HANFORD — Hanford workers have finished installing the major components of a mobile arm retrieval system into an underground tank of radioactive waste for the first time.
The new robotic arm, called MARS, is expected to be ready to start retrieving radioactive waste from Tank C-107 in mid-September.
If it works as expected, it will be “totally a game changer,” said Scott Sax, manager of single-shell tank retrieval and closure for Washington River Protection Solutions.
Hanford has 142 single-shell tanks, some of which have leaked in the past, that need to have waste retrieved and transferred to 28 sturdier double-shell tanks until the waste can be treated.
But getting high level radioactive waste out of the enclosed, underground tanks through 12-inch risers has been a challenge. Multiple technologies have been needed to retrieve waste from many of the tanks worked on so far, particularly as retrieval gets to the hard waste at a tank’s bottom.
Hanford officials are expecting MARS to operate more quickly and efficiently, tackling not only the bulk of waste but also the difficult waste at the bottom of tanks.
It’s by far the largest retrieval technology inserted into an underground tank and required a 55-inch hole to be cut into Tank C-107 to install a 42-inch riser.
The new riser was installed in December, and tank farm workers installed MARS in pieces through the riser Friday and Tuesday.
Last week, the 25-foot mast and robotic arm were installed and Tuesday, workers put in the waste pump, the hose support and then the final shielding block.
“The job went perfect,” Sax said. “There was no contamination, no radiation spread.”
Workers had completed a dry run at Columbia Energy and Environmental Services in Richland to practice in a nonradioactive environment. The company managed development of the robotic arm’s design.
The mast, which is inserted from the top of the tank to its bottom, has a carriage that can be raised or lowered to position a telescoping arm that can rotate 360 degrees. When it unfolds and lengthens, it can reach 40 feet total. Not only does it have an “elbow” midway to make it more flexible, but the “wrist” above the collection of the tools it holds also can move.
The sluicing tools on the MARS that will be used in Tank C-107 include a water cannon, high pressure nozzles and fan nozzles, each adding options to break up waste or sweep it toward a pump at the bottom of the mast.
In testing, the robotic arm has been able to break up and move substances that mimic the three types of tank waste that give Hanford workers trouble. Tanks may have sludge the consistency of peanut butter, a heavy sand- or gravel-like material and a hard layer of waste, comparable to low-strength concrete, that has to be broken up.
Tank C-107 has about 267,000 gallons of radioactive waste, which is expected to include sludge and a bottom layer of hard, gravel-like material.
The next two months will be spent testing and training on MARS before waste retrieval starts at Tank C-107.
“Ecology looks forward to seeing how this technology performs,” said Dieter Bohrmann, spokesman for the Washington State Department of Ecology, which regulates the Hanford tank farms. “Innovative technology development, such as MARS, is going to be important as retrieval continues for years to come.”