Japan suffers serious radiation incident

Two workers received potentially fatal radiation doses and over 300,000 people were ordered to stay indoors, following a serious accident at a uranium processing facility in Tokai, Japan, on Thursday morning.

Unlike a nuclear power plant, the research facility in question was built near a residential area 70 miles north-east of Tokyo – 150 people were evacuated from a 350 metre radius around the plant, and another 300,000 living within 10km were told to stay indoors and wash off any rain they came into contact with.

According to the International Atomic Energy Agency (IAEA), the accident occurred 30 September at 10:35 am Japan time at the Experimental Conversion Facility at Tokai-mura. The cause of the accident remains under investigation, though it is known that it occurred when workers were transporting a mixture of liquid nitric acid containing 19% enriched uranium to a precipitation container.
A “flash criticality” occurred, an indication of a self-sustaining nuclear chain reaction, resulting in severe radiation exposure of workers. At its highest point, the dose rate at the facility boundary was measured to be around 4 millisievert/hour – some 20,000 times the normal level.

According to the Daily Yomiuri the accident happened because 16kg of uranium were used in a reaction where only 2.4kg should be used to avoid criticality.

JCO co, which runs the facility, admitted on Thursday that it lacked measures and equipment to prevent such incidents.

In the case of a nuclear power station, where fission reactions take place in a reactor, fuel is contained in rods in a reactor containment building. Some experts said the facility did not employ such multiple safety measures since it was an experimental unit and its function was to process nuclear fuel, reports Daily Yomiuri.

As of 4am local time Friday, the measured dose rate was decreasing, though it remained high in the vicinity of the facility and indicated that the chain reaction was continuing. The Japanese authorities said on Friday morning that the chain reaction has been brought under control and the situation is now stable.

The Japanese Citizens Nuclear Information Centre (CNIC) said today that it believed the accident was “not yet over. . . . Although the criticality condition has ceased, the radioactive materials are still being released into the atmosphere, and CNIC thinks that this condition will continue yet for a while”.

The incident took place less than 24 hours before the arrival of a shipment of weapons-usable plutonium at the Takahama nuclear power plant in Fukui Prefecture. The plutonium shipment is now at the centre of a scandal due to the producers of the fuel, British Nuclear Fuels (BNFL), having admitted to falsifying important safety data during production. The owners of the Takahama reactor are now investigating the scandal, however, Greenpeace alleges that they are still trying to limit the investigation and ignoring basic safety standards.

“Whether it is the Japanese government, BNFL or Kansai Electric [KEPCO, operators of the Takahama plant], all have a vested commercial interest in ignoring expensive safety standards. Today’s accident at Tokaimura confirms our fears: the entire safety culture within Japan is in crisis and the use of dangerous plutonium in reactors here will only increase the probability of a nuclear catastrophe”, said Shaun Burnie of Greenpeace International.

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