Presentation and application of the ESCADRE system

A description is given of the current status of the ESCADRE system, a set of realistic computer codes for studying severe accidents at PWRs. The ESCADRE system is designed to simulate the physics of fission product transfers and the thermohydraulics governing the kinetics of these transfers. Codes describing the thermohydraulics of the core, the primary circuit and the containment (taking into account the safety systems and the corium-concrete interaction) are presented, followed by the fission product transfer codes (emission from degraded fuel, steam and aerosol behaviour, transport outside the containment). The ESCADRE system is now operational and has been used to determine and analyse the radiological consequences of several severe accident scenarios at a PWR. It makes it possible to calculate the thermodynamics of the vector fluid governing the fission product transfer phenomena as a function of the accident scenario being studied, then to calculate fission product transfers (suspended concentration) from the core to possible release to the environment. The possible applications are manifold and include the estimation of radioactive releases - in terms of the nature, quantity and kinetics - in order to check the validity of population evacuation plans, and the study of the effectiveness of intervention procedures and measures which the operator plans to use to minimize the consequences of severe accidents. Moreover, the ESCADRE system will make it possible to perform a number of parametric calculations on sensitivity to little-known data or to data which vary considerably according to the scenarios. These parametric calculations will improve the databases which are a necessary part of the decision aiding tools used at the Technical Emergency Centre of the Institute of Nuclear Protection and Safety. (author). Poster presentation. 14 refs, 5 figs