CATHARE Approach Recommended by EDF/SEPTEN for Training (or other) Simulators

This paper describes EDF's approach to NSSS thermal-hydraulics - this is the crucial module in a real-time simulator (this constraint relaxes requirements in respect of neutronics) because it determines the simulator's scope of application. The approach has involved several stages: (1) Existing full-scalers (1980-85 design), equipped with a five-equation primary model (about 40 nodes), coupled with a three-equation axial model of the SG secondary side (plus a very simple model for refilling/venting and draining), which can simulate only a small, 2-inch LOCA and up to 15 bar primary-system pressure; (2) SIPA(CT) and the new full-scalers at Fessenheim and Bugey (1990-95 design). These tools feature Cathare-Simu, an outgrowth of CATHARE 1 (six primary-system equations, four secondary-side equations, at least 187 nodes - extended to the steam header, implicit digital processing, possible parallelisation): this model permits simulation of breaks of up to 12 inches and at very low primary-system pressure; (3) SCAR (1995-2000 design) will be adapted from the CATHARE 2 design code (six equations everywhere, non condensables, 2D and 3D modules), and will allow simulator processing of all operating conditions (except for a severe accident, in the strict sense of core melt), including scenarios based on 481 broken primary piping, at atmospheric pressure. Only the fine-modelling capabilities of CATHARE make it possible to add genuine echographies to the traditional Man Machine Interface. (author)