COVER STORY | CANDU REPLACEMENT
we have to have inspection points so all of those things that need to be done associated with that change in process also needed to be completed.” OPG also adopted new digital and automated tools where
possible. This not only meant plant equipment, such as new digital controls for the steam turbines, but also in the refurbishment process, too. “We’re removing components that have been in the in the reactor for 30 years but many of the tools used for the removal phase of the reactor used digital and automated tooling to make the process safer and easier. Many of these tools were controlled by an operator who was in a different location from the actual vault where the work was being done. The whole point of that was to minimise the number of people that were interacting with the tool during the removal phase and increase safety for workers,” explains Rose. “There’s a number of digital improvements that were made in the tooling and continued to advance to automate the job and increase worker safety,” says Rose. Again, learnings from Unit 2 were applied to get the most out of the automated tooling. He says: “A lot of our welding tooling for the feeder pipes is automated. You lock on these welders, calibrate all the tools and through computer- assisted processes do the welding. It is very difficult to get the parameters right to make sure that the welding happened correctly though. That was one of the lessons learned on Unit 2. Because every weld is subsequently inspected, in Unit 2 the radiography required clearing the zone. We went to digital radiography in the subsequent units so in Unit 3 by using a digital radiography you did not need to get every worker out of the vault to do the radiography. That is another technology advance.” The use of mock ups and detailed modelling of
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Unit 1 is being refurbished in parallel with Unit 3, both are building on learnings from Unit 2
procedures with new tools were also important to the overall success of the refurbishment programme. “The other key lesson from the project is that we created a full-scale mock-up of the calandria at the Darlington Energy Complex about 1.5 km from the station. Every single tool that we used in the plant was fully tested once at the factory during functional acceptance testing but also inside our mock-up. We would run it through its paces in as real-life situation as possible, we’d get the workers, put them in plastic suits and run them through the process of operating that tool. We’d even try to break it, throwing things out that were
anomalies and making sure that they knew how to react. The whole point was if you fully tested that tool in the mock-up and fully trained the workers before they went into the real thing, you’re likely more successful.” OPG worked with the third-party contractor SNC Lavalin
Ltd but the tooling was sub-contracted to a number of different companies, including ATS, Cambridge, Rolls-Royce and others. CANDU also produced some of the tools. Although the physical mock-up at Darlington delivered
numerous operational benefits there were limitations due to the differences between the blueprints and the as-built plant. This required additional processes such as blue laser scans of the existing plant to know where all the positions were. “We used that as part of the planning,” says Rose, adding: “These reactors were built 30 years ago and even though there’s a design, the components are slightly out of place in terms of exact location. When you’re rebuilding components to put in there we want to make sure we accounted for that so we did a full laser scan of the vaults which then created a digital model.”
The importance of planning While it is almost unique to have any kind of nuclear project delivered on time and on budget, the Darlington refurbishment has achieved that through an intense planning process, including mock-ups and modelling. “It really boils down to meticulous planning. Planning doesn’t guarantee success, but a lack of planning guarantees failure. We planned this job extremely well. We are rate regulated by the Ontario Energy Board and we had to present our plans and our cost estimate schedule to them. Independent experts said they hadn’t seen a project that was so ready to be executed. We had good plans and we had to stick to them,” says Rose, adding: “Too often I’ve seen where projects are very well planned and risk registers are created and then during the project it seems all of that gets parked and forgotten about. Because we had planned the project so well, we knew where we were supposed to be each and every day and if we weren’t we could take action. By knowing where we were supposed to be and how many people we were supposed to have on the work if we weren’t accomplishing the production rate it was very visible. Every day there was an issue we focused in on why we didn’t achieve the planned progress and what we were doing to resolve those issues. That meticulous focus each and every day really drove us to success. If there was a problem we were asking why and fixing it and rectifying it very early.” However, he also adds a note regarding the importance
of built-in flexibility as a result of in-depth planning. Rose says: “In every project we have contingency. There are risks on every project and we have mechanisms to draw down contingency. We used to draw down funds for contingency and where we had opportunities we would actually fund contingency. So, if we learned something on Unit 2 that we could put forward on Unit 3 we took the budget away and put it back into contingency in case any other things came about. We created what we called an opportunity register corresponding to a risk register and we went after the opportunities as aggressively as we manage the risks.” Once the refurbishment programme is complete in 2026,
this C$12.8 bn (US$9.4 bn) project will enable the Darlington station to operate for an additional 30-plus years but the learnings on CANDU will potentially last far longer, reducing the cost and risk of reactor replacements. ■
26 | May 2023 |
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