High-Level Radioactive Waste Disposal Policy in Japan: Comparison
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Please note this is a comparison between Version 2 by Beatrix Zheng and Version 1 by Yuichiro Amekawa.

The researchers comprehensively reviewed the fundamental policies and procedures formulated by the government concerning the high-level radioactive waste (HLW) disposal. The discussion encompasses an assessment of the Second Progress Report and concrete geological disposal methodologies. Additionally, the investigation delves into strategies for minimizing waste and procedures for selecting suitable sites for disposal repositories, including both local siting protocols and nationwide mapping approaches.

  • high-level radioactive waste
  • radioactive waste management
  • risk society
  • sociology of scientific knowledge
  • social acceptance
  • Japan

1. Second Progress Report

The Second Progress Report is a voluminous document comprising several volumes and supplementary material, totaling over 2400 pages. The report was developed with the primary objective of demonstrating the technical reliability of geological disposal in Japan. To achieve this, the JNC outlined a comprehensive goal of verifying the existence of rational and viable technologies for HLW disposal and demonstrating, on scientific grounds, that such technologies and an appropriate geological environment would ensure long-term safety. To this end, the report summarizes the outcomes of the three main research and development fields pursued by the JNC. First, it sought to identify critical geo-environmental conditions that are relevant to geological disposal by conducting a “research study on geological environmental conditions”. This information was used as input data for the design and assessment of the disposal site. Second, through “R&D of disposal technology”, the JNC aimed to examine the specifications of the artificial barrier and the layout of the disposal site, taking into account a wide range of geological environments in Japan, while demonstrating the engineering feasibility of geological disposal. Finally, the JNC aimed to ensure the long-term safety of geological disposal by conducting “performance evaluation research”. This research aimed to establish a method for evaluating a geological disposal system constructed based on specific geo-environmental conditions, population barrier specifications, and disposal site layouts [33][1].
The final chapter of the General Report presented an overview of the technical advances attained as a result of the comprehensive R&D endeavors. The report affirmed that the following foundations had been laid:
  • A geological environment that satisfied the prerequisites for the geological disposal concept existed extensively across Japan, and a novel approach was devised to appraise if a specific geological environment fulfilled these criteria.
  • Techniques were formulated to effectively design and construct artificial barriers and waste repositories that could adapt to diverse geological and environmental conditions.
  • A method was devised to predict the long-term safety of geological disposal, which was thoroughly verified for its safety and efficacy [33][1] (p. VII-3).
Before its submission, an international peer review of the English version of the report was conducted by the Nuclear Energy Agency (NEA) to ensure its rigor and quality [26][2]. The Ministry of International Trade and Industry (now known as the Ministry of Economy, Trade and Industry: METI) has boasted that the technical reliability of Japan’s geological disposal is guaranteed through a meticulous series of processes [24][3].

2. Geological Disposal Methods

A distinctive feature of HLW is the danger it poses to the human body because of the strong radioactivity it emits. Immediately after production, the vitrified material emits a staggering 1.5 million millisieverts of radiation per hour, equivalent to 150,000 X-ray CT scans, and has the potential to cause death within mere 20 s [34][4]. This high level of radioactivity is primarily caused by fission products (e.g., cerium-144, cesium-137, and strontium-90) contained in HLW that have relatively short half-lives of several decades. The radioactivity level of these fission products gradually decreases over time, with only one out of several thousand [8][5] or approximately 1/10,000 remaining after 1000 years from the vitrification process [34][4]. Subsequently, the low-level radioactivity of actinides such as plutonium and americium persists for an extended period [8][5]. It can take up to 100,000 years for the vitrified material to reach the same level of radioactivity as natural uranium ore [34][4]. As a result of its extended radioactivity, TRU waste is also planned to be geologically disposed of together with HLW [8][5].
The long-term effectiveness of the deep-burial disposal method depends on the stability of the stratum [35][6]. In Japan’s geological disposal program, HLW will be buried in an old stratum deeper than 300 m below ground, which has been carefully selected to avoid active faults and volcanic areas [3][7]. To ensure the safety of human populations for more than 100,000 years, a “multiple barrier system” has been designed, consisting of both “artificial” and “natural” barriers. The former involves enclosing the vitrified waste generated in the reprocessing process within a steel container called an “overpack”, which is approximately 20 cm thick, and then covering it with a layer of bentonite clay that is approximately 70 cm thick. The “natural barrier” simply refers to the bedrock and underground environment [36][8]. The vitrified HLW is stored in stainless-steel canisters, which are specifically engineered to confine radionuclides and prevent immediate dissolution upon contact with groundwater [5][9]. To further ensure long-term safety, the canisters are surrounded by an iron overpack, which acts as a shield against radiation and also serves to prevent any contact between the vitrified waste and groundwater. The overpack rusts over time, thereby creating a state of reduction in which radioactive elements become less soluble, further reducing the risk of radioactive release into the environment. As a material, clay bentonite is endowed with the ability to expand and fill gaps, fractures, and pores within the bedrock upon contact with groundwater, thus preventing further intrusion of water. Its clay composition offers an added advantage of adsorption, which can effectively suppress the diffusion of radionuclides in the event of leakage [36][8]. Nonetheless, in cases where radionuclides manage to escape beyond the bentonite layer, minerals within the bedrock will adsorb the radionuclides, and the slow movement of groundwater will limit their migration. Consequently, radionuclides carried by the groundwater will be gradually dispersed and diluted, thus averting any potentially hazardous outcomes [4][10].

3. Waste Reduction

The HLW remaining after the reprocessing of spent nuclear fuel comprises minor actinides (MA) and fission products (FP), which cannot undergo further reprocessing [37][11]. The term MA refers to a group of ten actinide elements with atomic numbers greater than that of uranium (U, atomic number 92) but does not include plutonium (Pu, atomic number 94). The MA group includes radioisotopes with half-lives ranging from thousands to millions of years, such as neptunium (Np-237 with a half-life of 2.14 million years), americium (Am-242 with a half-life of 7400 years), and curium (Cm-245 with a half-life of 8500 years). Some plutonium isotopes also possess long half-lives (e.g., Pu-239 with a half-life of 24,000 years, Pu-240 with a half-life of 6500 years, and Pu-242 with a half-life of 380,000 years). The process of reducing the long-term hazards of long-lived transuranic elements by fissioning these MAs in nuclear reactors is known as nuclear transmutation. Plutonium has been the only transuranic element to be extensively recovered from spent fuel and utilized as a resource [38][12]. The R&D of nuclear transmutation presents a vital challenge for the disposal of HLW, as its practical implementation could significantly decrease the management period of HLW [35][6]. Furthermore, proponents of transmutation argue that it could reduce the quantity of waste sent to geological repositories by as much as 1/100th of the amount that would be produced by the direct disposal of spent fuel. Nonetheless, a report issued by the US National Academy of Sciences in 1996 suggests that removing 99.5% of the sludge could take at least 150 to 200 years, even with the use of many fast reactors, and thousands of years if light–water reactors are employed [39][13]. Certain experts in Japan hold a pessimistic view regarding the feasibility of transmutation, considering the limited success of fast reactor development in Japan and other countries. For instance, Professor Emeritus Shibata [35][6], a renowned radiation scientist at the University of Tokyo, expressed doubts regarding the viability of this technology by stating, “Although I do not deny that the technology to convert ultra-long-lived nuclides in radioactive waste into short-lived nuclides has some room for future research, I do not think it promising” (p. 129).

4. Geological Disposal Siting

4.1. Local Siting Procedure

Upon its establishment, the NUMO recognized the critical importance of acquiring candidate disposal sites through the voluntary application of local communities, in order to advance the project in a seamless and productive manner. In view of this, the NUMO adopted an open recruitment system to ensure transparency and fairness in the selection process [3][7].
According to NUMO documents, landfill site selection proceeds in three stages (Figure 1). First, upon receiving an application from the mayor of a township, the NUMO conducts a survey using various resources, such as ancient writings, historical records of past natural disasters (e.g., earthquakes, tsunamis, and volcanic activity), and the intentions of the concerned municipality and prefecture. This preliminary phase is referred to as a literature survey. Following this, if the results of the survey show no signs of concern and the consent of the relevant governments is obtained, the area is deemed a “preliminary survey site”. In the subsequent “outline survey”, further investigations such as drilling and bowling are conducted to verify the underlying geological conditions. Based on the findings from the outline survey, the intentions of the concerned local governments are confirmed, and areas that pass this stage are selected as “detailed survey sites”, where research facilities are constructed underground for detailed geological investigations. If no issues are identified, and the intentions of the relevant local governments are confirmed, the area is selected as the final disposal construction site [40][14].
/media/item_content/202305/646d604f35d42sustainability-15-07732-g001.png
Figure 1. The selection process of HLW disposal site. Source: modified from [19].
The selection process of HLW disposal site. Source: modified from [15].
In December 2002, a public call for proposals was initiated to select a preliminary survey area to identify a geological disposal site. According to the call for proposals, a literature survey of the application area was supposed to be conducted and an outline survey area selected by 2008, following which the construction of the final disposal site was planned to commence around 2028, and the final disposal was set to commence in 2038 [41][16].

4.2. Nationwide Map

After deliberations by the Radioactive Waste Working Group (“Waste WG”) in May 2015, the METI revised the Basic Policy on Final Disposal of Specified Radioactive Waste (Cabinet decision). During this process, the national government proclaimed that it would “stand at the forefront” in the selection of the NUMO’s general survey area, and identified scientifically promising areas that were highly evaluated as being scientifically suitable. By doing so, the government sought to gain the understanding and cooperation of the national population and local residents and made a request to the relevant local governments to consider HLW disposal in their areas [42][17]. As a response, in April 2017, the Geological Disposal Technology Working Group (“Technology WG”) compiled the requirements and standards for presenting the scientific characteristics of the region, and in July 2017, the Agency for Natural Resources and Energy of the METI released the Nationwide Map of Scientific Features for Geological Disposal (“Nationwide Map”) [30][18]. Since then, the NUMO has conducted geological disposal briefing sessions throughout Japan using detailed materials based on the map [34][4].
The Nationwide Map, with a scale of 1/2,000,000, classifies Japan’s entire region into four groups:
(a)
Areas assumed to have unfavorable characteristics concerning long-term stability deep underground (orange);
(b)
Areas estimated to have unfavorable properties regarding future drillability (silver);
(c)
Areas with a relatively high probability of confirming favorable characteristics (green);
(d)
Areas among (c) that are also advantageous in terms of waste transportation (dark green) [43][19] (Figure 2).
/media/item_content/202305/646d607881674sustainability-15-07732-g002.png
Figure 2. Scientific Nationwide Map. Source: [44].
Scientific Nationwide Map. Source: [20].
The map eliminates unfavorable regions that meet eight requirements, such as areas containing active faults, volcanoes, or mineral resources. Furthermore, coastal areas situated within 20 km of the coast, which make it easier to transport nuclear waste from storage facilities, were deemed preferable areas (Table 1). Consequently, of the approximately 1750 municipalities in Japan, approximately 900 were identified as areas with a high possibility of safe disposal [44][20].
Table 1.
Requirements and Criteria for Scientific Characterization Maps.
Requirements/Criteria for Unfavorable Areas
  Requirements Criteria
Volcano/

Pyrogenesis The surrounding areas of volcanoes (preventing magma from penetrating the repository) Within 15 km radius from the center of the volcano
Fault activity Areas where the impact of active faults is large (preventing destruction of disposal sites related to a fault slip) Within a certain distance (fault length × 0.01) on both sides of a major active fault (fault length of 10 km or more)
Uplift/erosion Areas where large erosion is expected to occur in the future due to the upliftment and lowering of the sea level (preventing disposal sites from approaching the ground surface) A coastal area with a large amount of upliftment in the past, with the possibility of uplift exceeding 300 m in 100,000 years
Geothermal activity Areas with strong geothermal heat (preventing functional deterioration of artificial barriers) Geothermal gradient greater than 15 °C/100 m
Volcanic hot water/deep fluid Areas with highly acidic groundwater (preventing functional deterioration of artificial barriers) pH 4.8, etc.
Soft ground Areas where the landfill stratum is soft (preventing collapse accidents of underground facilities during construction and operation) The stratum from about 780,000 years ago is distributed deeper than 300 m
Effects of pyroclastic flows, etc. Places where pyroclastic flows can reach (preventing destruction of ground facilities during construction and start-up) Pyroclastic flows from about 10,000 years ago are distributed
Mineral resources Areas where mineral resources are distributed (preventing human intrusion associated with resource mining) Rich in coal, petroleum, natural gas, and metallic minerals
Requirements/Criteria for Desirable Range
  Requirements Criteria
Shipping Areas where surface transport from the coast is easy Approximate distance of within 20 km from the coast
Source: [43][19].

References

  1. Japan Nuclear Cycle Development Institute. Technical Reliability of Geological Disposal of High-Level Radioactive Waste in Japan: Second Report on Geological Disposal Research and Development, General Report. 1999. Available online: https://www.jaea.go.jp/04/tisou/houkokusyo/dai2jitorimatome_so.html (accessed on 10 March 2023). (In Japanese).
  2. Takeuchi, M.R.H.; Hasegawa, T.; McKinley, L.; Marquez, G.P.; Ishihara, K.N. What is suitable leadership for high-level radioactive waste (HLW) management? Sustainability 2020, 12, 8691.
  3. Matsuoka, S. Back-end problems in nuclear policy and scientifically promising areas. Asia Pac. Stud. 2017, 8, 25–44. (In Japanese)
  4. Kogi, K. Nuclear Waste: Can Geological Disposal Ensure Safety for 100,000 Years? Godo Shuppan Publishers: Tokyo, Japan, 2021. (In Japanese)
  5. Ishikawa, H. The basic concept and current status of high-level radioactive waste disposal. Zairyo-to-Kankyo 1996, 45, 487–494. (In Japanese)
  6. Shibata, T. Questions and opinions from the audience and how to proceed with final disposal of high-level radioactive waste. In Final Disposal of High-Level Radioactive Waste; Japan Science Support Foundation, Ed.; Kitajima Publishers: Tokyo, Japan, 2014; pp. 41–57. (In Japanese)
  7. Takeda, S. Regarding high-level radioactive waste: Focusing on long-term stability in geological environment. In Final Disposal of High-Level Radioactive Waste; Japan Science Support Foundation, Ed.; Kitajima Publishers: Tokyo, Japan, 2014; pp. 41–57. (In Japanese)
  8. Yoshida, E. Geological Disposal: Scientific Issues Remaining after Phase-Out of Nuclear Power; Kinmiraisha Publishers: Nagoya, Japan, 2021. (In Japanese)
  9. Fujimura, Y. Geological disposal of high-level radioactive waste. Science 2007, 77, 1133–1140. (In Japanese)
  10. Masuda, S.; Umeki, H.; Naito, M. Technical reliability on geological disposal of HLW in Japan. J. Nucl. Sci. Technol. 2000, 42, 486–505. (In Japanese)
  11. Silverio, L.B.; de Lamas, W.Q. An analysis of development and research on spent nuclear fuel reprocessing. Energy Policy 2011, 39, 281–289.
  12. IPFM (Ed.) Chapter 10. Transmutation. In Plutonium Separation in Nuclear Power Programs: Volume Reduction, Problems and Future Challenges for Civil Reprocessing in the World; Princeton University’s Program on Science and Global Security: Princeton, NJ, USA, 2015; pp. 1–10. Available online: https://fissilematerials.org/library/rr14.pdf (accessed on 14 November 2022). (In Japanese)
  13. National Research Council. Nuclear Wastes: Technologies for Separations and Transmutation. 1996. Available online: https://nap.nationalacademies.org/catalog/4912/nuclear-wastes-technologies-for-separations-and-transmutation (accessed on 1 March 2023).
  14. Sugawara, S.; Juraku, K. Scientific, technological and sociological considerations on the site location process of high-level radioactive waste final disposal sites: “Lessons” learned from nuclear power plant location issues and system design “failures”. Sci. Technol. Soc. 2010, 19, 25–51. (In Japanese)
  15. Wada, R.; Tanaka, S.; Nagasaki, S. Social acceptance process model for ensuring the high-level radioactive waste disposal site. J. Nucl. Sci. Technol. 2009, 8, 19–33. (In Japanese)
  16. Kono, T. Problems of Japan’s nuclear fuel cycle. J. Nucl. Sci. Technol. 2012, 54, 342–345. (In Japanese)
  17. METI. Basic Policy on the Final Disposal of Specific Radioactive Waste. 2015. Available online: https://www.meti.go.jp/shingikai/enecho/denryoku_gas/genshiryoku/pdf/012_s03_00.pdf (accessed on 8 December 2022). (In Japanese).
  18. Yamada, M.; Choi, Y.; Matsuoka, S. Analysis of social acceptance factors on the high-level radioactive waste (HLW): Empirical public communication on deficit model. Environ. Inform. Sci. 2019, 33, 175–180. (In Japanese)
  19. Agency for Natural Resources and Energy. Scientific Characteristics Map. 2017. Available online: https://www.enecho.meti.go.jp/category/electricity_and_gas/nuclear/rw/kagakutekitokuseimap/maps/kagakutekitokuseimap.pdf (accessed on 18 December 2022). (In Japanese).
  20. Nikkei. Thirty Percent of the Land Area for 900 Local Governments that Have “Suitable Land”―For Nuclear Waste Final Disposal Sites. 2017. Available online: https://www.nikkei.com/article/DGXLASGG28H1D_Y7A720C1000000/ (accessed on 30 November 2021). (In Japanese).
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