MCNP可给出瞬发中子移出时间,但该值并不等同于点堆中子动力学模型中的中子有效代时间。对于以铍作反射层的小型快堆系统,两者的差别可能会十分显著。本文采用微扰法计算了微型钠冷快堆(MFR)的中子有效代时间,并将其推广应用于两点中子动力学模型。该方法的重要步骤是采用微扰法分别计算活性区和反射层中的中子代时间,以及增加反射层引起的反应性增量,这 MCNP gives the instantaneous neutron removal time, but this value is not the same as the neutron effective generation time in the point reactor neutron kinetic model. For small fast reactor systems that use beryllium as the reflector, the difference between the two can be significant. In this paper, the neutron effective generation time of micro-sodium cooled fast reactor (MFR) is calculated by perturbation method, which is extended to two-point neutron kinetic model. An important step of the method is to calculate the neutron generation time in the active region and the reflective layer respectively by using the perturbation method and increase the reactivity increment caused by the reflective layer, which