Rapid assay of plutonium in soils by passive L x-ray counting

Abstract

A technique has been developed to rapidly measure the presenw of plutonium in soils, lilters, smears, and glass waste forms by measuring the uranium L-shell x-ray emissions associated with the decay of plutonium. In addition, the technique can simultaneously acquire spectra of samples and automatically analyze them for the amount of americium, and gamma-ray emitting activation and fission products present. The samples are counted with a large area, thin-window, n type Ge sp~ctrometer which is equally efficient for the detection of low ener~x-raw (> 10 kev)> as WCIIas high-energy gamma rays (> 1 MeV). A 8192-channel analyzer is used to acquire the entire photon spectrum at one time. A dual-cner~, time-tagged pulser, that is injected into the test input of the preamplifier to monitor the energy scale, detector resolution, and pulse pile-up will be installed in FY-92. The L x-ray portion of each spectrum is analyzed by a linear Ieast-squares spectral fitting tcchniquc originally developed for the analysis of spectra from NaI('fl) detectors. The gamma-my portion of each spectrum is analyzed by a standard Ge gamma-ray analysis package. Detection Iimils (also referred to as lower limits of de(cction) for plutonium in contaminated soils that have been achieved by this technique are reported..,.