Validation of coupled neutron kinetic/thermal-hydraulic codes. Part 1: Analysis of a VVER-1000 transient (Balakovo-4)

Three-dimensional hexagonal reactor dynamic codes have been developed for V VER type reactors and coupled with different thermal-hydraulic system codes . In the EU Phare project SRR1/95 these codes have been validated against r eal plant transients by the participants from several countries. Data measu red during a test in the Balakovo-4 VVER-1000 have been analysed by coupled codes. In the test, one of two working feed water pumps of the steam gener ators was switched off at nominal power. The steady-state assembly powers m easured before and after this transient are reproduced by the codes with a maximum deviation of about 5%. The time behaviour of the most safety-releva nt parameters, such as total fission power, coolant temperatures and pressu res is well modelled. Thermal-hydraulic feedback effects observed in the me asurement are described by the codes in a consistent manner. The analyses h ave shown, that an accurate treatment of the heat transfer from the fuel ro ds to the coolant is important. In all, the results have increased the conf idence in the coupled code analyses of VVER-1000 transients. (C) 2001 Elsev ier Science Ltd. All rights reserved.