Optimization of shadow shield and analysis of radiation characteristics for nuclear powered spacecraft

Abstract

The layout of nuclear-powered spacecraft is very different from the layout of nuclear reactors used on Earth, so the design principle is also different. Taking nuclear-powered spacecraft as the object, this paper studies the coverage of the shadow area formed by the shield and distribution of neutron fluence and photon dose in the shadow area. In this paper, a nuclear power spacecraft model with a width of 6 m and a length of 25 m is built. The Monte Carlo method is used to calculate the transport of neutrons and photons, and the distribution of neutrons and photons in space is obtained. The coverage of the shadow area formed by shields with different widths is obtained, and the main factors affecting the width and angle of the shadow area are summarized. When the diameter of the shield decreases, the width of the shadow area also decreases, and the angle of the shadow area decreases, which greatly reduces the area of the shadow area. The distribution of neutron fluence and photon dose in the shadow area is obtained. At the end of the truss, the maximum value of the photon dose is 1.03 × 10-4 Gy∙s-1, and the average value is 6.42 × 10-5 Gy∙s-1. The maximum value of the neutron fluence rate is 1.01 × 104 n∙cm-2∙s-1, and the average value is 6.18 × 103 n∙cm-2∙s-1. And the influence of spacecraft structure on radiation is analyzed. The truss and droplet emitters have a greater impact on photons, and the heat sink and droplet emitters have a greater impact on neutrons. Based on the above work, a local shield scheme is proposed to reduce the mass. After being blocked by local shield, the photon dose is reduced to 1/10 and the neutron fluence rate is reduced to 1/6.