Theoretical Study of Steady State Neutron Flux Re-Construction in ADS Subcritical Reactor by Using Higher-Order Modes

Abstract

Neutron flux in Accelerator Driven Subcritical Reactor (ADS) is formed by superposition of fundamental and higher-order modes neutron flux, which provides the physical foundation of modes expansion based studies in ADS subcritical reactor characteristics. Based on the bi-orthogonal properties of forward and ad-joint modes, modes expansion theory for steady state neutron flux in ADS subcritical reactor is established in this paper, and numerical studies on three dimensional four groups ADS subcritical reactor diffusion problem are performed. Results indicate that λ and prompt α modes can effectively re-construct steady state neutron flux of ADS subcritical reactor, neutron flux re-construction accuracy is enhanced by increasing expansion number of modes. Compared with prompt α modes, λ modes are more appropriate for steady state neutron flux re-construction. Since the symmetries of external neutron source and core pattern in this paper, only modes that have symmetrical properties have contributions to steady state neutron flux.