Development of solidification techniques with minimised water content for safe storage of secondary radioactive aqueous wastes in Fukushima

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The processing of contaminated water from the TEPCO Fukushima Daiichi Nuclear Power Plant (NPP) results in a large amount of secondary aqueous wastes. They are highly radioactively contaminated, and those produced at the early stage of the processing also contain significant amounts of sea salt. Due to the significant radioactivity and water content, hydrogen gas is generated from these wastes, and their long-term storage faces the potential risk of not only leakage, but also explosion and fire. For the safe storage of these wastes, they must urgently be converted into a form that has a reduced risk of leakage as well as a minimised fire risk due to hydrogen gas generation. Thus, the proposed project aims to develop a solidification technique with minimised water content for the safe storage of secondary aqueous radioactive wastes from the Fukushima Daiichi NPP.The project has strong bilateral UK and Japan links, incorporating expertise from both universities and the Japanese Atomic Energy Agency. The joint research will focus on the immobilisation of secondary aqueous wastes, which are problematic since they incorporate a large number of compounds (e.g. 90Sr, Mg(OH)2, NaCl), making their chemistry complex. We will develop a novel solidification technique, through heat-treatment, based on magnesium phosphate and calcium phosphate cement chemistry that will result in a safe, passive wasteform. This wasteform will be fully characterised and its irradiation stability and long-term aqueous stability will be determined, to develop an understanding of its behaviour under further interim storage or final geological disposal conditions. The success of the project will lead to improved public and government confidence in the decommissioning and waste management practises at the Fukushima Daiichi NPP, in addition to supporting UK nuclear waste decommissioning strategies.