An intercomparison of indoor radon data using NTD and different dynamic recording systems

Indoor radon data monitored with several different recording systems in a controlled cellar were analyzed. The one-room cellar is carved into volcanic rock and presents an almost constant radon emanation throughout the year. Measurements were performed using the AlphaGUARD^®, Sun Nuclear^® 1027, DOSEman^® and RAD7^® radon monitors, and CR-39 Lantrack^® in a passive integrating detector. The radon concentrations measured by the active detection systems and averaged over the three-month measurement period ranged from 533 to 805 Bq m⁻³. The response of the passive detector system was a linear function for exposure times of one, two and three months. The data are discussed as a function of changes in the distribution of radon within the cellar and the response characteristics of the detection devices.     

Indoor radon measurements in a Greek city located in the vicinity of lignite-fired power plants

This work presents indoor radon measurements in 42 dwellings in the city of Megalopolis, Southern Greece, located in the vicinity of 2 lignite-fired power plants and examines the effect of season, floor level and age of the dwellings on indoor radon concentration. The radon measurements have been carried out using the LR-115, type II and CR-39 alpha track detectors in “closed-can” geometry. The average annual indoor radon concentration (GM) was found to be 52 Bq m^?3, which is well below the recommended action level of the European Union. This value corresponds to an annual effective dose to the population of 1.3 ± 0.4 mSv. Season and age of the examined dwellings represent factors that affected significantly the indoor radon in Megalopolis, while the effect of floor level appeared to be not significant. Radium activity concentration values, measured by γ-ray spectrometry in 20 sub-samples of six soil cores (60–135 cm depth), collected from the surrounding area of the city, were found to be consistent with the Greek and world average values. Based on the results of this study, it is concluded that the effect of the lignite-fired power plants on indoor radon concentration in Megalopolis’ dwellings was not significant.     

Study of radon transport through concrete modified with silica fume

The concentration of radon in soil usually varies between a few kBq/m³ and tens or hundreds of kBq/m³ depending upon the geographical region. This causes the transport of radon from the soil to indoor environments by diffusion and advection through the pore space of concrete. To reduce indoor radon levels, the use of concrete with low porosity and a low radon diffusion coefficient is recommended. A method of reducing the radon diffusion coefficient through concrete and hence the indoor radon concentration by using silica fume to replace an optimum level of cement was studied. The diffusion coefficient of the concrete was reduced from (1.63 ± 0.3) × 10⁻⁷ to (0.65 ± 0.01) × 10⁻⁸ m²/s using 30% substitution of cement with silica fume. The compressive strength of the concrete increased as the silica-fume content increased, while radon exhalation rate and porosity of the concrete decreased. This study suggests a cost-effective method of reducing indoor radon levels.     

Seasonal indoor radon concentration in FYR of Macedonia

This paper presents the results of the seasonal indoor radon concentration measurements in dwellings in all regions of the Former Yugoslav Republic (FYR) of Macedonia. The measurements were made in 437 dwellings using CR-39 track detectors over four successive three-month periods (winter, spring, summer and autumn) throughout 2009. The results of analysis of variance showed statistically significant differences between indoor radon concentrations in different seasons. The geometric mean values and geometric standard deviations of indoor radon concentrations in winter, spring, summer and autumn were obtained to be: 115 Bq m^?3 (2.02), 72 Bq m^?3 (1.97), 46 Bq m^?3 (1.95), 92 Bq m^?3 (2.02), respectively. The geometric mean values of spring, summer and autumn to winter ratios were found to be: 0.63 (1.50), 0.40 (1.81), and 0.80 (1.58), respectively. The results of the analysis of the variance showed statistically significant differences among the indoor radon measurements for the regions in different seasons. The influence of the factors linked to building characteristics in relation to radon measurements in different seasons was examined. The factors which enable a differentiation into subgroups (significance level p < 0.05) are the floor level, basement and building materials.     

Systematic grid-wise radon concentration measurements and first radon map in Cyprus

A systematic study of the indoor airborne radon concentration in the central part of the Nicosia district was conducted, using high-sensitivity active radon portable detectors of the type “RADIM3A”. From a total of 108 measurements in 54 grids of 1 km² area each, the overall mean value is 20.6 ± 13.2 Bq m^?3 (A.M. ± S.D.). That is almost twice less than the corresponding average worldwide value. The radon concentration levels in drinking water were also measured in 24 sites of the residential district, using the high-sensitivity radon detector of the type “RADIM3W”. The mean value obtained from these measurements is 243.8 ± 224.8 mBq l^?1, which is relatively low compared to the corresponding internationally accepted level. The associated annual effective dose rates to each measurement were also calculated and compared to the corresponding worldwide values. From the geographical coordinates of the measuring sites and the corresponding radon concentration values, the digital radon map of the central part of the Nicosia district was constructed for the first time, by means of the ArcMap software package.     

Influences on indoor radon concentrations in Riyadh,Saudi Arabia

The influences on indoor radon concentrations in Riyadh, Saudi Arabia survey was carried out for 786 dwellings. The measurements were obtained by using a passive integrating ionization system with an E-Perm^® Electret ion chamber. Radon levels ranged from 1 to 195 Bq m⁻³, with a mean value of 24.68 Bq m⁻³, the geometric mean and the geometric standard deviation are 21 and 2 respectively. 98.5% of the results were below the action level recommended by WHO of 100 Bq.m⁻³. The results were found to vary substantially due to types of houses and rooms, ventilation, seasons and building materials. Radon concentrations were higher in houses with no ventilation systems, and central air conditioners, and were relatively lower in well ventilated houses with red bricks and water air conditioners.     

A comparative study of indoor radon levels and inhalation dose in some areas of Punjab and Haryana, India

Indoor radon concentrations have been measured for two consecutive half-year periods in a wide range of dwellings of some regions of Punjab and Haryana states. The objective was to find correlation between the variations of indoor radon levels with the sub-soil, local geology, type of building materials, etc. of the two regions. So keeping this in view the indoor radon measurements have been carried out in the dwellings of different villages around the Tusham ring complex, Bhiwani District, Haryana, known to be composed of acidic volcanics and the associated granites along with some villages of Amritsar District, Punjab. The indoor radon concentration in the dwellings around Tusham (Haryana) have been found to be varying from 120.5±95 to 915.2±233 Bq m⁻³, whereas it ranges from 60.0±37 to 235.6±96 Bq m⁻³ for the dwellings of Punjab. The ²²²Rn concentration observed at most of locations particularly around Tusham ring complex region is higher than that of all the villages studied in Punjab region. Local geology including embedded granitic rocks, sub-soil, etc. as well as building materials having higher radioactive content are the major contributors for the higher indoor radon levels observed in the dwelling around Tusham, where few dwellings have higher radon concentrations than the ICRP, 1993 recommendations. The annual effective dose equivalent has also been estimated for each location of the both regions, which has been found to be varying from 1.0 to 17.2 mSv/y.     

The use of soil gas as radon source in radon chambers

A procedure is described in which soil gas is utilized as an alternative to the ²²⁶Ra source for the supply of the radon gas required to fill a radon chamber where radon-measuring devices are calibrated. The procedure offers opportunities to vary the radon concentration within the chamber around an average value of about 500 Bq/m³, which is considered to be sufficient for calibrating indoor radon detectors. The procedure is simple and the radon source does not require radiation protection certification (for import and/or use), unlike the commercially produced standard radioactive (²²⁶Ra) sources.     

National survey of indoor thoron concentration in FYR of Macedonia (continental Europe – Balkan region)

As a part of the national survey of natural radioactivity in The Former Yugoslav Republic of Macedonia, indoor thoron gas concentration was measured in 300 dwellings during one year, from December 2008 till December 2009 using passive discriminative radon–thoron detectors. Detectors were deployed at a distance of >50 cm from walls in order to be less sensitive to distance from walls. Altogether 532 measurements were performed: 53 in winter, 57 in spring, 122 in summer and 300 in autumn. The frequency distribution is well described by a log-normal function. The geometric means of indoor thoron concentration (with geometric standard deviations in brackets) in winter, spring, summer and autumn were obtained to be: 39 Bq m⁻³ (3.4), 32 Bq m⁻³ (2.8), 18 Bq m⁻³ (2.8), 31 Bq m⁻³ (2.9), respectively. Seasonal variations of thoron appear lower than those of radon. The seasonal corrected annual mean concentration ranges between 3 and 272 Bq m⁻³ with a geometric mean of 28 Bq m⁻³ (2.12). A detailed statistical analysis of the geogenic and building factors which influence the indoor thoron concentration is also reported. This survey represents the first national survey on indoor thoron in continental Europe.     

Exposure to radon in the radon spa Niška Banja,Serbia

There is a well-known radon spa Ni?ka Banja in south-east of Serbia. In Ni?ka Banja spa there is a medical complex and radon is used for therapeutic purposes for many different diseases. This paper presents elevated radon levels in the Ni?ka Banja spa. Indoor radon and radon in water activity concentration measurements in thermal pools and therapy rooms are presented. There are also results from gamma spectrometry measurements of soil, rock and therapy mud. A special attention is paid to the medical staff exposure to radon around thermal pools. The annual effective doses from radon for staff working around the thermal pools in Ni?ka Banja spa are very high comparing to the maximum recommendation level. The maximal radon concentration of (22.90 ± 0.57) kBq m^?3 was measured in the basement of the hotel-dispensary “Radon”. This hotel is settled on “bigar” rock – travertine, which has high content of ²²⁶Ra.     

Seasonal and location dependence of indoor and soil radon concentrations in two villages,Najran region,Saudi Arabia

Seasonal (winter-summer) indoor and soil radon comparison is made in two villages in Najran region, south west of Saudi Arabia, using CR-39 Dosimeter. Summer indoor radon concentrations were measured in the villages of Fara Al-Jabal and Hadadah. The respective winter-summer average values of 42 ± 4 Bq m⁻³ and 74 ± 5 Bq m⁻³ are measured in Fara Al-Jable village and the average values of 47 ± 4 Bq m⁻³ and 76 ± 5 Bq m⁻³ are measured in Hadadah village. The respective winter-summer soil values are 1.40 ± 0.21 kBq m⁻³ and 0.99 ± 0.04 kBq m⁻³ in Fara Al-Jabal village while those measured in Hadadah village are 2.90 ± 0.17 kBq m⁻³ and 1.40 ± 0.66 kBq m⁻³. Indoor radon levels are found to be seasonal dependent while that of soil are found seasonal and location dependent. Meteorological and geological factors are expected to have caused the measured significant differences in radon levels in dwellings and soil in the two villages.     

Experimental and theoretical study of radon levels and entry mechanisms in a mediterranean climate house

An experimental study has been carried out in an inhabited single-family house. Radon concentration in the different rooms of the house and in its garden soil has been measured with Nuclear Track Detectors. No high differences of radon concentration have been observed between the different rooms of the house, so that the proximity of the room level to the soil seems not to affect the radon concentration. The annual radon concentration obtained indoors and in the soil has been respectively 35 Bq m⁻³ and 24 kBq m⁻³. Since radon generation in the source, entry into indoor air and accumulation indoors depend on several parameters, the effect of a specific parameter on indoor radon concentration is difficult to explain from the radon measurements only. The RAGENA (RAdon Generation, ENtry and Accumulation indoors) model has been adapted to the room in the basement of the house. The mean radon concentration values obtained with the model are compared to experimental results derived from measurements using Nuclear Track Detectors. The use of the model, together with the experimental study, has allowed characterising radon sources, levels and entry mechanisms in the house. The concrete walls have been found to be the most relevant radon source, while the contribution of the soil is negligible in this case. The indoor radon level is given by the balance of the permanent exhalation from concrete and the removal due to ventilation. The indoor radon levels are close to the average value for the Barcelona area which, in turn, is close to the world averaged value.     

Natural radiation background in the ancient city of Palmyra

Natural radiation background has been determined for the Ancient City of Palmyra and its surrounding areas. Car-borne gamma spectrometry, indoor radon gas concentration and natural radionuclides levels in environmental samples (soil, water and plants) have been determined. Two types of dwelling were involved in this study, one with cancer cases, and the others without. The results showed that indoor radon gas concentrations and radiation exposure rates are within reported mean background levels in Syria (45 Bq m^?3 and less than 0.1 μSv h^?1, respectively); no differences were noticed between the dwelling groups. In addition, the results did not indicate any relation between recorded cancers and measured natural radioactivity.     

Efficiency of ionizers in removing airborne particles in indoor environments

Air ionizers are increasingly being used to clean indoor environments of particle pollution. We tested the efficiency of a small negative ion generator (Aironic AH-202) in removing ultrafine particles from indoor environments. A high-flow air filter fitted with a HEPA filter was used to compare the removal efficiencies. We estimated the percentage of particles removed when the ionizer was operated within a closed chamber of volume 1 m³, in a closed unventilated room of volume 20 m³ and in three force-ventilated rooms of volume 32, 45 and 132 m³. The closed chamber studies were conducted with ambient particles and with smoke at particle number concentrations of 5 × 10³ and 7 × 10⁴ cm⁻³, respectively. In both cases, 70% of the particles were removed by the ionizer in 15 min. In general, the particle removal efficiency of both the ionizer and the air filter decreased as the room size increased. Both devices were also more effective in unventilated rooms than in ventilated rooms. The most important finding in this study was that, while the air filter was more effective than the ionizer in the two small rooms, the ionizer was clearly more effective than the air filter in the three largest rooms. We conclude that air ionizers are more suited than high-flow air filters in removing ultrafine particles from rooms larger than about 25 m³. The investigation also showed that small ions produced by the ionizer, placed in one room, were carried through the air conditioning system into other rooms, effectively removing particles from the air in these rooms in the process.     

Radon levels in underground workplaces – results of a nationwide survey in Italy

In Italy an extensive survey has been carried out with the aim to evaluate annual average radon concentration in underground workplaces.The survey covered 933 underground rooms located in 311 bank workplaces spread throughout in all Italian regions; at this scope the sampling was stratified random in order to be representative on national scale. The annual radon concentration was estimated by using passive radon dosemeters (NRPB/SSI type holder and CR-39 as detector): the devices were exposed for a period of about 3 months and 4 cycles were performed to cover a solar year. The radon levels in underground workplaces ranged from 27 to 4851 Bq/m³ with an overall mean value of 153 Bq/m³. As expected, radon distribution is not uniform throughout Italy: in several regions high radon annual averages have been found, confirming previous surveys.The analysis of data shows a high variability among regions and intra-region but low spread among rooms belonging to the same workplace.About 5% of underground workplaces displayed radon concentration exceeding 400 Bq/m³, and the 4.4% exceeds 500 Bq/m³, the national action level for the exposure to natural radioactivity in workplaces.     

Testing of a scintillator and fibre optic based radiation sensor

We describe the optimisation of RadLine^®; a small, real time, remotely operated radiation detector, which consists of an inorganic scintillation crystal coupled to a fibre optic cable transporting produced photons to a CCD camera some distance away. RadLine^® is tested in a beta and gamma narrow radiation field of 2.4 GBq, from a Caesium-137 (662 KeV) source, at doses rates between 0.125 mSvhr⁻¹ and 10 mSvhr⁻¹. Our results establish that the lower limit of the device corresponds to a dose rate of 0.2 mSvhr⁻¹, constrained by the signal to noise ratio of the instrument. We also demonstrate the process of characterising the RadLine^® for utilisation underwater due to its partial electrical inactiveness; and to consider how the instrument might perform in aquatic environments and ultimately in a First Generation Magnox Storage Ponds (FGMSP). The RadLine^® brings a marked difference to actual underwater radiation monitoring devices such as; HPGe, CZT and GM detectors, which not only incorporate the whole electronics within and are more bulky, only perform over a short range. The RadLine^®’s design offers signification value for intermediate (>100 m) and long range detection.     

Measurements of the size distribution of unattached radon progeny by using the imaging plate

The size distribution of unattached radon progeny is an important parameter for an accurate estimation of the internal dose of radon exposure. In this study, a new measuring system was developed to evaluate the size distribution of unattached radon progeny in air. In the system, airborne radon progeny were collected with a newly designed graded screen array (GSA), the activity concentrations were measured by using the imaging plate technique, and the size distribution of unattached fraction was retrieved by using an iterative nonlinear algorithm. The simulation results indicated that the collection characteristics of the new GSA system were well agreed with other systems. Test experiments showed that the activity-weighted median diameters (AMD) for unattached ²¹⁸Po, ²¹⁴Pb and ²¹⁴Bi were 0.89 ± 0.11 nm, 0.96 ± 0.13 nm and 1.01 ± 0.25 nm in a particle-free radon chamber, and the distribution changed with different concentrations of particles. As multiple measurements can be simultaneously carried out with a single IP, the new technique is considered as an optional and useful way to measure the size distribution measurement of unattached radon progeny.     

Exposure to indoor radon and natural gamma radiation in public workplaces in north-western Greece

Measurements of indoor radon levels and gamma dose rates were performed in 42 workplaces in Ioannina, north-western Greece. Radon concentrations followed a log-normal distribution with an arithmetic mean of 95 ± 51 Bq m^?3. In all cases, radon levels were below 400 Bq m^?3, which is the action level implemented by the Greek Regulation for Radiation Protection, in accordance with the European Commission recommendation. Comparing summer and winter measurements, no statistically significant seasonal variation was established. However, radon concentrations measured in basement and ground floor workplaces were significantly higher (p < 0.01) than those measured in the first and upper floors. Annual effective dose rates from inhalation of radon and its decay products were estimated to be in the range from 0.13 to 1.36 mSv y^?1 with a mean value of 0.62 mSv y^?1. Indoor exposure to natural gamma radiation entailed an average effective dose rate of 0.13 mSv y^?1, of which approximately 62% was due to terrestrial and the rest due to cosmic sources. The reported data contribute to the assessment of radon distribution and dose estimate at the national level.     

Dosimetry measurements at the fast neutron therapy facility in Seattle

The fast neutron therapy facility at the University of Washington has been in routine clinical use for 25 years. 50.5 MeV protons produce neutrons in a beryllium target mounted on an isocentric gantry. Beam shaping is accomplished with a 40-leaf collimator. Dosimetry measurements for treatment planning and calibration are performed with tissue equivalent ion chambers. A layered phantom of alternating Solid Water^® and Plastic Water^® slabs has been developed for rapid dose verification measurements. The neutron field in the room has been used for radiation testing of electronic components.     

Indoor radon measurements in dwellings of four Saudi Arabian cities

An indoor radon survey of a total of 269 dwellings, with one dosimeter per house, distributed in four Saudi Arabian cities was carried out. The objective of this survey was to carry out indoor radon measurements of two cities in the Eastern Province, Khafji and Hafr Al-Batin and to compare this with two cities in the Western Province, Al-Madina and Taif. The survey provides additional information about indoor radon concentrations in Saudi Arabia. The results of the survey in these cities showed that the overall minimum, maximum and average radon concentration were 7,137 and 30 Bqm⁻³, respectively. The lowest average radon concentration (20 Bqm⁻³) was found in Hafr Al-Batin, while the highest average concentration was found in Khafji (40 Bqm⁻³).