Development of a Precision Spectrophotometric Method with Internal Referencing for Determination of Metals in Nuclear Materials: II. Analysis of Plutonium in the Presence of Uranium

Two versions of a spectrophotometric method with internal referencing were developed for determination of the Pu content at U : Pu ratios of 40 : 1, 20 : 1, and 1 : 1. Precision determination of Pu(VI) with a relative root-mean-square deviation (RRMSD) <= 0.2% from intrinsic absorption is possible without separation of U with the use of calibration solutions containing U. Under the same conditions, microgram amounts of Pu(IV) in the presence of U (U : Pu = 20 : 1) can be determined with an organic reagent, carboxyarsenazo, with RRMSD of 0.3-0.5%. Both versions were successfully applied to analysis of large size dried (LSD) spikes containing 40 mg of U and 2 mg of Pu. All the measurements were carried out on a two-channel spectrophotometric analyzer.