Germanium detector system for the detection of transuranics at low-activity concentrations in soil

A photon spectroscopy system is described which is designed for the detection of plutonium and 241Am in soil samples with a minimum turnaround time. Quantification is based upon the 60-keV gamma emitted in 241Am decay and upon the uranium L x-rays (energies from 13 to 22 keV) emitted by plutonium isotopes during alpha decay. The detector is a single-crystal, intrinsic-germanium-planar detector with a surface area of 21 cm2. Sensitivity is increased by incorporating a detector window with a larger than normal surface area. This optimized window size was established by Monte Carlo calculations. For small, Petri-dish samples, detection limits at the 3 sigma level for a 4-hr counting time are better than 4 pCi/g for plutonium and better than 0.05 pCi/g for 241Am. The specifications, performance, and cost of the system are discussed