In the PSB-VVER Integral Test Facility (ITF), extensive experimental investigations on the thermal hydraulic behavior of a VVER-1000 type reactor under LOCA accidents have been carried out during 2001. The general aim of the experiments is to contribute to a better understanding of accident sequences and to provide a detailed data base for the validation of Russian and Western computer codes. This paper presents the results of an 11% cold leg break experiment (CL-11-05) assuming loss of off-site power. The presented experiment belongs to a set of tests with a spectrum of break area in the PSB cold leg carried out in the summer 2001. The results of the post-test analyses using TRAP code are presented. A short description of the TRAP code mathematical model is also given.

The effect of thermal contact resistance in the elements of the graphite stack of the RBMK reactor on moderator temperature is studied. It is shown that estimation of the thermal contact resistance improves the accuracy of calculation of the graphite moderator temperature.