Underground tank vitrification: Engineering-scale test results

Abstract

Contamination associated with underground tanks at US Department of Energy sites and other sites may be effectively remediated by application of in situ vitrification (ISV) technology. In situ vitrification converts contaminated soil and buried wastes such as underground tanks into a glass and crystalline block, similar to obsidian with crystalline phases. A radioactive engineering-scale test performed at Pacific Northwest Laboratory in September 1989 demonstrated the feasibility of using ISV for this application. A 30-cm-diameter (12-in.-diameter) buried steel and concrete tank containing simulated tank sludge was vitrified, producing a solid block. The tank sludge used in the test simulated materials in tanks at Oak Ridge National Laboratory. Hazardous components of the tank sludge were immobilized or removed and captured in the off-gas treatment system. The steel tank was converted to ingots near the bottom of the block and the concrete walls were dissolved into the resulting glass and crystalline block. Although one of the four moving electrodes froze'' in place about halfway into the test, operations were able to continue. The test was successfully completed and all the tank sludge was vitrified. 7 refs., 12 figs., 5 tabs.