The Radioactivity and Dose Assessment of Radioacarbon and Tritium in Graphite Waste Samples of the KRR-2

Abstract

The radioactivity of 14 C and 3 H 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 degrees centigrade, 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 1 g. The recoveries from the combustion furnace were around 100 % and 90 % in 14 C and 3 H, respectively. The minimum detectable activity was 0.04-0.05 Bq/g for the 14 C and 0.13-0.15 Bq/g for the 3 H at the same background counting time. 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.