Radon Infiltration Building Envelope Test System: Evaluation of Barrier Materials

The performance of radon barrier materials currently available for housing foundations was evaluated using a unique radon infiltration building envelope test system that was designed to test radon prevention and mitigation systems using real world construction techniques. The reduction in radon concentration measured across the air barrier in the foundations has been used to evaluate five representative barrier materials installed in the radon infiltration building envelope test facility. The reduction in radon concentration in the mock house varied from 68% for 6 mil polyethylene to 98% for the spray polyurethane foam. The five representative barrier materials were selected after determining the radon diffusion coefficient and the corresponding radon resistance from samples of 14 barrier materials in a radon diffusion testing chamber. The Canadian experience evaluating whether radon barrier materials would satisfy building code requirements was described.

Analysis of Equivalent Thickness of Geological Media for Lab-scale Study of Radon Exhalation

Geological media are widely distributed in nature. Lab-scale tests are frequently employed in radon studies for these media. Thus, it is critical to find the thickness of the medium at an experimental scale that is equivalent to the medium thickness in a real geological system. Based on the diffusion–advection transport of radon, theoretical models of the surface radon exhalation rate for homogeneous semi-infinite and finite-thickness systems were derived (denoted as Jse and Jfi, respectively). Analysis of the equivalency of Jse and Jfi was subsequently carried out by introducing several dimensionless parameters, including the ratio of the exhalation rates for the semi-infinite and finite-thickness models, ε, and the number of diffusion lengths required to achieve a desired ε value, n. The results showed that when radon transport in geological media is dominantly driven by diffusion, if n > 3.6626, then ε > 95% (and if n > 5.9790, then ε > 99.5%). When radon migration is dominantly driven by advection, if n > 2.5002, then ε > 95% (and if n > 4.0152, then ε > 99.5%). Therefore, if the thickness of the geological media (x0) is greater than a certain n times the radon diffusion length of the media (L), the media can be modeled as semi-infinite. To validate the model, a pure radon diffusion experiment (no advection) was developed using uranium mill tailings, laterite, and radium-bearing rocklike material with different thicknesses (x0). The theoretical model was demonstrated to be reliable and valid. This study provides a basis for determining the appropriate thickness of geological media in lab-scale experiments of radon exhalation.

Mathematical Expressions of Radon Measurements

The measurement of radon, thoron and their progeny concentrations also leads to the knowledge of the presence of radioactive elements, which are the sources of these elements such as Uranium-238 and Thorium-232. Using of Solid State Nuclear Tracks Detectors (SSNTDs) it is probably the most widely applied for long term radon measurements. In this chapter, we derived the most important mathematical relationships that researchers need in radon measurements to calculate such as average radon concentration, exhalation rate, equilibrium factor, radon diffusion coefficient and transmission factor to get actual radon concentration in air atmosphere. The relationship between theoretical and experiment calibration drive and other mathematical relationships are given in this chapter.

THE INFLUENCE OF PINHOLES IN WATERPROOFING MATERIALS ON THE VALUE OF THE RADON DIFFUSION COEFFICIENT

This article focuses on an experimental study of the influence of imperfections on the value of the radon diffusion coefficient of various waterproofing materials. Microscopic holes were made by a thin tip or by a microdrill bit to imitate the real damage that can be incurred during construction. To determine the change in the radon diffusion coefficient, each waterproofing material was measured five times. The first measurement was performed on undamaged samples, while the following measurements were performed on samples with one, two, four and eight pinholes. The radon diffusion coefficient was measured under nonstationary conditions, because homemade radon sources with a slow rate of radon emanation were used. The radon diffusion coefficients identified in the study were compared according to the thickness of the material and the number and the size of the pinholes. The exact shape and size of the imperfections were documented by an electron microscope.

The Determination of Radon Diffusion Coefficient and Radon Speed Advection in the Conditions of Instantaneous Source with Diffusion-Advective Transfer in Rocks

Experimental determination of diffusion parameters in the upper part of geological section (presented by clayey weathering crust) was made by a point instantaneous source method in a diffusion mode and a linear instantaneous source diffusion-advective mode. The results obtained by these methods showed a fairly good coincidence of the obtained diffusion characteristics of the medium. The time to determine the diffusion characteristics of the medium is significantly reduced by more than an order of magnitude when using the advective method. This is a prerequisite for the widespread use of methods for determining radon hazard based on measurements of the vertical distribution of radon volume activity in the upper part of the geological section.