Generalization of the IDGS Technique

Isotope Dilution Gamma-ray Spectrometry (IDGS) is a method using gamma-ray spectrometry technique to measure plutonium in solutions. To measure the plutonium concentration, the unknown solutions are spiked with plutonium of accurately known plutonium mass and isotopic composition. The isotopic compositions of the unknown solution and the spiked solution are determined by highresolution gamma-ray measurements. In the traditional IDGS method, the concentration of plutonium in the unknown solution is determined by calculating the differences among the 239Pu weight percent and isotopic 240Pu/239Pu ratios of the spike, the spiked solution, and the unknown solution. To improve the measurement result, we are developing a generalization method for the IDGS technique. The generalized IDGS method utilizes all the plutonium isotopes (except 242Pu) and americium fractions. This would allow the calculations of the concentration of plutonium in the unknown solution using other plutonium isotopic ratios in addition to the isotopic 240Pu/239Pu ratio.