Exposure of Workers at Plutonium Fuel Research Facility

Print View Posted on: 20 April 2018

Event Date: 06 June 2017 Event Type: Research Facility
Event Location: Japan, Oarai Research and Development Center INES Rating: 2 (Final)

Body contamination was found from five workers who dealt with condition check of storage containers that stored nuclear fuel material at the Plutonium Fuel Research Facility (PFRF) in Oarai Research & Development Center of Japan Atomic Energy Agency on June 6, 2017.
In the PFRF, mixed powder of Plutonium oxide and Uranium oxide for laboratory use was packed in a polyethylene container, wrapped in a plastic bag, and stored in a storage container finally. During condition check of the polyethylene container in the concerned storage container, the plastic bag was ruptured by over pressure. It resulted contamination on surface of hands and feet of five workers. No injury reported. Each worker wore protection mask at the event however nose contamination was found from three workers.
There was no abnormal indication found in dust monitor in ventilation system or monitoring posts around the site, thus no release reported.
The results of bio-assay analysis showed that the maximum committed doses of assessed individual was 100 to 200 mSv in effective dose, while the statutory annual dose limit of Japan is 50 mSv.
The gas which caused rupture was generated by α-ray decomposition of contaminated organic substances (i.e., epoxy resin) which was not stabilized. The necessary information on the storage (radiation, properties, usage history) was not shared among workers. Operator will improve handling methods (stabilization of contents, cans in a cell or glove, preservation of records) as management standards and will re-educate those to the workers.

INES Rating: 2 - Incident (Final) as per 21 February 2018
Release beyond authorized limits? No
Overexposure of a member of the public? No
Overexposure of a worker? Yes

Contamination spread within the facility? No
Damage to radiological barriers (incl. fuel damage) within the facility? No

Degradation of Defence In-Depth No

Person injured physically or casualty? No
Is there a continuing problem? No

Shinichi Murata
Nuclear Regulation Authority

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