The last of the calandria tubes have been removed from Bruce A Unit 1, marking the end of the disassembly phase in the project to refurbish Units 1 and 2 at the Canadian plant.
|Fuel channels in a Candu reactor (Image: Bruce Power)
Each of the Candu reactors holds 480 calandria tubes, approximately six metres long by 13 cm in diameter, which lie horizontally inside the reactor and contain the pressure tubes, which in turn hold the uranium fuel bundles. Radioactive after years of service, these tubes were removed using remotely-operated, custom-designed robotic tools.
To complete this phase of the restart, a specialized tool was attached to one side of each reactor so it could push the tubes, one at a time, while another tool pulled from the opposite side. Guided into transfer cans, which served as contamination barriers, the six-metre long tubes were then placed on pallets.
To minimize the amount of radioactive waste, the tubes were then fed into a special press, which crushed and cut the tubes into small pieces. Each of these pieces were then stored in custom containers and transported across the Bruce site to the Western Waste Management Facility.
Workers from Atomic Energy of Canada Ltd (AECL) completed the removal of calandria tubes from Unit 1 in 26 days, compared with 117 days for Unit 2.
Hugh MacDiarmid, president and CEO of AECL, commented: "We have reached this important milestone through the combined effort and talents of Bruce Power and AECL employees. By applying many of the lessons learned from our work on Unit 2, we have overcome challenges and modified our tool sets to complete the calandria tube removal safely and in record time."
Bruce Power's president and CEO, Duncan Hawthorne, said, "The completion of this series marks the end of the most challenging part of this project. Having done so, and with a solid team behind us, our expectation going forward is that we can now work towards the successful rebuild and return-to-service of these units."
With the old calandria tubes now removed, workers are preparing the reactor vessels to accept new calandria tubes with the aim of returning both units to service in 2010.
"There has never been another project quite like this in the Canadian nuclear industry," remarked John Sauger, senior vice president of Bruce Power's restart project. "We're proud to be blazing a path for others to follow and I thank everyone who has brought us this far. But our work is far from over. Our job now is to put these reactors back together, to do it safely and to deliver a first-class product."
The Bruce site hosts eight reactors built in two large blocks of four each. Bruce A contains units 1 to 4, Bruce B has units 5 to 8.
Units 1 and 2 started commercial operation in 1977, but unit 2 was shut down in 1995 due to a maintenance accident in which lead contaminated the core. Unit 1 was laid up with another six units at the end of 1997 to allow operational focus on newer plants.
However, facing an impending power shortage, the Ontario government in October 2005 agreed with Bruce Power to refurbish the Bruce A units, each 769 MWe, rather than the longer process of building new ones to replace them.
Bruce 1 and 2 are having their fuel channels and steam generators replaced and ancillary systems upgraded to current standards, giving them a further 25-year life. Sixteen new steam generators have already successfully been manufactured and installed at the units. Once the refurbishment of Units 1 and 2 has been completed, Units 3 and 4 will then undergo a similar refurbishment.
The latest estimated cost of returning the two reactors to services is between C$3.1and C$3.4 billion ($2.4 and $2.6 billion).