ISO/TS 11665-13 Measurement of Environmental Radioactivity - Air: Radon 222 - Part 13: Determination of Diffusion Coefficient in Waterproofing Materials: Membrane Bilateral Activity Concentration Test Method

The standard "ISO/TS 11665-13 Environmental radioactivity measurement - Air: radon 222 - Part 13: Determination of the diffusion coefficient in waterproofing materials: membrane bilateral activity concentration test method" published by the International Organization for Standardization (ISO) describes the different methods designed for the assessment of the radon diffusion coefficient in waterproofing materials such as bitumen or polymeric membranes, coatings or paints, and the assumptions and boundary conditions that must be met during the test. This standard is not applicable to porous materials, where radon diffusion depends on the porosity and moisture content.

For the purposes of this standard, the following terms and definitions apply:

• Material refers to the product according to a certain technical specification that is the subject of the test.
• Sample (material) refers to a certain amount of material selected from the production batch for the determination of the radon diffusion coefficient.
• The radon diffusion coefficient expresses the radon activity passing through a unit area of ​​a single-layer material of unit thickness per unit time due to molecular diffusion and the unit radon activity concentration gradient at the boundaries of this material.
• Equivalent radon diffusion coefficient, the radon diffusion coefficient of the multi-layer material is numerically equal to the radon diffusion coefficient of a homogeneous material of the same thickness as the layered material, and expresses the layer in which radon penetrates the same amount through the layered material.
• Radon diffusion length expresses the distance through which radon passes due to diffusion and its effectiveness decreases by a factor of "e" due to decay. Radon diffusion length is expressed with the relationship given in the standard.
• The diffusive radon surface exhalation rate expresses the value of the activity concentration of radon atoms leaving a material per unit surface area per unit time. For the purpose of this standard, only diffusion transport through the sample is considered.
• Non-stationary radon diffusion refers to the time-dependent radon diffusion through a sample when the radon activity concentration in the sample changes (depending on time, distance from the radon-exposed surface, and radon activity concentration in the source vessel) and the radon surface exhalation rate from the sample to the receiver vessel also changes. One-dimensional non-stationary radon diffusion is described by a partial differential equation. Non-stationary radon diffusion occurs when the radon activity concentration in the source vessel is not constant and during the time interval immediately following the moment when the constant concentration in the source vessel is established.
• Stationary radon diffusion (time-independent radon diffusion through the sample or steady radon diffusion) is characterized by a constant (time-independent) radon distribution within the sample and hence a constant radon surface exhalation rate from the sample to the receiving vessel.
• Absolute measurement of radon activity concentrations refers to the measurement of the time courses of radon activity concentrations in the source and receiver vessels used to calculate the radon diffusion coefficient. The duration of the absolute measurement may be shorter than or the same as the duration of the test.

When performing the test, a sample of the material under test is placed between the airtight source and the receiving containers and the joint is carefully sealed. The radon activity concentration in both containers is measured using the continuous or point measurement methods specified in the ISO 11665-5 and ISO 11665-6 standards.

By means of a radon source with a constant radon production rate, the radon activity concentration in the source vessel is maintained at a high level. Radon emitted from the sample is monitored using a calibrated radon monitor in the receiver vessel.

Using a suitable mathematical procedure, the radon diffusion coefficient is then calculated from the time courses of the radon activity concentrations measured in the source and receiver vessels and the area and thickness of the sample tested. In multilayer samples, the principle described above results in the determination of the equivalent radon diffusion coefficient.

Among the numerous testing, measurement, analysis and evaluation studies that our organization has provided for businesses in various sectors, with its trained and expert staff and advanced technological equipment, it also provides testing services defined in the standard “ISO/TS 11665-13 Environmental radioactivity measurement - Air: radon 222 - Part 13: Determination of diffusion coefficient in waterproof materials: membrane bilateral activity concentration test method”.