Determination of plutonium in highly radioactive liquid waste by spectrophotometry using neodymium as an internal standard for safeguards analysis

Taguchi, Shigeo ; Surugaya, Naoki ; Sato, Soichi ; Kurosawa, Akira; Watahiki, Masaru; Hiyama, Toshiaki

A spectrophotometric determination using neodymium as an internal standard has been developed for safeguards verification analysis of plutonium in highly radioactive liquid waste which is produced by the reprocessing of spent nuclear fuel. The method offers reduced sample preparation and analysis time compared to isotope dilution mass spectrometry. It uses neodymium as an internal standard, which allows for determining an index for the authentication of the analytical operation and the instrument conditions. The sample was mixed with a known amount of neodymium as an internal standard. Subsequently, plutonium was quantitatively oxidized to Pu(IV) by the addition of Ce(IV). Plutonium concentration was calculated from a relation between Nd(III)/Pu(VI) molar extinction coefficient ratio and their absorbance ratio. The expanded uncertainty of the repeated analysis of plutonium (n=5) was found to be 15mgL (confidence interval 95%) for a highly radioactive liquid waste sample (173mgL). The determination limit was calculated to be 6mgL (ten fold's the standard deviation). This method was validated through comparison experiments with isotope dilution mass spectrometry. The analytical results of plutonium in highly radioactive liquid waste using this method were agree well with values obtained using isotope dilution mass spectrometry. The proposed method was successfully applied for the independent on-site safeguards analysis at the Tokai Reprocessing Plant.nt on-site safeguards analysis at the Tokai Reprocessing Plant.