DEVELOPMENT OF PROTOTYPE ISOTOPE DILUTION GAMMA-RAY SPECTROMETRY*

A novel technique, isotope dilution gamma-ray spectrometry (IDGS), has been recently developed for the simultaneous measurement of plutonium concentrations and isotopic composition in spentfuel dissolver solutions at a reprocessing plant. IDGS employs the high-resolution, low-energy, gamma-ray spectroscopy technique for the plutonium isotopic analysis and the isotope dilution principle for the plutonium concentration determination. The IDGS measurements have demonstrated nearly unbiased results relative to isotope dilution mass spectrometry (IDMS) measurements for both plutonium isotopic analysis and the plutonium concentration of dissolver solutions. The typical precision with a 1-hour count time is 0.2% for 239Pu, and less than 1% for plutonium concentrations. The rapid and accurate IDGS technique can provide a timely, lessexpensive, and simpler on-site verification method for the plutonium in input accountability samples. For automated, rapid measurements of the plutonium concentration and isotopic composition in spent-fuel dissolver solutions, we are developing a prototype IDGS system including physics, algorithms, and analysis software. The prototype IDGS system consists of a hyperpure germanium planar detector and associated electronics, an ORTEC multichannel buffer, and an IBM-compatible personal computer. The IDGS software package is a Windows application program and is being written in C.