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Calandria tubes installed in Unit 2 at Bruce A restart project By Lynda Cooper, myFM Radio |
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It's another first for Bruce Power as the calandria tubes have been installed in Unit 2 at the Bruce A Restart project. John
Sauger, executive vice-president of project management and construction
at the Bruce A Restart, said this is a precedent-setting activity. "In the 1990s, pressure tube life in Pickering and at other units had run its course," he said. "So, they had done these partial retubes at other CANDU plants, just replacing the actual fuel channels. "The way the reactors are constructed, there is a calandria tube on the outside and then the fuel channel is another tube that actually sits inside it. A partial solution is just to replace the fuel channel because that's what gets affected the most by neutron bombardment and starts to grow over time." However, when they looked at other reactors and the goal was to operate for another 25 to 30 years, the best way to ensure continued operation safely was to replace the whole thing - the calandria tube and the pressure tube, said Sauger. "This is the first time in the industry that this type of approach has been undertaken and completed," he said. "It's complicated to get them out. We used robotic tooling because of the dose rates involved and the complexity. They came out, they were all packaged and shipped to the Western Waste Management Facility, and new ones were installed - the first of a kind." "It took us longer than expected, but the priority was to do it right and make sure everything will work for 25 years. It took a little extra time to make sure all the joints where we roll the tubes into were very clean, pristine, as new, so they would last a long time." He said that effort and diligence has paid off in that the crew installed 480 tubes which were leak-checked on each end of the tube - 960 leak tests were done on those tubes and not one failed. "The crew had a tough sled ahead of them but they didn't give up," said Sauger. "They had a lot of challenges with the tooling. When there was a problem, they stopped, they analyzed it and came up with a plan. At end of the day, it took a little longer but it’s a perfect job."
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He credits the craftsmen in the province, the
boiler-makers and the millwrights on site. "They’re really artists," he
said. "The work they do is pure mechanical engineering. It's very
pretty to look at, and I know that sounds kind of strange, but when
they've done a job, it looks beautiful."
Sauger said Unit 1 is following Units 2 by about four to five months. With Unit 1, they had to stop the calandria tube and pressure tube install because when they took the old tubes out, debris fell into calandria, to the bottom of the vessel, he said. So CANDU services from AECL has fabricated special tools – super vacuums – that are put in with robotics and remote cameras and they go in and vacuum and remove any debris at the bottom of the calandria. "We did it on Unit 2 two months ago with excellent results," said Sauger. "We're gearing up for Unit 1 next week." He said it's an extensive project to clean the calandria, and will take about four days. Then they will install the calandria tubes and move into the more involved process of pressure tubes or fuel channels.
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