The information on this page has been issued by the International Atomic Energy Agency (IAEA).

26 Nov 1999 - IAEA web site - IAEA Preliminary Report on Tokaimura Nuclear Accident

The International Atomic Energy Agency (IAEA) has issued a report on the preliminary fact-finding mission it undertook in mid-October in Tokaimura, Japan, following the criticality accident that occurred there on September 30.

The illustrated report, consisting of 35 pages, is available here in pdf format to download (size 1.2MB, about 7 minutes). You will need Adobe Acrobat Reader. (Help with Acrobat Reader.) To return to this page, please click the 'Back' button on your browser. Download report.

Alternatively, the report is available in hard copy from the IAEA's Division of Public Information, telephone +43-1 2600 21273 and fax +43-1 2600 29616.

31 Oct 1999 - IAEA web site - IAEA team returns from Japan

The IAEA fact-finding team on the Tokaimura accident has returned to Vienna from Japan, where it received good cooperation and was able to visit the main locations desired in the period October 13-17. The team is now drafting a short factual report based on their visit and other available information. It is hoped that the report will be available in about three weeks' time.

12 October 1999 - PR 99/15 - Fact-finding team of experts from the International Atomic Energy Agency leaves today for Japan

A team of three nuclear safety specialists from the International Atomic Energy Agency (IAEA) in Vienna is leaving today for Japan to ascertain the facts relating to the September 30 criticality accident at a fuel conversion facility in Tokaimura, following the Japanese Government's announced acceptance of the IAEA's offer to send such a team.

Between October 13-15 the team will visit both Tokyo and Tokaimura, where they will conduct their work and hold discussions. They will return to Vienna over the weekend and prepare an internal report on their findings. No public statements are planned while the team is engaged in fulfilling its mission.

Consultations are underway on the separate question of a possible review, within the framework of the IAEA, at a later stage of the outcome of the overall investigation of the accident and the lessons to be learned.

IAEA statements on the radiation accident in Japan [Available from http://www.iaea.org/ Accessed 3 Oct 99]: (1) Technical briefing on 1 Oct 99; (2) Press release 1 Oct 99; (3) Statement 30 Oct 99:

Radiation Accident - Technical Briefing on 1 October

Technical Briefing on the Radiation Accident in Japan

At a technical briefing for participants and press at the 43rd General Conference held in Vienna today, the IAEA made the following points relating to the 30 September criticality accident at the Tokai-mura Conversion Plant. They are based principally on confirmed information received from the Japanese government.

• the IAEA has offered assistance to the Japanese government, but has not yet been invited to assist in any investigation; an expert team remains on standby
• under the Convention on Early Notification of a Nuclear Accident, countries are only required to notify the IAEA when there is the risk of transboundary release of radiation, which was not the case in this instance. Hence, the information to the Agency from Japan was voluntarily provided and the IAEA's activation of its Emergency Response Unit also was done on that basis
• the Japanese government has provisionally rated this accident as a level 4 on the International Nuclear Event Scale, implying limited risk of radiological contamination off the site
• high doses of radiation were received by three workers; 2 of whom received doses of at least 8,000 mSievert
• 36 other workers on-site may have received abnormal doses, as well as 3 firemen and 7 nearby members of the public
• release of significant radioactive materials into the surrounding environment, other than short-lived gases; was unlikely
• for reasons unknown as yet, criticality continued on and off over a 17 hour period, until the water was drained
• the accident was an irradiation accident involving beams of radiation, not widespread contamination or dispersal to the environment
• the accident cannot be compared to the Chernobyl accident which happened at a specific type of nuclear reactor in limited operation and resulted in wide dispersal of radioactive materials
• the immediate area within 350 metres of the facility was evacuated and residents were ordered to stay indoors within 10 km of the facility; those measures have now been lifted

1 October 1999 - IAEA Press Releases PR 1999/12

Accident at the Tokaimura Fuel Conversion Plant

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, which runs from 0 to 7. (Click here if you prefer the pdf version.) 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.

Radiation Accident - Statement of 30 September

Radiation Accident in Japan

Japanese nuclear authorities informed the International Atomic Energy Agency on 30 September 1999 of an accident occurring at a uranium processing facility at the Tokaimura nuclear complex. The IAEA has maintained continuous contact with Japanese nuclear authorities and the facility operator as to the accident's causes and consequences, and attendant emergency response measures. IAEA Director General Mohamed ElBaradei has offered the Japanese Government the services of an IAEA expert team which would be ready to go to Japan immediately to assess the situation. 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.