Sensitivity analysis of rod rearrangement in criticality safety for PWR fuel assemblies under transportation accidents

Custom Python scripts were used to automatically generate input files for the calculations. Parameter Scanning: For the Uniform Arrangement by Blocks, the fuel rod pitch in the central region was adjusted. For the Layer-by-Layer Determination, the number of deformed layers and their spacing were varied. For the Old/New Birdcage Deformation, the curvature radius of the damaged nozzle deformation was adjusted to simulate non-uniform fuel rod arrangements. Statistical Settings: Each simulation generation included 10,000 initial neutrons, with a total of 1,000 generations run (800 of which were active).

A single calculation took approximately 40 minutes (using an Intel i7-13700KF CPU and NVIDIA RTX 3080 GPU). 3.Errors and Missing Data: Statistical Errors: Inherent fluctuations due to the Monte Carlo method caused variations in results. 4.Data Files and Tools: Input files were generated using Python scripts. The Monte Carlo calculation program was based on the ENDF/B-VI nuclear database.