Patent Number: 039980570
Section: description

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 and 2 show a pressure-tight safety tank 1 of cylindrical shape made of reinforced concrete, closed at the top by a domed cap 2. Centrally inside the safety tank a likewise cylindrical structure of pre-stressed concrete 3 is placed which encloses a high-temperature reactor 4 together with the set of components that makes up the primary circuit described in detail below (the turbine assembly, heat exchangers, gas lines). Also placed inside the safety tank 1 are all auxiliary components that carry the active gas, and all other equipment needed for the operation of the primary components. Of these the drawings show only the revolving crane 5 serving as the main lifting device, located in a plane some distance below the lower edge of the domed cap 2. The work area of this crane is large enough to allow for the movement of all components installed in safety tank 1. The high-temperature reactor 4 is built into a cavity or vessel 6. It is a helium-cooled ball-pile reactor with graphite moderation, shown in the drawing as consisting of core 7, located at the bottom of the core, a connecting ball-release tube 8 and a suspended ceiling reflector 9. Underneath the floor of the reactor core is the collector chamber 10 which receives the hot gas released by the ball pile. The reactor 4 is connected with the primary circuit by six intake- and four vents (as described below.). Perpendicularly under the high-temperature reactor 4 and at a distance adequate to assure shielding, a horizontal chamber 11 is built inside the pre-stressed concrete housing 3. In the chamber have been placed a single-phase gas turbine 12 together with high and low-pressure compressors 13, 14, installed coaxially with the gas turbine 12 on a common axle 15. The turbine and the compressors are inserted in the assembly as one unit on a rail leading into the horizontal chamber 11, by the so-called "insertable construction" method. A removable generator 16, located in a cylindrical recess 17, is rigidly coupled to the gas turbine 12. This cylindrical recess 17 is closed gas- and pressure-tight by lid 63. Four radial connecting pipes 18 carry the gas from hot-gas collectors 10 to the vertical hot-gas lines 19, which, in turn, are connected by horizontal tubes 20 to the four symmetrical intake-valves 21 of turbine 12. The four radial connectors 18 by which helium, heated to 850.degree. C., is carried to turbine 12, extend together with graphite packings 22 of the reactor, to the vertical hot-gas pipes 19. This placement facilitates the installation and removal of the hot-gas pipes 19 which each are composed of four pieces. In a circle around reactor vessel 6, eight perpendicular shafts or pods 23, 24 . . . 30 are provided, spaced symmetrically to each other and at a suitable distance from the wall of the concrete housing 3, extending nearly the total height of the structure. These large pods are closed off by explosion-proof lids. These lids are shown in FIG. 3 both at the top and at the base of concrete housing 3. In six of these pods, namely in pods 23, 24 . . . 28, a recuperator 31 is placed, on a level with reactor 4, and a pre-cooler 32 is connected to each recuperator vertically beneath it. The remaining pods 29, 30 are used for holding the four intermediate coolers 33 installed therein one above the other in pairs. The six recuperators are designed as counter-flow elements with the tube bundles in a triangular arrangement that facilitates the replacement of individual defective cells. The pre-coolers 32 as well as the intermediate coolers 33 are arranged in a helical construction, thus permitting pressure tests to be taken on individual tubes or areas from outside of housing 3, also permitting these areas to be inactivated and by-passed. By the use of such well-known and proven elements of design, a high degree of reliability is attained in connection with the heat exchangers. The system for collecting and distributing low-pressure gases discharged by the turbine is located underneath turbine chamber 11. The exhaust gas, heated to 500.degree. C. first flows in a vertical duct 34 downward into distributor 35, then through two coaxial feeder ducts 36 and into distributors 37. Connected to each distributor are two coaxial feeder tubes 38 which serve to distribute the gas over the six pods 23, 24 . . . 28. The gas now flows through the interior pipe of the coaxial feeder ducts 36, 38. Inside the pods, the gas moves through the interior ducts 39 (FIG. 3) which are leading through the pre-coolers 32; it then enters the recuperators 31 through which it flows on the side of the jacket. The gas is thereby cooled to approximately 160.degree. C. Upon being reversed by 180.degree. in a collection chamber 40 located on top of recuperator 31, the gas is carried through an annular shaped aperture 41 between the recuperator and the wall of the pod, and reaches pre-coolers 32 through which it flows on the side of the jacket. The gas, now cooled down to approximately 30.degree. C. then enters the exterior passages of the coaxial ducts 38 and is then collected in collectors 42, 43, which are located coaxially with respect to distributors 35, 37, or in other words, with the exterior ducts now acting as collectors and the interior ducts as distributors for the gas. The entire system of tubes underneath turbine chamber 11 is designed in such a manner that the turbine exhaust duct at about 500.degree. C. is surrounded on all sides by cold gas, thereby preventing the build-up of temperature stresses in the concrete hull. The coaxial gas ducts as well as all other cavities in the concrete structure are moreover covered with gas-tight steel liners which are protected by heat insulation and cooled by water. The liners also are subjected to merely moderate temperature stresses, since streams of hot gas are always surrounded by streams of cooler gas. The pressure differential between gas streams flowing coaxially, in normal operation, and depending upon the load, amount to 0.7 - 4 bar. Tubing which is freely distributed inside the liners is therefore exposed to relatively low pressures, while the pressures of the exterior gas streams are absorbed by the cement liner. From collectors 42, 43 the cooled gas passes through two simple (not coaxial) horizontal passages 44 and into a vertical cylindrical duct 45, from which it proceeds to low-pressure compressor 14 where it is compressed to 36 bar. From low-pressure compressor 14 two coaxial ducts 46 lead to pods 29, 30 in which the four intermediate coolers 33 are installed. The helium flows to the two pods in the exterior tubes at approximately 125.degree. C. and is divided into two streams, one directed upward, the other downward. Both parts of the split stream then flow through an annular shaped aperture 47 located between the pod and the intermediate coolers 33, then through the intermediate coolers on the jacket side and then enter in region 48 into the inner duct of the coaxial tube 46 which is located between the stacked intermediate coolers. The gas, now cooled to about 30.degree. C. reaches high-pressure compressor 13. From high-pressure compressor 13 the gas, now compressed to 64 bar, enters into the hollow space 49 surrounding the turbine housing and the intake valves 21. The pressurized gas then flows through two simple vertical ducts 50 and four manifold gas pipes 51 which run partially coaxially to the hot-gas ducts 19, and then into the distributor heads 52 of recuperators 31. The four high-pressure tubes 19 connecting the reactor 4 with the turbine 12 are likewise surrounded by relatively cold pressurized gas (125.degree. C.) so that neither the liners nor the concrete are affected by high temperature. The helium gas flows from the distributor heads 52 through the bundled tubes of the recuperators 31 and is heated to about 450.degree. C. by the exhaust gas from the turbine flowing in opposite direction. It is then brought back to the collector heads 53 of the recuperators 31 located on top of distributor head 52. By way of six tubes 54 which partially pass through high-pressurized cold-gas ducts 50, 51 the pre-heated gas is finally returned to a collecting space 55 on the reactor 4. Before returning to the reactor core, the helium flows along the space between the thermal shield and the reactor wall, thereby cooling these areas (not shown). The gas is then deflected by ceiling reflector 9, it enters into the space 56 on top of the ball pile, and is returned to the ball pile. In four vertical shafts or pods 57 symmetrically distributed around the reactor pod 6 on the same circle as pods 23, 24 . . . 30 and at the same height as the recuperators 31, an auxilliary or back-up cooling system 58 of a known design is installed with a capacity of 4 .times. 50% and consisting of blowers, recuperators and coolers. Since this auxilliary system is not a part of the present invention, these components are not shown in detail. The system 58 receives hot gas through duct 59, cools it in the recuperator to about 450.degree. C. and subsequently in the cooler, to about 50.degree. C. It increases the pressure by means of the blower, and the temperature rises to about 70.degree. C. The condensed gas flows back into the recuperator through a centrally located pipe, it is re-heated to 400.degree. C. and is carried back onto the reactor 4 through duct 60 on the side of the cold gas. In order to be able to separate the reactor 4 from the primary circuit, shut-off valves 61 are installed in the input ducts 54 and the hot-gas ducts 19. For the purpose of repaid and maintenance operations these shut-off valves 61 are accessible through vertical shafts 62, while other valves are located in the shafts or pods for cold-gas lines 50, 51 and are accessible from the top. In the following paragraph the main or turbine circuit is once more summarized in brief. The work process of the primary circuit takes place within the range between a maximal pressure of 64.3 bar and a minimum pressure of 19.9 bar; the temperature ranges between an upper limit of 850.degree. C. and the lower limit of 30.degree. C. The gas, heated to 850.degree. C. under 60 bar pressure, flows by way of tubes 19 from the hot-gas accumulator 10 directly into the four intake valves 21 of turbine 12. In turbine 12 the working gas is expanded to 20.7 bar and it temperature reduced to about 500.degree. C. It enters into the recuperators 31 by way of coaxial tubes 38 and the central pipes 39, flowing through the recuperator 31 on the side of the jacket. On contact with the cold gas that flows along the high-pressure side of the recuperators 31 the gas is further cooled to about 160.degree. C. prior to entering pre-coolers 32. Here it is chilled to the lowest temperature in the process range of 30.degree. C. and collected in collectors 42, 43 prior to entering low-pressure compressor 14 by way of gas pipes 44 and duct 45. In the low-pressure compressor 14 the working gas is raised in ambient pressure to 64.3 bar and its temperature raised to 125.6.degree. C., and it is transported by way of coaxial tubes 46 into intermediate coolers 33. There the gas is recooled to 30.degree. C. after which it flows through the interior tube of coaxial tubing 46 and enters the high-pressure compressor 13 under a pressure of 35.8 bar. There the pressure is raised to the maximum of 64.3 bar and the gas is returned to the distributor head 52 by way of cold-gas lines 50, 51, and subsequently distributed over the tube bundles of recuperators 31 at a temperature of 125.6.degree. C. The high-pressure gas is then heated to 455.2.degree. C. by the heat supplied by the low-pressure surface of the recuperators and subsequently brought directly through tubes 54 to the cold-gas collection space 55 of the high temperature reactor 4.