Full pressure passive emergency core cooling and residual heat removal system for water cooled nuclear reactors

摘要

A water cooled nuclear reactor (10) comprises a reactor core (14), a primary water coolant circuit (24,26) and a pressuriser (46) arranged as an integral unit in a pressure vessel (12). A passive full pressure emergency core cooling and residual heat removal system is provided which comprises a tank (58) having a reserve supply of water positioned above the primary water coolant circuit (24,26) or the reactor core (14). The tank (58) is interconnected to the primary water coolant circuit by a first pipe (74) and a second pipe (68). The first pipe (74) has an inverted U-bend (76) which passes through a water space (48) and a steam space (50) of the pressuriser (46) to form a vapour lock (78). The first pipe (74) and second pipe (68) are also provided with hydrostatic thermal seals (82) and (70). The tank (58) has one or more residual heat removal circuits comprising heat exchanger (60) positioned in the tank (58) and heat exchanger (62) outside the tank (58). Movement of the vapour lock (78) from the inverted U-bend (76) allows cool water from the tank (58) to flow into the primary water coolant circuit and hot water to flow into the tank (58) to be cooled. The vapour lock (78) detects abnormalities in the reactor core (14) and primary water coolant circuit (24,26) and in the water level in the pressuriser (46), and automatically initiates full pressure passive emergency cooling and residual heat removal.