Patent Number: 045044392
Section: summary

BACKGROUND OF THE INVENTION 1. Field of the Invention The invention concerns a gas cooled nuclear reactor with several loops connected with the core by means of channels, with heat absorbing components such as heat exchangers, split tubular furnaces or the like being arranged in the loops with hot gas flowing through said components from bottom to top and their external surfaces being exposed to cold gas. 2. Background of the Prior Art In nuclear reactor installations, the thermal energy produced in the reactor core is transferred by means of a cooling gas medium to heat absorbing components such as heat exchangers, split tubular furnaces, and the like, which may be arranged in circuits or loops. A circuit or loop consists of a shaft or pod in the form of a cylinder arranged vertically in the prestressed concrete pressure vessel connected with the core by means of one or several channels. The circuit or loop houses different reactor components such as the heat exchanger equipment and the like. The cooling medium for example (helium) flows through the core from top to bottom. The cooling medium is conducted through a hot gas channel to the heat absorbing components, wherein it discharges a substantial portion of its thermal energy. It is then passed to the blower and returned to the core, whereby the cooled gas usually flows along the outside of the heat absorbing components. The above-described gas circuit may be supplemented by means of further reactor components, for example, a gas turbine. A plurality of circuits or loops are utilized in the conventional high temperature, gas cooled nuclear reactor. An essential characteristic of a nuclear reactor installation is that it is designed for a predetermined operational state. Excessive temperatures over extended periods of time or extreme fluctuations around its mean value may result in damage to the reactor installation. Grave problems are associated with the failure of certain heat absorbing components (such as with split tubular furnaces), as access to them is not possible for operational reasons alone (operational at gas temperatures of around 900.degree. C.). SUMMARY OF THE INVENTION It is the object of the invention to vary the gas temperature in a circuit of a gas cooled nuclear reactor installation without affecting the temperature of the gas in the other circuits. In an extreme case, it should be possible to take the affected circuit or loop out of service. This object is attained according to the invention by arranging a means for mixing gases under the heat absorbing component in the hot gas channel. The mixing means is connected with a cold gas conduit. The invention essentially consists of a mixing means arranged under a heat absorbing component located in the circuit or loop of a gas cooled nuclear reactor. Cold gas is fed into the hot gas flowing into the loop. The mixing means comprises at least one valve and a plurality of tubes projecting into the hot gas channel. The valves have a regulatory function, whereby the temperature of the gas being conducted to the heat absorbing component may be continuously varied within a temperature range of approximately 200.degree. to 900.degree. C. The simplest embodiment of the mixing means would have the potential disadvantage that the gas would not be adequately intermixed. A substantial temperature gradient within the mixed gas would possibly be created. Such a temperature gradient could have a negative effect (deformation) on the heat absorbing component. An adequate mixing of the hot gas with the cold gas may be obtained by feeding the cold gas by means of distributor heads into the hot gas. The distributor head has a plurality of orifices. The principal axis of each orifice is arranged perpendicularly to the surface of the distributor head. The turbulent flow of the gas flowing through the loop is prevented by inserting an apertured plate at the point of diversion in the hot gas channel. The tubes are arranged in the partition between the hot gas channel and the cold gas channel and may be located according to the invention either above or under the apertured plate. One embodiment is applied advantageously in cooling systems, wherein a reduction of the temperature from approximately 900.degree. to approximately 200.degree. is required. The tubes thereby pass through the apertured plate. The distributor heads are arranged above the apertured plate. In a further possible embodiment the tubes and the distributor heads are arranged under the apertured plate. A very good intermixing of the cold gas with the hot gas may be obtained in keeping with the invention, by causing the gas emerging from the mixing device to flow in a direction opposite to the direction of flow of the hot gas. Gas mixed in this manner displays no appreciable temperature gradient. The cold gas flows according to the invention through valves controlled by means of a regulator through the tubes into the hot gas channel. During normal operation, the actual temperature coincides with the nominal temperature and the valves are closed. If it is necessary to reduce the temperature of the gas flowing into the loop, the valves are opened slowly, whereby the cold gas flows into the hot gas. The heat absorbing components are, in a known manner, equipped with thermocouples to measure the temperature of the gas. In case of a failure of a heat absorbing component, it is desirable to reduce its temperature. This may be effected by opening the valves completely. By reducing the temperature, progressive failures of the heat absorbing components may additionally be prevented. The advantages obtained by the invention consist in particular of being able to vary the temperature of the gas flowing through the loop within a wide range of temperatures without thereby affecting the other loops, and particularly, without affecting the components arranged therein.