JUNO high purity nitrogen plant

The Jiangmen Underground Neutrino Observatory (JUNO) is a 20 kt low level radioactivity liquid scintillator detector in a laboratory 650 m underground. An excellent energy resolution and a large volume offer exciting opportunities for addressing many important topics in neutrino physics. High purity nitrogen is an important factor to ensure the low background of the JUNO detector. High Purity Nitrogen (HPN) is used for detector purging, pipe cleaning, and scintillator purification, among other things in JUNO. According to JUNO's requirements, the radon concentration in HPN should be less than 10 mu Bq/m 3 . To meet this requirement, A high-purity nitrogen plant with 100 Nm 3 /h maximum rate was designed and constructed. Low-temperature adsorption technology is used to remove radioactive impurities in nitrogen. High purification efficiency was ensured by using an activated carbon column with high column height-to-diameter ratio. Electrostatic collection and low-temperature enrichment methods are combined to measure radon in nitrogen. After ten days of continuous operation at 50 Nm 3 /h flux rate, the plant can to reduce the radon concentration in nitrogen from 37 . 4 +/- 1 . 8 mu Bq/m 3 to less than 1.33 mu Bq/m 3 . After HPN with flow rate of 50 Nm 3 /h passing through low-background pipeline (About 1.3 km), the radon concentration of HPN is 5 . 6 +/- 0 . 6 mu Bq/m 3 .