Monitoring of heat and moisture migration from radioactive waste disposed in an augered shaft

Soil temperature and moisture data have been collected for the past 4 years at the Greater Confinement Disposal Test (GCDT) being conducted at the Nevada Test Site. High-specific-activity radioactive waste with a thermal output of 3.4 kW was buried at a depth of 30 m in tuffaceous alluvium. Prior to waste emplacement the ambient subsurface temperature was about 170C and the volumetric soil moisture content was 10-12%. Two years after waste emplacement the soil temperature exceeded 1000C and the soil moisture content dropped below 4% at a radius of approximately 3 m from the thermal waste. Drying of the soil has occurred as the high temperature radiating from the thermal sources propels water vapor from the waste zone to a zone where dew-point temperatures are reached. The temperature and moisture data will be used in combination with data from gaseous tracer release tests in predicting and appraising the long-term performance of the GCDT