Patent Number: 046719253
Section: summary

The invention relates to a method for operating a nuclear reactor, with an exhaust gas source, particularly a coolant purifier, and an exhaust gas system connected thereto, including at least one compressor, a gas cooler, a reducing valve, a humidity adsorber, a delay line and a flue connection. German Patent DE-PS No. 23 02 905, corresponding to U.S. Pat. No. 3,964,965, describes a pressurized-water reactor which includes a coolant purification system with a degasification device. The gases separated from the cooling water are first freed of hydrogen by combustion. They are then transported to a drier, in which water is precipitated. The gases are then segregated in a gas segregation plant by fractional liquefication, so that the rare gases, especially krypton and Xenon, can be stored in a small storage tank, while the remaining gases are returned to the system, unless they are discharged through a flue connection. In other nuclear reactors, the gases are conducted through a delay line, so that their activity can decay. The delay line is either traversed in a cycle or it precedes the flue, as is explained in the book "VGB Kernkraftwerks-Seminar 1970" (VGB Nuclear Power Station Seminar 1970) on pages 43, 44 and 45. However, such procedures are quite expensive. It is accordingly an object of the invention to provide a method for operating a nuclear reactor, which overcomes the hereinaforementioned disadvantages of the heretofore-known methods of this general type, and to reduce the costs due to the exhaust gas treatment. With the foregoing and other objects in view there is provided, in accordance with the invention, a method for operating a nuclear reactor having reactor coolant including an exhaust gas source, particularly a coolant purifier, and an exhaust gas system connected to the exhaust gas source, the exhaust gas system having at least one compressor connected to the exhaust gas source, a gas cooler connected to the compressor, a first reducing valve connected to the gas cooler, a switching valve connected to the first reducing valve, a moisture adsorber connected to the switching valve, a delay line normally connected in parallel with the moisture adsorber, a gas loop connected between the moisture adsorber and the compressor, a flue connection set at a given pressure during normal operation, and a second reducing valve connected between the delay line and the flue connection, which comprises interconnecting the delay line and the moisture adsorber in series, setting the flue connection to a pressure at least twice as high as the given pressure, reversing the switching valve thus allowing the exhaust gas to pass from the moisture adsorber to the delay line and then to the flue connection through the second reducing valve, upon the occurence of a coolant displacement and increased exhaust gas production, especially when starting up and shutting down the reactor. The new method permits a considerable size reduction of the components required for the exhaust gas treatment and a simpler system construction without additional apparatus. The advantages of the retention behavior which are more advantageous with overpressure for short-time operation of high gas production are combined with the time-wise predominant operating phases with low gas production, in which the possibilities of decompression drying by reduction of the operating pressure are utilized for minimizing the cost of the drying devices customary heretofore. In accordance with another mode of the invention, there is provided a method which comprises thermally insulating and/or cooling or heating the gas chamber, the moisture adsorber and the gas section of the gas system therebetween. In accordance with a further mode of the invention, there is provided a method which comprises reducing pressure over a period of several hours after an increased production of exhaust gases. This has been found to be advantageous for the transition from one mode of operation (increased exhaust gas production) to the other (normal operation). In accordance with a concomitant mode of the invention, there is provided a method which comprises switching over the moisture adsorber into the gas loop leading to the compressor after reaching a given low operating pressure. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a method for operating a nuclear reactor, it is nevertheless not intended to be limited to the details shown, since various modifications may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.