Off-site decontamination after the accident at the Fukushima Daiichi Nuclear Power Station generated a vast amount of soil and waste in Fukushima Prefecture.

　The JESCO law stipulates that the Japanese government shall take actions to realize final disposal of removed soil and waste outside Fukushima Prefecture within 30 years after commencement of interim storage. Japan’s Ministry of the Environment has begun activities relating to final disposal, as outlined in the Technology Development Strategy for Volume Reduction and Recycling of Removed Soil and Waste under Interim Storage developed in 2016. The ministerial ordinance and options of final disposal were developed and published by the end of 2024FY based on technical considerations up to now. MOEJ will discuss final disposal outside Fukushima Prefecture from both the technical and social perspective, while proceeding ways to foster public understanding.

Since December 2014, the Japan Environmental Storage & Safety Corporation （JESCO） has been commissioned by the Ministry of the Environment to carry out interim storage-related activities in Fukushima Prefecture under the governing laws for JESCO.

　In promoting volume reduction and recycling, specific efforts are being made in accordance with the “Technology Development Strategy for Volume Reduction & Recycling of the Removed Soil and Waste under Interim Storage”, which was formulated in 2016, with the goal of completing the development of basic technologies within ten years.

　To achieve this goal JESCO has been involved in research, studies, and technology development, as well as the management of interim storage. This paper introduces JESCO’s technology demonstration projects aimed at volume reduction and recycling of removed soil and waste.

This paper presents three representative technical scenarios （i.e. non-concentration, balanced, and maximum concentration） for managing final disposal outside of Fukushima of molten fly ash from radioactively contaminated waste stored at the interim storage facility. Details of technical issues regarding cement solidification of molten fly ash in the non-concentration scenario and the two-step chemical coprecipitation method in the maximum concentration scenario are also presented. Although methods for final disposal outside the prefecture are not finalized, the paper does outline a structure for the final disposal facility that would serve as a containment facility, the role of maintenance and management, and what approach is being used to evaluate the feasibility of the facility. While the particular volume reduction scenario to be implemented has still not yet been decided upon, the need to prepare in advance for any scenario, by resolving all technical issues, is considered to be crucial.

In order to estimate the yield of H₂ from blast furnace cement type B containing radioactive materials, and from geopolymer hardened bodies, we irradiated and stored samples at temperatures different from room temperature to 90 ℃ to simulate decay heat. We then calculated the integrated G_H2 value over a period of four weeks from the time of irradiation. The results of this study indicate that, in the case of cement, the H₂ evoluted during γ-ray irradiation was seen to diffuse within the sample body and is released outside the test body. The integrated G_H2 value reached 0.45 for the test body irradiated and stored at 90 ℃, and it was not possible to confirm that the release had finished after 4 weeks of irradiation. In addition, when melted fly ash was mixed in, the value increased by about 4 times. It was ascertained that H₂ is generated from chemically bound water in the hardened body, exhibiting a larger G_H2 than liquid water. In contrast, even at room temperature, with a maximum G_H2 value of 0.2, geopolymer exhibited a distinct behavior, wherein all H₂ was released from the test body immediately after irradiation. The introduction of melted fly ash resulted in the restriction of diffusion within the test body, however, did not lead to an increase in G_H2, as observed in the case of the cement.

Combustible waste contaminated by radio-cesium（Cs）generated by the Fukushima Daiichi Nuclear Power Plant accident has been incinerated, thermally treated for volume reduction, and stored in an interim storage facility as molten slag and fly ash with high radio-Cs concentration. Since the fly ash needs to be disposed of after interim storage, it is necessary to establish the appropriate design for the final disposal facilities and safety assessment methodology, with particular attention to radio-Cs concentrations and leaching characteristics of the stabilized fly ash. This manuscript reviews the containment structure and safety assessment concept of existing disposal facilities, such as strictly controlled landfills for toxic industrial waste and low-level radioactive waste pit disposal facilities. Based on the review, it recommends that the high affinity to radio-Cs of engineered and natural barriers should be properly incorporated in the barrier system design of disposal facilities to delay transport to the surrounding environment until the radio-Cs is attenuated to a safe level. The authors also review recent studies on the sorption performance of radio-Cs in concrete and soil-bentonite mixture, which are expected to be used as engineered barriers, particularly on the influences of high concentrations of potassium, calcium, and other solutes in the leachate. Finally, technical issues for the appropriate final disposal of the stabilized fly ash are summarized.

Regarding the interim storage and out-of-prefecture final disposal of soil removed from the Fukushima Daiichi Nuclear Power Plant accident, technical aspects and social acceptance in the receiving areas are not the only factors to be considered. Issues such as community development and communication with local residents near interim storage facility are also critical areas to be addressed. This report provides an overview of the current situation and looks at issues relevant to areas surrounding interim storage facilities through analysis results and practical knowledge extracted at an environmental restoration project using “pattern language” in a village called Iitate Mura. It introduces an example of analysis using ‘community capital framework’ and ‘participatory leaflet creation’ for Okuma Town. Finally, the paper suggests that when considering future designs for reconstructive urban development which combines both methods, the importance of consensus building and community reconstruction according to each unique local context is key.

Biological monitoring was conducted in the area surrounding interim storage facilities to assess the current state of the natural environment and to evaluate changes in the ecosystem as a result of the Fukushima Daiichi Nuclear Power Plant accident. A mammal camera trap survey was able to identify 10 species in the vicinity of the facility. A higher number of localized indigenous satoyama species, such as the Hondo raccoon dog, were observed as compared to other areas. This suggests that the indigenous natural satochi-satoyama environmental landscape is being maintained. Frequent observation of the Nosime damselfly, a type of red dragonfly, within the interim storage facility area also indicates that the environment is able to support water-dependent insects. Regarding ecosystem services, indicators related to agriculture, forestry, and fisheries, such as rice, wheat, soybeans, livestock, and marine fisheries, declined significantly due to the earthquake, both inside and outside the evacuation zone. These sectors have not yet recovered, particularly in areas where evacuation orders were issued. However, there was no significant change in regulatory services before and after the earthquake.

The soils generated through decontamination efforts following the Fukushima Daiichi Nuclear Power Station accident will finally be disposed of outside Fukushima Prefecture by 2045. This paper presents factors that relate to public acceptance of this final disposal, which were identified through online questionnaires, a postal survey, and interviews. Comprehensively summarizing the results of these surveys, public acceptance of final disposal was affected by what the process for this final disposal would be, including procedural and distributive fairness, as well as individual social psychological factors such as trust in the implementing entity, perceived risks, and perceived social benefits. In order to promote public acceptance of final disposal, it will be particularly important to: （1） ensure distributive fairness including nationwide promotion of soil recycling,（2） disclose social significance in addition to safety and economic efficiency, and （3） dispel distrust through approaches based on procedural fairness including transparency, accountability, and comprehensiveness.

The issue of removed soil needs to be emphasized from the perspective of multi-dimensional justice. Particularly, the residents who relinquished their land for use as interim storage facilities must be prioritized from the principle of maximum improvement for the least advantaged people. This paper summarizes the outcome of our research conducted to foster public acceptance of the removed soil issue with a focus on pluralistic justice. Various methods, including group decision experiments, citizen participation workshops, and gaming, have been used. Results of this exercise demonstrate that citizens can engage in dialogue while taking Fukushima residents into consideration and can make decisions that prioritize those carrying the burden under certain conditions. Nevertheless, some agenda points have also arisen and need to be addressed. Providing objective and neutral information does not necessarily evoke a sense of involvement. Moreover, people who are living at a distance from Fukushima and had never benefited from the Fukushima Nuclear Power Plant found it difficult to understand the perspectives of Fukushima residents who have borne the burden. Gaming was developed as one tool for tackling such problems, but it still has not been fully implemented within society. Finally, we discussed the next research projects to continue to target and overcome the above challenges.