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.

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.

In order to validate predictive models of the very long-term processes which affect the performance of radioactive waste repositories, there has been an increased interest in the information and understanding which can be obtained from studying similar mechanisms in natural systems. These "natural analogues", as they are known in the jargon of waste management, have been studied sporadically for many years, but there has been a considerable rejuvenation of interest in the last four years, possibly owing to the fact that performance assessment methodolo gy is gradually maturing to the point where it needs the kind of support which analogues can offer. Since 1982, the Commission of the European Communities has been involved in specific work on natural analogues in the framework of its activities on radioactive waste management, principally within the MIRAGE project which concerns migration of radionuclides in the geosphere. As a consequence, the Commission took the initiative, in 1985, of establish ing a Natural Analogue Working Group (NAWG) whose members can benefit from the overall expertise available for managing their own natural analogue research programmes. In this group, modeller' s requirements and the results of field research are exchanged at regular intervals. A number of wide-ranging investigation programmes, both on national and international scales. are currently underway or being initiated, and several of these have been discussed recently at the NAWG.

There is an extremely voluminous literature on radioactive waste and its disposal, much in the form of government-sponsored research reports. To wade through this mountain of literature is indeed a tedious task, and it is safe to speculate that very few, if any, individuals have the time to examine each report that has been issued during the preceding ten years. This book attempts to summarize much of this literature. Further, many workers in the geosciences have not received training in the nuclear sciences, and many nuclear scientists could be better versed in geology. In this book an attempt is made to cover some background material on radioactive wastes and geotoxicity that may not be an integral part of a geologist's training, and background material on geology and geochemistry for the nuclear scientist. The geochemical material is designed for both the geoscientist and the nuclear scientist. There is no specific level for this book. Certainly, it should be useful to advanced undergraduates and graduates studying geology and nuclear science. It does not pretend to cover a tremendous amount of detail in all subjects, yet the references cited provide the necessary source materials for follow-up study. It is my intention that the reader of this book will have a better, broader understanding of the geochemical aspects of radioactive waste disposal than is otherwise available in anyone source.

In order to validate predictive models of the very long-term processes which affect the performance of radioactive waste repositories, there has been an increased interest in the information and understanding which can be obtained from studying similar mechanisms in natural systems. These "natural analogues", as they are known in the jargon of waste management, have been studied sporadically for many years, but there has been a considerable rejuvenation of interest in the last four years, possibly owing to the fact that performance assessment methodolo gy is gradually maturing to the point where it needs the kind of support which analogues can offer. Since 1982, the Commission of the European Communities has been involved in specific work on natural analogues in the framework of its activities on radioactive waste management, principally within the MIRAGE project which concerns migration of radionuclides in the geosphere. As a consequence, the Commission took the initiative, in 1985, of establish ing a Natural Analogue Working Group (NAWG) whose members can benefit from the overall expertise available for managing their own natural analogue research programmes. In this group, modeller' s requirements and the results of field research are exchanged at regular intervals. A number of wide-ranging investigation programmes, both on national and international scales. are currently underway or being initiated, and several of these have been discussed recently at the NAWG.

The perception of radioactive waste as a major problem for the industrial world has developed only recently. Four decades ago the disposal of such waste was regarded as a relatively minor matter. Those were the heady days when nuclear fission seemed the answer to the world's energy needs: the two wartime bombs had demonstrated its awesome power, and now it was to be harnessed for the production of electricity, the excavation of canals, even the running of cars and airplanes. In all applications of fission some waste containing radioactive elements would be generated of course, but it seemed only a trivial annoyance, a problem whose solution could be deferred until the more exciting challenges of constructing reactors and devising more efficient weapons had been mastered. So waste accumulated, some in tanks and some buried in shallow trenches. These were recognized as only temporary, makeshift measures, because it was known that the debris would be hazardous to its surroundings for many thousands of years and hence that more permanent disposal would someday be needed. The difficulty of accomplishing this more lasting disposal only gradually became apparent. The difficulty has been compounded by uncertainty about the physiological effects oflow-Ievel radiation, by the inadequacy of detailed knowledge about the behavior of engineered and geologic materials over long periods under unusual conditions, and by the sensitization of popular fears about radiation in all its forms following widely publicized reactor accidents and leaks from waste storage sites.

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.