By Virginia Heffernan
Nuclear Power: Pickering’s ProblemsEngineering
The complexities of bringing a 30 year-old nuclear power station up to modern standards have proved daunting for design engineers assigned to the Pickering A plant in southern Ontario.When the station...
The complexities of bringing a 30 year-old nuclear power station up to modern standards have proved daunting for design engineers assigned to the Pickering A plant in southern Ontario.
When the station on the shores of Lake Ontario east of Toronto was closed five years ago because of safety and environmental concerns, all four of its units were expected to be back on-line by the end of 2001. Now only one of them, Unit 4, will be ready for commissioning in the foreseeable future.
The fate of the other units remains uncertain as Ontario Power Generation (OPG), the crown corporation that owns and operates Pickering A, weighs the “appropriateness” of the estimated $300-$400 million price tag for repairing each one. (The four reactors of the adjacent and newer Pickering B are still operating).
At Pickering A Unit 4 alone has already cost $1.025 billion and another $230 million will be spent before the plant is ready for start-up in mid-2003. The total cost of the Pickering A project has swelled to $2.5 billion, more than twice the original estimate.
“We underestimated the size and complexity of the whole project as we tried to take a 1960s to 70s design and move it to today’s standards,” says John Earl, spokesman for Ontario Power Generation (OPG).
One of the biggest challenges was design engineering. About 35,000 different work packages were generated by either the initial plant redesign or the subsequent environmental assessment process. The sheer quantity of work created conflicting demands, resulting in tasks overlapping on each other or getting out of sequence, says Earl.
Some of the valves that control fluid flow, for example, had to be redesigned twice, one of about 1,500 “field change notices” that forced engineers back to the drawing board to incorporate design alterations after construction was already under way.
The refurbishment of the reactor condensers illustrates the complexity of the job. In a nuclear reactor, the heat generated from fission is used to generate steam to drive the generator turbines. As part of a closed loop system, the steam is converted into water in a condenser and then the water is reheated to create more steam. But the copper-zinc alloy used in the original condensers at Pickering A eroded over time.
As a result, Ontario Power Generation opted to replace the condenser walls with stainless steel, a material with greater longevity. But that decision triggered yet another task: installation of a special ball bearing cleaning system required for the new material. As a result, the designers had to come up with a whole new set of drawings to pass on to the trade workers, then separate the project into manageable sub-tasks for the construction stage.
The work, including project management, was largely contracted out to engineering and construction firms. Atomic Energy of Canada Limited (AECL), which designed and built the CANDU reactors at Pickering A, took the lead on design engineering. CANEC, a consortium that included Canatom NPM, a subsidiary of Montreal’s SNC-Lavalin and BFC Construction, Comstock Canada, a member of the mammoth U.S.-based EMCOR Group, and Stone & Webster, a Shaw Group company of Louisiana, shouldered responsibility for construction and project management. Schneider Canada Services, in partnership with Babcock and Wilcox, a global nuclear engineering manufacturing company with a plant in Cambridge, Ontario, refurbished the switchgears and motors that control the reactor coolant pumps and safety systems.
“There are only a few firms that have the expertise and experience that we could harness in bringing Pickering A back into service,” says Earl.
But while OPG staff were preoccupied with concurrent construction and renovation projects at the company’s other nuclear power plants plants, work at Pickering A fell into disarray.
“We did not have the staff capability to do both projects at the same time, and we decided that the improvement and safe operation of Darlington, Bruce B and Pickering B would take precedence,” Ontario Power Generation president and chief executive officer Ron Osborne told the Canadian Independent Power Producers in October. “Having a combination of contractors and OPG sharing management of the project did not work.”
OPG has since taken over full management of the project, including the design engineering for Unit 1, with the contractors acting in a subordinate role.
Another costly delay was the unexpected requirement for an environment assessment. Although OPG had already conducted an environmental review of the Pickering A and B stations when the company decided to restart the plant in 1998, regulations under the Canadian Environmental Assessment Act triggered a formal assessment that took 20 months to complete. The work wasn’t finished until February 2001.
“We did not feel it was prudent or proper to begin the major rebuilding work until after we received the go-ahead by the regulator,” said Osborne.
Unit 4 is expected to add 500 megawatts to Ontario’s supply of electricity by the second half of next year. If the remaining three reactors, with an added capacity of 1,500 megawatts, eventually come back on-line, Pickering A will recapture its role as a significant supplier to the province’s 27,000 megawatt grid. But given the monumental problems encountered so far, that remains a big if.
Virginia Heffernan is a freelance writer living in Toronto.