SERIES TITLE OPTIONAL “Advanced” Isn’t Always Better Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors “Advanced” Isn’t Always Better Assessing the Safety, Security, and Environmental Impacts of Non-Light-Water Nuclear Reactors Edwin Lyman March 2021 © 2021 Union of Concerned Scientists All Rights Reserved Edwin Lyman is the director of nuclear power safety in the UCS Climate and Energy Program. The Union of Concerned Scientists puts rigorous, independent science to work to solve our planet’s most pressing problems. Joining with people across the country, we combine technical analysis and effective advocacy to create innovative, practical solutions for a healthy, safe, and sustainable future. This report is available online (in PDF format) at www.ucsusa.org/resources/ advanced-isnt-always-better and https:// doi.org/10.47923/2021.14000 Designed by: David Gerratt, Acton, MA www.NonprofitDesign.com Cover photo: Argonne National Laboratory/Creative Commons (Flickr) Printed on recycled paper. ii union of concerned scientists [ contents ] vi Figures, Tables, and Boxes vii Acknowledgments executive summary 2 Key Questions for Assessing NLWR Technologies 2 Non-Light Water Reactor Technologies 4 Evaluation Criteria 5 Assessments of NLWR Types 8 Safely Commercializing NLWRs: Timelines and Costs 9 The Future of the LWR 9 Conclusions of the Assessment 11 Recommendations 12 Endnotes chapter 1 13 Nuclear Power: Present and Future 13 Slower Growth, Cost and Safety Concerns 14 Can Non-Light-Water Reactors Revive Nuclear Power’s Prospects? 15 A Note on Terminology 15 The Need to Fully Vet Claims About NLWRs 16 NLWRs: Past and Present 19 A Host of Challenges Even for More Mature NLWR Designs 22 Nuclear Power Growth and Climate Change Mitigation 22 Is Development of NLWRs Essential for Nuclear Power’s Future? chapter 2 24 Nuclear Power Basics 24 Nuclear Chain Reactions in the Reactor Core 25 The Components of Nuclear Fuels 28 Thermal and Fast Reactors “Advanced” Isn’t Always Better iii 29 Fuel Burnup and Refueling 30 Reactor Safety Considerations chapter 3 32 Nuclear Power Sustainability 32 Two Primary Goals for Increasing Sustainability 33 The Challenging and Conflicting Goals of Sustainability 34 High-Level Waste Reduction 39 Uranium Utilization Efficiency chapter 4 43 Nuclear Proliferation and Terrorism Risks of Nuclear Power 44 International Standards for Detecting Diversion of Nuclear Materials and Protecting Them from Theft 46 NLWRs: Enrichment Issues 47 Nuclear Terrorism and Proliferation Concerns of HALEU 49 Reprocessing and NLWRs chapter 5 55 Liquid Sodium–Cooled Fast Reactors 55 History and Current Status 57 Fast Reactors: Cost Considerations 59 Safety 66 Sustainability and Proliferation/Terrorism Risk 66 Sustainability of Once-Through Fast Reactors 67 Time Scale and Costs chapter 6 74 High-Temperature Gas–Cooled Reactors 74 The Technology 75 History and Current Status 77 Safety 81 Sustainability iv union of concerned scientists 83 Proliferation/Terrorism Risk 8 5 Readiness for Commercial Demonstration and Near-Term Deployment chapter 7 89 Molten Salt Reactors 90 History and Current Status 91 Safety 94 Sustainability 102 Proliferation/Terrorism Risk 104 Readiness for Commercial Demonstration and Deployment chapter 8 107 Breed-and-Burn Reactors 107 The Rationale for Breed-and-Burn Reactors 110 Breed-and-Burn Reactor Designs 112 Sustainability 113 Proliferation/Terrorism Risk chapter 9 115 Conclusions and Recommendations 115 Conclusions 116 Recommendations appendix 118 Simple Models of Fast Burner/Breeder Cycles 118 How Long Would It Take to Reduce Transuranics by a Factor of 10 with a Burner Reactor System? 120 How Long Would It Take for a Fast Breeder Reactor to Extract 100 Times As Much Energy from Uranium Ore as an LWR? 122 Uranium Utilization Efficiency of Burner Reactors vs. Breeder Reactors 122 Waste Reduction Factor of a Breeder Reactor 124 Endnotes 126 References “Advanced” Isn’t Always Better v [ figures, tables, and boxes ] figures 119 Figure A.1. Heavy Metal Mass Flow for Startup and Transition Core for a Fast Burner Reactor 119 Figure A-2. Annual Heavy Metal Mass Flow at Equilibrium for a Fast Burner Reactor 121 Figure A-3. Production of Initial Core and First Reload for a Fast Breeder Reactor 121 Figure A-4. Annual Heavy Metal Mass Flow at Equilibrium for a Fast Breeder Reactor tables 4 Table ES-1. Current Status of US NLWR Projects 6 Table ES-2. How NLWRs Compare with LWRs on Safety, Sustainability, and Proliferation Risk 17 Table 1. Past and Present Demonstration Reactors Worldwide boxes 19 Box 1. Stages of Advanced Reactor Development 26 Box 2. Reactor Stability: Controlling the Chain Reaction 37 Box 3. Reprocessing and Recycling: Turning Spent Fuel into Fresh Fuel 38 Box 4. What Level of Transuranic Reduction in Radioactive Waste Would Make a Real Difference? 50 Box 5. The Ups and Downs of US Reprocessing Policy 61 Box 6. Reactivity Effects in Fast Reactors 71 Box 7. The Pyroprocessing Files 95 Box 8. Protactinium and the Thorium Fuel Cycle 99 Box 9. Transatomic Power: A Cautionary Tale vi union of concerned scientists [ acknowledgments ] This report was made possible with the support of the John D. and Catherine T. MacArthur Foundation and UCS members. The author would like to thank the many UCS staff members, past and present, who provided invaluable input into this report: Angela Anderson, Rachel Cleetus, Rob Cowin, Peter Frumhoff, Lisbeth Gronlund, Kathleen Rest, and Steve Clemmer. He would like to thank Steve Fetter, Richard Garwin, Scott Kemp, and Frank von Hippel for reviewing the report and providing useful comments. He is very grateful to Cynthia DeRocco and Bryan Wadsworth for overseeing the report’s production, and to Hannah Poor and Sital Sathia for their invaluable assistance. Finally, he would like to thank Karin Matchett, Marc S. Miller, and Heather Tuttle for their excellent editing and David Gerratt for his deft layout and design. Organizational affiliations are listed for identification purposes only. The opinions expressed herein do not necessarily reflect those of the organizations that funded the work or the individuals who reviewed it. The Union of Concerned Scientists bears sole responsibility for the report’s contents. “Advanced” Isn’t Always Better vii Executive Summary The future of nuclear power is uncertain. Because nuclear the Nuclear Regulatory Commission (NRC) received applica- power is a low-carbon way to generate electricity, there is tions to build more than two dozen new reactors. All were considerable interest in expanding its role to help mitigate evolutionary versions of the light-water reactor (LWR), the the threat of climate change. However, the technology has type that comprises almost all operating reactors in the Unit- fundamental safety and security disadvantages compared ed States and most other countries with nuclear power. Com- with other low-carbon sources. Nuclear reactors and their panies such as Westinghouse, which developed the AP1000, associated facilities for fuel production and waste handling promised these LWR variants could be built more quickly and are vulnerable to catastrophic accidents and sabotage, and cheaply while enhancing safety. But prospective purchasers they can be misused to produce materials for nuclear weapons. cancelled nearly all of those proposals even before ground The nuclear industry, policymakers, and regulators must was broken, and the utilities that started building two AP1000 address these shortcomings fully if the global use of nuclear reactors at the V.C. Summer plant in South Carolina aban- power is to increase without posing unacceptable risks to doned the project after it experienced significant cost over- public health, the environment, and international peace runs and delays. Only one project remains—two AP1000 and security. units at the Alvin W. Vogtle plant in Georgia—but its cost Despite renewed enthusiasm for nuclear power in many has doubled, and construction is taking more than twice quarters, its recent growth has been far slower than antici- as long as originally estimated. pated 10 years ago. No doubt, the March 2011 Fukushima Almost all nuclear power reactors operating and under Daiichi accident in Japan, which resulted in three reactor construction today are LWRs, so called because they use meltdowns and widespread radiological contamination of the ordinary water (H2O) to cool their hot, highly radioactive environment, has contributed to nuclear power’s stagnation. cores. Some observers believe that the LWR, the industry Even more significant has been the high cost of building new workhorse, has inherent flaws that are inhibiting nuclear reactors relative to other sources of electricity—primarily power’s growth. In addition to its high cost and long natural gas but also, increasingly, renewable energy sources construction time, critics point to—among other things— such as wind and solar. The current rate of construction of the LWR’s susceptibility to severe accidents (such as the new nuclear plants around the world barely outpaces the meltdowns at Fukushima), their inefficient use of uranium, retirements of operating plants that reach the ends of and the long-lived nuclear wastes they generate. their lifetimes or are no longer economic. In response, the US Department of Energy’s national In the United States, new nuclear plants have proven laboratories, universities, and numerous private vendors— prohibitively expensive and slow to build, discouraging from large established companies to small startups—are private investment and contributing to public skepticism. pursuing the development of reactors that differ funda- In the 2000s, amid industry hopes of a nuclear renaissance, mentally from LWRs. These non-light-water reactors “Advanced” Isn’t Always Better 1 (NLWRs) are cooled not by water but by other substances, such as liquid sodium, helium gas, or even molten salts.1 Given the urgency of the NLWRs are sometimes referred to as “advanced reac- climate crisis, rigorous tors.” However, that is a misnomer for most designs being pursued today, which largely descend from those proposed evaluation is needed to many decades ago.