Research On Continuous Online Monitor Of Radioactive Aerosol

In the production of various nuclear materials,the decommissioning of nuclear equipment and the storage of radioactive wastes,there might be the possibility that radioactive substances with long half-life period disperse in air,forming artificial radioactive aerosol.Radioactive aerosol is the main source for internal exposure of workers,seriously influencing the professional health and safety of related personnel.Currently,there are two major measurements for aerosol,namely,sampling experiment analysis,and continuous online monitor.In order to ensure the accuracy of measurement result,this paper systematically analyzes the various factors of detection limit of continuous online monitor,and designs continuous monitor with high sensitivity and fast response including vacuum measurement and conventional surveying based on the existing basis.And based on improving the plan,the research and production of continuous online monitor of radioactive aerosol is achieved through design,processing and debugging.It mainly includes(1)Atmospheric pressure measurement chamber was designed for the collection of aerosols.A vacuum measurement chamber was designed to reduce the accuracy of the measurement results of the effects of radon thorium and its daughters.The design of the independent two-channel measuring room ensures the fast response time of the system and overcomes the problem of high detection limit of traditional atmospheric pressure measurement.Which atmospheric pressure measurement chamber for the normal atmospheric pressure measurement,because there is no vacuum radon thorium and its body will interfere with the measurement of artificial radioactive tailing phenomenon,so the detection limit is high,but the atmospheric pressure chamber is not the edge of the measurement time is not present time The To ensure that the production of a major leak occurred the first time the alarm.Vacuum measurement chamber for the vacuum environment measurement,atmospheric pressure measurement chamber sampling time after the filter paper into the vacuum environment measurement,to ensure that the system detection limit.(2)for the measurement of filter paper characteristics and collection requirements of the filter paper paper design components.Through the stepper motor to drive the filter paper to take the paper,incremental photoelectric encoder count to calculate the amount of paper,the gearbox to provide preload to ensure that the filter paper preload.(3)In order to facilitate the installation of the instrument and the use of the compatibility of the occasion,the design of a wall chassis,the internal regional design includes the internal measurement of mechanical areas,hardware circuit area,vacuum pumps and other parts of the heat insulation area,the Chassis features a small size,light weight,good reliability,good ergonomic.(4)As the system involves a variety of circuit modules of its power supply complex,designed a multi-linear power supply,the power supply voltage from-15 V to +24 V various voltage,its full load ripple low,small crosstalk.(5)For the system of various process control and sensor signal design of the main control circuit.Including the pressure,pressure,incremental photoelectric encoder,mass flow meter and other signal acquisition circuit and the next machine signal acquisition program design.Vacuum pump,sampling pump,linear motor,stepper motor control and drive circuit.Prepared the hardware under the machine program.6)In order to ensure the interaction of man and machine,this paper designed a special aerosol measurement software including rights management,alarm management,historical data management and other data processing.In this paper,the continuous monitoring of radioactive aerosol is based on the existing,the application of new technology designed for the existing aerosol continuous monitor to adapt to a narrow range(can not be applied to high radon environment)problem,through the proposed dual-channel measurement Way to make the device response time greatly reduced.The theoretical detection limit of 10-4 ~ 10-3Bq / m3,verifiable detection limit of uranium 0.1Bq / m3,plutonium 0.02 Bq / m3.The test results show that the monitor has reached the advanced level at home and abroad.At present,the performance of the monitor is stable,the detection limit is low,can be used in a variety of low radon and high radon environment,radioactive aerosol monitoring.