Low Background Radon Concentration Enrichment Measurement

According to the requirements of the central detector background in the Jiangmen Neutrino laboratory,the 222 Rn in the natural radioactive background is the main source of radioactivity.The radon in water must be reduced to 0.2 Bq/m3,that is,the detection limit of the detector is m Bq/m3,and the concentration of radon in the liquid scintillator must be reduced to ?Bq/m3,which requires high performance for the detector.The low background noise can reduce the effect of background on the detection of solar neutrino,so that the detection of neutrino can proceed smoothly.However,there are currently no means and devices for measuring the background noise.For this purpose,a detection system for measuring the ultra-low background radon concentration needs to be developed.The Daya Bay Nuclear Reactor Neutrino Experiment is located within a cluster of caves in the Daya Bay Nuclear Power Station approximately 50 kilometers east of Shenzhen City,Guangdong Province.Its main scientific research objective is to detect neutrinos from the reactor and to accurately measure neutrinos.Blend angle ?13 [1].In order to reduce the influence of natural background on neutrino detection,it also provides suggestions for future control of radon concentration in the Jiangmen Underground Neutrino Observatory of Jiangmen underground laboratory.Through the measurement of the concentration of radon in the air and water in the Daya Bay underground laboratory and the radon exhalation rate at selected reference points,the protective effect of the hall walls,pool wall coverings and nitrogen seals were analyzed and evaluated.Through the preliminary study of the concentration of radon in the underground neutrino laboratory of Daya Bay,but limited by the sampling point and sampling data,it can be initially confirmed that the source of radon in the hall of the underground laboratory is the raking out of the hall wall.The source of radon concentration in the water in the hall EH1 is the decrepitation of the pool wall.Judging from the effect of radon prevention,the effect of concrete on wall decantation is not good.Perma Flex paint film can reduce the precipitation of pool wall ripples.However,if it is used for a long time,there will be aging damage,leading to the risk of leaking into the pool.The nitrogen seal reduces the helium concentration in the water and prevents the helium in the air from entering the water.In order to further reduce the concentration of radon in the air and water,as well as to prepare for the construction of the Jiangmen Neutrino experiment in JUNO,a good underground ventilation system and flood prevention methods are all necessary.For the measurement of nitrogen system,it is limited to the lower detection limit of commercially available helium products,which is generally Bq/m3.The nitrogen background is on the order of m Bq/m3.In response to this low background radon concentration measurement,a set of measuring devices for measuring and enriching m Bq/m3 concentrations was developed at the Institute of High Energy Physics of the Chinese Academy of Sciences in Beijing.Enrichment of bottled nitrogen by activated carbon results in an active enrichment efficiency to further complete the measurement of lower order radon concentrations.