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.