Patent Number: 048636754
Section: claims

1. An inherently safe modular nuclear power system for producing electrical power at acceptable efficiency levels using working fluids at relatively low temperatures and pressures, said system comprising: a reactor module for heating a first fluid;  a heat exchanger module for transferring heat from said first fluid to a second fluid;  a first piping system effecting flow of said first fluid in a first fluid circuit successively through said reactor module and said heat exchanger module;  a power conversion module comprising a turbogenerator driven by said second fluid, and means for cooling said second fluid upon emergence thereof from said turbogenerator;  a second piping system comprising means for effecting flow of said second fluid in a second fluid circuit successively through said heat exchanger module and said power conversion module;  and a plurality of pits for receiving said modules;  each of said modules being elongated and having an upper end and a lower end, and being disposed in a substantially vertical orientation with a lower portion contained in one of said pits;  said reactor module and said heat exchanger module having means for connection with said first piping system near their respective upper ends;  each of said modules including a tank having support means thereon enabling said tank to be installed in an associated pit from above;  said modules being located side-by-side in close proximity to one another to provide compactness for the system while permitting overhead access to each of the modules without interference from any other module;  said reactor module comprising a tank, a core supported within said tank and disposed near the lower end of said tank, a pool of relatively cool liquid contained within said tank surrounding said core, means to selectively permit circulation of said liquid from said pool through said core by natural convection in the event of interruption of flow of said first fluid through said reactor module while inhibiting intermixing of said liquid from said pool with said primary coolant under normal conditions, and a plurality of coolers disposed within said reactor module to remove heat from said pool;  the pit which receives said reactor module being lined with a relatively impermeable material so as to provide secondary containment for said pool so that said core will remain surrounded by said relatively cool liquid in the event of a rupture of said tank;  said piping systems and modules maintaining separation between said first and second fluids;  said core comprising a fuel which imparts a large prompt negative temperature coefficient to the core, which inherently shuts down the reactor in the event of a large reactively insertion;  said second fluid being a member of the group consisting of R-113 and R-114. 2. A system in accordance with claim 1 wherein said means for cooling said second fluid is a recuperator which cools said second fluid without change of phase, said system further comprising a condenser module, said second piping system further comprising means for effecting flow of said second fluid through said condenser. 3. A system in accordance with claim 2 wherein said means for effecting flow of said second fluid through said condenser includes a substantially horizontal straight pipe extending from said recuperator to said condenser to enable said second fluid to flow directly from said recuperator to said condenser without changing direction. 4. A system in accordance with claim 1 wherein said turbogenerator comprises a turbine and a generator supported for rotation on a common vertical shaft, and wherein said means for cooling said second fluid upon emergence thereof from said turbogenerator includes an annular tube bundle defining a central plenum directly beneath said turbine, whereby said second fluid flows downwardly from said turbine into said inlet plenum without changing direction. 5. A system in accordance with claim 4 wherein said means for cooling said second fluid upon emergence thereof from said turbine is configured so that said second fluid flows downwardly into said inlet plenum from said turbine and thence radially outwardly through said tube bundle. 6. A system in accordance with claim 1 wherein said means for cooling said second fluid is a condenser. 7. A system in accordance with claim 1 wherein said means for cooling said second fluid upon emergence thereof from said turbogenerator includes an annular tube bundle defining a central plenum for receiving said second fluid, and wherein said power conversion module is configured to enable said second fluid to flow from said turbine into said central plenum without changing direction. 8. A modular nuclear power system in accordance with claim 1 wherein said fuel comprises uranium zirconium hydride fuel.