Exposure to Radiation During Regular Operations of Rokkasho Reprocessing Plant Nuke Info Tokyo No. 114
Quantity of Radioactivity Handled by Rokkasho Reprocessing Plant
The Rokkasho Reprocessing Plant commenced active tests on 31 March 2006, the last day of the 2005 fiscal year. Japan Nuclear Fuel Ltd (JNFL) wanted to start the tests during the 2005 fiscal year no matter what. As reported in NIT 113, for doing so it received 52.9 billion yen. Of course the fact that it took this step is a problem, given that it has irreversible consequences. Politics and the economy follow the logic of money. But perhaps an even more serious problem is that citizens get caught up in this logic.
The standard nuclear reactors these days are 1000 MW. Each year they burn 1,000 times the quantity of uranium that fissioned in the Hiroshima bomb and they produce a correspondingly larger quantity of fission products. The limit of radiation exposure permitted for members of the general public is set at 1 milli-sievert (milli-Sv) per year1(1,000 micro-sieverts (micro-Sv) per year). However, since people are exposed to radiation from many facilities, if an exposure of 1 milli-Sv were allowed from each facility, the level of exposure for each person would exceed the annual limit. Consequently a benchmark of 50 micro-Sv is set for each nuclear power plant2. Each year the Rokkasho Reprocessing Plant will handle 800 tons of spent nuclear fuel. This is equivalent to the amount of fuel reloaded each year into 30 reactors (see figure 1). The purpose of reprocessing is to extract the plutonium which has accumulated in the spent fuel. Whereas inside the reactor the plutonium and the fission products somehow or other manage to stay contained within the fuel rods, in the reprocessing plant the plutonium is chemically separated by cutting these fuel rods up into little pieces and dissolving them in nitric acid. Of course, the quantity of radioactivity released into the environment increases by orders of magnitude. It is said that the amount of radioactivity released in one day is equal to the amount released from a nuclear reactor in 1 year.
There are regulations governing the concentration of radioactivity that can be released from a nuclear power plant in both liquid and gaseous forms. For the reprocessing plant, in regard to gaseous releases, the diluting effect of the atmosphere is taken into account and the radioactivity concentration allowed outside the site boundary is the same as for nuclear power plants. However, if the limit for liquid tritium releases were set at the same level as for nuclear power plants3, every day the liquid releases would have to be diluted with 1 million tons of water. Consequently the concentration of radioactivity in liquid releases from the reprocessing plant is not regulated. Instead, the radiation dose to the public is calculated and it is considered to be sufficient if the calculated dose is below the regulated level4. JNFL and the government say that the calculated radiation dose to members of the public from the regular operation of the Rokkasho reprocessing plant will be just 22 micro-Sv per year5.
Calculation derived from assumptions on top of more assumptions
As shown in figure 2, the assessment of radiation dose starts from the quantity of radioactivity handled by the reprocessing plant. There are many intermediate steps in the assessment before a value for radiation dose is finally arrived at. By rights, the radiation effect should then be assessed, but Japan’s safety review does not go so far as to assess the radiation effect. Nevertheless, there are still many assumptions made along the way. Depending on the assumptions made, the results could be several times larger or several times smaller. In many cases the results could even vary by orders of magnitude. Naturally there is a big margin for error in the value which is finally derived. In JNFL’s submission to the safety review the calculated value is given to two significant figures, as if it had some kind of strict scientific validity. At best it is valid to just one significant figure. Giving it to two significant figures is unscientific in itself. By rights, the margin of error should be shown, with upper and lower limits.
Furthermore, the calculated value is not the maximum dose to members of the public. The assumptions which have been made in deriving this value are shown in the ellipses on the right hand side of figure 2. JNFL has not in all cases adopted the most conservative assumptions and, in some cases, its assumptions are very optimistic. For example, for consumption of seafood the biggest contributor to radiation dose is the iodine in seaweed. The concentration coefficient adopted between seawater and seaweed is 2,000. [This means that the concentration of radioactivity in seaweed is taken to be 2,000 times that of the surrounding seawater (ed.).] However, the coefficient used in safety reviews for nuclear power plants is 4,000. So the calculated dose for the reprocessing plant is underestimated by a factor of 2 compared to nuclear power plants (see assumption in ellipse 4).
In regard to the consumption of food, Aomori Prefecture’s assessment of the daily consumption of beef is 20 grams, whereas JNFL’s assessment is 6 grams (see assumption in ellipse 5). Obviously there are people who eat more beef than this, so on this point also, JNFL’s assumption does not represent the maximum value. In regard to the dose conversion coefficient, this has been amended many times over the years, at times by orders of magnitude. In some cases low conversion coefficients have been used in the dose assessment for the Rokkasho reprocessing plant. For example, in the latest regulations the dose conversion coefficient for oral consumption of Iodine-129 is 1.1 x 10-4 milli-Sv/Bq, whereas the coefficient used for Rokkasho is 4 x 10-5 milli-Sv/Bq. So here too the calculated dose is underestimated by a factor of 3 (see assumption in ellipse 6).
There is also a problem of a different nature. Reprocessing is a core nuclear military technology, which was developed in order to extract plutonium for nuclear weapons. As a loser country in World War 2, Japan was prohibited from nuclear research, so it was way behind European and North American countries in nuclear technology. Consequently, spent fuel from Japan’s nuclear reactors was sent to Windscale (also called Sellafield) in the UK and La Hague in France for reprocessing. Also Japan’s Tokai reprocessing facility was built by France. One would have expected Japan to build the Rokkasho reprocessing plant with its own technology by imitating and learning from the Tokai technology. However, in fact, once again Japan asked France to build the plant. One of the radioactive substances released from reprocessing plants is the volatile Ruthenium Oxide (RuO4). France and the UK have had lots of problems containing this substance and there have been many instances of environmental contamination. The quantity of Ru-106 released into the sea each year from France’s La Hague reprocessing plant, adjusted to scale based on the quantity of spent fuel reprocessed at Rokkasho, is 1 x 1013 Bq. However, the quantity of Ru-106 that will be released into the sea each year from Rokkasho, is said to be 2.4 x 1010 Bq. So apparently the Rokkasho reprocessing plant, which was built with French technology, will release 400 times less Ru-106 into the sea than the French have managed to achieve (see assumption in ellipse 2). If the quantity of Ru-106 released from Rokkasho turns out to be the same as that released from La Hague, the radiation dose from this substance alone through consumption of seafood works out to be about 13 micro-Sv per year.
Problems in the exposure scenario itself
In the assessment of radiation exposure from the Rokkasho reprocessing plant, it is assumed that radioactive releases from the exhaust stack will only have a radiological effect as gases and radioactive releases from the liquid release pipe will only have a radiological effect as liquids. However, some of the radioactivity released from the exhaust stack will fall into the sea and contaminate seafood, while some of the radioactivity released to sea will return to land. Radiological effects from the latter have already been observed in the environment around Windscale. Insoluble radioactive substances such as plutonium released as liquids from the liquid release pipe have contaminated the seabed. A portion of this has been blown back to land by the wind and has even been detected in the dust picked up by household vacuum cleaners6. When food containing plutonium is eaten, the majority of the plutonium is not absorbed into the body, so it doesn’t contribute much to radiation exposure. However, if plutonium is blown on the breeze and is breathed in, it lodges in the lungs and gives a very dangerous uneven exposure. This exposure pathway is not considered in the radiation exposure assessment for the Rokkasho reprocessing plant.
There is also another important problem. In the radiation exposure assessment for the Rokkasho reprocessing plant, it is assumed that the radioactive releases are dispersed evenly in the atmosphere and the sea and that they do not settle or accumulate anywhere. Consequently, it is assumed that the contamination caused by radioactive substances released in any one year does not contribute to radiation exposure beyond that year. However, among the radioactive materials handled at reprocessing plants are many long-lived trans-uranic elements. If these are once released into the environment, the contamination accumulates over a long period of time. Around the Windscale reprocessing plant, the contamination of seafood is not proportional to the radioactivity released in that particular year, but rather to the total radioactive releases until that year7. The radiation exposure assessment does not take this long-term accumulation of contamination into account. That fact alone is proof that the assessment is not in accord with reality.
The crime of a society in which everything is decided by economics
Reprocessing was developed under supreme order for military purposes. Operation was permitted no matter how uneconomic the plants were, or how much environmental contamination they caused. Japan’s Rokkasho reprocessing plant, which professes to be for peaceful purposes, was designed and will be operated with economics uppermost in mind.
Figure 3 shows the radioactivity that is expected to be released from the Rokkasho reprocessing plant during regular operations and the radiation dose that this will give rise to. The overwhelming majority is from aerial releases, with just 3 isotopes, Krypton-85, Tritium and Carbon-14, making up 70% of the total. JNFL intends to release all of these. It writes, “They cannot be filtered out…They will be released from a 150 meter exhaust stack, with a sufficient dispersion and dilution effect, and from a sea release pipe 3 kilometers out to sea and 44 meters deep.”5
However, the boiling point of krypton is minus 153oC. If it is cooled to that level, it can be liquefied and captured. A total of 3.3 x 1017 Bq of K-85 will be released from the Rokkasho reprocessing plant each year. That converts to a weight of just 23 kg. The government has already spent 16 billion yen on research and development into the capture of krypton, but that will all be money down the drain, because JNFL says it will release all the krypton into the environment. Regarding tritium, a portion of this will be released from the exhaust stack as saturated steam. However, JNFL itself calculates that the radiation dose from tritium released via the exhaust stack is 17 times that of the same quantity of tritium released to sea. It is easy to dehumidify the air released from the stack. Simply by releasing to sea the tritium captured in this way, the radiation dose could be greatly reduced. It would cost money, but technology for concentrating the tritium isotope is already established, so the only reason for not capturing tritium is cost. For C-14 also, the intention is to release the lot. It is possible to capture carbon by chemical processes. For example, it can be turned into a solid by reacting it with sodium hydroxide.
There is no safe level of radioactivity. “Sufficient dispersion and dilution” means spreading contamination over a large area. The K-85 that the Rokkasho reprocessing plant will release each year will contaminate the whole world and will give rise to a global radiation dose of 1,320 person sieverts8. If a cancer death ratio of 1 person per 10 person sieverts is applied, this works out to 130 cancer deaths each year. This represents 5,000 cancer deaths over the 40 years that the plant is expected to operate.
Operation of the Rokkasho reprocessing plant will expose the local people to a level of radiation that is unprecedented in their experience. The standard for “clearance” of radioactive waste is 10 micro-Sv/yr. The 22 micro-Sv/yr radiation dose calculated by the government and JNFL for Rokkasho is already greater than twice this clearance standard. Furthermore, by “dispersing and diluting” without capturing the radioactivity, the government and JNFL are spreading radioactive contamination on a global scale. I believe that by not adopting measures which ought to be adopted, just because they don’t want to pay the economic costs involved, they are committing a premeditated crime.
By Hiroaki Koide
(Kyoto University Research Reactor Institute)
References
1. A radiation exposure limit for the general public is not clearly specified in Japan’s regulations. However, this limit is specified for the boundaries of nuclear facilities.
2. Guidelines for assessment of dose benchmark for nuclear power plants with light water reactors.
3. Regulations for Establishment and Operation of Nuclear Power Reactors, Article 15, Clause 7
4. Regulations for Spent Fuel Reprocessing Business, Article 16, Clause 7
5. Japan Nuclear Fuel Ltd., Application for Establishment License for Rokkasho Reprocessing Plant
6. W.W. McKay & N.J. Pattenden, The Transfer of Radionuclides from Sea to Land via the Air: A review, J. Env. Radioact. 12 (1990) 49-77
7. Masayoshi Yamamoto, Behavior and Distribution of Long-lived Radionuclides in Seabed Sediment, Journal of the Society of Sea Water Science Japan, Vol. 57-3 (2003) 192-204.
8. Ian Fairlie, Estimated Radionuclide Releases and Collective Doses from the Rokkasho Reprocessing Facility, Greenpeace Japan, March 2006
