AECL provides update on NRU activities
(June 24, 2009)
Atomic Energy of Canada Limited (AECL) provides the following status report on the unplanned shutdown of the NRU reactor at its Chalk River Laboratories.
AECL reports that removal of all fuel, control and isotope rods has been completed. The heavy water level in the reactor vessel has been lowered and is being maintained at approximately 1.2 metres, the level required for ultrasonic inspections. The heavy water leak rate has been reduced to a flow of less than 0.5 kg/hr.
Non-destructive examinations (NDE) of the interior of the aluminum vessel are underway. Two sets of NDE measurements have been completed to date with initial results from one set in the area of the leak indicating significant wall thinning in a region 100 mm wide by 25 mm high. The second set of measurements indicated no significant thinning of the vessel wall. Further examinations are being conducted on a 24 hour /7 day rotation and are expected to take several weeks to complete.
Metallurgical and materials experts are assisting in determining the most effective options for cleaning, inspection and repair techniques for the reactor vessel. Mock-ups of the affected area of the NRU vessel have been constructed to provide on-site testing and training for vessel inspection and repair work. A full height mock-up of the reactor vessel components is currently being developed and will be assembled in the former NRX reactor building at Chalk River. This mock-up will allow AECL to simulate the repair procedures.
Further guidance on a return to service date will be provided as soon as sufficient data has been collected and analyzed from the non-destructive examination and a decision has been made with respect to the repair technique chosen.
AECL continues to communicate closely with CNSC on NRU outage issues, and CNSC safety inspectors at Chalk River are closely following work at NRU.
AECL confirms that there is no threat to workers, the public, the environment or nuclear safety related to this event. AECL will continue to provide updates to the CNSC and stakeholders as new information becomes available.