Patent Number: 043740839
Section: summary

The invention relates to a nuclear reactor with a liquid coolant, especially water, in a cooling loop to which hydrogen is added, and having a volume control surge tank for the coolant and a high-pressure pump which feeds coolant taken from the cooling loop back into the cooling loop after purification. In the book "VGB-Kernkradtwerks-Seminar 1970", especially on page 41 thereof, a volume control system for a pressurized-water reactor is described that is used, among other things, for feeding-in chemicals. Part of this system, through which a portion of the reactor cooling water continuously flows, is also charged with hydrogen. This is to counteract the radiolytic decomposition of the coolant in the vicinity of the core. In the known system, the hydrogen is added into the volume control surge tank, which is part of the volume control system, and is therefore present above the liquid level as a gas cushion. The partial H.sub.2 pressure in the gas cushion is set in accordance with the desired hydrogen concentration in the cooling water. As the hereinafore-mentioned reference literature shows, the volume control system contains high-pressure pumps because the cooling system must be fed back into the primary loop of the pressurized-water reactor in which, as is well-known, pressures of, for instance, 160 bar prevail. It is accordingly an object of the invention to provide a nuclear reactor having a liquid coolant which overcomes the hereinafore-mentioned disadvantages of the heretofore known devices of this general type, and to modify the known volume control system with the objective of reducing the hydrogen components present in the volume control surge tank outside the volume of liquid, so that the danger of oxyhydrogen gas explosions if leaks occur is completely eliminated. With the foregoing and other objects in view, there is provided, in accordance with the invention, a nuclear reactor with a liquid (especially water) coolant loop having a volume control surge tank for the coolant disposed in the loop, and a high pressure pump disposed in the loop for feeding coolant taken from the loop back into the loop after purification, comprising a line bypassing the volume control surge tank and having an end connected to the suction side of the high-pressure pump, and means for introducing hydrogen into a liquid-filled section of the loop on the suction side of the high-pressure pump. With the use of the invention, the hydrogen to be added is directly fed into the liquid. Thus, it is no longer necessary to place very stringent requirements on the tightness of the volume control surge tank, since a flammable mixture can no longer be produced in the event of leaks. In accordance with another feature of the invention, the hydrogen introducing means feeds hydrogen gas to the bypass line. In accordance with a further feature of the invention, the hydrogen introducing means mixes hydrogen gas with coolant bled off from the volume control surge tank. In accordance with an additional feature of the invention, there are provided means for mixing hydrogen and coolant, disposed up-stream of the hydrogen introducing means, in flow direction of the coolant. The mixing means or section is a section of line with built-in components which causes deflection of the liquid flowing through it and thereby effects thorough mixing of added gas components. In accordance with an added feature of the invention, there is provided a gas separator disposed upstream of the mixing means, in the flow direction of the coolant. This prevents the occurrence of large gas bubbles due to excess hydrogen on the suction side of the high-pressure pump. In accordance with still another feature of the invention, there is provided a hydrogen delivery source connected to the hydrogen introducing means, and means connected to the gas separator and the hydrogen introducing means, for controlling the delivery rate from the hydrogen delivery source. The hydrogen source can be commercially available gas bottles with a suitable regulating device which is, for instance, a reducing valve. In accordance with still a further feature of the invention, there is provided a gas outlet line connected from the gas separator to the hydrogen introducing means, and a compressor preferably a diaphragm compressor, disposed in the gas outlet line. In this way, the hydrogen collected in the gas separator is again transported back into the liquid-filled line section with the feeding point or hydrogen introducing means. Further addition of hydrogen can then be dispensed with until the control device connected to the gas separator determines a demand for hydrogen to be added. It is assumed here that the gas which is separated in the gas separator behind the hydrogen feed-in point is substantially all hydrogen. The hydrogen content can be determined with measuring devices such as a process chromatograph. Other gas analyzers can also be used; the hydrogen content need not necessarily be determined continuously but can be performed at certain time intervals. In accordance with still an additional feature of the invention, the hydrogen introducing means includes a ceramic filter cartridge. Thereby, a fine distribution is achieved, which promotes the dissolution of the hydrogen in the coolant. In accordance with a concomitant feature of the invention, there is provided an exhaust gas system connected to the volume control surge tank above the coolant level. The gas space of the volume control surge tank, which in the invention is no longer required for hydrogen enrichment, should be connected to the exhaust gas system in such a manner that, contrary to known practice, the hydrogen content in the gas space remains reliably below 4%. Since the danger of oxyhydrogen gas explosions exists only above 4%, the connection to the exhaust gas system is used here to keep the amount of hydrogen small, while in the known system, a pure hydrogen cushion is present for the purpose of charging with gas. 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 nuclear reactor having a liquid coolant, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.