AECL reports that removal of the last NRU fuel rod was successfully completed June 15. Removal of the remaining 15 control, adjuster and cobalt-60 isotope rods has begun. Seven of these assemblies were removed from the reactor as of June 16.
Completion of rod removal and the subsequent removal of heavy water from the reactor is expected to be complete by the end of this month. Final preparations are underway to conduct a detailed inspection of the condition of the reactor vessel using remote non-destructive examination techniques. This task will be performed as soon as the remaining rods and heavy water have been removed.
AECL is drawing on advice provided by its technical staff and industry experts to determine the most effective options for vessel repairs. AECL continues to work with industry experts on cleaning, inspection and repair techniques for the reactor vessel. Earlier this week, AECL was provided with a demonstration of a potential repair technique from a supplier company. Evaluation of this and other inspection, cleaning and repair options continues.
A full-scale mock-up of a portion of the NRU vessel is currently being constructed at Chalk River. This mock-up will serve to provide on-site testing and training of vessel inspection and repair work.
The NRU heavy water leak rate has been reduced to a flow of between 3-4 kg/hr. A small portion of the leakage evaporates and results in a monitored airborne tritium release through the NRU reactor ventilation system. While this airborne tritium release remains about 1/1,000 of the regulatory limit, the action level for tritium release to the atmosphere was exceeded this week due to the leak.
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.