Patent Number: 063273233
Section: description

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 illustrates a nuclear power plant having a single containment building 10 enclosing more than one reactor vessel 12. Each vessel 12 includes a plurality of fuel bundles 14, the bundles including fuel rods (not shown) encased in a fuel cladding 16. Water flows upwardly past fuel bundles 14, where it is heated, and then flows through an outlet nozzle. Containment building 10 is generally cylindrical with a hemispherical or shallow domed roof. In FIG. 2, a second single containment building 10' is illustrated which is generally spherical. Containment building 10 houses the entire primary system of a nuclear reactor including reactor vessel 12, the reactor coolant or steam supply system with steam lines and water or other coolant, pumps, heat exchanges and steam generators. The associated control systems for reactor vessels 12 and both the coolant system and steam Generators are also enclosed within containment building 10. The various systems are customized for a particular reactor and require extraordinary levels of redundancy and backup. Therefore, they are extremely costly to implement at each physical plant location. Containment building 10 is a key barrier associated with nuclear reactor safety. First, containment building 10 must be able to prevent any radioactivity that escapes from a reactor vessel 12 from being released to the outside environment even if its internal pressure is substantially above that of the surrounding ambient air and even if a reactor vessel literally explodes and propels debris toward the walls of the containment building. Second, containment building 10 must protect the rest of the nuclear reactor against outside calamities such as earthquakes, floods, tornadoes, explosions, fires, and even aircraft crashes. Not surprisingly, with such rigid requirements and the associated customization required for each physical location, containment building 10 is one of the most expensive structures of a nuclear power plant. To help defray cost, the conventional wisdom has been to maximize the power associated with a single reactor vessel 12 such that the total power generated by the plant makes the up-front construction and safety costs more economical. However, current nuclear power plants are reaching a practical limit on the amount of energy which can be generated in view of additional added expense and core stability issues. The use of two or more conventional reactor vessels 12 within a single containment building 10 provides significant advantages over the prior art use of a single reactor vessel 12. For example, duplication of construction costs required by having completely separate containment buildings are minimized. As illustrated in FIG. 2, the phantom line 18 represents a typical diameter of approximately 200 feet required for a spherical containment building. The total volume of such a spherical containment building is approximately 4.2 million cubic feet. If the diameter is in creased by only approximately 52 additional feet, the total volume is doubled to approximately 8.4 million cubic feet. Thus, the revised diameter of a building adapted to hold two reactor vessels 12 is less than 1.5 times the original building diameter and preferably only between 1.2 and 1.3 times the original diameter. Further, certain control systems may be shared between each of the reactor vessels 12. Even if the primary systems are maintained completely separate for each of the reactor vessels, certain backup systems and the like may be shared between the vessels, providing a further level of economization. In addition, the use of a multiple number of reactor vessels in various different configurations provides a significantly improved level of control and customization depending on the current needs of the plant. A first embodiment of the present invention, nuclear power plant 20, is illustrated in FIG. 3. Plant 20 includes containment building 10, two reactor vessels 12, a plurality of steam generators 22, and two control systems 24. In the illustrated embodiment, each of the reactor vessels 12 and resulting generated electrical power is controlled completely independently of the other reactor vessel. As a result, energy generated by each reactor vessel 12 is converted to electrical power using coolant or steam supply systems 26 associated only with that reactor vessel as well known in the art. However, the two nuclear reactors advantageously share a single containment building, reducing cost. Further, having two such reactors within a single structure makes further redundant control or safety systems more cost effectively shared between each of the reactors. A second embodiment of the present invention, nuclear power plant 28, is illustrated in FIG. 4. Plant 28 is an example of a partial joint control philosophy involving two or more reactor vessels 12 within a single containment building 10. Each of the reactor vessels 12 has its own reactor vessel control system 30 and its own coolant or steam supply system 31. However, the two reactor vessels share a common feedwater heat exchange system with header 32. A plurality of steam generators 22 are associated with header 32. A steam generator control system 25 may also be provided. As a result, power generated from either one of the reactor vessels may be used to supply steam to the same steam generator by means of the common header 32. Thus, power may be most efficiently generated using a combination of one or more of the reactor vessels. FIG. 5 is an example of third embodiment of a nuclear power plant 34 having an integrated control philosophy. A single control system 36 is used to operate two reactor vessels 12 within a single containment building 10 sharing a common coolant system 38. Steam generators 22 are integrally connected to common coolant or steam supply system 38 to provide electrical energy. More precise control of the entire plant is possible while reducing the expense of having redundant primary systems performing the same function for only one reactor vessel at a time. Finally, FIG. 6 is an example of how power may be generated using two steam generator turbines in parallel. Thermal power in the form of steam is generated at location 40 which then passes through heat exchanger 42 having a feedwater coolant system. The heat turns the water in the feedwater coolant system to steam which is then routed through turbines 44 by means of lines 46 where it is used to generate electricity. The remnant energy within the steam passes through condenser 48 by means of lines 50 with the feedwater returned back to heat exchanger 42 by means of line 52. If necessary, turbines 44 may be partially or completely bypassed using steam bypass line 54 which represents a reactor power cut back such that all or part of the thermal energy generated at location 40 is immediately released through condenser 48. Typically, a small amount of steam is extracted from turbines 44 or from lines 46 to pre-heat feedwater flowing through line 52. Preferred embodiments of the present invention have been disclosed. A person of ordinary skill in the art will realize, however, that certain modifications and alternative forms will come within the teachings of this invention. Therefore, the following claims should be studied to determine the true scope and content of the invention.