Assessing the effects of switching from multi-channel to three-dimensional nodalisations of the core in TRACE

• 1D and 3D nodalisations of the reactor core are compared for PWR LOCA scenarios. PCT generally significantly lower than multi-channel models. CCFL behaviour at upper tie plate explains many observed differences. Modern thermal-hydraulics (TH) systems analysis codes increasingly being updated to include three-dimensional (3D) TH components towards capturing complex flow phenomena in large light water reactors (LWRs). These becoming popular modelling pressure vessels cores since they potentially offer a more realistic representation of, example, effects asymmetric loop flows injection, which cannot be captured using traditional Experience suggests, however, there may unexpected side upgrading from In this paper, we present comparative results demonstrating our experiences switching US-NRC system code TRACE. We series studies representative loss-of-coolant-accident (LOCA) see clear trend scenarios considered. particular, peak cladding temperature (PCT) is models cases. Counter current limitation (CCFL) appears one driving This is, not universal; For surge line break scale test facility (LSTF), heterogeneities lead hot regions core, model. cores, appear represent reality closely. smaller cross-sections, validity TRACE’s prediction questionable. Specific guidelines therefore needed help TRACE users select most appropriate nodalisation different geometries.