Method for computer modeling the core of a nuclear reactor

A method for computer modeling the core of a nuclear reactor, comprising the following method steps:

• dividing the core into a multiplicity of coarse mesh cells including at least one given coarse mesh cell and adjoining coarse mesh cells;
• assigning the at least one given coarse mesh cell a subregion of the core, the subregion having a boundary and containing the given coarse mesh cell and a buffer zone, the buffer zone enclosing the given coarse mesh cell in a horizontal direction and containing at least the coarse mesh cells immediately adjoining the coarse mesh cell;
• dividing the subregion into a multiplicity of fine mesh cells, the fine mesh cells being finer than the coarse mesh cells;
• assigning a first dataset to each coarse mesh cell and, based on the dataset respectively assigned to each coarse mesh cell, calculating a model of the core, including fluxes at the boundary of the subregion by a nodal calculation method in a first computation step;
• assigning a second dataset to each fine mesh cell and, based on the second dataset respectively assigned to each fine mesh cell of a subregion and with fluxes at the boundary of the subregion as calculated in the first computation step, calculating a model for the subregion by a nodal calculation method in a second computation step;
• and
• outputting the model of the core obtained in the first computation step and the model for the subregion obtained in the second computation step.