Isotope Ratios Measurements in Environmental Samples Using Thermal Ionization Mass Spectrometry (TIMS) and Filament Carburization

Thermal Ionization Mass Spectrometry (TIMS) is a widely used mass spectrometric technique for the determination of the isotopic composition of plutonium. Moreover, advances in the last decades have led to increasingly high precision and accuracy of the isotope ratio measurements using multiple ion counting detection system. High precision plutonium isotope measurements would allow distinguishing different types of plutonium contamination and could be used as a finger print to track various sources of plutonium in the environment. To measure plutonium isotope ratios with high precision and accuracy, stable ion beams with high intensity are desired. This is sometimes difficult to achieve, especially when measuring plutonium in low amounts. In this study, carburization of the Re filaments was used to increase the ionization efficiency of plutonium. Carburized filaments were prepared in a special vacuum chamber in which benzene vapour was introduced as a pure source of a carbon. As a result of the carburization of the filaments higher efficiencies were obtained. This carburization technique was combined with a multi-dynamic measurement technique using the multiple ion counting system and applied to two sediment samples IAEA 135 and IAEA 368; respectively. The results in term of plutonium isotope ratios are presented and compared with the literature values.JRC.D.2-Reference material