Safety concepts regarding nuclear waste disposal in underground repositories generally rely on a combination of engineered and geological barriers that minimize potential radionuclide release out of the containment-providing rock zone and transport through the biosphere. The presence of water, however, may alter the engineered barrier system, dissolve radionuclides, and facilitate radionuclide transport that over time may permeate the biosphere. So while barrier systems aim to prevent or hinder water from contacting the waste, the possible intrusion of aqueous solutions must be considered for several safety case scenarios impacted by the long-term evolution of a repository. Dissolution and solubility phenomena thus arise as important processes controlling the chemical behaviour of radionuclides and other key materials of relevance in the context of such repositories and their safety assessments. The solubility and aqueous speciation of radionuclides is of particular interest as they provide upper limits of water-transportable concentrations of radionuclides. Solubility phenomena of radioactive and other gases in water provide important information on gas transport and pressure build-up. Moreover, solubility assessments offer insight into time-independent constraints on the evolution of the disposal system. Particularly important in this regard is the geochemical modelling of radionuclide behaviour in the engineered barrier system as well as in natural aquatic systems along the transport path of radionuclides to the biosphere. The obtained information provides valuable inputs that appropriately constrain safety analyses of nuclear waste disposal.

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.

Over the past decade significant progress has been achieved in the development of waste characterization and control procedures and equipment as a direct response to ever-increasing requirements for quality and reliability of information on waste characteristics. Failure in control procedures at any step can have important, adverse consequences and may result in producing waste packages which are not compliant with the waste acceptance criteria for disposal, thereby adversely impacting the repository. The information and guidance included in this publication corresponds to recent achievements and reflects the optimum approaches, thereby reducing the potential for error and enhancing the quality of the end product. -- Publisher's description.

To assess the relevance of colloidal influences on radionuclide transport for the long-term safety of a radioactive waste repository, the KOLLORADO-2 project integrates the results of geochemical and hydrogeological studies. The results may serve as a basis for an appraisal of the implications of colloid presence in the vicinity of radioactive waste repositories in different deep geological host-rock formations.

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.

This is an authoritative compilation of information regarding methods and data used in all phases of nuclear engineering. Addressing nuclear engineers and scientists at all levels, this book provides a condensed reference on nuclear engineering since 1958.

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.