System for the emergency cooling of a pressurized water nuclear reactor core

Claim 1

In a water-cooled nuclear reactor of the type having a reactor vessel and a device for injecting low pressure emergency water into the top of the reactor vessel from a cold water tank, an emergency cooling system being a closed circuit comprising, in series, a low pressure pump connected to the cold water tank, a normally closed upstream valve connected to the pump, a first heat exchanger integrated into the reactor vessel and normally submerged in the reactor water, a three-way valve connected to the upstream valve and to a normally closed valve and a normally open valve which are connected in parallel between the three-way valve and an inlet of the first heat exchanger, the normally closed parallel-connected valve having a much higher flow rate than the normally open parallel-connected valve, a normally closed downstream valve connected to an outlet of the first heat exchanger, and a second heat exchanger connected to the downstream valve and to said cold water tank, the second heat exchanger being supplied with a secondary cooling water flow therethrough for removing heat from water flowing in said closed circuit, and the water injection device being connected to the three-way valve, the three-way valve being operable to supply water from the cold water tank alternatively to said water injection device or to said first heat exchanger.