Application of the Burnable Poison in the Design of Space Nuclear Reactor

The previous research showed that the application of burnable poison was helpful to improve the criticality safety of space nuclear reactor (SNR). In order to analyze the worth of burnable poison in the SNR’s design, a model of homogeneous reactor had firstly been built based on the design of SAFE400. Comparing its difference with the real design of SAFE400 through criticality calculation, the precise of our model had been verified. Then the influence of the criticality parameters and immersion accident character parameters for this model had been analyzed for the application of the different burnable poisons (such as samarium, europium or gadolinium). The calculation results had shown that the application of the most of the burnable poisons would soften the neutron spectrum and induced a decrement of reactor’s keff in the beginning of life. However, the immersion accident analysis gave out another result that only the reactor using gadolinium could ensure the criticality safety of reactor after it made its initial keff equal with the design value. Meanwhile, compared with the initial design of SAFE400, in one hand, the burn-up results had shown that the decrement of homogeneous reactor’s reactivity using gadolinium as burnable poison was deceased after the 10 years full power operation; in other hand, its neutron spectrum became more softer with the operation time; and what’s more important, the amount of the burnable poison was not decreased with burn-up during its service life-time. These results implied that the application of the burnable poison (especially for gadolinium) could highly ensure the criticality safety and stable operation of SNR.