EAC-analysis of hypothetical LOF and TOP accidents with emphasis on the ICE-type finite element hydrodynamic module EACMAND

EAC is a multichannel modular computer code oriented towards the simulation of hypothetical whole core accidents in LMFBRs (e.g. loss of flow or transient overpower events). The code presents itself as an informatic support receiving various stand-alone modules which are put together to become interactive in the framework of a whole core model. Neutronics, fuel behaviour and sodium thermohydraulics are the main phenomena which interact during the initiating phase of almost all hypothetical whole core accidents. The scope of this paper is to illustrate some of the physics which lies behind the assembling process of such codes. As a matter of fact modifications may be necessary in some of those modules in order to account for new boundary conditions (e.g. on the inlet pressure instead of the inlet velocity) and new heat source specifications (e.g. clad-coolant heat transfer instead of given power history). Attention is focused also to the computational aspects which should lead to the usual compromise between improved versatility and accuracy together with reduced CPU-time consumption. Along these lines it is shown that EAC makes realistic predictions of the neutronic behaviour of the whole core: the resulting temperature distributions in fuel, structures and coolant are then the leading parameters for further thermo-mechanical study towards the accident termination. Emphasis is given in particular to the homogeneous boiling model EACMAND which is discretized in a ICE-type finite element format. (orig.)