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  • Christopher Adlam

A tribute to the CANDU

It seems that Canadians often have a hard time with patriotism. I'm not talking about the overtly contradictory American flag proudly hanging from a pole made in China type of patriotism, but the kind where we are proud of things that are uniquely Canadian and identifiable as such on the world stage: developed by Canadians for Canadians and we then share that genius with the rest of the world.


Back in the 1950's while the US and the rest of the world were hotly pursuing atomic weapons, Canada, who had no desire for nuclear arms, saw the power of the atom as a way to produce abundant and inexpensive electricity. Atomic Energy Canada Limited (AECL) was the Federal thinktank comprised of brilliant engineers whose goal was exactly that: come up with a nuclear reactor that didn't require enrichment (we didn't have enrichment capability because we didn't have a nuclear arms program) and whose purpose was to be used for power generation.


Utilizing deuterium as a moderator, which allowed the use of a fuel with very low fissile content (natural uranium), what would become the foundation for the CANDU was in its infancy. A pressure tube design was chosen as the low fissile content fuel would need to be swapped out frequently, thus it was a requirement that the reactor could be refuelled online.

After a small radiological release incident at Chalk River, it was determined that multiple levels of containment and redundant safety systems would be absolutely necessary. A family of designs was born from this philosophy with safety being the top priority.

After NPD was constructed and successfully demonstrated the CANDU concept the first commercial unit for the purpose of power generation was constructed. This was in the early 1960's at Douglas Point, now part of the massive Bruce Power site. This ~200MWe unit was a proof-of-concept design and led to the construction of the 4 units at Pickering A in a partnership between AECL, the Federal Government, the Ontario government and Ontario Hydro. Pickering was built instead of a similar capacity (4GW) coal plant.


Pickering was a massive success and by this point AECL had come up with a larger design and Ontario Hydro was keen. This led to the construction of Bruce A whose steam generators were intentionally oversized so the units could produce process steam to run operations on the grounds, such as the massive heavy water plant designed to produce deuterium both for domestic use and export. It was expected that the CANDU would be popular abroad, as we had managed to obtain partnerships and construction contracts with India, Romania, New Brunswick, Quebec...etc. CANDU was going places and we wanted to be ready.


On the heels of Bruce A came Pickering B, now based on the standardized CANDU 6 design, but with some changes on the steam and generation side to make it more similar to the A plant, thus reducing output. Then Bruce B was built, as efforts were made to cement the design for what would be the next export-ready unit, the CANDU 9. This led to the first commercial construct of that unit design: Darlington.


Darlington is probably the best known and most maligned nuclear plant in Ontario's entire nuclear fleet. Construction started while Bruce B hadn't even come online yet (similar to Bruce A and Pickering B) and was well underway when disaster struck: Half a world away a massive and unweildly reactor designed to produce weapons-grade plutonium succumbed to operator incompetence and suffered a meltdown. Because it lacked secondary containment found on every CANDU including Douglas Point, a hydrogen explosion resulted in a large radiological release.

Everything stopped.


Construction at Darlington ceased. The world scrambled to reconcile with what happened and the entire nuclear industry, even here in Canada, despite sharing absolutely nothing in common with the Soviet RBMK design at Chernobyl, went back to the drawing board. They had to prove it couldn't happen here. While this was taking place time, and debt, marched on. Interest rates were soaring, the cost of the Darlington project, despite no actual work being done, was increasing rapidly. By the time the first unit entered commercial service 10 years had passed, a far cry from the 6 years shovel to breaker for the Bruce A units. This led to a construction cost of $14.4 billion. Darlington was a white elephant and thus the B plant was never built.


Darlington was the most mature design in the CANDU fleet. It was, at the time, the epitome of CANDU engineering. Deep water inlet and outlet diffusers, better heat transfer loop design, higher power output...etc. The list goes on.

We never exported CANDU 9.


After Chernobyl the global nuclear industry never recovered. AECL managed to land a few CANDU 6 sales but the 9 went nowhere and it was abandoned. Darlington is the only operating example of the CANDU 9.


Since then, AECL managed to partner with China on the Enhanced CANDU 6, which the Chinese had interest in because as had been demonstrated in various tests in Canada, the high neutron economy and inherently flexible nature of the deuterium pressure tube design meant that the CANDU could run on a huge variety of fuel combinations, something other reactors were simply incapable of. China's intention for the units at Qinshan was for them to run on the used fuel coming out of their neighbouring American-style light water units, and they do.

When AECL failed to secure the construction contract for the ACR1000's that were supposed to be built at Darlington B in the 20-teens it was sold off to SNC Lavalin. Ontario had screwed itself with insanely generous fixed-rate contracts for industrial wind and even more highly subsidized solar projects. This drove rates through the roof, leaving no consumer tolerance for a 25 billion dollar nuclear development.


As OPG continues to refurbish Darlington, now on Unit 3, and Bruce Power refurbishes the remaining 6x Bruce units while providing the 2nd lowest cost generation in the province I think it important to note that these things are not widely celebrated. Ontario has one of the lowest emissions grids in the world and that's mostly due to our massive nuclear fleet. Who knew that before reading this?


Today, as Darlington Unit 1 soldiers on after setting the world record for continuous operation at 963 days of almost zero emissions generation we should be proud of what that stands for: a Canadian design built by Canadians for Canadians for the purpose of peaceful power production. Operated by your fellow Ontarians providing valuable employment in all corners of this massive province and, along with hydro, being one of the only things keeping your rates down after the disaster that was the GEA. This is something we can, and should, all be proud of."

Christopher Adlam