Experimental and Theoretical Tools to Support the Development of High-Performance LWR Fuel Elements

Abstract

The fluid-dynamic optimization of fuel elements for light water reactors requires advanced CFD models and experiments with sufficiently high-resolution instrumentation. An overview is given on novel developments in this field at the ETH Zurich and the Paul Scherrer Institute. Instrumentation is based on wire-mesh sensor technology and neutron tomography, which are used in adiabatic tests. Theoretical approaches pursued are liquid film models for boiling water reactor conditions based on RANS simulations of the vapor flow, coupled with a simplified mass transport model for the liquid phase and single-phase LES to predict turbulent coolant exchange between neighboring sub-channels. LES coupled with surface tracking techniques is on the way towards fundamental modeling of flow boiling, together with solving conjugate heat transfer. Existing tomography with cold neutrons is complemented by exploring the possibilities of imaging with fast neutrons.