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

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.

The largest, and no doubt the most important impact that the successful outcome of this research can make, is the actual application of the developed solidification technology for the secondary aqueous wastes arising from the processing of the contaminated water at Fukushima Daiichi Nuclear Power Plant. As such, we identify four main beneficiaries from the research: Japanese Governmental bodies; Japanese nuclear community (i.e. public); and Japanese and international academic and industrial nuclear communities. In detail:

- Japanese Governmental bodies, such as the Nuclear Damage Compensation and Decommissioning Facilitation Corporation (NDF) and the International Research Institute for Nuclear Decommissioning (IRID) will benefit from close communication of our research progress and outcomes through the Japanese research partners. This will ensure that the proposed research continues to align with the recently published Fukushima Roadmap to decommissioning.
- The large scale demonstration of the heating solidification process will help to improve Japanese Governmental and public confidence in the Fukushima Daiichi NPP site decommissioning. Improved public confidence will also be realised in the UK, which will ultimately benefit the governmental bodies responsible for nuclear waste management (e.g. Nuclear Decommissioning Authority) and nuclear waste disposal (Radioactive Waste Management Limited).
- The dissemination of the research outcomes of this proposal to the international community and the nuclear academic community in Japan will us to promote the research and attract further collaborators, building an extended network for the development of decommissioning technologies using a novel cementitious material approach. For example, we will disseminate our research at the Atomic Energy Society of Japan (AESJ) biannual meeting. The UK-Japan based research will therefore help to promote an internationally-leading research community in the field of nuclear power plant decommissioning, which will have impacts not only to those countries participating, but also specifically to support the UK Government's ambition to promote nuclear power research and development. This will have far-reaching impacts to the UK economy, the environment and society.
- In accordance with the EPSRC and STFC review of Nuclear Engineering, this research will produce highly skilled and knowledgeable post-doctoral scientists for potential recruitment by the nuclear industry, with awareness of both UK and Japan decommissioning issues.