Fukui Masami
Radiation Safety and Control Division, Department of Fundamental Nuclear Engineering, Research Reactor Institute, Kyoto University, Kumatori-cho, Sen-nan-gun Osaka, Japan.
Health Phys. 2005 Oct;89(4):303-14. doi: 10.1097/01.hp.0000161281.51407.a4.
Despite renovation of the D2O facility, tritium concentrations in the condensates of reactor room air showed tens of Bq mL before venting resumption on July 1997. This suggested the presence of tritium sources in the research reactor-containment building. An investigation was therefore initiated to locate the source and determine the distribution of tritium in the containment building. Air monitoring in the working area using a dish of water placed in the building suggested that the source of tritium was near the reactor core. Monitoring exhaust air from the two facilities (a cold neutron source and a D(2)O tank) showed high specific activity on the order of 10 Bq mL(-1), suggesting the presence of tritium in condensates near the reactor core. The major concern was whether the leakage of liquid deuterium (4 L) and heavy water (2 x 10(3) L) used as a moderator had occurred. The concentration of tritium in condensates has not increased over the past few years in either the exhaust line or working area, and the deuterium itself has not been found in the surrounding environment. The concentration of tritium measured using an ionization chamber after Ar decay was dependent on the thermal output of the research reactor, indicating that the tritium was produced by the irradiation process within shielding/moderator materials or cover gas with neutrons.
尽管对重水设施进行了翻新，但在1997年7月恢复排气之前，反应堆房空气中冷凝物中的氚浓度显示为每毫升数十贝克勒尔。这表明研究反应堆安全壳建筑中存在氚源。因此，展开了一项调查，以确定氚源的位置并测定安全壳建筑内氚的分布情况。在建筑内放置一盘水对工作区域进行空气监测，结果表明氚源靠近反应堆堆芯。对两个设施（一个冷中子源和一个重水箱）的废气监测显示，其比活度高达10贝克勒尔每毫升左右，这表明在反应堆堆芯附近的冷凝物中存在氚。主要担忧的是用作慢化剂的液态氘（4升）和重水（2×10³升）是否发生了泄漏。在过去几年中，排气管线或工作区域冷凝物中的氚浓度均未增加，且在周围环境中未发现氘本身。使用氩衰变后的电离室测量的氚浓度取决于研究反应堆的热输出，这表明氚是由屏蔽/慢化材料或覆盖气体中的中子辐照过程产生的。
