Following its discovery by Dorn in 1900 [1] studies of radon and its progeny have contributed to many scientific fields but it is best known for being a significant cause of lung cancer. From the work of Paracelsus [2] and Agricola [3] it is clear that radon was responsible for the fatal lung disease of silver miners in Saxony and Bohemia in the 16^th century. In the 20^th century the causal role of radon and its short-lived progeny in lung cancers in underground uranium miners was established in the 1950s. From the mid 20^th century, stimulated initially by the work of Holmqvist in Sweden [4], there has been an ever-growing interest in the health effects of exposure of the general public to radon in their homes. Over recent decades a large body of radon epidemiological studies both of underground miners and the general population has quantified the radon lung cancer risks to both of these groups. Radon was classified in 1988 by IARC [5] as a human carcinogen mainly on the basis of the miner epidemiology. More recently the World Health Organisation International Radon Project in 2009 identified radon as the second cause of lung cancer after smoking [6]. Many governments now have established radon control strategies to reduce the risk to public health from radon. Apart from the health effects of radon it has also played a role in many scientific areas such as radiotherapy, meteorology and geophysics. Starting with the NASA Apollo lunar missions the detection and behaviour of radon and its progeny on the Moon have made contributions to our understanding of the geology of the Moon. There is currently a growing interest in radon behaviour on Mars which it is hoped will add to our knowledge of its volcanology and the availability of water on that planet.

1. E. Dorn, Über die von radioaktiven substanzen ausgesandte emanation. Abhandlungen der Naturforschenden Gesellschaft zu Halle (Stuttgart) 22, 155, (1900).
2. Paracelsus, Von der Bergsucht oder Bergkranckheiten drey Bücher, inn dreyzehen Tractat verfast unnd beschriben worden. Meyer Verlag (Bayerische Staatsbibliothek), (1567).
3. G. Agricola, De Re Metallica. Translated from the Latin by H. C. Hoover and L. H. Hoover (1950), Dover Publications Inc. 1556.
4. B. Hultqvist, Studies on naturally occurring ionizing radiations with special reference to radiation doses in Swedish houses of various types. Thesis (in English) Kungl. Svenska Vetenskapsakademiens Handlingar, No. 3, Series 4, 6, Stockholm, Sweden, (1956).
5. International Agency for Research on Cancer. Man-made mineral fibres and Radon. IARC Monographs on the Evaluation of Carcinogenic Risks to Humans, 43, IARC, Lyon (1988).
6. World Health Organisation, WHO Handbook on Indoor Radon, WHO, Geneva, (2009), pp. 94.

The reduction of the gamma-ray background contributes to the reduction of statistical errors of low activity measurements, while reduction of time variations of the background leads to lower systematic errors, especially in measurements of activities that coexist in the background. The sources of time variation of the background in a typical measurement of low activity are daily variations of radon concentration and aperiodic variations of cosmic-rays intensity. In this study we investigated the conditions that contribute to variations of radon and background by analyzing their time series in our ground level and shallow underground laboratories.

This study relies on the measurement activity concentration of stream sediments from the Băiţa-Plai brook, which is polluted by the spoil-banks of an abandoned uranium mine. Geologically speaking, the area is mainly formed out of sedimentary rocks, which are soluble in water, so they can travel large distances in this medium. We measured several radionuclide activity concentrations along the river using an Ortec GMX – type HpGe detector with relative efficiency of 34%. The investigated radionuclides were ²³⁸U, ²¹⁰Pb, ²³²Th, ²²⁶Ra, ¹³⁷Cs, and ⁴⁰K. The average activity concentrations were 260±45 Bq/kg for ²³⁸U, 50±4 Bq/kg for ²¹⁰Pb, 21±2 Bq/kg for ²³²Th, 80±4 Bq/kg for ²²⁶Ra, 2±0.2 Bq/kg for ¹³⁷Cs, and 383±15 Bq/kg for ⁴⁰K. We observed that the values were much higher at the upper side of the river and at the regions, where the settlements are and that they were lower at the estuary of the brook. We also measured limit exceeding levels of ²²⁶Ra concentration in the area of the settlements and the first sample had a much larger activity (546±20 Bq/kg) concentration than the concentration of a normal soil sample.

Geo-referenced datasets of indoor radon concentrations and radium concentrations in soil are available for the Republic of Macedonia. However, the indoor ²²²Rn data are spatially strongly clustered as the measurements were essentially confined to major towns and cities. Hence, the estimation of the geographical distribution of ²²²Rn concentration based only on the ²²²Rn data is difficult to be made. On the other hand, geochemical measurements ²²⁶Ra are quite well distributed over the country. Since ²²⁶Ra is the source of ²²²Rn, one may think of using ²²⁶Ra as a predictor for ²²²Rn. In this paper we present a method for modelling the stochastic dependency of indoor ²²²Rn of soil ²²⁶Ra. The method is new in the area on ²²²Rn assessment and still needs to be validated by more case studies.

The risk related to radon exposure may be expressed by the probability of exceeding a threshold of a quantity which is radiologically relevant with respect to radon, such as indoor concentration. Thresholds have been established as reference values for instance by the WHO, UNSCEAR or the new draft Basic Safety Standards proposed by the European Commission. Estimation of this risk is based on observed quantities which may be different ones from the target quantities relevant to risk assessment. Therefore it is necessary to assess the dependence of target and observed input quantities. Several “transfer models” have been proposed in the literature. However the most complete description of dependence requires multivariate probabilistic modelling of these quantities. In this paper the approach of copula modelling is introduced for this purpose. The method is demonstrated with an example of indoor and soil Rn concentrations or the Radon potential (RP), as observed in Germany. It is shown that a bivariate Gumbel copula appears appropriate to model upper tail (high risk) dependence reasonably. Several technical issues are shortly addressed which are typical for spatial data, such as data declustering and dealing with the collocation problem. As one result an indoor risk map of Germany is shown, predicted by soil Rn.

Researchers around the world had already established that radon and thoron are a hazard to the human health. Different techniques and methods are applied in order to measure them as accurately as possible. In Romania, most measurements earlier conducted were focused on using grab-sampling measurements to establish the two gasses decay progeny activity concentration; however, recently, there has been an increased interest in using passive devices together with active devices for long-term measurements. In order to get more accurate knowledge about the real radon and thoron indoor concentration in dwellings as well as in public buildings and work places, a new survey was carried out in 15 locations within and surrounding Birlad Town, Vaslui County. Passive methods including two types of discriminative detectors based on CR 39 chips as well as active measurements, such as RAD7 were used for this survey. During this survey, it was also pointed out the continuous difficulty in measuring thoron, due to its short half-life and faults in the measuring system.

Liquid Scintillation Counting (LSC) is a measuring technique, broadly applied in environmental monitoring of different radionuclides. One of the possible applications of LSC is the measurement of radon and thoron progeny. There are certain advantages of this method, especially high counting efficiency for alpha and beta particles emitted by radon and thoron progeny. This advantage has been pointed out several years ago, when such methods were applied to calibration of portable monitors for radon progeny, especially due to the fact that in the case of radon progeny no standard atmosphere exists. Radon and thoron progeny might be collected on a filter, which after immersion in the liquid scintillator becomes transparent and can be counted without significant quenching. Therefore such a method can be stated as an absolute one and can be widely used for radon progeny monitoring.
Both methods, LSC and TLD, can be used for calibration of decay product monitors. The LSC method has the advantage to be an absolute one, the TLD method to measure directly the (dose relevant) deposited energy.

OECD, Guidelines for the Testing of Chemicals recommend the alga growth inhibition test, in ecotoxicological studies, for assesing the exposure. Regarding the Radon exposure as a toxic exposure, we try to observe the induced effects, as a consequence of alpha particle deposition, on our Chlamydomonas culture kept 10 minutes at 400C and relative humidity 70%, in our in vitro exposure system, when the Radon concentrations was 500 Bq/m³ and 1000 Bq/m³. Control sample follow the same exposure, but for a background Radon level of 48 Bq/m³. The decrease of surviving rate has been observed, especially for 1000 Bq/m³ scenarios. In this light, this test shoud be very good for study of environmental exposure into the thermal area.

Adherence to the European Union (EU) means also that Romania must take into consideration the requirements which were established by scientific institutes of the UE. For the Institute of Reference Materials and Measurements (IRMM) these requirements refer to the unification of experimental methods, Certified Reference Materials in the relative methods and processing of obtained experimental data. These requirements are in conformity with those enforced by the International Quality Assurance Programmes. Also, these requirements ensure both the quality of the obtained results and the possibility of these results to be included in the continental and global database. The work continues a process of implementing the radon map in the Carpathians Curvature area (both internal and external) initiated in 1999 in cooperation with two institutions. The measurements are based on the method used by Debrecen Laboratory for Radon Measurements, with solid state detectors CR-39. The results carry forth high values in the researched area and, consequently, we draw your attention on the necessity of taking appropriate protection measures.

Radon concentration measurements were performed in all 25 primary schools in Banja Luka city, the capital of Republic of Srpska, during 2011 and 2012, using both active RAD7 continual Radon measuring instruments and CR-39 passive (commercially known as Gamma) detectors. The two complimentary methods were employed not only to obtain annual averages, but also to study the dynamics of radon concentration changes during the week. For each school, average and temporal variations of radon concentrations were analysed, taking into consideration local geology, building materials and meteorological conditions. The influence of forced ventilation, caused by frequent opening of doors and windows during working hours, with typical dawn and weekend peaks is evident in most but not all schools. Elevated levels of Radon concentration (>400 Bq m^-3) were found in a few schools using both methods. Although high correlation factor of 0.8 between passive and active methods was found, still shorttime (one-week) measurements cannot be used for annual estimation of radon activity but only as a screening one. Thus, the conclusion concerns only long time measurements as valid indicator of annual Radon activity.

In this paper a new method for preparation of any shape radioactive sources with a desired activity is described, by using ThO₂ in secular equilibrium for calibration in efficiency of a HPGe detector. By knowing the absolute specific activity of ThO2 and the disintegration probability of the γ- emitters from the ²³²Th series, the efficiency curve of the spectrometer was well determined for different shape of samples. We also used this method for preparation of calibration samples in Marinelli backers, by mixing a determined quantity of ThO₂ with artificial soil for environmental radioactivity measurements in different types of soils from the forest and uranium mines zones, in which radionuclides from the uranium family were identified and the total activity of the samples was determined.

The Vietnamese government has decided to build the first two nuclear power plants in Ninh Thuan province. This study reports the indoor radon (Rn) survey of the area in the vicinity of the nuclear plants to be built in this province. The survey was conducted during the years 2010-2011 in order to establish the radioactive background database of the province before the nuclear power plant is built and put into operation. Fifty nine locations (representing the 59 most populated of the 64 communes in the province) were investigated. Indoor Rn concentration was measured using Solid State Nuclear Track Detector (SSNTD) LR-115 type II strippable with 3 months exposure for the dose assessment of the future population. Rn concentration values gained during the survey were rather low in general compared to the data of other international surveys. The average was 10±5 Bq/m³ (min. 4 Bq/m³; max. 27 Bq/m³). From the point of view of dosimetry even the highest estimated effective dose originating from the Rn concentration is negligible. After the completion of the power plants, however, the previous background data have crucial importance in order to assess the concentrations due to the power plants and to provide credible information to the public.

The novel ENEA-INMRI Image Analyzer system has been tested in semi-automated mode for a computer-assisted alpha track counting of electro-chemically etched (ECE) and chemically etched CR-39 Solid State Nuclear Track Detector (SSNTD) chips. A track recognition program based on the Java-Image J processing software was developed. Experimental tests have been carried out to maximize the Field of View (FOV) value of the novel apparatus using appropriate optical magnification and digital video camera resolution. Experimental data on digital Charge Couple Device (CCD) camera and the Image J software performance, in particular a comparison of fixed and variable threshold option, are presented.

This work presents the development of a system which monitors the Radon level, using a PIN diode for detecting the radon particles and a data processing module with Wi-Fi communication capabilities for the transmission and management of measurement results. This solution represents an inexpensive, easy to use, portable radon detector which can be used for monitoring the radon level in a specific location or for being a part of a distributed monitoring system. The detector can send radon level measurements to a computer or a smart-phone or can be a part of an ad hoc network of sensors. Data can also be stored locally and therefore the system can be used in environments where wireless connectivity is not available at all times. The main advantage of the developed system is the long lifetime which may reach up to one or two years, due to the fact that it runs on batteries and that it uses ultra low-power Wi-Fi.

This paper presents the exact method for radon equilibrium determination by gamma spectrometry measuring of radon progeny concentrations in the air. The method is based on simultaneous sampling of air through the filter paper and alpha spectrometry measurement of radon activity concentration in the air. This paper derived a mathematical formula to calculate the initial concentrations of radon progenies ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi in the air at the start of sampling based on the detected count rate of post radon gamma lines in the sample of filter paper. Such a model containing the radioactive decay corrections during the time of sampling, cooling and measurement can be applied in other nuclear analysis where the half-life of the source has the same order of magnitude as the available recording time.

In order to achieve a fair description of radon transport through concrete certain information is needed on the concrete structure, porosity and permeability, on processes causing the transport of radon, on radon’s interaction with environment, factors favouring the generation of radon, etc.
The concrete characteristics (that depend on its composition and especially on the W/C ratio) which influence the transport of radon through concrete are, mainly, porosity, permeability, diffusion, humidity and density.
This paper presents the influence of W/C ratio and concrete density on apparent and overall porosity of concrete, permeability coefficient and diffusion coefficient. Also, we present influence of concrete permeability on the diffusion coefficient for many types of concrete prepared with different blended cements.
The results achieved confirm the quality of concretes prepared with cements with slag, even if results achieved for slag in radioactive contents did not anticipate this. Concretes prepared with cement with slag addition are less permeable to air and water, display a lower porosity compared to other concrete types surveyed.
A highly important parameter in the relation concrete - radon is the water / cement ratio, a ratio that influences the concrete characteristics and implicitly the radon concentration within buildings.

This paper presents the research program which consisted in the determination of concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K radionuclides in concretes prepared with some cement types with additions. The results achieved in the determination of concentrations of the main radioactive elements (²²⁶Ra, ²³²Th and ⁴⁰K) and of the radioactivity index are presented for various additions used in cements, blended cements and concretes prepared therewith.
The contribution of tested additions was assessed by adding them in the manufacturing process of different cement types. Thus, tests were performed on no-addition cements and cements with additions of slag, fly-ash, limestone, slag + limestone, puzzolana + limestone, fly-ash + slag.
The research program consisted in the determination of certain strength and durability characteristics (compressive strength, porosity, water and air permeability, etc.) of concretes prepared with cements with various additions and admixtures, in order to cross-reference results achieved with the radon exhalation rates and respectively the values acquired for the indoor radon concentration. During the research program, the strength characteristics, the air and water permeability were determined on concretes having various compositions, in order to enable cross-reference with radon exhalation rates.

Radon, ²²²Rn, is radioactive noble gas which decays by alpha emission with half-life of 3.825 d. Its short-lived progeny, ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi (²¹⁴Po), are alpha and beta radioactive and they emit gamma radiation as well. Radon progeny can be inhaled by humans where they deposit on the inner layers of bronchi, and bronchioles. Particles (alpha, beta and gamma) emitted in radioactive decay damage surrounding tissue which can lead to development of lung cancer. The Absorbed Fractions (AF) of electrons and beta particles in sensitive layers of human respiratory tract were calculated in this paper. For that purpose the MCNP5/X simulation software [1], based on Monte Carlo method, was used. The human respiratory tract was modeled according to ICRP66 publication [2].

1. X-5 Monte Carlo Team, MCNP–a General Monte Carlo N-Particle Transport Code, Version 5 Vol. I: Overview and Theory, Los Alamos, NM: Los Alamos National Laboratory; LA-UR-03-1987, 2003.
2. ICRP Human respiratory model for radiological protection. A report of a task group the International Commission on radiological protection, ICRP Publication 66, Pergamon, Oxford, 1994.

These work present results of preliminary study of radon concentration in soil gas at 64 locations within 13 urban areas of Bulgaria using AlphaGuard equipment. The measuring period was from 2008 to 2012. The temperature and humidity has been measured as well, including the gamma dose rate. The radon concentration in soil gas was found to be log-normally distributed within the range from 3–97 kBq.m⁻³, with arithmetic mean of 26 kBq.m⁻³. The influence of the meteorological and geological factors in relation to radon measurements was examined. Correlation between Radon in soil gas and gamma dose rate was also present.

A first step in mapping indoor radon concentration in Kosovo and Metohija was taken by carrying out 153 measurements in residential houses. About 21% of the territory of these areas was covered by mapping. Dosimeters with CR-39 detectors were used to measure indoor ²²²Rn concentration, all deployed on the ground floor of typical houses. The arithmetic mean (AM) over AMs within 10 km x 10 km grid cells is 202 Bqm^-3 and geometric mean (GM) is 148 Bqm^-3. The data for mapping are arranged according to recommendations made by the Joint Research Centre (JRC) of the European Commission (EC) in 2006. This paper presents the status of the survey of natural radioactivity in Kosovo and Metohija.

In this paper are presented the results of indoor radon survey in Bacău County. Radon measurements were made in 37 dwellings by using CR-39 nuclear track detectors exposed for approximately three months, during spring and summer. The study area contains locations from different parts of Bacău County, which was divided in 60 square cells of 10 x 10 Km out of which 20 (33%) were fully covered. Moreover, the radon detectors were placed only in dwellings, most of them situated in rural areas. The measured radon concentrations indicating a log-normal distribution, confirmed by the D’Agostino-Pearson test (K² = 0.88, p = 0.64). The average of indoor radon concentrations for Bacău County was found to be 58 Bq/m³. The values recorded in the study area vary from 18 to 180 Bq/m³, which is below the recommended action limit of ICRP.

Radon is a radioactive noble gas of natural origin that may be found anywhere in soil, air and in different types of water: surface, wells and springs. It is worth carrying out surveys for radon in natural water and indoor air for radiation protection as well for geological considerations. The results presented in this paper are from a survey carried out in Transylvania region, in North West of Romania for radon concentrations in water and indoor air. The measurements were made using a LUK-VR system based on radon gas measurements with Lucas cell for water and with track detectors based on CR-39 for indoor air.
The results show that the radon concentrations are within the range of 0.9 to 68.9 BqL^-1 with an average value of 11.4 BqL^-1 for all types of water covered within this survey. The indoor radon concentrations range from 26 Bqm^-3 to 415 Bqm^-3 with an average of 138.1 Bqm^-3.

This paper examines the possible occurrence of errors due to electromagnetic interferences during radon air concentration measurements. Using SIMULINK, two measurement methods were simulated and compared in terms of their susceptibility to perturbations. After analyzing the detection chamber and the analogue input stage, a method for eliminating the parasitic pulses passing through two measurement channels is described. The subsequent measurements were performed in areas exposed to high electromagnetic field levels and then compared with results obtained in areas with lesser exposure to electromagnetic fields. Two sets of final measurement results were presented by using alternatively an electronic measuring device as well as track detectors.

One of the aims of the First Intercomparison on Natural Radioactivity Under Field Conditions was to test different instruments and detectors for the measurement of radon gas and external gamma radiation (dose rate) in filed conditions, where the levels of natural radiation are quite high. The event was organized by the Radon group of University of Cantabria, (Spain) LaRUC, and was held in the end of May 2011, in the area of an old uranium mine of ENUSA, near Saelices el Chico (Salamanca, Spain). The following activities were performed: External gamma dose rate; Radon indoors with active and passive detectors; Radon outdoors; Radon in water; Radon exhalation rate from building materials; Radon exhalation rate from soil and Radon in soil gas. This work presents the main results of the intercomparison obtained by our group in all the exercises.

The report comprehends one decade experience in the use of the high radon absorption ability of bisphenol-A based polycarbonates for measuring radon. The three major directions of research and development include: (1) Use of the polycarbonate material, in particular that of which CDs/DVDs are made, as both radon absorber and track detector for measuring radon; (2) Use of a polycarbonate foil as an absorber that serves as radiator of an external detector; (3) Use of CDs/DVDs for combined retrospective measurements of radon and thoron. The emphasis is made on the application of CDs/DVDs as “radon sensors” available practically at any dwelling. This allows to develop an integrated approach to the radon problem. Within this approach the basic process “detection → diagnostic → mitigation” is considered as an united whole, all actions of which can be performed in relatively short time. This is illustrated with a case of kindergarten, one of the problem dwellings identified and mitigated during our year 2012 radon campaign.

The paper presents the most significant steps to be covered in the assurance of the continuity of the metrological chain, from the International System (SI) up to the end users. Some of them, such as realization of the primary standard, calibration of the secondary standard equipments and obtaining of receptacles with standard radon gas or dissolved in liquid scintillator, were already covered and published. The following operations regard the construction of a radon calibration chamber, to be used for the calibration of the equipment used for in field radon measurements and the validation of the system by participation at international comparisons. The paper is an overview of all these obtained and planned results.

In case of indoor conditions the probability of the radon accumulation is high, greatly depends on the features of the surrounding materials. In order to prevent the elevated indoor radon levels in buildings the influencing parameters of the migration and origin of the radon – generated in the building materials – should be investigated beyond the Ra-226 content. The natural radioactive content of 27 clay samples, which are used as raw material in brick factories were investigated in radiological point of view. The radon emanation factors were determined as well. The optimal sample thickness of the powdered and wet clay samples were determined in order to measure the free exhalation. The effect of the moisture content modifying the radon emanation was determined as well. The obtained results clearly prove that the measurement of emanation in dry state is not enough to characterize the radon emanation features and via that the radon exhalation capacity of the material.

The variation of outdoor ²²²Rn and ²²⁰Rn progeny concentrations were investigated for 5 years (2002 - 2006). The results presented in this paper were obtained within the framework of the monitoring program performed by the Environmental Radioactivity Monitoring Stations (ERMS) situated in Toaca, Iasi, Cluj Napoca, Craiova, Bucuresti and Constanta, part of the National Environmental Radioactivity Survey Network (NERSN), coordinated by National Environmental Protection Agency (NEPA). The measuring method is based on the total beta measurements of atmospheric aerosols filters, using a low background total beta counter and (⁹⁰Sr/Y) reference standard. Analysis of the time series of progeny concentrations in the low atmosphere makes evident different patterns of variation of these concentrations: diurnal, seasonal and annual variations.

The present paper presents the study of the multiple linear regression model for the estimation and prediction of the time series of radon and thoron progeny concentrations in atmosphere. Radon and thoron progeny data measured in Environmental Radioactivity Monitoring Station Botoşani, part of the National Environmental Radioactivity Survey Network are modeled, at different time scales, by making use of the multiple linear regression with meteorological parameters as independent variables. The collinearity and multicollinearity of independent variables have been analyzed. The estimations were checked by using the regression statistics: multiple correlation coefficient, coefficient of determination, F-test values, level of significance (p-value) and residuals. The predictions performances have been analyzed by means of the residuals, coefficient of determination and the relative error specific to each time interval from prediction period.

Radon and its decay products are the most important sources of natural radiation for the human exposure (UNSCEAR, 2000). As the second cause of lung cancer (after smoking), radon is received indoors, in houses and others buildings by the majority of the population exposed (ICRP, 1993). In the past decades, systematic radon surveys in dwellings were carried out all over the world (UNSCEAR 2000). Almost half of the radioactive dose is due to radon gas.
The objective of this present study was to estimate the lung cancer risk induced by exposures to radon for a period of 200-210 days in bedrooms at 1-1.5m distance from the floor. The mean measured radon concentration values were corrected for seasonal variations, depending on the time when detectors were exposed during the course of the year. The radon average concentration in the exanimate places was <C_Rn> = 112 Bqm^-3, C_Rnmin= 9 Bqm^-3 and C_Rnmax = 1127Bqm^-3. The geometrical mean of radon, GM, in studied areas were found to be 68 Bqm^-3. Distribution of indoor radon concentration in homes was: 32,7% in C_Rn[0-40 Bqm^-3], 31,5% in C_Rn[41-80 Bqm^-3], 11% C_Rn[81-120 Bqm^-3], 6,3% in C_Rn[121-160 Bqm^-3], and 18,1% in C_Rn[>160 Bqm^-3].

The linear no-threshold hypothesis (LNT) is a model of the damage caused by ionizing radiation which presupposes that the response is linear at all dose levels. Thus, LNT asserts that there is no threshold of exposure below which the response ceases to be linear. While most authorities agree that the LNT model is most appropriate, the advances in radiobiology during the past two decades, the understanding of carcinogenesis, and the discovery of defenses against carcinogenesis challenge the validity of the LNT model. These studies disagree with the LNT hypothesis suggesting that low levels of low LET radiation, below 100 mSv, may actually be positive or at least neutral to health, and suggest that the present LNT overestimates radiation risks. Therefore the dose-response particularly for low-doses and low dose-rates has to be further analyzed. The influence of genetics and genetic variation in individuals, as well as the response to high LET radiation is less clear. The objective of this study was to update the LNT debate by using the latest radiation biologic and epidemiologic data, as well as our predictions of the Transformation Frequency-Tissue Response (TF-TR) model. Low, chronic radon exposures are characterized by the occurrence of nontargeted effects (e.g. adaptive response, genomic instability) so their effect on the doseresponse curve was simulated with the mechanistic, biologically-based TF-TR carcinogenic model. Model predictions were in agreement with the linear no-threshold hypothesis at high radon exposures, but dose-response curves for low, chronic radon exposures (less than 4 cGy) were slightly different.

This study was conducted to review the latest research in radon problem carried out in the Republic of Moldova. The main aim of this paper was focused on the need for a National Radon Strategy (NRS) and a National Action Plan (NAP) for NRS implementation. Both NRS and NAP has to be correlated with other national policies, such as Smoking Reducing or Energy Efficiency. Development of a Radon Database including a map of radon concentrations, as well as a set of requirements for new housing construction, would be among the main components of NAP.

Several radioactive and radiation dose limit values should be kept for the remediation of waste rock piles and tailings ponds of former uranium mining. Using some 1m order of magnitude thick inactive cover on the tailings, the requirements for ambient gamma dose rate and for radioactive aerosol generation are fulfilled automatically. Keeping the limits for radon concentration in air and for radon exhalation rate from soil surface is more difficult task due to the high mobility of radon. Construction of suitable radon barrier on the emission sources (first of all: tailings ponds) is one of the basic points of remediation planning. A radon transport model has been developed to study the cover options and the acceptable versions of the available cover layer materials were experimentally surveyed in practice. In the present state the model deals onedimensional, stationary and single cover layer situations only. The basic soil-physical parameters are involved into the model and their role in radon exhalation rate is particularly analysed. Both the model calculations and the field experiments supported that the official requirements for radon exhalation rate are fulfilled well in the case of applied versions of cover.

The paper presents studies associated with the implementation of the indoor radon measurement technique using CR-39 nuclear track detectors and an automatic Radosys set-up in the Applied Nuclear Physics Department of the Horia Hulubei National Institute for Physics and Nuclear Engineering and new, in-situ, indoor radon data in various locations in South/South-East Romania.

In this paper the results of radon concentration measurements performed in 207 schools in 7 communities of Southern Serbia are presented. The annual radon concentration varied from 17 Bq m^-3 to 428 Bq m^-3 with a median value of 96 Bq m^-3. The arithmetic mean (AM) of the 207 annual averages was 118 Bq m^-3 with a standard deviation (SD) of 78 Bq m^-3. The best distribution fitting of radon concentration by log-normal function was obtained. The log-normal parameters are the following: geometric mean (GM) = 97 Bq m^-3, geometric standard deviation (GSD) = 1.9. In addition, a spatial distribution of the indoor radon concentration over the investigated areas is observed.

Indoor radon concentration was measured in all schools (n = 9) and kindergartens (n = 7) of Kremikovtsi district, Bulgaria, using passive integrating electret detectors. The study was based on two successive: short and long term set measurements. In first phase, the short term detectors were deployed in all frequently occupied rooms in ground floor. The exposure was during the summer vacation (2011) under close condition with 10 days duration. From the results of short term measurement we have found that the radon concentration in 4 schools and 5 kindergartens were above the recommended National level of 300 Bq m^-3 for existing buildings. In order to confirm the initial shortterm measurement long-term measurements for the period from September 2011 to April 2012, in the same buildings of schools and kindergartens were performed under normal functional conditions (second phase). Comparing the results obtained from the short-term measurements under close conditions with the results of long-term measurement, we found that measured values were in correlation (R = 0.817).

This paper deals with calculated effective doses that members of real population received from radon gas and its short lived progeny during air inhalation in their dwellings at field site Kalna in Eastern Serbia. There are two crucial parameters in effective dose calculation: Dose Conversion Factor (DCF) for particular subjects (including real gender, age and physical activity level) and indoor concentration of radon and its short lived progeny in field area. According to the results of indoor radon measurements in the area of former uranium mine, Kalna, the effective dose for this real population was estimated by using the dosimetric lung model, developed by authors according ICRP Publication 66. Authentic software was developed for determination of effective dose per unit inhaled activity of radon progeny, DCF expressed in unit [mSv/WLM]. The results, obtained according to ICRP 66 dosimeter lung model, were compared with results calculated according to ICRP Publication 65. The dosimetric results were, also, compared and discussed with epidemiological approach data, according to UNSCEAR.