Research on power flattening method and neutron characteristic analysis of a megawatt-class space gas-cooled fast reactor

Abstract According to the versatility and durability requirements of the deep space missions, the space nuclear reactor (SNR) power system is becoming a more suitable choice compared with traditional solar and chemical power systems in the fields with the larger-scale and longer-life applications. For a megawatt-class space gas-cooled reactor, the power peak factor is a major factor that influences the reactor power and safety. In the present paper, two methods are proposed to flatten the power profile of SNR and the corresponding neutron characteristic of the space gas-cooled fast reactor is analyzed. One is to change the material of the reflector, and the other is to add neutron burnable poisons in the middle of the core. The result reveals that when the reactor is with the same initial reactivity, the power peak factor and the reflector mass of the reactor using Be as the reflector material is smaller than that using the BeO. Adding 5 wt% Gd2O3 in the range of the four layers fuel rods in the center of the reactor, the power profile of the reactor can be flattened greatly, and it can also meet the 10-year lifetime requirement. Finally, through calculation and analysis, one reasonable arrangement scheme of the control rod is proposed. The results can lay basis for the design of the large power space nuclear reactor.