A note on the numerical solution procedures used in the LAURA computer code and in other codes for nuclear-reactor thermal hydraulics

Distinguishing features of the numerical formulations, and of the solution procedures, employed in the loop analysis of unsteady reactor and ancillary equipment behavior (LAURA) computer code, and of their similarities to and distinctions from those of other thermal hydraulics codes are described. Attention is concentrated on the distinction between fully-implicit and partially-explicit formulations, and on the question of how many interactions are accounted for in the pressure-correction equation. It is shown that fully-implicit formulations permit adequate explorations of what grid and time step are necessary for accuracy. Because of the way in which nuclear safety codes are constructed, the grids which they are forced to employ, for economic reasons, are far too coarse to give any grounds for belief in their numerical accuracy.