Patent Number: 060884177
Section: summary

BACKGROUND OF THE INVENTION Field of the Invention The invention relates to an apparatus for leak detection and leak location in a nuclear plant, in particular in a pipeline of a nuclear plant, having a collection line which is permeable to a substance to be detected and communicates with a pump and with a sensor for the substance, and in which the sensor is not suited to detecting the radioactivity of the substance. The invention also relates to a method for detecting and locating leaks in a nuclear plant, in particular in a pipeline of a nuclear plant, in which the concentration of a substance from the plant that has penetrated a collection line is measured. German Published, Non-Prosecuted Patent Application 24 31 907 corresponding to U.S. Pat. Ser. No. 3,977,233, discloses an apparatus for leakage detection and location (which is abbreviated as LEOS). That apparatus includes a collection line which is permeable to the substances to be detected. Communicating with the collection line is a pump, with which volumes of a transport medium, such as air, are pumped in succession through the collection line. Disposed at the end of the collection line is at least one sensor, which detects substances that have penetrated the collection line. A special construction of such a collection line is known from European Patent 0 175 219 B1. It has permeable points, which may be formed of sintered metal and are spaced apart from one another. The line is impermeable between those permeable points. U.S. Pat. No. 5,301,538 describes a further leak detecting and locating apparatus, which has at least two collection lines permeable to substances to be detected. The collection lines discharge into a common gas sensor, which in particular may be a sensor for radioactive radiation. In particular, there may be two gas sensors. A device for monitoring a line in which radioactive substances are carried, is known from Published Japanese Patent Application JP 59 166 986. That line is surrounded by a collection line of larger diameter, which communicates with a radioactivity detector. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide an apparatus and a method for leak detection and location, which overcome the hereinafore-mentioned disadvantages of the heretofore-known apparatuses and methods of this general type in such a way that a second, diverse evidence of leakage is possible. As a result, even more-reliable leakage detection and location are to be assured. With the foregoing and other objects in view there is provided, in accordance with the invention, an apparatus for detecting and locating leaks in a nuclear plant, in particular in a pipeline of a nuclear plant, comprising a collection line permeable to a substance to be detected; a pump communicating with the collection line; a sensor communicating with the collection line for sensing the substance, the sensor not suited to detecting radioactivity of the substance; and a detector communicating with the collection line for detecting radioactivity of the substance. This detector may be a gamma detector. In that case, not only the maximum concentration of a substance that has penetrated but also the maximum activity of the penetrating substance is determined and utilized for detecting and locating leaks. Thus two redundant apparatuses for leakage location are obtained. In accordance with another feature of the invention, there is provided a branch line which communicates with the detector and branches off upstream of the sensor. In accordance with a further feature of the invention, there is provided a suction pump associated with the detector. In accordance with an added feature of the invention, there is provided a supply container in which the detector is disposed. In accordance with an additional feature of the invention, there is provided a valve disposed upstream of the collection line. In accordance with yet another feature of the invention, the sensor determines a concentration of substances. In accordance with yet a further feature of the invention, there are provided openings which are located at intervals in the collection line and at which check valves are disposed. These check valves are constructed in such a way that they open if a predetermined pressure fails to be attained, but otherwise are closed. If the sensor line is closed at its entrance by a valve and a suction pump upstream of the radioactivity detector is turned on, these check valves open once the predetermined pressure fails to be attained. The location of the leak can be determined from the period of time that elapses between the opening of the check valves and the response of the detector for detecting the radioactivity, if the flow speed in the collection line is known. This advantageously provides two possibilities of leakage location, thereby assuring reliable results. With the objects of the invention in view there is also provided a method for detecting and locating leaks in a nuclear plant, in particular a pipeline of the nuclear plant, which comprises measuring concentration and radioactivity of a substance from a nuclear plant having penetrated a collection line. In accordance with another mode of the invention, if the flow speed in the collection line is known, the location of the leak is determined, for instance, from the period of time that has elapsed between a pressure surge in the collection line and a response of the detector for detecting radioactivity. In accordance with a concomitant mode of the invention, the pressure surge may in particular be brought about by the opening of at least one check valve. 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 an apparatus and a method for leak detection, 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. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.