Application of the advanced radon diagnosis methods in the indoor building environment

The health risk and dose calculations from exposure to indoor radon and its decay products are generally based on long-term integral measurements and standard ICRP recommendations. In this context, the results of assessments predicate more about human activities inside the building instead of a quality and an effectiveness of applied measures against the radon. The present paper is focused on a set of different measuring techniques and methods practically used for a classification of buildings regarding to the radon protection requirements. The fundamental quantitative and qualitative procedures of radon transport pathways and radon sources analysis, commonly named as radon diagnostic methods are performed in detail.     

Significance of independent radon entry rate and air exchange rate assessment for the purpose of radon mitigation effectiveness proper evaluation: case studies

Two new single-family houses identified as insufficient with regard to existing radon barrier efficiency, have been selected for further examination. A complex set of radon diagnosis procedures has been applied in order to localise and quantify radon entry pathways into the indoor environment. Independent assessment of radon entry rate and air exchange rate has been carried out using the continuous indoor radon measurement and a specific tracer gas application. Simultaneous assessment of these key determining factors has turned out to be absolutely crucial in the context of major cause identification of elevated indoor radon concentration.     

氡析出率测量中的218Po非平衡修正

通过对传统的累积法测量氡析出率模型实验验证,发现得到的氡析出率明显偏低。对测氡仪器的工作原理与集氡罩中氡的浓度变化规律进行分析,发现是由于被测介质表面析出的氡不断进入集氡罩,218Po与氡没有平衡,造成测量的氡浓度明显偏低。通过非平衡修正得到了修正后的氡析出率测量理论模型。利用修正后的该模型得到的介质表面氡析出率与参考值符合得较好,误差小于7%。此外比较优值函数的取值也可发现:修正后的理论模型优值函数的取值小于传统模型,这表明修正后的理论模型更符合实际,该理论模型可应用于氡析出率仪的研制与改进。     

Identification of sources of high radon levels in Slovenian schools

The sources of radon were investigated in twenty selected schools with high room levels of radiation. A combination of radon measuring techniques was applied: etched track and electret detectors to obtain average indoor air radon concentration. devices to record radon concentration continuously and thus characterise its diurnal variation, and alpha scintillation cells to analyse air from potential sources of radon entry. In some cases, a single strong source was identified (e.g. sinks, sub-floor channels), while in others the poor quality of the basic concrete slab was responsible for high indoor radon concentrations. The combination of etched track and electret detectors and alpha scintillation cells was essential for locating these sources.     

Radon concentration measurements in bituminous coal mines

Radon measurements were carried out in Kozlu, Karadon and Uzülmez underground coal mines of Zonguldak bituminous coal basin in Turkey. Passive-time integrating method, which is the most widely used technique for the measurement of radon concentration in air, was applied by using nuclear etched track detectors (CR-39) in the study area. The radon concentration measurements were performed on a total of 42 points in those three mines. The annual exposure, the annual effective dose and lifetime fatality risk, which are the important parameters for the health of workers, were estimated based on chronic occupational exposure to the radon gas, which is calculated using UNCEAR-2000 and ICRP-65 models. The radon concentrations at several coal production faces are higher than the action level of 1000 Bq m(-3). It is suggested that the ventilation rates should be rearranged to reduce the radon concentration.     

Dosimetric calculations for uranium miners for epidemiological studies

Epidemiological studies on uranium miners are being carried out to quantify the risk of cancer based on organ dose calculations. Mathematical models have been applied to calculate the annual absorbed doses to regions of the lung, red bone marrow, liver, kidney and stomach for each individual miner arising from exposure to radon gas, radon progeny and long-lived radionuclides (LLR) present in the uranium ore dust and to external gamma radiation. The methodology and dosimetric models used to calculate these organ doses are described and the resulting doses for unit exposure to each source (radon gas, radon progeny and LLR) are presented. The results of dosimetric calculations for a typical German miner are also given. For this miner, the absorbed dose to the central regions of the lung is dominated by the dose arising from exposure to radon progeny, whereas the absorbed dose to the red bone marrow is dominated by the external gamma dose. The uncertainties in the absorbed dose to regions of the lung arising from unit exposure to radon progeny are also discussed. These dose estimates are being used in epidemiological studies of cancer in uranium miners.     

Indoor radon concentration forecasting in South Tyrol

In this paper a modern statistical technique of multivariate analysis is applied to an indoor radon concentration data base. Several parameters are more or less significant in determining the radon concentration inside a building. The elaboration of the information available on South Tyrol makes it possible both to identify the statistically significant variables and to build up a statistical model that allows us to forecast the radon concentration in dwellings, when the values of the same variables involved are given. The results confirm the complexity of the phenomenon.     

Effect of radon measurement methods on dose estimation

Different radon measurement methods were applied in the old and new buildings of the Turkish bath of Eger, Hungary, in order to elaborate a radon measurement protocol. Besides, measurements were also made concerning the radon and thoron short-lived decay products, gamma dose from external sources and water radon. The most accurate results for dose estimation were provided by the application of personal radon meters. Estimated annual effective doses from radon and its short-lived decay products in the old and new buildings, using 0.2 and 0.1 measured equilibrium factors, were 0.83 and 0.17 mSv, respectively. The effective dose from thoron short-lived decay products was only 5 % of these values. The respective external gamma radiation effective doses were 0.19 and 0.12 mSv y(-1). Effective dose from the consumption of tap water containing radon was 0.05 mSv y(-1), while in the case of spring water, it was 0.14 mSv y(-1).     

Detection properties of a measuring system for a continuous soil radon concentrations monitoring.

The continual soil-gas radon concentration measurements are absolutely crucial for a reliable assessment of radon entry characteristics into the indoor building environment. For this purpose, a new detection system (a continuous monitor RM-3) was developed and tested. The detection principle of the monitoring device is based on an airflow ionisation chamber operating in a current mode. A comprehensive series of testing and calibration experiments have been carried out in a laboratory environment. An output signal of the device caused by the radon concentration in a sensitive detection volume significantly depends on a detector ventilation rate, the gas flow rate through the ionisation chamber. A set of calibration experiments was accomplished with the artificial radon source application and close circuit experimental arrangements. The system detection properties including applied experimental conditions and key results of pilot in situ measurements are reported in detail.     

Determination of the diffusion coefficient and solubility of radon in plastics

This paper describes a method for determination of the diffusion coefficient and the solubility of radon in plastics. The method is based on the absorption and desorption of radon in plastics. Firstly, plastic specimens are exposed for controlled time to referent (222)Rn concentrations. After exposure, the activity of the specimens is followed by HPGe gamma spectrometry. Using the mathematical algorithm described in this report and the decrease of activity as a function of time, the diffusion coefficient can be determined. In addition, if the referent (222)Rn concentration during the exposure is known, the solubility of radon can be determined. The algorithm has been experimentally applied for different plastics. The results show that this approach allows the specified quantities to be determined with a rather high accuracy-depending on the quality of the counting equipment, it can be better than 10 %.     

Radon risk in Alpine regions in Austria: risk assessment as a settlement planning strategy

Soil gas radon measurements complement indispensable and well-established radon indoor measurements in Austria. Radon in soil gas is a result of geochemical conditions as well as of geology, mineralogy, geophysics and meteorology. Therefore, geological factors can help to predict potential indoor radon concentrations via soil gas. Soil gas radon measurements in well-defined geological units give an estimate of local and regional radon hazards and build the basis for radon risk maps, which could be used for land-use planning and urban development. The creation of maps makes an important contribution to health care. For this purpose, several research projects were carried out in Austria. On the one hand, a study was already conducted in Lower Austria to determine the influence of meteorological and soil physical parameters on radon concentrations in soil gas and to evaluate soil gas radon concentrations with a radon emanation and migration model. On the other hand, radon measurements on different geomorphologic formations in the Austrian Alps, which are potential settlement areas, are of special interest.     

Radon programme: presence and future

An overview of radon programme experience is presented. The paper summarises broad topics concerning radon issue: philosophy of radon policy, radon measurements strategies with respect to indoor radon variation, progress in radon measurement of an individual house (radon diagnosis), national programmes, the role of preventive measures and interventions with respect to existing and future exposure and knowledge of radon risk, problems of remediation strategies, radon mapping process and sense of delineation of radon prone areas, public awareness on radon issue and publicity campaign. Some research activities are proposed aiming at effective solutions for radon issues in the future.     

Indoor and soil gas radon simultaneous measurements for the purpose of detail analysis of radon entry pathways into houses

Detailed knowledge of radon transport mechanisms from the subsoil into the indoor environment is essential for the correct interpretation of results of short-term indoor radon measurements and for proper and effective design of radon mitigation systems. Radon transfer factor time variations have been studied based on simultaneous continuous indoor and soil gas radon measurements within the framework of complex radon diagnosis of individual buildings. In this context, the key influencing factors have been identified and analysed in order to provide satisfactory explanation on radon entry variations under different measurement conditions. Moreover, a new significant manner of radon entry into the indoor environment has been identified and will be discussed in detail.     

Radon in soil gas--investigation and data standardisation at radon reference sites, Czech Republic

Radon risk mapping at building sites in the Czech Republic indicate an advisable level of protection of buildings against the penetration of radon from the geological basement. Various techniques and instruments are used for the measurement of radon in soil gas. A national radon chamber and three radon reference sites in Central Bohemia enable radon data standardisation. Tests of field radon measurements and the reported radon activity concentration in soil gas at the reference sites are based on comparisons with other organisations and with a database of reference site measurements. The radon reference sites have been used for various investigations of radon in soil gas during the period 2000-07.     

A preliminary radon map for Canada according to health region

The recent publications of the combined analyses of residential radon studies in Europe and North America have shown that there is a significant risk of lung cancer at residential radon levels. In order to assess the population risk due to radon, the knowledge of the spatial distribution of indoor radon levels is essential. Here a preliminary radon map for Canada is presented, based on historical radon measurements collected in 6016 locations across Canada with the health region as the basic geographic units.     

Radon hazard and risk in Sussex, England and the factors affecting radon levels in dwellings in chalk terrain

A survey was undertaken of radon levels in 1013 dwellings in Sussex, UK. A number of dwellings were identified with high radon levels in an area previously considered to offer low radon risk from geological sources. Multiple regression was used to determine the relative influence of the various geographical and building-related factors on indoor radon levels. The radon hazard, independent of building-related effects, was determined for each surveyed location by standardising radon measurements to a 'model' dwelling. These were entered into a geographic information system and related to surface geology. The highest radon levels were found to be associated with the youngest Chalk formations, Tertiary deposits and Clay-with-flints Quaternary deposits in the area. Radon potentials were also determined for the area which can be used to estimate radon risk and assist in environmental planning and development control.     

Development and management of a radon assessment strategy suitable for underground railway tunnelling projects

The construction of underground tunnels through radon-bearing rock poses a radiation health risk to tunnelling workers from exposure to radon gas and its radioactive decay products. This paper presents the development and practical application of a radon assessment strategy suitable for the measurement of radon in tunnelling work environments in Hong Kong. The assessment strategy was successfully evaluated on a number of underground railway tunnelling projects over a 3 y period. Radon measurements were undertaken using a combination of portable radon measurement equipment and track etch detectors (TEDs) deployed throughout the tunnels. The radon gas monitoring results were used to confirm that ventilation rates were adequate or identified, at an early stage, when further action to reduce radon levels was required. Exposure dose estimates based on the TED results showed that the exposure of tunnel workers to radon did not exceed 3 mSv per annum for the duration of each project.     

Radon dynamics and reduction in an underground mine in Brazil. Implications for workers' exposure

This work was aimed at studying the behaviour of 222Rn in an experimental underground copper mine in Brazil with a single entrance. The 222Rn concentrations, meaured by using a dynamic radon measuring technique. varied between 30.5 Bq.m(-3), during ventilated conditions applied to the mine galleries, and 19.4 x 10(3) Bq.(-3) for non-ventilated conditions and when operational mining activities were conducted inside. High radon concentration surges were observed after blasting and drilling activities. In the cases of inadequate ventilation, it was estimated that workers could be subjected to exposures as high as 10 microSv.h(-1), only due to 222Rn and its short-lived progeny. The results show the importance of real-time measurements to evaluate radon dynamics during mining operations.     

Are radon gas measurements adequate for epidemiological studies and case control studies of radon-induced lung cancer?

The lung dose derived from radon is not attributed to the radon gas itself, but instead to its short-lived progeny. However, in many epidemiological studies as well as in case control studies of the radon risk, the excess number of cancers are related to the radon gas exposure, and not to the radon progeny exposure. A justification for such an approach has resorted to the assumption that there is self-compensation between the radiation doses from the unattached and attached fractions. In the present study, we used the Jacobi model to calculate the radon progeny concentrations in a room by varying the attachment rate and then calculated the resulting lung dose. It was found that self-compensation was not fully realised, and the effective dose can vary by a factor up to approximately 2 for the same radon gas concentration. In conclusion, the radon gas concentration alone does not provide adequate information on the effective dose.     

Discussion on framework of radon management strategy in various environments

Activities on radon management strategy of international organisations (International Atomic Energy Agency, International Commission on Radiation Protection, etc.) should be carefully and continuously traced to discuss how to control radon in various environments, for example, dwellings, workplace, underground, caves, mines, hot springs, disposal facilities and so on. It is more reasonable in parallel to set radon reference level by effective dose criteria of Sv y(-1) as well as by radon concentration in air of Bq m(-3). How to investigate radon concentration in each environment, and how to make decisions on needed action for radiation protection from natural radon,--these should be discussed for each environmental situation on a case-by-case basis. International discussion as well as domestic discussion is continuously needed, not only among the radon specialists and regulators, but also including stakeholders who are the main users of regulation and guidance.