Elemental and isotopic analysis of americium in non-separated spent fuel using high resolution ICP-OES and sector field ICP-MS

摘要

As there are no certified reference materials, accurate, straightforward analytical procedures for the determination of americium (Am) in non-separated spent fuels employing high resolution ICP-OES and sector field (SF-)ICP-MS were developed and cross-validated. One spent (Th,Pu)O2 fuel and two U/Pu-based spent fuels representing different chemical and isotopic compositions were analysed for their Am content. Even though the lowest limit of detection (0.07 µg kg-1) was obtained at 283.226 nm, the ICP-OES signal at 408.929 nm provided the most reliable performance for the analysis of spent fuel among the six investigated Am emission wavelengths. A massive spectral interference from Th omitted the use of the 283.226 nm emission line for Am analysis of the (Th,Pu)O2 fuel, while other potential interferences from plutonium (Pu) and neptunium (Np) could be excluded for all tested Am wavelengths. Employing ICP-OES, both external calibration and standard addition yielded comparable Am concentrations. Calibration of the SF-ICP-MS response for Am was accomplished using both 232Th and 238U signals as well as applying the related mass bias. This calibration methodology that is frequently used in absence of an Am stock standard solution, was tested against a home-made 241Am stock standard solution underpinning the validity of this calibration approach. Sector field ICP-MS analysis essentially confirmed the Am concentrations obtained using ICP-OES in the three spent fuel solutions with mean values overlapping within their standard deviations. Considering isotopes of other actinides such as Pu and curium (Cm), the Am isotopic abundance (241Am, 242Am, 243Am) was established in two non-separated fuel solutions comparing well with model calculations based on the ORIGEN-2 code.