Am装载对加速器驱动次临界系统瞬态过程的影响分析

Impact of Americium Loading on Transient of Accelerator Driven Subcritical System

加速器驱动次临界系统(ADS)由于外中子源驱动的特点带来大安全裕量,其被广泛设计用于嬗变次锕系(MA)核素。堆芯装载MA核素会减弱燃料的负多普勒效应、增加冷却剂的正温度系数并减小有效缓发中子份额,从而影响系统对扰动的瞬态响应,其中Am同位素的影响尤为重要。本文基于装载金属燃料的ADS嬗变方案,分析了不同Am装载份额条件下系统对于束流过功率和无保护瞬态过功率事故的瞬态过程,发现在深次临界状态下Am装载量对ADS的瞬态过程影响较小,说明ADS具有良好的安全特性,适宜高MA份额燃料的装载。

As driven by external neutron source and working under subcritical state, the accelerator driven subcritical system （ADS） provides larger safety margin and is widely adopted for minor actinides （MA） transmutation. Loading MA into the subcritical core, especially the isotropic of americium, will decrease the magnitude of the negative Doppler feedback effect, increase the positive coolant temperature coefficient and also reduce the effective delayed neutron faction. Furthermore, it will impact the system response under transient processes. Based on an ADS transmutation design loaded with metallic fuel, the transient of beam overpower and unprotected transient of overpower accidents under different americium concentration conditions was investigated. It is found that the impacts of americium are not obvious. This demonstrates the enhanced safety characteristics and the potential flexibility to utilize fuel with high MA ratio.