One truism of nuclear reactors is that you really don't want to be next to one. Unfortunately, reactor cores need to be inspected and maintained, which means teams of workers going inside the containment vessel. It's an operation that's not only hazardous, but expensive and time consuming. In an effort to make such inspections safer, cheaper, and faster, GE Hitachi Nuclear Energy has developed the Stinger; a free-swimming, remote-controlled robot that replaces humans for cleaning and inspecting reactor vessels.

Nuclear reactors are not the easiest thing in the world to inspect. Immersed in a pool of water for coolant and to moderate the nuclear reaction, the reactor and the water vessel that contains it requires periodic cleaning and inspection to ensure that it's safe and operating efficiently. The trouble is, such inspections are expensive and surprisingly labor intensive.

Part of the problem is that special bridges need to be hauled in and installed over the pool, so workers can walk out with poles tipped with tools and instruments to do their job. This operation is not only burdensome, but it also exposes the team to radiation, which the industry obviously tries to avoid, and interrupts the on-going operations to remove and replace spent fuel rods.

The GE Hitachi Stinger is designed to simplify the whole inspection task by replacing the team and the bridge with a free-swimming robot that looks a bit like a gigantic mechanical seahorse. Instead of using a rail or a track, the robot swims about using an advanced camera and remote positioning technology while being controlled by an operator in a tent away from the radiation area. This not only removes the need for a bridge, but also allows refueling operations to continue uninterrupted.

"Stinger performs inspections of welds within nuclear reactors. It remotely operated and swims to these welds within this highly irradiated area," said Jerry Dolan, Senior Tooling Manager at GE in an interview with Gizmag. "Stinger uses a hydrolaser to blast welds with water before it shoots HD video of the weld. This video is then beamed near real-time to Nuclear Regulatory Commission-approved inspectors at our global Center of Excellence in Wilmington, NC, where they are analyzed.

"Stinger literally replaces eight people standing on the bridge of the reactor lowering cameras and brushes with ropes and pulleys. It is much faster and more accurate than previous methods while also significantly reducing radiation dose."

Dolan went on to explain that the robot uses multiple thrusters to navigate, and depth, pitch, and roll sensors stabilize and position itself.

In a separate interview, John Lizzi, Manager of the Distributed Intelligent Systems Laboratory at GE Global Research, cites the Stinger as one example of the company's service robotics strategy. The robot been in operation for 1½ to 2 years, and in the future it may be upgraded to carry out maintenance and repair operations as well as inspections.

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