AECL provides update on the NRU reactor
(May 27, 2009)
The following information bulletin is in accordance with Atomic Energy of Canada Limited's (AECL) commitment to enhance its voluntary public disclosure of events related to the Chalk River Laboratories (CRL).(2009 May 27) Atomic Energy of Canada Limited (AECL) provides the following status report on the unplanned shutdown of the NRU reactor at its Chalk River Laboratories.
On Monday, May 18, AECL reported that the NRU reactor would remain out of service for more than one month in order to investigate and repair a heavy water leak in the reactor vessel. Since then, AECL staff have been working around the clock to complete the initial investigation of the reactor vessel.
The location of the heavy water leak has been identified at the base of the reactor vessel in a location where there is corrosion on the outside wall of the vessel. Initial inspection of the full circumference of the external wall at the base of the reactor vessel using remote cameras is now complete. Results from this inspection indicate additional corrosion points on the outer wall of the vessel that will require further examination. Test equipment is being prepared to inspect the interior of the reactor vessel.
"Sophisticated diagnostic procedures are required to determine the exact nature and extent of the repairs before returning the NRU reactor safely to service," stated AECL's Senior Vice-President and Chief Nuclear Officer, Bill Pilkington. "Based on our preliminary findings to date, we now believe that the NRU reactor will be out of service for at least three months."
Hugh MacDiarmid, President and CEO of AECL added "Until all investigations are completed, it is premature at this point to set a definitive timeline for the return to service of the NRU reactor. We want to reassure Canadians that every effort is being taken by our team of experts to address the situation as quickly as possible while adhering to all prescribed safety procedures. We remain committed to providing regular updates on the situation just as soon as we learn more about the condition of the reactor vessel and the repair requirements."
AECL has also lowered the heavy water level in the reactor vessel. As a result of this action the initial leak rate of 5 kg/hr. has been reduced by approximately one quarter. The heavy water is fully contained and is being stored in specially designed drums. Due to high airflow in the area, a small portion of the leakage evaporates and results in a monitored tritium release through the NRU reactor ventilation system. Although the airborne release is well below regulatory limits, the release has reached action levels for tritium. While this level does not pose a threat to the public or our workers, this is the level at which AECL reports to stakeholders and the Canadian Nuclear Safety Commission (CNSC) for administrative purposes.
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 when new information becomes available. A detailed briefing for media is planned for next week.