INPUT PLUTONIUM ACCOUNTABILITY ANALYSIS IN A REPROCESSING PLANT BY SPECTROPHOTOMETRY USING INTERNAL STANDARD

Plutonium in a spent fuel dissolver solution of a reprocessing plant has usually been determined by isotopic dilution mass spectrometry (IDMS) because of its high precision. IDMS, however, is too time-consuming to know the amount of input nuclear material in the plant. IDMS is also regarded as a costly method for the purpose. An analytical technique based on spectrophotometry has been, therefore, developed for an alternative way. Standard neodymium solution was added to the same aliquot of input dissolver sample, followed by the oxidation of Pu(III), Pu(IV) to Pu(VI) with Ce(IV). Pu concentration was determined by repeatedly measuring absorbance ratio of Pu(VI) and Nd(III). Plutonium in spent fuel dissolver solutions determined by this method agreed well with that by conventional isotope dilution mass spectrometry. The precision of the plutonium determination was 0.4Z. Time required for the analysis was within two hours. The absorbance was not influenced by the acidity in the range of 0.5M to 1.5M HN03. The input plutonium accountability measurement could be replaced by this technique.