Extraction and Specific Activity Measurement of Tritium Induced in Accelerator Shielding

An infrared furnace (ULVAC RHL-410P) was newly applied to the extraction of tritium from concrete samples. After studying the tritium recovery yield regarding temperature and time, the best extraction conditions were set to 800 ℃ for 30 min under Ar-gas flow of 200 mL/min. Tritium was collected in two cold traps and transferred to a vial for liquid scintillation counting. It only took 55 min for the extraction of tritium. Reproducibility and recovery yield of tritium were about 100% compared to the values obtained by the ordinary heating method using an electric furnace. γ-ray emitters and tritium of concrete samples collected from several accelerator facilities were determined. The activity of tritium strongly correlated with that of ¹⁵²Eu and ⁶⁰Co, so it was found that tritium was produced by thermal neutron reaction of the 、⁶Li(n, α)³H. The results indicate that the tritium activity in concrete can be estimated from the ⁶⁰Co activity obtained easily by γ-ray measurement.