Measurement of 160tb and 161tb in Nuclear Forensics Samples

160Tb and 161Tb are important radionuclides to measure when analysing a Nuclear Forensics sample. An analytical method for the measurement of both 160Tb and 161Tb was developed in this study. Terbium was separated and purified using exchange resin and TrisKem LN Resin. The purified fraction containing 160Tb and 161Tb was measured by gamma spectrometry and liquid scintillation counting. The counting efficiencies of 160Tb and 161Tb were determined using the CIEMAT/NIST efficiency tracing method. The LSC count rate ratio, \({{R_{{{}^{160}{\text{Tb}}}} } \mathord{\left/ {\vphantom {{R_{{{}^{160}{\text{Tb}}}} } {R_{{{}^{161}{\text{Tb}}}} }}} \right. \kern-0pt} {R_{{{}^{161}{\text{Tb}}}} }}\), on the reference date was determined by sequential counting and calculated using a custom script based on their half-lives.