Trends in thermalhydraulics and in the CATHARE code development

The R and D activity at CEA/DRN/DTP/SMTH in two-phase thermalhydraulics related to reactor accidental transient analysis can be split into two main projects: (1) The CATHARE-SCAR project (this project started in 1979 and has planned developments up to 2003), (2) The advanced thermalhydraulics (started in 1999 and planned up to 2010). The CATHARE 2 code developed jointly by CEA, IPSN, EDF and FRAMATOME has reached a high degree of maturity so that it is now a reference tool used as a support for an increasing number of safety studies for French PWRs, for the EPR project, and for other reactors. As a best-estimate 2nd generation tool and thanks to the quality of the physical modelling, it allows to justify new fuel management, power increase, increase of the combustion rate, etc. Due to the combined increase of numerical performance of the code and of the computers, a unique code can be used for both safety studies and real time plant simulators, reducing maintenance costs. After such an industrial success the same partners decided in 1999 to launch a new project called 'advanced thermal hydraulics' following two considerations: (1) A more local description of the two-phase flows can still improve the predictions (this requires first some theoretical work and will result in a third generation of numerical tools planned for 2010), (2) The increasing computer performance will make it possible to develop such advanced tools. (orig.)