应用分段烟羽模式估算秦山核电厂(二期)设计基准事故概率后果

A PROBABILITY CONSEQUENCE ESTIMATION OF DESIGN BASIC ACCIDENT FOR QINSHAN NUCLEAR POWER STATION PLANT (2×600 MW) USING SEGMENT METHOD

采用天气取样技术和分段烟羽模式估算了秦山核电厂二期工程（２×６００ＭＷ）一旦发生设计基准事故，在半径８０ｋｍ评价区内可能造成的事故概率后果．天气取样采用分层取样技术，根据秦山二期厂址百米气象铁塔一年逐时气象观测数据获取．持续时间长达３０天的事故释放采用分段烟羽模式由５个不同持续时间、不同释放量的烟段模拟；应用有效扩散参数概念以描述大气稳定度变化对扩散参数的影响，扩散参数采用厂址实测值．计算了每次事故释放通过浸没外照射、吸入、地面干、湿沉积外照射等照射途径造成的剂量，也估算了集体剂量．最终估算了每次事故释放在评价区内可能造成的集体剂量及其余补累积频率分布ＣＣＦＤ曲线．结果表明，秦山二期工程中某一个堆一旦发生失水事故，其集体剂量等于或大于１８人·Ｓｖ（累积概率水平为９５％）或等于、大于２５人·Ｓｖ（累积概率水平为５０％）．

The probability consequence of accident within an assessment area with radius 80 km caused by a Design Basic Accident (DBA) for Qinshan Nuclear Power Station (NPP) second stage (2×600MW) was estimated by using a weather sampling technique and a segment diffusion model. Based on hourly meteorological observation data for 1 year on the Qinshan site, a weather sample sequences was obtained by using stratified sampling technique. Five segments with different duration and different release amounts were adopted to simulate the release of DBA which will last for 30 days. The concept of effective diffusion parameter was used to describe the effect of the stability changes on the diffusion parameter during plume transfer. A set of measured values for diffusion parameters were adopted. The following individual doses were included: external dose from radionuclides in the immersion cloud, internal dose due to inhalation of radionuclides, external dose from dry and wet deposited radionuclides on the ground. The population dose was also estimated. The complementary cumulative frequency distribution CCFD of population dose within assessment area caused by DBA release is finally estimated. The results showed that the population dose cause by DBA for the Qinshan NPP (2×600MW) is more than or equal to about 18 men Sv(95% cumulative probability level) or about 25 men Sv(50% cumulative probability level) respectively.