Post-nuclear-accident Radiation Protection as Seen from the Basic Policy for the Final Disposal of Contaminated Soil
By Tanimura Nobuko
Reflections on the aftermath of the nuclear accident
The accident at Tokyo Electric Power Company’s Fukushima Daiichi Nuclear Power Station brought about radioactive contamination of the environment, and “decontamination” to reduce the atmospheric radiation dose rate was carried out not only in Fukushima Prefecture but also across a wide area of eastern Japan. Areas with levels of 0.23 microsieverts/hour (μSv/h) or more were targeted for decontamination, and public decontamination efforts were carried out not only in Fukushima Prefecture but also by local governments in Iwate, Miyagi, Gunma, Tochigi, Ibaraki, and Chiba prefectures. Since radioactive materials are not eliminated by decontamination, large amounts of highly contaminated soil (removed soil) and waste materials were generated.
In Fukushima Prefecture, an intermediate storage facility began operation in a location straddling the towns of Okuma and Futaba in March 2015. The facility was intended as a temporary facility, as seen in one document distributed at a resident briefing, which states, “Large amounts of soil and waste containing radioactive materials are generated in association with decontamination, etc. Since the amount of soil and waste containing radioactive materials will be enormous in Fukushima Prefecture, it is difficult to clarify the final disposal method at this point. For this reason, intermediate storage facilities are facilities for the safe and intensive management and storage of soil and waste containing radioactive materials until final disposal.”1 It is also stipulated by law that the national government should “Take necessary measures to complete final disposal outside Fukushima Prefecture within 30 years from the start of interim storage.”2
As of the end of December 2024, approximately 14 million (M) cubic meters of removed soil was stored in interim storage facilities within Fukushima Prefecture, and a total of approximately 0.33M cubic meters was stored by local governments outside Fukushima Prefecture.3
Policy for the disposal of soil contaminated by radioactivity
Stating that reducing the volume of removed soil is the key to establishing a final disposal site for removed soil outside Fukushima Prefecture, the national government has decided on a policy of reusing soil below a certain concentration level. Since 2015, the Ministry of the Environment (MoE) has been conducting studies and demonstration projects on technologies related to volume reduction and recycling of removed soil, and on the promotion of recycling. As a result of these studies over the past decade, MoE announced the “Results of Efforts for Final Disposal Outside Fukushima Prefecture thus Far and How to Proceed from FY2025,” “Guidelines for Reconstruction and Revitalization,” and “Guidelines Related to Landfill Disposal of Removed Soil Generated Outside Fukushima Prefecture” in March this year. In fact, however, where plans for demonstration projects were proposed, in areas both inside and outside Fukushima Prefecture, opposition to the plans arose from residents, and this has led to the projects in their planned form being abandoned. The outlook for the selection of a final disposal site is looking bleak.
In December last year, the Promotion Council for the Final Disposal of Removed Soil from Fukushima Prefecture, which includes all ministers of state except the prime minister was established, announced its basic policy in May this year.4 Recognizing the necessity to build national understanding and strengthen risk communication in order to realize final disposal outside Fukushima Prefecture, the basic policy stated that the government will take the lead in efforts to creating precedents, such as the use of soil at the prime minister’s official residence. Other than that, similar efforts as in the past were listed, such as posters with easy-to-understand explanations, the use of websites and SNS, the holding of study tours, and explanations of IAEA safety standards. The plan is to compile a roadmap for the next five years during this summer.
Recycling standards
The recycling of removed soil in Fukushima Prefecture has been termed “use for reconstruction and revitalization,” and the standard has been set at a combined radioactive cesium 134 and 137 total of 8,000 becquerels (Bq) or less per 1 kg (Bq/kg). Use for reconstruction and revitalization is defined as “the use of removed soil recycled as revitalization materials under appropriate management (including maintenance and management) for the purpose of contributing to revitalization from disasters caused by the accident” and is planned to be implemented in public works and other areas.5 The standard concentration was calculated such that the annual exposure of construction workers would be 1 millisievert/year (mSv/y) or less. Further, regarding the double standards for the clearance level (100 Bq/kg), which refers to materials that do not need to be treated as radioactive materials and the standard concentration mentioned above, MoE explains that this difference is due to the difference between “standards for safe reuse of waste” and “standards for safe treatment and disposal of waste.”6
Handling of contaminated waste from the accident
Waste contaminated by radioactivity was generated over a wide area after the accident, and incineration caused problems by resulting in materials with higher concentrations. The standard for “designated waste,” which the government is responsible for disposal, was set at 8,000 Bq/kg or more, making it possible to dispose in the normal way any waste below that level.7 Prior to this, the Nuclear Safety Commission (as it was at the time) issued the following statement regarding the concept of radioactive waste. “It is desirable that items that were affected by the accident at the Fukushima Dai-ichi NPS and are to be disposed of (debris, water purification and sewage sludge, incineration ash, plants and trees, and soil generated from decontamination activities, etc.) should be treated under appropriate management with due consideration for the safety of surrounding residents and workers and finally disposed of. Treatment and disposal of the waste affected by the accident is one of the important activities for the improvement of the living environment of the local residents in the present radiation exposure situation.” “1. Regarding recycling, it is thought that a part of the waste material affected by the accident may be reused. It is necessary to confirm that the concentration of radioactive materials is appropriately controlled so that the concentration of radioactive materials falls below the standard (10 μSv/year) used for setting the clearance level before the product is distributed to the market.”8 (Underlines by the author)
Decontamination was necessary to reduce the exposure of residents living in an already contaminated environment (existing exposure situation), and since the generated waste had to be treated, a standard was set such that the exposure resulting from treatment would be below a certain amount. What should be highlighted here is that reuse was being considered below the clearance level. About three months after the accident occurred, of the various levels of contaminated waste materials (including soil), those with a radiation dose not exceeding 1 mSv/year were targeted for treatment, and reuse was being considered for a part of the waste material below the clearance level. There was no mention of recycling contaminated soil outside the region.
Furthermore, the policy had been that the national government would be responsible for constructing disposal sites for the disposal of designated waste in the prefectures where it had been generated, but the selection of sites ran into problems. Time passed without disposal, and the situation is that the designation is being lifted due to the natural attenuation of radiation.
The Guidelines Related to Landfill Disposal of Removed Soil Generated Outside Fukushima Prefecture laid out procedures for landfill disposal of removed soil stored outside Fukushima Prefecture under the responsibility of municipalities. About 95% were evaluated to be less than 2,000 Bq/kg, but the Guidelines mentioned measures based on the Ordinance on Prevention of Ionizing Radiation Hazards when the concentration exceeded 10 thousand (K) Bq/kg. Surprisingly, in spite of the background of soil removed from inside Fukushima Prefecture being different from that of soil removed from the prefecture, the Guidelines stated that the use for reconstruction and revitalization of soil outside the prefecture was not negated.
Volume reduction and social acceptability of final disposal sites
The study group on volume reduction technology examined and evaluated four scenarios in which soil with a concentration of more than 8,000 Bq/kg was treated and then divided into soil with a concentration of less than 8,000 Bq/kg and soil with a higher concentration (Table 1).
Table 1: Multiple options for final disposal outside Fukushima Prefecture
Without volume reduction, the final disposal volume was about 2.1 million to 3.1 million m3 of soil with a concentration of several tens of thousands of Bq/kg. However, when soil is concentrated to the highest concentration by combining volume reduction technology, the final disposal volume was about 50K to 0.1Mm3 of soil with a concentration of several tens of millions of Bq/kg. The final disposal volume decreases as the concentration increases, but disposal costs are high and secondary waste is generated. The structure of the final disposal site as well as the exposure assessment during work and after burial differ depending on the scenario.
From 2025 onwards, the final disposal scenario will be scrutinized and changes in social acceptability due to the radioactivity concentration are to be considered. Technically, any concentration can be achieved, but there is no plan to recycle soil that has been cleaned below the clearance level.
Exposure situations and reference levels
The International Commission on Radiological Protection (ICRP) distinguishes three types of exposure situations in its approach to radiation protection, and Japan is taking measures based on this concept (Table 2). These situations are not distinguished by measurable physical values such as air radiation dose rates and concentrations of radioactive materials, and the reality is that no clear spatiotemporal line has been drawn in Japan after the nuclear accident.
Table 2: Three types of exposure situations
Before a nuclear accident occurs, the public is basically in a planned exposure situation (said to be exposure to the natural nuclide radon and aircrew, who are considered to face existing exposure situations). In this situation, unjustified exposure is restricted. An emergency exposure situation is defined as a situation in which adverse effects cannot be avoided due to inability to control an unstable nuclear reactor after an accident. In Japan, this refers to areas where evacuation and refuge zones were established after the Fukushima nuclear accident. It was also stated that there are areas where “a transition to an existing exposure situation occurs when the release of radioactive materials is controlled and the exposure due to residual materials can be managed such as to be below a certain level” and thus are considered to have reached existing exposure conditions without passing through an emergency exposure situation.9
A radiation dose limit of 1 mSv/y is set for the public only in planned exposure situations. There are no dose limits for emergency and existing exposure situations, reference levels being used. The reference level is 100 mSv/y or lower for the former, and the lower half of 1 to 20 mSv/y for the latter. The reference level identifies people who are exposed in excess of that level and prioritizes the protection of those who are exposed to higher doses. It is not permitted for the public to exceed the dose limit without reason, but it is assumed that some people will exceed it even though the reference level has a wide range. The fact that the planned exposure situation disappears once a nuclear accident occurs can be said to mean that the dose limit is a loose regulation that does not need to be observed in an emergency.
Which areas are exposed to existing exposure situations?
The removed soil “Guidelines for Reconstruction and Revitalization” contains the following passage.
< Radiation Protection Concept >
Since use for reconstruction and revitalization is action taken to recover from the accident, the reference level for existing exposure situations (1 to 20 mSv/y) is taken as the starting point for discussion. As this level used under the responsibility of decontamination implementers on the premise of appropriate maintenance and management, 1 mSv/y, which is the upper limit of dose limits and dose constraints for planned exposure situations, it is used as a reference and the standard dose (additional exposure dose) was set to 1 mSv/year or less. (Author’s note: ‘decontamination implementers’ are the national government inside Fukushima Prefecture, and local governments in areas outside the Fukushima Prefecture.)
The expressions “as the starting point for discussion” and “is used as a reference…” are used to make the context ambiguous. However, the government is plotting to use removed soil (radioactive materials) stored under existing exposure situations, i.e. “in a condition where exposure already exists at the time of making a decision on management,” in areas (nationwide) where exposure does not already exist, in other words, where existing exposure situations cannot be said to exist. Because everyone is working together to rebuild the country, the policy is to bring unbeneficial exposure to the areas to which the soil is transported by claiming that the whole of Japan is in an existing exposure situation. Does this make any sense?
The annual level of 1 mSv/y has been adopted in various standards, with the explanation that anything below that level is safe. Meanwhile, the national standards adopted for the concentration of radioactive materials in food, public decontamination standards, standards for the disposal of radioactive waste, and so on, when added together, already exceed 1 mSv/y. The Radiation Council, under the jurisdiction of the Nuclear Regulation Authority, has indicated its view on the dose limit by stating, “The total exposure from all relevant radiation sources shall not exceed the dose limit.”10 In February this year, however, the government shelved this principle and announced its view that, in line with the government policy of recycling removed soil, a concept “close to the planned exposure situation will also be introduced” into the radiation protection concept of the reconstruction and revitalization use.11 What does “close to” mean? The government is making very convenient use of the three types of exposure situations.
When will the existing exposure situation end?
After a major nuclear disaster, when and under what circumstances will society return to the planned exposure situation? When will the day come when exposure to citizens is limited to 1 mSv/y at most? In the case of the 1986 accident at the Chernobyl Nuclear Power Plant, it is said that areas outside the nuclear power plant site have returned to the existing exposure situation since 1991.12 There is no legal regulatory document that determines the lifting of long-term protective measures, and the existing exposure situation remains in place almost 40 years after the accident. The end of the existing exposure situation requires caution because it also means the end of the compensation system, but continuation of the existing exposure situation is also grounds for avoiding strict radiation protection.
Before 2011, neither the government nor the electric power companies imagined the massive amount of contaminated soil resulting from the Fukushima nuclear accident or the final disposal outside the prefecture that the government has promised. The lesson of the Fukushima nuclear accident is that once an accident has taken place and radioactive contamination of the environmental occurs, the world will no longer be one in which radioactive materials are controlled, the assumptions that had been in place up to that time will be destroyed, and the public’s exposure to radiation will gradually increase. Since the accident, the regulation of low-level radioactive materials has become illogically complicated (Table 3).
Table 3: Status of regulations on low-level radioactive materials since the Fukushima nuclear accident
When it was discovered last year that radioactive bricks (total cesium 341.45 Bq/kg) were brought into a quarry and crushed in Kasama City, Ibaraki Prefecture, the national government responded that the bricks were not subject to regulation under the Nuclear Reactor Regulation Act, the Act on the Regulation of Radioactive Isotopes, etc., or the Act on Special Measures Concerning Handling of Radioactive Pollution.13 Administrative control was no longer necessary, and it is unknown how the bricks were handled subsequently.
We are already living in a world where materials contaminated with radioactivity are moving around on a daily basis. If that is so, it should then go without saying that it is crucial that nuclear power plants are no longer operated and that accidents are not allowed to occur.
References:
1) Ministry of the Environment decontamination information website, (Handouts for the Okuma Residents Briefing on May 12 and 13, 2012)
2) Intermediate Storage and Environmental Safety Corporation Act (Act No. 44 of 2003)
3) Ministry of the Environment decontamination information website [as of the end of March 2024], Number of storage sites and amount of removed soil stored in priority contamination survey areas (outside Fukushima Prefecture)
4) Basic Policy for Promoting Recycling and Other Measures to Realize Final Disposal of Removed Soil in Fukushima Prefecture, May 27, 2025
5) Ministry of the Environment, Guidelines for Use in Reconstruction and Revitalization, March 2025
6) Ministry of the Environment, Waste Management and Recycling Department, Differences between the 100 Bq/kg and 8,000 Bq/kg Standards
7) Act on Special Measures Concerning Countermeasures against Environmental Pollution Caused by Radioactive Materials Released from the Nuclear Power Plant Accident following the Tohoku District Offshore Pacific Ocean Earthquake on March 11, 2011 (Abbreviated to “Special Act on Countermeasures to Pollution by Radioactive Materials”)
8) Current Approach to Ensuring the Safety of Waste Treatment and Disposal Affected by the Accident at TEPCO’s Fukushima Daiichi Nuclear Power Station,” June 3, 2011, Nuclear Safety Commission
9) Nuclear Safety Commission, Basic Concept of Radiation Protection for the Lifting of Evacuation Orders and Reconstruction, July 19, 2011
10) Radiation Council, Organization of the Basic Concepts of Radiation Protection: Response by the Radiation Council, January 2018, revised February 2022
11) Radiation Council, Concept of Radiation Protection in the Use of Removed Soil for Reconstruction and Revitalization after the Accident at TEPCO’s Fukushima Daiichi Nuclear Power Station – Views of the Radiation Council, February 27, 2025
12) ICRP Publ.146
13) Environmental Policy Department, Kasama City, Results of Confirmation of Regulations under Relevant Laws and Regulations Concerning Radiation Doses, etc. of Bricks Transported into City Quarry, December 25, 2024
