The used fuel discharged from nuclear power plants constitutes the main contribution to nuclear waste in countries which do not undertake reprocessing. As such, its disposal requires isolation from the biosphere in stable deep geological formations for long periods of time (some hundred thousand years) until its radioactivity decreases through the process of radioactive decay. Ways for significantly reducing the volumes and radiotoxicities of the waste and to shorten the very long times for which the waste must be stored safely are being investigated. This is the motivation behind the partitioning and transmutation (P&T) activities worldwide. This paper addresses the potential impact of P&T on the long-term disposal of nuclear waste. In particular, it evaluates how realistic P&T scenarios can lead to a reduction in the time required for the waste to be stored safely. The calculations have been done independently by three research groups: ITU and FZK in Germany, and by the CEA in France.

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FEDERAL REPUBLIC OF GERMANY n 7 5 i 4 EGGENSTEIN-LEOPOLDSHAFENRecent trends in reprocessing of spent LWR-fuel necessitate improved neptunium decontamination in uranium purification cycles.For the uranium purification cycles of the WAK plant and the EUROCHEMIC plant, respectively, the time dependent performance of the 2D-extractors has been calculated using the VISCO program for the mathematical modelling of solvent extraction processes. Results have been validated using dataacquiredin laboratory-scale extraction facilities and in the plant.Intercycle evaporation and thus high uranium concentration in the aqueous feed solution results in a high organic-to-aqueous flow ratio within the extraction part of the 2D-extractor. The required neptunium decontamination is achieved by allowing a considerable amount of uranium to leave the extractor with the aqueous raffinate rather than with the organic product stream. Thereby an increased amount of process control is required. aqueous raffinate stream by feeding diluted uranium solutions, received from the preceeding backextraction step, to the 2D-extractor. Then the uranium yield of the extraction step is high, while the amount of process control required is low.AS an alternative, neptunium can be sent directly to the Copyright 0 1984 by Marcel Dekker, Inc.

Abstract. NUCLEONICA is a new nuclear science web portal from the European Commission's Joint Research Centre. The portal provides a customisable, integrated environment and collaboration platform for the nuclear sciences using the latest internet "Web 2.0" dynamic technology. NUCLEONICA is aimed at professionals, academics and students working with radionuclides in fields as diverse as the life sciences (e.g., biology, medicine, agriculture), the earth sciences (geology, meteorology, environmental science) and the more traditional disciplines such as nuclear power, health physics and radiation protection, nuclear and radio-chemistry, and astrophysics. It is also used as a knowledge management tool to preserve nuclear knowledge built up over many decades by creating modern webbased versions of so-called legacy computer codes.