On-Line Monitoring the In-Core Flux Distribution Using the Eigenfunctions

A method of on-line monitoring the reactor core flux distribution is proposed in this paper. In this method, the real in-core flux distribution is reconstructed on-line using the eigenfunctions of neutron diffusion equation. we expand the real in-core flux distribution by the eigenfunctions with linear combination and calculate the expansion coefficients according to the fixed in-core detector readings which are the real-time response of in-core flux distribution. For only a few expansion coefficients need to be calculated in monitoring process, this method has a high calculation speed to meet the requirement of on-line monitoring the reactor. A program named NLSANM-K (Nonlinear Iteration Semi-Analytic Nodal Method & Krylov subspace method) is encoded to calculate the eigenfunctions. The accuracy of the reconstruction is verified by comparing the reconstructed flux distribution with the results calculated by a core simulator SAMME.