OPG gets a 360 degree view inside nuclear reactors
Nuclear power plants have been operating in Canada since the early 1970s. According to the Canada Nuclear Safety Commission there are about seven currently in operation across the country, using uranium as fuel and heavy water as a coolant and moderator.
But due to high radiation levels, no one has ever been able to inspect critical components inside the reactors, until now.
MacDonald, Dettwiler and Associates Ltd. (MDA), a Richmond, BC-based solutions provider, built a robotic arm for Ontario Power Generation (OPG) to inspect the inside of its Calandria Vault at the Pickering nuclear station.
This robot gives OPG its first close-up, 360-degree view of steel components and structural welds deep inside the concrete walls of the reactor.
Lawrence Gryniewski, the MDA systems engineer that worked on the reactor campaign said OPG was looking for a company with a good engineering background, and since MDA has expertise in space application solutions, it won the contract.
“When we deliver a system, it’s the whole system not just the hardware,” says Gryniewski. “We started with the hardware itself and conceived what it would go through, we went through development, testing and validation to prove that this piece of hardware would do exactly what we wanted and reliably.”
But the hardware is just one part of the project. MDA also developed the electronics to run the 14-metre robotic arm, developed the software for it and trained the operators how to use it.
It’s one thing to get a robotic arm into a reactor, but it’s entirely another to get it back out.
Gryniewski says one of the biggest challenges was squeezing the robotic arm through a tiny opening and reaching 14-metres away to some of the components.
“We needed a high level of optimizing the system structure and the system components to be able to get in there. You have to go through structural analysis to ensure your components are strong enough,” says Gryniewski. “And you have to go through kinematic analysis to make sure it can actually reach from your starting point to the target without contacting any components.”
And since there are high levels of radiation within these reactors, parts of the arm need to be able to be changed in order to complete the inspection. The cameras, in particular, used to capture images inside the reactor are highly affected by the radiation.
“Some of the cameras are high resolution and some aren’t,” he explains. “The cameras that survive the longest are essentially the older version of TV cameras with Vidicon lenses [that were in style about 25 years ago].”
The lenses are robust and have no problem operating in a nuclear environment. But the new cameras, that capture higher resolution images, are more susceptible to radiation and need to be changed.
Controlled from a remote workstation, the operator controls the highly dexterous robotic arm from a computer console where he can program auto-scripted modes and use joysticks to drive the joints of the arm.