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 μ Bq/m3. To meet this requirement, A high-purity nitrogen plant with 100 Nm3/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 Nm3/h flux rate, the plant can to reduce the radon concentration in nitrogen from 37. 4 ± 1. 8 μ Bq/m3 to less than 1.33 μ Bq/m3. After HPN with flow rate of 50 Nm3/h passing through low-background pipeline (About 1.3 km), the radon concentration of HPN is 5. 6 ± 0. 6 μ Bq/m3. • The high purity nitrogen plant with maximum flow rate of 100 Nm3/h was constructed. • The radon concentration in HPN radon is lower than 1.33 uBq/m3 after 10 days of continuous running of HPN plant. HPN with design flow rate of 50 Nm3/h after passing through low-background pipeline (about 1.3km),the radon concentration of HPN is 5.5 ± 0.6 uBq/m3, which meets JUNO requirements in the underground. [ABSTRACT FROM AUTHOR]