Beta Assayer The detector unit is a thin, massless (i.e., no attenuation correction required) gas (90 percent argon, 10 percent methane), proportional counter with multiple aluminum absorbers. On wastes aged ten years or more, laboratory tests show that both strontium-90 and cesium~137 can be assayed in the nanocurie per gram sensitivity range. The counting statistics reliability is a +10 percent. The unit was completed and tested in the field. It is mounted on a pushcart with large balloon wheels for transport across the desert terrain. The electronics and sensing element are all on the cart, with the power system being supplied by a vehicle with a 110-volt generator. DEV-VAN-I This is a van housing an argon dosimeter for measurement of 50 to 1,300 milliroentgens per year, an alpha water meter for assaying below maximum permissible concentration (MPC) levels, several NaI(Tl) portable instru- ments, a neutron counter with directional probe and the key detector systems, a Ge(Li) collimated unit (see Figure 1), and an L-X-ray system for determining plutonium and americium at nanocurie to picocurie levels. The unit is completed and is being field tested. DEV-VAN-ITI This development van is for in-van core collimated assaying and downhole radionuclide assay. Precision draw works for depth accuracies Zn the centimeter range are required. A directional system allows 360 coverage using windowed Ge(Li), intrinsic germanium, neutron, and Nal(Tl) detectors. Both plume characterization and movement with time DEV-VAN-II at the picocurie to microcurie levels. picture of the van with a boom on the end to allow distance between van and wells to minimize cave-in at burial grounds or cribs. will be determined by Figure 2 shows a attaching tools and problems, especially DEV-VAN-TIIT This van is in the planning stage and involves a californium-252 activa- tion source for determining downhole plutonium and uranium, and various matrix parameters such as density, porosity, void volume, and elemental compositions. 699