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

Lead Research Organisation: University of Sheffield
Department Name: Materials Science and Engineering

Abstract

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.

Planned Impact

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.

Publications

10 25 50
 
Description - Process conditions to solidify and dehydrate the phosphate-based cement developed in this project has been established.
- Incorporation of simulated secondary aqueous wastes has been achieved, and their effects evaluated.
- Gamma and electron irradiation tests have been conducted, and a reduced risk of hydrogen gas generation confirmed
- Leaching tests were conducted, and superior immobilisation of strontium in the developed cement matrix was discovered
- Dehydration process was largely influenced by the are of the exposure surface.
- Slow heating by the conventional oven was better than the rapid heating by an industrial scale microwave.
Exploitation Route The outcomes of the project will be reviewed by the governmental committees in Japan after the end of the project.
Sectors Construction,Energy,Environment

 
Description Decontamination activities in Fukushima generates variety of radioactive wastes that are significantly different from the wastes arising from conventional operation of nuclear power plants. One of such waste streams is the secondary aqueous wastes generated from the cleaning of the contaminated water. Because it is highly radioactive, hydrogen gas can be produced through the radiolysis of the water, which can cause a serious concern in the storage of the wastes and standard solidification process using conventional cement matrices. Out findings so far proves that it is possible to solidify these wastes using the developed cementitious matrix with a significantly reduced water content, which can reduce the risk of hydrogen gas generation. We have produced simulated wasteforms to incorporate simulated aqueous wastes in the developed cementitious matrix, and currently investigating their properties, to assess their feasibility for practical application.
Sector Chemicals,Construction,Energy,Environment
Impact Types Cultural,Economic

 
Description EPSRC UK-Japan Civil Nuclear Phase 3
Amount £600,000 (GBP)
Funding ID EP/P013171/1 
Organisation Engineering and Physical Sciences Research Council (EPSRC) 
Sector Academic/University
Country United Kingdom
Start 11/2016 
End 03/2019
 
Description Engineering And Physical Science Research Council (Epsrc) IAA
Amount £23,855 (GBP)
Funding ID R/143154 
Organisation University of Sheffield 
Sector Academic/University
Country United Kingdom
Start 05/2015 
End 09/2015
 
Description Development of versatile cementitious matrix for Fukushima's decontamination wastes 
Organisation Japan Atomic Energy Agency (JAEA)
Country Japan 
Sector Public 
PI Contribution We have hosted a PDRA from JAEA to conduct a feasibility investigation on a new cementitious matrix for radioactive waste encapsulation.
Collaborator Contribution JAEA provided a PDRA to undertake the titled project.
Impact This collaboration formed the foundation of the awarded project. The direct outcomes of the project have been presented at two conferences shown below, one of which won a poster prize. Keita Irisawa, Amar Kamarulzaman, Ines Garcia-Lodeiro, Yoshihiro Meguro, Hajime Kinoshita, "Effect of phosphate modification on incorporation of caesium nitrate by calcium aluminate cement," Oral presentation at 4th Mechanisms and Modelling of Waste/Cement Interaction, Switzerland, May 2016. Keita Irisawa, Sze Wing Yeung, Patcharapak Suriwong and Hajime Kinoshita, "Effects of composition on calcium aluminate phosphate cement for caesium nitrate incorporation," Oral and poster presentation at 35th Cement and Concrete Science Conference, Aberdeen, August 2015
Start Year 2015
 
Description Electric leaching tests on cementitious nuclear wasteforms 
Organisation University of Kyoto
Department Laboratory on Innovative Techniques for Infrastructures
Country Japan 
Sector Academic/University 
PI Contribution Partnership within the large project currently on-going (Development of solidification techniques with minimised water content for safe storage of secondary radioactive aqueous wastes in Fukushima), originated from a smaller collaboration between Sheffield- Hokkaido started in 2014. We provide the materials to test at Kyoto to be tested using their facility of electric leaching.
Collaborator Contribution They conduct testing on the materials provided from us - simulated cementitious wasteforms aiming to apply for the radioactive secondary wastes arising from the decontamination of water in Fukushima.
Impact This is collaboration between materials scientists and civil engineers. The outcomes of this specific collaboration is yet to be established, but the outcomes of the overall project are listed elsewhere.
Start Year 2015
 
Description Training of next generation nuclear engineer in Fukushima 
Organisation Fukushima National College of Technology
PI Contribution As an official overseas partner of the consortium, we host the students on this programme in our group to provide training on research and professional skills via internship.
Collaborator Contribution With a support from Japanese Government, Fukushima National College of Technology is strategically fostering talented students in Fukushima region to educate engineers of next generation specialising in nuclear waste management and reprocessing who can meet the demand of the society and industry. They will lead the programme, select students and provide opportunities of trainings through internship and visits within Japan.
Impact This partnership is yet to produce outputs.
Start Year 2018
 
Description Cross-disciplinary Seminar, Research Institute of Nuclear Engineering, University of Fukui 
Form Of Engagement Activity Participation in an activity, workshop or similar
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Provided a series of 3 lectures on the current research activities at 94th Cross-disciplinary seminar of Research Institute of Nuclear Engineering, University of Fukui (01 May, Tsuruga, Japan 2017). Approximately 50 audience, both students and staff participated, and discussed the waste management research for recovery of Fukushima.
Year(s) Of Engagement Activity 2017
 
Description Hosting visitors from National Institute of Technology, Fukushima College 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Undergraduate students
Results and Impact The representatives from Fukushima College (3 undergraduate students and 2 academic staff) visited the Department of Materials Science and Engineering at The University of Sheffield, to see the research activities in the decommissioning of nuclear power plants and environmental recovery, currently undertaken at Sheffield. This was a part of the training of the next generation of engineers commissioned by the Nuclear Regulatory Agency in Japan. (Visit 1: March 2018, Visit 2: September 2018, Visit 3, March 2019)
Year(s) Of Engagement Activity 2018,2019
URL https://www.sheffield.ac.uk/materials/news/fukushima0703-1.767398
 
Description International seminar on Decommissioning of Fukushima Daiichi Nuclear Power Station 
Form Of Engagement Activity Participation in an open day or visit at my research institution
Part Of Official Scheme? No
Geographic Reach International
Primary Audience Postgraduate students
Results and Impact Through the group discussion and debates, as well as presentations of the leading experts from US, France, UK and Japan, this seminar inspired young researchers and postgraduate students in Japanese research institutions and industry in the area of decommissioning of nuclear power plants.
Year(s) Of Engagement Activity 2018
URL https://fukushima.jaea.go.jp/en/hairo/frc/frc02_20180926.html