THERMAL-HYDRAULIC ANALYSES OF PARTIAL GDH BREAK USING BEST-ESTIMATE CODE RELAP5

The paper presents the results of the thermal-hydraulic analyses of the postulated Group Distribution Header partial break at RBMK-1500 type reactor for different reactor operation stages: operable reactor and reactor during shutdown, when the amount of accumulated heat in the core is still sufficiently high, however the protection system preventing the core from low flow is deactivated. For both cases the uncertainty analysis is performed. Results of the analyses show that the reactor core will be reliable cooled in the case of partial GDH break for all possible reactor stages and core power.