Dresden 2000 – wissenschaftliches Programm

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AKE: Energie

AKE 11: Kerntechnik und Sicherheit

AKE 11.1: Hauptvortrag

Dienstag, 21. März 2000, 10:15–11:00, TMATH

Is Nuclear Waste Disposal a Scientific Challenge ? — •Jae-Il Kim — Institut für Nukleare Entsorgungstechnik, Forschungszentrum Karlsruhe, 76021 Karlsruhe

In the world, 433 nuclear power plants with an installed capacity of approximately 350 GWe (22 GWe in Germany) are in operation at present for electricity generation, while 36 are under construction, which amounts to 17 % of the total electricity production. Whereas use of nuclear energy, as is generally apprehended, extenuates a rapid depletion of convenient fossil energy sources and thus curtails the much discussed CO₂ emission problem, a serious concern remains on the long-term safety aspect of nuclear waste disposal. Up to now about 220,000 tons of spent fuel (8,300 tons in Germany) have been discharged worldwide, which contain about 1,400 tons of plutonium (over 80 tons in Germany), and substantial amounts of minor actinides (Np, Am and Cm) and fission products. At present about 11,000 tons (450 tons in Germany) of spent fuel are discharged annually.

The long-term safety entails a permanent safe confinement of long-lived radionuclides, mostly actinides and some long-lived fission products, in deep geologic formations, for which the time scale on cognition extends over a hundred thousand years. On this subject various scientific and engineering researches have been endeavored in many countries. However, one of the important aspects to be solved is how to predict with high certainty the safe confinement of radionuclides of divers chemical nature in a given disposal site on such a long time scale. For obvious reasons, this question can only be answered by well substantiated knowledge on the chemistry and nanoscopic geochemical behaviour of individual radionuclides and the physical modeling capability of their migration in a variety of the geochemical environment. Is such knowledge available already ?, if not, what are the possible solutions ? and after all, is the safety assessment of nuclear waste disposal really a scientific challenge ? These questions have in the recent years attracted growing attention of scientists involved and hence they are entreated to develop the possible solutions.

This paper describes the present state of development in the basic research relevant to the long-term safety assessment of nuclear waste disposal. One part deals with recent advances made in the nanoscopic aquatic chemistry of actinides, such as thermodynamics, speciation by laser spectroscopy or plasma-generation, dynamic surface speciation by EXAFS, etc., which provide a deep insight into the possible long-term chemical behaviour of actinides in trace concentrations in the particular geochemical environment. Such knowledge enables physical modeling of the migration behaviour of actinides which is essential for the long-term performance assessment of a given repository. The other part is concerned with an alternative solution to geological disposal, namely transmutation of long-lived radionuclides by high flux neutron sources. The development of this field is for the moment at a conceptualizing stage but much of the theoretical study has been advanced.