核电厂烟囱流出物取样点选择和代表性验证

Selection and Representative Verification of Sampling Points for Effluent from Nuclear Power Plant Chimneys

核电厂在运行过程中会产生由气体所载带的、通过烟囱排放到大气环境中的放射性物质。对这些放射性物质的准确监测是有效评价核电厂对环境影响的基础。一般监测设备布置在烟囱下方,因而需要将烟囱排放的气载放射性物质通过取样的方式运输到监测设备。如果取样位置、取样管选型和布置设计不当,将严重影响监测结果,使得监测结果无法代表烟囱实际排放的放射性水平。结合标准《核设施气载放射性物质的取样导则》(ANSI/HPS N13.1—1999)的要求,对核电厂烟囱流出物取样点选择及其取样代表性进行试验验证。所述设计与验证流程已在某核电厂应用。应用结果表明,采用皮托管、热线风速仪、SF6示踪气体、气溶胶发生器等设备在烟囱缩比模型中验证气旋角、气流速度、气体浓度、气溶胶浓度分布方案可行。该气载取样代表性验证方案可以为核设施烟囱排放气载放射性物质的取样设计及验证提供参考。

During the operation of nuclear power plants,radioactive materials will be produced by the gas,which will be discharged into the atmosphere through the chimney.Accurate monitoring of these radioactive materials is the basis for effective assessment of the environmental impact of nuclear power plants.Generally,the monitoring equipment is arranged under the chimney,so the airborne radioactive material discharged from the chimney needs to be transported to the monitoring equipment by means of sampling.If the sampling location,sampling tube selection and layout design are not appropriate,the monitoring results will be seriously affected,so that the monitoring results can not represent the actual emission of radioactivity level of the chimney.In accordance with the requirements of ANSI/HPS N13.1-1999,the selection of sampling points for effluent from nuclear power plants'chimney and the sampling representativity were tested and verified.The design and verification process has been applied in a nuclear power plant.The application results show that it is feasible to use Pitot tube,hot-wire anemometer,SF6 tracer gas and aerosol generator to verify the cyclone angle,airflow velocity,gas concentration and aerosol concentration distribution in the chimney scale model.The representative verification scheme of airborne sampling can provide a reference for sampling design and verification of airborne radioactive substances discharged from the chimney of nuclear facilities.