小型自然循环钠冷堆堆芯初步设计研究

提出了一种适用于分布式发电系统的小型自然循环钠冷堆AMTEC系统。通过对堆芯的临界计算和热工水力分析，研究了堆芯燃料装载量不变情况下，芯块半径、燃料棒长度和圈数对堆芯有效增殖因数k_eff、堆芯压降和传热的影响。同时分析了不同额外停堆裕量下，B₄C吸收层厚度和堆芯初始剩余反应性随燃料棒圈数的变化关系。计算结果表明：保持堆芯当量直径和冷却剂通道总截面积不变的情况下，减少燃料棒圈数和活性区长度不仅可增加k_eff，且能降低堆芯压降；为提高额外停堆裕量需增加吸收层厚度，但降低了堆芯初始剩余反应性，不利于电厂的经济性。

Preliminary Design Research on Core of Small Natural-circulation Sodium-cooled Reactor

A small natural-circulation sodium-cooled reactor-AMTEC system was presented as a distributed generation system. According to the criticality calculation and thermal-hydraulic analysis of the core when the total fuel mass was constant, the influence of pellet radius, fuel pin length and the number of rings of fuel pins upon the effective multiplication factor k_eff, pressure drop across the core and heat transfer was analyzed. Additionally, the B₄C absorber thickness and beginning-of-life excess reactivity under different numbers of rings of the fuel pins were studied when the assumed additional shutdown margin was different. The results show that decreasing the number of rings and active fuel length would increase k_eff and decrease pressure drop across the core when the core equivalent diameter and total cross-sectional area of the coolant channel are unchanged. In order to increase additional shutdown margin, the absorber thickness should be increased while the beginning-of-life excess reactivity and power plant economy would decrease.