Shielding effect on tritium water monitoring system based on CaF₂ flow-cell detector postprint

Abstract: A monitoring system based on a CaF₂ flow-cell detector was previously developed for measuring the tritium concentration in water. The flow-cell detector was fabricated using a granular CaF₂(Eu) solid scintillator. In the present study, the effect of lead shielding on the measurement sensitivity was investigated. First, measurements were carried out both on tritium water and tritium-free water without the use of shielding. Counts were accumulated for either 600 or 10 000 s and the detection limits without shielding were calculated. Second, the effect of shielding was evaluated using background radiation. Lead blocks with a thickness of 5 cm were used as shielding materials. Full shielding around the entire measurement system reduced the background count by 53.8%. Approximating this to a background reduction of 2 times, the detection limit with full shielding was then calculated. It was concluded that 5-cm-thick lead shielding reduced the detection limit for tritium by at least 35%