A methodology to determinate the HTR (High Temperature Reactor) core seismic behaviour: Experiments and numerical analyses

摘要

The Very High Temperature Reactor (VHTR) core is constituted of prismatic graphite blocks (fuel and reflectors), enclosed within a metallic core barrel. This design is common to several HTR reactor types such as AREVA ANTARES Project, GT-MHR [1] and HTTR [3]. The whole structure is constituted of nearly 2600 blocks and is cooled by pressurised helium gas. The necessity to withstand thermal dilatations and the probable occurrence of graphite shrinkage under irradiation implies the existence of significant gaps between adjacent block columns and clearances in the linking systems between piled up blocks. The seismic behavior of such assembly is largely non linear and includes frictional sliding, impacts and blocks rocking. Nevertheless, it requires a detailed understanding in order to: ? Respect the safety criteria against seismic aggression, which include keeping the graphite blocks integrity and limiting the transversal displacements of the control rod channels. ? Model and control the interactions between the core and the other internal components of the reactor vessel. A research program is performed by CEA, EdF and AREVA, with experimental and theoretical parts. Tests have been performed on a few graphite blocks. The interpretation of the experiments provides the opportunity to test and to choose numerical methods to describe the dynamic behavior and allows the determination of the corresponding parameters. Numerical simulations of the seismic behavior of the whole core lead to first estimations of the kind of movements the blocks can undergo.