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.

CONSEQUENCES OF USING HOME-MADE RADON SOURCES FOR MEASURING THE RADON DIFFUSION COEFFICIENT.

The applicability of home-made radon sources for determining the radon diffusion coefficient of waterproofing materials was studied for three representatives of materials with a high radium content: uraninite, slag concrete and filter sand. The results of our investigation confirmed that the radon production rate of home-made radon sources is significantly lower than the radon production rate of artificial sources. Consequently, home-made sources are usually unable to generate concentrations higher than 100 kBq/m3 in the source container. Therefore, they cannot be used for determining radon diffusion coefficients lower than 1 × 10-12 m2/s. In addition, when home-made radon sources are used, only time-dependent mathematical solutions of the non-stationary radon diffusion can be used for determining the radon diffusion coefficient from the measured data.

NEW, EFFICIENT AND GENERALLY APPLICABLE DESIGN OF RADON-PROOF INSULATIONS-A PROPOSAL FOR A UNIFORM APPROACH.

A comparison of existing methods used for dimensioning radon-proof insulations showed that they generate significantly different thicknesses. As a consequence, they fail to provide relevant information about the applicability of particular waterproofing materials. A new, generally applicable and simple method for dimensioning radon-proof insulation is therefore proposed here. It is based on comparing two values: the radon resistance of the insulation, and the minimum radon resistance. Whilst the radon resistance of a particular insulation can be provided by the manufacturers in technical data sheets in dependence on the thickness and the radon diffusion coefficient, the minimum radon resistance is tabulated in dependence on the radon risk of the foundation soils and the parameters of the building. The new method allows fast, reliable and optimized design of radon-prof insulations.

A NEW APPROACH TO THE ASSESSMENT OF RADON BARRIER PROPERTIES OF WATERPROOFING MATERIALS.

New definitions of the radon resistance and radon transmittance of waterproofing materials are introduced. They are based on the real steady-state radon distribution within the materials. Both quantities can therefore be considered as suitable parameters for the design of radon-proof insulations. A comparison between the existing definitions and the new definitions of radon resistance showed that the existing definition significantly underestimates the real radon resistance for a thickness to diffusion length ratio >0.8. It has also been proven that materials with different radon diffusion coefficients but with the same thickness to diffusion length ratio do not have the same radon resistance.

INTERNATIONAL STANDARDS ON FOOD AND ENVIRONMENTAL RADIOACTIVITY MEASUREMENT FOR RADIOLOGICAL PROTECTION: STATUS AND PERSPECTIVES.

Radiological protection is a matter of concern for members of the public and thus national authorities are more likely to trust the quality of radioactivity data provided by accredited laboratories using common standards. Normative approach based on international standards aims to ensure the accuracy or validity of the test result through calibrations and measurements traceable to the International System of Units. This approach guarantees that radioactivity test results on the same types of samples are comparable over time and space as well as between different testing laboratories. Today, testing laboratories involved in radioactivity measurement have a set of more than 150 international standards to help them perform their work. Most of them are published by the International Standardization Organization (ISO) and the International Electrotechnical Commission (IEC). This paper reviews the most essential ISO standards that give guidance to testing laboratories at different stages from sampling planning to the transmission of the test report to their customers, summarizes recent activities and achievements and present the perspectives on new standards under development by the ISO Working Groups dealing with radioactivity measurement in connection with radiological protection.

Sub-slab depressurisation systems used in the Czech Republic and verification of their efficiency.

Design principles for sub-slab depressurisation systems recently used in the Czech Republic for remediating existing buildings are described. Results of an efficiency analysis performed on the basis of data from >60 single-family houses are presented. It was found out that the efficiency varies between 70 and 98 %, which is twice greater than when additionally applied radon-proof insulation is used. The efficiency is mainly influenced by the vertical profile of the soil permeability and by the air-tightness of floors resting on the soil. Higher efficiency was found for houses with greater air-tightness of the floors and with a sub-floor layer with permeability higher than the permeability of the subsoil.

National radon programmes and policies: the RADPAR recommendations.

Results from epidemiological studies on lung cancer and radon exposure in dwellings and mines led to a significant revision of recommendations and regulations of international organisations, such as WHO, IAEA, Nordic Countries, European Commission. Within the European project RADPAR, scientists from 18 institutions of 14 European countries worked together for 3 y (2009-12). Among other reports, a comprehensive booklet of recommendations was produced with the aim that they should be useful both for countries with a well-developed radon programme and for countries with little experience on radon issues. In this paper, the main RADPAR recommendations on radon programmes and policies are described and discussed. These recommendations should be very useful in preparing a national action plan, required by the recent Council Directive 2013/59/Euratom.

Dealing with the increased radon concentration in thermally retrofitted buildings.

The influence of energy-saving measures on indoor radon concentration has been studied on the basis of a family house made of clinker concrete wall panels containing from 1000 up to 4000 Bq kg(-1) of 226Ra. Thermal retrofitting based on installing external thermal insulation composite system on the building envelope and replacing existing windows by new ones decreased the annual energy need for heating 2.8 times, but also reduced the ventilation rate to values<0.1 h(-1). As a consequence, the 1-y average indoor radon concentration values increased 3.4 times from 337 to 1117 Bq m(-3). The additional risk of lung cancer in the thermally retrofitted house increased to a value that is 125 % higher than before conversion. Methods for dealing with this enhanced risk by increasing the ventilation rate are discussed. Recovery of investments and the energy consequences of increased ventilation are studied in a long-term perspective.

Radon remediation and prevention status in 23 European countries.

Radon remediation and prevention aim at reducing indoor radon concentrations in the existing and new buildings. This paper gives an estimate of the number of dwellings where remediation or preventive measures have been applied so far in Europe. Questionnaires were sent to contact persons in national radiation protection authorities and radon-related research institutes. Answers from 23 European countries were obtained. Approximately 26 000 dwellings have been remediated in total. Millions of dwellings remain to be remediated and the number is increasing due to the rare use of radon prevention. These facts imply a need for an efficient radon strategy to promote radon remediation. Moreover, the importance of radon prevention in new construction and the regulations concerning radon in the national building codes should be emphasised.

Radon diffusion coefficients in 360 waterproof materials of different chemical composition.

This paper summarises the results of radon diffusion coefficient measurements in 360 common waterproof materials available throughout Europe. The materials were grouped into 26 categories according to their chemical composition. It was found that the diffusion coefficients of materials used for protecting houses against radon vary within eight orders from 10(-15) to 10(-8) m(2) s(-1). The lowest values were obtained for bitumen membranes with an Al carrier film and for ethylene vinyl acetate membranes. The highest radon diffusion coefficient values were discovered for sodium bentonite membranes, rubber membranes made of ethylene propylene diene monomer and polymer cement coatings. The radon diffusion coefficients for waterproofings widely used for protecting houses, i.e. flexible polyvinyl chloride, high-, low-density polyethylene, polypropylene and bitumen membranes, vary in the range from 3 × 10(-12) to 3 × 10(-11) m(2) s(-1). Tests were performed which confirmed that the radon diffusion coefficient is also an effective tool for verifying the air-tightness of joints.

New technique for the determination of radon diffusion coefficient in radon-proof membranes.

This paper describes a new device and a method to determine the radon diffusion coefficient in damp-proof membranes developed in the Czech Republic. The main advantage of the device is that it enables tests to be carried out in all the known measuring modes used throughout Europe. Two recently developed computer programs are presented for the numerical modelling of the time-dependent radon transport through damp-proof membranes. According to this method, the radon diffusion coefficient is derived from the process of fitting the numerical solution to the measured curve of radon concentration in a receiver container. Numerical simulation and measured data are also compared. Reasons for disagreements between different methods and specific configurations of the measuring device are also discussed.

Mitigation of ineffective measures against radon.

Reasons of low effectiveness of radon remedial measures have been studied on several unsuccessfully remediated houses. Based on the thorough analysis, factors responsible for failures are clarified. The possibilities of how to improve the effectiveness of installed measures are also discussed. Experience in this field is documented by several examples of additionally mitigated houses. After application of additional measures, indoor radon concentration in the studied houses decreased in average 5.3 times. Costs for additional mitigation were at least four times cheaper compared with costs required for installation of original measures.

Applicability of various insulating materials for radon barriers.

The effectiveness of various insulating materials for limiting radon entry into houses has been investigated under laboratory conditions. Results for the radon diffusion coefficient measurements in more than 80 insulating materials are summarized. We have discovered that great differences exist in diffusion properties, because the diffusion coefficient varies within four orders from 10(-13) m2/s to 10(-10) m2/s. A methodological approach is proposed in order to identify the minimal thickness of radon-proof membranes, depending on building and soil characteristics. General guidelines for the selection of radon-proof insulation are presented.