In this paper, the ex-core source-range detector response was simulated for AP1000 cores in its fuel-loading process by using a Monte Carlo code. Firstly, the current sensitivity coefficients of the ex-core source-range detectors have been calibrated by utilizing the experiments with single fuel assembly and the primary source loaded in the core. Secondly, both relative and absolute calibration methods have been applied and analyzed for the sensitivity coefficients calibration. Thirdly, the simulation values for the ex-core source-range response with fully loaded fuel have been validated by using the actual measurement of the first AP1000 cores in the world. Fourthly, the contribution of the ²³⁸U spontaneous fission to the ex-core source-range detector response has been studied. Through the numerical simulation results, the following observations can be obtained: 1) The relative calibration method is better than the absolute calibration method, especially when the ex-core source-range response is small. 2) Compared with the measurements, the relative deviation between the simulated and the measured values is within 14% for the two AP1000 cores at Sanmen Nuclear Power Plant. 3) The intensity of ²³⁸U spontaneous fission source accounts for 15% of the total source strength in the AP1000 core Unit 1, but the maximum change of response is only 0.02 cps, which is still insignificant for the ex-core detector response simulation in PWR.

在本文中，使用蒙特卡洛代码对AP1000内核在燃料装载过程中的核外源范围探测器响应进行了仿真。首先，通过利用单个燃料组件和装载在堆芯中的主要燃料源的实验，对堆外核源范围探测器的当前灵敏度系数进行了校准。其次，相对和绝对校准方法均已应用，并针对灵敏度系数校准进行了分析。第三，已经通过使用世界上第一批AP1000磁芯的实际测量结果验证了满载燃料时核外源范围响应的仿真值。第四，²³⁸的贡献研究了自发裂变对前核源范围探测器的响应。通过数值模拟结果，可以得到以下观察结果：1）相对校准方法优于绝对校准方法，尤其是在核外源范围响应较小的情况下。2）与实测值相比，三门核电站两个AP1000堆芯的仿真值与实测值之间的相对偏差在14％以内。3）²³⁸ U自发裂变源的强度约占AP1000核心单元1总源强度的15％，但响应的最大变化仅为0.02 cps，这对于图1中的核外探测器响应模拟仍然微不足道。压水堆