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空间核热推进(SNTP)粒子球床堆(PBR)呈现正的慢化剂温度效应,影响反应堆运行安全。基于PBR堆芯物理模型,采用蒙特卡洛中子-光子输运程序(MCNP)对PBR堆芯慢化剂温度系数进行计算。从中子平衡的角度分析慢化剂升温前后堆芯内中子能谱、中子产生率、中子吸收率和中子泄漏率的变化。结果表明:7Li H升温后,堆芯总的中子消失率(吸收率和泄漏率)的增量要比中子产生率的增量少得多,使得PBR堆芯表现出正的慢化剂温度效应,且低温时正温度系数值较大。
Space nuclear thermal propulsion (SNTP) particle bed reactor (PBR) presents a positive moderator temperature effect, affecting reactor operation safety. Based on the physical model of PBR core, the Monte Carlo neutron-photon transport procedure (MCNP) was used to calculate the temperature coefficient of PBR core moderator. The change of neutron energy spectrum, neutron generation rate, neutron absorption rate and neutron leakage rate before and after moderator warming were analyzed from the viewpoint of neutron balance. The results show that after the 7Li H is heated, the total neutron disappearance rate (absorption rate and leakage rate) increment of the core is much less than that of the neutron generation rate, so that the PBR core exhibits a positive moderator Temperature effect, and low temperature positive temperature coefficient larger.