Patent Number: 043222684
Section: summary

The present invention relates generally to heat exchanger cooling systems, and more particularly to a novel cooling system for a gas-cooled nuclear reactor wherein primary and auxiliary cooling loops are provided with a common flow return duct to return coolant to the reactor core, and including a flow diverter common to both the primary and auxiliary coolant loops and selectively operable to control coolant flow through a selected one of the primary or auxiliary coolant loops while isolating the other of the loops. It is a conventional practice in gas-cooled high temperature nuclear reactors to circulate a coolant gas, such as helium, within the power loop, i.e., a closed loop containing the reactor core and a heat exchanger in the form of a steam or vapor generator, through a ducting system by means of main or primary circulators. For emergency cooling of the gas coolant, as in the case of a malfunction or shutdown of the steam generator, independent auxiliary cooling loops are frequently employed consisting of auxiliary circulators, auxiliary heat exchangers and a ducting system for the auxiliary cooling loop which is independent of the primary cooling loop. The primary and auxiliary circulators are generally installed in different cavities or penetrations within the reactor vessel. While such systems have proven capable of providing sufficient primary and emergency auxiliary cooling for the heated coolant gas after it is passed through the active reactor core, such independent cooling loops add substantially to the overall cost of a nuclear reactor power system. The present invention has as one of its primary objects the provision of a novel cooling system for a gas-cooled nuclear reactor which employs primary and emergency auxiliary cooling loops sharing common cavity, return duct and diverter valve means resulting in significant economic advantages over prior gas-cooled nuclear reactor cooling systems. A more specific object of the present invention is to provide a novel cooling system for a gas-cooled nuclear reactor which employs primary and emergency auxiliary cooling loops having a common flow return duct to the reactor core and a single flow diverter valve located at the junction of the common return duct with the primary and auxiliary cooling loops so as to allow selective isolation of one of the loops while facilitating coolant flow through the other of the loops. Still another object of the present invention is to provide a novel cooling system for a gas-cooled nuclear reactor wherein primary and emergency auxiliary cooling loops include a common vertical cavity in a prestressed concrete reactor vessel, the primary and auxiliary cooling loops being connected to a common coolant return duct at a junction in which is disposed a diverter valve normally isolating the coolant within the primary coolant loop but being selectively operable to divert flow of coolant gas from the reactor core to the emergency auxiliary cooling loop while isolating the primary cooling loop. A feature of the present invention lies in the provision of primary and emergency auxiliary cooling loops in a gas-cooled nuclear reactor wherein the loops include a common vertical cavity housing both a circulator for the primary cooling loop and a circulator for the emergency auxiliary cooling loop. A single return duct common to the primary and auxiliary loops houses a flow diverter valve operative to selectively control coolant flow through the primary or auxiliary cooling loops and their associated circulators whereby to eliminate the need for an isolation valve normally located at the circulator associated with the emergency auxiliary cooling loop. Another feature of the gas-cooled nuclear reactor cooling system in accordance with the present invention lies in the provision of a novel diverter valve located at the junction of a common return duct with a cavity in the reactor vessel which houses both the primary and auxiliary circulators, the diverter valve being operable by means externally of the reactor vessel to selectively isolate the auxiliary cooling loop from the primary coolant loop.