Simultaneous determination of plutonium and uranium isotope ratios in individual plutonium-uranium mixed particles by thermal ionization mass spectrometry

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• 作者：Chi-Gyu Lee ; ^{lee.chigyu@jaea.go.jp} ; Daisuke Suzuki ; Yoko Saito-Kokubu ; Fumitaka Esaka ; Masaaki Magara ; Takaumi Kimura
• 关键词：TIMS ; Individual U&ndash ; Pu mixed particles ; Isotope ratios ; Submicrometer-sized particles
• 刊名：International Journal of Mass Spectrometry
• 出版年：2012
• 期刊代码：43_13873806
• 类别：ch
• 出版时间：15 March, 2012
• 卷：314
• 期：Complete
• 页码：57-62
• 文件大小：681 K

摘要

Simultaneous determination of plutonium (Pu) and uranium (U) is preferred for analyzing the isotope ratio in Pu and U mixed samples such as the particles formed from MOX (mixed U-Pu oxide) fuels. In this study, we developed a method for the simultaneous measurement of all the plutonium and uranium isotopes without the need for chemical separation, using thermal ionization mass spectrometry (TIMS) with a continuous heating method. The MOX particles with sizes of 0.6-2.3 渭m used in this study were made from a mixed solution of plutonium (SRM947) and uranium (U500, 50%²³⁵U enriched). The isotope ratios of plutonium and uranium obtained for all the MOX particles, including the ones in the sub-micrometer size range, were in good agreement with the certified values within the range of error. In particular, the determination of the ²³⁸Pu/²³⁹Pu isotope ratio, which is difficult because of the isobaric interference of ²³⁸U, was performed accurately. The ²³⁸Pu/²³⁹Pu ratios were obtained by using a correction in which the background of ²³⁸U intensity at the ²³⁸Pu peak was estimated from the peak fitting of the ²³⁸U signal profile. In addition, the ²⁴¹Pu/²³⁹Pu isotope ratio could be accurately measured without being influenced by the ²⁴¹Am formed by the decay of ²⁴¹Pu. For the MOX particles with diameters of 1.12 渭m, the relative standard deviations (2RSDs) of the ²³⁸Pu/²³⁹Pu, ²⁴⁰Pu/²³⁹Pu, ²⁴¹Pu/²³⁹Pu, and ²⁴²Pu/²³⁹Pu isotope ratios were 15.2%, 3.4%, 12.5%, and 5.1%, respectively. The relative standard deviations (2RSDs) of the ²³⁴U/²³⁸U, ²³⁵U/²³⁸U, and ²³⁶U/²³⁸U isotope ratios were 7.0%, 3.0%, and 41.2%, respectively. It is expected that the method developed in this study will become a powerful tool for the analysis of Pu and U mixed samples because of its ability to measure simultaneously even the minor isotopes of plutonium and uranium without any chemical separation.