Environmental behaviour of tritium and assessment of public absorption dose tritium

（1）用彗星试验研究了氚水（HTO）对20 ~ 23周龄ICR雄性小鼠淋巴细胞DNA的低剂量效应（体外照射）。淋巴细胞经17- 50 mGy的HTO照射后，洗涤包埋的琼脂糖凝胶片，进行细胞裂解处理后电泳。使用成像软件分析电泳后染色载玻片上的单个彗星。未观察到明显的DNA损伤。（2）在释放到环境中的氚的化学形态中，氚化水对剂量的贡献较大。在温室内进行了重水（D2 O）蒸气释放试验，以D2 O代替HTO，研究了大豆不同生长过程中叶片对D2 O的吸收和损失动力学以及有机结合氘（OBD）在大豆体内的形成、运转和存留。测定了叶片白天和夜间吸收D_2的速率常数、释放后叶片D_2O损失的速率常数和半衰期。D_2O释放后，大豆中OBD浓度逐渐升高，直至暴露后3-4 d，随着暴露时间的延长，由于大豆的代谢消耗，OBD浓度逐渐降低。(3)An核聚变反应堆氚辐射的照射条件可能是低剂量率的长期照射。低剂量率辐射的生物效应尚不清楚，因为尚未建立任何适当的检测系统。为了研究氚的低剂量率效应，建立了一种用携带人类X染色体的仓鼠细胞进行超灵敏突变检测的系统。在0.18和44 cGy/h之间的剂量率氚水的诱变进行了测试。在较低剂量率下，突变频率似乎略有增加。

(1)The low dose effects of tritiated water (HTO) on mouse lymphocyte DNA (in vitro irradiation) were determined by the comet assay using ICR male mouse of 20 to 23 weeks old. After lymphocytes were exposed to 17-50mGy of HTO, the lymphocytes embedded agarose gel slides were washed and cell lysis treatment was conducted before electrophoresis. The individual comets on stained slides after electrophoresis were analyzed using imaging software. No significant DNA damages were observed.(2)Among the chemical forms of tritium released in the environment, tritiated water has a large contribution to the dose. Heavy water (D_2O) vapor release experiments were carried out in a greenhouse using D_2O as a substitute for HTO and uptake and loss kinetics of D_2O in leaves and formation, translocation and retention of organically bound deuterium (OBD) in bean of soy bean were investigated using different growth process of soybean. Rate constants of D_2 uptake in leaves in the daytime and nighttime release, rate constants and the half time of D_2O loss in leaves after release were determined. After D_2O release, OBD concentration in bean increased gradually until 3-4 days after the exposure and then decreased with time due to metabolic consumption in bean.(3)An exposure condition of tritium radiation from nuclear fusion reactor could be a long-term exposure with low dose rate. The biological effects of low dose rate radiation are not clear because any suitable detection system has not been established. To examine the low dose rate effect of tritium, a hypersensitive mutation detection system using hamster cells carrying a human X-chromosome was established. The mutation induction by tritiated water at dose rate between 0.18 and 44 cGy/h was tested. The mutation frequency seemed to be slightly increased at lower dose rate.