Study of VVER Steam Generator Operation in Condensation Mode with Non-condensable Gases Effect in Case of Twenty-four-hour Accident Process

摘要

The design verification of the heat removal efficiency from VVER-1200 reactor (NPP-2006 project) in case of primary circuit leaks and operation of passive safety systems only has been performed on the base of computational simulation of the interrelated processes in the reactor and containment during twenty-four hours after the accident. Computational simulation has been performed in consideration of the negative non-condensable gases effect on steam generator (SG) condensation power. The main sources of non-condensable gases in the primary circuit are nitrogen arriving at the circuit, as hydroaccumulators of the first stage actuate and products of radiolysis of water. The feature of NPP-2006 passive safety systems operation is that during the system of hydroaccumulators of the second stage (HA-2) emptying the spontaneous withdrawal of gas-steam mixture takes place from steam generators into the volume of HA-2 tanks. The calculations carried out by the thermal hydraulic codes have revealed sufficiency of such volumetric gas-steam mixture flow rate to maintain necessary SG condensation power. To confirm the calculated investigation results, the experiment on a HA2M-SG test facility has been carried out. The basic results of experimental studies are presented in the report. As a result of the research, carried out at the HA2M-SG test facility, the experimental substantiation has been obtained that in the case of emergency leak SG’s have condensation power sufficient for effective heat removal by PHRS system from reactor.