Analysis Of The Core Compaction Phenomenon

The compaction of the bundle of core assemblies is an important aspect of the core design particularly for the next generation LMR. The core deformation, caused by dynamic condition like the seismic motion, may determine, at large or small extent, an assembly compaction generally characterized by a radial inward displacement, and subsequently result in a possible insertion of reactivity. The aim of this study is to investigate the deformation of core (and restraint system) geometry of the Advanced Lead Fast Reactor European Demonstrator - ALFRED (300 MWth). Numerical analyses have been carried out by the finite element MSC©Marc code to simulate the mechanical behaviour of the overall reactor system and, specifically, of the main components of the inner vessel, such as the lower and upper grid, the inner vessel, the support skirt, etc.. Suitable boundary and initial conditions, such as that one related to the core sub-assemblies mass, the restrictions imposed to the geometrical in-structures connections, etc. have been assumed to numerically investigate the dynamic response of the structures, since confidence was established by sensitivity analyses of size and type of the adopted elements. The results indicate that the stresses overcome the yielding limit particularly in the upper part of the inner vessel, close to the flange support, in the upper grid and in the annular area neighboring the nozzle penetration. The displacement resulted of course variable along the height of the inner vessel, with a mean value of about 2 cm around the core assemblies. This research activity was developed and financed by the Italian Ministry of Economic Development (MSE) as part of the activities carried out in the framework of the AdP MSE-ENEA-CIRTEN PAR 2013.