As the 21st century unfolds, energy has become a theme underlying many of the challenges facing mankind. There is little doubt that standard of living closely correlates with the availability of energy resources. Raising the global standard of living will require providing power to those who cur­rently do not have it. It is estimated that two billion people do not have access to electricity.[1] This represents 30% of the world population. Providing power to these people, while continuing to satisfy the needs of the developed world, represents an enormous challenge, especially in the face of the threat of global climate change and decreasing availability of “clean” fossil fuels. Fission-based nuclear power will play a vital role in meeting this challenge. Nuclear power provides reliable base-load power with virtually no greenhouse gas emissions (other than those associated with mining and construction operations). This power production technol­ogy is well established and has proven to be safe and reliable, although it will be essential to maintain the improvements that have been made in plant operational safety and efficiency over the past several decades. One aspect of nuclear power that still provides significant technical challenges is the management of irradiated nuclear fuel.

For the most part, the United States has pursued a “once through” fuel cycle policy in which the uranium passes once through the power reactor and the irradiated fuel is emplaced intact in a geologic repository. However, no geologic repository has been licensed and this policy is presently being re-evaluated. At present, the fate of irradiated fuel from commercial power production reactors in the US is uncertain. Partial recycling of the irradiated fuel has been practiced in a number of countries (e. g., France, the United Kingdom, Russia, and Japan). These operations allow recycling of fissile uranium and plutonium back into the fuel cycle as mixed oxide (MOx) fuel, but they still result in problematic long-lived transuranic elements in the high-level waste that must be disposed of in a repository. The presence of the transuranic elements in waste placed in a repository requires engineer­ing of the repository to ensure safe performance for hundreds of thousands of years. Ensuring repository performance over such a large span of time is beyond human experience. Because of this, there has been growing inter­est in closing the nuclear fuel cycle in a manner that allows long-lived radionuclides to be recycled back into the fuel cycle and thus to have little effect on repository design or performance. Under such scenarios, the integ­rity of the repository need only be ensured for hundreds of years, a time frame well within the horizon of recorded history.

The subject matter of this book is the separation science and technology underpinning the efforts to manage irradiated nuclear fuel, including an examination of progress towards achieving a closed fuel cycle. The book is organized into three parts. The first part is aimed at providing fundamental scientific and engineering information related to nuclear fuel cycle separa­tions. The second part is devoted to describing standard and advanced technological solutions for application in nuclear fuel cycle separations. The third part reviews emerging and innovative separation and extraction tech­niques that are being pursued in the development of advanced nuclear fuel cycles.

Part I opens with two chapters summarizing fundamental actinide chem­istry as it relates to the separation of these elements and also their behavior in the environment, and the physical and chemical properties of actinides in particular, i. e. the most critical type of element of concern in nuclear fuel reprocessing. This is followed by a chapter describing the nuclear engineer­ing principles as they relate to aqueous separations. Chapters 4 and 5 discuss issues related to monitoring material flow through nuclear separation plants both for the purpose of process monitoring and control, and for safeguard­ing of special nuclear materials.

Part II of the book begins with Chapter 6 describing well-established technology for separating uranium and plutonium from dissolved irradiated fuel (i. e., the PUREX process). This chapter not only discusses the estab­lished PUREX methods, but also describes recent enhancements such as the recovery of a mixed uranium/plutonium product (the COEXTM process) and options for managing neptunium. This is followed by a chapter describ­ing the recent work performed in the US on advanced alternatives to the PUREX process. Chapter 8 describes recent developments in the separa­tion of fission products such as 137Cs and 90Sr from the dissolved irradiated fuel matrix. Taking this a step further, Chapter 9 discusses efforts to develop a single process that can extract and separate a number of radionuclides (actinides and fission products) together.

Part III of the book opens with Chapter 10 describing pyrochemical/ electrochemical separations and engineering. Chapter 11 details the quest to design new separation materials that are highly specific for selected fuel components, coverage that is enhanced by Chapter 12, which reviews developments in the partitioning and transmutation of radioactive wastes.

The development of such highly selective separations media would greatly simplify implementation of the separations required for closing the fuel cycle. Finally, the book closes with three chapters that discuss separation methods that are somewhat different from the traditional liquid-liquid extraction methods. Firstly, Chapter 13 discusses the possibility of using solid-phase extraction methods in nuclear fuel separations; secondly, Chapter 14 explores the use of supercritical fluid extraction and ionic liquids in advanced fuel cycle separations; and thirdly, Chapter 15 details biological treatment and bioremediation processes of use in separations science and for the recovery of useful materials from radioactive wastes.

It is our hope that this book will provide a useful reference to scientists and engineers working in the field of nuclear fuel cycle separations. But perhaps more importantly, we hope that it will provide a starting point for the young scientists and engineers who will rise to meet the challenge of safely managing the nuclear fuel cycle in a sustainable manner, enabling safe expansion of this low-carbon means of electrical production to raise mankind’s standard of living worldwide in the 21st century.

Finally, the editors and publisher would like to make a special dedication to Dr Troy Tranter, formerly of Idaho National Laboratory, USA, and author of Chapter 13 of this book, who sadly passed away in December 2010.

Reference

1. Rhodes, R.; Beller, D. The Need for Nuclear Power, Foreign Affairs, 2000, 79,

30-44.

Gregg J. Lumetta

Pacific Northwest National Laboratory P. O. Box 999, MSIN P7-22 Richland, WA 99352 USA

gregg. lumetta@pnl. gov (email)

Kenneth L. Nash

Washington State University P. O. Box 644630 Pullman, WA 99164-4630 USA

knash@wsu. edu (email)