Design and realization of a radon chamber as a secondary standard

Abstract

The air-radon mixture is the most significant source of natural radiation in workplaces and within dwellings. Despite some uncertainty in the risk estimates, it is widely believed that greater the exposure to radon, greater the risk of developing lung cancer. To assess the radiological hazard, accurate measurements of radon concentrations are necessary. A large variety of radon monitoring instruments have been developed in the last years, usually calibrated in radon chambers containing a known radon concentration released within the chamber by a specific solid radium-226 source. Radon calibration chamber has been constructed to test and calibrate radon and radon progeny detectors at various environmental conditions and to study the characteristic behaviour of radon decay products. The potential use of the above mentioned facility is still under study to assess its reliability and the reproducibility of results with respect to several variables of interest. A new radon chamber has been designed, constructed, and tested at Nuclear Engineering Department of Palermo University. The design was chosen to meet the needs of several different radon detection techniques, both active and passive. The chamber is a cylindrical shape made of stainless steel with volume about 0.4 m3. It has also the possibility to expose passive radon detectors at different levels inside the chamber as well as the radon gas concentration inside the chamber can be maintained constant by a fan. The radon chamber consists of an exposure room, a radon reference monitor, an equipment for control of radon circulation and air features. The variables that can be changed and controlled are radon activity, gas pressure (in the range 700 – 1100 mbar), temperature (5 – 50 °C), and humidity (10-90%), respectively. A number of experiments have been conducted to study the influences of environmental parameters on the equilibrium factor. This chamber can be used to perform researches and studies on radon behaviour, to calibrating different types of detectors (passive and active) which are used for measuring radon and its daughters.