Year
2005
Abstract
Quantitative Plutonium analysis depends upon the accurate identification of the assay peak. The Np[Pa] equilibrium pair introduces interfering peaks in 239Pu, 238Pu, and 235U assay peak regions. When an interfering peak is present, it negates the assay unless an appropriate technique can be developed to deal with the interference. Peak Stripping is one such technique. Peak stripping involves an algorithm to strip an entire peak from another, resulting in a spectrum that can then be analyzed for the radionuclide of interest. A simpler method is a “pseudo-peak-stripping” whereby the effects of the interfering peak are quantified and those effects are stripped from the assay data. In this case, integrated peak areas are analyzed and corrected. There are two methods presented in this paper. Both assimilate the integrated data for the assay peak regions (in this case 239Pu, 238Pu, and 235U) and for the Neptunium/Protactinium secular equilibrium pair ([Np[Pa]). Using Np[Pa] assumes that the Protactinium has come to equilibrium with Neptunium. This requires only ~ 6months from the time chemical purification. Therefore it is a valid assumption in most cases. A correction is then applied to the assay peak areas to “strip” the underlying effects of Np[Pa].