Patent Number: 052727386
Section: claims

1. A device for monitoring an atmosphere within a containment shell of a nuclear reactor plant, comprising: sample removal means provided in the containment shell;  a measuring line connected to the sample removal means for leading a gas sample from the containment shell;  a measuring zone located in the measuring line and disposed outside of the containment shell through which the sample is led for measuring the activity of the gas sample;  a dilution plant located in the measuring line and disposed int he containment shell for reducing the activity concentration of the gas sample upstream of the measuring zone;  the dilution plant being adapted to be connected to a clean, pressure-controlled dilution gas source located outside the containment shell.  sampling means for drawing a sample of gas within the atmosphere in the containment;  a dilution plant connected to the sampling means for diluting the gas sample with clean dilution gas, the dilution plant being adapted for connection with a source of clean, pressurized dilution gas;  a measuring line connected to the dilution plant for removing the diluted gas sample from the containment; and,  a measuring zone connected to the measuring line outside of the containment for measuring the activity of the diluted gas sample.  sampling gases in a containment shell;  diluting the gas sample in a dilution plant with clean, pressurized dilution gas;  removing the diluted gas sample from the containment shell;  directing the diluted gas sample through a measuring zone; and,  measuring selected activity of the diluted gas sample. 2. The device as claimed in claim 1, wherein the dilution gas is heated by means of a heater before introduction into the dilution plant. 3. The device as claimed in claim 1, wherein the dilution plant is provided with a plurality of stages for dilution of the gas sample. 4. An apparatus for monitoring gases within a containment of a nuclear reactor plant, comprising: 5. The apparatus as claimed in claim 4, further comprising a heater to heat the dilution gas before introduction to the dilution plant. 6. The apparatus as claimed in claim 4 wherein the dilution plant comprises a plurality of dilution stages connected in series for diluting the sample gas in steps. 7. A method for monitoring gases within a containment shell of a nuclear reactor plant, comprising the steps of: 8. The method as claimed in claim 7, further comprising the step of heating the dilution gas before diluting the gas sample. 9. The method as claimed in claim 7, wherein the step of diluting the gas sample is performed is several stages.