Prospects for melt refining of radioactive waste from fusion reactors

Abstract

Fusion has the prospect of producing only low-level radioactive waste, but the volume of this waste is potentially very large. A possible means of reducing the volume of this waste is to recycle the activated materials, e.g. within the fusion industry. In the process of steelmaking, certain impurities are removed via accumulation in slag or fumes produced during the process, and this has been successfully employed as a means of clearing surface-contaminated LWR steels (e.g. steam generators). In this work, we simulate the process applied to neutron-activated fusion reactor components including the blanket, divertors, and shielding.The process is based on a well known partitioning between melt, slag, dust, and gas that is based on the oxidation potential of the elements and their volatility. We model this partitioning of activated materials and use FISPACT-II to simulate their activation during operation; the processes are repeated cyclically to simulate the long-term accumulation of activation products in the steel and waste products. The principal findings are that most of the induced activity remains in the metal rather than accumulating in the slag, and that while the slag remains a low-level waste under the assumptions employed, its volume actually exceeds that of the recycled material, and it therefore did not constitute a successful waste volume reduction technique.