A Passive Diffusion 222Rn Sampler Based on Activated Carbon Adsorption

Abstract

A simple passive sampler for 222Rn with up to 24-hr integration times can be constructed by using a diffusion barrier to regulate the effective sampling rate of an ambient temperature activated carbon bed. The diffusion element serves to make sampler performance relatively independent of the properties of the type of carbon used. Satisfactory results are obtained if the total effective sample volume is kept well below the equivalent air volume of the activated carbon bed. The influence of various temperature and Rn profiles on the sampler's performance have been examined by experiment and by simulation. The amount of Rn adsorbed may be measured by gamma spectroscopy, by outgassing into an alpha scintillation flask, or by desorption into a liquid scintillator. In the latter case, a sensitivity of 0.2 pCi l-1 is obtainable for 24-hr exposures.

Radiological impact of phosphogypsum discharged into the Venice lagoon:222Rn

“…The method, with appropriate adjustment, has been used for decades [5][6][7]. Our research laboratory has developed and tested the method used for this study; it consists in placing the radon collectors, containing about 200 grams of activated carbon, on the ground of the landfill surface, within a PVC tube (diameter of 10 cm), inserted in the soil down to about 10 cm.…”

An Activated Charcoal-based, Liquid Scintillation - Analyzed Airborne Rn Detector

“…In most cases, it is assumed that activated charcoalbased, diffusion type Rn detectors are governed by the equation (Cohen and Nason 1986;Prichard and Marien 1985): The constant ( L + f / V ) serves the same role as the decay constant in radiological buildup or decay and will determine the time behavior of the detector. Normally, this constant is measured by first allowing the detector to absorb Rn for a set amount of time.…”

“…This problem was partly overcome by Prichard and Marien (1985) who extracted the Rn from the charcoal in their detectors by desorption into toluene. The toluene was drawn off from the charcoal, fluor was added and the mixture was counted by liquid scintillation methods for which numerous automated measurement systems exist.…”

Temperature calibration formula for activated charcoal radon collectors

“…PicoRad detectors are simple commercially available activated charcoal radon collectors that are particularly suitable for short-term radon assessment in dwellings and workplaces (WHO, 2009). In contrast with previous charcoal canisters (George, 1984;Cohen and Cohen, 1986) which required g-spectroscopy measurements, PicoRad detectors make use of the liquid scintillation counting method (Prichard and Marien, 1985;Schoreder et al, 1989) to estimate the adsorbed radon activity. It offers numerous advantages such as less charcoal needed (3 g), a lower determination limit (<5 Bq m À3 ) (Bem et al, 1999), a shorter collection time (<48 h), and possibilities for repeated and automatized scintillation measurements.…”