Contamination by tritium of waters and concrete in a research reactor containment due to leakage of heavy water

Approximately heavy water of ca. 28.2L (ca. 0.34 TBq of tritium) leaked from the D20 facility of the Kyoto University Reactor (KUR) during the period of about one and half year. As a result of the incident, HTO concentrations in pool waters had increased extensively as well as in the containment building air during the period before the leak detection. The soaking effect of HTO vapor by the building concrete was also confirmed by air monitoring. Although the leak was of little radiological consequence it served as a useful lesson of our emergency response. (author)