategic Plan Fiscal Years 2022-2026, NUREG-1614, Vol. 8 (Washington, D.C.:

April 2022). See also, NRC, Inspection Manual: Adverse Weather Protection, Inspection Procedure 71111, Attachment 01 (Washington, D.C.: Jan. 1, 2018).

8GAO, Standards for Internal Control in the Federal Government, GAO-14-704G (Washington, D.C.: Sept. 10, 2014).

Page 5 GAO-24-106326 Nuclear Power Plants Private companies own nearly all nuclear power plants in the United States. As of August 2023, the United States had 93 operating commercial nuclear reactors with an average age of about 42 years old, according to the U.S. Energy Information Administration. These reactors are located at 54 nuclear power plants in 28 states.9 In addition, as of July 2023, there were 21 shutdown plants that have spent nuclear fuel stored onsite in spent fuel pools or in dry casks. See figure 1 for the locations and regions of operating and shutdown nuclear power plants by U.S.

Census region.

9According to the U.S. Energy Information Administration, nuclear reactors are machines that contain and control nuclear chain reactions while releasing heat at a controlled rate. A nuclear power plant uses the heat that a nuclear reactor produces to turn water into steam, which then drives turbine generators that generate electricity.

Background

The Nuclear Power Industry and U.S. Plant Operations

Page 6 GAO-24-106326 Nuclear Power Plants Figure 1: Map of Operating and Shutdown Nuclear Power Plants by U.S. Census Region Note: This map includes 75 U.S. nuclear power plants54 operating plants and 21 shutdown plants with spent nuclear fuel onsite.

Nuclear reactors rely on technologies to initiate and control chain reactions that produce heat through a physical process called fission whereby atoms are split to release energy. All commercial nuclear power reactors in the United States use uranium as fuel and are light water reactors, which means they use water as both a coolant and moderator to

Page 7 GAO-24-106326 Nuclear Power Plants serve critical safety and operations functions.10 Nuclear power plants use water during normal operations to absorb the heat that is left over after making electricity and to cool the equipment and buildings used in generating that electricity. In the event of an accident, nuclear power plants also need water to remove the heat produced by the reactor core, even when it is temporarily shut down. Water is also used to cool spent fuel once it is removed from the reactor core. Because light water reactors rely on water for key safety and operational functions, nuclear power plants are typically located next to lakes, rivers, or oceans.

There are two types of light water reactors in the United States pressurized water reactors and boiling water reactors. Pressurized water reactors, the predominant type of light water reactor in the United States, use steam generators to transfer the heat created by fission from the primary coolant loop to the secondary coolant loop, creating steam in the secondary loop that spins a turbine and generates electricity. Boiling water reactors, which constitute a third of the operating reactors in the United States, do not use steam generators or have secondary loops.

Instead, the steam is generated directly inside the reactor vessel. See figure 2 for an overview of a nuclear power plants components for a pressurized water reactor.

10The commercial nuclear power reactors currently operational in the United States are known as light water reactors, meaning reactors that use ordinary water to cool and moderate the reactor, as opposed to heavy water, which contains deuterium, an isotope of hydrogen.

Page 8 GAO-24-106326 Nuclear Power Plants Figure 2: Nuclear Power Plant Components and Operations for a Pressurized Water Reactor Note: This illustration depicts a pressurized water reactor, the predominant reactor type in the United States. Boiling water reactors, which constitute a third of the operating reactors in the United States, do not use steam generators or have secondary loops. Boiling water reactors boil water directly inside the reactor vessel to produce steam.

To operate the cooling pumps and other systems that manage the water that reactors rely on for key safety and operational functions, nuclear plants need a reliable source of power. Nuclear power plants typically rely on the electricity grid to which the plant is connected for offsite power.11 11As we reported in 2021, climate change is expected to affect every aspect of the electricity gridfrom generation, transmission, and distribution, to demand for electricity.

We found that power outages can have significant cascading effects on critical sectors and electric service disruptions can significantly affect the reliability of other parts of the energy sector. These losses are of special concern because outages caused by climate effects can be widespread and affect large geographic areas all at once, according to the Department of Energy. GAO, Electricity Grid Resilience: Climate Change Is Expected to Have Far-Reaching Effects and DOE and FERC Should Take Actions, GAO-21-346 (Washington, D.C.: March 5, 2021).

Page 9 GAO-24-106326 Nuclear Power Plants However, if a plant loses access to offsite power, it must rely on backup power sources, such as diesel generators, to power cooling pumps. The loss of power and ability to pump cooling water can have a significant adverse impact on a plants ability to safely shut down and maintain safe shutdown conditions. This could result in damage to a reactors core and potentially release radiological material into the environment.

NRC is an independent federal agency, headed by five commissioners, responsible for permitting the construction and licensing of commercial nuclear power reactors and regulating and overseeing their security and safe operation.12 NRC can issue a license to operate a nuclear power reactor for up to 40 years and can renew a license for up to 20 additional years. A renewed license may be subsequently renewed for up to another 20 years, allowing a reactor to operate for up to a total of 80 years. As of December 2023, NRC had issued subsequent license renewals for six reactors at three nuclear power plants in the United States.13 Spent nuclear fuel may remain onsite long after a plant shuts down.14 As part of NRCs process for issuing construction permits and licenses for nuclear power plants, agency staff conduct safety and environmental reviews. As part of the safety review, NRC reviews a plants design to ensure it meets the technical specifications required for the safe operation of the plant. Specifically, NRCs reactor design criteria require that important safety systems, structures, and components are designed to withstand the effects of natural hazards, including climate-related hazards 12NRCs mission is to regulate the civilian use of radioactive materials, to provide reasonable assurance of adequate protection of public health and safety, to promote the common defense and security, and to protect the environment. As such, any new requirements that the agency imposes on commercial nuclear plants must meet this standard, according to NRC officials.

13NRC issued subsequent license renewals to Turkey Point Units 3 and 4 in December 2019; Peach Bottom Units 2 and 3 in March 2020; and Surry Units 1 and 2 in May 2021.

14The United States does not have a consolidated storage facility or repository where plants can send their spent fuel during operations or after a plant shuts down. GAO, Commercial Spent Nuclear Fuel: Congressional Action Needed to Break Impasse and Develop a Permanent Disposal Solution, GAO-21-603 (Washington, D.C.: Sept. 23, 2021).

NRCs Role

Page 10 GAO-24-106326 Nuclear Power Plants such as hurricanes and floods, without losing the ability to perform their safety functions.15 License applicants are responsible for ensuring their plants are protected against natural hazards by assessing the hazards that may affect their plants and designing the plants to withstand those hazards. NRC is responsible for reviewing plant and reactor designs and comparing the design limits for natural hazards with those found in applicants hazard assessments, which consider the characteristics of the plants geographic location. Once a nuclear power plant is licensed and operational, NRC conducts regular inspections of the plants systems and ensures that the licensee is operating in accordance with its license. If a plant experiences external conditions that exceed the limiting conditions for operation, the licensee is required to either shut the reactor down, take remedial actions as permitted in its license, or request a license amendment or enforcement discretion from NRC to continue operations.16 NRC also regulates the decommissioning of nuclear power plants, which means safely removing nuclear power plants from service by reducing residual radioactivity to a level that permits the release of the property and termination of the license.17 NRC uses conservatism, safety margins, and defense-in-depth to implement regulatory requirements for the design, construction, maintenance, operation, and decommissioning of nuclear power plants to prevent and mitigate accidents that could release radiation or hazardous 1510 C.F.R. Part 50, Appendix A, General Design for Nuclear Power Plants, Criterion 2 Design Bases for Protection Against Natural Phenomena. According to an NRC document, all currently operating reactors were licensed to meet the intent of the General Design Criteria, which include General Design Criterion 2. See also 10 C.F.R. §§ 50.34, 52.79 (detailing safety analysis and design requirements for a license application).

16Limiting conditions for operation are the lowest functional capability or performance levels of equipment required for safe operation of the plant. 10 C.F.R. § 50.36(c)(2)(i). If the limiting conditions are exceeded by an extreme weather event, licensees can request the following from NRC: a temporary enforcement discretion for a brief period to allow them to continue operating despite the exceedance; a temporary license amendment to revise the limiting conditions for a specified period (e.g., 1-3 months); or a permanent license amendment to change the technical specifications.

17The NRC ensures that safety requirements are being met throughout the decommissioning process by reviewing decommissioning or license termination plans, conducting inspections, monitoring to ensure that radioactive contamination is reduced or stabilized, and issuing permits for spent nuclear fuel that will remain on site after license termination. See 10 C.F.R. pt. 20, subpt. E; 10 C.F.R. §§ 50.75, 50.82, 51.53, 51.95.

NRCs Regulatory Approach

Page 11 GAO-24-106326 Nuclear Power Plants materials. According to agency documents and NRC officials we interviewed, the approach can be described as follows:

Conservatism, for example, includes the consideration of the most severe natural phenomena that have been historically reported for a nuclear power plant site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data have been accumulated.18 Safety margins are the extra capacity factored into the design of a structure, system, or component so that it can cope with conditions beyond what is expected as a way to compensate for uncertainty.19 Defense-in-depth includes multiple independent and redundant layers of defense to compensate for potential human and mechanical failures so that no single layer, no matter how robust, is exclusively relied upon. Defense-in-depth includes the use of access controls, physical barriers, redundant and diverse key safety functions, and emergency response measures (see fig. 3).20 1810 C.F.R. Part 50, Appendix A, General Design Criterion 2, Design Bases for Protection Against Natural Phenomena. See also, NRC, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision-Making, NUREG-1855 (Washington, D.C.: March 2017).

19NRC, Glossary of Risk-Related Terms in Support of Risk-Informed Decision-Making, NUREG-2122 (Washington, D.C.: Nov. 2013).

20For more information on defense-in-depth, see NRC, Historical Review and Observations of Defense-in-Depth, NUREG/KM-0009 (Washington, D.C.: April 2016).

Page 12 GAO-24-106326 Nuclear Power Plants Figure 3: Measures Consistent with the Nuclear Regulatory Commissions (NRC)

Defense-in-Depth Approach

Page 13 GAO-24-106326 Nuclear Power Plants Climate change is expected to exacerbate natural hazardsincluding heat, drought, wildfires, flooding, hurricanes, and sea level rise. In addition, climate change may affect extreme cold weather events.21 These natural hazards pose risks to nuclear power plants (see fig. 4).

Figure 4: Examples of Natural Hazards that May Pose Risks to Nuclear Power Plants Note: The potential risks to nuclear power plants from these hazards include a loss of offsite power, diminished cooling capacity, flood damage, and reduced operations or temporary plant shutdowns.

The loss of offsite power is a complete loss of electrical power from the grid to a nuclear power plant.

The loss can decrease a plants ability to maintain safe shutdown conditions. Diminished cooling capacity refers to any impact which reduces a plants ability to cool reactor or fuel cycle components and can result in a temporary plant shutdown.

21According to the NCA, climate change has driven increases in the frequency and severity of some extreme weather events. For example, climate change caused Hurricane Harveys rainfall to be an estimated 15 and 20 percent heavier than it would have been without human-caused warming. However, researchers disagree about some climate impacts. For example, whereas emerging research suggests that the frequency of cold-weather events and heavy snowfall may be increasing because of warming Arctic temperatures, there is some disagreement in the research community regarding this projection.

Climate Change Is Expected to Exacerbate Natural Hazards That Pose Risks to Nuclear Power Plants

Page 14 GAO-24-106326 Nuclear Power Plants According to our analysis of NCA and U.S. Forest Service data, all 75 operating and shutdown U.S. nuclear power plants are located in areas where climate change is expected to exacerbate heat, drought, wildfires, or all three.

Heat and drought. Heat and drought pose risks to nuclear power plants because they can affect the water used for cooling. Specifically, higher-than-usual ambient air temperatures may increase the temperature of water used for cooling. Drought can also reduce the supply of cooling water. If a plant has an insufficient supply of cooling water or its cooling water approaches or exceeds the maximum allowable temperature for cooling certain reactor components, a licensee may need to temporarily limit or stop operations to ensure plant safety. Higher temperatures in the bodies of water into which nuclear power plants discharge cooling water may also require a plant to limit or temporarily stop operations to comply with laws designed to protect aquatic ecosystems and wildlife.22 In addition, high temperatures can also degrade the performance or cause failure of pumps and other equipment, reduce the lifetime of plant components, and reduce the overall efficiency of power plants. Warmer temperatures may also increase levels of certain algae or other biological material which can block cooling water systems and lead to reduced production or a temporary plant shutdown.

22Some plants that discharge cooling water into rivers or lakes are subject to environmental requirements. These requirements could force a power plant to shut down or reduce power generation. For example, in 2007, 2010, and 2011, the Tennessee Valley Authority had to reduce power output from its Browns Ferry Nuclear Power Plant in Alabama because river temperatures were too high to receive discharge water from the plant without posing ecological risks.

Heat, Drought, and Wildfires Pose Risks to Nuclear Power Plants, and Climate Change Is Expected to Exacerbate These Hazards, Particularly in the South and Southwest

Page 15 GAO-24-106326 Nuclear Power Plants All operating and shutdown nuclear power plants are located in areas where climate change is projected to increase measures of heat, including daily and average maximum temperature, according to our analysis of NCA and NRC data. The effects of climate change on maximum temperatures are projected to be most severe in the South, where one-third of the plants are located.23 The plants in the South are projected to experience an annual average of from 21 to 31 days with higher maximum temperatures than historical high temperatures. In addition, according to the NCA, climate change is expected to increase drought intensity in some regions, specifically in the Southwest, where two operating and four shutdown nuclear power plants are located.

23Of the 25 plants in the South, 24 are operational and one is shutdown.

Heat and Drought at Turkey Point Nuclear Generating Station According to the Nuclear Regulatory Commission (NRC) and Turkey Point Nuclear Generating Station officials, in 2014, extended drought conditions and high algae content caused the cooling water for the Turkey Point Generating Station to exceed its maximum allowable temperature in its license. NRC approved the licensees requests to not enforce the temperature requirement for the plants cooling water for a limited period.

Later, NRC granted the licensee a permanent license amendment that raised the maximum allowable cooling water temperature for the plant from 100 degrees to 104 degrees Fahrenheit.

High temperatures and drought conditions at Turkey Point Nuclear Generating Station potentially created risks to local drinking water sources when decreased water levels and increased evaporation rates led to higher salinity in the cooling canals. Higher salinity levels made the water denser, causing it to sink below the canals that contain it. This could have led to intrusion of higher salinity water into the areas of the Biscayne Aquifer, a source of drinking water for the Miami-Dade area.

To mitigate these risks, the licensee constructed a series of wells to decrease the water salinity in the cooling canals.

Well used to adjust salinity in the Turkey Point Nuclear Generating Stations cooling canals Sources: Interviews with plant personnel at the Turkey Point Nuclear Generating Station, and review of NRC documents; GAO (photo). l GAO-24-106326

Page 16 GAO-24-106326 Nuclear Power Plants Wildfire. According to the NCA, increased heat and drought contribute to increases in wildfire frequency, and climate change has contributed to unprecedented wildfire events in the Southwest. The NCA projects increased heatwaves, drought risk, and more frequent and larger wildfires. Wildfires pose several risks to nuclear power plants, including increasing the potential for onsite fires that could damage plant infrastructure, damaging transmission lines that deliver electricity to plants, and causing a loss of power that could require plants to shut down. Wildfires and the smoke they produce could also hinder or prevent nuclear power plant personnel and supplies from getting to a plant.

According to our analysis of U.S. Forest Service and NRC data, about 20 percent of nuclear power plants (16 of 75) are located in areas with a high or very high potential for wildfire.24 More specifically, more than one-third of nuclear power plants in the South (nine of 25) and West (three of eight) are located in areas with a high or very high potential for wildfire (see fig.

5).

24The U.S. Forest Service maps wildfire hazard potential based on landscape conditions and other observations. These maps include an index of wildfire hazard potential for the United States, based on, among other factors, annual burn probabilities and the potential intensity of large fires. The wildfire potential index is a relative ranking. The U.S. Forest Service categorizes the wildfire hazard potential index into five classes: very low, low, moderate, high, and very high. The U.S. Forest Service designates as high those areas with wildfire hazard potential index from the 85th to the 95th percentile, and as very high those areas above the 95th percentile. For this analysis, we combined the high and very high wildfire hazard potential categories; we did not identify the number of facilities in each of these categories separately. Of the 16 plants with high or very high potential for wildfire, 12 are operating and four are shutdown.

Page 17 GAO-24-106326 Nuclear Power Plants Figure 5: Nuclear Power Plants Located in Areas with Exposure to No/Low, Moderate, and High/Very High Wildfire Hazard Potential Note: To determine if a plant is located in an area with wildfire hazard potential, we identified overlap between a 0.5-mile radius around nuclear power plant coordinates provided by the Nuclear Regulatory Commission and wildfire hazard potential data. Overlap indicates that a facility is located in an area that may be affected by the selected hazard. We used the U.S. Forest Service Wildfire Hazard Potential Map to show exposure to wildfire hazard potential. The U.S. Forest Service categorizes the wildfire hazard potential index into five classes of very low, low, moderate, high, and very high. We analyzed the moderate, high, and very high wildfire potential layers, and combined results for the high/very high layers. No/low refers to plants that are not located in an area with wildfire potential of moderate, high, or very high, based on the U.S. Forest Service Wildfire Hazard Potential Map. See appendix I for more details on our data analysis. We previously reported that the primary intended use of the wildfire hazard potential map is to identify priority areas for hazardous fuels treatments from a broad, national-to regional-scale perspective. This analysis does not account for any protective measures plants may have taken to mitigate the risk of selected natural hazards.

Page 18 GAO-24-106326 Nuclear Power Plants Appendix III provides additional details of exposure to heat and wildfire hazard potential in areas where nuclear power plants are located.

According to our analysis of NOAA and NRC data, about 63 percent of nuclear power plants (47 of 75) are located in areas with exposure to either Category 4 or 5 hurricane storm surge or high flood hazard, and nine are located on a coastline, where NOAA projects a range of sea level increases.25 In addition, 20 percent of nuclear power plants (15 of

75) are located in areas with exposure to both Category 4 or Category 5 hurricane storm surge and high flood hazard. The NCA predicts that climate change will exacerbate all three hazards.

25To identify coastal plant locations, we used nuclear power plant coordinates from NRC and added a 0.5-mile radius around NRCs plant coordinates as a proxy for an average size nuclear power plant. Coastal plants were those with a radius that intersected with or beyond the coastline.

Flooding, Hurricanes, and Sea Level Rise Pose Risks to Nuclear Plants, and Climate Change Is Expected to Exacerbate These Hazards, Particularly in Coastal Regions

Page 19 GAO-24-106326 Nuclear Power Plants Flooding. Flooding could pose risks to nuclear power plants by, among other things, diminishing a plants cooling capacity. Flooded roads could prevent personnel, equipment, and supplies from reaching a plant.

Flooding could also cause damage to buildings, equipment, and electrical systems that could require a plant to curtail operations or shut down. In addition, flood waters could interfere with heat removal from spent fuel pools by blocking ventilation ports with water. Prolonged exposure to salt water from coastal flooding could also degrade or corrode a casks exterior, potentially posing risks to the environment and human health.

Our analysis of Federal Emergency Management Agency data found that 60 of the 75 nuclear power plants in the United States are located in areas with high flood hazard and two are in areas with moderate flood hazard.26 Just over one-third of the plants (21 of 60) located in areas with high flood hazard are in the South (see fig. 6). According to the NCA, heavy rainfall and flooding are expected to become more frequent and severe across the United States. The NCA predicts that climate change will continue to exacerbate hurricane storm surge, rainfall, and flood events in U.S. coastal areas.

26We analyzed Federal Emergency Management Agency data from 2023. For our analysis, high flood hazard corresponds to areas in 100-year floodplains (areas with a 1 percent or higher annual chance of flooding), moderate flood hazard corresponds to areas in 500-year floodplains (areas with a 0.2 percent or higher annual chance of flooding), and no/low corresponds to areas with minimal, unknown, or other flood hazards, including areas with reduced risk because of levees as well as areas with flood hazard based on future conditions, such as the future implementation of land-use plans. Of the 60 plants located in areas with high flood hazard, 42 are operating and 18 are shutdown. Both of the plants located in areas with moderate flood hazard are operating.

Flood Protection To mitigate the impacts of flooding, licensees have implemented various measures, including the elevation of spent fuel pools and use of flood barriers.

Flood barrier protecting part of the Turkey Point Nuclear Generating Station Sources: GAO site visit and interviews with plant personnel at the Turkey Point Nuclear Generating Station; GAO (photo). l GAO-24-106326

Page 20 GAO-24-106326 Nuclear Power Plants Figure 6: Nuclear Power Plants Located in Areas with High and Moderate Flood Hazard Note: To determine if a plant is located in an area with exposure to moderate or high flood hazard, we identified overlap between a 0.5-mile radius around nuclear power plant coordinates provided by the Nuclear Regulatory Commission and the flood hazard data. Overlap indicates that a facility is located in an area that may be affected by the selected hazard. See appendix I for more details on our data analysis. To show exposure to flooding, we use the Federal Emergency Management Agencys National Flood Hazard Layer, which estimates several levels of flood hazard, including high flood hazard (areas with a 1 percent or higher annual chance of flooding), and moderate flood hazard (areas with a 0.2 percent or higher annual chance of flooding). This analysis does not account for any protective measures plants may have taken to mitigate the risk of selected natural hazards.

Hurricanes. High winds from hurricanes can generate projectiles capable of damaging parts of nuclear power plants and electricity transmission lines that provide nuclear power plants with power. In addition, storm surge from hurricanes can cause flooding, which could diminish a plants cooling capacity and damage buildings, equipment, and electrical

Page 21 GAO-24-106326 Nuclear Power Plants systems. About 23 percent of nuclear power plants (17 of 75) are located in areas that may be inundated by storm surge from Category 4 or Category 5 hurricanes,27 according to our analysis of NOAA and NRC data.28 All 17 of these plants are in the East and South, and the six plants with exposure to Category 5 hurricanes are located in the South (see fig.

7).29 According to the NCA, climate change is expected to heighten hurricane storm surges, wind speeds, and rainfall rates.30 27Of the 17 plants located in areas that may be inundated by storm surge from Category 4 or 5 hurricanes, 11 are operating and six are shut down. For the West Coast of the United States, storm surge data were only available for Southern California.

28Our analysis of NOAA storm surge data is based on a model that estimates the maximum extent of storm surge at high tide. NOAA provides estimates of hurricane storm surge using a model called Sea, Lake, and Overland Surges from Hurricanes. This model includes hypothetical hurricanes under different storm conditions, such as landfall location, trajectory, and forward speed. Hurricanes reaching Category 3 and higher are considered major hurricanes because of the potential for significant loss of life and damage. In our analysis, we used the maximum extent of storm surge from Category 1 hurricanes (the lowest possible category) and Category 5 hurricanes (the highest possible category) to show a range of potential climate change effects. Category 4 hurricanes carry sustained winds of 130-156 miles per hour. Category 5 hurricanes have sustained winds exceeding 156 miles per hour.

29Storm surge impacts to nuclear power plants would depend on several factors, including a plants elevation and protective measures.

30Climate change leads to warmer ocean surface temperatures. This, in turn, makes hurricanes more powerful because the temperature increase causes more water to evaporate from the ocean. Evaporation adds moisture to the air, and warmer air temperatures can hold more water vapor. The increased moisture in the air leads to more intense rainfall. In a hurricane, spiraling winds draw moist air toward the center, fueling the thunderstorms that surround it.

Page 22 GAO-24-106326 Nuclear Power Plants Figure 7: Nuclear Power Plants Located in Areas with Exposure to Storm Surges from Category 4 and Category 5 Hurricanes Notes: To determine if a plant exists in an area with exposure to hurricane storm surge, we identified overlap between a 0.5-mile radius around nuclear power plant coordinates provided by the Nuclear Regulatory Commission and storm surge data. Overlap indicates that a facility is located in an area that may be affected by the selected hazard. See appendix I for more details on our data analysis. To show exposure to hurricane storm surge, we use the National Oceanic and Atmospheric Administrations Sea, Lake, and Overland Surges from Hurricanes Model, which estimates storm surge heights resulting from the various categories of hurricanes. This analysis does not account for any protective measures plants may have taken to mitigate the risk of selected natural hazards.

Sea level rise. Sea level rise could affect nuclear power plants by contributing to greater storm surges and flooding. According to NOAA officials, a rise in sea level can increase corrosion from saltwater intrusion and lead to chronic long-term erosion of coastal cliffs, where some plants

Page 23 GAO-24-106326 Nuclear Power Plants are located.31 According to a NOAA report, over the next 30 years sea levels will continue to rise as climate change warms glaciers and ice sheets, causing additional water mass to enter the ocean.32 The rise in sea level is expected to increase coastal flooding by contributing to higher tides and storm surges that reach further inland, potentially affecting coastal nuclear power plants.

Our analysis of NOAA and NRC data indicates that about half of nuclear power plants (37 of 75) are located in a coastal region, and nine of these are located on the coastline.33 Projected sea level rise in 2050 varies by coastal region, from 0.5 feet in the Northwest to 1.9 feet in the Western Gulf (see fig. 8). In addition, sea level rise may increase saltwater intrusion into the coastal rivers or groundwater aquifers that some nuclear power plants use for service or potable water.34 31NOAA officials said that Turkey Point Nuclear Generating Station is an example of a plant where, if unaddressed, sea level rise could lead to saltwater intrusion into the plants cooling canals. Officials also said that Southern California is an example of an area where cliffs consist of unconsolidated rock, a type of loose rock composition that is particularly vulnerable to long-term erosion from sea level rise.

32W. V. Sweet, B. D. Hamlington, R. E. Kopp, C. P. Weaver, P. L. Barnard, D. Bekaert, W.

Brooks, M. Craghan, G. Dusek, T. Frederikse, G. Garner, A. S. Genz, J. P. Krasting, E.

Larour, D. Marcy, J. J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L.

Schmied, W. Veatch, K. D. White, and C. Zuzak, 2022: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines, NOAA Technical Report NOS 01 (Silver Spring, MD: Feb. 2022).

33Of the 37 nuclear power plants located in a coastal region, 24 are operating and 13 are shut down. Of the nine nuclear power plants located on the coastline, seven are operating and two are shut down. To determine which nuclear power plants are located on the coastline, we identified plants whose coordinates intersect with a coastline. NRC provided coordinate data, and we used a 0.5-mile radius as a proxy for plant size in our analysis.

34According to one U.S. Environmental Protection Agency source, sea level rise may increase river levels and the risk of saltwater intrusion into rivers and coastal groundwater aquifers, especially during dry periods. According to NRCs Generic Environmental Impact Statement for License Renewal of Nuclear Plants, saltwater intrusion into groundwater aquifers can degrade the quality of groundwater used for potable and service water at nuclear power plants. See NUREG-1437, Vol. 1, Revision 1.

Page 24 GAO-24-106326 Nuclear Power Plants Figure 8: Nuclear Power Plants in the National Oceanic and Atmospheric Administration (NOAA) Coastal Regions and Projected Sea Level Rise in 2050 Note: The regional sea level rise values for 2050 are regional observation-based extrapolations from an interagency report covering sea level rise scenarios. These extrapolations use observed changes in sea level rise and other factors to estimate the trajectory of sea level rise in the near term. Sea-level rise primarily affects coastlines but may also affect the salinity and level of coastal rivers and groundwater aquifers. This map includes all nuclear power plants that are located in NOAA coastal regions. The analysis does not account for site-specific plant elevation or protective measures plants may have taken to mitigate the risk of selected natural hazards.

Appendix III provides additional details of our analysis of exposure to flooding, hurricane storm surges, and sea level rise in areas where nuclear power plants are located.

Page 25 GAO-24-106326 Nuclear Power Plants Cold temperatures can diminish cooling capacity and lead to the loss of offsite power, posing risks to nuclear power plants. Specifically, extreme cold conditions may create ice that could block a plants cooling water intake system, potentially reducing the supply of cooling water to safety-related systems and components. In addition, frozen precipitation can cause icing of power lines and lead to full or partial loss of off-site power, potentially forcing a plant to rely on backup diesel that may be vulnerable to extremely cold air temperatures.

Climate change may affect extreme cold weather events.35 While the NCA found that climate change is expected to cause an overall increase in average temperatures, a 2021 study funded in part by NOAA found that Arctic warming caused by climate change may cause extremely cold air from the Arctic to stretch into the United States.36 The study links climate change to extreme cold events, such as the record cold temperatures in Texas in 2021. Our analysis of NCA climate projections data and NRC location data found that the average operating nuclear power plant will 35As noted previously, according to the NCA, there is disagreement among researchers about some climate impacts. For example, whereas emerging research suggests that the frequency of cold weather events and heavy snowfall may be increasing because of warming Arctic temperatures, there is some disagreement in the research community regarding this projection.

36J. Cohen, L. Agel, M. Barlow, C. I. Garfinkel, and I. White, Linking Arctic Variability and Change with Extreme Winter Weather in the United States, Science, Volume 373, Issue 6559 (Washington, D.C.: 2021) 1116-1121.

Extreme Cold Weather Events Pose Risks to Nuclear Power Plants, and Climate Change May Affect These Events in Certain Regions Extreme Cold at South Texas Project Nuclear Power Plant On February 15, 2021, the South Texas Project experienced an automatic reactor shutdown when a 5-foot section of uninsulated water line froze, causing the failure of a feed water pump. The Nuclear Regulatory Commission (NRC) found that the facility shut down safely, but the licensee failed to implement a required Freezing Weather Plan to insulate the line. According to one NRC official, a cold weather event nearly rendered another plants diesel generators inoperable when the air intake temperature dipped to -50 degrees Fahrenheit.

South Texas Project, reactor units 1 and 2 Sources: GAO analysis of NRC documents; U.S. NRC Blog (photo). l GAO-24-106326

Page 26 GAO-24-106326 Nuclear Power Plants experience from 17 to 22 fewer frost days annually.37 However, certain regions may also see an increase in extreme cold weather events.

Following 2021s Winter Storm Uri, the Federal Energy Regulatory Commission approved a new standard, effective October 2024, that will require certain owners of certain electricity generating units, including nuclear power reactors, to implement freeze protection measures to operate for at least 12 continuous hours at the units recorded extreme cold weather temperature.38 Appendix III provides additional details of our analysis of exposure to cold weather events in areas where nuclear power plants are located.

37Climate projections are used to show a range of future outcomes, and are limited by uncertainties in emissions, natural variability, and scientific models. To show a range of possible outcomes, we used climate projections for a low-emission scenario (17 days) and a high-emission scenario (21 days). Climate projections rely on a variety of assumptions about the future. These limitations are further discussed in appendix II.

38In 2023, the Federal Energy Regulatory Commission (FERC) approved Emergency Operation Standard 012-01, also known as the Extreme Cold Weather Preparedness and Operations standard. Effective October 1, 2024, the standard addresses the effects of operating in extreme cold weather by ensuring owners and operators of generating units like nuclear power reactors develop and implement plan(s) to mitigate the reliability impacts of extreme cold. FERC defines extreme cold weather as the temperature equal to the lowest 0.2 percentile of the hourly temperatures measured in December, January, and February. The standard exempts certain generating units, including nuclear power reactors, which have an extreme cold weather temperature exceeding 32 degrees Fahrenheit or operate only in a backup or non-winter capacity.

Cold Protection Licensees have insulated water lines and added cold-weather insulation for turbines to protect against freezing water in pipes and damage to other plant equipment.

Example of insulation at an industrial facility Sources: Interviews with plant personnel at the Turkey Point Nuclear Generating Station; rootstocks/stock.adobe.com (photo). l GAO-24-106326

Page 27 GAO-24-106326 Nuclear Power Plants NRCs processes for licensing and overseeing nuclear power plants include actions to address risks from natural hazards. However, NRCs actions do not fully consider the potential effects of climate change.

NRCs existing processes are designed to address risks to the safety of nuclear power plants, including risks from natural hazards. For example:

Defense-in-depth. A nuclear power plant must be designed and built to withstand phenomena or events such as earthquakes, tornadoes, hurricanes, and floods without the loss of the structures, systems, or components necessary to ensure public health and safety. According to NRC, NRCs defense-in-depth approach focuses on protecting plants against risks such as those related to events that exceed a plants design basis, including flooding from intense precipitation or hurricanes.39 As such, NRCs defense-in-depth approach includes verifying that plants have multiple physical barriers and equipment backups to ensure plant safety if plant structures and equipment are damaged due to such severe weather events or if a power outage threatens a plants ability to continue cooling the reactor.

39The design basis for a plant includes the specific functions to be performed by the structures, systems, or components that could be compromised by an adverse weather event that exceeds what the plant was designed to withstand, such as the maximum flood elevation or maximum temperature limit allowed for a plant to continue operating. 10 C.F.R. Part 50, Appendix A, General Design for Nuclear Power Plants, Criterion 2 Design Bases for Protection Against Natural Phenomena.

NRCs Actions to Address Risks to Nuclear Power Plants from Natural Hazards Do Not Fully Consider the Potential Effects of Climate Change NRCs Oversight of Nuclear Power Plants Includes Actions to Address Risks from Natural Hazards

Page 28 GAO-24-106326 Nuclear Power Plants Licensing. During the licensing process, NRC assesses a plants risks from natural hazards as part of its safety evaluation. In doing so, NRC reviews reactor and plant designs and compares the design limits for natural hazards with the sites expected exposure to natural hazards on the basis of the licensees hazard assessments.

According to NRC officials, NRC also conducts a confirmatory analysis of the licensees hazard assessments, which if deemed insufficient, must be revised by the licensee.

Inspections. NRC resident inspectors use inspection manual procedures to inspect licensees preparations for addressing adverse weather events and extreme temperatures.40 As part of their inspections, NRC resident inspectors verify that selected systems and components will function when affected by adverse weather. NRC officials explained that an inspection includes observing licensees repair and run pieces of equipment, conducting emergency drills, and verifying that licensees are taking appropriate actions in response to severe weather conditions. Inspectors from NRC regional offices may also conduct plant inspections after adverse weather events, such as floods or hurricanes.

Probabilistic risk assessments. NRC uses probabilistic risk assessments in its licensing and inspection processes to analyze various risks, including safety risks posed by natural hazards.41 These assessments are a systematic method for assessing what can go wrong, its likelihood, and its potential consequences to provide insights into the strengths and weaknesses of the design and operation of a nuclear power reactor. Probabilistic risk assessments are used to estimate the risk of reactor core damage, radioactive material release, and related consequences to the public and environment based on the as-built, as-operated plant.

Operating experience program. NRCs operating experience program collects and evaluates information from various regulatory oversight activities and inspection findings and shares information about plants operating experiences with NRC staff. In addition, according to NRC officials, NRC has a research office that analyzes long-term trends, such as the loss of offsite power due to severe 40Inspections by resident inspectors at the plant level are called baseline inspections, and different types of baseline inspections occur either daily, quarterly or annually.

41Applicants for certain licenses for new reactors must submit a description of the plant-specific probabilistic risk assessment and its results to NRC as a part of their application.

Defense-in-Depth at Duane Arnold Energy Center In 2020, the Iowa Derecho Windstorm brought heavy rains and winds up to 130 miles per hour to the Duane Arnold Energy Center.

The storm resulted in the loss of offsite power, which caused an emergency shutdown of the reactor. Winds from the storm also damaged two cooling towers and buildings housing the reactor, turbine, and equipment.

However, according to a Nuclear Regulatory Commission (NRC) document, the plants safety margins and use of a defense-in-depth approach mitigated the effects of storm damage. Specifically, the plant had multiple backup generators and pumps as well as physical barriers to protect the plant.

During the storm, the plant lost offsite power, and the cooling pump for the spent fuel pool turned off. Before the outage, two emergency diesel generators started automatically due to grid-related storm impacts. Staff immediately started a second cooling pump. This action prevented the water in the spent fuel pool from boiling and potentially exposing the fuel rods.

According to NRC, the winds also damaged the reactors containment unit, but it remained functional and would have prevented a release of radiological material in the event of damage to the reactor core.

Duane Arnold Energy Center Sources: Nuclear Regulatory Commission; AsNuke (photo),

https://creativecommons.org/licenses/by-sa/4.0/deed.en. No changes were made to this photo. l GAO-24-106326

Page 29 GAO-24-106326 Nuclear Power Plants weather, to identify lessons learned that could be applied to the oversight of other plants.

Following the 2011 accident at Japans Fukushima Dai-ichi nuclear power plant, NRC and industry took several actions to further address risks to nuclear power plants from natural hazards.42 Some of these actions were taken in response to recommendations from a task force NRC established to assess its regulatory approach (see fig. 9).

42On March 11, 2011, a 9.0-magnitude earthquake and subsequent tsunami devastated northeast Japan and led to the most extensive release of radioactive material at a nuclear power plant since the 1986 Chernobyl disaster. The Fukushima Dai-ichi nuclear power plant suffered extensive damage when a 45-foot-high tsunami wave exceeded the plants seawall and flooded the site, causing a prolonged loss of electrical power at several of its reactors. As a result of the loss of power, plant operators were unable to keep three of the reactors cool, which led to fuel melting, hydrogen explosions, and the release of radioactive material into the environment. The disaster displaced tens of thousands of residents and contaminated the surrounding area. Nuclear-power-generating countries worldwide have since taken actions to prepare for an event like this, which far exceeded the Fukushima Dai-ichi plants design basis.

NRC Inspectors Address Heat Risks at the Palo Verde Nuclear Generating Station To prepare for extreme summer heat, Nuclear Regulatory Commission (NRC) resident inspectors at the Palo Verde Nuclear Generating Station in Arizona inspect systems likely to be affected by high temperatures, such as diesel generators and spray ponds, both of which are used to cool the reactor. The spray ponds contain a 26-day supply of water to ensure that plants have adequate cooling capacity to safely shut down.

Because high temperatures can cause water held in the spray ponds to evaporate, the plant relies on its reservoirs and deep wells as backup sources of water.

Palo Verde Nuclear Generating Station spray pond Sources: NRC; GAO (photo). l GAO-24-106326

Page 30 GAO-24-106326 Nuclear Power Plants Figure 9: Timeline of Selected Nuclear Regulatory Commission (NRC) and Industry Actions after the Fukushima Dai-ichi Accident in 2011 aNRC prioritized the recommendations in three tiers: (1) recommendations NRC should implement without unnecessary delay; (2) recommendations that could not be initiated in the near term due, in part, to resource or critical skill set limitations; and (3) recommendations that required further study by NRC to determine if regulatory action was necessary, among other factors.

bNRC, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, Order EA-12-049 (Washington, D.C.: Mar. 12, 2012); Issuance of Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation, Order EA-12-051 (Washington, D.C.: Mar. 12, 2012); and Order Modifying Licenses with Regard to Reliable Hardened Containment Vents, Order EA-12-050 (Washington, D.C.: Mar. 12, 2012).

cNRC, Mitigation of Beyond-Design-Basis Events, 84 Fed. Reg. 39,684 (Aug. 9, 2019). Orders EA 049 and EA-12-051 are applicable to all licensees and construction permit holders. Order EA-12-050 applies to licensees with boiling water reactors that feature certain containments that require proper venting to ensure safety.

dNuclear Energy Institute, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, NEI 12-06 (August 2012) and NRC, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, Order EA-12-049 (Washington, D.C.: Mar. 12, 2012).

Page 31 GAO-24-106326 Nuclear Power Plants The actions NRC took in response to the task force recommendations include the following:

Required licensees to assess flooding risks. NRC required all licensees to assess updated flood hazard risk information and reevaluate and upgrade, as necessary, their plants flood protection of structures, systems, and components. On the basis of these assessments, NRC did not identify the need to require any plant modifications or revise plant safety procedures.43 Created a process for ongoing hazard assessments. In May 2017, the Commission approved the Process for the Ongoing Assessment of Natural Hazard Information (POANHI) to determine the need for site-specific assessments, additional research, or regulatory action.44 POANHI involves collecting and maintaining hazard information in the 43NRC required all nuclear power plant licensees to conduct on-site inspections of safety-related systems to verify that plant features that protect against flooding are available, functional, and properly maintained. All licensees conducted flood reevaluations for their plants, and licensees at six plants conducted further integrated assessments, which are requested by NRC if the plants design for a potential flood is exceeded by the reevaluations estimates of potential maximum elevation of flood waters. These assessments evaluate the plant response to flooding hazards and the effectiveness of existing systems and procedures to mitigate risks from flooding. In addition, NRC required licensees to identify and address plant-specific vulnerabilities related to flooding and verify the adequacy of monitoring and maintenance for protection features in the interim period until longer term actions were completed to reevaluate design-basis flooding hazards.

Also, following the accident at the Fukushima Dai-ichi plant, NRC issued a temporary instruction directing its inspection staff to independently assess the adequacy of actions taken by licensees. NRC also required licensees to assess seismic hazard risks. Seismic hazard risks are not included in the scope of this report.

44Preceding the approval of POANHI, NRC conducted a 2013 Probabilistic Flood Hazard Assessment workshop following the accident at the Fukushima Dai-ichi nuclear power plant, in which participants from federal agencies and other organizations shared information about probabilistic assessment of extreme rainfall, flood-induced dam and levee failures, tsunami flooding, river flooding, extreme storm surge, and combined-events flooding. NRC continues to host Probabilistic Flood Hazard workshops nearly annually, and these workshops often share research results with the public. For example, NRC contracted with the Pacific Northwest National Laboratory to publish four national and regional reports on the potential impacts of climate change, which as of 2022 have not yet led to additional NRC guidance for probabilistic flood hazard assessment. These reports are publicly available at https://www.osti.gov/biblio/1259942, https://www.osti.gov/biblio/1593340, https://www.osti.gov/biblio/1524249, and https://www.osti.gov/biblio/1605280.

Page 32 GAO-24-106326 Nuclear Power Plants Natural Hazards Information Digest45a database that supports POANHIand reviewing and assessing the hazard information to determine whether a hazard has a potentially significant impact on plant safety.46 To ensure that NRC is aware of new hazard information from a variety of sources for inclusion in this database, NRC regularly interacts with internal and external stakeholders, including other federal agencies, academia, industry, regulators from other countries, and other technical and scientific organizations, according to NRC officials. If a POANHI assessment of new hazard information identifies a potentially significant effect on plant safety, NRC refers the issue to the appropriate regulatory program, at which point the program office determines how to proceed. POANHI leverages and is integrated into other existing processes, such as the operating experience program, for the assessment of new information and the determination of whether a change is needed to a particular plants licensing basis. According to NRC officials, NRC has not taken any regulatory actions as a result of POANHI.47 Required enhanced safety and emergency equipment. In 2012, NRC ordered all licensees and nuclear power plant construction permit holders to ensure that a plants key safety functions could be 45NRC incorporates new hazard information, such as records of site-specific or regional extreme weather events, into its Natural Hazards Information Digest, which NRC began using in 2019. This database is NRCs repository for information on natural hazard-related events at or near nuclear power plants. The database captures documentation provided by licensees in response to site hazard reevaluations and plant inspections as well as historical site-specific events and information about natural hazards that could affect plants. In addition to informing POANHI, the database also supports NRC efforts to (1) respond to emergent events associated with natural hazards by providing relevant information, (2) engage with stakeholders, (3) evaluate natural hazard-related inspection findings to determine their safety significance, (4) implement natural hazards research plans, and (5) update regulatory and staff guidance.

46According to NRC policy, the significance assessment determines whether the new information indicates that the hazard could adversely affect the capability of a plants structures, systems, and components to perform their intended safety functions. To make this determination, NRC staff either conduct a quantitative assessment that compares the new information with risk insights from past hazard analyses to assess the impacts of plant response or conduct a qualitative assessment that considers the likelihood of the event, identifies vulnerabilities and actions to address them, and adheres to defense-in-depth principles, among other factors.

47NRC is reviewing new seismic information from a 2018 report to assess updated seismic hazards at the nuclear power plants located in the region addressed by the report. See Pacific Earthquake Engineering Research Center, Central and Eastern North America Ground-Motion Characterization: NGA-East Final Report, (Berkeley, CA: December 2018). After reviewing this report, NRC determined that 13 nuclear power plants located in the central and eastern United States needed further assessment. Based on assessments conducted as of March 2024, NRC determined that no regulatory action was needed.

Page 33 GAO-24-106326 Nuclear Power Plants maintained during a natural disaster that exceeds a plants design basis. In response, the nuclear industry developed and implemented the Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, which NRC has endorsed as one method to comply with the 2012 order.48 FLEX is a strategy that uses controls, procedures, and backup equipment to ensure that the key safety functions related to cooling a reactors core and spent fuel, as well as containment to prevent accidental releases of radiation, are maintained if a disaster occurs at a plant. According to NRC officials, as part of this strategy, all plants have backup equipment on site. In addition, the nuclear power industry operates two Strategic Alliance for FLEX Emergency Response (SAFER) centers that maintain emergency equipment that can be provided to plants as a backup to plants primary backup equipment onsite.49 See figure 10 for examples of FLEX and SAFER equipment.

48Nuclear Energy Institute, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, NEI 12-06, August 2012.

49The SAFER centers are located in Phoenix, Arizona, and Memphis, Tennessee. The SAFER centers staff comprises staff from a private company that has contractual agreements to manage and deploy offsite equipment with every nuclear licensee in the United States as part of FLEX. The SAFER centers maintain generic equipment useful for multiple plants, including various types of generators and pumps, and site-specific equipment unique to certain plants. NRC determined there is reasonable assurance that equipment at the SAFER centers can be deployed to any plant in the United States within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />, as specified by licensees SAFER response plans. To date, no SAFER response plan has been activated. According to our analysis of federal hazard data, SAFER centers are in areas with no exposure to sea level rise or hurricane storm surge, and either low (Memphis) or high (Phoenix) flood hazard. The centers are located in areas projected to see an increase in daily temperature from 3.6 to 4.9 degrees, and the Phoenix SAFER center is in an area with high or very high wildfire risk.

Page 34 GAO-24-106326 Nuclear Power Plants Figure 10: Examples of the Diverse and Flexible Coping Strategies (FLEX) and Strategic Alliance for FLEX Emergency Response (SAFER) Center Equipment NRCs actions to address risks to nuclear power plants from natural hazards in its licensing, license renewal, and inspection processes do not fully consider the potential increased risks from natural hazards that may be exacerbated by climate change.

Licensing. NRC does not use climate projections data to identify and assess risk as part of the safety reviews or probabilistic risk NRCs Actions Do Not Fully Consider the Potential Effects of Climate Change

Page 35 GAO-24-106326 Nuclear Power Plants assessment reviews it conducts during the initial licensing process.50 Rather, NRC uses historical data to extrapolate the future risks of natural hazards that may occur during the lifetime of a nuclear power plant.51 Extrapolating historical data into the future assumes that existing climatological trends will continue.52 According to NRC officials, NRC uses historical data in conjunction with other information to establish a conservative licensing basis, and many of the natural hazards considered during licensing target annual exceedance probabilities such that an event is unlikely to occur during the lifetime of the plant. In such a case, NRC expects the event to occur only once in 10,000 to 10 million years, depending on the hazard. NRC officials we interviewed told us that they review regional climate projections information for some hazards but do not incorporate site-specific climate projections data, which include hazard assessments, design bases, or determining the adequate safety margin for plants. For example, NRC officials said they review the projected average increase in temperature that applies to a multi-state region according to the NCA designation and compare that with the maximum temperature limits for a particular plant in that region.

The officials said that they do not use data on the projected temperature increase to inform licensing decisions at the plant site itself.

License renewals. Following an initial 40-year licensing period, NRC does not reevaluate natural hazard risks, including climate-related 50The NCA defines a climate projection as the simulated response of the climate system to a scenario of future emissions or concentrations of greenhouse gases and aerosols, generally derived using climate models. Projections data could be based on a range of possible future scenarios for particular time frames, such as the projected temperature of a specific location in the year 2050, as identified by models that consider climate systems physical, chemical, and biological properties and their interactions. According to NRC officials we interviewed, probabilistic risk assessments use current estimates of the probability of external events, and neither licensees nor NRCs assessments incorporate climate projections data, despite their role in assessing the likelihood of future events.

NRC officials said that while it is both technical and feasible to update these models with the latest information reflecting their current state of knowledge, using climate projections data would increase uncertainty in the results of the probabilistic risk assessments, and no historical trends have emerged to suggest the need to adjust these.

51For example, NRC regulations for evaluating sites for initial licensing require NRC to consider the seismology, meteorology, geology, and hydrology of the site and to estimate the maximum probable flood using historical data, among other factors. 10 C.F.R. § 100.20(c). These regulations do not preclude NRC from using climate projections data.

52As noted previously, according to the NCA, climate change is altering the characteristics of many extreme weather events. Specifically, some of these events have already become more frequent, intense, widespread, or of longer duration, and many are expected to continue to worsen.

Page 36 GAO-24-106326 Nuclear Power Plants risks, to update the safety reviews required for the license renewal process. NRCs license renewal process focuses on evaluating and managing the effects of aging on the extended operations of nuclear power plants and considers the original licensing basis in that context.53 As of January 2024, NRC had issued license renewals to 49 of the 54 operating nuclear power plants, meaning most plants are operating on the basis of assessments of natural hazard risk that are over 40 years old.

Inspections. During regular inspections, NRC resident inspectors are responsible for focusing on the immediate day-to-day safety of plants rather than on the potential long-term safety risks. Inspections do not include an assessment of future climate projections data. In addition, while NRC sometimes conducts additional inspections using outside teamsincluding staff from NRC regional officesto address recent events or emerging issues related to safety, these inspections also do not focus on long-term safety risks.

NRC officials we interviewed told us that while their regulatory processesincluding licensing, license renewals, and inspectionsdo not use climate projections data to assess climate risks, they believe conservatism, safety margins, and defense-in-depth provide an adequate margin of safety to address climate risks to the safety of nuclear power plants.54 However, NRC has not conducted an assessment to demonstrate that this is the case.

Moreover, NRC actions taken to address risks to nuclear power plants from natural hazards post-Fukushima did not fully consider the effects of climate change. Specifically, NRC required licensees to assess flooding risk and enhance safety and emergency equipment, but NRC did not require licensees to use climate projections data to assess future flooding 53Licensees are not required to reevaluate their plants design basis pertaining to natural hazards as part of the license renewal process.

54According to NRC officials, NRC uses the NCA, which includes climate projections, in the environmental reviews it conducts during licensing and license renewals to assess the expected effects of nuclear power plants on the environment. For example, NRC addresses the greenhouse gas emissions associated with the life cycle of the plant as well as the potential effects of climate change on the environment in these reviews.

Page 37 GAO-24-106326 Nuclear Power Plants risks as part of these assessments or in the FLEX equipment needs assessments.55 NRC also created POANHIits process for ongoing hazard assessments following Fukushimawhich, according to NRC officials, NRC relies on to identify and assess changes in natural hazard risks, including those driven by climate change. However, POANHI has several limitations as a mechanism for comprehensively identifying and assessing climate risks.

Specifically:

While POANHI was designed to assess all natural hazards, NRC has not used POANHI to assess potential changes to all natural hazards, nor has NRC comprehensively reviewed natural hazards on a regular basis to determine whether available information indicates the need for a POANHI assessment. NRC officials told us that while POANHI requires continuous evaluation of new information on natural hazards, NRC conducts POANHI assessments for one hazard at a time, and the agency does not have a schedule for reviewing natural hazards beyond the assessment of seismic hazards currently underway. As such, POANHI is used to react to new hazard information or events when NRC staff become aware of them.

NRC has not documented the new hazard information it reviews as part of POANHI or the way it incorporates climate projections data to determine whether to initiate a POANHI assessment, require additional plant-specific assessments, conduct an overall hazard reevaluation, or take regulatory action.

NRC has not implemented POANHI and the Natural Hazards Information Digest at all levels of the agency. For example, several regional branch chiefs and resident inspectors we interviewed were unaware of POANHI and this information database. An official from one NRC regional office said that if the database were shared more broadly, it would benefit resident inspectors, who could access and use information on weather-related events and inspection findings to inform probabilistic risk assessments. According to NRC officials, the 55According to NRC officials, the plant-specific mitigation strategy relied on information each licensee had previously been required to provide as part of reevaluations of external events for comparison against the current licensing bases and FLEX equipment reflect the most severe external events that could occur based on known available meteorological, geological, and geographical data. According to NRC officials, the external hazards needing to be considered were both extreme and rare in nature which resulted in the regulatory approach of using flexible, diverse strategies to maintain or restore core cooling, containment, and spent fuel pool cooling.

Page 38 GAO-24-106326 Nuclear Power Plants agency is conducting internal outreach to increase NRC staffs knowledge of POANHI.

NRCs Fiscal Year 2022-2026 Strategic Plan calls for ensuring that licensees have measures to address the potential for increased risks from climate change. The strategic plan also promotes risk-informed decision-making to support NRCs strategic objective of providing quality licensing and oversight of nuclear facilities. Moreover, GAOs Standards for Internal Control in the Federal Government state that management should identify, analyze, and respond to risks related to achieving defined objectives.56 These standards also call for agency management to use quality information to achieve their objectives.

Assessing its current processes would help NRC to determine whether they adequately address the potential for increased risks to nuclear power plants from climate change. Specifically, identifying gaps in its processes and developing a plan to address them, including by using climate projections data or augmenting POANHI, would help ensure that NRC adopts a comprehensive approach for assessing risks and fulfills its mission to protect public health and safety.

NRC officials told us that they use historical data in licensing and oversight processes rather than climate projections data, in part because regulations require NRC to use available historical data to assess the safety of the reactor site and design and they believe these data are reliable and sufficient for developing an adequate margin of safety for plants.57 According to NRC officials, using site-specific climate projections 56GAO-14-704G. Risk assessment is the identification and analysis of risks related to achieving defined objectives to form a basis for developing responses to these risks. Our prior work has shown that assessing risks includes assessing both the likelihood of an event occurring and the effect the event would have. Agency leaders and subject matter experts should assess each risk by assigning the likelihood of the events occurrence and the potential effect if the event occurs. GAO, Enterprise Risk Management: Selected Agencies Experiences Illustrate Good Practices in Managing Risk, GAO-17-63 (Washington, D.C.: Dec. 1, 2016).

57See, e.g., 10 C.F.R. § 100.20(c) (requiring NRC to consider for initial licensing of new reactors the seismology, meteorology, geology, and hydrology of the site and to estimate the maximum probable flood using historical data). See also 10 C.F.R. § 60.2 (defining design bases to include using severe natural events estimates based on historical and physical data); and 10 C.F.R. Part 50, Appendix A, General Design for Nuclear Power Plants, Criterion 2Design Bases for Protection Against Natural Phenomena (requiring the design bases for the reactors safety structures, systems, and components to consider the most severe of the natural phenomena that have been historically reported for the site and surrounding area, with sufficient margin for the limited accuracy, quantity, and period of time in which the historical data have been accumulated, among other factors).

Page 39 GAO-24-106326 Nuclear Power Plants data for extreme hazard levels in nuclear power plant design and safety reviews is challenging because of the uncertainty associated with applying these data to specific sites. However, NRC regulations do not preclude NRC from using climate projections data, and new sources of reliable projected climate data are available to NRC. In 2023, the White House Office of Science and Technology Policy issued guidance to federal agencies on selecting and using climate data to assess risks and their potential impacts.58 This guide provides information on climate models and projections to help federal agencies understand exposure to current and future climate-related hazards and their potential impacts.

Without incorporating the best available information into its licensing and oversight processes, it is unclear whether the safety margins for nuclear power plants established during the licensing periodin most cases over 40 years agoare adequate to address the risks that climate change poses to plants.

Commercial nuclear power plants in the United States were licensed and built an average of 42 years ago, and weather patterns and climate-related risks to their safety and operations have changed since their construction. Climate change is expected to exacerbate natural hazardssuch as heat, drought, wildfires, flooding, hurricanes, sea level rise, and extreme cold weather eventsthat can affect nuclear power plant safety and operations in various ways. Some of these effects are already occurring, and many are expected to continue to worsen.

However, NRC does not use climate projections data to identify and assess risk as part of the safety reviews it conducts or the probabilistic risk assessments it reviews during the initial licensing process. NRC has also not fully developed POANHI, which the agency relies on to identify and assess changes in natural hazard risks, including climate change.

NRC has the opportunity to consider climate risks more fully and, in doing so, to better fulfill its mission to protect public health and safety.

58Office of Science and Technology Policy, Selecting Climate Information to Use in Climate Risk and Impact Assessments: Guide for Federal Agency Climate Adaptation Planners, (Washington, D.C.: March 2023). Although climate projections data and guidance are available to federal agencies, we previously recommended that the federal government, through the Executive Office of the President, make authoritative climate data and information accessible and assist in translating that information for decision makers. GAO, High-Risk Series: Efforts Made to Achieve Progress Need to Be Maintained and Expanded to Fully Address All Areas, GAO-23-106203 (Washington, D.C.: April 20, 2023) and Climate Information: A National System Could Help Federal, State, Local, and Private Sector Decision Makers Use Climate Information, GAO-16-37 (Washington, D.C.:

Nov. 23, 2015).

Conclusions

Page 40 GAO-24-106326 Nuclear Power Plants Specifically, assessing whether its licensing and oversight processes adequately consider climate risks to nuclear power plants and developing and implementing a plan to address any gaps identified would help the agency do so. As NRC makes licensing, license renewal, and oversight decisions, adopting an approach that incorporates the best available information on climate risks and ways that those risks may affect nuclear plants, would provide greater assurance that licensees have adequate measures to address risks from climate change.

We are making the following three recommendations to NRC:

The Chair of the NRC should direct NRC staff to assess whether its licensing and oversight processes adequately address the potential for increased risks to nuclear power plants from climate change.

(Recommendation 1)

The Chair of the NRC should direct NRC staff to develop, finalize, and implement a plan to address any gaps identified in its assessment of existing processes. (Recommendation 2)

The Chair of the NRC should direct NRC staff to develop and finalize guidance on incorporating climate projections data into relevant processes, including what sources of climate projections data to use and when and how to use climate projections data. (Recommendation 3)

We provided a draft of this report for review and comment to NRC.

In its written comments, reproduced in appendix IV, NRC stated that the three recommendations are consistent with actions that are either underway or under development. In addition, NRC stated that the layers of conservatism and defense-in-depth incorporated into NRCs processes provide reasonable assurance regarding any plausible natural hazard and combinations at a site for the licensed operational lifetime of the reactor, including those that could result from climate change. As we noted in our report, NRC has not conducted an assessment to demonstrate that the safety margins for nuclear power plants established during the licensing period are adequate to address the risks that climate change poses to plants. According to the NCA, many of the climate conditions and impacts experienced in the United States today are unprecedented for thousands of years. Across all regions of the United States, extremes, including heat, drought, flooding, wildfire, and hurricanes, are becoming more frequent and/or severe, with a cascade of effects in every part of the country. We continue to believe that NRC cannot fully consider potential Recommendations for Executive Action Agency Comments and Our Evaluation

Page 41 GAO-24-106326 Nuclear Power Plants climate change effects on plants without using the best available informationincluding climate projections datain its licensing and oversight processes.

NRC also provided technical comments, which we incorporated, as appropriate.

We are sending copies of this report to the appropriate congressional committees, the Chair of the NRC, and other interested parties. In addition, the report is available at no charge on the GAO website at https://www.gao.gov.

If you or your staff have any questions about this report, please contact me at (202) 512-3841 or ruscof@gao.gov. Contact points for our Offices of Congressional Relations and Public Affairs may be found on the last page of this report. GAO staff who made key contributions to this report are listed in appendix V.

Frank Rusco Director, Natural Resources and Environment

Appendix I: Objectives, Scope, and Methodology Page 42 GAO-24-106326 Nuclear Power Plants This report examines (1) how climate change is expected to affect nuclear power plants and (2) actions the Nuclear Regulatory Commission (NRC) has taken to address the risks to nuclear power plants from climate change.

To address both objectives, we interviewed officials from NRC headquarters, all four NRC regional offices, and two nuclear power plants. We also interviewed officials from the Department of Energy including the Office of Nuclear Energy and the Idaho National Laboratorythe Department of Homeland Security, the Federal Energy Regulatory Commission, and the National Oceanic and Atmospheric Administration (NOAA). We also interviewed nine stakeholders knowledgeable about nuclear power plant safety and operations, climate change, and resilience measures. These included stakeholders from three industry groups, four nongovernmental organizations, and two academic institutions. We identified stakeholders using snowball sampling.1 Views from selected stakeholders cannot be generalized to all stakeholders.

We conducted site visits to two nuclear power plantsPalo Verde Nuclear Generating Station in Buckeye, Arizona, and Turkey Point Nuclear Generating Station in Homestead, Florida. We toured the power plants and interviewed plant staff and NRC resident inspectors at each site. To answer both objectives, we chose these sites for in-person visits based on factors including exposure to distinct natural hazards, regional diversity, reactor type, licensee size, and agency resources. Findings from selected site visits are not generalizable to all sites.

To address how climate change is expected to affect nuclear power plants, we reviewed prior GAO reports and sources of climate change information (including the fourth and fifth National Climate Assessments (NCA)), completed a literature review, and conducted data analysis.2 To conduct the literature review of articles and reports related to the effects of selected hazards and climate change on nuclear power plants, we searched a variety of scholarly, trade, and news databases, such as Ei 1In snowball sampling, the methodology begins with an initial list of contacts and asks each person interviewed to refer the interviewer to additional cognizant persons. The group of referred contacts (or snowball) grows larger and then narrows as a group of individuals are identified frequently.

2Few supporting sources distinguish between the impact of selected natural hazards on operating versus shutdown nuclear power plants. As a result, we most often do not make this distinction.

Appendix I: Objectives, Scope, and Methodology

Appendix I: Objectives, Scope, and Methodology Page 43 GAO-24-106326 Nuclear Power Plants Encompass LIT, Geobase, Inspec, the National Technical Information Service, ProQuest Environmental Science Professional, and Scopus using relevant keywords (e.g., nuclear power, climate change, risk, and extreme weather) for articles and other documents published since 2012. The results yielded 107 potentially relevant articles and other documents published from January 2012 through January 2023. To determine which articles were relevant to our scope, one analyst reviewed the articles abstracts and determined whether the articles were in scope using professional judgment based on their knowledge of the engagements scope. A second analyst reviewed the first analysts determinations, and the two came to a consensus on which articles were in scope. Using this method, we selected 56 articles and other documents for further review. Reviewing them for relevance, we ultimately identified and used 36 articles to support findings in our report.

To conduct our data analysis, we identified national-level data sets from relevant federal agencies for six of the seven natural hazards identified by the NCA, and our review of literature, as likely to be exacerbated by climate change in the United States. The six hazards are heat, cold, wildfires, flooding, storm surge from hurricanes, and sea level rise.3 For heat and cold, we used climate projections data that incorporate emission scenarios to project future exposure to those hazards.4 For wildfires, flooding, and hurricane storm surge, we used climate data that show current conditions based on past conditions (which do not incorporate climate projections).5 For sea level rise, we used data for coastal regions and sea level rise projections from an interagency report covering sea level rise scenarios to identify coastal nuclear power plants and projected 3To identify the best available federal-level hazard data, we relied on interviews with agency officials and prior GAO reports. We did not analyze drought data because we were unable to identify national-level geospatial data that was both relevant to nuclear power plants and sufficiently reliable for our purposes.

4To analyze projected exposure to heat and cold hazards, we used NCA data on the projected exposure to maximum and minimum temperatures in the midcentury (i.e., 2036-2065), using both a low and high emission scenario for projected climate change.

5To analyze flood exposure, we used 2023 data from the Federal Emergency Management Agency that categorizes flood exposure into high, moderate, minimal or other, and unknown flood hazard categories. To analyze exposure to hurricane storm surge, we used NOAA data on storm surge exposure from Categories 1, 4, and 5 hurricanes. To analyze exposure to wildfires, we used 2023 data from the U.S. Forest Service on wildfire hazard potential.

Appendix I: Objectives, Scope, and Methodology Page 44 GAO-24-106326 Nuclear Power Plants sea level rise in their respective regions.6 In this report, we refer to these hazards collectively as selected natural hazards that may be exacerbated by climate change.

For our national-level data from federal agencies, we used data we determined to be the most appropriate to represent selected natural hazards.7 Data sources for each of the hazards we analyzed are, as follows:

Heat and cold. To analyze projected exposure to heat and cold, we used data from the fourth NCA on the projected exposure to maximum temperatures in the midcentury (i.e., 2036-2065).8 Wildfire. To analyze exposure to wildfire hazard potential, we used 2023 data from the U.S. Forest Services Wildfire Hazard Potential Map. For reporting purposes, we grouped wildfire hazard potential into the following three categories: no/low, moderate, and high/very high.9 Flooding. To analyze exposure to flood hazards, we used 2023 data from the Federal Emergency Management Agencys National Flood Hazard Layer. For reporting purposes, we grouped flood hazard 6W. V. Sweet, B. D. Hamlington, R. E. Kopp, C. P. Weaver, P. L. Barnard, D. Bekaert, W.

Brooks, M. Craghan, G. Dusek, T. Frederikse, G. Garner, A. S. Genz, J. P. Krasting, E.

Larour, D. Marcy, J. J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L.

Schmied, W. Veatch, K. D. White, and C. Zuzak, Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines, NOAA Technical Report NOS 01 (Silver Spring, MD:

February 2022).

7Data sources were chosen based on use in prior GAO reports, review of the NCA, and interviews with federal agencies responsible for collecting and reporting on data related to the selected natural hazards.

8The fifth NCA was released on November 14, 2023, after we had obtained and analyzed the hazard data sets from the fourth NCA. We reviewed relevant sections from the fifth NCA and did not identify major differences in the predicted or projected trends for the selected natural hazards.

9We combined layers of high and very high wildfire hazard potentials, which correspond to areas at the 85th percentile or greater for wildfire hazard potential. The no/low category includes plants that are in areas that are not covered by the moderate, high, or very high wildfire potential layers.

Appendix I: Objectives, Scope, and Methodology Page 45 GAO-24-106326 Nuclear Power Plants zones into the following three categories: no/low, moderate, and high.10 Hurricane storm surge. To analyze exposure to various levels of hurricane storm surge, we used data from NOAAs Sea, Lake, and Overland Surges from Hurricanes model. We used a range of categories from the data, including no exposure to hurricanes, and Categories 1, 4, and 5 hurricanes.11 Sea level rise. To analyze potential exposure to sea level rise in 2050, we used data from an interagency report covering sea level rise scenarios to illustrate regional climate projections for sea level rise in coastal regions. The data include two types of estimates-observation-based extrapolations and regionalized global mean sea level scenarios. NOAA officials recommended using these projections for our analysis of sea level rise data.

To identify nuclear power plant locations, we used nuclear power plant location data from NRC.12 We used a 0.5-mile radius around the plant coordinates provided by NRC as a proxy for approximate plant size. We based the size of the radius on approximations we made for an average U.S. nuclear power plant.13 See appendix II for further discussion of these data sources.

10No/low corresponds to areas with minimal, unknown, or other flood hazards, including areas with reduced risk because of levees as well as areas with flood hazard based on future conditions, such as the future implementation of land-use plans. Moderate flood hazard zones correspond to a 500-year floodplain, which indicates between 0.2 percent and 1 percent annual chance of flooding. High flood hazard zones correspond to a 100-year floodplain, which indicates a 1 percent or higher annual chance of flooding.

11In our analysis, we used data on storm surge from Category 1 hurricanes (the lowest possible category) and for Categories 4 and 5 hurricanes (the highest possible categories) to show a range of climate change effects.

12In March of 2023, we obtained NRC nuclear power plant coordinates for all 54 operating nuclear power plants. In July 2023, we obtained NRC nuclear power plant coordinates for the 21 nuclear power plants that have shut down and have spent nuclear fuel stored onsite in spent fuel pools or in dry cask storage. NRC provided coordinates, including a latitude and longitude value for each plant. In addition, NRCs location data file contained other identifying plant information including operating status, license number, and reactor type.

13We requested average plant size from NRC, but NRC was unable to provide these data.

Instead, we approximated the size of a typical nuclear power plant using DOE documentation on nuclear power plants.

Appendix I: Objectives, Scope, and Methodology Page 46 GAO-24-106326 Nuclear Power Plants Using hazard and nuclear power plant location data, we analyzed natural hazard exposure in the areas around nuclear power plants. In our analysis, we included operating plants and plants at various stages of decommissioning, including those in the process of decommissioning and those already shut down, with spent nuclear fuel stored onsite. We did not include experimental or test reactors in our analysis.

For certain hazards, we analyzed exposure to a range of intensities. For example, we analyzed nuclear power plant exposure to storm surge from the weakest (Category 1) and strongest (Category 5) hurricanes, as modeled by NOAA.

To analyze whether nuclear plants are located in areas that may be affected by heat, cold, wildfire, flooding, and hurricane storm surge, we used MapInfo mapping software to determine whether the nuclear power plant locations were located in areas with exposure to the selected hazards. Exposure indicates that a facility is located in an area that may be affected by a selected hazard. If the plant overlapped with multiple hazard layers, the layer representing the highest level of exposure was reported. For example, in our report, we coded a plant whose locations showed exposure to both layers for Category 1 and Category 5 storm surge data as having exposure to Category 5 storm surge.

We assessed the reliability of the fourth NCA climate projections data we used to analyze heat and cold exposure by (1) interviewing NOAA officials knowledgeable about the data and (2) reviewing existing information about the data and system that produced them.

To assess the reliability of the Federal Emergency Management Agencys National Flood Hazard Layer, NOAAs data on Sea, Lake, and Overland Surges from Hurricanes, and the U.S. Forest Services Wildfire Hazard Potential data, we reviewed prior GAO data reliability assessments for reports using the same data.14 Then, through interviews and email correspondence with NOAA, the Federal Emergency Management Agency, and U.S. Forest Service officials, we ensured that these data remained appropriate and reliable, considering any subsequent updates or changes made to the data.

14GAO, Chemical Accident Prevention: EPA Should Ensure Regulated Facilities Consider Risks from Climate Change, GAO-22-104494 (Washington, D.C.: Feb. 28, 2022) and GAO, Superfund: EPA Should Take Additional Actions to Manage Risks from Climate Change, GAO-20-73 (Washington, D.C.: Oct. 18, 2019).

Appendix I: Objectives, Scope, and Methodology Page 47 GAO-24-106326 Nuclear Power Plants To assess the reliability and appropriate use of sea level rise data for use in our analysis, we reviewed regional sea level rise data in an interagency report covering sea level rise scenarios and interviewed NOAA officials knowledgeable about sea level rise data.

To assess the reliability of NRCs data on nuclear power plant locations, we communicated with NRC staff about data accuracy and conducted limited data testing.15 As a result of the steps described above, we found the data from the NCA, the Federal Emergency Management Agency, NOAA, the U.S. Forest Service, and NRC to be sufficiently reliable for the purpose of our reporting objectives.

To examine NRCs actions to address risks to nuclear power plants from climate change, we conducted interviews and reviewed relevant agency documents. We interviewed officials from NRC headquarters, all four NRC regional offices, and two nuclear power plants. During our two nuclear power plant site visits, we interviewed plant operator staff as well as NRCs resident inspectors to assess whether NRC processes to mitigate the risks of natural hazards and extreme weather at those plants adequately consider climate change risks. We also observed an NRC safety evaluation review to understand the extent to which NRC incorporates considerations of climate change risks when determining whether and under what conditions to license a nuclear power plant.16 We reviewed relevant documents consisting of the following: relevant laws and regulations, agency documents (including guidance on probabilistic risk assessments and NRCs 2022-2026 Strategic Plan), two NRC office instructions, NRCs inspection manual on adverse weather protection, and other documents.17 We compared NRCs actions against requirements to identify any relevant gaps. We also reviewed GAOs 15Specifically, we inputted a selection of NRCs location data into mapping software to ensure NRCs latitude and longitude location data for nuclear power plants correctly corresponded to plant names and identifying information provided by NRC. Also, we compared the plant operating status of selected plants in NRCs dataset with public information to ensure the operating status of plants matched.

16This safety evaluation review was for Turkey Points Units 6 and 7, which were granted an operating license under 10 C.F.R. Part 52 but have not been built, according to NRC officials.

17NRC, Strategic Plan Fiscal Years 2022-2026, NUREG-1614, Vol. 8 (Washington, D.C.:

April 2022). See also, NRC, Inspection Manual: Adverse Weather Protection, Inspection Procedure 71111, Attachment 01 (Washington, D.C.: Jan. 1, 2018).

Appendix I: Objectives, Scope, and Methodology Page 48 GAO-24-106326 Nuclear Power Plants Standards for Internal Control in the Federal Government and compared NRCs actions against those standards.18 We conducted this performance audit from November 2022 to April 2024 in accordance with generally accepted government auditing standards.

Those standards require that we plan and perform the audit to obtain sufficient, appropriate evidence to provide a reasonable basis for our findings and conclusions based on our audit objectives. We believe the evidence obtained provides a reasonable basis for our findings and conclusions based on our audit objectives.

18GAO, Standards for Internal Control in the Federal Government, GAO-14-704G (Washington, D.C.: Sept. 10, 2014).

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise Page 49 GAO-24-106326 Nuclear Power Plants This appendix provides information on data sources we used to analyze potential exposure of nuclear power plants to selected natural hazards including heat, cold, wildfires, flooding, storm surge from hurricanes, and sea level rise. We include information, when available, on the data source name, description, purpose, update frequency, and limitations.

The U.S. Global Change Research Program posts climate projections data on its website so that authors and other users can access their data.1 The variables we used for heat and cold are part of a suite of variables intended to provide users insights into the effects of climate change on different variables under multiple emission scenarios.2 We analyzed and reported on the following heat or cold variables from the fourth National Climate Assessment (NCA):3 projected change in maximum daily temperature; 1NOAAs Technical Support Unit and the Scripps Institute of Oceanography were involved in creating these data. Together, these stakeholders contributed to creating 100 variables derived through statistical downscalinga process used to take climate model data, which are typically at a low resolution, and produce more detailed data relevant to a specific location or region. Climate projections have limitations that include uncertainties in emissions, natural variability, and differences in scientific models. Emission uncertainty refers to a climate projections reliance on emission scenarios reliant on assumptions about future emissions, changes in population, energy use, and technology. Natural variability refers to unpredictable climate events like volcanic eruptions. Scientific models refer to the way processes are understood and incorporated. For example, any change in the scientific understanding of cloud properties and ocean circulation can affect projections of future climate. In this report, we refer to these data as NCA data.

2Climate projections are based on emissions scenarios. These scenarios are produced using a range of future assumptions about underlying socioeconomic conditions, such as population and global gross domestic product projections. The climate projections data from the fourth NCA enable users to analyze projected exposure to temperature, precipitation, and other related variables by using a range of emission scenarios and time periods. Four scenarios are available, including historical climate (averages based on the 1976-2005 climate), lower (averages based on NCA assumptions for intermediate-low sea level rise, lower population, and lower development land use), higher (averages based on intermediate sea level rise, higher population, and higher development land use), and the upper bound (averages based on extreme sea level rise, higher population, and higher development land use). All four scenarios base their future projections on historical climate data for 1976-2005. These scenarios are available for three time periods, which include the early 21st Century (2016-2045), mid-21st Century (2036-2065), and late 21st Century (2070-2099).

3The fifth NCA became available in November 2023, after we had obtained and analyzed heat and cold data from the fourth NCA.

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise National Climate Assessment Heat and Cold Climate Projections Data

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise Page 50 GAO-24-106326 Nuclear Power Plants projected change in the annual days with a maximum temperature greater than the 99th percentile; projected change in the annual number of days with a maximum temperature greater than 115 degrees Fahrenheit; projected change in annual highest maximum temperature averaged over a 5-day period; and projected change in the annual number of days with a maximum temperature lower than the 1st percentile.4 The U.S. Forest Service maps wildfire hazard potential based on landscape conditions and other observations. We previously reported that the primary intended use of the wildfire hazard potential map is to identify priority areas for hazardous fuels treatments from a broad, national-to regional-scale perspective. The data do not explicitly show wildfire threat or risk.5 The U.S. Forest Service maps an index of wildfire hazard potential for the contiguous United States based on, among other factors, annual burn probabilities and potential intensity of large fires. The U.S. Forest Service categorizes the wildfire hazard potential index into five classes: very low, low, moderate, high, and very high. The U.S. Forest Service designates as high those areas with wildfire hazard potential index from the 85th to the 95th percentiles, and as very high those areas above the 95th percentile. The U.S. Forest Service also categorizes some areas as non-burnable (including agricultural lands, developed lands, and water).

As we previously reported, according to the U.S. Forest Service, areas with higher levels of wildfire hazard potential have fuels that are more likely to burn with high intensity under certain weather conditions.

However, areas with moderate, low, and very low wildfire hazard potential 4We selected temperature data using the projected change by the midcentury time frame under both a low and high emission scenario to show the range of potential projected change to selected natural hazards. The midcentury time frame was selected because it captures potential hazard effects during the period in which nuclear power plants are likely to remain operational. Other available variables include the average daily temperature and maximum 1-or 5-day precipitation. In this report, we refer to these data as NCA data.

5The objective of the wildfire hazard potential map is to depict the relative potential for wildfire that would be difficult for suppression resources to contain. The U.S. Forest Services Wildfire Hazard Potential map is available at https://doi.org/10.2737/RDS-2015-0047-4.

U.S. Forest Service Wildfire Hazard Potential Data

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise Page 51 GAO-24-106326 Nuclear Power Plants may still experience wildfires, particularly near areas with higher wildfire hazard potential.

We used 2023 wildfire hazard potential data. These data incorporated methodological changes to the fire simulation modeling to better represent probabilistic components of wildfire hazard for the fuel and climate conditions as they exist today, according to U.S. Forest Service officials we interviewed. For our analysis, we combined the high and very high wildfire hazard potential categories; we did not identify the number of facilities in each of these categories separately.

The Federal Emergency Management Agencys National Flood Hazard Layer provides data on the most current coastal and riverine flooding hazard data.6 Among other uses, the flood hazard data are used for flood insurance ratings and floodplain management. The National Flood Hazard Layer identifies areas with the highest risk of flooding, with a 1 percent or higher annual chance of flooding.7 In some locations, the National Flood Hazard Layer also identifies areas with a 0.2 percent or higher annual chance of flooding, which the Federal Emergency Management Agency considers moderate flood hazards, and other flood hazards.8 The National Flood Hazard Layer also identifies areas with minimal flood hazards, including those with less than 0.2 percent annual chance of flooding, and unknown flood hazards, including areas the Federal Emergency Management Agency has not assessed for flood hazards.

6Riverine flooding is flooding related to or caused by a river, stream, or tributary overflowing its banks because of excessive rainfall, snowmelt, or ice. The Federal Emergency Management Agency provides a tool for viewing, downloading, and printing flood maps for specific locations. The Federal Emergency Management Agencys flood hazard maps are available at https://www.fema.gov/flood-maps/national-flood-hazard-layer. Federal law requires the Federal Emergency Management Agency to assess the need to revise and update the nations flood maps once every 5 years or more often as the Administrator determines necessary. 42 U.S.C. § 4101(e).

7These areas are known as Special Flood Hazard Areas. Under federal law, in communities that participate in the National Flood Insurance Program, homeowners are required to purchase flood insurance for properties located in Special Flood Hazard Areas that are secured by mortgages from federally regulated lenders. 42 U.S.C. § 4012a(b)(1).

8Other flood hazards include areas with reduced risk because of levees, as well as areas with flood hazard based on future conditions, for example, if land use plans were implemented.

Federal Emergency Management Agency Flood Hazard Data

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise Page 52 GAO-24-106326 Nuclear Power Plants The National Oceanic and Atmospheric Administration (NOAA) provides estimates of hurricane storm surge using a model called Sea, Lake, and Overland Surges from Hurricanes.9 Estimates for storm surge are available for coastal areas in the eastern United States from Texas to Maine as well as in Hawaii, Puerto Rico, and the U.S. Virgin Islands. As of November 2023, storm surge data for coastal areas in the western United States were only available for Southern California.

The model accounts for specific shorelines by incorporating bay and river configurations, water depths, bridges, roads, levees, and other physical features. It estimates the maximum extent of storm surge at high tide by modeling hypothetical hurricanes under different storm conditions, such as landfall location, storm trajectory, and forward speed.

NOAA models storm surge for Category 1 through Category 5 hurricanes for the Atlantic coast south of the North Carolina-Virginia border, the Gulf of Mexico, Puerto Rico, and the U.S. Virgin Islands; and Category 1 through Category 4 hurricanes for the Atlantic coast north of the North Carolina-Virginia border and Hawaii.10 As we previously reported, the model is to be used for educational purposes and to increase awareness of storm surge hazards at a city or community level. According to NOAAs website, the agency updates the model for portions of the shoreline each year to account for, among other changes, new data and the addition of flood protection devices, such as levees. The model does not account for future conditions such as erosion, subsidence (i.e., the sinking of an area of land), construction, or sea level rise.

The 2022 Interagency Sea Level Rise Technical Report provides observation-based extrapolations and model-based global mean sea level scenarios as two distinct estimates of future sea level rise. Observation-based extrapolations use observed changes in sea level rise to estimate 9According to NOAA, storm surge is an abnormal rise of water generated by a storm, over and above the predicted tides. Storm surge is produced by water being pushed toward the shore by the force of the storms winds. NOAAs storm surge hazard maps are available at https://www.nhc.noaa.gov/nationalsurge/.

10We previously reported that NOAA does not estimate storm surge for Category 5 hurricanes in areas where such hurricanes have not historically made landfall, such as areas north of the North Carolina-Virginia border.

National Oceanic and Atmospheric Administration Storm Surge Hazard Data 2022 Interagency Sea Level Rise Technical Report Sea Level Rise Data

Appendix II: Available Federal Data on Heat, Cold, Wildfires, Flooding, Storm Surge, and Sea Level Rise Page 53 GAO-24-106326 Nuclear Power Plants the trajectory of sea level rise.11 Model-based-global mean sea level scenarios use emission scenarios to estimate future sea level rise. The 2022 Interagency Sea Level Rise Technical Report provides both types of estimates for sea level rise in 2050 (relative to a baseline of the year 2000) for eight coastal regions of the United States. Formed by analyzing aggregated tide gauge data, the regional boundary data that NOAA provided our team include the Northeast (Maine to Virginia), the Southeast (North Carolina to the east coast of Florida), the Eastern Gulf (west coast of Florida to Mississippi), the Western Gulf (Louisiana to Texas), the Southwest (California), the Northwest (Oregon to Washington), the Hawaiian Islands, and the Caribbean.

The 2022 Interagency Sea Level Rise Technical Report providing the sea level rise estimates and coastal regions is intended to help inform federal agencies, Tribes, state and local governments, and stakeholders in coastal communities about current and future sea level rise.12 The two primary limitations that the report discusses for the sea level rise estimates we use include process uncertainty and emission uncertainty.

Process uncertainty refers to uncertainty about the impact of emissions on ice sheet loss, ocean expansion, and local ocean dynamics. Emission uncertainty refers to the uncertain amount of greenhouse gas emissions that will enter the atmosphere, trap heat, and affect temperature and sea level rise.

11The observation-based extrapolations are intended to serve as a comparison with the model-based-global mean sea level scenarios.

12W. V. Sweet, B. D. Hamlington, R. E. Kopp, C. P. Weaver, P. L. Barnard, D. Bekaert, W.

Brooks, M. Craghan, G. Dusek, T. Frederikse, G. Garner, A. S. Genz, J. P. Krasting, E.

Larour, D. Marcy, J. J. Marra, J. Obeysekera, M. Osler, M. Pendleton, D. Roman, L.

Schmied, W. Veatch, K. D. White, and C. Zuzak, 2022: Global and Regional Sea Level Rise Scenarios for the United States: Updated Mean Projections and Extreme Water Level Probabilities Along U.S. Coastlines, NOAA Technical Report NOS 01 (Silver Spring, MD: February 2022).

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 54 GAO-24-106326 Nuclear Power Plants Table 1 shows the exposure of areas around operating nuclear power plant locations to six current or projected natural hazards: flooding, hurricane storm surge, wildfire, sea level rise, heat, and cold. Data for flooding, hurricane storm surge, and wildfire are current and based on historical observation data. Data for sea level rise and heat and cold temperature variables are climate projections data, which incorporate emission scenarios. For more information about the data sources used, see appendix II.

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 55 GAO-24-106326 Nuclear Power Plants Table 1: Potential Exposure to Current and Future Hazards at Operating Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Browns Ferry AL High No exposure None/

low N/A 3.74, 4.61°F 21.07, 29.35 days 0.01, 0.05 days 5.05, 6.32°F

-1.86,

-2.18 days Joseph M.

Farley AL High No exposure Moderate 1.0, 1.7 ft.

3.53, 4.33°F 19.79, 28.87 days 0.01, 0.02 days 4.33, 5.44°F

-1.88, -2.27 days Arkansas Nuclear One AR High No exposure Moderate N/A 3.90, 4.85°F 14.15, 20.63 days 0.09, 0.17 days 4.94, 6.10°F

-2.01,

-2.25 days Palo Verde AZ Moderate No exposure None/

low N/A 3.64, 4.73°F 16.66, 24.67 days 15.09, 22.64 days 3.82, 4.85°F

-2.34,

-2.72 days SAFER Phoenixk AZ High No exposure High/

very high N/A 3.59, 4.66°F 19.21, 28.16 days 12.86, 19.86 days 4.31, 5.32°F

-2.09,

-2.52 days Diablo Canyon CA High No exposure High/

very high 0.5, 1.2 ft.

2.59, 3.27°F 5.14, 7.10 days 0,

0 days 3.56, 4.35°F

-2.49,

-2.82 days Millstone CT High Category 4

None/

low 1.2, 1.8 ft.

3.38, 4.32°F 8.28, 12.78 days 0,

0 days 3.52, 4.76°F

-2.37,

-2.77 days St. Lucie FL High Category 5

Moderate 0.9, 1.6 ft.

3.05, 3.99°F 37.60, 60.07 days 0,

0 days 3.52, 4.60°F

-1.52,

-2.05 days Turkey Point FL High Category 5

High/

very high 0.9, 1.6 ft.

2.91, 3.75°F 54.28, 79.80 days 0,

0 days 3.11, 3.94°F

-1.99,

-2.40 days Edwin I.

Hatch GA High No exposure High/

very high 0.9, 1.6 ft.

3.39, 4.22°F 20.62, 30.21 days 0,

0.01 days 4.38, 5.56°F

-1.78,

-2.25 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 56 GAO-24-106326 Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Vogtle GA No/low No exposure High/

very high 0.9, 1.6 ft.

3.54, 4.38°F 16.23, 22.88 days 0.01, 0.01 days 4.30, 5.41°F

-2.02,

-2.41 days Braidwood IL No/low No exposure None/

low N/A 4.26, 5.35°F 16.66, 24.74 days 0.01, 0.01 days 5.06, 6.57°F

-2.48,

-2.76 days Byron IL No/low No exposure None/

low N/A 4.37, 5.46°F 15.92, 24.51 days 0,

0 days 5.26, 6.88°F

-2.61,

-2.84 days Clinton IL High No exposure None/

low N/A 4.35, 5.35°F 19.12, 26.98 days 0.05, 0.03 days 5.50, 6.87°F

-2.41,

-2.74 days Dresden IL High No exposure None/

low N/A 4.27, 5.38°F 17.00, 25.26 days 0.01, 0.01 days 5.08, 6.61°F

-2.52,

-2.80 days LaSalle IL No/low No exposure None/

low N/A 4.28, 5.40°F 16.67, 24.88 days 0.02, 0.01 days 5.21, 6.79°F

-2.47,

-2.77 days Quad Cities IL High No exposure None/

low N/A 4.20, 5.22°F 17.12, 25.92 days 0.01, 0 days 5.20, 6.73°F

-2.45,

-2.70 days Wolf Creek KS High No exposure None/

low N/A 3.91, 4.91°F 11.36, 16.85 days 0.15, 0.22 days 4.92, 6.16°F

-1.87,

-2.26 days River Bend LA No/low No exposure None/

low 1.6, 2.3 ft.

3.09, 3.91°F 29.25, 41.28 days 0,

0 days 3.85, 4.88°F

-1.33,

-1.70 days Waterford LA No/low Category 5

None/

low 1.6, 2.3 ft.

2.88, 3.59°F 22.43, 33.67 days 0,

0 days 3.14, 4.04°F

-1.70,

-2.04 days Calvert Cliffs MD High Category 4

Moderate 1.2, 1.8 ft.

3.62, 4.58°F 16.21, 24.27 days 0,

0 days 4.75, 6.22°F

-2.32,

-2.61 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 57 GAO-24-106326 Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Donald C.

Cook MI High No exposure None/

low N/A 4.25, 5.43°F 16.75, 25.52 days 0,

0 days 5.23, 6.85°F

-2.67,

-2.97 days Fermi MI High No exposure None/

low N/A 4.18, 5.29°F 15.12, 23.04 days 0,

0 days 5.29, 7.01°F

-2.84, -3.09 days Monticello MN High No exposure Moderate N/A 4.36, 5.41°F 14.72, 22.40 days 0,

0 days 5.27, 6.87°F

-2.72,

-2.96 days Prairie Island MN High No exposure None/

low N/A 4.44, 5.51°F 14.28, 22.42 days 0,

0 days 4.86, 6.45°F

-2.78,

-3.00 days Callaway MO No/low No exposure None/

low N/A 4.34, 5.33°F 15.36, 23.26 days 0.15, 0.22 days 5.71, 7.11°F

-2.31,

-2.54 days Grand Gulf MS High No exposure None/

low 1.6, 2.3 ft.

3.72, 4.59°F 24.81, 34.84 days 0,

0.01 days 4.30, 5.46°F

-1.93,

-2.18 days Brunswick NC High Category 5

High/

very high 0.9, 1.6 ft.

2.67, 3.39°F 12.00, 18.35 days 0,

0 days 3.02, 3.91°F

-1.94,

-2.28 days McGuire NC High No exposure High/

very high N/A 3.89, 4.82°F 17.41, 24.70 days 0,

0.02 days 4.64, 5.91°F

-2.07,

-2.36 days Shearon Harris NC High No exposure High/

very high 0.9, 1.6 ft.

3.79, 4.73°F 17.66, 25.38 days 0,

0.01 days 4.47, 5.72°F

-2.05,

-2.37 days Cooper NE High No exposure High/

very high N/A 4.32, 5.32°F 12.21, 18.53 days 0.05, 0.09 days 5.09, 6.55°F

-2.26,

-2.46 days Seabrook NH High Category 4

None/

low 1.2, 1.8 ft.

3.72, 4.77°F 9.24, 13.56 days 0,

0 days 3.89, 5.18°F

-2.72,

-3.07 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 58 GAO-24-106326 Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Hope Creek NJ High Category 4

None/

low 1.2, 1.8 ft.

3.74, 4.79°F 12.70, 19.86 days 0,

0 days 4.24, 5.71°F

-2.63,

-2.95 days Salem NJ High Category 4

None/

low 1.2, 1.8 ft.

3.74, 4.79°F 12.70, 19.86 days 0,

0 days 4.24, 5.71°F

-2.63,

-2.95 days James A.

FitzPatrick NY High No exposure None/

low N/A 4.06, 5.16°F 14.59, 21.08 days 0,

0 days 4.87, 6.44°F

-2.65,

-3.06 days Nine Mile Point NY High No exposure None/

low N/A 4.06, 5.16°F 14.59, 21.08 days 0,

0 days 4.87, 6.44°F

-2.65,

-3.06 days R. E. Ginna NY No/low No exposure High/

very high N/A 4.39, 5.53°F 14.43, 20.97 days 0,

0.01 days 4.98, 6.72°F

-2.84, -3.15 days Davis-Besse OH High No exposure None/

low N/A 4.06, 5.08°F 15.18, 22.48 days 0,

0 days 4.93, 6.46°F

-2.71,

-2.98 days Perry OH High No exposure None/

low N/A 4.27, 5.41°F 15.04, 23.08 days 0,

0 days 4.82, 6.35°F

-2.82,

-3.07 days Beaver Valley PA High No exposure None/

low N/A 3.76, 4.79°F 16.38, 24.97 days 0,

0 days 4.84, 6.54°F

-2.55,

-2.87 days Limerick PA High No exposure None/

low 1.2, 1.8 ft.

3.88, 4.91°F 13.22, 20.69 days 0,

0 days 4.96, 6.66°F

-2.57,

-2.87 days Peach Bottom PA High No exposure None/

low 1.2, 1.8 ft.

4.06, 5.08°F 16.27, 24.13 days 0,

0 days 5.20, 6.79°F

-2.56,

-2.89 days Susquehanna PA Moderate No exposure Moderate 1.2, 1.8 ft.

4.23, 5.27°F 15.05, 21.82 days 0,

0.02 days 5.58, 7.13°F

-2.69,

-3.00 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 59 GAO-24-106326 Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Catawba SC High No exposure High/

very high N/A 4.00, 4.96°F 18.27, 25.53 days 0,

0.03 days 4.73, 6.02°F

-2.05,

-2.30 days H. B.

Robinson SC High No exposure High/

very high 0.9, 1.6 ft.

3.57, 4.44°F 15.03, 21.81 days 0,

0.01 days 4.39, 5.59°F

-1.94,

-2.29 days Oconee SC High No exposure Moderate N/A 3.66, 4.54°F 19.32, 26.96 days 0,

0.03 days 4.86, 6.22°F

-1.56,

-1.89 days Virgil C.

Summer SC High No exposure Moderate 0.9, 1.6 ft.

3.55, 4.50°F 15.91, 22.53 days 0.01, 0.05 days 4.50, 5.72°F

-1.71,

-2.12 days SAFER Memphisk TN No/low No exposure None/

low N/A 3.99, 4.85°F 21.63, 31.04 days 0.01, 0.04 days 5.09, 6.41°F

-1.98,

-2.24 days Sequoyah TN High No exposure Moderate N/A 3.70, 4.55°F 19.20, 26.92 days 0,

0.01 days 4.99, 6.30°F

-1.68,

-2.04 days Watts Bar TN High No exposure Moderate N/A 3.70, 4.59°F 18.75, 26.76 days 0,

0.01 days 4.78, 6.04°F

-1.90,

-2.22 days Comanche Peak TX High No exposure Moderate N/A 3.69, 4.67°F 14.75, 21.52 days 0.18, 0.62 days 4.07, 5.42°F

-1.89,

-2.15 days South Texas Project TX No/low Category 5

None/

low 1.6, 2.3 ft.

2.93, 3.74°F 22.77, 34.60 days 0,

0 days 3.16, 3.99°F

-1.62, -1.90 days North Anna VA High No exposure Moderate 1.2, 1.8 ft.

3.82, 4.83°F 18.28, 26.64 days 0.01, 0.02 days 4.95, 6.43°F

-2.20,

-2.55 days Surry VA High Category 4

None/

low 1.2, 1.8 ft.

3.47, 4.40°F 13.85, 21.08 days 0,

0 days 3.96, 5.17°F

-2.36,

-2.68 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 60 GAO-24-106326 Nuclear Power Plants Source: GAO analysis of data from the fourth National Climate Assessment (NCA), U.S. Forest Service, National Oceanic and Atmospheric Administration (NOAA), the 2022 Interagency Sea Level Rise Technical Report, the Federal Emergency Management Agency, and the Nuclear Regulatory Commission (NRC). I GAO-24-106326 aTo identify plant locations, we used nuclear power plant coordinates from NRC and added a one-half-mile radius around NRCs plant coordinates to approximate the size of a nuclear power plant. To analyze whether nuclear plants are located in areas that may be affected by heat, cold, wildfire, hurricane storm surge, and flooding, we used MapInfo mapping software to determine whether the nuclear power plant locations are located in areas with exposure to the natural hazards. Exposure indicates that a facility is located in an area that may be affected by the selected hazard. If the plant overlapped with multiple hazard layers, the layer representing the highest level of exposure was reported.

bTo analyze exposure to flood hazards, we used 2023 data from Federal Emergency Management Agencys National Flood Hazard Layer. We grouped flood hazard zones into three categories: no/low, moderate, and high. No/low refers to areas with minimal, unknown, or other flood hazards, including areas with reduced risk because of levees as well as areas with flood hazard based on future conditions, such as the future implementation of land-use plans. Moderate corresponds to a 500-year floodplain, which indicates between 0.2 percent and 1 percent annual chance of flooding. High corresponds to a 100-year floodplain, which indicates a 1 percent or higher annual chance of flooding.

cTo analyze exposure to various levels of hurricane storm surge, we used data from NOAAs Sea, Lake, and Overland Surges from Hurricanes model. We used a range of categories from the data, including no exposure to hurricanes, and Category 1, and 4, and 5 hurricanes.

dTo analyze exposure to wildfire hazard potential, we used 2023 data from the U.S. Forest Services Wildfire Hazard Potential Map. None/low refers to plants in areas that are not covered by the moderate, high, or very high wildfire potential layers. Moderate refers to plants in areas with moderate wildfire hazard potential. High/very high refers to plants in areas with high or very high wildfire hazard potential.

eTo analyze potential exposure to sea level rise in 2050, we used data from an interagency report covering sea level rise scenarios to illustrate climate projections for sea level rise in coastal regions, under both a low and high scenario in the regions.

fProjected change in daily max. temp. refers to the projected change in daily maximum temperature by the midcentury (i.e., 2036-2065) using both a low-and high emission scenario for projected climate change from the fourth NCA. Values are measured in degrees Fahrenheit.

gProjected change in max. temp. exceeding historical highs refers to the change in the annual number of days with a maximum temperature greater than the 99th percentile by the midcentury (i.e., 2036-2065), using both a low and high emission scenario for projected climate change from the fourth NCA. This Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/

year)h Projected change in 5-day max.

temp., low and high emission scenarios,

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios (days/ year)j Columbia WA No/low No exposure High/

very high N/A 3.90, 4.87°F 9.56, 14.05 days 0.01, 0.06 days 4.15, 5.29°F

-1.64,

-1.88 days Point Beach WI High No exposure None/

low N/A 3.91, 4.93°F 10.01, 15.74 days 0,

0 days 4.58, 6.13°F

-2.48,

-2.78 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 61 GAO-24-106326 Nuclear Power Plants variable measures the annual number of days when the highest temperature of the day exceeds the hottest (99th percentile of) historical (1976-2005) high temperatures. Values are measured in number of days per year.

hProjected change in max. temp. over 115°F refers to the projected change in annual number of days with a maximum temperature over 115°F by the midcentury (i.e., 2036-2065) using both a low and high emission scenario for projected climate change from the fourth NCA. Values are measured in number of days per year.

IProjected change in 5-day max. temp. refers to the projected change in highest maximum temperature averaged over a 5-day period by the midcentury (i.e.,

2036-2065) using both a low and a high emission scenario for projected climate change from the fourth NCA. Values are measured in degrees Fahrenheit.

jProjected change in min. temp. below historical lows refers to projected change in the annual number of days with a maximum temperature lower than the 1st percentile by the midcentury (i.e., 2036-2065), using both a low and high emission scenario for projected climate change from the fourth NCA. This variable measures the annual number of days when the highest temperature of the day is lower than the coldest (1st percentile of) historical (1976-2005) high temperatures. A negative value indicates that there will be fewer days when the daily highest temperature falls below the 1st percentile. Values are measured in number of days per year.

kThe nuclear power industry operates two Strategic Alliance for FLEX Emergency Response (SAFER) centers that maintain emergency equipment that can be provided to plants as a backup to a plants onsite primary backup equipment.

Table 2 shows the exposure of areas around shutdown nuclear power plant locations to six current or projected natural hazards: flooding, hurricane storm surge, wildfire, sea level rise, heat, and cold.1 Data for flooding, hurricane storm surge, and wildfire are current data and based on historical observation data. Data for sea level rise and heat and cold temperature variables are climate projections data, which incorporate emission scenarios.

For more information about the data sources used, see appendix II.

1We included plants at various stages of decommissioning, including those in the process of decommissioning and those already decommissioned, with spent nuclear fuel stored onsite. We refer to these as shutdown plants because they are no longer operational.

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 62 GAO-24-106326 Nuclear Power Plants Table 2: Potential Exposure to Current and Future Hazards at Shutdown Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/ year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/ year)h Projected change in 5-day max.

temp., low and high emission scenarios

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios(days/

year)j Humboldt Bay CA High No exposure Moderate 0.5, 1.2 ft.

2.65, 3.43°F 8.70, 14.32 days 0,

0 days 3.22, 4.20°F

-2.36,

-2.68 days Rancho Seco CA High No exposure Moderate 0.5, 1.2 ft.

3.35, 4.26°F 10.78, 15.07 days 0.12, 0.26 days 4.29, 5.35°F

-2.28,

-2.65 days San Onofre CA High Category 1

High/

very high 0.5, 1.2 ft.

2.52, 3.34°F 6.59, 9.92 days 0,

0 days 3.10, 3.93°F

-2.66,

-3.01 days Fort Saint Vrain CO No/low No exposure Moderate N/A 4.43, 5.55°F 20.00, 27.98 days 0,

0 days 5.07, 6.48°F

-1.43,

-1.83 days Haddam Neck CT High Category 4

Moderate 1.2, 1.8 ft.

3.64, 4.69°F 9.65, 15.07 days 0,

0 days 3.86, 5.24°F

-2.42,

-2.80 days Crystal River FL High Category 5

High/

very high 1.0, 1.7 ft.

3.01, 3.87°F 34.35, 52.84 days 0,

0 days 3.24, 4.22°F -1.76, -2.22 days Duane Arnold IA High No exposure None/ low N/A 4.50, 5.55°F 17.40, 26.03 days 0.01, 0.02 days 5.47, 7.04°F

-2.60,

-2.80 days Zion IL High No exposure None/ low N/A 4.18, 5.25°F 13.44, 20.26 days 0.01, 0.01 days 5.20, 6.80°F

-2.41,

-2.65 days Pilgrim MA High Category 4

Moderate 1.2, 1.8 ft.

3.23, 4.12°F 7.35, 10.76 days 0,

0 days 3.53, 4.60°F

-2.06,

-2.44 days Yankee Rowe MA No/low No exposure None/ low 1.2, 1.8 ft.

4.24, 5.52°F 11.92, 18.63 days 0,

0 days 4.82, 6.74°F

-2.73,

-3.07 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 63 GAO-24-106326 Nuclear Power Plants Planta State Flood hazard levelb Hurricane storm surge levelc Wildfire potential leveld Projected regional sea level rise in 2050, low and high emission scenarios (feet)e Projected change in max. daily temp., low and high emission scenarios

(°Fahrenheit)f Projected change in max. temp.

exceeding historical highs, low and high emission scenarios (days/ year)g Projected change in max. temp.

over 115°F, low and high emission scenarios (days/ year)h Projected change in 5-day max.

temp., low and high emission scenarios

(°Fahrenheit)i Projected change in max.

temp. below historical lows, low and high emission scenarios(days/

year)j Maine Yankee ME High Category 4

None/ low 1.2, 1.8 ft.

3.74, 4.85°F 9.87, 14.50 days 0,

0 days 4.09, 5.41°F

-2.58,

-2.9 days Big Rock Point MI High No exposure None/ low N/A 4.22, 5.39°F 11.06, 17.29 days 0,

0 days 4.13, 5.71°F

-3.02,

-3.28 days Palisades MI High No exposure None/ low N/A 3.84, 4.92°F 13.75, 21.03 days 0,

0 days 4.35, 5.78°F

-2.61,

-2.99 days Fort Calhoun NE High No exposure Moderate N/A 4.26, 5.32°F 13.67, 20.69 days 0.01, 0.01 days 4.78, 6.15°F

-2.32,

-2.58 days Oyster Creek NJ High Category 4

High/

very high 1.2, 1.8 ft.

3.60, 4.54°F 9.99, 14.93 days 0,

0 days 4.33, 5.65°F

-2.51,

-2.81 days Indian Point NY High Category 4

High/

very high 1.2, 1.8 ft.

3.78, 4.84°F 12.33, 18.84 days 0,

0 days 4.78, 6.39°F

-2.63,

-3.00 days Trojan OR High No exposure Moderate 0.3, 1 ft.

3.44, 4.37°F 6.64, 10.03 days 0,

0 days 4.19, 5.32°F

-1.96,

-2.22 days Three Mile Island PA High No exposure None/ low 1.2, 1.8 ft.

4.14, 5.21°F 14.66, 21.37 days 0.01, 0.05 days 5.68, 7.31°F

-2.78,

-3.05 days Vermont Yankee VT High No exposure None/ low 1.2, 1.8 ft.

3.77, 4.89°F 13.48, 21.03 days 0,

0 days 4.80, 6.64°F

-2.48,

-2.84 days Kewaunee WI No/low No exposure None/ low N/A 3.92, 4.96°F 9.50, 14.96 days 0,

0 days 4.38, 5.92°F

-2.59,

-2.88 days Lacrosse WI High No exposure None/ low N/A 4.31, 5.38°F 17.34, 26.24 days 0,

0 days 5.30, 6.96°F

-2.58,

-2.79 days

Appendix III: Nuclear Power Plant Exposure to Selected Natural Hazards Page 64 GAO-24-106326 Nuclear Power Plants Source: GAO analysis of data from the fourth National Climate Assessment (NCA), U.S. Forest Service, National Oceanic and Atmospheric Administration (NOAA), the 2022 Interagency Sea Level Rise Technical Report, the Federal Emergency Management Agency, and the Nuclear Regulatory Commission (NRC). I GAO-24-106326 aTo identify plant locations, we used nuclear power plant coordinates from NRC and added a one-half-mile radius around NRCs plant coordinates to approximate the size of a nuclear power plant. To analyze whether nuclear plants are located in areas that may be affected by heat, cold, wildfire, hurricane storm surge, and flooding, we used MapInfo mapping software to determine whether the nuclear power plant locations are located in areas with exposure to the natural hazards. Exposure indicates that a facility is located in an area that may be affected by the selected hazard. If the plant overlapped with multiple hazard layers, the layer representing the highest level of exposure was reported.

bTo analyze exposure to flood hazards, we used 2023 data from Federal Emergency Management Agencys National Flood Hazard Layer. We grouped flood hazard zones into three categories: no/low, moderate, and high. No/low refers to areas with minimal, unknown, or other flood hazards, including areas with reduced risk because of levees as well as areas with flood hazard based on future conditions, such as the future implementation of land-use plans. Moderate corresponds to a 500-year floodplain, which indicates between 0.2 percent and 1 percent annual chance of flooding. High corresponds to a 100-year floodplain, which indicates a 1 percent or higher annual chance of flooding.

cTo analyze exposure to various levels of hurricane storm surge, we used data from NOAAs Sea, Lake, and Overland Surges from Hurricanes model. We used a range of categories from the data, including no exposure to hurricanes, and Category 1, and 4, and 5 hurricanes.

dTo analyze exposure to wildfire hazard potential, we used 2023 data from the U.S. Forest Services Wildfire Hazard Potential Map. None/low refers to plants in areas that are not covered by the moderate, high, or very high wildfire potential layers. Moderate refers to plants in areas with moderate wildfire hazard potential. High/very high refers to plants in areas with high or very high wildfire hazard potential.

eTo analyze potential exposure to sea level rise in 2050, we used data from an interagency report covering sea level rise scenarios to illustrate climate projections for sea level rise in coastal regions, under both a low and high scenario in the regions.

fProjected change in daily max. temp. refers to the projected change in daily maximum temperature by the midcentury (i.e., 2036-2065) using both a low-and high emission scenario for projected climate change from the fourth NCA. Values are measured in degrees Fahrenheit.

gProjected change in max. temp. exceeding historical highs refers to the change in the annual number of days with a maximum temperature greater than the 99th percentile by the midcentury (i.e., 2036-2065), using both a low and high emission scenario for projected climate change from the fourth NCA. This variable measures the annual number of days when the highest temperature of the day exceeds the hottest (99th percentile of) historical (1976-2005) high temperatures. Values are measured in number of days per year.

hProjected change in max. temp. over 115°F refers to the projected change in annual number of days with a maximum temperature over 115°F by the midcentury (i.e., 2036-2065) using both a low and high emission scenario for projected climate change from the fourth NCA. Values are measured in number of days per year.

iProjected change in 5-day max. temp. refers to the projected change in highest maximum temperature averaged over a 5-day period by the midcentury (i.e.,

2036-2065) using both a low and a high emission scenario for projected climate change from the fourth NCA. Values are measured in degrees Fahrenheit.

jProjected change in min. temp. below historical lows refers to projected change in the annual number of days with a maximum temperature lower than the 1st percentile by the midcentury (i.e., 2036-2065), using both a low and high emission scenario for projected climate change from the fourth NCA. This variable measures the annual number of days when the highest temperature of the day is lower than the coldest (1st percentile of) historical (1976-2005) high temperatures. A negative value indicates that there will be fewer days when the daily highest temperature falls below the 1st percentile. Values are measured in number of days per year.

Appendix IV: Comments from the Nuclear Regulatory Commission Page 65 GAO-24-106326 Nuclear Power Plants Appendix IV: Comments from the Nuclear Regulatory Commission

Appendix IV: Comments from the Nuclear Regulatory Commission Page 66 GAO-24-106326 Nuclear Power Plants

Appendix V: GAO Contact and Staff Acknowledgments Page 67 GAO-24-106326 Nuclear Power Plants Frank Rusco, at (202) 512-3841 or ruscof@gao.gov In addition to the contact named above, Janice Ceperich (Assistant Director), Marissa Dondoe (Analyst-in-Charge), Bethany Benitez, Colleen Candrl, Breanne Cave, Lilia Chaidez, John Delicath, Cindy Gilbert, Claire McLellan, John Mingus, Katrina Pekar-Carpenter, Dan C. Royer, Wesley Sholtes, John Tanis, Joseph Dean Thompson, Linda Tsang, and Kristen Watts made significant contributions to this report.

Appendix V: GAO Contact and Staff Acknowledgments GAO Contact Staff Acknowledgments

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8 UNITED STATES OF AMERICA NUCLEAR REGULATORY COMMISSION BEFORE THE ATOMIC SAFETY AND LICENSING BOARD

)

In the Matter of

)

Virginia Electric Power Co.

)

Docket Nos. 50-338/339 SLR North Anna Power Station, Units 1 and 2

)

___________________________________ )

CERTIFICATE OF SERVICE I certify that on April 11, 2024, I posted MOTION BY BEYOND NUCLEAR AND THE SIERRA CLUB TO AMEND THEIR CONTENTION 3 REGARDING FAILURE TO CONSIDER ENVIRONMENTAL IMPACTS OF CLIMATE CHANGE and Attachment A on the NRCs Electronic Information Exchange.

___/signed electronically by/__

Paul Gunter