Analysis of plutonium isotope ratios including Pu/Pu in individual U-Pu mixed oxide particles by means of a combination of alpha spectrometry and ICP-MS.

Isotope ratio analysis of individual uranium-plutonium (U-Pu) mixed oxide particles contained within environmental samples taken from nuclear facilities is proving to be increasingly important in the field of nuclear safeguards. However, isobaric interferences, such as U with Pu and Am with Pu, make it difficult to determine plutonium isotope ratios in mass spectrometric measurements. In the present study, the isotope ratios of Pu/Pu, Pu/Pu, Pu/Pu, and Pu/Pu were measured for individual Pu and U-Pu mixed oxide particles by a combination of alpha spectrometry and inductively coupled plasma mass spectrometry (ICP-MS). As a consequence, we were able to determine the Pu/Pu, Pu/Pu, and Pu/Pu isotope ratios with ICP-MS after particle dissolution and chemical separation of plutonium with UTEVA resins. Furthermore, Pu/Pu isotope ratios were able to be calculated by using both the Pu/(Pu+Pu) activity ratios that had been measured through alpha spectrometry and the Pu/Pu isotope ratios determined through ICP-MS. Therefore, the combined use of alpha spectrometry and ICP-MS is useful in determining plutonium isotope ratios, including Pu/Pu, in individual U-Pu mixed oxide particles.