Fuel Assembly Flow Blockage in a LFR Reactor Core: CFD Modelling and Preliminary Numerical Analysis

In the context of GEN-IV Heavy Liquid Metal safety studies, the flow blockage in a Fuel sub-assembly is considered one of the main issues to be addressed and the most important and realistic accident for LFR Fuel Assembly. The present document is a first step towards a detailed analysis of such phenomena, and a CFD model and approach is presented to have a detailed thermo-fluid dynamic picture in the case of blockage. In particular, a careful comparison is presented between open square-lattice grid-spaced elements (without wrap) and triangular lattice, hexagonal wrapped, grid-spaced fuel assembly. At this stage, the details of the spacer grids have not been considered, but a conservative analysis has been carried out basing on the main geometrical and physical features. Reactivity feedback, as well as axial power profile, has not been considered here.