Reactor reactivity calculations with simplified-P3 and perturbation theories

A new method to calculate reactivity of nuclear reactors through combining the simplified-P3 (SP3) and perturbation theories is proposed. The focus of this study is the sodium void reactivity calcula-tions in the fast spectrum reactors. Verification of this new method was conducted with an OECD/NEA benchmark, which contains four sodium-cooled fast reactors differing in fuel type and core size. Sodium void reactivity attribution analysis indicates that more accurate prediction of the scattering and leakage components of reactivity can be obtained with the new method compared to the diffusion-perturbation method, and that the computation time is reduced compared with the SN- perturbation method. A term having an unclear physical meaning in the SP3-perturbation method was investigated using a transformed SP3 equation set which is different from the widely used form. Results suggested the equation derivation and code implementation are successful, and the new method shows obvious advantage in component-wise reactivity calculations.