The processing and downblending of uranium-233 for disposal has resumed at Oak Ridge National Laboratory, following a pause in operations due to the COVID-19 pandemic, the Department of Energy announced on October 20. Removal and disposition of the U-233 is one of the DOE Office of Environmental Management’s highest priorities at the site, as stated in its strategic vision released earlier this year.
The project is removing a significant risk by eliminating the inventory of highly enriched fissile material stored in Building 3019, the world’s oldest operating nuclear facility, according to the DOE. Employees, known as fissile material handlers, use shielded gloveboxes to dissolve U-233 into a low-level form so that it can be mixed with grout for safe transportation and disposal. The material dates back decades and was originally pursued as a fuel for reactors; however, it did not prove to be a viable option.
Upgrades: The DOE’s Oak Ridge Office of Environmental Management (OREM) and its contractor Isotek worked collaboratively during the operational pause to install upgrades and identify and implement a number of methods to ensure employee safety.
At the restart of U-233 processing, employees went through retraining to ensure that they were prepared to handle the radioactive material. They were also trained on new procedures that incorporated COVID-19-related safety precautions.
During the suspension of work, a new filter was added to catch undissolved particles of U-233 as the material is being processed. This filter is intended to prevent undissolved particles from plugging up transfer lines, resulting in handlers spending less time using the gloveboxes.
Another addition is an extended waste transfer line. This new line extends from the glovebox to a negative pressure area so that waste can be transferred directly to a safe zone. Before this, employees transferred waste to a drum and then moved the drum to the safe zone.
Hot cell work: In conjunction with the restart of glovebox processing, work is under way to enable hot cell processing, which will be needed to handle high-dose U-233 canisters. Entry tubes are being fitted for remote manipulators that will handle material inside the hot cells. An entire floor of Building 3019 has been reconstructed for an air pallet that will be able to move 30 tons of waste after it has been processed for disposal.
Hot cell processing is expected to begin next year, according to the DOE. Until then, Isotek will continue addressing the low-dose inventory using gloveboxes.
Thorium extraction: Last year, OREM, Isotek, and TerraPower announced a public-private partnership that makes use of the U-233 inventory before it is disposed. Isotek extracts thorium before the material is processed into a disposal-ready form. TerraPower, the Bellvue, Wash.–based company known for its Traveling Wave Reactor design, is using the extracted thorium to support cancer treatment research.