Study on Heterogeneous Effect Correction Methods of Control Rod Assembly in Fast Reactor

The control rod assembly is an important part of the fast reactor control system and safety protection system. The accurate solution of the fast reactor control rod worth is very important. The direct volume homogenization method is used in the calculation of the fast reactor few�group homogenization constants based on the PASC�5 code, which will lead to a serious overestimation of the control rod worth, and the heterogeneous effects of the control rod assembly must be corrected. Based on the idea of group constant correction, the applications of three methods including volume�flux weight, reaction rate ratio preservation, and reactivity preservation were studied in the correction of heterogeneous effects of fast reactor control rod assembly in the paper. Based on the two�dimensional characteristic line code, the calculation code named FRHP for the group constant correction was developed. Tested and verified by the China Experimental Fast Reactor case, the corrected control rod worth calculation results are in good agreement with the MCNP calculation reference results, indicating that the three methods can effectively correct the heterogeneous effects of the control rod assembly, among which the reactivity preservation method has the best correction effect.