In Situ Verification And Monitoring Of Stabilized Trwmixed Waste

During 1997, MSE Technology Applications, Inc. (MSE) in cooperation with the U.S. Department of Energy<br>(DOE) Office of Science and Technology, Subsurface Contaminants Focus Area and the Idaho National<br>Engineering and Environmental Laboratory (INEEL) tested the feasibility of in situ waste stabilization for either<br>encapsulating waste for in situ disposal or as a step in the process of contaminated retrieval with improved<br>contamination control. In situ stabilization was accomplished by encapsulating the waste in a monolith constructed<br>by injecting grout at high pressure into the subsurface. A vital part of this test was the confirmation that the<br>monolith had encapsulated the waste and evaluate the internal integrity of the monolith (detect voids, poorly grouted<br>zones, fractures, . ..).<br>Verifying the internal integrity of the emplaced monolith can be accomplished any number of ways, including<br>destructive examination of the monolith (i.e., coring and excavating). Although effective, these methods are not<br>often preferred, as the spread of contamination may be significant. As a result, a method to nondestructively<br>examine these monoliths was investigated.<br>Monoliths were emplaced at the INEEL Radioactive Waste Management Complex (RWMC) as part of an In Situ<br>Stabilization Treatability Study. Cold and Hot Demonstration sites were nondestructively examined using seismic<br>geophysical methods. These methods require limited access to the monoliths. Data obtained from the seismic<br>measurements were used to generate 3-dimensional models of the grout monoliths. Results, presented in this paper,<br>are expected to show that borehole seismic methods are an effective means of nondestructively imaging the grout<br>monoliths.