RESONANCE IONIZATION MASS-SPECTROSCOPY FOR TRACE DETERMINATION OF PLUTONIUM IN ENVIRONMENTAL-SAMPLES

Resonance ionization mass spectroscopy (RIMS) is a sensitive and isoto pe selective method and well suited for trace analysis of plutonium in the environment. After the chemical isolation of plutonium from soil, air filters or urine, e.g., it is electrolytically deposited as hydro xide on a tantalum backing and covered with a thin titanium layer. By heating such a sandwich filament in the RIMS-apparatus under vacuum an atomic beam of plutonium is produced. The atoms are ionized by a thre e-step resonant excitation using pulsed dye lasers, and the ions are m ass-selectively detected with a time-of-flight (TOF) spectrometer and a multi channel plate detector. RIMS yields a low detection limit of 1 0(6)-10(7) atoms and a high element and isotope selectivity. This tech nique has been used for the investigation of soil samples from the Che rnobyl area, sediments from the Mururoa Atoll and urine samples with r espect to the total amount of plutonium and its isotopic composition.