Multiple Ion Counting of Fission Product Ruthenium

Off-site characterization of nuclear fuel chemical separation activities is an evolving area, with continued interest in techniques that permit distant sampling. However, far-field detection is typically limited to atmospheric approaches that suffer from short temporal sampling windows. Vegetation has been shown to capture and create records of airborne particles; however, many chemical signatures in vegetation resulting from the nuclear industry are largely unexplored. These unexplored chemical signatures are important because they could act as reliable, long-term archives of nuclear activities, providing information on the nature, extent and source of contamination. Downwind accumulation of stable fission products provides the opportunity to assess a record of past nuclear activities. Ruthenium (Ru) is an ideal candidate, as it is among the most abundant of fission products, has isotopic signatures from uranium (U) versus plutonium (Pu) fission that are distinct from natural Ru, and is released as a volatile, oxide phase. These features of Ru make it ideal for offsite characterization. Ruthenium was demonstrated to react with the reducing surfaces of vegetation after the Chernobyl accident, but to our knowledge no attempts have been made to measure isotopic ratios at low levels. We present results for Ru separated from vegetation samples analyzed via multiple ion counting for Ru isotopic ratios using a Nu Instruments thermal ionization mass spectrometer (TIMS), an instrument equipped with Zoom lens technology, 16 Faraday detectors, and five ion counters. We have been able to quantitatively determine the natural background isotopic ratios of Ru, as well as measure the variability in Ru ratios on samples containing ultra-trace levels of Ru. This presentation will cover methods developed for handling, separation, loading, and analysis of Ru from vegetation samples.