Patent Number: 051065746
Section: summary

This invention was made in part by an employee of the University of New Mexico. BACKGROUND OF THE INVENTION 1. Field of the Invention (Technical Field) The invention relates to nuclear reactors for use in space and more particularly to those which can be fueled, emptied and refueled in space and which incorporate redundancy and which are safe to launch and operate. 2. Description of the Related Art Including Information Disclosed under 37 C.F.R. .sctn..sctn.1.97-1.99 (Background Art) Solid core reactors, currently proposed for space power applications, have a single core structure with inlet and outlet coolant ducts. Such designs have the disadvantages of a single point failure, since a break in or rupture of a single pipe feeding or removing coolant from the core would result in a complete loss of coolant. Subsequently, heat generated by the radioactive decay of fission products would overheat the core structure beyond its design limit and might melt the core in the absence of an auxiliary core cooling system. Some designs employ an independent auxiliary cooling loop to remove the decay heat from the core in case of a failure of the primary loop. Although employing an auxiliary loop could avoid degradation of the core structure due to overheating, it increases the size and mass of the core and requires a complete shutdown of the reactor, thereby terminating the mission. An early termination will naturally result in significant losses in resources and scientific opportunities. Another drawback of current solid core reactors is the need for at least two independent safety mechanisms, each of which is capable of shutting down the reactor during emergency. With these safety mechanisms in place, reactors are designed to remain subcritical during a launch abort resulting in a water immersion or core compaction. SUMMARY OF THE INVENTION (DISCLOSURE OF THE INVENTION) In accordance with the present invention there is provided a gas cooled nuclear reactor suitable for use in space. The reactor has a housing comprising a plurality of at least three sectors, each sector comprising a container for a reactor core separate and distinct from the reactor cores of the other sectors, each sector being capable of operating and cooled on its own and in cooperation with one or more of the other sectors. Each sector is subcritical for safe launching. Structure is associated with each sector for independently introducing gas coolant into and extracting coolant from each sector to cool the core therein. The reactor further comprises structure associated with each sector for independently fueling, emptying and refueling each sector. The fuel for the sector cores preferably comprises structurally self-supporting pellets, such as spheres. The fueling, emptying and refueling structure can comprise structure for using the vacuum of space in accomplishing fueling, emptying and refueling. In the event of failure of the cooling system of a core in a sector, one or more of the other sectors comprise structure for conducting heat away from the failed sector core and structure for radiating the heat away, thus maintaining sector operation. The sectors are preferably made of Mo, Mo-Re alloy, Mo alloy, Re alloy, or W-Re alloys. One object of the present invention is to increase safety of operation and handling of reactors for use in space. Another object of the invention is to provide for fueling, emptying, and refueling capability for reactors for use in space. Still another object of the invention is to decrease maintenance problems and costs for reactors in space. One advantage of the present invention is that in accordance therewith, the cooling system of one or more reactor core sectors can fail and the reactor will still operate. Another advantage of the invention is that a reactor in accordance therewith is relatively light in weight. Another advantage of the present invention is that operation of a reactor in accordance therewith is at relatively low temperature gradient and consequently at low stress to the materials thereof. Additional objects, advantages and novel features of the invention will be set forth in part in the description which follows, and in part will become apparent to those skilled in the art upon examination of the following or may be learned by practice of the invention. The objects and advantages of the invention may be realized and attained by means of the instrumentalities and combinations particularly pointed out in the appended claims.