中文摘要：

采用高斯分段烟羽模型估算了某小型动力堆在码头内发生破口尺寸为29.4％当量直径的设计基准事故时，放射性核素在码头20 km 区域范围内的大气扩散规律。源项采用严重事故计算程序M ELCOR仿真获得，并将计算结果输入到大气扩散分析软件M ACCS进行分析计算。计算结果表明：中破口失水事故会造成码头区域的放射性污染，风速越小、气象条件越稳定，放射性的影响范围越大。

英文摘要：

Using the model of Gaussion subsection plume ,the radioactive nuclide atmos‐pheric dispersion rule in the terrain of 20 km of the coastal w as estimated w hen the design basis accident with 29.4% equivalent diameter break size happened .The source term was captured by the calculation program of severe accident named MELCOR ,and the result was used as input in the analysis software of atmospheric dispersion named MACCS .The results show that the mid‐break LOCA would lead to the radioactive pol‐lution for the area of dock .The slower the wind blows and the more steady the weather is ,the larger the radioactive polluted area is.