Study of minor actinides effect on kinetic parameters and reactivity coefficients in an accelerator driven system

Abstract

The effect of minor actinides (MA) on kinetic parameters and reactivity coefficients in an accelerator driven system (ADS) is analyzed in this paper. The Italian XADS reactor with (U,Pu,MA)O2 fuel is considered as the case study of the problem, which consists of a subcritical liquid metal reactor and a proton accelerator. A new Monte Carlo method is applied to calculate the kinetic parameters, i.e., effective delayed neutron fraction (βeff), mean neutron generation time (Λ). Furthermore, Doppler coefficient (αD) and coolant feedback coefficient (αC) are obtained by calculating effective multiplication factors (keff) at various temperatures. To verify the adopted method, calculations are performed on several benchmarks. The calculated values of the new method are compared with those obtained from prompt method, 1/v absorber method and reference data. The results show that the new method could accurately calculate kinetic parameters for both critical reactors and subcritical reactors with an external source. The different percentage of MA in the fuel is studied to determine its effect on kinetic parameters and reactivity coefficients for XADS. When the content of MA reaches 5% in the fuel, the values of βeff and Λ decrease by about 18% and 31%, respectively. With the increase of MA content from 0 to 5%, the value of α¯D varies from −0.56 pcm/K to −0.36 pcm/K, and the value of α¯C varies from −2.11 pcm/K to −1.73 pcm/K.