Information provided to the IAEA by Japanese authorities – as of 11 pm Vienna time on 30 September -- included the following points:
- 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. As of 4 am local time, the measured dose rate was decreasing, though it remained high in the vicinity of the facility and indicated that the chain reaction was continuing. Mitigation measures included draining water from the precipitation container.
- At least two workers were exposed to radiation doses as high as 8 sievert, a level that can lead to fatality. Another worker has been seriously exposed. Two of the three workers are known to have received potentially fatal doses. All are under medical care and treatment. An additional 21 persons were exposed to lower doses and are under medical evaluation.
- As part of emergency response measures, access to the uranium facility has been restricted at a radius of 200 meters. Additionally, authorities have established a 350-meter evacuation zone around the facility. Persons residing within 10 kilometers of the facility are being advised to take shelter until tomorrow and local transportation has been stopped. The Japanese Government has established an Emergency Task Force in response to the accident
The IAEA will be providing further information as it is received from the Japanese Government.