原型微堆进行低浓化是为将目前高浓铀(~(235)U富集度为90%)燃料组件更换为低浓铀燃料组件(~(235)U富集度小于20%),在高浓铀燃料组件卸出时,需先将中心控制棒移出堆芯。为确保卸料安全,在堆芯内外辐照座内(图1)设计了镉吸收体,用于卸料时临时停堆。在5个内跑兔管(图1中内1~5)和2个外跑兔管内分别放入镉串,镉串由3个镉盒组成,镉盒外直径为1.3cm、厚度为 The low enrichment of prototype microducts is to replace the current HEU (~ (235) U enrichment of 90%) fuel assemblies with LEU fuel assemblies (~ (235) U with less than 20% enrichment) When the HEU fuel assembly is unloaded, remove the center control rod first from the core. In order to ensure the safety of discharge, a cadmium absorber is designed inside and outside the reactor core (Figure 1) to temporarily shut down when unloading. The cadmium strings were placed in 5 running rabbit tubes (1 ~ 5 in Fig. 1) and 2 running rabbits respectively. The cadmium strings consisted of 3 cadmium boxes whose outer diameter was 1.3 cm and thickness