Tens of thousands of Japanese residents have been warned to stay indoors and the government says further nuclear reactions at the processing plant Tokaimura may still be taking place. At least 14 workers have been taken to the hospital. The two were in a state of shock with fever and diarrhea. Plant staff and 150 members of the nearby community have been evacuated and a further 300,000 people within a 10km radius have been told to stay indoors, and to wash off any rain that falls on them. Local schools were closed after the accident.
Criticality is the point at which a nuclear chain reaction becomes self-sustaining.
According to JCO officials, the reaction occurred when workers mixed too much uranium with nitric acid in a storage tank. Nakahara said that when workers are able to get inside the plant, they will attempt to drain water from the tank in the hope of stopping the nuclear reaction. Water, he explained, magnifies the radiation, making the nuclear reaction possible. Schools and transportation services in the region were shut down. Officials from the Ibaraki Prefecture, the local state government, said radiation levels were 10 times higher than normal up to 1.2 miles outside the plant, but had been as high as 10,000 times above normal shortly after the accident.