TRAWA-FEE Simulation of Reactivity Transients in PWRCores

Abstract

TRAWA-FEE is version of Finnish code TRAWA, which soLves the two-group neutron diffusion equations simultaneously with the heat conduction equations and the nonequilibrium separated two-phase hydraulic equations for one or more channels in one dimension. The modifications of original TRAWA code include: new model of control rod movement, additional options of DFDT and OTDT trips based on the Westinghouse methodclogy, time dependent triggering conditions, changes in fuel rod heat conduction model, incorporation of improved DNBR correlations, FEE developed system for group constants generation based on LEOPARD, EXTERMINATOR-2 and SURFIT codes. TRhWA-FEE model was tested on a two loop Westinghouse FWR core of NPP Krsko by simulation of reactivity transients.