A reduced order accelerator for time-dependent segregated neutronic solvers

The deterministic solution of the neutron transport problem entails the coupled solution of several partial differential equations, one for each energy group, direction and/or spherical harmonic. Several techniques have been devised for accelerating the solution of this set of equations, both for time dependent and eigenvalue calculations. This paper describes an acceleration technique based on reduced order models and applicable to the segregated solution of time dependent solutions. In this work the technique is applied to the simple case of multi-group diffusion and tested on two cases of practical interest. It shows performances that are comparable to some commonly employed acceleration techniques. Some potential advantages have been observed for transients with significant flux deformations. In addition, possibly interesting features of the proposed technique are: a relatively easy implementation in general PDE solvers and numerical libraries; its potential applicability to any kind of problem requiring the iterative solution of a system of equations; a flexible implementation with a wide margin for possible modifications.