The handling of actinides and actinide-based materials provides significant technological challenges due to the toxicity and radioactivity associated with these materials. These challenges are particularly apparent in the nuclear power industry. Under normal operation, a reactor can produce a significant amount of spent fuel requiring subsequent containment for geologic times, and under accident conditions it can release lethal doses of radioactive material to the environment. Inevitably, radioactive material will enter the environment, necessitating as complete an understanding as possible of its behavior. An understanding of the interaction between actinides and the environment must be based on a knowledge of their basic physical and chemical properties. To date, although there is general agreement on the principles for waste disposal, no facility has been built for the long term disposal of high level radioactive waste from either normal reactor operations or from accidental catastrophes. This makes it most important for the scientific and technical community to develop the necessary cross-disciplinary understanding that will help us implement safe and secure waste management, accident remediation and accident prevention systems.

Zusammenfassung
Proceedings of the NATO Advanced Study Institute, Maleme, Crete, Greece, July 7-19, 1996

Inhalt
The transuranium elements: From neptunium and plutonium to element 112.- Solid state chemistry and thermophysical properties of the actinides.- Electronic structure of the actinide elements.- Bulk properties of light actinides from first principles.- 5f-Electrons localization of the actinide metals, ?-plutonium case.- Lattice relaxation and the stability of plutonium-based alloys and intermetallics.- Electronic structure and structural stability of uranium dioxide.- Synthesis and crystal structure of new quaternary silicides of uranium.- Structural chemistry of new quaternary germanides of uranium.- Main features of improvement of existing NPP units and creation of new ones in Russia: Principal safety aspects.- Conception of VVER reactors with coated particles.- Improvement of the models and codes for RBMK neutronic calculations.- Nuclear heating power plant technical safety decisions.- Modeling of the experiments with natural circulation of a molten fluoride salt fuel.- Geological disposal of high level radioactive waste.- Spent fuel characteristics and disposal consideratios.- Thermochemistry of crystalline and amorphous phases related to radioactive waste.- Potential long term disposal of plutonium in the stockpile.- Application of radiochemical, accelerator-based and surface analytical techniques to the investigation of the U- and Th-interaction with tectosilicate minerals.- Lanthanide oxalates as a possible form of intermediate separation for long-lived fission-product nuclides.- Interactions of radionuclide with hard rock.- Radionuclide dispersal pathways: Some general considerations and examples.- Fission products and transuranic elements released into the environment during the Chernobyl accident.- Remediation of the Chernobyl accident site.- Radioactive wasteand contamination in the Arctic regions Perspectives on the impact on its indigenous peoples.- Fate and transport of plutonium in forest ecosystems: Assessment using the FORESTPATH model.- Plutonium content in Black Sea sediments and algae.- Uranium in the environment in surrounding areas of the Romanian nuclear power plant during the pre-operational period.- Use of high gradient magnetic separation for actinide applications.- Actinides in Portugal.- Social and psychological sources of the Chernobyl accident.- Indices.- Author Index.