The 3D simulation system for the decommissioning of nuclear power plants is supposed to provide real-time display of the radiation field level of the decommissioning site, which requires its module for radiation field calculation to perform quickly and accurately. However, regions with complex geometry and regions with simple geometry coexist in the site, and a single method of radiation field calculation has its own advantages and disadvantages, which cannot meet the requirements of accuracy and calculation time simultaneously. Therefore, the coupling method of Monte Carlo and point kernel integration is proposed. Using the coupling method to calculate the radiation field of the single source model, the results show that the coupling method has reasonable accuracy and a greatly shortened calculation time compared with the single MC method. On this basis, the influence factors of the calculation accuracy and time of the coupling method are explored. Computational experiments show that the coupling method has better accuracy in the calculation of high source energy; when the mesh is fine, the calculation time of the coupling method becomes longer. In general, the coupling method is stable. Finally, the decommissioning radiation field of Qinshan I is calculated by the coupling method. The results indicate that the MC-PK coupling method has reasonable accuracy and fast calculation speed, which can cover the demands for the decommissioning radiation field calculation of nuclear power plants and provide a basis for the development of the calculation module in the simulation system.

介绍了基于点源空间效率函数的层析γ扫描(TGS)无源效率刻度方法.利用TGS系统MC-NP模型计算探测空间120 cm×60 cm×50 cm和γ能量0.01～1.408 MeV的点源空间效率,建立点源空间效率函数及参数,采用体素中心点源效率等效法,实现体素效率矩阵计算.结果表明:5种γ能量在探测空间507个位置处的效率测量值和函数计算值具有较高相关性,说明该方法能够准确、快捷地实现TGS体素无源效率刻度.

针对200 L核废物桶分段γ扫描(SGS)过程中的效率刻度问题,提出了一种效率刻度函数模型,采用MCNP程序计算不同基质密度和γ射线能量条件下的离散断层效率,经过多元非线性回归获取函数参数,从而建立效率刻度函数,实现核废物桶SGS断层效率刻度.对核废物桶样品进行实验分析,结果表明:对于桶内基质分别为密度0.310 g·cm?3的硅酸铝、密度0.595 g·cm?3的木质纤维,桶内核素分别为活度3.110×105 Bq的点源137Cs、活度1.371×105 Bq的点源60Co,在桶内仅有单个点源存在的核素分布极端不均匀情况下,桶内核素活度重建误差在?37.68％～31.52％范围内.本文的方法能够准确有效实现核废物桶SGS断层效率矩阵计算,并确定核废物桶内放射性核素活度,满足实际检测要求.