Improvements in or relating to protective arrangements for cooling systems

Reference is made to cooling systems in which a fluid is arranged to circulate around the system under pressure through a coolant path that includes a region that requires to be protected against overheating. The system described is stated to be especially applicable to fluid-cooled nuclear reactors, where a breach in the cooling system, leading to a loss of normal circulation, could result in overheating of the reactor core, with serious consequences. Although it is possible to provide for a rapid shutdown of the reactor, and the removal of heat from the core by an emergency cooling system, these operations may take several seconds to become fully effective and during that time the core temperature may have risen to a point where severe damage has occurred. The system provides a protective arrangement comprising means arranged to respond to a reduction in the normally circulating coolant due to a breach of the system and to inject into the system an auxiliary coolant under pressure. Nozzle means are provided for the injection, arranged normally to maintain coolant flow in the normal direction but prevent reversal of flow for a period following reduction of flow. The point of injection of the auxiliary coolant will depend on the part of the cooling system requiring protection. An auxiliary store of coolant under pressure is provided, and the mode of injection may be automatic. The auxiliary coolant may be maintained at a pressure substantially equivalent to the main coolant pressure or at a pressure higher than the main coolant pressure, with a normally closed valve located between the auxiliary coolant vessel and the nozzle means, the valve actuating means being arranged to open the valve automatically in response to a drop in pressure in the system. The normal coolant path preferably has a constriction in the vicinity of the nozzle to aid production of a high pressure region and to ensure substantial reduction in backflow along the coolant path. (U.K.)