Staff at US nuclear utility Entergy have developed a remote-controlled truck to reduce worker radiation exposure in applications where health physics, operations or engineering employees are required to perform simple visual inspections.
Entergy’s remote controlled truck
“We have used the robot recently to perform inspections for leaks in our steam-affected areas,” said Tom Baccus, RP support supervisor at River Bend nuclear power station in Louisiana. “For a boiling water reactor the steam-affected areas are subject to high levels of N16 gamma rays during operations. This results in high-dose fields in these areas. We used the robot in two such areas recently. One was our condenser bay. We attached a wireless telemetry device to the robot so we could monitor the dose while performing the inspection. The inspection was performed remotely using the camera on the robot. Based on the telemetry, 301 mrem was received by the robot during the inspection. We also sent the robot into a main steam relief bay to perform another leak inspection, which probably saved another 20 to 40 mrem exposure.”
Projected radiation savings are cumulative. Based on estimation from several recent uses, a one-time savings in exposure was about 50 mrem. Assuming approximately one use every other month, this would correspond to approximately 300 mrem per year at one station alone.
The device is a wheeled robot with high-resolution visual capabilities, similar in concept to machines developed for military uses, but uniquely modified for nuclear power plants, with an off-the-shelf video camera (with tilt, pan and zoom), lights, and a 5lb payload bay for equipment such as a radiation monitor. The joystick controls – modified from an RC airplane controller – are connected by a 150ft tether to the robot.
The only decontamination concern with the robot are its rubber wheels; “we don’t intend to run it under dripping pipes,” says Charles Turk, Entergy leader, R&D/university partnership in the company’s corporate innovation group. He said that instead of cleaning the wheels, some users are considering leaving the robot in contaminated environments, or buying an extra set of wheels.
He said that the robot can clamber over one-inch high doorsills without a problem, but a 3-inch-high pipe would probably block its travel.
Entergy’s Grand Gulf nuclear station in Mississippi is also planning to use it. “We are currently determining the level of training required to operate it through our training department,” says Grand Gulf’s Tom Trichell. “Our plans for future use deal primarily with performing inspections (steam leaks, air in leakage into our off gas system) for planned or emergent-type issues associated with hazard area entries. The robot could also be used to assess environmental hazards associated with spills.”
Entergy has ordered about 10 robots in the latest design; they are currently being tested at Entergy’s Grand Gulf and River Bend nuclear power stations. It also ordered one unit of a previous version.
The California Mechatronics Centre, affiliated to California State University (Chico) built the robot. A new version is currently under development that will have a different suspension, more robust battery and wireless ethernet connectivity, according to mechatronic engineer Jason Coates.
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1. Four wheel drive, four wheel steering |
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