Das Projekt "Schmelzen von radioaktivem Altmetall aus kerntechnischen Anlagen" wird vom Umweltbundesamt gefördert und von Siempelkamp Nuklear- und Umwelttechnik durchgeführt. Objective: This research is based on the results and experience of work carried out at Siempelkamp in the framework of the first five-year (1979-83) programme (ref.: eur 10021). The preceding research work proved that it is possible to melt down contaminated scrap by means of a modified industrial furnace device in compliance with the legal limits and regulations. This research work, therefore, aims mainly at the behaviour of radionuclides during the melting procedure, with regard to various material qualities and the harmless recycling of melted-down metal parts coming from refurbishing and decommissioning of nuclear installations. General information: b.1. Planning and design of the melt device taking into account an existing furnace. B.2. Construction of the needed melt device components. B.3. Melt work using as scrap contaminated carbon steel, stainless steel and its mixture. B.4. Evaluation of melt results. B.5. Technical, economical and radiological consequences. B.6. Extrapolation economical and radiological consequences. To large nuclear power plant and comparison with alternative modes with a view to the economical and environmental aspects. B.7. Melting of contaminated galvanised sheet material. B.8. Melting of non-ferrous metal (e.g. copper and brass) to investigate the behaviour of relevant radionuclides (e.g. co-60, cs-137) during the melting process. B.9. Investigation on adding radioactive carbon to the steel melt process to obtain cast iron of suitable quality for e.g. disposal containers. B.10. Investigation on the long-term behaviour of the furnace liner, the charging device and the filter system after melting of about 500 t of contamined steel waste (over two years) with particular view to activity concentration in the different parts of the melting plant. Achievements: To date, approximately 3500 tonnes of very low level contaminated steel components from the refurbishing and dismantling of various nuclear installations in Germany have been treated by melting. 95 per cent of the radioactivity was due to cobalt-60 and caesium-137 with an average ratio of 60:40. After melting, caesium was found in the slag and filter dust, whereas cobalt-60 mainly remained in the ingot (90-99 per cent). A special melting facility has been constructed to treat components which have been contaminated up to a level of 200 Bq/g in a controlled area. Approximately 2000 tonnes of steel components have been melted, so far, in this facility and to a large extent it has been recycled for nuclear purposes such as for transport and disposal containers and biological shieldings. One of the most important problems was to quantify the amount of secondary waste produced during melting (e.g. slag, filter dust). Melting of radioactive waste metal from the dismantling or refurbishing of nuclear installations has been assessed with respect to recycling (e.g. type A and type B containers for transport and/or final disposal, and shieldings). Long term tests ...
Das Projekt "Grosse, aus schwach radioaktivem Altmetall gegossene Abfallbehaelter" wird vom Umweltbundesamt gefördert und von Siempelkamp Nuklear- und Umwelttechnik durchgeführt. Objective: radioactive waste coming from dismantling of large reactor components should be transported in larger containers than those already used, in order to save cutting work and, consequently, radiation exposure of personnel. The use of radioactive steel for manufacturing transport and disposal containers reduces the volume of waste to be stored, and also metal consumption. A reference container will be chosen in agreement with requirements for the Konrad disposal site and suitable for fabrication out of low-level radioactive steel (specific activity up to 74 bq/g). In a supplementary agreement concluded in 1988, the initial work programme was extended to studies related to the qualification requirements for waste containers, presently under development at the physikalisch-technische Bundesanstalt (PTB). This will be applied to the available prototype container Waco i. General information: b.1. Optimisation of type a cast steel containers, taking into account all relevant requirements for safe transport and disposal in the Konrad mine. B.2. Design of a prototype container based on the previous optimisation. B.3. Fabrication of the prototype container with lid and all accessories (plugs, sealing, screws...) And testing under boundary conditions as given by iaea and German regulations. B.4. Establishment of a radiological measurement programme and measuring of all relevant activities occurring before and during fabrication, and on the finished container. B.5. Design studies and experiments aiming at optimising the prototype as regards leak tightness and the potential for repairs. B.6. Five experiments on the prototype with a view to assessing leak tightness and mechanical integrity. B.7. Definition of the original status and back fitting of the prototype with above developed methods. B.8. Radiological studies into the health physics consequences for given release rate and activity inventories.