Accelerator - Based Conversion of Weapons - Grade Plutonium

Nuclear confrontation between the United States and the former Soviet Union is less likely now that political tensions have eased and a large portion of their nuclear arsenals are being dismantled. However, negative ramifications of dismantlement have raised the specter of nuclear proliferation in a new and dangerous arena: nuclear terrorism. As a result of warhead dismantlement, stockpiles of weapons-grade plutonium (WGPu) and highlyenriched uranium (HEU), which form the heart of a nuclear weapon, are steadily increasing in both the U.S. and Russia. There is concern, particularly for the Russian inventories, that adequate controls and facilities are not in place to handle the expected levels of plutonium and the even larger amounts of uranium from dismantled weapons. Coupled with the pressures of a volatile political and economic environment, the lack of secure storage capacity increases the risk of nuclear materials being diverted into the hands of non-nuclear states and terrorist groups. Recognizing this danger, Russia has solicited financial assistance from the U.S. for the construction of a secure underground facility for interim storage of the WGPu and HEU. It is expected that a similar facility (or facilities) will be built in the United States. Plutonium disposition poses a particularly difficult problem. Unlike HEU, which can be mixed with natural uranium thus rendering it unusable for nuclear weapons and burned in existing commercial reactors, plutonium-fueled reactors are not well developed. Moreover, plutonium cannot be denatured; any mixture of plutonium can be made into a nuclear weapon. A variety of plutonium processing options have been proposed to render the WGPu more "proliferation resistant" for possible reuse in nuclear weapons, ranging from mixing WGPu with radioactive poisons to complete destruction through fissioning. However, a permanent plutonium disposal option has not been chosen by either country. This thesis evaluates the accelerator-based fission reactor concept (ABC) that has been proposed to completely eliminate the WGPu through fissioning. The ABC concept constitutes an alternative to current solid-fuel reactors, and is a recast of early liquid-fueled reactor concepts, with one exception: the ABC will operate subcritically by means of a powerful linear accelerator that injects an exogenous source of neutrons into the core to maintain constant power level. Based on the existing policy objectives of the U.S. and Russia, a general framework is developed to evaluate the ABC system as a plutonium disposition technology. In summary, this analysis shows that the ABC is a feasible concept, though its technical immaturity makes it less attractive than concepts that are based on near-term technologies. However, reactors with high plutonium consumption rates, such as the ABC, may become attractive, or even necessary, if the analysis is expanded beyond weapons-grade plutonium to include the larger stockpiles of reactor-grade plutonium. Thesis Supervisor: Dr. Marvin Miller Title: Senior Research Scientist, Department of Nuclear Engineering 0.1 Acknowledgements I have been blessed with several advisors and friends without whom this thesis would not have been realized. I would like to take this opportunity to recognize them: Dr. Marvin M. Miller, my thesis advisor, has offered guidance throughout this process from definition to final draft. His review and comment on the many iterations of this work have been invaluable. I am also grateful to Dr. Kevin Otto, my thesis reader, for reading and providing comments. I would like to thank Rulon Linford, Ed Arthur, T.J. Trapp, Harry Dewey, and the many others I met while at Los Alamos National Laboratory, for their cooperation in providing information and help as I studied the ABC concept. I am grateful to Dr. Douglas Henderson, of the University of Wisconsin at Madison, for his willingness to tutor me in the fundamentals of nuclear physics and design. He is a patient teacher and friend. I would especially like to thank Kristine Cornils, who, throughout this long and sometimes discouraging thesis process, has been a daily source of encouragement, understanding, humor, and love. You are wonderful, Kristine! In this same light, I am eternally grateful to my friend Mike Perrott, a fellow New Mexican and MIT graduate student, whose patience and support has provided stability through the rough waters of MIT. Friends are friends forever, if the Lord is the Lord them. Indeed, people like Kristine and Mike make these words come alive! Finally, I would like to thank my family my parents, Robert and Rafelita Taylor, and my brothers and sisters (all eleven of them!...and beyond) for their undying love and support. I could not have made it without you!