High frequency EMI sensing for estimating depleted uranium radiation levels in soil

This paper studies high (100 kHz up to 15 MHz) frequency electromagnetic responses (HFEMI) for DU metallic pieces and DU contaminated soils and derives a simple empirical expression from the measured HFEMI data for estimating DU contamination levels in soil. Depleted uranium (DU) is the byproduct of uranium enrichment and contains 33% less radioactive isotopes than natural uranium. There are at least thirty facilities at fourteen separate locations in the US, where munitions containing DU have been evaluated or used for training. At these sites, which vary in size, evaluation studies have been conducted with and without catch boxes. In addition, the DoD used DU at open firing ranges as large as thousands of acres (hundreds of hectares), for both artillery and aircraft training. These activities have left a legacy of DU contamination. Currently at military sites where DU munitions have been or are being used, cleanup activities mainly are done by excavating and shipping large volumes of site soil and berm materials to a hazardous material radiation disposal site. This approach is very time consuming, costly, and associated with the potential for exposure of personnel performing excavation and transportation. It also limits range use during the operation. So, there is an urgent need for technologies for rapid surveying of large areas to detect, locate, and removal of DU contaminants at test sites. Additionally, the technologies are needed to detect material at a depth of at least 30 cm as well as discriminate between DU metals and oxides from natural uranium and from other conductive metals such as natural and man-made range clutter. One of the potential technologies for estimating DU radiation levels in soils is HFEMI sensing. In this paper, HFEMI signals are collected for DU metal pieces, sodium diunarate (Na2U2 O3) and tri-uranium octoxide (U3O8). The EMI signal’s sensitivity with respect to DU material composition and conditions are illustrated and analyzed. A new scheme for extracting near-surface soil’s EM parameters is formulated.