Patent Number: 054024544
Section: summary

CROSS-REFERENCE TO RELATED APPLICATION This application is a Continuation of International Application Ser. No. PCT/DE92/00679, filed Aug. 13, 1992. BACKGROUND OF THE INVENTION FIELD OF THE INVENTION The invention relates to a process and a device for obtaining a sample from the atmosphere in a closed gastight vessel, preferably from the reactor safety vessel of a nuclear power station, wherein the sample is introduced into a sample-taking container and constituents of the sample which are soluble and/or condensable in a transport or vehicle fluid are discharged from the vessel together with the transport fluid and gaseous constituents of the sample. Such a process and a device suitable for carrying out the process are known from German Published, Non-Prosecuted Application DE 39 32 712 A1, corresponding to Published European Application No. 0 419 994 A1 and to U.S. application Ser. No. 07/590,151, filed Sep. 28, 1990, now abandoned. Gastight vessels are frequently used for enclosing installations in which substances that must not pass into the environment of the vessel are reacted. Such vessels, which are also known as containments, are normally accessible while the installation enclosed in them is working correctly, and at the same time they also permit problem-free monitoring of the atmosphere contained in them. However, in the event of faults, the vessels are hermetically sealed in accordance with regulations, so that difficulties are encountered in obtaining samples from the outside which are representative of the atmosphere. When taking samples, the different states of the atmosphere, such as "dry" and "moist", as well as the behavior of the substances in gas or vapor form and of air-borne solid and liquid aerosols are of considerable importance. In particular, effects such as depositions of condensing vapors or large aerosols (&gt;1 .mu.m) upstream (in the direction of flow) of a sample taking device may result in a highly erroneous assessment of the composition and of a radioactive contamination of the atmosphere. In the device referred to above, sample taking fittings which are connected serially are provided in the run of a pipe loop, with each of them being able to be operated by means of a pneumatic or hydraulic line. Two penetrations of the wall of the vessel are then needed for the pipe loop in addition to one such penetration for each pneumatic or hydraulic line. Since the strength and tightness of the vessel must not be impaired thereby, it entails an expense which is not inconsiderable. Furthermore, the mechanically active sample taking fittings must also remain capable of operating under and after accident conditions, such as with temperatures above 500.degree. C. and extreme radiation loads of over 10 KGy/h, so that stringent demands on materials, particularly for moving parts, have to be met. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a process and a device for obtaining samples from the atmosphere in a closed gastight vessel, preferably from the reactor safety vessel of a nuclear power station, which overcome the hereinafore-mentioned disadvantages of the heretofore-known methods and devices of this general type and which obtain representative samples of the atmosphere prevailing in the vessel from the outside, without impairing the strength and tightness of the latter, while depositions of constituents of the samples, which would falsify the results of the measurement, are reliably avoided and the taking of samples is effected with components which can also be constructed for faulty conditions and which are preferably mechanically passive. With the foregoing and other objects in view there is provided, in accordance with the invention, a process for obtaining a sample from an atmosphere in a closed gastight vessel, preferably from a reactor safety vessel of a nuclear power station,which comprises passing a sample through a venturi nozzle immediately upon entry of the sample into a sample-taking container in a vessel; mixing the sample in the venturi nozzle with a transport fluid serving as a washing liquid; and subsequently discharging gaseous constituents of the sample being soluble and/or condensable in the washing liquid together with the washing liquid from the sample-taking container and from the vessel by triggering by a sudden pressure reduction. In accordance with another mode of the invention, an inlet channel, through which the sample flows before reaching the venturi nozzle, is flushed with the washing liquid contained in the sample-taking container, before the sample is discharged. In accordance with a further mode of the invention, the velocity of flow of the sample in the venturi nozzle or nozzles is slightly, preferably 10% to 30%, below the critical nozzle velocity, so long as no condensation of the sample occurs in the washing liquid, and the velocity of flow is increased to the critical nozzle velocity as soon as the sample condenses, at least partially, in the washing liquid. In accordance with an added mode of the invention, there is provided a process which comprises reacting gaseous constituents of the sample and of the transport fluid chemically with one another. In accordance with an additional mode of the invention, there is provided a process which comprises varying a level height of the washing liquid, preferably in the inlet channel, by pressure changes in the transport fluid, and raising the washing liquid at least once after the sample has flowed in to a height of an inlet opening at a free end of the inlet channel for the sample. In accordance with yet another mode of the invention, there is provided a process which comprises adjusting a difference in pressure between an atmosphere in the vessel and an interior of the sample-taking container to up to 5000 hPa. In accordance with yet a further mode of the invention, there is provided a process which comprises adjusting a temperature of the washing liquid at the beginning of a sample taking process to be slightly lower than that of an atmosphere in the vessel. In accordance with yet an added mode of the invention, there is provided a process which comprises retaining elementary organic iodine, CO, CO.sub.2 and other gas from the sample in the washing liquid, by inactive iodine additions and variation of the pH value of the washing liquid. In accordance with yet an additional mode of the invention, there is provided a process which comprises diluting the washing liquid after being drawn off by suction from the sample-taking container, until the radioactivity of the sample is lower than 10.sup.9 Bq/m.sup.2. In accordance with again another mode of the invention, there is provided a process which comprises separating the sample before its assessment into gaseous constituents and washing liquid containing other parts of the sample, and drawing off the sample by suction through a throttle working in the laval velocity range, through a water separator and into a vacuum vessel. In accordance with again a further mode of the invention, there is provided a process which comprises distributing each individual sample over a plurality of transport containers for transport purposes. In accordance with again an added mode of the invention, there is provided a process which comprises subjecting the sample-taking container to superatmospheric pressure, such as by introducing nitrogen, until a bursting disk at a free end of the inlet channel breaks, to initiate obtaining a sample. With the objects of the invention in view, there is also provided a device for obtaining samples from an atmosphere in a closed gastight vessel, preferably from a reactor safety vessel of a nuclear power station, comprising a sample-taking container having a bottom and a given volume; a washing liquid being disposed in the sample-taking container and having a volume being at most approximately equal to half of the given volume; a venturi nozzle dipping into the washing liquid in the sample-taking container above the bottom; and an inlet channel leading into the sample-taking container below the venturi nozzle. In accordance with another feature of the invention, the volume of the washing liquid is slightly greater than the volume of an inlet channel, serving for the admission of the samples, between the free end of the channel and the bottom of the sample-taking container. In accordance with a further feature of the invention, the venturi nozzle is replaced by filling bodies, which serve as flow distributors, and a plurality of nozzles in the bottom of the sample-taking container, with an inlet opening of the inlet channel at the free end of the latter being closed by a bursting disk during the normal use of the vessel. In accordance with an added feature of the invention, the sample-taking container has a dome, and there is provided a filling and emptying line at the bottom for the washing liquid, and a gas line connected to the dome. In accordance with an additional feature of the invention, the sample-taking container has a side, the filling and emptying line is guided upwards at the side, and there is provided an injector connecting the filling and emptying line to the gas line laterally above the dome. In accordance with yet another feature of the invention, the sample-taking container is disposed inside the vessel, preferably inside a reactor safety vessel. In accordance with yet a further feature of the invention, there is provided a line starting from the injector and passing to the outside through an outer wall of the vessel, and a throttle in the line for limiting a flow through the line. In accordance with yet an added feature of the invention, there is provided a sorption filter for organoiodine being inserted into the line. In accordance with yet an additional feature of the invention, there are provided polished or teflon-coated surfaces, preferably in the inlet channel, being in contact with the sample. In accordance with again another feature of the invention, the sample-taking container has built-in fittings, and the inlet channel, the sample-taking container with all of the built-in fittings, the filling and emptying line, the gas line, the injector and the line starting from the injector are formed essentially of radiation-resistant material, such as special steel. In accordance with again a further feature of the invention, volume of the washing liquid filling the sample-taking container is substantially between 2 and 3 liters. In accordance with a concomitant feature of the invention, there are provided means for maintaining a constant velocity of flow of the sample by throttling in the venturi nozzle and/or with a throttle disposed outside the vessel. The process according to the invention and the device according to the invention are very advantageous because they make it possible to obtain unadulterated samples of the atmosphere in a hermetically sealed vessel and for this purpose require only a single bushing for a pipe through the wall of the vessel. Impairment of the strength and tightness of the vessel are thereby virtually impossible. This is still true if, in the event of the direct extraction of washing liquid, a second pipe is passed through the wall of the vessel. 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 process and a device for obtaining samples from the atmosphere in a closed gastight vessel, preferably from the reactor safety vessel of a nuclear power station, 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.