Neutronics calculation for AP1000 based on the fission response function
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摘要: 使用基于裂变响应函数算法的FLASH程序,在具有复杂堆芯结构的AP1000反应堆内进行计算验证。通过基于Serpent蒙特卡罗程序的参考工况计算构建裂变响应函数数据库,结合局部组件间环境效应修正因子算法,有效消除了组件状态差异对计算精度的影响。同时,采用预估-校正法对反射层进行了精确模拟。自主开发的FLASH程序在AP1000 堆芯热态零功率工况下进行了数值验证,结果表明:与蒙特卡罗参考解相比,各2D轴向切片的有效增值系数偏差均控制在+220 pcm以内,全堆三维有效增值系数偏差为+209 pcm;2D棒功率分布的均方根误差低于1.1%,三维棒功率均方根误差为1.05%,组件功率均方根误差为0.67%。在20核并行条件下,FLASH程序实现了AP1000全堆三维计算,耗时仅为73秒,验证了所提方法的高效性与高精度。Abstract:
Background High-fidelity neutronics simulation of nuclear reactor cores, particularly those with complex geometries such as the AP1000, remains computationally challenging. Efficient deterministic methods that can achieve Monte Carlo-level accuracy are highly desirable for design and analysis.Purpose This study aims to develop, apply, and validate the FLASH code, which implements an advanced Fission Response Function (FRF) algorithm, for performing efficient and accurate full-core, pin-wise neutronics calculations of the AP1000 reactor core.Methods The FRF database was generated through reference-state simulations using the Serpent Monte Carlo code. To enhance accuracy in complex geometries, the methodology incorporated a local inter-assembly environmental correction factor to address fuel assembly heterogeneity and a predictor-corrector scheme to precisely simulate reflector environmental effects. The performance of the FLASH code was validated against reference Monte Carlo solutions under Hot Zero Power (HZP) conditions.Results The validation results demonstrated high accuracy. Deviations in the effective multiplication factor (keff) were within +220 pcm for all 2D axial slices and +209 pcm for the full 3D core calculation. The root-mean-square error (RMSE) was below 1.1% for the 2D pin power distribution, while the 3D pin power RMSE was 1.05% and the 3D assembly power RMSE was 0.67%. In terms of efficiency, the FLASH code completed the pin-wise full-core 3D calculation for the AP1000 in 106 seconds using 64 CPU cores.Conclusions The developed FLASH code, based on the FRF algorithm with integrated correction schemes, successfully bridges the gap between efficiency and high fidelity. It provides a rapid and accurate computational tool for AP1000 core analysis, confirming the practicality and effectiveness of the proposed methodology for detailed reactor physics calculations. -
图 1 AP1000反应堆堆芯径向排布图[10]
Figure 1. AP1000 reactor core radial arrangement
表 1 堆芯组件7种区域布置细节表
Table 1. Core assembly arrangement details for seven regions
region group fraction of total U235 Midzone U235 Blanket IFBA Rods WABA Rods 1 0.10 0.740 Absent 0 0 2 0.31 1.580 Absent 0 0 3 0.18 3.200 1.580 0 0 4 0.23 3.776 3.200 68 8L+4S 5A 0.05 4.376 3.200 88 4I 5B 0.03 4.376 3.200 124 0 5C 0.10 4.376 3.200 124 8I 表 2 slice1-7两种功率相对误差情况汇总表
Table 2. Summary table of relative power errors for slice 1-7
slice FLASH keff reference keff pin-wise power RMSE/% case-wise power RMSE/% 1 1.06395 1.06263 0.72 0.42 2 1.01983 1.01761 0.92 0.42 3 1.01062 1.00863 0.98 0.54 4 1.00139 0.99950 1.03 0.51 5 1.01064 1.00858 1.00 0.58 6 1.01968 1.01751 1.05 0.65 7 1.06210 1.06195 0.78 0.53 表 3 FLASH计算AP1000-3D所需时间
Table 3. FLASH calculation time for AP1000-3D
task number of core duration/s read FRF database 1 21 2D calculations for 7 slices 20 22 collapse calculation for 7 slices 20 16 3D full-core collapse matrix calculation 20 3 power reconstruction + output distribution 1 11 total duration − 73 -
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