Improved combined HRGS-TIMS method for rapid determination of Pu in nuclear material samples collected in the Rokkasho reprocessing plant

A combined method of high-resolution gamma spectroscopy and thermal ionization mass spectroscopy without chemical separation was applied for plutonium assay in pure Pu and U–Pu mixed solutions collected at the Rokkasho Reprocessing Plant, Japan. The relative biases of Pu assay results determined by the combined method to the conventional IDMS are less than 0.01% in the pure Pu and the U–Pu mixed solutions. The combined method can be used as an alternative rapid method for Pu assay as a backup to the conventional IDMS method and K-edge densitometry without any loss of precision and accuracy.