Keywords: nuclear reactors, multi–physics modelling, multi–scale modelling, deterministic methods, neutron transport, fluid dynamics, heat transfer, thermal hydraulics, nuclear energy, nuclear power, infinite lattice, single fuel assembly
Multi–physics modelling of nuclear reactors: current practices in a nutshell
Current practices in the nuclear industry to model the transient behaviour of nuclear reactors are based on the use of different solvers for resolving the different physical fields, and to some extent the different scales. The overall time–dependence is computed by a coarse–mesh neutronic solver coupled to a coarse–mesh thermal–hydraulic solver. The meso–scale information in the thermal–hydraulic solver is provided by empirically–derived correlations, which are strongly dependent on the flow regime. The neutronic solver makes use of homogenised and condensed macroscopic cross–sections, which are tabulated in advance as functions of local instantaneous and history variables. The pre–computation of such macroscopic cross–sections is carried out by a neutron transport solver modelling an infinite lattice of a single fuel assembly. The entire modelling procedure involves many intertwined steps, each step having its own set of approximations. The purpose of the present paper is to clearly highlight such steps and the corresponding approximations.