Measurement of30Si as a tracer by neutron-induced prompt gamma-ray analysis

The application of stable isotope analysis using neutron-induced prompt -ray analysis (PGA) with cold/thermal neutron beams for the tracer study of geological materials are discussed. Silicon has three natural isotopes differing in abundance:²⁸Si (92.23%),²⁹Si (4.67%) and³⁰Si (3.10%). For the purpose of the assessment of Si migration in engineered barrier material, enriched³⁰Si can be used as a tracer due to its nuclear and chemical properties. Isotope analysis of³⁰Si was performed by PGA during the tracer study. Neutron intensity at the sample position was 1.4·10⁸ n¢cm^–2·s^–1, 2.4·10⁷ n·cm^–2·s^–1 for cold and themal neutron guided beams of JRR-3M, respectively. Calibration curves and analytical sensitivity of³⁰Si were determined based on measurement of standard samples. BG and detection limits for³⁰Si analysis were also measured in Japanese bentonite (Kunigel V1 and Kunipia F) and their pore water. Fiffteen elements were determined simultaneously using PGA.