Nuclear Disasters Disasters
The first Tokaimura nuclear accident occurred in a nuclear reprocessing plant of the Dōnen (Power Reactor and Nuclear Fuel Development Corporation) on 11 March 1997. It is sometimes referred to as the Dōnen accident.
In the evening hours of Tuesday, 11 March 1997, a small explosion occurred in a nuclear reprocessing plant of the Dōnen. Windows broke, allowing smoke to escape into the atmosphere. On the following Thursday, workers used duct tape to perform repairs on thirty broken windows and three doors that sustained damage from the blast. At least 37 of the workers were exposed to elevated levels of radiation during the incident.
A week after the event, meteorological officials detected unusually high levels of caesium 40 kilometers (25 miles) south-west of the plant.
The second, more serious Tokaimura nuclear accident occurred on 30 September 1999, and resulted in two deaths. It was the worst civilian nuclear radiation accident in Japan prior to the Fukushima Daiichi nuclear disaster of 2011.
The criticality accident occurred in a uranium reprocessing facility operated by JCO (formerly Japan Nuclear Fuel Conversion Co.), a subsidiary of Sumitomo Metal Mining Co. in the village of Tōkai, Naka District, Ibaraki Prefecture.
Tōkai is a village located in Ibaraki Prefecture, Japan. The Japan Atomic Energy Agency along with other organizations operate a number of nuclear technology research facilities in the town. There have been two Tokaimura nuclear accidents at the nuclear facility at Tōkai, Ibaraki: on 11 March 1997, an explosion occurred in a Dōnen plant, and on 30 September 1999, a serious criticality accident happened in a JCO plant.
In the evening hours of Tuesday, 11 March 1997, a small explosion occurred in a nuclear reprocessing plant of the Dōnen. Windows broke, allowing smoke to escape into the atmosphere. On the following Thursday, workers used duct tape to perform repairs on thirty broken windows and three doors that sustained damage from the blast. At least 37 of the workers were exposed to elevated levels of radiation during the incident.
A week after the event, meteorological officials detected unusually high levels of caesium 40 kilometers (25 miles) south-west of the plant.
The second, more serious Tokaimura nuclear accident occurred on 30 September 1999, and resulted in two deaths. It was the worst civilian nuclear radiation accident in Japan prior to the Fukushima Daiichi nuclear disaster of 2011.
The criticality accident occurred in a uranium reprocessing facility operated by JCO (formerly Japan Nuclear Fuel Conversion Co.), a subsidiary of Sumitomo Metal Mining Co. in the village of Tōkai, Naka District, Ibaraki Prefecture.
The accident occurred as three workers, Hisashi Ouchi, Masato Shinohara, and Yutaka Yokokawa, were preparing a small batch of fuel for the Jōyō experimental fast breeder reactor, using uranium enriched to 18.8% with the fissile radionuclide (radioisotope) U‑235 (with the remainder being the fertile U‑238). It was JCO's first batch of fuel for that reactor in three years, and no proper qualification and training requirements appear to have been established to prepare those workers for the job. At around 10:35, a precipitation tank reached critical mass when its fill level, containing about 16 kilograms (35 pounds) of uranium, reached about 40 liters (11 U.S. gallons). More details
