Trilochana S, Somashekarappa H M, Kumara K Sudeep, Mohan M P, Nayak S Rashmi, D'Souza Renita Shiny, Kamath Srinivas S, Sahoo B K, Gaware J J, Sapra B K, Janik M, Al-Azmi Darwish, Mayya Y S, Karunakara N
Centre for Advanced Research in Environmental Radioactivity (CARER), Mangalore University, Mangalagangothri, Mangalore 574199, India.
Radiological Physics and Advisory Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400 085, India.
Radiat Prot Dosimetry. 2019 Dec 31;187(4):466-481. doi: 10.1093/rpd/ncz188.
A walk-in type 222Rn calibration chamber of volume 22.7 m3, which has traceability to international standards, is established at the Centre for Advanced Research in Environmental Radioactivity, Mangalore University, India. It has a human-machine interface communication system, a programmable logic controller and sensor feedback circuit for controlling and data acquisition of relative humidity (RH) and temperature (T). An innovative method for the generation of desired 222Rn concentration (a few hundred Bq m-3 up to about 36 kBq m-3) using soil gas as a source was adopted. Leak rates of 222Rn from the chamber for the mixing fan ON and OFF conditions were determined to be 0.0011 and 0.00018 h-1 respectively. With the exhaust system fully turned on, the maximum clearance rate of the chamber was 0.58 ± 0.07 h-1. Excellent spatial uniformity in 222Rn concentration in the chamber was confirmed (with a mean value of relative standard deviation < 12%) through measurements at 23 locations using CR-39 film-based passive devices. Demonstration of calibration applications was performed using charcoal canister and PicoRad vials as the 222Rn adsorption devices. The study shows that gamma spectrometry is a convenient alternative approach to liquid scintillation analysis of PicoRad vials for 222Rn measurement.
印度芒格洛尔大学环境放射性高级研究中心建立了一个体积为22.7立方米的步入式222Rn校准室，其可追溯至国际标准。它具有人机界面通信系统、可编程逻辑控制器以及用于控制和数据采集相对湿度（RH）和温度（T）的传感器反馈电路。采用了一种创新方法，以土壤气体为源生成所需的222Rn浓度（几百贝克勒尔每立方米至约36000贝克勒尔每立方米）。确定了混合风扇开启和关闭条件下校准室中222Rn的泄漏率分别为0.0011和0.00018每小时。排气系统完全开启时，校准室的最大清除率为0.58±0.07每小时。通过使用基于CR - 39薄膜的无源装置在23个位置进行测量，确认了校准室内222Rn浓度具有出色的空间均匀性（相对标准偏差平均值<12%）。使用活性炭罐和皮可拉德小瓶作为222Rn吸附装置进行了校准应用演示。研究表明，γ能谱法是用于222Rn测量的皮可拉德小瓶液体闪烁分析的一种便捷替代方法。
