CATHARE (Code for Analysis of THermalhydraulics during an Accident of Reactor and safety Evaluation) is a two-phase thermal-hydraulic simulator in development since 1979 at CEA-Grenoble as part of an agreement between the CEA, EDF, AREVA and the IRSN. The software is currently in its second major revision and is used, in particular, in pressurised water reactor safety analyses, the verification post-accidental operating procedures, and in research and development.
The CATHARE2 simulator has a modular structure capable of operating in 0D, 1D or 3D. It is capable of modelling any type of reactor (PWR, RBMK, VVER, etc.), several types of system loop (including BETHSY and LOFT) and many analytical experiments (CANON, ECTHOR, MARVIKEN, PERICLES, etc.). It also contains a module capable of simulating the behaviour of a nuclear reactor containment vessel in the event of a break in either the primary or secondary circuit.
The software is based on a two-phase model with six equations (conservation of mass, energy and quantity of movement for each phase). The numerical method used is implicit in 0D and 1D, and semi-implicit in 3D. This robust and efficient method provides a good compromise between accuracy and computing cost.
The successive versions of the code were validated in a two-step process: Qualification in separate-effect experiments (CANON, ECTHOR, MARVIKEN, PERICLES, etc.) followed by verification of the overall behaviour of the software in system experiments (particularly BETHSY and LOFT).
CATHARE2 is capable of simulating the physical phenomena that occur during a loss of coolant accident (small and large break LOCA), steam generator tube rupture (SGTR), feed water line break (FWLB), residual heat removal failure (RHR), or steam line break (SLB). For the investigation of transients leading to severe reactor core degradation (severe accident), CATHARE2 has been linked to the ICARE software. CATHARE has also been integrated into the IRSN SOFIA (Simulateur d’Observation du Fonctionnement Incidentel et Accidentel) accidental simulator for the EDF reactors. This simulator is used to train specialists, prepare crisis management exercises, and to carry out studies in support of reactor assessments.
Version 3 of the simulator is currently under development as part of the larger NEPTUNE platform project (which will itself form part of the generic P@L/SALOME platform). Co-financed by EDF, the CEA, the IRSN and AREVA-NP, the main purpose of NEPTUNE is to provide a new generation of tools for nuclear thermo-hydraulic two-phase (water/steam) simulations. With results due in 2010-2015, NEPTUNE will be capable of operating on several scales (local, component and system) from 3D local to 0D macroscopic. The scope of NEPTUNE includes single phase functionality in order to provide for a continuous passage towards two-phase conditions, but it does not include large eddy simulation (LES) or direct numerical simulation (DNS). Eventually, the NEPTUNE platform should be able to link different scales together, in particular to enable zooming into critical areas.