Study of tritium in the primary loop of HTR-10: Experiment and theoretical calculations

An experimental system for the measurement of tritium in the primary loop of HTR-10 has been established, sampling gas from the helium purification system. After the restart of HTR-10 in 2015, the activity of tritium in the primary loop has been obtained at three different sampling points: upstream of the copper oxide bed, downstream of the copper oxide bed, and downstream of the molecular sieve adsorber. The experimental results indicated that the activity concentration of tritium in the primary loop of HTR-10 was 1.09 (10) × 104 Bq/m3STP. The calculated value of 2.31 × 105 Bq/m3STP was highly conservative compared to the experimental results. The discrepancy between experimental data and theoretical result may come from uncertainties in the inputs to the generation term (He-3 in the helium coolant and Li-6 in the graphite), and the ability of the graphite in the primary coolant circuit to absorb and desorb tritium. The experimental data for the activity of tritium in the primary loop of HTR-10, HTTR, and AVR are presented and compared. The chemical form of H-3 and other factors affecting the experimental measurements are discussed.