Plutonium process control using an on-line gamma monitor for uranium, plutonium and americium

An On-Line Gamma Monitor profiles the concentration of uranium, plutonium and americium in waste and product streams of the anion exchange process used to purify plutonium at Los Alamos. The Monitor employs passive gamma spectrometry to measure the 59.5 keV and 129 keV gamma rays of 241Am and 239Pu, respectively. Because the uranium impurity in typical process streams has no gamma ray suitable for passive measurement, a novel radiotracer technique is used. Uranium-237, always present in plutonium processed at Los Alamos as a minor alpha-decay daughter of 241Pu, has a 6.8-day half-life and 208 keV gamma energy, which make it an ideal radiotracer for macro amounts of uranium in the process. The On-Line Gamma Monitor is used routinely to provide Los Alamos operators with continuous, real-time process control information. (author) 5 refs.; 9 figs