EXPERIMENTAL INVESTIGATION OF 14C IN THE PRIMARY COOLANT OF THE 10 MW HIGH TEMPERATURE GAS-COOLED REACTOR

The very high temperature reactor (VHTR) is a development of the high-temperature gas-cooled reactors (HTGRs) and one of the six proposed Generation IV reactor concept candidates. The 10 MW high temperature gas-cooled reactor (HTR-10) is the first pebble-bed gas-cooled test reactor in China. A sampling system for the measurement of carbon-14 (C-14) was established in the helium purification system of the HTR-10 primary loop, which could sample C-14 from the coolant at three locations. The results showed that activity concentration of C-14 in the HTR-10 primary coolant was 1.2(1) x 10(2) Bq/m(3) (STP). The production mechanisms, distribution characteristics, reduction routes, and release types of C-14 in HTR-10 were analyzed and discussed. A theoretical model was built to calculate the amount of C-14 in the core of HTR-10 and its concentration in the primary coolant. The activation reaction of C-13 has been identified to be the dominant C-14 source in the core, whereas in the primary coolant, it is the activation of N-14. These results can supplement important information for the source term analysis of C-14 in HTR-10 and promote the study of C-14 in HTGRs.