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For nearly eight decades, the world has been navigating the dangers of the nuclear age. Despite Cold War tensions and the rise of global terrorism, nuclear weapons have not been used in conflict since Hiroshima and Nagasaki in 1945. Efforts such as strategic deterrence, arms control and non-proliferation agreements, and the U.S.-led global counterterrorism have helped to keep nuclear incidents at bay. However, the nation's success to date in countering nuclear terrorism does not come with a guarantee, success often carries the risk that other challenges will siphon away attention and resources and can lead to the perception that the threat no longer exists. This report found that U.S. efforts to counter nuclear or radiological terrorism are not keeping pace with the evolving threat landscape. The U.S. government should maintain a strategic focus and effort on combatting terrorism across the national security community in coordination with international partners, State, Local, Tribal and Territorial authorities, the National Laboratories, universities and colleges, and civil society. Developing and sustaining adequate nuclear incident response and recovery capabilities at the local and state levels will likely require significant new investments in resources and empowerment of local response from Federal Emergency Management Agency (FEMA), working with the Centers for Disease Control and Prevention, Environmental Protection Agency, Department of Energy, and National Institutes of Health.

The United States and the world face serious threats to nuclear stability and peace, now and in the coming decades. Within the nuclear arena, U.S. policy makers will need to make strategic decisions related to nuclear risks to assist with long-term planning as well as responding in real time to unanticipated events. The occurrence of unanticipated nuclear events is expected to increase as more countries develop, expand, or field nuclear energy capability; more countries consider development of nuclear weapon capability and new nuclear weapon states emerge; and nuclear weapon states expand their nuclear arsenals. At the request of the Department of Defense, the National Academies of Sciences, Engineering, and Medicine established and managed the Committee on Risk Analysis Methods for Nuclear War and Nuclear Terrorism to explore U.S. government methods for assessing nuclear war and nuclear terrorism risks and how those assessments are used to develop strategy and policy. This publication is the unclassified Phase 2 version of the final classified report. Risk Analysis Methods for Nuclear War and Nuclear Terrorism: Phase II builds on an earlier Phase I unclassified report. This book expands upon the use of analytical methods to assess the risks of nuclear terrorism and nuclear war and the role such approaches may play in U.S. security strategy.

The assessment of risk is complex and often controversial. It is derived from the existence of a hazard, and it is characterized by the uncertainty of possible undesirable events and their outcomes. Few outcomes are as undesirable as nuclear war and nuclear terrorism. Over the decades, much has been written about particular situations, policies, and weapons that might affect the risks of nuclear war and nuclear terrorism. The nature of the concerns and the risk analysis methods used to evaluate them have evolved considerably over time. At the request of the Department of Defense, Risk Analysis Methods for Nuclear War and Nuclear Terrorism discusses risks, explores the risk assessment literature, highlights the strengths and weaknesses of risk assessment approaches, and discusses some publicly available assumptions that underpin U.S. security strategies, all in the context of nuclear war and nuclear terrorism.

High magnetic fields are a vital tool in many areas of science and technology that impact our everyday lives. Magnetic resonance imaging enables a wide range of medical diagnostics and research, while nuclear magnetic resonance is critical for drug discovery research and more. High magnetic fields are an essential component to many proposed fusion energy reactors and are necessary to push the boundaries towards the development of new quantum technologies and semiconductors. At the request of the National Science Foundation, the National Academies organized a study to identify scientific opportunities and key applications for high-magnetic-field science and technology for the next decade and beyond. This report explores the current state and future prospects for high-magnetic-field technologies and recommends actions to support the workforce, facilities, magnet development, and critical materials access necessary to promote U.S. innovation.

The Hanford Nuclear Reservation in the state of Washington produced about two-thirds of the nations plutonium for nuclear weapons from 1944 until the last reactor was shut down in 1987. The U.S. Department of Energy Office of Environmental Management (DOE-EM) manages the ongoing clean-up at Hanford and has built a plant to convert the high-level radioactive waste into a glass form (vitrification) for safe disposal. However, decisions remain about how best to treat and dispose of the low-level waste at Hanford, which comprises over 90% of the volume of waste. To inform its decision, DOE contracted with key Federally Funded Research and Development Centers (FFRDC), led by Savannah River National Laboratory, to carry out an analysis. This final in a trilogy of reports from the National Academies reviews the FFRDC third report released in January 2023. The review finds that the FFRDC team made a strong technical case that converting the supplemental low-level waste from the vitrification process to a grout form (like cement) is the best option in terms of cost-effectiveness and timeliness, and that off-site disposal of that grout is a valid option as it will be away from potable water. The FFRDC provided a useful framework to help decision-makers understand the issues and trade-offs of the disposal options and did an excellent job of isolating specific factual considerations that can be analyzed, often quantified, and compared with each other. The FFRDC chose to provide a purely technical analysis that excluded analysis of two important factors to be considered - securing regulatory permissions and public acceptance - treating them, for now, as uncertainties. Looking ahead, the DOE faces many uncertainties and should emphasize flexibility in its overall approach, allowing for multiple, redundant options and pathways, as well as the ability to change over time.

The Committee on Risk Analysis Methods for Nuclear War and Nuclear Terrorism was established and managed by the National Academies of Sciences, Medicine, and Engineering in response to a congressional mandate to independently explore U.S. government methods for assessing nuclear war and nuclear terrorism risks and how those assessments are used to develop strategy and policy. This publication is the public, abbreviated version of the classified report.

The world confronts an existential challenge in responding to climate change, resulting in an urgent need to reduce greenhouse gas emissions from all sectors of the economy. What will it take for new and advanced nuclear reactors to play a role in decarbonization? Nuclear power provides a significant portion of the worlds low-carbon electricity, and advanced nuclear technologies have the potential to be smaller, safer, less expensive to build, and better integrated with the modern grid. However, if the United States wants advanced nuclear reactors to play a role in its plans for decarbonization, there are many key challenges that must be overcome at the technical, economic, and regulatory levels. Laying the Foundation for New and Advanced Nuclear Reactors in the United States discusses how the United States could support the successful commercialization of advanced nuclear reactors with a set of near-term policies and practices. The recommendations of this report address the need to close technology research gaps, explore new business use cases, improve project management and construction, update regulations and security requirements, prioritize community engagement, strengthen the skilled workforce, and develop competitive financing options.

The United States has deployed commercial nuclear power since the 1950s, and as of 2021, nuclear power accounts for approximately 20 percent of U.S. electricity generation. The current commercial nuclear fleet consists entirely of thermal-spectrum, light water reactors operating with low-enriched uranium dioxide fuel in a once-through fuel cycle. In recent years, the U.S. Congress, U.S. Department of Energy, and private sector have expressed considerable interest in developing and deploying advanced nuclear reactors to augment, and possibly replace, the U.S. operating fleet of reactors, nearly all of which will reach the end of their currently licensed operating lives by 2050. Much of this interest stems from the potential ability of advanced reactors and their associated fuel cycles - as claimed by their designers and developers - to provide a number of advantages, such as improvements in economic competitiveness, reductions in environmental impact via better natural resource utilization and/or lower waste generation, and enhancements in nuclear safety and proliferation resistance. At the request of Congress, this report explores merits and viability of different nuclear fuel cycles, including fuel cycles that may use reprocessing, for both existing and advanced reactor technologies; and waste management (including transportation, storage, and disposal options) for advanced reactors, and in particular, the potential impact of advanced reactors and their fuel cycles on waste generation and disposal.

The Hanford Nuclear Reservation in Washington state, which produced plutonium for nuclear weapons from 1944-1987, is the site of the largest and most complex nuclear cleanup challenge in the United States. The U.S. Department of Energy's Office of Environmental Management (DOE-EM) is responsible for managing the cleanup of the radioactive and other hazardous wastes stored in 177 underground tanks at the site. DOE plans to use vitrification, or immobilization in glass waste forms, for all of the high-level radioactive waste at Hanford. However, because the volume of'low-activity waste'exceeds DOEs capacity limits for vitrification, DOE must decide how to treat the remaining'supplemental low-activity waste'(SLAW) so that it can be safely disposed in a near-surface disposal site. To help inform its decision, DOE contracted with a Federally Funded Research and Development Center (FFRDC), led by Savannah River National Laboratory, to analyze and report its findings about three potential alternative technologies. At the request of Congress, the National Academies reviewed the FFRDC report in terms of its value for decision making and how well it meets various Congressional requirements related to Hanford cleanup. The review concludes that the FFRDC report is overall very strong, provides a useful framework for evaluating the technology options, and is responsive to guidance from the first National Academies review. The framework provides for structured side-by-side comparisons, using relevant criteria, of a limited number of alternatives for managing SLAW. Recommendations for strengthening the report include estimating a lifecycle cost profile for constructing and operating each alternative, and providing more in-depth discussion on potential challenges that may need to be addressed in obtaining the necessary various regulatory approvals.

The U.S. Department of Energy's Office of Environmental Management (DOE-EM) was established by Congress in 1989 to remediate waste and environmental contamination that have resulted from nuclear weapons production and related activities. It has expended almost $200 billion on cleanup and related activities since its establishment and completed cleanup at all but 15 of the more than 100 sites. At the request of Congress, the National Academies of Sciences, Engineering, and Medicine formed a committee to provide advice on enhancing the effectiveness and efficiency of DOE-EM cleanup activities, particularly with respect to project management, contracting, and oversight practices. These recommendations were provided in two reports. The first report, Review of Effectiveness and Efficiency of Defense Environmental Cleanup Activities of DOE's Office of Environmental Management: Report 1, considered overall project management practices, project management metrics and outcomes, and contract structures and performance measures. This second report focuses on specific DOE-EM sites to assess how effective the management of the numerous projects at the sites is contributing to the wider programmatic objectives of DOE-EM.

Radiation exposure at low doses (below 100 milligray) or low-dose rates (less than 5 milligray per hour) occurs in a wide range of medical, industrial, military, and commercial settings. The effects of exposure at these levels are not fully understood, but there are long-standing concerns that such exposure could negatively affect human health. Although cancer has been linked to low-dose radiation exposure for decades, there is increasing evidence that low-dose radiation exposure may also be associated with cardiovascular disease, neurological disorders, immune dysfunction, and cataracts. Recent advances in research, new tools, and a coordinated multidisciplinary research program could help fill knowledge gaps about the health impacts of low-dose radiation exposures. This report calls for the development of a U.S. research program to study how low doses of radiation affect cancer, cardiovascular disease, neurological disorders, and other disease risks. Research should also better define the impacts of radiation doses, dose rates, types of radiation, and exposure duration. The report estimates $100 million annually for the next 15 years would be required to conduct epidemiological and biological research, and to establish an infrastructure for research.

Nuclear reactors can provide low-carbon energy, and advanced nuclear technologies could play an important role in moving the United States toward a zero-carbon future. Next-generation nuclear reactors have the potential to be smaller, safer, less expensive to build, and better integrated with the modern grid. However, the technical, economic, and regulatory outlook for these technologies remains uncertain. The Committee on Laying the Foundation for New and Advanced Nuclear Reactors in the United States was convened by the National Academies of Sciences, Engineering, and Medicine to identify opportunities and barriers to the commercialization of new and advanced nuclear reactor technologies in the United States over the next 30 years as part of a decarbonization strategy. To support its information gathering, the committee convened a workshop on September 1-3, 2021, titled Understanding the Societal Challenges Facing Nuclear Power. Speakers and participants from industry, government, and academia discussed the nature and extent of the societal challenges facing nuclear energy as well as lessons from past experiences in the nuclear industry, from analogous industries, and from the social sciences. This publication summarizes the presentations and discussion of the workshop.

The Hanford Nuclear Reservation, where about two-thirds of the nation's weapons plutonium was produced from 1944 to 1987, is the site of the largest and most complex nuclear cleanup challenge in the United States. Section 3125 of the National Defense Authorization Act for Fiscal Year 2021 calls for a Federally Funded Research and Development Center (FFRDC) to develop a framework of decisions to be made among the supplemental treatment technologies, waste forms, and disposal locations for low-activity waste in the Hanford tanks. In addition, Section 3125 calls for the National Academies of Sciences, Engineering, and Medicine to provide a concurrent, independent peer review of the ongoing FFRDC analysis. This review report, the first of three to address the Congressional mandate, focuses on the technical quality and completeness of the FFRDC's draft framework.

Astronauts face unique health-related risks during crewed space missions, and longer-duration missions that extend to greater distances in our solar system (including to the Moon and Mars) will likely increase those risks. Cancer risks due to ionizing radiation exposure are one of these health-related risks. Assessing, managing, and communicating radiation-induced cancer risks associated with spaceflight are challenging because of incomplete knowledge of the radiation environment in space, limited data on radiation-induced cellular damage mechanisms, lack of direct observations from epidemiological studies, and the complexities of understanding radiation risk. At the request of the National Aeronautics and Space Administration (NASA), an ad hoc committee of the National Academies of Sciences, Engineering, and Medicine convened to provide advice on NASA's proposed updates to their space radiation health standard, which sets the allowable limit of space radiation exposure throughout the course of an astronaut's career. Space Radiation and Astronaut Health: Managing and Communicating Cancer Risks provides the committee's recommendations and conclusions regarding the updated space radiation health standard, NASA's radiation risk communication strategies, and a process for developing an ethics-informed waiver protocol for long-duration spaceflight missions.

Radioactive Sources: Applications and Alternative Technologies assesses the status of medical, research, sterilization, and other commercial applications of radioactive sources and alternative (nonradioisotopic) technologies in the United States and internationally. Focusing on Category 1, 2, and 3 sources, this report reviews the current state of these sources by application and reviews the current state of existing technologies on the market or under development that are or could be used to replace radioisotopic technologies in those applications. Radioactive Sources will support existing and future activities under the National Nuclear Security Administration Office of Radiological Security program to reduce the use of high-risk radiological materials in commercial applications.

The U.S. Department of Energy (DOE) and its predecessor agencies have conducted activities to develop atomic energy for civilian and defense purposes since the initiation of the World War II Manhattan Project in 1942. These activities took place at large federal land reservations of hundreds of square miles involving industrial-scale operations, but also at many smaller federal and non-federal sites such as uranium mines, materials processing and manufacturing facilities. The nuclear weapons and energy production activities at these facilities produced large quantities of radioactive and hazardous wastes and resulted in widespread groundwater and soil contamination at these sites. DOE initiated a concerted effort to clean up these sites beginning in the 1980s. Many of these sites have been remediated and are in long-term caretaker status, closed or repurposed for other uses. Review of the Effectiveness and Efficiency of Defense Environmental Cleanup Activities of the Department of Energy's Office of Environmental Management: First Report provides background information on the sites currently assigned to the DOE's Office of Environmental Management that are undergoing cleanup; discusses current practices for management and oversight of the cleanups; offers findings and recommendations on such practices and how progress is measured against them; and considers the contracts under which the cleanups proceed and how these have been and can be structured to include incentives for improved cost and schedule performance.

Fusion energy offers the prospect of addressing the nation's energy needs and contributing to the transition to a low-carbon emission electrical generation infrastructure. Technology and research results from U.S. investments in the major fusion burning plasma experiment known as ITER, coupled with a strong foundation of research funded by the Department of Energy (DOE), position the United States to begin planning for its first fusion pilot plant. Strong interest from the private sector is an additional motivating factor, as the process of decarbonizing and modernizing the nation's electric infrastructure accelerates and companies seek to lead the way. At the request of DOE, Bringing Fusion to the U.S. Grid builds upon the work of the 2019 report Final Report of the Committee on a Strategic Plan for U.S. Burning Plasma Research to identify the key goals and innovations - independent of confinement concept - that are needed to support the development of a U.S. fusion pilot plant that can serve as a model for producing electricity at the lowest possible capital cost.

The U.S. Department of Energy's Office of Environmental Management is responsible for managing and cleaning up the waste and contamination at the Hanford Nuclear Reservation, the nation's biggest and most complex nuclear cleanup challenge. At the site, 177 underground tanks collectively contain about 211 million liters of waste that includes high-activity and low-activity materials. At the request of Congress, Final Review of the Study on Supplemental Treatment Approaches of Low-Activity Waste at the Hanford Nuclear Reservation: Review #4 focuses on approaches for treatment and disposal of the supplemental portion of the low-activity waste from the tanks. This review report discusses developments since the publication of Review #3 and provides a summary of public comments on the third committee review report. The authoring committee then shares their views on these comments and whether they change any of the findings or recommendations in the third review report.

In 2018, the National Academies of Sciences, Engineering, and Medicine issued an Interim Report evaluating the general viability of the U.S. Department of Energy's National Nuclear Security Administration's (DOE-NNSA's) conceptual plans for disposing of 34 metric tons (MT) of surplus plutonium in the Waste Isolation Pilot Plant (WIPP), a deep geologic repository near Carlsbad, New Mexico. It provided a preliminary assessment of the general viability of DOE-NNSA's conceptual plans, focused on some of the barriers to their implementation. This final report addresses the remaining issues and echoes the recommendations from the interim study.

The National Defense Authorization Act for fiscal year 2017 contained a request for a National Academies of Sciences, Engineering, and Medicine review and assessment of science and technology development efforts within the Department of Energy's Office of Environmental Management (DOE-EM). This technical report is the result of the review and presents findings and recommendations.

In 1943, as part of the Manhattan Project, the Hanford Nuclear Reservation was established with the mission to produce plutonium for nuclear weapons. During 45 years of operations, the Hanford Site produced about 67 metric tonnes of plutonium—approximately two-thirds of the nation's stockpile. Production processes generated radioactive and other hazardous wastes and resulted in airborne, surface, subsurface, and groundwater contamination. Presently, 177 underground tanks contain collectively about 210 million liters (about 56 million gallons) of waste. The chemically complex and diverse waste is difficult to manage and dispose of safely. Section 3134 of the National Defense Authorization Act for Fiscal Year 2017 calls for a Federally Funded Research and Development Center (FFRDC) to conduct an analysis of approaches for treating the portion of low-activity waste at the Hanford Nuclear Reservation intended for supplemental treatment. The third of four, this report provides an overall assessment of the FFRDC team's final draft report, dated April 5, 2019.

Accidents and terrorist attacks that lead to the release of radioactive materials can cause deaths, injuries, and a range of psychosocial effects in the surrounding community and team of emergency responders. In the United States, federal, state, and local agencies respond with the necessary resources to address the consequences of nuclear and radiological incidents and monitor the affected population. Following the 2011 Fukushima Daiichi Nuclear Power Plant accident and the 2017 Gotham Shield National Level Exercise, the CDC recognized an opportunity to improve their practices by establishing a more efficient and timely health effect surveillance system before another incident occurs. On March 12-13th, 2019, the National Academies convened a workshop to discuss the process for preparing a radiation registry for monitoring long-term health effects of populations affected by a nuclear or radiological incident. Participants assessed existing information, useful practices, and tools for planning a radiation registry that will enhance incident monitoring and response methods. This publication summarizes the discussions and presentations from the workshop.

Exposures at low doses of radiation, generally taken to mean doses below 100 millisieverts, are of primary interest for setting standards for protecting individuals against the adverse effects of ionizing radiation. However, there are considerable uncertainties associated with current best estimates of risks and gaps in knowledge on critical scientific issues that relate to low dose radiation. The Nuclear and Radiation Studies Board of the National Academies hosted the symposium on The Future of Low Dose Radiation Research in the United States on May 8 and 9, 2019. The goal of the symposium was to provide an open forum for a national discussion on the need for a long-term strategy to guide a low dose radiation research program in the United States. The symposium featured presentations on low dose radiation programs around the world, panel discussions with representatives from governmental and nongovernmental organizations about the need for a low dose radiation research program, reviews of low dose radiation research in epidemiology and radiation biology including new directions, and lessons to be learned from setting up large research programs in non-radiation research fields. This publication summarizes the presentation and discussion of the symposium.

One of the pathways by which the scientific community confirms the validity of a new scientific discovery is by repeating the research that produced it. When a scientific effort fails to independently confirm the computations or results of a previous study, some fear that it may be a symptom of a lack of rigor in science, while others argue that such an observed inconsistency can be an important precursor to new discovery. Concerns about reproducibility and replicability have been expressed in both scientific and popular media. As these concerns came to light, Congress requested that the National Academies of Sciences, Engineering, and Medicine conduct a study to assess the extent of issues related to reproducibility and replicability and to offer recommendations for improving rigor and transparency in scientific research. Reproducibility and Replicability in Science defines reproducibility and replicability and examines the factors that may lead to non-reproducibility and non-replicability in research. Unlike the typical expectation of reproducibility between two computations, expectations about replicability are more nuanced, and in some cases a lack of replicability can aid the process of scientific discovery. This report provides recommendations to researchers, academic institutions, journals, and funders on steps they can take to improve reproducibility and replicability in science.

In 1943, as part of the Manhattan Project, the Hanford Nuclear Reservation was established with the mission to produce plutonium for nuclear weapons. During 45 years of operations, the Hanford Site produced about 67 metric tonnes of plutonium—approximately two-thirds of the nation's stockpile. Production processes generated radioactive and other hazardous wastes and resulted in airborne, surface, subsurface, and groundwater contamination. Presently, 177 underground tanks contain collectively about 210 million liters (about 56 million gallons) of waste. The chemically complex and diverse waste is difficult to manage and dispose of safely. Section 3134 of the National Defense Authorization Act for Fiscal Year 2017 calls for a Federally Funded Research and Development Center (FFRDC) to conduct an analysis of approaches for treating the portion of low-activity waste (LAW) at the Hanford Nuclear Reservation intended for supplemental treatment. The first of four, this report reviews the analysis carried out by the FFRDC. It evaluates the technical quality and completeness of the methods used to conduct the risk, cost benefit, schedule, and regulatory compliance assessments and their implementations; waste conditioning and supplemental treatment approaches considered in the assessments; and other key information and data used in the assessments.

Disposal of Surplus Plutonium at the Waste Isolation Pilot Plant: Interim Report evaluates the general viability of the U.S. Department of Energy's National Nuclear Security Administration's (DOE-NNSA's) conceptual plans for disposing of 34 metric tons (MT) of surplus plutonium in the Waste Isolation Pilot Plant (WIPP), a deep geologic repository near Carlsbad, New Mexico. This report evaluates DOE-NNSA's plans to ship, receive, and emplace surplus plutonium in WIPP and its understanding of the impacts of these plans on WIPP and WIPP-bound waste streams. This report, the first of two to be issued during this study, provides a preliminary assessment of the general viability of DOE-NNSA's conceptual plans, focusing on some of the barriers to their implementation.

In 1943, as part of the Manhattan Project, the Hanford Nuclear Reservation was established with the mission to produce plutonium for nuclear weapons. During 45 years of operations, the Hanford Site produced about 67 metric tonnes of plutonium—approximately two-thirds of the nation's stockpile. Production processes generated radioactive and other hazardous wastes and resulted in airborne, surface, subsurface, and groundwater contamination. Presently, 177 underground tanks contain collectively about 210 million liters (about 56 million gallons) of waste. The chemically complex and diverse waste is difficult to manage and dispose of safely. Section 3134 of the National Defense Authorization Act for Fiscal Year 2017 calls for a Federally Funded Research and Development Center (FFRDC) to conduct an analysis of approaches for treating the portion of low-activity waste (LAW) at the Hanford Nuclear Reservation intended for supplemental treatment. The second of four, this report reviews the results of the assessments, including the formulation and presentation of conclusions and the characterization and treatment of uncertainties.

Participants of the July 17-18, 2017, symposium titled Opportunities and Approaches for Supplying Molybdenum-99 and Associated Medical Isotopes to Global Markets examined current trends in molybdenum-99 production, prospects for new global supplies, and technical, economic, regulatory, and other considerations for supplying molybdenum-99 to global markets. This publication summarizes the presentations and discussions from the symposium.

Most countries in the world use the SI (Système International, also known as the metric system) units for radiation measurements in commercial and technical activities. The United States, in contrast, uses a mix of SI and conventional units for radiation measurements, despite 30-year-old national and international recommendations to exclusively use SI. Radiation professionals in the United States are faced with the need to understand both systems and make conversions between the two. In September 2016, the National Academies of Sciences, Engineering, and Medicine organized a workshop to explore potential communication improvements associated with adopting the international system of units (SI units) for radiation measurements in the United States. Participants discussed potential improvements in the effectiveness of responding to national and international radiation emergencies, international experiences in adopting the exclusive use of SI units of radiation measurements, and steps needed to adopt the exclusive use of SI units in the US in terms of timing, implementation, and ways to overcome or manage technical, economic, and policy barriers. This publication summarizes the presentations and discussions from the workshop.

The Department of Energy's Office of Environmental Management (DOE) is responsible for the safe cleanup of sites used for nuclear weapons development and government-sponsored nuclear energy research. Low-level radioactive waste (LLW) is the most volumetrically significant waste stream generated by the DOE cleanup program. LLW is also generated through commercial activities such as nuclear power plant operations and medical treatments. The laws and regulations related to the disposal of LLW in the United States have evolved over time and across agencies and states, resulting in a complex regulatory structure. DOE asked the National Academies of Sciences, Engineering, and Medicine to organize a workshop to discuss approaches for the management and disposition of LLW. Participants explored the key physical, chemical, and radiological characteristics of low-level waste that govern its safe and secure management and disposal in aggregate and in individual waste streams, and how key characteristics of low level waste are incorporated into standards, orders, and regulations that govern the management and disposal of LLW in the United States and in other major waste-producing countries. This publication summarizes the presentations and discussions from the workshop.

The continued presence of highly enriched uranium (HEU) in civilian installations such as research reactors poses a threat to national and international security. Minimization, and ultimately elimination, of HEU in civilian research reactors worldwide has been a goal of U.S. policy and programs since 1978. Today, 74 civilian research reactors around the world, including 8 in the United States, use or are planning to use HEU fuel. Since the last National Academies of Sciences, Engineering, and Medicine report on this topic in 2009, 28 reactors have been either shut down or converted from HEU to low enriched uranium fuel. Despite this progress, the large number of remaining HEU-fueled reactors demonstrates that an HEU minimization program continues to be needed on a worldwide scale. Reducing the Use of Highly Enriched Uranium in Civilian Research Reactors assesses the status of and progress toward eliminating the worldwide use of HEU fuel in civilian research and test reactors.

The U.S. Congress asked the National Academy of Sciences to conduct a technical study on lessons learned from the Fukushima Daiichi nuclear accident for improving safety and security of commercial nuclear power plants in the United States. This study was carried out in two phases: Phase 1, issued in 2014, focused on the causes of the Fukushima Daiichi accident and safety-related lessons learned for improving nuclear plant systems, operations, and regulations exclusive of spent fuel storage. This Phase 2 report focuses on three issues: (1) lessons learned from the accident for nuclear plant security, (2) lessons learned for spent fuel storage, and (3) reevaluation of conclusions from previous Academies studies on spent fuel storage.

Passenger screening at commercial airports in the United States has gone through significant changes since the events of September 11, 2001. In response to increased concern over terrorist attacks on aircrafts, the Transportation Security Administration (TSA) has deployed security systems of advanced imaging technology (AIT) to screen passengers at airports. To date (December 2014), TSA has deployed AITs in U.S. airports of two different technologies that use different types of radiation to detect threats: millimeter wave and X-ray backscatter AIT systems. X-ray backscatter AITs were deployed in U.S. airports in 2008 and subsequently removed from all airports by June 2013 due to privacy concerns. TSA is looking to deploy a second-generation X-ray backscatter AIT equipped with privacy software to eliminate production of an image of the person being screened in order to alleviate these concerns. This report reviews previous studies as well as current processes used by the Department of Homeland Security and equipment manufacturers to estimate radiation exposures resulting from backscatter X-ray advanced imaging technology system use in screening air travelers. Airport Passenger Screening Using Backscatter X-Ray Machines examines whether exposures comply with applicable health and safety standards for public and occupational exposures to ionizing radiation and whether system design, operating procedures, and maintenance procedures are appropriate to prevent over exposures of travelers and operators to ionizing radiation. This study aims to address concerns about exposure to radiation from X-ray backscatter AITs raised by Congress, individuals within the scientific community, and others.

The Science of Responding to a Nuclear Reactor Accident summarizes the presentations and discussions of the May 2014 Gilbert W. Beebe Symposium titled'The Science and Response to a Nuclear Reactor Accident'. The symposium, dedicated in honor of the distinguished National Cancer Institute radiation epidemiologist who died in 2003, was co-hosted by the Nuclear and Radiation Studies Board of the National Academy of Sciences and the National Cancer Institute. The symposium topic was prompted by the March 2011 accident at the Fukushima Daiichi nuclear power plant that was initiated by the 9.0-magnitude earthquake and tsunami off the northeast coast of Japan. This was the fourth major nuclear accident that has occurred since the beginning of the nuclear age some 60 years ago. The 1957 Windscale accident in the United Kingdom caused by a fire in the reactor, the 1979 Three Mile Island accident in the United States caused by mechanical and human errors, and the 1986 Chernobyl accident in the former Soviet Union caused by a series of human errors during the conduct of a reactor experiment are the other three major accidents. The rarity of nuclear accidents and the limited amount of existing experiences that have been assembled over the decades heightens the importance of learning from the past. This year's symposium promoted discussions among federal, state, academic, research institute, and news media representatives on current scientific knowledge and response plans for nuclear reactor accidents. The Beebe symposium explored how experiences from past nuclear plant accidents can be used to mitigate the consequences of future accidents, if they occur. The Science of Responding to a Nuclear Reactor Accident addresses off-site emergency response and long-term management of the accident consequences; estimating radiation exposures of affected populations; health effects and population monitoring; other radiological consequences; and communication among plant officials, government officials, and the public and the role of the media.

It is probably only a matter of time before we witness the next event in which large numbers of people are exposed to ionizing radiation. In the past, planning a response to such an occurrence would have likely focused on the management of casualties from high-dose exposure. However, more recently, a different threat has come to the fore: accidental (through a containment breach in a nuclear power plant, for example) or intentional (via a'dirty bomb') releases of radioactivity resulting in low-dose exposure to a population. The magnitude of the health risks arising from low-dose radiation exposure is uncertain, and this uncertainty has significant economic implications for public health decision making. Research on Health Effects of Low-Level Ionizing Radiation Exposure examines recent scientific knowledge about the human effects of exposure to low-dose radiation from medical, occupational, and environmental ionizing-radiation sources. This report is intended to provide advice to the Armed Forces Radiobiology Research Institute (AFRRI) about its role in low-dose radiation health effects research. The report identifies current research directions in radiobiological science and assesses how AFRRI programs are advancing research along these directions. The recommendations of Research on Health Effects of Low-Level Ionizing Radiation Exposure will provide guidance for AFRRI to build on its strengths and advance its mission while contributing to the body of scientific knowledge on the health effects of exposure to low-dose ionizing radiation.

The March 11, 2011, Great East Japan Earthquake and tsunami sparked a humanitarian disaster in northeastern Japan. They were responsible for more than 15,900 deaths and 2,600 missing persons as well as physical infrastructure damages exceeding $200 billion. The earthquake and tsunami also initiated a severe nuclear accident at the Fukushima Daiichi Nuclear Power Station. Three of the six reactors at the plant sustained severe core damage and released hydrogen and radioactive materials. Explosion of the released hydrogen damaged three reactor buildings and impeded onsite emergency response efforts. The accident prompted widespread evacuations of local populations, large economic losses, and the eventual shutdown of all nuclear power plants in Japan. Lessons Learned from the Fukushima Nuclear Accident for Improving Safety and Security of U.S. Nuclear Plants is a study of the Fukushima Daiichi accident. This report examines the causes of the crisis, the performance of safety systems at the plant, and the responses of its operators following the earthquake and tsunami. The report then considers the lessons that can be learned and their implications for U.S. safety and storage of spent nuclear fuel and high-level waste, commercial nuclear reactor safety and security regulations, and design improvements. Lessons Learned makes recommendations to improve plant systems, resources, and operator training to enable effective ad hoc responses to severe accidents. This report's recommendations to incorporate modern risk concepts into safety regulations and improve the nuclear safety culture will help the industry prepare for events that could challenge the design of plant structures and lead to a loss of critical safety functions. In providing a broad-scope, high-level examination of the accident, Lessons Learned is meant to complement earlier evaluations by industry and regulators. This in-depth review will be an essential resource for the nuclear power industry, policy makers, and anyone interested in the state of U.S. preparedness and response in the face of crisis situations.

The Department of Energy's Office of Environmental Management's (EM) mission is the safe cleanup of sites associated with the government-led development of nuclear weapons and nuclear energy. While many of these legacy sites have completed cleanup, the largest and most complex sites have not been fully remediated. The cleanup of these sites is proceeding under legally enforceable agreements with timelines for hundreds of milestones. EM is reviewing alternative approaches to increase effectiveness and improve cost efficiencies of its cleanup activities, especially for sites that will have residual contamination when active cleanup is complete. This report is the summary of two workshops convened in October 2013 and January 2014 on best practices for risk-informed remedy selection, closure, and post-closure control of radioactive and chemically contaminated sites that present significant difficulty for remediation to unrestricted release. The workshop series aimed to explore best practices that promote effective, risk-informed decision making and future opportunities to improve remediation approaches and practices.In the Workshop #1 section of Best Practices for Risk-Informed Decision Making Regarding Contaminated Sites, the report examines holistic approaches for remediating sites with multiple contaminant sources and post-closure uses, and approaches for incorporating a sustainability framework into decision making regarding site remediation, closure, and post-closure control. In Workshop #2, the report focuses on post-closure controls, assessment of long-term performance of site remedies, and best practices for risk-based remediation decisions.

The material that sustains the nuclear reactions that produce energy can also be used to make nuclear weapons—and therefore, the development of nuclear energy is one of multiple pathways to proliferation for a non-nuclear weapon state. There is a tension between the development of future nuclear fuel cycles and managing the risk of proliferation as the number of existing and future nuclear energy systems expands throughout the world. As the Department of Energy (DOE) and other parts of the government make decisions about future nuclear fuel cycles, DOE would like to improve proliferation assessments to better inform those decisions. Improving the Assessment of the Proliferation Risk of Nuclear Fuel Cycles considers how the current methods of quantification of proliferation risk are being used and implemented, how other approaches to risk assessment can contribute to improving the utility of assessments for policy and decision makers. The study also seeks to understand the extent to which technical analysis of proliferation risk could be improved for policy makers through research and development.

The Global Nuclear Detection Architecture (GNDA) is described as a worldwide network of sensors, telecommunications, and personnel, with the supporting information exchanges, programs, and protocols that serve to detect, analyze, and report on nuclear and radiological materials that are out of regulatory control. The Domestic Nuclear Detection Office (DNDO), an office within the Department of Homeland Security (DHS), coordinates the development of the GNDA with its federal partners. Performance Metrics for the Global Nuclear Detection Architecture considers how to develop performance measures and quantitative metrics that can be used to evaluate the overall effectiveness and report on progress toward meeting the goals of the GNDA. According to this report, two critical components are needed to evaluate the effectiveness of the GNDA: a new strategic plan with outcome-based metrics and an analysis framework to enable assessment of outcome-based metrics. The GNDA is a complex system of systems meant to deter and detect attempts to unlawfully transport radiological or nuclear material. The recommendations of Performance Metrics for the Performance Metrics for the Global Nuclear Detection Architecture may be used to improve the GNDA strategic plan and the reporting of progress toward meeting its goals during subsequent review cycles.

In the late 1980s, the National Cancer Institute initiated an investigation of cancer risks in populations near 52 commercial nuclear power plants and 10 Department of Energy nuclear facilities (including research and nuclear weapons production facilities and one reprocessing plant) in the United States. The results of the NCI investigation were used a primary resource for communicating with the public about the cancer risks near the nuclear facilities. However, this study is now over 20 years old. The U.S. Nuclear Regulatory Commission requested that the National Academy of Sciences provide an updated assessment of cancer risks in populations near USNRC-licensed nuclear facilities that utilize or process uranium for the production of electricity. Analysis of Cancer Risks in Populations near Nuclear Facilities: Phase 1 focuses on identifying scientifically sound approaches for carrying out an assessment of cancer risks associated with living near a nuclear facility, judgments about the strengths and weaknesses of various statistical power, ability to assess potential confounding factors, possible biases, and required effort. The results from this Phase 1 study will be used to inform the design of cancer risk assessment, which will be carried out in Phase 2. This report is beneficial for the general public, communities near nuclear facilities, stakeholders, healthcare providers, policy makers, state and local officials, community leaders, and the media.

The growing use of medical diagnostic procedures is correlated with tremendous and undeniable benefits in the care of most patients. However, it is accompanied by growing concerns about the risks associated with diagnostic computed tomography and other procedures that utilize ionizing radiation. A number of initiatives in radiation safety in medicine have taken place in the United States and internationally, each serving different purposes. Their ultimate goals are to provide higher quality clinical management of the patient and to ensure that reasonable steps are taken to keep the exposures as low as possible without compromising diagnostic efficacy. Tracking Radiation Exposure from Medical Diagnostic Procedures: Workshop Reports provides a summary of the presentations and discussions that took place during the December 8-9, 2011, workshop titled'Tracking Radiation Exposure from Medical Diagnostic Procedures.'This workshop was organized by the Nuclear and Radiation Studies Board of the National Academy of Sciences and sponsored by the Centers for Disease Control and Prevention, the U.S. Food and Drug Administration, and the U.S. Department of Health and Human Services. This workshop report was authored by a six-member committee of experts appointed by the National Academy of Sciences. This committee brought together public health regulators, physicians, manufacturers, researchers, and patients to explore'why,''what,'and'how'to track exposure from medical diagnostic procedures and possible next steps.

The growing use of nuclear medicine, the potential expansion of nuclear power generation, and the urgent needs to protect the nation against external nuclear threats, to maintain our nuclear weapons stockpile, and to manage the nuclear wastes generated in past decades, require a substantial, highly trained, and exceptionally talented workforce. Assuring a Future U.S.-Based Nuclear and Radiochemistry Expertise examines supply and demand for expertise in nuclear chemistry nuclear science, and radiochemistry in the United States and presents possible approaches for ensuring adequate availability of these skills, including necessary science and technology training platforms. Considering a range of reasonable scenarios looking to the future, none of these areas are likely to experience a decrease in demand for expertise. However, many in the current workforce are approaching retirement age and the number of students opting for careers in nuclear and radiochemistry has decreased dramatically over the past few decades. In order to avoid a gap in these critical areas, increases in student interest in these careers, in the research and educational capacity of universities and colleges, and sector specific on-the-job training will be needed. Concise recommendations are given for actions to avoid a shortage of nuclear chemistry, nuclear scientists, and radiochemists in the future.

Highly enriched uranium (HEU) is used for two major civilian purposes: as fuel for research reactors and as targets for medical isotope production. This material can be dangerous in the wrong hands. Stolen or diverted HEU can be used-in conjunction with some knowledge of physics-to build nuclear explosive devices. Thus, the continued civilian use of HEU is of concern particularly because this material may not be uniformly well-protected. To address these concerns, the National Research Council (NRC) of the U.S. National Academies and the Russian Academy of Sciences (RAS) held a joint symposium on June 8-10, 2011. Progress, Challenges, and Opportunities for Converting U.S. and Russian Research Reactors summarizes the proceedings of this joint symposium. This report addresses: (1) recent progress on conversion of research reactors, with a focus on U.S.- and R.F.-origin reactors; (2) lessons learned for overcoming conversion challenges, increasing the effectiveness of research reactor use, and enabling new reactor missions; (3) future research reactor conversion plans, challenges, and opportunities; and (4) actions that could be taken by U.S. and Russian organizations to promote conversion. The agenda for the symposium is provided in Appendix A, biographical sketches of the committee members are provided in Appendix B, and the report concludes with the statement of task in Appendix C.

A nuclear weapon or a significant quantity of special nuclear material (SNM) would be of great value to a terrorist or other adversary. It might have particular value if acquired from a U.S. facility—in addition to acquiring a highly destructive tool, the adversary would demonstrate an inability of the United States to protect its nuclear assets. The United States expends considerable resources toward maintaining effective security at facilities that house its nuclear assets. However, particularly in a budget-constrained environment, it is essential that these assets are also secured efficiently, meaning at reasonable cost and imposing minimal burdens on the primary missions of the organizations that operate U.S. nuclear facilities. It is in this context that the U.S. Congress directed the National Nuclear Security Administration (NNSA)—a semi-autonomous agency in the U.S. Department of Energy (DOE) responsible for securing nuclear weapons and significant quantities of SNM—asked the National Academies for advice on augmenting its security approach, particularly on the applicability of quantitative and other risk-based approaches for securing its facilities. In carrying out its charge, the committee has focused on what actions NNSA could take to make its security approach more effective and efficient. The committee concluded that the solution to balancing cost, security, and operations at facilities in the nuclear weapons complex is not to assess security risks more quantitatively or more precisely. This is primarily because there is no comprehensive analytical basis for defining the attack strategies that a malicious, creative, and deliberate adversary might employ or the probabilities associated with them. However, using structured thinking processes and techniques to characterize security risk could improve NNSA's understanding of security vulnerabilities and guide more effective resource allocation.

The Department of Energy's Office of Environmental Management (DOE-EM) is responsible for cleaning up radioactive waste and environmental contamination resulting from five decades of nuclear weapons production and testing. A major focus of this program involves the retrieval, processing, and immobilization of waste into stable, solid waste forms for disposal. Waste Forms Technology and Performance, a report requested by DOE-EM, examines requirements for waste form technology and performance in the cleanup program. The report provides information to DOE-EM to support improvements in methods for processing waste and selecting and fabricating waste forms. Waste Forms Technology and Performance places particular emphasis on processing technologies for high-level radioactive waste, DOE's most expensive and arguably most difficult cleanup challenge. The report's key messages are presented in ten findings and one recommendation.

This letter is the abbreviated version of an update of the interim report on testing, evaluation, costs, and benefits of advanced spectroscopic portals (ASPs), issued by the National Academies'Committee on Advanced Spectroscopic Portals in June 2009 (NRC 2009). This letter incorporates findings of the committee since that report was written, and it sharpens and clarifies the messages of the interim report based on subsequent committee investigations of more recent work by the Domestic Nuclear Detection Office (DNDO). The key messages in this letter, which is the final report from the committee, are stated briefly in the synopsis on the next page and described more fully in the sections that follow. The committee provides the context for this letter, and then gives advice on: testing, evaluation, assessing costs and benefits, and deployment of advanced spectroscopic portals. The letter closes with a reiteration of the key points. The letter is abbreviated in that a small amount of information that may not be released publicly for security or law-enforcement reasons has been redacted from the version delivered to you in October 2010, but the findings and recommendations remain intact.

The worldwide expansion of nuclear energy has been accompanied by concerns about nuclear weapons proliferation. If sited in states that do not possess nuclear weapons technology, some civilian nuclear technologies could provide a route for states or other organizations to acquire nuclear weapons. Metrics for assessing the resistance of a nuclear technology to diversion for non-peaceful uses-proliferation resistance-have been developed, but at present there is no clear consensus on whether and how these metrics are useful to policy decision makers. In 2011, the U.S. Department of Energy asked the National Academies to convene a public workshop addressing the capability of current and potential methodologies for assessing host state proliferation risk and resistance to meet the needs of decision makers. Proliferation Risk in Nuclear Fuel Cycles is a summary of presentations and discussions that transpired at the workshop-held on August 1-2, 2011-prepared by a designated rapporteur following the workshop. It does not provide findings and recommendations or represent a consensus reached by the symposium participants or the workshop planning committee. However, several themes emerged through the workshop: nonproliferation and new technologies, separate policy and technical cultures, value of proliferation resistance analysis, usefulness of social science approaches. The workshop was organized as part of a larger project undertaken by the NRC, the next phase of which (following the workshop) will be a consensus study on improving the assessment of proliferation risks associated with nuclear fuel cycles. This study will culminate in a report prepared by a committee of experts with expertise in risk assessment and communication, proliferation metrics and research, nuclear fuel cycle facility design and engineering, international nuclear nonproliferation and national security policy, and nuclear weapons design. This report is planned for completion in the spring of 2013.

The Department of Energy's Office of Environmental Management is developing a technology roadmap to guide planning and possible future congressional appropriations for its technology development programs. It asked the National Research Council of the National Academies to provide technical and strategic advice to support the development and implementation of this roadmap, specifically by undertaking a study that identifies principal science and technology gaps and their priorities for the cleanup program based on previous National Academies reports, updated and extended to reflect current site conditions and EM priorities and input form key external groups, such as the Nuclear Regulatory Commission, Defense Nuclear Facilities Safety Board, Environmental Protection Agency, and state regulatory agencies. In response, this book provides a high-level synthesis of principal science and technology gaps identified in previous NRC reports in part 1. Part 2 summarizes a workshop meant to bring together the key external groups to discuss current site conditions and science and technology needs.

Beginning with the Manhattan Project and continuing through the Cold War, the United States government constructed and operated a massive industrial complex to produce and test nuclear weapons and related technologies. When the Cold War ended, most of this complex was shut down permanently or placed on standby, and the United States government began a costly, long-term effort to clean up the materials, wastes, and environmental contamination resulting from its nuclear materials production. In 1989, Congress created the Office of Environmental Management (EM) within the Department of Energy (DOE) to manage this cleanup effort. Although EM has already made substantial progress, the scope of EM's future cleanup work is enormous. Advice on the Department of Energy's Cleanup Technology Roadmap: Gaps and Bridges provides advice to support the development of a cleanup technology roadmap for EM. The book identifies existing technology gaps and their priorities, strategic opportunities to leverage needed research and development programs with other organizations, needed core capabilities, and infrastructure at national laboratories and EM sites that should be maintained, all of which are necessary to accomplish EM's mission.

The so-called nuclear renaissance has increased worldwide interest in nuclear power. This potential growth also has increased, in some quarters, concern that nonproliferation considerations are not being given sufficient attention. In particular, since introduction of many new power reactors will lead to requiring increased uranium enrichment services to provide the reactor fuel, the proliferation risk of adding enrichment facilities in countries that do not have them now led to proposals to provide the needed fuel without requiring indigenous enrichment facilities. Similar concerns exist for reprocessing facilities. Internationalization of the Nuclear Fuel Cycle summarizes key issues and analyses of the topic, offers some criteria for evaluating options, and makes findings and recommendations to help the United States, the Russian Federation, and the international community reduce proliferation and other risks, as nuclear power is used more widely. This book is intended for all those who are concerned about the need for assuring fuel for new reactors and at the same time limiting the spread of nuclear weapons. This audience includes the United States and Russia, other nations that currently supply nuclear material and technology, many other countries contemplating starting or growing nuclear power programs, and the international organizations that support the safe, secure functioning of the international nuclear fuel cycle, most prominently the International Atomic Energy Agency.