Scientific And Technical Basis For The Geological Disposal Of Radioactive Wastes

This report focuses on the different functions of a repository within its life cycle and describes the processes relevant to the containment of long lived radioactive waste and other criteria influencing the long term integrity of the repository. It emphasizes the central role of safety and the importance of safety/performance assessments in the decision making process during repository development.

The disposal of radioactive waste is a central issue in the future of nuclear power and poses considerable technical, political and social issues. This book addresses these topics in an integrated fashion using performance assessment of the disposal concept as a unifying theme. Subjects addressed include: regulatory criteria; waste types, sources and characteristics; man-made or "engineered" barriers; the selection and evaluation of geological disposal media; the use of underground research laboratories; the movement of radionuclides in the biosphere; repository performance assessment tools and approaches; addressing uncertainty and spatial variability; assessing information from natural systems; and looking at radioactive waste in relation to other wastes. The book provides an up-to-date picture of radioactive waste disposal issues and will be of interest to scientists, engineers and consultants working in the nuclear industry and the environmental field.

Many countries are currently exploring the option to dispose of highly radioactive solid wastes deep underground in purpose built, engineered repositories. A number of surface and shallow repositories for less radioactive wastes are already in operation. One of the challenges facing the nuclear industry is to demonstrate confidently that a repository will contain wastes for so long that any releases that might take place in the future will pose no significant health or environmental risk. One method for building confidence in the long-term future safety of a repository is to look at the physical and chemical processes which operate in natural and archaeological systems, and to draw appropriate parallels with the repository. For example, to understand why some uranium orebodies have remained isolated underground for billions of years. Such studies are called 'natural analogues'. This book investigates the concept of geological disposal and examines the wide range of natural analogues which have been studied. Lessons learnt from studies of archaeological and natural systems can be used to improve our capabilities for assessing the future safety of a radioactive waste repository.

Focused attention by world leaders is needed to address the substantial challenges posed by disposal of spent nuclear fuel from reactors and high-level radioactive waste from processing such fuel. The biggest challenges in achieving safe and secure storage and permanent waste disposal are societal, although technical challenges remain. Disposition of radioactive wastes in a deep geological repository is a sound approach as long as it progresses through a stepwise decision-making process that takes advantage of technical advances, public participation, and international cooperation. Written for concerned citizens as well as policymakers, this book was sponsored by the U.S. Department of Energy, U.S. Nuclear Regulatory Commission, and waste management organizations in eight other countries.

During the next several years, decisions are expected to be made in several countries on the further development and implementation of the geological disposition option. The Board on Radioactive Waste Management (BRWM) of the U.S. National Academies believes that informed and reasoned discussion of relevant scientific, engineering and social issues can-and should-play a constructive role in the decision process by providing information to decision makers on relevant technical and policy issues. A BRWM-initiated project including a workshop at Irvine, California on November 4-5, 1999, and subsequent National Academies' report to be published in spring, 2000, are intended to provide such information to national policy makers both in the U.S. and abroad. To inform national policies, it is essential that experts from the physical, geological, and engineering sciences, and experts from the policy and social science communities work together. Some national programs have involved social science and policy experts from the beginning, while other programs have only recently recognized the importance of this collaboration. An important goal of the November workshop is to facilitate dialogue between these communities, as well as to encourage the sharing of experiences from many national programs. The workshop steering committee has prepared this discussion for participants at the workshop. It should elicit critical comments and help identify topics requiring in-depth discussion at the workshop. It is not intended as a statement of findings, conclusions, or recommendations. It is rather intended as a vehicle for stimulating dialogue among the workshop participants. Out of that dialogue will emerge the findings, conclusions, and recommendations of the National Academies' report.

The first purpose of this book is to provide a comprehensive review of the state of development of natural analogue studies with emphasis on those studies which are relevant to the following repository designs: Nagra (Switzerland) disposal concepts for high-level waste/low and intermediate-level waste; SKB (Sweden) disposal concepts for spent fuel/low and intermediate-level waste; and Nirex (UK) disposal concept for low and intermediate-level waste. The book's second aim is to discuss the expanding application of natural analogues for non-performance assessment purposes, especially their potential for presenting the concept of geological disposal to various interested audiences in a coherent, understandable and scientifically legitimate manner. Much of the discussion of the book is relevant to concepts for geological disposal of radioactive wastes by other countries, and is concerned only with those physico-chemical processes which control the release of radionuclides from the near-field, and their subsequent retardation and transport in the geosphere.

This comprehensive report discusses, in a generic sense, the scientific and technical basis for the disposal of low and intermediate level waste in near surface repositories. It is based on the experience of Member States with operational disposal facilities and on relevant national and international research and development studies. It focuses on basic principles, approaches, methodologies and technical criteria considered to be important for the design and safe operation of a near surface disposal facility, and for providing a convincing safety case that also covers the periods following repository closure and the end of institutional controls.

This publication examines the possible technological implications of retrievability when developing designs for geological nuclear waste repositories. Disposal strategies including scenarios for retrieving disposed nuclear waste have been driven by a desire to cope with or benefit from new technical advances in waste management and materials technologies, as well as changing social, economic and political conditions. In this respect, the publication analyzes the concepts currently being developed by some countries for the retrieval of emplaced waste packages and any technological provisions that should be incorporated into the design, construction, operational and closure stages of the repository. It is targeted at those responsible for deep geological disposal programs, including repository designers and decision makers.