Patent Number: 043103855
Section: summary

BACKGROUND OF THE INVENTION A reactor core, of a nuclear reactor, is typically located in a containment vessel having predetermined operating pressure and temperature ranges for normal safe operation of the reactor. The containment vessel is typically provided with heat-transferring fluid coolant which is pumped into the containment vessel adjacent the reactor core, heated by the reactor core, with said heat being utilized in a steam turbine for the generation of electricity. Under certain conditions, the heat-transfer fluid coolant to the core could be interrupted. In this event, the temperature of the core would continue to rise, resulting in a preliminary melting of the core, and upon uninterrupted continuous temperature increase, would cause a complete melt down of the core to a molten bolus of radioactive fuel. This fuel would flow by gravity downwardly from said core and could melt through the bottom of the containment vessel, causing great damage to the nuclear reactor and create extreme danger to public health and environmental safety. Presently, known types of nuclear reactors can be provided with core melt down accepting fluxing or eutectic solute material or device beneath the core to receive the molten bolus of atomic fuel in the event of a melt down; however, presently there is no device which is retrofitable to the primary heat-transfer fluid system to automatically provide the containment vessel with a molten core fuel catcher. Moreover, no such safety device is provided in this manner through the heat-transfer fluid system or by a supplemental system connected to the containment vessel. SUMMARY OF THE INVENTION In the present art of nuclear reactor systems, a failure in the heat-transfer coolant system could cause a melt down of the reactor fuel elements, resulting in the formation of a molten bolus in the bottom of the reactor containment pressure vessel as an immediate prelude to burn through of the vessel by the molten bolus. This bolus presents a large thermal assault on any available materials which would most likely not be sufficient to neutralize the bolus under these conditions. This invention provides a device for preventing the emission of radioactive material into the environment in the event of a melt down and to limit damage to the nuclear power plant. OBJECTS OF THE INVENTION The primary object of this invention is to provide a device which is retrofitable to a nuclear power plant to limit the damage to a nuclear power plant and the environment in the event of a fuel core melt down. It is another object of this invention to provide a fuel element core catcher to receive initial bits and drops of molten fuel as it begins to melt down from the fuel core to provide a gradual thermal assault, shock or challenge to the eutectic solute material, as is calculatedly provided by this invention, and thereby avoiding the otherwise massive thermal shock assault or challenge to the accepting material, device or containment vessel, otherwise accompanying the melt down of the fuel system in the present art of nuclear fuel power plants. It is a further object of this invention to provide a device which is specifically retrofitable to existing nuclear reactor power generating plants to provide the means for preventing the escape of radioactive material and damage to the nuclear plant in the event of a core melt down accident which is not otherwise provided by the original structure of the plant, or which is retrofitable to said plant to augment an existing melt down retainer. An additional object of this invention is to provide a fuel core melt down catcher which is not otherwise provided by the state of the art and existing nuclear energy power plants. Another object of this invention is to provide an emergency melt down core catcher for a nuclear reactor core containment vessel which is responsive to temperature and/or pressure to be operable to provide and position supplemental core melt down catching material within the containment vessel.