The IWTU will use a fluidized bed steam-reforming process to treat the remaining 900,000 gallons of liquid radioactive waste from the Idaho Site’s underground tank farm.
The IWTU’s primary reaction vessel, the Denitration Mineralization Reformer (DMR), contains billions of tiny beads kept in a fluidized state with the help of superheated gases. Liquid waste enters the fluidized bed, coating the beads like the formation of pearls. The waste product is transferred to stainless steel canisters and ultimately concrete vaults.
Fluor Idaho, EM’s Idaho Site cleanup contractor, has enlisted Hazen Research in Golden, Colorado to conduct testing to correct problems with the DMR involving fluid bed stability and a wall-scale formation resembling bark on the DMR’s interior walls.
Testing proved that controlling the operating conditions — including the size of liquid droplets of simulated waste injected and the size of the resulting solidified waste particles in the vessel — reduces the wall-scale formation and improves the fluid bed stability.
Testing showed that introducing carbon dioxide gas into the bottom of the vessel minimizes the formation of clumps resulting in the bed instability and wall-scale formation.
Researchers are also examining the chemical properties inside the scaled-model reaction vessels as the liquid is converted into a granular solid. Increasing the conversion speed decreases the likelihood of the wall-scale formation.
“During prior demonstration runs at IWTU, the formation of wall scale became a problem because the cause was unknown and it appears to interfere with the fluidization process inside the DMR,” said DOE-Idaho project manager Kevin O’Neill. “The testing at Hazen has been beneficial because they’ve been able to significantly reduce, if not virtually eliminate, this problem.”
Testing will continue for several months, providing valuable input into the next IWTU demonstration with simulated waste planned for later this year.
Fluor Idaho is integrating the test results with DMR process modeling and laboratory-scale work performed by the National Energy Technology, Idaho National, and Savannah River National laboratories to establish necessary modifications and operating parameters for the demonstration and ultimately operation of the plant.