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| Our campaign against nuclear power in Japan |
The numbers of people who suffered radiation exposure during the nuclear accident at the Tokaimura uranium plant was almost certainly higher than the Government estimates of forty-nine due to the high levels of neutron radiation, coupled with the slow evacuation of the area, Greenpeace said today, based on results of an investigation around the site.
Releasing the monitoring results in Mito city and Tokyo today, Greenpeace said that it had found evidence of radioactive fallout. Greenpeace also found high radiation levels on a public road near the plant on Sunday - 24 hours after the all-clear was given by the Government - and compelling evidence of high levels of neutron radiation. Neutron radiation is the most penetrating and one of the most dangerous forms of radiation.
"Greenpeace undertook this survey in order to provide some independent assessment of the levels of radiation and the extent of contamination resulting from the Tokaimura accident," said Greenpeace Japan executive director, Sanae Shida. "Our results raise further serious questions about the Japanese government's nuclear safety and emergency planning procedures and the safety of the nuclear industry in general."
Greenpeace said that during the critical accident period, which lasted some 20 hours, high levels of neutron radiation (1) appear to have irradiated the environment up to a distance of at least 500 metres from the site of the accident. (This conclusion is supported by radiation modelling carried out by the environment group, Citizens Nuclear Information Centre- CNIC). This undoubtedly would have affected the hundreds of people who traveled on a nearby main road, were in the more than 170 houses, on a golf range and on agricultural land .
Neither the owner of the plant, JCO, nor the Japanese authorities used neutron detectors until six and a half hours after the accident. However Greenpeace was able to estimate the full radiation doses by analysing household salt samples obtained from residents living around the plant. When salt is bombarded with neutron radiation, the radioisotope sodium (natrium) 24 is created. The amount of this radioactive isotope present in the salt can then be used to calculate the intensity of neutron radiation emitted during the accident.
"Just as the table salt was bombarded with neutrons so were all the people within range of the accident site," said Diederik Samsom, a nuclear engineer and qualified radiation protection officer, who led the Greenpeace investigation.
"It was known 10 minutes after the accident that this incident was a criticality event (nuclear chain reaction). Evacuation from the surrounding area to avoid the penetrating neutron radiation should have been immediate. Instead it was almost four and a half hours before the evacuation order was announced."
The Greenpeace research team also found elevated levels of Iodine 131 and Iodine 133 in plant and soil samples around the plant. This shows that the accident resulted in radioactive fall-out. Iodine-133 has a short half life and therefore cannot have come from any other source. However, the lack of non-volatile radioactive elements in the samples (such as Cerium-144) suggests that the actual release from the accident was limited to the gaseous and volatile substances.
"It seems that a worse case scenario was avoided in this case. But this was more the result of good luck than good management. If the tank containing the uranium had ruptured, the situation would have undoubtedly been considerably worse," said Samsom. "Nevertheless, there was fall-out and the public around the site needs to know what were and are the exact levels. Our sampling showed there is a need for more research. It's now up to the authorities to extend their sketchy reporting to a full-scale assessment of contamination levels in the area around the plant."
Greenpeace also urges the government to conduct a long-term health monitoring programme of all people who were in the vicinity of the plant during the accident. The first step should be immediate registration of all people likely to have been exposed to radiation.
"The accident demonstrates the lack of a safety culture within the nuclear industry globally, and illustrates the inherent hazards of nuclear technology," said Greenpeace International nuclear campaigner, Shaun Burnie. "This is not an isolated incident. Yesterday, 29 workers were exposed to elevated radiation levels as a result of a leak of radioactive material at the Wolsung nuclear power plant in South Korea. The Japanese and other governments must change their energy policies by ending nuclear programmes, including fast breeder reactors, and moving into energy efficiency and renewable energy."
Notes to editors:
(1) 8 milliSieverts (mSv)/hour at fence
1 mSv/hour at 175 metres from plant
0.05 mSv/hour at 500 metres
