Abstract

The neutron spectrum is an essential factor in making possible the increase of ²³³U isotope breeding from thorium fuel in an accelerator-driven subcritical (ADS) system; therefore, studying the effects of various moderators and coolants on ²³³U breeding is an important step in ADS performance. This study aims to evaluate the effect of using different moderators and coolants on the ADS system characteristics. Sodium, which was the most common coolant used in ADS reactors, was replaced by light water (LW) and graphite + CO₂, separately. In this study, we used uranium nitride as the seed fuel associated with ThO₂ as the blanket fuel for all cases. The Monte Carlo transport code MCNPX 2.7.0 was used to calculate neutronic parameters such as effective multiplication factor (K_eff), power peaking factor (P_max/P_av) in the radial direction of the ADS reactor core, actinide isotope evolution during fuel burnup, and power fraction from each fuel type for all cases. The results show that the utilization of graphite as the moderator with CO₂ as the coolant allows more ²³³U production in thorium fuel compared with sodium and LW. On the other hand, LW showed great ability for plutonium and minor actinide transmutation and for energy generation.

摘要

中子光谱是在加速器驱动的亚临界（ADS）系统中使由from燃料产生的²³³ U同位素的增加成为可能的重要因素。因此，研究各种缓和剂和冷却剂对²³³ U繁殖的影响是ADS性能的重要一步。这项研究旨在评估使用不同的调节剂和冷却剂对ADS系统特性的影响。钠是ADS反应器中最常用的冷却剂，分别被轻水（LW）和石墨+ CO ₂代替。在这项研究中，我们使用氮化铀作为与ThO ₂相关的种子燃料作为所有情况下的毯子燃料。使用蒙特卡罗运输代码MCNPX 2.7.0计算中子学参数，例如有效乘数因子（K _eff），ADS反应堆堆芯径向的功率峰值因子（P _max / P _av），燃料过程中act系元素同位素的演化在所有情况下，每种燃料类型的燃耗和功率分数。结果表明，石墨的利用率与CO主持人₂作为冷却剂允许更多的²³³ ü生产钍燃料与钠和LW比较。另一方面，LW表现出强大的act和次act系元素trans变能力以及产生能量的能力。