Symposium D
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The Seventh International Symposium on the Scientific Basis for Nuclear Waste Management attracted 129 invited and contributed papers. This year's symposium differed from those of previous years in that the geomedia-specific research relating to repository placement was emphasized. The media-specific theme was timely since United States repository sites have recently taken on expanded roles for development of site-specific information relative to repository licensing and also because basic research activities in other countries are becoming more focused. The geomedia that have received the largest amount of research applicable to nuclear waste disposal are basalt, salt, tuff, and granite. A half-day session was devoted to materials research related to disposal of nuclear waste in each of the four media types. Interactive phenomena between containment materials, radionuclide release and radiation/radiolysis effects were among the research reported in the environments characteristic of each geomedia. Some of the significant findings reported included the incorporation of low alloy steels into aqueous environments containing silicate waste forms in enhanced reaction rates and colloidal particle formation. The iron also serves as an effective scavenger for many radionuclides. Radiolysis effects were found to generally enhance radionuclide release rates and metallic barrier materials corrosion rates. Alpha radiolysis was particularly effective at creating an oxidizing environment in salt brine, which can have significant effects on actinide solubility limits. Ionizing radiation (gamma) was shown to cause metallic sodium generation in bedded rock salt. Additionally, models for predicting radionuclide release from repositories in each geomedia were described. The four media-specific sessions were evaluated on a technical basis by three distinguished members of the scientific community not associated with any geomedium (repository site). The review panel members were Dr. G.A. Cowan, Los Alamos Scientific Laboratory; Dr. C.A. Heath, NUS Corporation, and Prof. D.D. Runnells, University of Colorado. Their review was frank and even-handed. All three review panel members agreed that nuclear wasterelated research has come a long way in the past several years and that the important factors are now being considered and evaluated. They all agreed that the quality of research has improved and that a much better level of understanding is evident. However, the geomedia-specific research was criticized for its lack of focus and for a lack of communication between scientists and managers in the various research areas. Concern was expressed that the requirements for licensing a repository (both NRC and EPA) are not being adequately considered in nuclear waste disposal-related research. The end product of this research is supposed to be to demonstrate the licensability of a
G.L. MCVAY
repository in a specific geomedium. Modeling activities of the entire repository system are critical and are not adequately addressed in existing programs
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