ABSTRACT

Fuel debris removal is the most challenging part of damaged nuclear power station decommissioning. It is important to carry out nuclear safety calculations accurately and quickly enough. Here, it was clarified that modern codes based on the Monte Carlo method were capable of performing neutronic analysis with the same accuracy and without significant differences in the results. The benchmark calculations were performed using three codes: MVP, Serpent, and MCU. In this study, the comparison focused on multiplication factor, neutron fluxes and reaction rates relative difference, and calculation time of many fuel debris particles system. Then the calculation results were used when codes comparing. It was shown that the calculation results showed good agreement between all codes. It was assumed that minor differences in the thermal range of neutron fluxes can be caused by different thermal neutrons scattering treatment for all codes. The study also showed that solving such problems requires significant computing power and time. It has been proven that the statistical geometry model in the MVP and the explicit stochastic geometry model in the Serpent have the possibility to provide solutions with the same accuracy, but much faster.

摘要

燃料碎片清除是受损核电站退役中最具挑战性的部分。足够准确和快速地进行核安全计算非常重要。在这里，澄清了基于蒙特卡罗方法的现代代码能够以相同的精度进行中子分析，并且结果没有显着差异。使用三个代码执行基准计算：MVP、Serpent 和 MCU。在本研究中，比较集中在许多燃料碎片粒子系统的倍增因子、中子通量和反应速率的相对差异以及计算时间上。然后将计算结果用于代码比较。结果表明，计算结果表明所有代码之间具有良好的一致性。假设中子通量的热范围的微小差异可能是由对所有代码的不同热中子散射处理引起的。该研究还表明，解决此类问题需要大量的计算能力和时间。已经证明，MVP 中的统计几何模型和 Serpent 中的显式随机几何模型有可能以相同的精度提供解决方案，但速度要快得多。