Robotic arm close to seeing use

Hanford's newest and largest-by-far robotic arm system should be emptying radioactive waste from an underground tank this summer.

The Mobile Arm Retrieval System, or MARS, is expected to be installed in Hanford Tank C-107 as soon as the end of March, said Chris Kemp, Department of Energy project director.

"It is innovative," Kemp said. "It is game-changing technology, and it is going to allow us to accelerate retrieval and become more efficient at retrieval."

On Thursday, Hanford workers were training on the system at Columbia Energy and Environmental Services in Richland.

About 25 operators are expected to be trained to allow around-the-clock work with the robotic arm and prepare for its use at tanks beyond C-107.

The robotic arm can be raised or lowered in the tank, rotated 360 degrees and unfolded and lengthened to reach 40 feet to the tank sides or bottom. It can be fitted with different attachments, but its first use will be a water cannon, high pressure nozzles and fan nozzles to break up waste and sweep it toward a pump at the center of the tank.

In earlier technology, sluicing nozzles were used near the roof of the enclosed underground tanks, but MARS allows the spray to get close to the waste.

It might seem like an obvious improvement, but getting robust equipment into the underground tanks has been the problem.

Previous technology has been lowered into the tanks through 12-inch openings dating to as early as World War II to get waste into the tanks, not take the waste out.

Washington River Protection Solutions has taken a new approach, showing it safely could cut a new 55-inch-diameter hole into a waste tank in December. The larger opening, which was cut in Tank C-107, will allow the larger robotic arm to be inserted in the tank.

"We're encouraged by this technology," said Dieter Bohrmann, spokesman for the Washington State Department of Ecology, the regulator for Hanford's tanks. "We think it will be effective in this tank."

Tank C-107 has about 267,000 gallons of radioactive waste, most of it sludge the consistency of peanut butter. Beneath the sludge is hard material similar to rock or gravel.

Tank C-107 was picked for sluicing with MARS because it is not known to have leaked in the past. Other tanks might be emptied with a vacuum attachment added to the robotic arm to limit the liquid added to the tank during waste retrieval.