控制棒对核动力航天器辐射屏蔽特性的影响

Influence of control rods on the radiation and shielding characteristics of a megawatt nuclear-powered spacecraft

针对控制棒及其导向管贯穿阴影式屏蔽体的情况,本文进行了核动力航天器全场辐射屏蔽特性的分析,并提出局部屏蔽的优化方案。利用蒙特卡罗方法在核动力航天器全场范围内对中子与光子进行输运计算,求解得到控制棒吸收体处于不同位置时的中子注量率与光子剂量分布情况,分析了控制棒及其导向管对阴影屏蔽体的屏蔽特性及航天器全场辐射特性的影响,并针对辐射薄弱点提出了局部屏蔽优化方案,对优化后的方案进行了计算验证。结果表明:控制棒导向管垂直贯穿屏蔽体会导致仪器平台辐射剂量超限值,极端工况下光子剂量达到限值的10倍,中子注量达到了限值的1.8倍。利用局部屏蔽体可以有效消除控制棒导向管带来的辐射剂量超限问题,能在控制质量增幅的情况下保证仪器平台所处区域的辐射安全。

This study analyzes the full-field radiation shielding characteristics of a nuclear-powered spacecraft when the control rod and its guide tube penetrate a shadow shield and proposes an optimization plan for local shielding.The Monte Carlo method is used to complete the transport of neutrons and photons within the entire field of a nucle-ar-powered spacecraft,obtaining the neutron fluence rate and photon dose distribution at various positions of the control rod absorber.The influence of the control rod and its guide tube on the shielding characteristics of the shad-ow shield and the full-field radiation characteristics of the spacecraft is analyzed.Furthermore,a local shielding op-timization scheme is proposed for the radiation of weak points,and the optimized scheme is calculated and verified.The results show that if the guide tube of the control rod vertically penetrates the shielding body,the radiation dose of the instrument platform will exceed the limit value.In extreme cases,the photon dose and the neutron fluence will reach tenfold and 1.8-fold the limiting value,respectively.The arrangement of local shields can effectively eliminate the problem of the radiation dose exceeding the limit due to the guide tube of the control rod and ensure the radiation safety of the area where the instrument platform is located while controlling the mass increase.