Underwater craft could help maintain and secure nuclear reactor cores

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On November 10, 2003

The core of a nuclear reactor is often referred to as no-man’s land because it sits under at least 25 feet of water and is so radioactive that no living thing should go near it. But a researcher at UMR is developing a water-submersible craft to safely inspect the core to determine whether maintenance or repair is needed.

Dr. Akira Tokuhiro, assistant professor of nuclear engineering and director of the UMR Reactor, is working on a water-submersible craft with a radiation-resistant camera that journeys to the center of a reactor and records images of the core’s components. This project’s goal is to help maintain and secure the nation’s nuclear reactor facilities, he says.

"Because the radiation level near the core is lethal, we cannot put on a wetsuit and go down 25 feet into the pool and examine the reactor components," Tokuhiro says. "The submersible craft with the camera can withstand a high level of radiation and functions as an in-service inspection device (ISI)."

Initial tests have already been done with the submersible craft in the UMR swimming pool. "Within the next year, we hope the submersible will be fully operational and it will go down into the reactor core and take some images of the components," says Tokuhiro.

The images recorded by the device can be studied to determine the condition of the reactor components, and the kind of maintenance that may be required. According to Tokuhiro, reactor components are in many ways vulnerable to corrosion despite the high purity of the water. "Many nuclear reactors are water-cooled or are boiling water, so all the components are either in contact with water or steam," says Tokuhiro. "If you keep your water low in impurities, the reactor components are less likely to corrode, but it’s very difficult to keep the water pure. Now we will have some means for in-service inspection of reactor components."

UMR’s reactor was built in 1961 and Tokuhiro says the facility is in good condition, but some of the components have been under water for 40 years. "The grade of aluminum that we have here has been used at many other research reactor facilities and it has held up extremely well, and all of the remaining reactors are about 40 years old," he says. "We don’t have any doubts that it’s in good condition, but we would like to confirm it visually."

Many UMR students are involved in this project and Tokuhiro says they have made all the difference. "These kinds of projects really bring together all the students. It’s not only nuclear engineering students, but also computer engineering, electrical engineering, mechanical engineering, and so on. It’s become a multidisciplinary team," says Tokuhiro.

He says that the submersible craft is one of several robotic projects at the UMR reactor. Collectively called Reactor Robotics Development and Deployment, or R2D2, the projects focus primarily on security issues for the facility. Tokuhiro is driven by the fact that "we should educate engineers to know about security, because in the post-9/11 environment security engineering will become a new field of employment. We need to start producing engineers that know about security issues."

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On November 10, 2003. Posted in Research