COMPARISON OF NEUTRON MOISTURE GAUGES AND A NEUTRON TOOL FOR USE IN MONITORING WELLS

Research at the Idaho National Engineering Laboratory investigated the movement of water through a thick fractured basalt vadose zone. Measu rements taken in 20-cm diameter boreholes completed with 10.2-cm diame ter PVC casing and in specially constructed test containers filled wit h basalt showed that 50-m Ci neutron moisture gauges could distinguish differences in moisture levels in the basalt formation beyond the wel l's annular space. Measurements made at depths up to 55 m in similarly constructed monitoring wells in the field showed that moisture gauge readings lead to the same interpretation of moisture movement as readi ngs made with a 3-Ci neutron tool.