1 Exploring New Paradigm of Nuclear Safety: From Accident Mitigation to Resilient Society Facing Extreme Situations Joonhong Ahn Department of Nuclear Engineering, University of California, Berkeley, Berkeley, California USA ABSTRACT Observing current situations in Japan after the Fukushima Daiichi accident on different scales, I discuss resilience in nuclear utilization as a new paradigm of nuclear safety. On the local-community scale, due to lack of understanding on radioactivity contamination in the environment, effective decontamination actions have not been taken. The difficulty has been compounded by the lack of effective stakeholder engagement in decision-making process in the decontamination actions. On the national and international scales, due to lack of flexibility in back-end of the fuel cycle and reactor decommissioning, resilience of a nation's reactor fleet has been significantly limited, resulting in increase in various potential risks. Nationalscale resilience is deeply coupled with the community-scale resilience because the trust toward nuclear technology is based on the public's trust in the 5th level defense, i.e., how resilient the society can be in aftermath of a severe accident. Thus, experts of natural and social sciences and engineering must discuss resilience as a new paradigm of nuclear safety at multiple scales and levels. Key words: Local-community scale, National scale, Resilience of nuclear utilization INTRODUCTION The consequences of the Fukushima Daiichi nuclear accident in March 2011 sparked a debate about the nuclear safety. Most directly, the impact on local communities is substantial and manifold, including as of March 2015 more than 100,000 citizens who are still evacuated from their homes and nearly 2,000 deaths during the evacuation and living in temporary housing as a result of various causes triggered by the evacuation, while releases of large amounts of radioactive materials resulted in no casualties due to radiation. In addition, thousands of families, local communities, and industries were damaged or completely destroyed. On a national and international scale, Japan is experiencing complicated situations in international relations and economics, as its nuclear policy started to stray after the accident. These consequences should have been recognized, analyzed, discussed in public, and prepared for prior to the accident, but there had been serious oversight and misunderstanding about what harms must be protected against in such a severe accident. This insufficient preparedness has been compounded by the lack of an effective decision-making process with participation from a broad range of stakeholders on local-community scale and national scale, resulting in intolerable delays in societal recovery after the accident. Numerous cases can be found on various scales in which decisions led to greater damage due to lack of timely decision-making informed by solid scientific evaluation of various risks. These challenges are compounded by the eroded public trust for government and operators. The bitter reality is that severe nuclear accidents will occur in the future, no matter how advanced nuclear technologies become; we just do not know when, where, and how they will occur. Technologies for reactors and nuclear fuel cycles should continue to be improved to minimize the frequency and consequences of accidents in the conventional context of Level 1 to 4 in the defensein-depth concept, as well as in the Level-5 defense. Scientific and academic communities should start efforts for establishing the scientific bases, both natural and social, for better societal resilience. In this paper, I try to describe difficulties that Japan has been experiencing in the aftermath of the Fukushima Daiichi accident on different scales. ON LOCAL-COMMUNITY SCALE The Model Fig. 1 shows the parts of Japan that were affected by fallout of Cs-134 and Cs-137 from the Fukushima Daiichi nuclear power plant. For this situation, the Japanese government enacted a law on special 1 Fig. 1: The level of the surface radioactivity concentration (kbq/m2) in September 2011.
2 measures on August 30, 2011 . It stated that (1) the annual dose is to be made less than 20 msv/year within 2 years, and (2) 1 msv/year or lower at any location in the long term. In Fig. 1, the surface concentrations of cesium in the yellow and red regions exceed the 1,000 kbq/m 2 level, in which case, as the calculation in  illustrates, annual doses exceed the 20 msv/year level. This fact indicates that efforts to reduce the surface concentration of cesium should be focused in these regions to achieve the first guideline. To achieve the second guideline requires decontamination of a much broader area. With the proportionality between the surface concentration and the annual dose, the target area of decontamination would be all places with a surface contamination greater than 50 kbq/m 2. With the two decontamination guidelines defined by the law, questions arise immediately as to how soon these goals can actually be achieved, how much it will cost, and what the parameters are that could significantly affect effectiveness of a decontamination job. To help answer these questions, an abstracted model was developed by taking into account three major mechanisms that would affect the surface radioactivity concentration: (1) spontaneous radioactive decay, (2) natural dispersion, and (3) decontamination by human actions. The reader is referred to  for further details. Results Table 1 shows the results for four cases as combinations of with or without decontamination and slow or fast natural dispersion. Answers to the questions addressed in relation to the two goals defined in the law can be obtained as follows: (1) Can the annual dose be made smaller than 20 msv/year within 2 years? The dose rate exceeds 20 msv/year if the initial contamination was 1,000 kbq/m 2 or higher. Table 1 indicates that for the area with 1,000 to 3,000 kbq/m 2 contamination, the dose rate would become below 20 msv/year within at most 2.52 years. For the area with > 3,000 kbq/m 2, the time for the dose to become below 20 msv/year is longer than that, but decontamination action can effectively shorten the time, particularly where the natural dispersion is slow. If the natural dispersion is fast, effects of decontamination on shortening the time to lower the dose rate below 20 msv/year are limited. Thus, decontamination should be applied only in such areas where natural dispersion occurs slowly for the purpose of minimizing waste generation by decontamination. (2) How long will it take for annual doses to become 1 msv/year or lower at any location? For the area with the initial contamination < 100 kbq/m 2, in any conditions of natural dispersion, within at most 1.66 years the dose rate becomes below 1 msv/year. Actually in this area in the past four years the < 1-mSv/year radiation level has been achieved. Between 100 and 1,000 kbq/m 2, if natural dispersion is fast, then decontamination should not be applied because the time for the dose rate to become below 1 msv/year would not shorten significantly. Thus, similar to the observation for Question (1), it is crucial to identify regions where natural dispersion occurs slowly. Decontamination generates waste materials containing radioactive cesium. From the aforementioned observation, we consider that decontamination should be applied only in the region with the initial contamination of 300 kbq/m 2 or greater. In Table 2, the area for each contamination level is shown in the second column from the left. In-situ measurements for soil contamination  indicate cesium has migrated into the soil to a depth of about 5 cm. Assuming that the contaminated materials are removed from the area to a depth of 5 cm, we can estimate the volume of the radioactive waste to be generated by decontamination activities. The third and fourth columns of Table 2 show results of the waste volume estimate for the cases of fast and slow natural dispersion by the model shown in . 16 or 24 million m 3 of waste will be generated from decontamination for regions with 1000 kbq/m 2 or greater (the yellow and red regions in Fig. 1). But if decontamination is applied to regions with lower contamination levels, the total volume of radioactive waste generated could be as large as 37 or 58 million m 3. The two rightmost columns in Table 2 show the estimated cost. Depending on the area targeted for decontamination, the cost of decontamination varies greatly. Even if decontamination is limited to highly contaminated areas where the dose rate is above 20 msv/year, the cost is likely to be on the order of ten trillion yen. Table 1 Effects of decontamination and natural dispersion (Fast: natural dispersion rate = yr -1 ; Slow: 0.05 yr -1 ; -- : air dose rates always below 20mSv/yr) Initial Years to reach 20 msv/yr contamination, No With β (kbq/m 2 ) decontamination decontamination Years to reach 1 msv/yr No decontamination With decontamination Fast Slow Fast Slow Fast Slow Fast Slow > 3000 >1.43 >4.32 >1.10 >2.19 >5.67 >38.4 >4.25 >
3 Table 2 Evaluation of Volume and Cost of Disposal for Radioactive Waste Arising from Decontamination Initial soil Area contamination, included β (kbq/m 2 ) (km 2 ) Waste volume (million m 3 ) Estimated cost (trillion yen) Fast dispersion Slow dispersion Fast dispersion Slow dispersion > 3, ,000 3, Subtotal , Subtotal 1, Total 1, Observations and Suggestions The result indicates the importance of waste volume reduction, for which basically two approaches can be considered. The first is strategic selection of areas for decontamination. Decontamination has been found to effectively reduce the air dose rate if it is applied in areas where natural dispersion is slow. The second is development of volume reduction technologies, which include incineration, physical and chemical partitioning, and compaction. Both approaches should be applied in a concerted manner. Unfortunately, sufficient scientific information and knowledge that enable strategic prioritization of areas for decontamination are not currently available. From the present analysis, these are primarily related to in-depth understanding about natural dispersion phenomena, including (1) the interaction of radionuclides with materials in the natural environment, (2) the transport and dispersion of radionuclides in the natural environment, and (3) the measurement of radiation and radionuclides in the environment. Furthermore, effectiveness of decontamination should have been evaluated through experiences in actual decontamination work. In the past four years, although decontamination has been carried out in more than 100 local municipalities, data, experience, and knowledge have not been made available in the public domain in forms that can be utilized for further analyses and feedback. This lack of integrated scientific knowledge base about environmental contamination caused deterioration in trust among stakeholders in society. But, at the same time, knowledge and information about natural dispersion phenomena and decontamination effects could not be accumulated and fed back due to the lack of trust. What has actually occurred in the past three years indicates that the issue of decontamination has sensitized differences among people about what needs to be achieved by decontamination, resulting in belated decision making on various important matters, which has led to greater and prolonged hardship for the evacuees. To halt this vicious cycle, we need to establish a fundamental scientific basis, both natural and social, for enabling indepth analysis about what has been the most crucial damage resulting from the accident and why that occurred, and how radiological risk can or should be compared with other risks in society. Coupled with such scientific efforts, advanced concepts and technologies should be developed and implemented to facilitate decision making by a broad range of stakeholders, which would significantly enhance the resilience of society. ON NATIONAL AND INTERNATIONAL SCALES Status Quo In the past fifty years of nuclear power utilization in Japan, 25,640 metric ton (MT) of spent nuclear fuel 1 has been generated. Of this amount, 7,100 MT was reprocessed in France and U.K., and the plant in Tokai-mura currently owned by Japan Atomic Energy Agency (JAEA) reprocessed 1,020 MT (Table 3). As a result, Japan possesses approximately 44 MT of plutonium (Pu) (Table 4) and about 8,000 canisters of HLW. The un-reprocessed spent fuel (25,640 1,020 7,100 = 17,520 MT) is stored either at each nuclear power plant in Japan (total 14,170 MT) or in the storage facility attached to the Rokkasho reprocessing plant (3,350 MT). 14,170 MT occupies approximately 70% of total storage capacity (20,000 MT) in 1 Nuclear fuel before usage in a contemporary light-water reactor (LWR) is made of uranium oxide (UOX) consisting of the fissile U-235 isotope comprising 4.5% of total U atoms. After producing 45,000 mega-watt-days of heat per metric ton (MWd/MT), the fuel is discharged from the reactor. This spent fuel still contains around 0.8 % of U-235 and 0.9 % of Pu (approximately 9 kg), of which about 0.5 % (5 kg) is fissile. If one MT of spent fuel is reprocessed, 9 kg of Pu and approximately 960 kg of U are recovered separately, and the rest becomes vitrified high-level waste (HLW), including fission-product isotopes and minor actinide isotopes, such as neptunium, americium, and curium. The HLW is solidified with borosilicate glass in a stainless steel canister. 3
4 all existing nuclear power plant sites. 3,350 MT is already 97% of the spent fuel storage capacity at the Rokkasho reprocessing plant. How Has This Status Quo Been Generated? Table 3 Japan s Spent Fuel Balance (02/2013) Stored at JNFL in Rokkasho 3,350 MT Stored at nuclear power plants 14,170 MT Reprocessed in U.K. and France 7,100 MT Reprocessed at Tokai-mura 1,020 MT Total 25,640 MT Table 4 Japanese Plutonium Stockpile (kg) (as of the end of 2011) in Japan (Pu fissile) 9,295 (6,316) Reprocessing Plants 4,364 MOX Fuel Plant 3,363 Stored at Reactors 1,568 in Europe (Pu fissile) 34,959(23,308) U.K. 17,028 France 17,931 Total (Pu fissile) 44,254(31,837) In 1955, ten years after the end of World War II, Japan established the Atomic Energy Basic Law, and launched its nuclear development program. The Japanese national policy for nuclear fuel cycle was established during the 1970s and 1980s to achieve energy independence by decreasing dependence on oil, motivated by the experience of the oil crises in 1973 and The establishment of the nuclear fuel cycle, consisting of uranium (U) enrichment, reprocessing of spent nuclear fuel to recover Pu and U, and a fast breeder reactor (FBR), became the national policy with the highest priority. In 1988, Japan successfully reached a comprehensive Nuclear Cooperation Agreement (NCA) with the United States that enabled Japan to develop and own the nuclear fuel cycle. It was a remarkable diplomatic achievement in the international environment after the nuclear test by India in 1974, upon which the U.S. strengthened its anti-nuclear fuel cycle policy. Indeed, Japan is the only non nuclear weapons country other than EURATOM that has industrial-scale capability of U enrichment, PUREX reprocessing, and FBRs, acknowledged by the international community, particularly by the U.S. After reaching the U.S.-Japan NCA in 1988, Japan made steady progress toward construction of nuclear fuel cycle facilities in 1990s. After the 1997 Kyoto Protocol ratified at the United Nations Framework Convention on Climate Change (UNFCCC), reduction of greenhouse-gas emissions was added as the main objective of nuclear power utilization. In other words, the 1997 Kyoto Protocol solidified the raison d etre of Japan s nuclear energy industry, and this was the mindset in place until the Fukushima Daiichi accident on March 11, The Japanese nuclear community had never conceived of sudden braking scenario as the situation currently observed in Japan that all reactors halted operation after the Fukushima Daiichi accident. The sudden braking clearly revealed that there was a serious oversight, or lack of plan B, in the national policy for development of the nuclear fuel cycle and for spent fuel management. What Are the Problems with the Current Situation? After March 11, 2011, all forty-eight operable nuclear reactors in Japan had been put out of service one after another due to previously scheduled regular maintenance and inspection, and none could resume operations except for the Number 3 and 4 reactors at Kansai Electric s Oi Nuclear Power Station for the term between July 2012 and September While the two units at Oi could restart for a year as an emergency measure, 2 others could not, because more stringent regulations implemented after the accident require all existing 48 reactors to be back-fitted before they obtain permission to restart. Aged reactors in general need more work to comply with new regulations, which creates higher costs, but investing in aged reactors may not pay off if the remaining license term is not long enough. This is currently urging utilities companies to consider decommissioning their aged reactors, and thus almost certainly the total number of Japanese nuclear reactors will be reduced in the future. What is not so clear at this moment is how fast the reduction process will occur, and at what capacity the Japanese nuclear fleet size will level off. The Japanese monthly trade statistics  indicate that Japan s import of natural gas and oil increased significantly after the accident to fill the gap created by loss of the nuclear reactor fleet. Japan has to spend an extra 4 to 5 trillion yen every year. In addition, burning oil and gas emits carbon dioxide into the atmosphere. In 2011, Japan emitted an extra 175 million ton of carbon dioxide compared to the average annual emission before the accident. This pattern will continue as long as Japan relies fully on fossil fuels. 2 Prime Minister Noda expressed his support for the restarting of Oi s two reactors on June 8, 2012, driven by the projection that the Kansai area, including Osaka, Kyoto, and Kobe, would otherwise suffer from a severe electricity shortage in the coming summer. 4
5 When Aomori Prefecture agreed in 1989 to build in Rokkasho the reprocessing plant and attached interim storage facilities for spent fuel and HLW canisters, the central government promised that Rokkasho would never be the final disposal site for HLW. After the accident, in the course of public discussions about whether nuclear power utilization should be continued or phased out and whether reprocessing should be carried out or abandoned, Aomori Prefecture warned that all spent fuel and HLW canisters currently stored in the Rokkasho site must be returned back to their original plants if reprocessing is not carried out in Rokkasho. In this case, 3,350 MT of spent fuel stored currently in Rokkasho and 8,000 canisters of HLW to be returned from U.K. and France would need to be relocated from Rokkasho. In October 2013, in Mutsu city, Aomori, the interim storage facility for spent fuel became available first with a 3,000 MT capacity with a planned expansion to 5,000 MT in the future. Considering that the fleet size is likely to be significantly reduced, and that there is a total of approximately 10,000 MT (6,000 in individual power plant sites and 3,000 to 5,000 in Mutsu) of available space for spent fuel storage, Japan can restart reactors for a decade or longer while postponing decision on reprocessing. This offers Japan an invaluable grace period to review policy, during which time a plan must be developed for the medium- and long-term range. The United States has been demanding that Japan make clear its plans for commercial Pu utilization to avoid creating a large Pu stockpile. However, with the onset of delays in the development of FBR technologies, the Atomic Energy Commission and utilities companies decided to introduce utilization of Pu in the form of mixed oxide (MOX) fuel with existing LWRs. 44 MT of separated Pu can be made into approximately 640 MT of MOX fuel at the MOX fuel fabrication plant to be commissioned in 2017 at JNFL s Rokkasho site with production capacity of 130 MT/year. Thus, if LWRs can be restarted, the Pu stockpile can be burnt in LWRs in the form of MOX. Assurance of timely Pu consumption by MOX utilization will be helpful for the Rokkasho reprocessing plant to commence its operation. However, if an immediate nuclear phase-out is chosen, this MOX option for dealing with the Pu stockpile would no longer be viable. Without establishing a complete fuel cycle with FBR, geological disposal becomes more complicated. Before the accident, the policy was to reprocess all spent nuclear fuel and to utilize separated Pu as MOX first for LWRs, but eventually for FBRs. If FBRs are deployed, the resultant wastes that require deep geological disposal are HLW and intermediate-level waste (so-called TRU waste) from reprocessing. Because only trace amounts of weapons-usable materials, such as Pu, are included in HLW or TRU, the International Atomic Energy Agency (IAEA) would terminate its safeguards inspection for a disposal facility for these two types of waste. But, if a repository is for disposal of spent fuel (either MOX or UOX), separated Pu and U, IAEA will not terminate its safeguards inspection in perpetuity. In addition to safeguardability issues, a geological repository for spent fuels can potentially be a greater radiological risk than that for HLW and TRU. These issues, i.e., (1) Aomori Prefecture s refusal to store HLW and spent fuel in Rokkasho without a plan for them to be taken out to a permanent geological repository, (2) drainage of national wealth for purchasing additional oil and gas, (3) international pressure on Japan not to have an unnecessary Pu stockpile, and (4) perpetual safeguards inspection and higher potential radiological risk to be imposed on a final repository for spent fuel and separated Pu and U, are coupled to each other, creating a deadlocked situation after the accident. If reactors are back in operation and reprocessing is conducted at Rokkasho, aforementioned issues (1), (2), and (3) could be solved, but the resultant repository would require high maintenance for a long-term period. Public agreement on this scenario seems to be very difficult to reach under the current situation. If reactors restart but reprocessing is abandoned, (2) and (3) could be solved, while (1) and (4) remain unsolved. If reactors and reprocessing are decommissioned, all four issues remain unsolved, while public support for this option may be the greatest. CONCLUSIONS On the local-community scale, we recognize that the lack of integrated scientific knowledge base about environmental contamination caused deterioration in trust among stakeholders in society. But, at the same time, knowledge and information about natural dispersion phenomena and decontamination effects could not be accumulated and fed back due to the lack of trust. It is essentially important for various stakeholders to share common understanding on what primarily needs to be protected in a severe accident, and to have confidence that such understanding is supported by science (natural and social). From the natural science and engineering, in the level-5 defense, these are primarily in-depth understanding about natural dispersion phenomena, including (1) the interaction of radionuclides with materials in the natural environment, (2) the transport and dispersion of radionuclides in the natural environment, and (3) the measurement of radiation and radionuclides in the environment. Improvement in reactor technologies can contribute to Level 1-4 defense, and ultimately to Level 5 by minimizing the area affected by a severe accident. On the national and international scale, resilience and flexibility need to be enhanced in a nation's fleet of nuclear reactors. Financial and technological barriers for reactor decommissioning are currently so high that reactor owners and the government cannot make timely decisions in fast-evolving environment. Spent fuel accumulation, inter alia, plutonium stockpile, is another crucial factor that reduces flexibility or variety of options that a country can take. Difficulty in getting public agreement is another factor that makes nuclear utilization less resilient and flexible. Considering that the difficulty in public agreement results from fear of severe accidents and lack of effective measures in aftermath of severe accidents, this 5
6 national and international scale resilience is deeply coupled with the local-community scale resilience, which has been observed in the previous paragraph. Thus, resilience as a new paradigm of nuclear safety must be discussed at multiple scales and levels by experts of natural and social sciences and engineering. REFERENCES  Act on Special Measures concerning the Handling of Environment Pollution by Radioactive Materials Discharged by the Nuclear Power Station Accident Associated with the Tohoku District Off the Pacific Ocean Earthquake that Occurred on March 11, 2011 enacted on August 30, 2011 by the National Diet of Japan. Available at: (in Japanese).  Joonhong Ahn, Chapter 4: Environmental Contamination and Decontamination after Fukushima DaiichiAccident. In: Joonhong Ahn, Cathryn Carson, Mikael Jensen, Kohta Juraku, Shinya Nagasaki, Satoru Tanaka (Eds) "Reflections on the Fukushima Daiichi Nuclear Accident: Toward Social-Scientific Literacy and Engineering Resilience," ISBN: (Print) (Online)  Shiozawa S (2013) Vertical migration of radiocesium fallout in soil in Fukushima. In: Nakanishi TM, Tanoi K (eds) Agricultural implications of the Fukushima nuclear accident. Springer Japan. ISBN: (Print) (Online)  Cabinet Secretariat, Japanese Government (11 Sep 2012) Status of plutonium management. Handout No. 2 distributed at the 39 th meeting of Atomic Energy Commission. Available at: Accessed 20 July 2014 (in Japanese)  Ministry of Finance, Japanese Government (n.d.) Trade statistics of Japan. Available at: Accessed 20 July 2014  Ministry of Economy, Trade and Industry, Japanese Government (2014) Statistics on resources and energy. Available at: Accessed 20 July 2014 (in Japanese) 6