RADIATION MEASUREMENTS OF EXCAVATED ITEMS AT A RADIOACTIVE-WASTE BURIAL SITE

Radiation measurements on items excavated from a radioactive-waste bur ial ground were part of a field test of excavation techniques for the cleanup of subsurface sites. The waste resulted from plutonium product ion for nuclear weapons at Hanford, WA. The radiation measurements inv estigated techniques for classifying bulk waste for placement into a p ermanent disposal facility. Hand-held gamma-ray survey instruments mea sured exposure rates (mR/h) from contaminated dirt and radioactive obj ects as they were removed by heavy excavation equipment. Gamma-ray det ectors mounted on the excavation equipment provided additional data th at were transmitted by radio. Exposure rates from identifiable objects (e.g. specific reactor components) were compared with expected exposu re rates calculated from site-disposal records and computer modeling. Selected objects were subjected to additional on-site measurements usi ng a high-purity germanium detector. Detected nuclides included Co-60, Cs-137, Eu-152,Eu-154, and Ag-108m. A large-volume neutron detector c hecked for possible transuranic nuclides. Alpha and beta spectrometry also were tested, but their utility for this application was limited d ue to the short range of the particles and the difficulty of maintaini ng a repeatable measurement geometry in the held.