Patent Number: 051788217
Section: summary

FIELD OF THE INVENTION This invention relates to water cooled nuclear fission reactors of the so-called boiling water type. Boiling water nuclear reactors comprise a steam generating plant wherein reactor water coolant is circulated through a core of heat producing fissionable nuclear fuel to transfer thermal energy from the fuel to the coolant water and thereby produce steam. The steam is then used to drive turbines and other machinery employing steam, such as for electrical power generation. BACKGROUND OF THE INVENTION Due to the prodigious quantities of thermal energy produced by fissioning nuclear fuel, it is imperative to maintain the fuel core of commercial water cooled nuclear fission reactors submerged within heat transferring coolant water. The conveyance of heat out away from the energy producing fuel core by means of circulating coolant water is needed to preclude the possibility of hazardous conditions or reactor damage such as could occur with an overheating meltdown within the fuel core of the reactor plant. Such a potentially destructive occurrence can result from a loss of coolant accident (LOCA) caused by an extensive breach of a major reactor coolant receptacle or conduit. To cope with this theoretical accidental event, commercial water cooled nuclear fission reactors are provided with large reservoirs of water available for supplying supplementary coolant water to the reactor vessel for cooling the fuel core and maintaining lower or normal operating temperatures. A variety of safety measures have been proposed or employed to activate and operate systems for supplying or injecting this supplementary coolant water as needed to the fuel core for replacing or supplementing any loss of the original coolant water due to some mishap. A typical arrangement in commercial water cooled nuclear fission reactor plants for incorporating standby safety systems which feed or inject auxiliary coolant water to temper the fuel core temperatures utilize an apt gas, such as nitrogen, for a propellant to drive the supplementary liquid water or a boron solution from a source or reservoir through communicating conduits into the reactor vessel. Thus, auxiliary coolant water or an aqueous boron solution is maintained within a closed vessel or tank under sufficient gas pressure to drive the liquid contents into the reactor vessel through an appropriate arrangement of conduits upon a manually or automatically actuated signal responding to a malfunction within the reactor. However, such systems are prone to leakage and loss of gas for propelling coolant water as well as prone to malfunctioning of the manual and/or mechanical or electronic means for actuation of the system. Another means comprises gravity feed arrangements employing elevated vessels of auxiliary coolant water. However loss-of-coolant accidental events can sometimes result in overheating which in certain cases causes increased pressures above the already high pressures within the reactor pressure vessel. The occurrence of such elevated pressure conditions inhibits gravity feeding of coolant water into a highly pressurized reactor vessel. SUMMARY OF THE INVENTION This invention comprises an improved standby safety system for water cooled, nuclear fission reactor plants. The improvement of the invention comprises a totally passive delivery means for introducing a standby supply of auxiliary coolant water into the fuel core region of the nuclear reactor pressure vessel. Additionally this invention comprises a unique arrangement of auxiliary coolant water reservoirs housed within the reactor pressure vessel combined with means for providing inherently passive action or motivating force for supplying auxiliary coolant water to deal with a reactor emergency or malfunction. OBJECTS OF THE INVENTION It is a primary object of this invention to provide an improved coolant water standby safety supply system for nuclear fission reactor plants. It is an additional object of this invention to provide a coolant water standby safety supply system for water cooled nuclear fission reactor plants having a passive delivery means. It is a further object of this invention to provide a standby safety supply for water cooled nuclear fission reactor plants having an inherent passive gas propellant source and application system that enhances safe performance as well as economic benefits. It is a still further object of this invention to provide a liquid standby safety supply system for water cooled nuclear fission reactor plants having an improved arrangement of coolant water delivery which is actuated passively upon occurrence of a malfunction. It is also an object of this invention to provide improved multiple liquid standby safety supply for water cooled nuclear fission reactor plants providing for auxiliary application of coolant water to the fuel core by means of a passive system providing an inherent source of propellant gas during any period of core overheating due to a loss of coolant accident.