Patent Number: 040509842
Section: description

DETAILED DESCRIPTION OF THE INVENTION In FIG. 1 a cylindrically-shaped pressure-tight safety tank 1 formed of steel concrete is provided with a dome-shaped top 2. Located centrally inside of and spaced inwardly from the safety tank is a cylindrically-shaped prestressed concrete pressure tank 3 which includes a high temperature nuclear reactor 4 as well as all of the main cycle components of the plant associated with the reactor. In FIG. 1 only the turboset is shown, the heat transfer components and interconnecting conduit system are not illustrated so that a clearer picture of the reactor and the turboset can be obtained. All of the active gas-carrying auxiliary devices as well as the equipment necessary for the disassembly of the main cycle components are located within the safety tank. Of such disassembly equipment, only the revolving crane 5 which serves as the main hoisting member is shown in the drawing. The crane 5 is movably supported in a horizontal plane immediately below the plane at which the dome-shaped top is located. The working radius of the crane is such that it can be used for the disassembly of all the components located within the safety tank 1. The high-temperature reactor 4 is a graphite-moderated, helium-cooled, pebble bed reactor having a cone 6 located at the bottom of the reactor core with a delivery pipe 7 extending downwardly from the lower end of the cone and a suspended ceiling reflector 8 located above the core. A hot gas collecting chamber 9 is located within the reactor below the core for receiving the hot gases after they pass through the pebble bed of the core and before they are circulated on to the turboset and the other components in the closed cycle provided by the plant. The reactor 4 extends vertically and centrally within the pressure tank 3 and a horizontally arranged tunnel is spaced a sufficient distance below the reactor to ensure safe shielding from reactor radiation. A gas turboset is located within the tunnel and includes a single-shaft gas turbine 10 and a compressor consisting of a high-pressure stage 11 and a low-pressure stage 12, secured to the turbine by a common shaft 13. Aligned laterally outwardly from the turbine 10 and the compressor stages 11, 12 and exteriorly of the pressure tank 3, is a generator 14 positioned within a horizontally arranged cylindrical recess 14a extending outwardly from the outer surface of the safety tank 1. The generator 14 is rigidly coupled with the gas turbine 10. The cylindrical recess 14a is provided with a cover 14b so that access to the generator is available for disassembly, note FIG. 1. The installation of the turbine is effected by the so-called plug-in design. Two vertically extending hot gas lines 23, note FIGS. 2-6, each containing a gas fitting 24, extend between the hot gas collecting chamber 9 of the reactor, as shown in FIG. 1, and the four turbine inlets 25. As can be seen in the four sectional views provided in FIGS. 4-7, symmetrically disposed in an annular arrangement around the vertical axis of the prestressed concrete tank are eight vertical shafts or pods 15-22 which traverse the tank for the full extent of its vertical height with the shafts being disposed radially outwardly from the reactor and radially inwardly from the outer surface of the pressure tank 3. In FIG. 3 the shafts 15-22 are shown in a developed view, that is, with the portion of the pressure tank encircling the reactor being cut and opened so that the shafts appear in a single vertical plane. However, as can be seen in the sectional views, the shafts are arranged in a ring or annular arrangement about the reactor. In each of six of these shafts 15-20, in the vertical range comparable to that of the nuclear reactor, a recuperator 26 is positioned an above each recuperator is a pre-cooler 27. The recuperators 26 are arranged in two groups, in one group are the recuperators positioned in the vertical shafts 15, 16 and 17 and in the other group are the recuperators in shafts 18, 19 and 20. The recuperators in the vertical shafts 15, 16 and 17 are interconnected at their lower ends by means of a ring segment conduit 28 while the recuperators in the shafts 18, 19 and 20 are interconnected by another ring segment conduit 29, note FIGS. 3 and 5. Each group of vertical shafts is connected to a turbine outlet 25A over a tie line 30, 31 so that the entire outlet flow of the coolant gas from the turbine 10 is divided into two equal partial flows passing from the turbine through the tie lines 30, 31 to, as shown in FIG. 4, the shafts 17, 18. The flow into the first shafts in each of the groups is conducted to the other two shafts over the ring segment conduits 28, 29. Correspondingly, the pre-coolers 27 connected to the respective recuperators 26 in each shaft are interconnected by ring segment conduits 32, 33, at their upper ends, note FIGS. 3 and 7. A common collecting main 34 located between the shafts 15, 20, note FIG. 7, is connected to each of the ring segment conduits 32, 33 and the main passes downwardly through the pressure tank to inlets 35, note FIG. 4, into the low-pressure stage 12 of the compressor. The nuclear power plant can be equipped with four intermediate coolers 36, note FIG. 8, to improve its efficiency. Preferably, the intermediate coolers are located below the recuperators 26 in the vertical shafts 16, 17, 18 and 19. As with the recuperators and the pre-coolers located within the vertical shafts, the intermediate coolers are combined into two separate groups each interconnected by a ring segment conduit 37, 38, note FIGS. 3 and 5, and each of the conduits being connected by a tie line 39, 40 to the outlet 35A from the low-pressure stage 12 of the compressor. The ring segment conduits 37, 38 are located at the lower ends of the intermediate coolers 36 and the gases flowing through such coolers are collected at the upper ends thereof in two ring segment conduits 41, 42, note FIG. 3 and FIG. 4 and then empty into tie lines 43, 44, respectively, note FIG. 5, which lead to the inlets 11A to the high-pressure stage 11 of the compressor. The compressed gases from the outlets 11B of the high-pressure stage are conducted to the two groups of recuperators 26 through two tie lines 45, 46 each of which contains a cold gas fitting 47, 48, note FIGS. 4, 5 and 6. Since the recuperators are divided into two groups, the flow of the compressed gases through the tie lines 45, 46 are each directed into a separate ring segment conduit 49, 50, respectively, and then pass into the nests of tubes in each of the three recuperators associated with each of the two groups of heat exchange equipment. In FIG. 8, the ring segment conduit 49 is shown supplying the compressed gases into the lower end of the recuperator 26. Further, as can be seen in FIG. 8, the gases flow upwardly through the tubes within the recuperators 26 and then downwardly through a centrally arranged tube within each recuperator and finally into one of the six radially extending lines 51, 56 which convey the preheated gas from the recuperators in each of the shafts back into the cold gas collecting chamber 57, note FIG. 1, of the high-temperature reactor 4. Before the preheated gas reenters the reactor core, it flows between the thermal shield and the reflector arrangement cooling these parts, not shown. After passing through the reflector, the gas flows downwardly through the core containing the pebble bed and removes the heat generated in the fission reaction. As viewed in FIG. 3, the two shafts 21 and 22 are displaced from the positions shown in FIGS. 4-7 for the purpose of showing the shafts 15-20 relative to the reactor 4. Each of the shafts 21, 22 contain a shut-down heat elimination system 58 in the same vertical range as the intermediate coolers 36 within the other shafts. The shut-down heat elimination system 58 is composed of a blower, recuperator and cooler. Since the heat elimination system is not the subject of the invention, its components are not represented in detail. The heat elimination system 58 takes gas from a hot gas line 59, note FIG. 3, cools it in the recuperator to about 450.degree. C, subsequently reduces its temperature within the cooler to about 50.degree. C and then effects a pressure increase through the blower while increasing the temperature of the gas to about 70.degree. C. The compressed gas then flows through a centrally arranged pipe to the recuperator where it is heated to 400.degree. C and is returned through pipe line 60 to the reactor core on the cold gas side, note the lines 59, 60 in FIG. 5. Since not all of the space within the vertical shafts 15-22 are required for the main coolant cycle components, auxiliary systems needed for the operation of the reactor can be positioned within the remaining free spaces in the shafts. Accordingly, a gas storage tank can be provided in each of the vertical shafts 17 and 18 which act as frequency regulating tanks to support frequency of the gas turbine. With this arrangement a certain amount of gas is circulated back and forth between the frequency regulating tanks, not shown, and the main coolant cycle. The pressure gradient between the two pressure levels of the main cycle is used for frequency regulating action. The main cycle also includes a closed cooling water cycle affording a recooling system for conducting the heat resulting from energy losses to dry cooling towers for dissipation into the atmosphere. The recooling system is divided into two units each handling 50% of the output. Accordingly, two identical cooling water cycles are provided each of which gives up its heat in one of the dry cooling towers. In FIG. 2, the closed cycle gas coolant flow through the nuclear power plant is shown in a schematic arrangement, using the same reference numerals as employed in FIGS. 1 and 3. In the main gas coolant cycle the pressure ranges between a top pressure of 64.3 bar and a bottom pressure of 19.9 bar and the temperature varies within a range of 850.degree. C to 30.degree. C. On the hot gas side of the cycle, the gas flows at 850.degree. C and 60 bar directly out of the hot gas collecting chamber 9 of the reactor passing through the lines 23 and fittings 24 into the four inlets 25 into the gas turbine 10. In the turbine 10, the working gas is expanded to 20.7 bar and at a temperature of 494.degree. C flows through the turbine outlets 25A being divided between the two tie lines 30, 31 which are connected respectively into the shafts 17, 18, with the other two shafts in each group being connected by the ring segment conduits 28, 29. Within each of the shafts in each group, the gas flows into the recuperators 26. The recuperators, as shown in FIG. 8, consist of a number of vertically extending tubes positioned within a shell. The gas flowing through the tie lines 30, 31 flows over the nest of tubes within the recuperators. As the gas flows over the tubes it is cooled by gas flowing on the high-pressure side of the recuperators 26, that is, within the tubes, to 162.5.degree. C and then is directed into the superposed pre-coolers 27, note FIG. 8 where the arrows indicate that the flow over the tubes is directed into the pre-cooler. In the pre-coolers 27, the gas is cooled down to the lowest cycle temperature of 30.degree. C and then is collected in the two ring segment conduits 32, 33 located at the upper ends of the pre-coolers with both of the ring segment conduits flowing the gas into the vertical collecting main 34 which conducts it downwardly through the pressure tank into the inlets 35 to the low-pressure stage 12 of the compressor. In FIG. 1, the main 34 is shown extending downwardly through the pressure tank to the point at which it is connected to one of the inlets 35 to the low pressure stage 12, note in FIG. 4 that there are two inlets 35. In the low-pressure stage 12 of the compressor, the gas coolant is raised to a pressure of 36.1 bar and at a temperature of 125.6.degree. C flows from the outlets 35A of the low-pressure stage into two tie lines 39, 40 which convey the gas into the lower ends of the intermediate coolers 36. In these coolers, the gas temperature is reduced to 30.degree. C and exits into the ring segment conduits 41, 42 for flow through the tie lines 43, 44 into the inlets 11A to the high-pressure stage 11 of the compressor at a pressure of 35.8 bar, note the tie lines 43, 44 as shown in FIGS. 4 and 5. Within the high-pressure stage 11, the gas is raised to the maximum cycle pressure of 64.3 bar and flows through the outlets 11B, note FIGS. 4 and 5, through the tie lines 45, 46 containing the cold gas fittings 47, 48 into the ring segment conduits 49, 50 located at the lower ends of the recuperations 26 within the shafts which distribute the gas at a temperature of 125.6.degree. C for flow through the tubes in the recuperators 26, note FIG. 8. With the heat supplied from the low-pressure side of the recuperators 26, that is, the flow over the outside of the tubes, the high-pressure gas is brought to a temperature of 455.2.degree. C as it flows through the recuperator. As indicated in FIG. 8, the high-pressure gas flows upwardly through the tubes and at the upper end is deflected within a plenum through 180.degree. and flows downwardly through the central pipe in the recuperator. From the lower end of each central pipe in the recuperators 26, the gas flows into the radially extending lines 51-56, note FIG. 6, for delivery into the gas collecting chamber 57 located above the high-temperature reactor 4. The particularly compact arrangement provided by the present invention can be appreciated most completely by considering the arrangement of the piping shown in FIGS. 4-7. While a specific embodiment of the invention has been shown and described in detail to illustrate the application of the inventive principles, it will be understood that the invention may be embodied otherwise without departing from such principles.