The US Department of Energy’s Office of Environmental Management (EM) said on 25 May that its Office of River Protection (ORP) and its tank operations contractor Washington River Protections Solutions (WRPS) were an important step closer to treating tank waste at the Hanford Site in Washington state following the installation of two critical pumps and the completion of equipment and worker testing.

The Hanford Nuclear Reservation, established during World War II is the subject of a decades-long, multibillion-dollar clean-up effort. |It is the most contaminated site of radioactive waste in the USA. While operational, it produced about 66% of the plutonium used for US nuclear weapons. A series of massive underground storage tanks ranging in capacity from 55,000 gallons to more than 1,000,000 gallons were constructed to hold the wastes from plutonium production.

They are located throughout Hanford’s 200 Area in a 18 “tank farms”, each comprising from two to 16 tanks. There are 149 original single-shell tanks and 28 double-shell tanks which were built later. They contain liquids, gases, semi-solids, and solids. All of the liquid that can be safely pumped out of the single shell tanks and transferred into double shell tanks has taken place. Work now centres on transferring the solid and semi-solid wastes into the double shell models.

In early May, crews installed a pair of pumps in tank AP-106, the tank that will feed waste treated by a Tank-Side Caesium Removal (TSCR) system to the Waste Treatment and Immobilisation Plant where it will be vitrified, or immobilised in glass. Completion of construction of the TSCR system at Hanford is an EM 2021 priority.

“This is an exciting and historic time for Hanford,” said Janet Diediker, federal project director at ORP. “We’re just months away from being able to operate our caesium removal system. As we make progress installing equipment and training employees, we get closer to vitrification and reducing the risk this waste poses to the environment.”

TSCR is nearly ready for operation. During the past month workers ran water through the system to simulate tank waste, giving crews some hands-on training and the opportunity to validate operational procedures.

“With each week, we were able to process more simulated waste as we improved efficiency,” said Matt Cuttlers, TSCR operations manager for WRPS. “This provided experience for our operators, and we received great support from commissioning, engineering, and maintenance.” Workers also practiced changing out the TSCR ion-exchange columns, which will remove caesium from tank waste. During waste treatment, workers will change out the columns approximately once a month.

“This was a big team effort,” said Mario Servin with WRPS tank farms projects engineering. “It gives us a lot of confidence when field workers have the opportunity to practice the procedures. They give us feedback so we can make improvements with each practice run.”

Several members of the team that will operate TSCR are second-generation Hanford workers. “It’s been a long time coming, but it’s exciting to know that we’re on the cusp of treating the waste,” said nuclear chemical operator Darin Wood, a 20-year Hanford veteran whose father worked at the site for nearly 40 years.