Radiation-Hardened Cameras Aid in Nuclear Generator Refueling
Brent D. Johnson
During a refuel outage of a nuclear power plant, all of the fuel assemblies in the reactor core are either replaced or moved to other locations in the core. Each of these fuel assembly moves, which may number more than 1000, must be verified by technicians who view the process with binoculars from the refueling bridge. The process not only is difficult, but also increases the potential for radiation exposure.
A fuel assembly inspection system mounted in the reactor vessel examines fuel bundles.
Ed McVey, senior staff engineer for Exelon Generation's Nuclear Fuel Management organization, explained that, if the bundles are not loaded correctly, the reactor could fail to operate as designed. The reason for this is that each of the 764 assemblies in the core has unique properties.
To ensure the correct placement of the bundles, R.O.V. Technologies has adapted two Sony (330T) high-resolution charge-injection-device 24X cameras that are mounted on robotic arms on each side of the nuclear reactor. The cameras have been reconfigured to meet the demands of the harsh environment within the reactor core, where they are exposed to hundreds of rem (roentgen equivalent man) an hour for a week or more at a time.
Some of the components were moved to the back of the cameras or to the control console to shield them from the radiation. The cameras also are mounted in a pressurized, watertight housing to make them more radiation-tolerant.
The two telescoping cameras are mounted directly onto a large bolt on the reactor vessel, and two 500-W underwater lights provide the illumination. The cameras are 180° apart and reach across half the distance of the core. They can boom down and can swivel to the right or the left. Wireless technology sends the camera signal to two high-resolution monitors.
R.O.V.'s customers wanted to use color imaging for the new fuel inspection system that mounts directly on the reactor. "It's always an advantage to have color when looking for orientation, debris and proper seating," said Don Butler of R.O.V. "Sony was the highest-resolution camera out there."
The new method for performing the fuel assembly verification is much more efficient, taking less than five minutes of critical outage time and saving Exelon hundreds of thousands of dollars per outage.
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