Atomic Energy of Canada Limited (AECL) said Wednesday that due to the most recent data from the ongoing assessment of the National Research Universal (NRU) medical isotope reactor, and the development of a critical path for the various repair options, the NRU will not return to service before late 2009.
The 51-year-old NRU reactor in Chalk River, Ont., had been responsible for half of the radioactive medical isotopes used by oncology and cardiology clinics and hospitals in the United States.
The organization said the duration of the shutdown continues to be founded on the best evidence available, including the most up-to-date analysis of the heavy water leak site, vessel condition, repair strategies and critical path requirements for restart after an extended shutdown.
"We have identified three phases of our return to service plan. Today we are progressing toward the end of phase one which involves a comprehensive condition assessment of the reactor, the development and testing of several repair options, and overall planning and critical path development," said AECL's President and CEO Hugh MacDiarmid. "This work will contribute to a decision on the preferred repair strategy to pursue in phase two."
A decision on the repair method is expected in the next few weeks, according to AECL. Phase two of the plan, effecting the actual repair, is estimated to take about two months depending on the method determined, regulatory considerations and further analysis of the extent of the repair required. Phase three, restarting and testing the reactor, is estimated to take an additional two months, based on AECL's previous experience of refilling, refuelling and start-up of the reactor in 1992.
To date, the organization said that the leak site at the base of the reactor, which is approximately nine meters from the closest access location, has been thoroughly analyzed. More than 60 percent of the reactor vessel's circumference has been surveyed. The review has revealed thinning of the wall at the leak site, and identified a total of nine areas of interest.
AECL said its metallurgical and material experts are working with external engineering firms having remote repair capability to determine the best methods for cleaning and repairing the reactor vessel.
Mock-ups of the affected area of the NRU vessel have been constructed to provide necessary on-site testing and training for vessel inspection and repair work, and a full-height mock up of a section of the reactor is currently being built.
"All of the evidence to date supports the view that the NRU can be successfully returned to service," said Bill Pilkington, AECL's senior vice president and chief nuclear officer.
"Returning the NRU to service to support the production of medical isotopes for Canadian patients and healthcare practitioners is our primary objective," MacDiarmid said. "However, it is a complex task with many variables."