The radioactivity estimation of 14C and 3H in graphite waste samples of the KRR-2

Abstract

The radioactivity of 14C and 3H in graphite samples from the dismantled Korea Research Reactor-2 (the KRR-2) site was analyzed by high-temperature oxidation and liquid scintillation counting, and the graphite waste was suggested to be disposed of as a low-level radioactive waste. The graphite samples were oxidized at a high temperature of 800°C, and their counting rates were measured by using a liquid scintillation counter (LSC). The combustion ratio of the graphite was about 99% on the sample with a maximum weight of 1g. The recoveries from the combustion furnace were around 100% and 90% in 14C and 3H, respectively. The minimum detectable activity was 0.04–0.05Bq/g for the 14C and 0.13–0.15Bq/g for the 3H at the same background counting time. The activity of 14C was higher than that of 3H over all samples with the activity ratios of the 14C to 3H, 14C/3H, being between 2.8 and 25. The dose calculation was carried out from its radioactivity analysis results. The dose estimation gave a higher annual dose than the domestic legal limit for a clearance. It was thought that the sampled graphite waste from the dismantled research reactor was not available for reuse or recycling and should be monitored as low-level radioactive waste.