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The Integrated Waste Treatment Unit at DOE's Idaho Site.
IDAHO FALLS, Idaho – DOE recently convened a “Chemistry Summit” of scientific experts to aid its efforts to safely and effectively start up the Integrated Waste Treatment Unit (IWTU).
The summit’s team of chemists from the Idaho Cleanup Project, Idaho National Laboratory, and EM’s Savannah River National Laboratory in South Carolina, and industry experts, developed recommendations to address technical issues as IWTU undergoes startup testing with a waste simulant prior to beginning operations with actual radioactive material.
“We are finding and fixing the problems,” said Idaho EM Manager Jack Zimmerman. “The purpose of the testing and commissioning phase is to identify and fix problems without the hazardous and radioactive constituents. We have made a lot of progress, and have fixed most of the problems identified, but we still have some work to do. We continue to encourage the engineers and workers at the IWTU to propose and test new and innovative ways to operate the facility more safely and efficiently.”
IWTU is a first-of-a-kind facility built to treat 900,000 gallons of radioactive liquid waste at the DOE Idaho Site. The facility will use a steam reforming process to treat the liquid waste and convert it into a granular solid, which is transferred to stainless steel canisters for safe storage and eventual disposal. DOE is taking a deliberative approach to starting up the IWTU to ensure any technical issues that could negatively impact the facility are identified and resolved before beginning radioactive waste treatment operations.
To date, DOE has conducted three campaigns at the IWTU using a waste simulant to help identify potential issues and gain operating experience. The simulant closely models the chemical makeup — minus the radioactive constituents and mercury — of the liquid waste to be processed. Testing performed to date shows that the prime objective of the IWTU — safely converting a liquid into a solid waste form — can be successfully accomplished. As a result of the simulant campaigns, significant progress has been made in equipment and process reliability, and the IWTU is operating in a more stable fashion as the Department prepares to introduce radioactive waste.
The latest simulant campaign, conducted in late 2015, was intended to help DOE evaluate fixes put into place following the previous simulant campaigns, such as changes to the fluidized bed that is part of the treatment process; as well as demonstrate stable plant operations. The third simulant run provided IWTU operators with their longest opportunity to date to run the facility and learn more about it. Inspections performed after the simulant run found a bark-like material on the internal surface of the facility treatment vessel, as well as some equipment erosion issues. Notably, the bark-like material found in the treatment vessel after the third simulant run was not as extensive and was easier to remove than similar material found after an earlier simulant campaign.
“The plant is operating in a much more stable fashion than in earlier simulant runs,” said Zimmerman. “This complex, first-of-a-kind facility requires testing and modifications that normally happen during the commissioning phase of a project like this. We remain focused on meeting our commitment to the state of Idaho, and the measured, methodical, deliberative approach to starting up IWTU is necessary so that when we do begin treating radioactive waste, we are confident we are doing it safely and efficiently.”
At the summit held in Idaho Falls, the chemists and process experts discussed potential solutions to the bark-like formation and new erosion issue. The group identified potential equipment and process modifications to address the chemistry and fluidization issues. Some of these solutions can be implemented in the near term, while others will require additional testing.
The near-term path forward is to implement some of the team’s recommendations during the next planned simulant run, which is expected to get underway this spring. DOE is working to meet an agreement with the state of Idaho to begin actual waste processing at IWTU by Sept. 30, 2016.