At 10:06, March 11, 1997, a fire occurred in the cell of the Bituminization Demonstration Facility, and ventilation system stopped. Ten hours after the fire, an explosion occurred in the facility, and containment of the cell and building was degraded. Following the fire and the explosion, workers were evacuated from the facility and adjacent facilities. It is assumed that the largest radiation dose level to the workers was 0.4 to 1.6 mSv and the maximum quantity of the Cs-137 released from the facility was 1 to 4 GBq.
The investigation Committee was organized under the Science and Technology Agency (STA). The Committee reported the results of the investigation into causes of the fire and explosion, the problem of operation management system, etc.
Justification of the rating:
This incident was rated level 3 based on the results of the assessment. Both "off-site" and "on-site" criteria were not applicable.
On the "defence-in-depth" criterion, this incident was rated level 2, which is assumed a maximum rating level for this facility, because the containment function of facility was lost. Allowing for additional factors, the level was upgraded by one level because of lack of safety considerations that the knowledge of the similar accident in the past was not sufficiently reflected, etc.
Event date: Tue, 11-03-1997