Project to measure radioactivity released from Rokkasho Nuke Info Tokyo No. 111

1. Objective
It is impossible to operate the Rokkasho reprocessing plant without discharging radioactivity with the liquid and gaseous wastes. It is, therefore, important for citizens to have information that they can trust about the pollution released into the surrounding environmental. There is a danger that agricultural produce will be radioactively contaminated in the course of the plant’s normal operations, so it is essential to analyze the nature of the radioactive pollution and highlight it as a social issue. For this, it is necessary to obtain environmental data before the plant begins operations. We intend to measure radioactive isotopes which are emitted in the course of normal operations, in particular the beta emitters tritium and carbon-14.

Sampling of pine needles and beach sand for testing
(Photos by Shigeru Ogasawara)

2. Operation of Rokkasho and radioactive pollution
Active tests are scheduled to be carried out from March or April 2006 to July 2007. During the course of these tests, it is planned that 430 tons of spent nuclear fuel will be reprocessed. During the active test phase, the plant will at times operate much the same as it will after commercial operations officially commence. Once reprocessing begins, volatile isotopes such as tritium, carbon-14, krypton-85 and iodine-129 will be released into the atmosphere and all sorts of isotopes, including cesium-137, strontium-90 and plutonium, will be released from the liquid waste pipe.

There are benchmarks for the release of radioactivity, but it is not clear whether actual releases will be held within these benchmarks. If data from the surrounding area is not collected before the tests begin, it will be very difficult to prove later that pollution was caused by the plant. The people living around the reprocessing plants in France and the UK didn’t have data showing the situation before reprocessing started, so they were at a great disadvantage when attempting to respond to the numerous problems that arose as a result of pollution and radiation exposure. Learning from their experience, we have decided to collect such basic data. We believe that it will be useful in all sorts of ways when responding to problems associated with the plant.

The current data from the surrounding area was collected by JNFL, or the relevant prefectural government office. Often this type of data and the method of collecting the data is not made available to the general public. Frequently assessments lack objectivity and are unreliable. Detection limitations are not always clear and there may be problems with the methodology. In this survey, citizens will take measurements and do the analysis themselves, so they will be able to clarify problems in the company’s measurements.

3. Major radionuclides released
See Table 1 and comments for each radionuclide below.

Table 1: Releases per year of operation of 4 major radionuclides in tera-becquerels (1TBq = 1012 Bq)

Half life (years)
Rokkasho (aerial)
Rokkasho (liquid)
La Hague (aerial)
La Hague (liquid)
Tritium (H3)
15.7 million

La Hague: actual releases (iodine-129 for 1999, others for 2003)
Rokkasho: benchmarks in license application

Comments for each radionuclide
1) Tritium (beta ray energy 18 keV) is currently contained in rainwater at a concentration of 0.001-0.002 Bq/cm3. In reactors it is formed mainly through ternary fission. When spent fuel is reprocessed, tritium mainly exists in water, or as gaseous hydrogen. Hydrogen molecules disperse rapidly in the atmosphere, so the radiological effect is not thought to be great. In liquid form it is mainly released as wastewater. When considering its radiological effect, it is important to bear in mind that it can be exchanged with hydrogen atoms in living organisms. The Rokkasho benchmark is similar to the actual releases from La Hague, but there is concern that the high liquid releases may contaminate marine organisms.
2) Carbon-14 (beta ray energy 155 keV) is present in the atmosphere in CO2 gas. The current level of radioactivity of 1 gram of carbon in atmospheric CO2 is 0.25 Bq. When spent fuel is reprocessed it is released in gaseous and liquid form. The benchmark for Rokkasho is similar to the total actual releases from La Hague. According to JNFL the liquid discharges are very small and are lumped under “other isotopes: non-alpha emitters” (see Table 3, previous article). The concentration of carbon-14 recovered from grass, seaweed and shellfish near La Hague is 3 to 4 times higher than normal. Even if the effect is small, eating food containing such carbon-14 will certainly increase internal exposure.
3) Krypton-85 (beta ray energy 687 keV) is formed in the atmosphere by cosmic rays, but the concentration from this is low. When spent fuel is reprocessed all the krypton-85 is released. As a consequence, the concentration of krypton-85 in the atmosphere has risen to 1Bq/m3. The Rokkasho benchmark works out at about 1 TBq per minute if the plant operates for 200 days a year. Krypton is not thought to have a great impact on human health, because it does not bio-accumulate, though it accounts for the largest portion of radioactivity released. Around La Hague concentrations over 10,000 Bq/m3 have been recorded. The Meteorological Research Institute in Tsukuba City in Ibaraki Prefecture notes that concentrations are affected by the Tokai reprocessing facility 60 kilometers away. Radioactivity from Rokkasho would be expected to reach major cities in Aomori Prefecture, including Aomori, Hirosaki, and Hachinohe.
4) Iodine-129 (beta ray energy 150 keV) is formed in the atmosphere by cosmic rays, but the concentration is very low. It is also released in gaseous and liquid wastes from reprocessing plants. There is a considerable difference between the actual releases at La Hague and the benchmark for Rokkasho. This is because equipment to remove it has been installed at Rokkasho, but it is not known how effective this equipment will be.

4. Measurement of tritium and carbon-14
1) Tritium: There is too little tritium in rainwater to measure with usual measuring devices. However, it is easy to measure tritium at the legal limit for wastewater of (60 Bq/cm3). Using a scintillation counter, this concentration can reliably be detected in 5 cm3 of water in one minute. At the low concentration of 0.1 Bq/cm3, a reliable measurement can be made in 30 minutes. We predict that a useful measurement can be made of radioactive contamination of seawater in the vicinity of Rokkasho and that it will be possible to follow the movement of contamination down the coast of Iwate Prefecture.
2) Carbon-14: For various reasons, the concentration of carbon-14 in the environment varies, so it is desirable to obtain data from the local area. To measure carbon-14, accelerator mass spectrometry is used. Special equipment is required for this. We intend to commission a private organization to do this. Since only a limited number of samples can be measured, careful selection from a large number of plant and animal samples is necessary.
3) Others: We are interested in krypton-85 and iodine-129, but we are unable to measure these isotopes in this survey. We intend to assess the data released by JNFL, etc. Besides the abovementioned isotopes, we also plan to measure gamma emitters by collecting samples of sand from the beach and sediment from the seabed.

Professor Michiaki Furukawa
(Member of CNIC Board of Directors)

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