MacDonald, Dettwiler and Associates Ltd. (MDA), a Richmond, BC-based provider of advanced information systems and robotics has entered another realm: the inside of Ontario Power Generation’s (OPG’s ) Calandria Vault at the Pickering nuclear station.
MDA’s nuclear robot arm reaches inside OPG’s Calandria Vault.
Nuclear power plants have supplied communities across Canada with electricity since the 1970s and according to the Canada Nuclear Safety Commission there are currently seven in operation using uranium as fuel with heavy water as a coolant and moderator. But it hasn’t been possible to inspect critical components inside the reactors because of high radiation levels – until now.
MacDonald, Dettwiler and Associates Ltd. (MDA), a Richmond, BC-based provider of advanced information systems and robotics that perform tasks in such diverse environments as outer space and the human brain, has entered another realm: the inside of Ontario Power Generation’s (OPG’s ) Calandria Vault at the Pickering nuclear station.
This robotic arm gives OPG its first close-up, 360-degree view of steel components and structural welds deep inside the concrete walls of a reactor’s radioactive chambers.
Lawrence Gryniewski, the MDA systems engineer who worked on the reactor project, says OPG was looking for a company with a good engineering background.
“When we deliver a system, it’s the whole system not just the hardware,” says Gryniewski.
The process began with an analytical CAD model to demonstrate how hardware would work inside a reactor and then the model was taken through a series of verification tests.
MDA also developed the electronics to run the 14-metre robotic arm, the software (essentially the same used by a robotic arm that performs delicate brain-surgery), and it trained the operators.
Of course, it’s one thing to get a robotic arm into a reactor, and quite another thing to get it back out.
Gryniewski says one of the biggest challenges was squeezing the arm through a tiny opening and reaching some of the components 14-metres away.
“We needed a high level of optimizing to get in there. You have to go through structural analysis to ensure your components are strong enough. And you have to go through kinematic analysis to ensure [the arm] can actually reach the target from your starting point without contacting any components.”
Since radiation levels within these reactors is so high, parts of the arm must be changed to complete the inspection. For instance, cameras used to capture images inside the reactor are greatly 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 an older version of TV cameras with Vidicon lenses [in style about 25 years ago].”
The lenses are robust and operate easily within a nuclear environment, but the new cameras that capture higher resolution images are more susceptible to radiation and need to be changed more frequently.
Working from a remote workstation, the operator controls the dexterous robotic arm from a computer console where he can program auto-scripted modes and use joysticks to drive the joints of the arm.
“The mechanical system has 11 degrees of freedom, meaning 11 joints,” says Gryniewski. “Five of those joints are what we consider to be the delivery system at the end of the arm, which has six degrees of freedom.”
Several scripted control modes handle the routine task the robot is expected to complete. “We can preplan that and rehearse it in a mock up to make sure we’re not getting close to sensitive components and that there’s no danger of collision,” says Gryniewski.
With its technology now being put to practical use in OPG’s Calandria Vault, MDA now has the capability to extend its reach and its grasp beyond even the USS Enterprise’s star trekking capabilities, to go where no man has been able to go before.