Absolute determination of 79Se/80Se with AMS

Selenium-79 measurement with accelerator mass spectrometry (AMS) is increasingly being used for the determinations of ⁷⁹Se relevant nuclear data. Furthermore, ⁷⁹Se was deemed to be an ideal tracer nuclide for long-period and non-intrusive biological studies on selenium. An ultra-sensitive AMS measurement method of ⁷⁹Se has been established at the CIAE-AMS system. For further applications of ⁷⁹Se-AMS, reference standards were requested. ⁷⁹Se can be derived from the ⁷⁸Se(n, γ)⁷⁹Se reaction but cannot be accurately quantified by theoretical calculation owing to the small and dubious cross section and other relevant parameters. In this paper, an AMS method has been developed for the absolute determination of the ⁷⁹Se/⁸⁰Se ratio in a ⁷⁹Se sample with relatively high ⁷⁹Se content. The relative standard uncertainty of ⁷⁹Se/⁸⁰Se ratio is 4.7% and a reference standard is thus acquired. The results are favourable for further applications of ⁷⁹Se-AMS.