拟建桃花江AP1000核电站LOCA ^(131)I源项分析

LOCA I-131 source term analysis for the proposed Taohuajiang AP1000 NPP

针对核电厂事故工况下放射性物质的大气弥散问题,运用CALPUFF空气质量模型,模拟了桃花江核电厂冷却剂丧失事故(LOCA)工况下典型气载放射性物质131I的大气弥散过程,并对计算结果进行辐射剂量的估计,结果表明:1)事故开始后数小时内,源下风向8 km左右,高程与释放源有效高度相当,且海拔明显高于上风向海拔的地形区域,极易形成131I地面空气积分浓度峰值。2)三种化学形态的碘中,元素碘最易沉积。计算区域内地面沉积浓度与空气积分浓度呈现相同的分布规律。3)131I内照射造成的最大剂量当量比外照射高4个数量级,因而事故情况下防止放射性物质从呼吸道、口腔、伤口及皮肤进入人体,能极大降低131I的辐射剂量当量。

In this paper, atmospheric dispersion of 131I from a loss of coolant accident （LOCA） at the proposed Taohuajiang nuclear power plant （NPP） is simulated with the CALPUFF modeling system. The following results are obtained： （1） Within a few hours after the accident, at the grid point in the downwind direction, which is about 8 km away from the source, the 131I concentration forms a peak of air-time integration activity, because the altitude is as high as effective height of the source, while it is the highest in the downwind direction. （2） Among the three chemical forms of iodine, elemental iodine is the most likely to deposit, with the same contour distribution of deposited activity in the ground as the time-integrated air concentration. （3） The dose equivalent resulting from 1311 internal exposure caused is far greater than external exposure, hence the need of, should a LOCA occur, preventing radioactive materials from entering human body via the respiratory tract, oral cavity and skin wound, so as to greatly reduce the 131 I radiation dose equivalent.