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The IWTU auger-grinder before its redesign.
The IWTU auger-grinder after its redesign.
The auger-grinder is an enclosed metal shaft with blades that break up solid product greater than a half inch in diameter so it can be successfully transferred from IWTU’s primary reaction vessel to vessels that hold the product before it’s added to storage canisters. The auger-grinder is being re-engineered after malfunctioning during prior IWTU waste simulant processing campaigns.
Engineers and operators have completed three simulated waste treatment campaigns at IWTU, converting more than 100,000 gallons of liquid waste simulant to a granular solid. The simulant closely resembles the 900,000 gallons of remaining sodium-bearing waste in the tank farm at the Idaho Nuclear Technology and Engineering Center. That waste is awaiting treatment to allow the eventual closure and grouting of the remaining underground storage tanks.
In recent testing of the second-generation auger-grinder, engineers with Fluor Idaho, EM’s contractor, were able to replicate the conditions that caused the machine to plug and seize during simulant testing. The new design features a modular approach, which allows replacement of the individual components — such as cutting blades, clarifiers and bearings — in the working end without having to replace the entire auger-grinder assembly. The new design also includes multiple sets of varying teeth and blade configurations that will be tested to determine the combination of blades and teeth that best satisfy the performance criteria.
Testing over the next two months will involve placing heating blankets on the auger-grinder to bring it up to 1,200 degrees Fahrenheit. Steam will be applied to simulate the conditions the auger-grinder experiences during IWTU operations. Testing will also determine whether the openings at the bottom of the auger-grinder allow an adequate flow of converted material to the waste canisters, a problem the previous model experienced during simulant campaigns.
Following testing, the revised auger-grinder will be installed in the plant for the next simulant run. The final version of the auger-grinder for actual plant operations will be fabricated out of a metal alloy to withstand long-term high temperatures and corrosive environments.