European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, DE-76125 Karlsruhe, Germany.
Anal Chem. 2010 May 15;82(10):4055-62. doi: 10.1021/ac9029295.
In order to prevent nuclear proliferation, the isotopic analysis of uranium and plutonium microparticles has strengthened the means in international safeguards for detecting undeclared nuclear activities. In order to ensure accuracy and precision in the analytical methodologies used, the instrumental techniques need to be calibrated. The objective of this study was to produce and characterize particles consisting of U, Pu, and mixed U-Pu, suitable for such reliability verifications. A TSI vibrating orifice aerosol generator in connection with a furnace system was used to produce micrometer sized, monodispersed particles from reference U and Pu materials in solution. The particle masses (in the range of 3-6 pg) and sizes (approximately 1.5 microm) were controlled by the experimental conditions and the parameters for the aerosol generator. Size distributions were obtained from scanning electron microscopy, and energy-dispersive X-ray analysis confirmed that the particle composition agreed with the starting material used. A secondary ion mass spectrometer (SIMS) was used to characterize the isotopic composition of the particles. Isobaric and polyatomic interference in the SIMS spectra was identified. In order to obtain accurate estimates of the interference, a batch of Pu particles were produced of mainly (242)Pu. These were used for SIMS analysis to characterize the relative ionization of Pu and U hydride ions and to determine the SIMS useful yields of U and Pu. It was found that U had a higher propensity to form the hydride than Pu. Useful yields were determined at a mass resolution of 450 for U-Pu particles: (1.71 +/- 0.15) % for Pu and (0.72 +/- 0.06) % for U. For Pu particles: (1.65 +/- 0.14) % for Pu. This gave a relative sensitivity factor between U and Pu (RSF(U:Pu)) of 2.4 +/- 0.2. However, the RSF(U:Pu) showed large fluctuations during the sputtering time for each analyses of the mixed U-Pu particles, in the range of 1.9-3.4.
为了防止核扩散，对铀和钚微粒的同位素分析加强了国际保障措施中探测未申报核活动的手段。为了确保分析方法的准确性和精密度，需要对仪器技术进行校准。本研究的目的是生产和表征由 U、Pu 和混合 U-Pu 组成的颗粒，以进行这种可靠性验证。使用 TSI 振动孔气溶胶发生器与炉系统相结合，从溶液中的参考 U 和 Pu 材料中产生微米级、单分散的颗粒。颗粒质量（3-6 pg 范围内）和尺寸（约 1.5 微米）由实验条件和气溶胶发生器的参数控制。通过扫描电子显微镜获得粒径分布，能谱分析（EDS）确认颗粒组成与所用起始材料一致。使用二次离子质谱仪（SIMS）对颗粒的同位素组成进行了表征。鉴定了 SIMS 谱中的同量异位素和多原子干扰。为了准确估计干扰，生产了一批主要由 (242)Pu 组成的 Pu 颗粒。这些颗粒用于 SIMS 分析，以表征 Pu 和 U 氢化物离子的相对电离，并确定 U 和 Pu 的 SIMS 有效产率。结果发现，U 比 Pu 更容易形成氢化物。在质量分辨率为 450 时，测定 U-Pu 颗粒的有用产率为：Pu 为（1.71 +/- 0.15）%，U 为（0.72 +/- 0.06）%。对于 Pu 颗粒：Pu 为（1.65 +/- 0.14）%。这给出了 U 和 Pu 之间的相对灵敏度因子（RSF（U：Pu））为 2.4 +/- 0.2。然而，在混合 U-Pu 颗粒的每次分析中，RSF（U：Pu）在溅射时间内显示出很大的波动，范围在 1.9-3.4 之间。
