The International Atomic Energy Agency (IAEA) learned at approximately 9 a.m. Vienna time on September 30 that an apparent criticality accident had occurred at a fuel conversion plant in Tokaimura.
The IAEA immediately made contact with the Japanese authorities in order to obtain authoritative information and to follow the situation closely, which it did through its Emergency Response Unit - which was established to fulfil the IAEA’s obligations under the relevant international Conventions - throughout the day and last night as the situation evolved. It should be noted that the information was provided by Japan on a voluntary basis and not pursuant to the Convention on Early Notification of a Nuclear Accident, which in the view of the Japanese authorities was not triggered. All indications thus far suggest that the accident was due primarily to human error.
The accident now appears to have been more serious than originally believed. Some 39 workers at the plant were exposed to radiation, three of them very seriously. The degree of exposure to the others, as well as to ten members of the public, is being assessed.
The criticality - a chain reaction - continued on and off for some 17 hours until it was stopped early this morning. Evacuation of families within 350 metres of the perimeter has been implemented. A decision to shelter the population out to a radius of about 10 kilometres was in effect until today, but has now been lifted.
The IAEA issued a series of six status reports to contact points in Member States and to Permanent Missions here in Vienna giving information as it became available. The Director General, Dr. Mohamed ElBaradei, also offered to send an expert team immediately to Japan but the Japanese authorities have indicated that it is not necessary at this stage. If requested, the IAEA stands ready to provide assistance to the Japanese Government and also to perform an evaluation with the co-operation of the Japanese authorities once the situation permits.
The IAEA has been notified that Japan has given a provisional rating for the accident of level 4 on the IAEA’s International Nuclear Event Scale [pdf], which runs from 0 to 7. It has also been informed that the Japanese authorities at this time are carrying out measurements of the level of radioactivity in the vicinity of the facility.