Radiation containment levels immediately plummeted to a quarter of what they measured before the water was drained and soon reached what officials said were near-normal levels. This is a very important first step in the process of clearing up this accident. The fission reaction started when a worker skipped a key step and mixed too much uranium with nitric acid in the storage tank on Thursday, an official for the JCO Co. plant said. Nuclear fission happens when neutrons hit uranium, causing atoms to split, releasing huge amounts of energy. It is the principle behind the atomic bomb.
Water stimulates the neutrons, spurring along the reaction.
Rescue teams said dozens of people were suffering from radiation exposure in Tokaimura, including the three hospitalized workers. Three paramedics who treated the workers were also found to be contaminated and were hospitalized. Government officials said Thursday's accident spewed a gas containing alpha, beta and gamma radiation into the atmosphere. Radiation levels soared as high as 17,000 times above normal shortly after the accident, officials said. About 150 people were evacuated from the immediate vicinity of the plant, one of 15 nuclear-related plants in Tokaimura.