大亚湾核电站周围海域水生生物人工放射性核素辐射剂量率的蒙特卡罗计算

Monte Carlo calculation of artificial radionuclide radiation doses for aquatic organisms in the sea area around Daya Bay Nuclear Power Plant

为了定量研究核电站液态流出物对水生生物的辐射,建立了核电站周围海域水生生物辐射剂量模型,用MCNP程序对大亚湾11种辐射参考生物的人工核素辐射剂量率进行了计算.生物体建模时采用2个椭球体模型,分别模拟全身和器官团.选取了对生物影响最大的9种人工核素作为源项逐一模拟.最后以137Cs、90Sr、110mAg三种核素为例,根据其海水中的比活度计算出生物的吸收剂量率.结果表明在正常工况下大亚湾水生生物受到的辐射剂量是安全的,而且生物浓缩核素的内照射贡献了98%以上的辐射剂量.即使是在非正常工况下,海水中放射性核素含量升高,但只要比活度尚未超过海水水质标准的比活度限值,水生生物受到的剂量(最大剂量约3.420 mGy/a)仍然是安全的.本研究结果可用于评价核电站对海域生态环境的影响,以及水生物种的辐射防护工作.

To quantitatively investigate the radiation doses for aquatic organisms exposed to radioactive liquid efflu- ents from nuclear power plants, a radiation dose model of aquatic organisms in the sea area around Daya Bay Nucle- ar Power Plant, China, was established. The Monte Carlo Neutron and Photon Transport Code was used to calculate the radiation doses of artificial radionuclides for 1 1 radiation reference species in Daya Bay. Two ellipsoid models were used to represent the whole body and organs. Nine radionuclides with the largest influence on aquatic organ- isms were chosen as radiation sources and calculated. Using J37Cs, 9~Sr, and ll~＂~Ag as an example, dose rates ab- sorbed by organisms were calculated according to the activity of radionuclides in seawater. The study showed that aquatic organisms in Daya Bay were safe within normal operating conditions. Among the organisms investigated,Pampus chinensis received the maximum dose of 1.85 ~Gy/a, and that internal exposure of concentrated nuclides inside an organism contributed to more than 98% of radiation doses. In abnormal operating conditions, although a greater quantity of radionuclides were present in seawater, the doses that aquatic organisms received （ a maximum dose of approximately 3. 420 mGy/a） were still safe provided the activity concentration of radionuclides was within the limits of seawater quality standards. These calculated values can be used for evaluating the impact of nuclear power plants on marine environments, and for the protection of aquatic organisms from excessive radiation doses.