Analysis of emergency situations caused by BN-800 primary circuit pressure pipe depressurization

The results of the analysis of emergency situations caused by BN-800 pressure pipe depressurization are presented in this paper. The Russian fast reactor BN-600 and BN-800 designs have characteristic features that influence the processes during the primary circuit pressure pipes depressurization: - Individual suction of primary circuit main circulation pump (MCP); - Safeguard housings at the diagrid and pressure pipes; - Pressure pipes leak detection system; - Safeguard devices in the support belt. The results of the analysis of emergency situations and their consequences from the viewpoint of their effect upon the core and support belt are presented. The following initial events are assumed: - A leak of 0.5 mm equivalent diameter (DN) in the pressure pipe, as a result of an initial defect in the pipeline weld penetration through the whole wall thickness; - Postulated ruptures of pressure pipes of 55 mm equivalent diameter (DN 55), DN 120, DN 200; - Instantaneous guillotine rupture of one of the six pressure pipes DN 600 with moving apart of the pipeline ends (outflow from two DN 600 sections). The analysis of all the aforementioned events shows that reactor safety is secured in all situations, including the instantaneous guillotine rupture of one DN 600 pipeline (sodium boiling and fuel melting do not occur). (author)