Historical hydronuclear testing: Characterization and remediation technologies

This report examines the most current literature and information available on characterization and remediation technologies that could be used on the Nevada Test Site (NTS) historical hydronuclear test areas. Historical hydronuclear tests use high explosives and a small amount of plutonium. The explosion scatters plutonium within a contained subsurface environment. There is currently a need to characterize these test areas to determine the spatial extent of plutonium in the subsurface and whether geohydrologic processes are transporting the plutonium away from the event site. Three technologies were identified to assist in the characterization of the sites. These technologies are the Pipe Explorer{trademark}, cone penetrometer, and drilling. If the characterization results indicate that remediation is needed, three remediation technologies were identified that should be appropriate, namely: capping or sealing the surface, in situ grouting, and in situ vitrification. Capping the surface would prevent vertical infiltration of water into the soil column, but would not restrict lateral movement of vadose zone water. Both the in situ grouting and vitrification techniques would attempt to immobilize the radioactive contaminants to restrict or prevent leaching of the radioactive contaminants into the groundwater. In situ grouting uses penetrometers or boreholes to inject the soil below the contaminant zone with low permeability grout. In situ vitrification melts the soil containing contaminants into a solid block. This technique would provide a significantly longer contaminant immobilization, but some research and development would be required to re-engineer existing systems for use at deep soil depths. Currently, equipment can only handle shallow depth vitrification. After existing documentation on the historical hydronuclear tests have been reviewed and the sites have been visited, more specific recommendations will be made