May 31, 2013
Radiation Production Facility Accident Report
Incorporated Administrative Agency - Japan Atomic Energy Agency
Inter-University Research Institute - High Energy Accelerator Research Organization
Subject : Leak of Radioactive Material at the Hadron Experimental Facility, Japan Proton Accelerator Complex (J-PARC)
Time and Date of Accident : Approximately 11:55 am on 23 May 2013
Accident Location : Hadron Experimental Facility, J-PARC
Description of Accident :
It is presumed that due to a malfunction of the beam extraction system, the gold target of the Hadron Experimental Facility was damaged and radioactive material was discharged into the room that contained the target and the primary beamline. The radioactive material then leaked into the experimental hall where workers were exposed to radiation
Area monitors around the boundary of the controlled area registered an increase in ambient radiation. Higher than normal levels were also observed for a short period at the three monitoring posts and stations near to J-PARC of the neighboring Nuclear Fuel Cycle Engineering Laboratories. Accordingly, it is reasoned that there was a radiation leak from within the controlled area of the Hadron Experimental Facility.
Radiation Leakage and Exposure within the Controlled Area :
It is presumed that the gold target of the Hadron Experimental Facility was damaged and radioactive material was discharged into the room that contained the target and the primary beamline. The radioactive material then leaked into the experimental hall.
Thirty four (34) registered radiation workers in the controlled area of the Hadron Experimental Facility received total (internal plus external) radiation doses between 0.1 and 1.7 mSv.
Radiation Leakage into the Environment and It's Effects :
Simulations indicate that the leaked material would have diluted and decayed as it dispersed in a narrow range towards the west of the Hadron Experimental Facility. It has been estimated that the maximum integrated radiation dose at the site boundary closest to the Hadron Experimental Facility was 0.29μSv (preliminary) .
Cause of the Accident :
A detailed investigation will be carried out.
Immediate Response and Future Measures :
All J-PARC accelerators have been shut down and access to the hadron experimental hall has been restricted. Taking into account the findings of the investigation, all necessary measures to prevent a reoccurrence of the accident will be examined.