Construction on the 53,000-square-foot Integrated Waste Treatment Unit started in 2007.

Cleanup crews are finishing several improvements to the Integrated Waste Treatment Unit following a 50-day demonstration of the facility.

The IWTU was built to treat 900,000 gallons of liquid radioactive waste from nearby underground waste tanks that accepted rinse water and other effluents from historic spent nuclear fuel reprocessing. This was supposed to have been done years ago, but has been delayed due to technical problems, causing the U.S. Department of Energy to miss milestones for the 1995 Settlement Agreement between Idaho and DOE that sets deadlines for waste removal.

Testing there has ramped up this year, and so far the facility has treated approximately 225,000 gallons of liquid simulant in six demonstrations, cleanup contractor Fluor Idaho said in a news release Tuesday. The last simulant run, which converted more than 63,000 gallons of liquid simulant to a dry, granular solid, was finished in June. Now, crews are working on a few other projects before a final test run and then actual waste treatment begins.

“The takeaway from this and the previous 30-day demonstration runs is that the IWTU facility and its steam reforming technology works for liquid waste treatment,” Archie Benner, IWTU nuclear facility manager with Fluor Idaho, said in a statement. “The plant operated as designed and we’ll now focus on three key process improvements that are necessary to progress to the next level.”

The IWTU’s filters became plugged with fine particulates in the last two demonstrations. Fluor picked new filters after testing at the Colorado facility Hazen Research, and further testing will refine operating parameters and installation requirements for the new filters.

IWTU engineers are working now to test a robotic arm for decontaminating stainless steel canisters that would be filled with treated waste once IWTU begins operating, Fluor said in a news release. Testing also continues on a new system to let operators decontaminate a cell, vessel, and piping without disassembling and cleaning them by hand. A sump system would transfer the liquid decontamination solution from the cell to be processed.

And, crews are working with a mock-up of the Denitration Mineralization Reformer, the IWTU’s primary reaction vessel, to test the ability to enter it and replace its internal parts once radioactive waste treatment begins. A mock-up also has been built for the process gas filter and off-gas filter vessels to test removal and replacement of filter bundles and associated equipment in a radiological environment.