Abstract:
An emission monitoring system for a venting system of a nuclear power plant is configured for low consumption of energy while having high reliability of measurement results. The emission monitoring system has a pressure relief line connected to a containment and contains a high-pressure section, a low-pressure section, and a sampling line, which, on the inlet side, opens into the low-pressure section of the pressure relief line and is guided from there to a functional path through which steam flows. An ejector containing a pump fluid connector, a suction connector and an outlet connector is provided. A pump fluid feed line has an inlet side opening into the high-pressure section of the pressure relief line and is guided from there to the ejector and connected to the pump fluid connector. A sample return line is guided from the functional path to the ejector and connected to the suction connector.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This is a continuation application, under 35 U.S.C. §120, of copending international application No. PCT/EP2014/055804, filed Mar. 24, 2014, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2013 207 595.2, filed Apr. 25, 2013; the prior applications are herewith incorporated by reference in their entirety. 
     
    
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
       [0002]    The invention relates to an emission monitoring system for a venting system of a nuclear power plant. 
         [0003]    In case of a severe accident of a nuclear power plant, in addition to the release of steam, the release of large quantities of hydrogen can occur, in particular due to the known zirconium-water reaction. Without effective countermeasures, explosive (also detonation-capable) mixtures, which endanger the containment in the event of an uncontrolled reaction, are not to be precluded. Furthermore, in particular in the case of relatively small inerted boiling water reactor containments (typical volumes 5,000-15,000 m 3 ), due to the release of the non-condensible hydrogen together with steam, a rapid pressure increase occurs, which can go beyond the design pressure and can go up to the failure pressure of the containment. 
         [0004]    To prevent overpressure failure of the containment, the plants have been equipped for some time with filtered pressure relief. In spite of the filtering, a release of radioactivity into the surroundings takes place to a certain extent during the pressure relief. This release is typically measured and recorded by an emission monitoring system. The ascertained data are used to inform the population and to derive accident measures. 
         [0005]    The presently installed emission monitoring systems require a quantitatively substantial energy supply for operation for heating the sampling lines to avoid condensation and accumulation of aerosols. Furthermore, energy is required for the sample transport to the filters and the operation of the analyzers. The power supply (approximately 4-8 kW) can presently only be ensured via the emergency power diesel network. A desirable supply solely via batteries is difficult to implement due to the required battery capacity. Specifically, it would require a high expenditure for batteries and space. Furthermore, the plants are to be qualified for earthquake loads, which is complex because of the diesel generator sets and the associated fuel tanks and installation rooms. For accident sequences with complete failure of the internal power plant power supply (SBO=station blackout), the presently installed systems for monitoring are not available or are only available in limited form. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention is based on the object of providing a remedy in this regard and specifying an emission monitoring system of the type mentioned at the outset, which, with a high level of reliability, availability, and quality of the measurement results, is configured for particularly low consumption of electrical energy. 
         [0007]    Using the system according to the invention, emission monitoring can also be carried out during SBO events. The claimed emission monitoring system advantageously uses the thermo-hydraulic energy content of the venting exhaust gas stream for the sample conveyance and intrinsic medium heating to prevent condensation in the sampling lines. The optimized energy supply concept enables battery buffering from the failure of the normal operational power supply until the passive energy supply after the start of the containment venting process. 
         [0008]    The essential advantages from the viewpoint of the user or operator are summarized hereafter: 
         [0009]    a) autonomous processing of measurement and monitoring tasks with regard to gaseous emissions (exhaust gas monitoring) even in the case of SBO; 
         [0010]    b) items of information on the activity release are also available during SBO; 
         [0011]    c) information for deriving severe accident measures is provided; 
         [0012]    d) low energy consumption for the operation of the online monitors (iodine, aerosols, noble gases); 
         [0013]    e) energy supply by battery stores possible; 
         [0014]    f) low battery capacity required; 
         [0015]    g) small space requirement for the energy supply of the system; 
         [0016]    h) the emission monitoring system collects a representative sample, which is proportional to the flow rate of the venting system; 
         [0017]    i) regulation of the sample stream can be omitted; and actively turning on the sampling can be omitted, since the sampling is performed in a passively self-regulating manner by the venting stream. 
         [0018]    Other features which are considered as characteristic for the invention are set forth in the appended claims. 
         [0019]    Although the invention is illustrated and described herein as embodied in an emission monitoring system for a venting system of a nuclear power plant, 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. 
         [0020]    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. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
         [0021]      FIG. 1  is a schematic circuit diagram of an emission monitoring system for a venting system of a nuclear power plant in a first variant according to the invention; and 
           [0022]      FIG. 2  is a schematic circuit diagram of an emission monitoring system for a venting system of a nuclear power plant in a second variant. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0023]    Identical or identically acting parts are provided with the same reference signs in both figures. 
         [0024]    Referring now to the figures of the drawings in detail and first, particularly to  FIG. 1  thereof, there is shown an emission monitoring system  2 , which is used for measuring and monitoring the predominantly gaseous emissions, which are released into the surroundings during the so-called venting of a nuclear power plant  4 , in particular with regard to the radiological activity thereof. 
         [0025]    Venting refers in this context to the controlled pressure reduction within the safety container  6 , which is also referred to as a containment, and is only illustrated schematically and partially here, of the nuclear power plant  4  in the event of severe accidents having massive steam and gas release within the safety container  6 , with correspondingly high overpressure in relation to the external surrounding atmosphere. For this purpose, a pressure relief line  8 , which is also referred to as a vent line, is led out of the safety container  6 , this line being closed in normal operation of the nuclear power plant  4  by a shutoff valve  10 . To initiate the pressure relief, the shutoff valve  10  is opened, so that a predominantly gaseous pressure relief stream forms along the flow direction  12 , which is released via a chimney  14  or the like into the surroundings. An overpressure in the containment is thus reduced to subcritical values. 
         [0026]    To keep contamination of the surroundings as low as possible during the venting, various filter and/or washer units, in particular dry filters, wet washers, and/or sorbent filters, are in particular connected into the pressure relief line  8  upstream, optionally also downstream, of the section of the pressure relief line  8  which is picked out here in enlarged form, for the pressure relief stream, which is also referred to as a vent stream. This is referred to as filtered containment venting. Such units (not shown) are configured to substantially retain radioactive activities contained in the vent stream, in particular in the form of noble gases, iodine and iodine compounds, and aerosols. The entirety of all components provided for the venting operation is also referred to as a venting system  16 . 
         [0027]    Nonetheless, it cannot be entirely precluded that in specific severe accident scenarios, noteworthy quantities of activity will escape together with the vent stream into the surroundings, in particular in the case of old plants having inadequate retention units. In this case, at least temporary contamination of the power plant terrain threatens, which is to be taken into consideration during the planning and coordination of rescue measures. The emission monitoring system  2  is provided for this purpose, which collects a gas sample from the vent stream and supplies it to a number of analyzers  18 . The analyzers  18 , which preferably operate in through flow operation, perform, preferably in real time (“online monitoring”) or in any case promptly, a measurement of the present content of noble gases, iodine and iodine compounds, and aerosols in the gas sample and/or ascertain the radiological activity to be attributed to these components. Furthermore, for example, gas analyzers can be integrated into an analysis section  20  for determining the hydrogen concentration. 
         [0028]    Specifically, a sample taking line or in short a sampling line  22  is led for this purpose out of the pressure relief line  8 , which guides the vent stream, and is attached or connected to the analysis section  20 , which is arranged outside the pressure relief line  8 . On an intake side, the sampling line  22  is provided with a sampling nozzle  24  or probe, which is situated inside the pressure relief line  8  and has an intake opening  26  protruding into the vent stream. Alternatively, a simple line branch from the pressure relief line  8  also comes into consideration. In this manner, a part of the vent stream is thus supplied as a sample stream in the flow direction  27  through the sampling line  22  to the analysis section  20 . 
         [0029]    The analysis section  20  is equipped in the exemplary embodiment here with a plurality of the above-mentioned, real-time capable analyzers  18 , specifically an aerosol analyzer  28 , an iodine or iodine compound analyzer  30 , a noble gas analyzer  32 , and a hydrogen analyzer  34 , which all operate according to the through-flow principle and are connected in series with respect to flow. It is obvious that other and/or additional analyzers  18  can be provided, and that as an alternative to the series circuit, a parallel circuit of analyzers  18  or a combination of both line topologies can be implemented. Corresponding line branches and mergers can optionally be provided for this purpose. 
         [0030]    Additionally/alternatively, such analyzers can be attached directly on/in the pressure relief line  8  for online monitoring, in particular with respect to iodine and aerosol components of the vent stream. For this purpose, for example, an expansion part having reduced wall thickness (approximately 3 mm) is located in the pressure relief line  8 , preferably in the low-pressure portion  76  thereof (see below), to increase the sensitivity of the aerosol/iodine monitor  112 , which is attached on the outer side, by way of the reduced shielding. 
         [0031]    In the exemplary embodiment here, the analyzers  18  transmit the recorded measurement data via associated signal lines  36  to a shared control and pre-analysis unit  38 , which can be installed, for example, in an emergency control room of the nuclear power plant  4 . Alternatively, a plurality of decentralized analysis units can be installed. Under certain circumstances, the function of this unit can be restricted to data collection and optionally data processing, so that the actual analysis takes place in a downstream unit (not shown here). In addition, a remote transfer of raw and/or processed measurement data by telemetry or the like to an external observation station can be provided. 
         [0032]    The power supply of the control and analysis unit  38  and—if necessary—the individual analyzers  18  is performed, with intact intrinsic power supply of the nuclear power plant  4 , via a conventional plant power network  40  and, in the event of its failure, via an autonomous emergency power network  42 , which is preferably activated according to the principle of an uninterruptible power supply (UPS) if needed. The emergency power network is preferably supplied by rechargeable batteries/accumulators  44 , which can be recharged via the plant power network  40  if it is intact, but can also have a fuel cell unit and/or a diesel generator set. 
         [0033]    In the exemplary embodiment according to  FIG. 1 , a filter section  46  having a number of filters/collectors  48  is connected to the sampling line  22  in a parallel circuit with respect to flow to the analysis section  20 . For example, it is equipped with an aerosol filter  50  and an iodine filter/iodine compound filter  52 . A partial stream of the sample stream collected via the sampling line  22  thus flows through the filter section  46 . Online measurement is not provided for the filters/collectors  48  of the filter section  46 ; rather, they can be removed during the venting operation or at least after the abatement of the accident and studied with respect to the retained activity carriers. Even in the event of total failure of the online analyzers  18 , a subsequently analyzable, summary documentation of the emissions released by the venting is still enabled. 
         [0034]    Additionally or alternatively to the mentioned filters, for example, filters/collectors for H-3 (tritium) and C-14 (carbon) can be connected into the filter section  46 . 
         [0035]    Furthermore, a bypass section  54  is provided in a parallel circuit with respect to flow to the analysis section  20  and to the filter section  46 . On the outlet side, all three partial lines discharge into a shared collection line or sample return line  56 , in which a suction pump  58  or vacuum pump, which is to be described in greater detail hereafter, is connected further downstream. Alternatively to the nomenclature selected here, the entire line network of the sampling and analysis system between the sampling nozzle  24  and the suction pump  58  could be referred to in simplified form as the sampling line. This alternative nomenclature is used hereafter in conjunction with  FIG. 2 , inter alia, because fewer partial lines or line sections are to be differentiated with respect to terms therein. 
         [0036]    To set or control or regulate the various partial streams, a plurality of shutoff and regulating valves are preferably provided in the line network of the sampling system. On the one hand, a settable shutoff valve  60  is provided upstream of the branches in the bypass section  54 , the filter section  46 , and the analysis section  20 , using which the flow rate through the sampling line  22 , that is to say the sample stream, can be set as a whole. On the other hand, the lines branching off from the sampling line  22 , which form the mentioned functional sections  20 ,  46 ,  54 , are themselves equipped with regulating valves  62  for setting the respective partial streams. These regulating valves  62  are arranged here in the exemplary embodiment downstream of the functional units, that is to say downstream of the filters/collectors  48  and the analyzers  18 . Additionally or alternatively, such regulating and/or shutoff valves can be arranged upstream of the functional units, so that one or more partial lines can optionally be decoupled with respect to flow from the sampling line  22  in running operation, for example, for maintenance and replacement work and for inspection of the filters/collectors  48 . In a particularly simple embodiment of the system, however, regulating and/or shutoff valves can also be substantially or even completely dispensed with, whereby the susceptibility to error and the control expenditure are reduced. In particular, active switching on of the sampling can be omitted if the shutoff valve  60  is dispensed with, since the sampling is then performed passively in a self-regulating manner by the venting stream and is therefore automatically activated. 
         [0037]    Furthermore, the shutoff valve  60  in the sampling line  22 , as indicated in  FIG. 1 , can be configured as a three-way valve having an additional line connection, namely for an inert gas line  64  or a flushing gas line. For example, an inert gas or flushing gas, in particular nitrogen N 2 , can therefore be introduced as needed from a pressurized storage container  66 , such as a pressurized gas bottle, into the sampling line  22  and admixed to the sample stream. With correspondingly selected valve setting of the three-way valve  60 , the inert gas or flushing gas can also exclusively be conducted through the following section of the sampling line  22 . In a similar manner, the individual partial lines of the functional sections can have line fittings  67  for inert gases, flushing gases, or also reagents for chemical conditioning of the respective partial stream, which are to be supplied as needed. Control or regulation of the significant valves is preferably performed via the central control unit  18 , and alternatively manually. 
         [0038]    For the most reliable possible measurement of the activities and gas compositions of interest, condensation of vaporized fractions in the sample stream and accumulation of aerosols on the path to the filters/collectors  48  of the filter section  46  and the analyzers  18  of the analysis section  20  are to be avoided as completely as possible. 
         [0039]    For this purpose, in standby operation of the emission monitoring system  2 , i.e., in normal operation of the nuclear power plant  4 , preheating of the sampling line  22  and the partial lines leading to the filters  48  and analyzers  18  is provided at least on selected line sections and optionally on the filters  48  and analyzers  18  themselves. This standby heating is implemented in the emission monitoring system  2  according to  FIG. 1  by an electric pipe trace heater, to which operating current is normally applied by the conventional plant power network  40  of the nuclear power plant  4 . The associated heating coils/heating elements  68 , which are laid around the pipe lines or are integrated in the pipe walls, are only indicated as examples at several points of the line network in  FIG. 1 . The heating power of the entire heating system is configured for a temperature to be ensured of the sample stream above the dewpoint temperature to be expected during measurement operation (approximately &gt;150-200° C.). 
         [0040]    In the case of a so-called station blackout situation with failure of the conventional plant power network  40 , which typically exists in particular during the activation or during operation of the emission monitoring system  2 , the above-mentioned emergency power network  42 , based on a battery unit, a fuel cell unit, or a diesel generator set, at least initially takes over the power supply of the electrical pipe heating and therefore the compensation of the unavoidable heat losses during the sample transport. 
         [0041]    To keep the heat losses as low as possible (approximately &lt;500 W), the sampling line  22 , the partial lines branching off therefrom to the functional units (filters/collectors  48  and analyzers  18 ), and the functional units themselves are provided as completely as possible, but at least in some relevant portions and regions, with thermal insulation, in particular in the form of an insulation jacket  70 , which is only schematically indicated at several points in  FIG. 1 . In addition, materials having poor heat conductivity are preferably used in the region of the pipe walls or housing walls. 
         [0042]    To avoid aerosol accumulation on the walls of the flow path, the sampling line  22  and the partial lines branching off therefrom to the functional units are preferably embodied having internal Teflon coating or aluminum coating or in hydraulically smooth, electropolished stainless steel. 
         [0043]    To keep the capacity requirements for the emergency power supply  42  or the energy stores thereof as low as possible and nonetheless to ensure reliable sample transport to the functional modules while preventing vapor condensation, an array of measures is provided, which bring about the design of the emission monitoring system  2  according to  FIG. 1  to form a substantially passive or semi-passive system (of course, the analysis and control unit  38  and the analyzers  18  generally require a certain quantity of electrical current, so that complete passivity in the sense of complete decoupling from the emergency power network  42  is only implementable with difficulty in this variant). These measures will now be described in detail. 
         [0044]    On the one hand, a throttle portion, in the form of a throttle orifice  72  here, is arranged in the pressure relief line  8  which guides the vent stream. Upstream of the throttle orifice  72 , the gas pressure approximately corresponds to the containment internal pressure of the atomic plant  4 , typically of 3 to 6 bar absolute at the beginning of the venting, possibly reduced by a pressure drop of up to 1 or 2 bar, in the line sections connected upstream with respect to flow, including filter and/or washer units. A pressure reduction to approximately the ambient pressure of approximately 1 bar absolute is performed by the throttle orifice  72 . Therefore, a high-pressure portion  74  of the pressure relief line  8  upstream of the throttle orifice  72  and a low-pressure portion  76  downstream of the throttle orifice  72  can be referred to. 
         [0045]    Passive drying and overheating of the vent stream take place due to the throttling, so that, in sampling operation with open shutoff valve  60  in the sampling line  22 , through the sampling nozzle  24 , which is preferably arranged downstream of the throttle orifice  72 , an overheated sample is introduced into the sampling line  22 , the vapor fraction of which already has a sufficient dewpoint distance (with relative humidity &lt;1). 
         [0046]    In addition, by way of a suction pump  58 , which is connected in the collection line  56  leading away from the filters  48  and the analyzers  18 , a partial vacuum, which drives or assists the sample transport, is generated in the upstream portions of the line system provided for the sampling and analysis. By way of the partial vacuum, the vapor fraction in the sample stream is led further by isenthalpic relaxation into the overheating region of the phase diagram, which describes the thermodynamics. The dewpoint temperature is reduced in this way below the prevailing saturation vapor temperature before the throttle orifice  72 . The electrical heating can be completely deactivated and removed from the energy balance due to the sampling line  22 , including filter section  46  and analysis section  20 , which is heated using the isenthalpic relaxed intrinsic medium. Sampling and heating now take place—in any case after a brief initial startup phase, in which the electrical heating can also be switched on as a supplement under certain circumstances—completely passively over the entire venting procedure. 
         [0047]    The suction pump  58  can in principle be an electrically driven pump, which is supplied with operating power via the plant power network  40  or the emergency power network  42  of the nuclear power plant  4 . However, it is particularly advantageous in the meaning of the desired passive system design if it is driven by the existing flow energy of the vent stream in the pressure relief line  8 , as exists in particular in the high-pressure portion thereof. 
         [0048]    For this purpose, the suction pump  58  of the emission monitoring system  2  according to  FIG. 1  is embodied as a jet pump  78 , sometimes also referred to as an ejector. A partial stream of the vent stream from the high-pressure portion  74 —i.e., the portion upstream of the throttle orifice  72 —of the pressure relief line  8  of the nuclear power plant  4  is collected as the propellant. That is to say, a pressure resistant propellant supply line  80  is led from the high-pressure portion  74  of the pressure relief line  8  to the propellant fitting  82  of the jet pump  78 , through which flow occurs in the flow direction  83 . The intake opening  84  of the propellant supply line  80  can be formed, as indicated in  FIG. 1 , as a simple branch from the pressure relief line  8  or, as in the preferred embodiment of the sampling line  22 , as a sampling nozzle protruding into the flow channel. 
         [0049]    The collection line or sample return line  56  for the sample stream on the outlet side of the filter section  46 , the analysis section  20 , and optionally the bypass section  54  of the sampling line system is connected to the suction fitting  86  or suction connecting piece of the jet pump  78 . An outlet line or return line  90  is connected to the outlet fitting  88  of the jet pump  78 , which is led back at the other end, the outlet end  91 , into the pressure relief line  8  in a preferred embodiment, specifically into the low-pressure portion  76  thereof, downstream of the throttle orifice  72 , in particular downstream of the sampling nozzle  24  of the sampling line  22 . 
         [0050]    The jet pump  78  can be embodied in conventional construction and, at the propellant intake, can have a propellant nozzle  92 , further downstream a mixing chamber  94 , in which the propellant jet meets the suction means sucked in from the circumferential region, and at the outlet side an optional diffuser  96  for partial pressure reclamation, as indicated in detail D of  FIG. 1 . Alternatively, a design like a simple Venturi nozzle  97  is also possible, at the constriction point or throat  98  of which the suction fitting  86  is formed as an opening in the pipe wall. Such a configuration is illustrated in detail E of  FIG. 2  (the optional envelope by a jacket pipe of the sampling line  22  additionally depicted therein will be described in greater detail hereafter). 
         [0051]    According to the known functional principle of the jet pump  78 , a partial vacuum for suctioning in the sample stream is generated in the nozzle section or throat  98  thereof by the conversion of pressure energy into flow velocity. The sucked-in sample stream is primarily entrained by momentum transfer from the propellant stream and mixes with it at the same time. The resulting mixture of propellant and suction means, which is at relatively low pressure—in both cases partial streams of the vent stream here—then leaves the jet pump  78  via the outlet fitting  88  thereof and the return line  90  connected thereto and is advantageously unified again, as already described above, with the remaining vent stream and released together with it into the surroundings. The sampling and the sample transport are therefore performed completely passively by the existing flow energy of the vent stream, wherein passive overheating of the sample stream is additionally ensured. 
         [0052]    The variant of the emission monitoring system  2  illustrated in  FIG. 2  differs as follows from the variant illustrated in  FIG. 1 . 
         [0053]    On the one hand, no aerosol/iodine monitoring performed online is provided here. The analysis section  20  is thus omitted. The bypass section  54  is also not provided. Only the filter section  46  having aerosol filters  50  and/or iodine filters  52  is implemented. Instead of an emission monitoring system  2 , an emission documentation system can also be referred to in this variant. Such alterations could also be implemented in the variant according to  FIG. 1 , of course. 
         [0054]    In addition, the entire sampling line  22  is now led from the sampling nozzle  24  via the aerosol filters  50  and/or iodine filters  52  up to the suction fitting  86  of the jet pump  78  in an enveloping jacket pipe  100 , so that a heating medium can flow through the intermediate space between the outer wall of the sampling pipe  102  and the inner wall of the jacket pipe  100 . The sampling pipe  102  is advantageously embodied in this embodiment using a material (for example, aluminum) having high thermal conductivity, while the jacket pipe  100  preferably has poor thermal conductivity and/or is provided with a thermal insulation jacket  104 , to promote the heat transfer from the heating medium to the sample stream, on the one hand, and to minimize the heat dissipation to the external surroundings, on the other hand. 
         [0055]    A partial stream of the vent stream from the vent line  8  is advantageously branched off as the heating medium. For this purpose, the jacket pipe  100  has, for example, as shown in detail F, a ring-shaped intake opening  106  for the comparatively hot vent gas in the region of the sampling nozzle  24  of the sampling line  22 . In this embodiment, therefore, the sampling nozzle  24  can already be heated. The vent gas, which acts as the heating medium, subsequently flows through the intermediate space between sampling pipe  102  and jacket pipe  100  in the same direction as the sample stream and thus causes the desired superheating of the sample in the sampling line  22  including the filter section contained therein having the filters/collectors  48 . Downstream of the filter section, the heating stream and the sample stream are advantageously brought together, for example, as shown in detail E through a slotted transfer  108  in the pipe wall of the sampling pipe  102 , and after/with mutual mixing are sucked in jointly at the suction fitting  86  of the jet pump  78 . To avoid undesired backflow into the sampling pipe  102 , a throttle orifice  109  can be arranged in the sampling pipe  102  upstream of the transfer  108 . 
         [0056]    In the described manner, in particular with still closed sampling line  22  in standby operation of the emission monitoring system  2 , preheating of the sampling line  22  can be performed by solely passive suctioning in of the hot vent gas stream via the jacket pipe  100 . This heating is also maintained later in the actual sampling operation with open sampling line  22 . Electrical preheating of the sampling line  22 , which is indicated in  FIG. 2  by optional heating elements  110 , can be completely omitted with suitable design and dimensioning of the flow and temperature conditions. 
         [0057]    Such a design of the pipe heating having jacket pipes  100 , through which vent gas flows, is also possible in principle in the more complex system variant according to  FIG. 1 , at least for individual partial lines. However, complete coverage of the heating demand in this manner is more difficult to achieve in particular in regard to the analysis section  20 . Because of the variety of pipe branches and mergers, the design effort would also be substantial therein, so that this design suggests itself more for systems which are kept simple, as in  FIG. 2 . 
         [0058]    As already mentioned, various combinations of the individual components and partial sections provided in  FIG. 1  and  FIG. 2  can be implemented. A focal point in online measured value acquisition is placed in particular on the emitted radioactive noble gases. The noble gas analyzer  32 , which is advantageously arranged in the analysis section  20 , has a robust gamma sensor for this purpose, for example. The measured values which are preferably continuously recorded and transmitted online by the noble gas analyzer  32  enable conclusions about the mass flows and concentration of the noble gases contained in the vent stream and of the corresponding nuclide-specific activity rates. The quantity of the radioactive aerosols and iodine components contained in the vent stream and the contribution thereof to the activity release can be ascertained therefrom in the sense of a modeled rough estimate or simulation quickly (ideally in quasi-real time), without having to carry out online monitoring for these components themselves. Sophisticated simulation programs and the like are available for this purpose, which take into consideration the respective reactor type. That is to say, the aerosol analyzers  28  operating online and the iodine analyzers  30  from  FIG. 1  can optionally be omitted, without having to thus accept substantial losses with respect to the analysis quality. 
         [0059]    Nonetheless, a representative sampling with respect to the aerosol and iodine components and also optionally H-3 and C-14 in the filters/collectors  48  of the filter section  46 , which are configured for correspondingly high temperatures and pressures of the sample stream and are therefore outstandingly robust, can be performed during the venting. After ending the venting process, an analysis of the collected activities can then be performed in a laboratory (in particular for documentation or preservation of evidence of the activity emissions). On the basis of this subsequent analysis, a correction of the measured values which were previously captured online and/or the nuclide-specific outflow and activity rates calculated on the basis of models can optionally be performed. The circumstance is thus also taken into consideration that the long-lived radioactive isotopes, for example, I-131 or Cs-137, which are particularly important for evaluating the environmental stress, can possibly only be directly captured metrologically during the venting with difficulty, because the short-lived noble gas decomposition products such as Rb-88 or Cs-137 dominate the vent stream with respect to radiation at this point in time. 
         [0060]    The following is a summary list of reference numerals and the corresponding structure used in the above description of the invention:
     2  emission monitoring system     4  nuclear power plant     6  safety container/containment     8  pressure relief line/vent line     10  shutoff valve     12  flow direction     14  chimney     16  venting system     18  analyzer     20  analysis section     22  sampling line     24  sampling nozzle     26  intake opening/intake mouth     27  flow direction     28  aerosol analyzer     30  iodine analyzer     32  noble gas analyzer     34  hydrogen analyzer     36  signal line     38  control and/or analysis unit     40  plant power network     42  emergency power network     44  battery/accumulator     46  filter section     48  filter/collector     50  aerosol filter     52  iodine filter     54  bypass section     56  collection line/sample return line     58  suction pump     60  shutoff valve/three-way valve     62  regulating valve     64  inert gas line/flushing gas line     66  storage container     67  line fitting     68  heating coil/heating element     70  insulation jacket     72  throttle orifice     74  high-pressure portion     76  low-pressure portion     78  jet pump     80  propellant supply line     82  propellant fitting     83  flow direction     84  intake opening     86  suction fitting     88  outlet fitting     90  return line     91  outlet end/outlet mouth     92  propellant nozzle     94  mixing chamber     96  diffuser     97  Venturi nozzle     98  throat     100  jacket pipe     102  sampling pipe     104  thermal insulation jacket     106  intake opening     108  transfer     109  throttle orifice     110  heating element     112  aerosol/iodine monitor   M online monitoring   N 2  nitrogen   D, E, F details