摘要

The article presents application of an autonomous passive residual heat removal system (RHRS) for cooldown of nuclear power plants (NPP) with water-cooled, water-moderated power reactors (WWER 1000). The residual heat is removed via heat exchangers composed of two-phase thermosiphons. The proposed system also provides efficient primary de-pressurization by natural circulation of steam from pressurizer's upper part through emergency gas removal system towards thermosiphon heat exchanger and eventual return of the condensate back to the primary circuit. The results of analytical modeling show, that the suggested passive system provides for timely injection of boric acid solution from hydro accumulators (HAs) and thus sufficient subcriticality margins during the entire reactor installation cooldown process simultaneously maintaining subcooled conditions in the reactor core. The results of analytical modeling of emergency cooldown of the reactor installation during complete, long-term blackout event are presented. It is proved that proposed passive heat removal system provides efficient heat sink and primary de-pressurization. That creates conditions for actuation of emergency core cooling system (ECCS) HAs and maintains adequate subcriticality during the transient along with maintaining subcooled conditions of the primary coolant in the reactor core.