On May 26, 1999, four AECL employees entered a controlled radiological zone to perform work on a ventilation system. The work involved the removal of a component (baffle box) in a room in a building that contained a plutonium processing facility. The facility has been non-functional since 1957, and remained in a dormant state in preparation for decomissioning. Workers were wearing protective and monitoring equipment. Cutting of the baffle box proceeded for an hour and 40 minutes and dust was observed falling from the box. When work was terminated and upon exiting the area, personal contamination monitors detected contamination on the clothing of all workers. Immediate actions included placing work restriction on affected personnel and initiating dose assessment through bioassay techniques. Initial exposure estimates were less than 11 mSv. Recent indications are that the maximum committed doses are of the order of 24 to 55 mSv for the four individuals involved. 50 mSv is the regulatory dose limit. Radiochemical analysis is continuing to determine whether doses exceeded the regulatory limit. Following the incident, the AECB, the regulatory authority in Canada, has conduced an inspection at CRL and continues to gather information on the incident.
Location: CHALK RIVER LABORATORIES Event date: Wed, 26-05-1999