External gamma-ray dose rate and radon concentration in indoor environments covered with Brazilian granites

Redistribution of radionuclides in wall material and its effects on the room dose rate

Here we investigate the annual effective dose rate obtained from gamma radiation emitted from radionuclides in construction materials in a model room with fixed dimensions. The dose rate is calculated on the whole room area at half the room height. We focus our analyses on a comparison of the annual effective dose rate between the room centre and the room average at half the room height and provide wall-wise quadratic index equations for both. We find that the annual effective dose rate based on the room average is larger than for the room centre due to increased annual effective dose rates for positions in the room closer to the walls. Furthermore, we evaluate the annual effective dose rate under a non-equal distribution of radionuclides in the three wall types (floor and ceiling, long walls, short walls). When considering the room average of the annual effective dose rate, our analysis indicates that it appears advantageous to use construction materials with a higher radionuclide activity concentration for floor and ceiling and the material with a lower radionuclide content for long and short walls, if there is a choice in the construction process.

Countrywide monitoring of absorbed dose rate in air due to outdoor natural gamma radiation in India

The Indian Environmental Radiation Monitoring Network continuously monitors, throughout India, the absorbed dose rate in air due to outdoor natural gamma radiation, by using Geiger-Mueller detector-based standalone environmental radiation monitors. The network consists of 546 monitors spread across 91 monitoring locations distributed all over the country. In this paper, the countrywide long-term monitoring results are summarised. The measured mean dose rate of the monitoring locations followed a log-normal distribution and ranged from 50 to 535 nGy.h-1 with a median value of 91 nGy.h-1. Due to outdoor natural gamma radiation, the average annual effective dose was estimated to be 0.11 mSv.y-1.

Natural radioactivity and radiological risk assessment due to building materials commonly used in Erbil city, Kurdistan region, Iraq

Radiometric monitoring of construction materials is required for estimating the interior and exterior exposure to ionizing radiation emitted by terrestrial radioactive elements in building materials. Using gamma-ray spectroscopy, the activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰ K in fifty-two samples from eighteen different building materials commonly used in Erbil city, Kurdistan region, Iraq, were evaluated to assess possible radioactive dangers to human health. The activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰ K ranged from 1 ± 0.1 (gypsum board) to 130 ± 11 (granite), 1.3 ± 0.2 (gypsum) to 66 ± 8 (ceramic sample), and 18.74 ± 4 (gypsum) to 1061.708 ± 40 (granite) with an average of 28 ± 5, 20.7 ± 4, and 340.8 ± 18 (average ± standard deviation), respectively. Radiological indicators (activity concentration index, alpha and gamma index, hazard indices, interior absorbed gamma dose rate and the corresponding yearly effective dosage rate, and excess lifetime cancer risk) were computed to assess the health risks associated with these building materials. Consideration was given to the indoor annual effective dosage for common construction materials, the radon surface expiration rate, and the indoor radon concentration. The mean values of activity concentration were then inputted into the RESRAD-BUILD computer software to calculate a resident's long-term radiation exposure. The dosages were measured over a range of 0 to 70 years. From 0 to 30 years, there was a significant change in dosages; however, from 30 to 70 years, the dosages were reasonably consistent. This research demonstrates that granite samples are not safe for dwellings with poor ventilation (especially those without windows). In general, other investigated construction materials in the buildings are deemed safe for the population, since the computed values for these parameters fall within the well-being restrictions or criterion values.

WINDCATCHER VENTILATION COMPUTATION AND INDOOR 222RN CONCENTRATION IN TRADITIONAL ADOBE HOUSES

Radon-based radiation is a significant issue that can affect resident health as a contributory source of natural radiation from soil construction materials. This study investigates the effect of windcatchers on radon activity concentrations and radon exhalation rate from the soil surface in traditional adobe houses of Yazd, Iran. Radon concentrations were measured by passive detectors in 16 adobe houses. Computational fluid dynamics simulations were performed for different wind speed to calculate ventilation rate. The concentrations of 222Rn were in the ranges of 22 ± 1-117 ± 8 Bq m-3 with an average value of 50 ± 3 Bq m-3. The radon exhalation rates values were in the range of 8.3 ± 0.1 to 47.2 ± 0.5 Bq m-2 h-1. Radon concentration results in only one dwelling site were higher than the level recommended by the World Health Organization. The annual radon inhalation dose was found in seven sites higher than the worldwide average.

Health Hazards Assessment and Geochemistry of ElSibai-Abu ElTiyur Granites, Central Eastern Desert, Egypt

In this paper, a thorough radio- and chem-ecological evaluation of ElSibai-Abu ElTiyur granites located within Egypt’s crystalline basement rocks was conducted for risk and dose assessments. Twenty granitic samples from the study area’s various lithological units were analyzed using high-resolution γ-ray spectrometry to determine the natural radioisotopes (U-238, Th-232, and K-40) concentrations. The average concentrations of U-238, Th-232, and K-40 were 38.72, 38.23, and 860.71 Bq/kg, respectively, exceeding the GAV (global average value) documented by UNSCEAR (Scientific Committee on the Effects of Atomic Radiation, Vienna, Austria). The radiological parameters and indices judging the usage of ElSibai-Abu ElTiyur granites in homes were computed. The obtained results showed that ElSibai-Abu ElTiyur granites are safe to be used by inhabitants as superficial building materials, as per the globally accepted values and the recommended safety limits approved by UNSEAR, WHO (World Health Organization, Geneva, Switzerland), ICRP (International Commission on Radiological Protection, Ottawa, ON, Canada), and EC (European Commission, Luxembourg). Further, the samples were subjected to ICP-MS (inductively coupled plasma mass spectrometry) analysis for quantifying radionuclide variations with chemical composition. Geochemically based on the ICP-MS results, the studied granites proved to be highly evolved A-type granites. They span the metaluminous to peralkaline fields. The REE patterns are characterized by the enrichment of the light rare earths (LREE) over the heavy ones (HREE) where (La/Yb)n = 5.2, (Gd/Yb)n = 1.63 with pronounced negative Eu-anomalies (Eu/Eu*)n = 0.49. The albite granite exhibits the highest concentrations of Ga, Nb, Ta, U, and Y, and REE (Gd, Dy, Ho, Yb) than the Na-metasomatic granites. Finally, the obtained data serve as a valuable future database for finding out the compatibility of the geochemical data with the natural radioactivity levels of granites.

The possibility of the phosphogypsum use in the production of brick: Radiological and structural characterization

In this paper, phosphogypsum (PG) with the content of ²²⁶Ra of about 500 Bq kg^-1 was used as a clay additive in mass ratios of (0-40) % and its influence on the radiological and mineralogical characteristics of the obtained brick samples was monitored. After sintering the samples at 1000 ℃, the formation of the mineral phase gehlenite was observed, and its share increased with the share of PG in the samples. The Monte Carlo method was used to determine the gamma dose rates, and consequently annual effective dose, for a standard room, with dimensions 4 × 5 × 2.8 m, whose walls were built of brick with PG. The obtained values were in the range (0.22-0.35) mSv y^-1. In addition, the active device RAD7 was used to determine the radon surface exhalation rates from the samples, which were found to be in the range (63-150) mBq m^-2 h^-1. The estimated indoor radon concentrations were found to be drastically lower than 100 Bq m^-3, leading to low radon inhalation doses. However, estimated annual effective doses from external gamma exposure were found not to be insignificant.

Estimation of Natural Radionuclides’ Concentration of the Plutonic Rocks in the Sakarya Zone, Turkey Using Multivariate Statistical Methods

The study aimed to determine the natural radioactivity levels of 226Ra, 232Th, and 40K by the Gamma-Ray spectrometry method, and radiological hazard parameters of the plutonic rocks in the Western and Central Sakarya Zone and to analyze the data using multivariate statistical methods. The average radiological values of samples were determined as 40K (1295.3 Bq kg−1) > 232Th (132.1 Bq kg−1) > 226Ra (119.7 Bq kg−1). According to the skewness values of the distributions of the examined radionuclides, 226Ra (2.1) and 232Th (0.7) seemed to be positively right-skewed while 40K (−0.2) had a negatively right-skewed histogram. On the other hand, the following kurtosis values were calculated for the distributions: 226Ra (5.8 > 3), 232Th (−0.7), and 40K (−0.8). Kolmogorov–Smirnov and Shapiro–Wilk tests were applied to the data to test their normality. Therefore, Spearman’s correlation coefficient method was performed. The radionuclides of 226Ra and 232Th were found to have a positive correlation with radiological hazard parameters of the samples. 2 (two)-related factors identified, and the cumulative value was calculated to be 98.7% on the basis of the Scree Plot. According to the hierarchical cluster analysis, the samples that are grouped with those from Camlik region are prominent. The average radioactivity values of Camlik, Sogukpinar, Karacabey, and Sogut (except for 232Th) regions were detected to be higher than the world averages while the value of 40K was also found to be higher than the average values of various countries in the world.

Estimation of absorbed gamma dose rate from granite by Monte Carlo simulation approach

Apart from the continuous exposure of humans to background ionising radiation, an increased level of radiation may also originate from the use of building materials with an enhanced level of radioactivity. Thus, it is necessary to examine the content of radionuclides present in building materials, as well as the corresponding dose which may be received by residents from these materials. In this paper, particular attention was dedicated to finding the absorbed dose rate and annual effective dose caused by the presence of naturally occurring radioisotopes ²²⁶Ra, ²³²Th, and ⁴⁰K in granite, a widely used building material, by means of Monte Carlo simulations. In addition, the obtained dose rate simulation results were compared with values estimated from commonly used simple equations, relating to the dose rate emitted by granite plates, covering the interior of a standard room. In the simulation, a room was constructed with standard dimensions (4 m × 5 m × 2.8 m), and with floor and walls covered with 3 cm thick granite. A water cylinder (approximate mass 65 kg) was positioned in the center of the room, representing a human body. The emission of the most intense gamma rays from ²²⁶Ra and ²³²Th progenies, as well as from ⁴⁰K, emanating from the granite matrix, was simulated. The number of generated photons in each simulation (typically it was an order of magnitude of ~10⁶) precisely represented actual activity concentrations of ²²⁶Ra, ²³²Th, and ⁴⁰K in granite samples. All processes playing a role in the interactions of gamma photons with the granite matrix itself, the outer concrete shell, the air within the room, and the water cylinder, were taken into account by GEANT4 simulation software, after which the spectra of deposited energy inside of the water cylinder were obtained. Based on the deposited energy, the absorbed dose rate and annual effective dose were calculated for 6 analysed granite samples, each with different ²²⁶Ra, ²³²Th, and ⁴⁰K contents. Furthermore, the effect of the position of the water cylinder in the simulated room on the absorbed dose rate was considered, as well as the distribution of the deposited energy within the water cylinder. The absorbed dose rates, and consequently annual effective dose, obtained in the simulations were found to be 30%-40% higher than the values obtained from using a standard formula.

Measurement of the Background Gamma Dose Rates in Houston, Texas: A Descriptive Summary of an Undergraduate Research Mentored Project Performed by Students Underrepresented in the Health Physics Profession

Natural background radiations include cosmic, terrestrial, and medical sources. Cosmic radiation is mostly shielded by the magnetic field of the Earth; however, those that penetrate can produce nuclear interactions within the Earth's atmosphere yielding cosmic ray showers. Terrestrial and medical sources of radioactivity are typically identified through radionuclide-specific decay signatures. Medical sources of radiation mainly result from diagnostic x rays, which attenuate into the environment. These x rays also contribute slightly to background radiation. The purpose of this study was to have students involved with the Texas Southern University (TSU) health physics program measure and report background gamma dose rates in Houston, Texas, using the Canberra InSpector 1000 Digital Hand-Held Multichannel Analyzer. The results were compared with the average gamma dose rate on Earth. Of note, TSU is one of the largest historically black colleges and universities (HBCUs) in the nation and currently boasts the only undergraduate health physics program in Houston. Targeted locations were selected within the I-610 loop of Houston covering an area of approximately 100 km. Measurements were performed at nine locations and verified by GPS latitude and longitude coordinates. The dose rate was measured over a 100 m area at each location, while spectral analysis was simultaneously performed for natural gamma-emitters. Our results suggest the dose rate averaged over all geographical locations in this study was 0.114 ± 0.001 μSv h and thus, consistent with most literature. The only radionuclide identified in the spectra in all measurements was K due to the limited energy resolution of the InSpector 1000.

THE SCREENING INDOOR RADON AND PRELIMINARY STUDY OF INDOOR THORON CONCENTRATION LEVELS IN KUWAIT

Indoor measurements of radon and thoron in Kuwait were conducted during the years 2015 and 2016. In this study, 65 dwellings were selected for the long-term radon-thoron survey using passive nuclear track monitors. The monitors (at least one) were used at various locations in the dwellings for 83-306 days. Some measurements were also repeated at the same locations in different seasons. This current study is a preliminary thoron survey with relatively small sample size. The results showed that the range of thoron concentration was from below the lower limit of detection to 35 Bq m-3, whereas the range of radon concentration was within 10-202 Bq m-3. Furthermore, 22% of the radon results exceeded the WHO radon reference level of 100 Bq m-3. The analysis of variance showed a correlation between indoor radon concentration and the season. However, the thoron measurements were rather limited and the values were low. In addition, the relationship was investigated between radon and thoron concentrations involving the floor levels and the type of ventilation systems used.

Natural radioactivity in granites and gneisses of the Opava Mountains (Poland): a comparison between laboratory and in situ measurements

The natural radioactivities of five characteristic igneous rocks of the eastern foreland of the Opava Mountains (Eastern Sudetes, Poland), obtained in the laboratory and under in situ conditions, are presented. The activity concentrations of ²³²Th, ²³⁸U, and ⁴⁰K were measured using an HPGe gamma-ray spectrometry system. The ranges of the activity concentrations of ²³²Th were 7–71 Bq kg⁻¹ in the laboratory and 6–68 Bq kg⁻¹ for the in situ measurements. For ²³⁸U, the ranges of the activity concentrations were 5–52 Bq kg⁻¹ in the laboratory and 9–48 Bq kg⁻¹ for the in situ measurements, and for ⁴⁰K, the ranges were 520–1560 Bq kg⁻¹ in the laboratory and 537–1700 Bq kg⁻¹ for the in situ measurements. These determined activity concentrations were compared with the average activity concentrations of the radionuclides in similar types of rocks and with data from the Sudetes available in the literature. No significant differences were found between the in situ and laboratory measurements.

Assessement of doses to members of the public arising from the use of ornamental rocks in residences

The main pathways to human exposure associated with naturally occurring radionuclides in ornamental rocks are external irradiation and the inhalation of radon. Usually, external doses and risks are assessed by using generic approaches in which the specific properties and use of the material are not considered. Moreover, limited information on radon inhalation dose due to the use of rock is available. The radionuclide concentrations in 180 rock samples reached a wide range of values: for ²²⁸Ra from  <2 to 530 Bq kg^-1, for ²²⁶Ra between  <5 and 600 Bq kg^-1and for ⁴⁰K varied between 190 and 2797 Bq kg^-1. Considering the rock properties, mathematical models, a residential scenario and radionuclide concentrations in the rocks, ²²²Rn concentrations and inhalation and external doses were estimated to range from 0.1 to 13 Bq m^-3, from 0.01 and 0.26 mSv yr^-1 and from 0.01 and 0.61 mSv yr^-1, respectively. The ventilation and the emanation rates are key parameters for the Rn dose, whereas the location of the receptor significantly affects the external dose. The overestimations of doses and risks by the generic approaches highlight the necessity of considering the properties and use of the materials for those estimations.

Indoor Gamma Dose Rates In Kuwait Using Handheld Gamma-ray Spectrometer

A survey of indoor gamma dose rates was carried out in Kuwait using a NaI dosimeter/spectrometer. The measurements started from May 2013 until April 2015 and covered different locations within 200 dwellings: 158 halls, 26 rooms, 17 basements, and 43 kitchens (total of 244 locations). Alongside the dose rate measurements, gamma-ray spectra were also acquired to evaluate the relative contributions of K, Bi, and Tl and check the presence of Cs. The results show that the dose rates for all locations varied from 39.3 to 103.3 nSv h with a mean of 70.6 nSv h, indicating that the indoor dose rates are low and within the normal range.

Assessment of radiological hazard of commercial granites from Extremadura (Spain)

The term "commercial granite" comprises different natural stones with different mineralogical components. In Extremadura, western Spain, "commercial granites" can be classified in three types: granite s.s. (sensus stricti), granodiorite, and diorite. The content of naturally occurring radionuclides depended of the mineralogy. Thus, the (40)K content increased as the relative content of alkaline feldspar increased but decreased as the plagioclase content increased. The radioactive content decreased in the following order: granite s.s. > granodiorite > diorite. In this work, the radiological hazard of these granites as building material was analyzed in terms of external irradiation and radon exposure. External irradiation was estimated based on the "I" index, ranged between 0.073 and 1.36. Therefore, these granites can be use as superficial building materials with no restriction. Radon exposure was estimated using the surface exhalation rates in polished granites. The exhalation rate in granites depends of their superficial finishes (different roughness). For distinct mechanical finishes of granite (polish, diamond sawed, bush-hammered and flamed), the surface exhalation rate increased with the roughness of the finishes. Thermal finish presented the highest exhalation rate, because the high temperatures applied to the granite may increase the number of fissures within it. The exhalation rates in polished granites varied from 0.013 to 10.4 Bq m(-2) h(-1).

Using (222)Rn as a tracer of geodynamical processes in underground environments

Radon levels in two old mines in San Luis, Argentina, were measured and analyzed, with the aim to assess the potential use of this radioactive noble gas as a tracer of geological processes in underground environments. La Carolina gold mine and Los Cóndores tungsten mine are today used as tourism mines. CR-39 nuclear track detectors were used for this purpose. Measurements were performed during both winter and summer seasons. The findings show that in these environments, significant radon concentrations are subject to large seasonal fluctuations, due to the strong dependence on natural ventilation with the outside temperature variations. For both mines, higher concentration values of (222)Rn were observed in summer than in winter; with an extreme ratio of 2.5 times between summer and winter seasons for Los Cóndores mine. The pattern of radon transport inside La Carolina mine revealed, contrary to what was believed, that this mine behaves as a system with two entrances located at different levels. However, this feature can only be observed in the winter season, when there is a marked difference between the inside and outside temperatures of the mine. In the case of Los Cóndores mine, the radon concentration pattern distribution is principally established by air current due to chimney-effect in summer and winter seasons. In both cases, the analyses of radon pattern distribution appear as a good method to trace air currents, and then localize unknown ducts, fissures or secondary tunnels in subterranean environments.

Natural radioactivity, radon exhalation rates and indoor radon concentration of some granite samples used as construction material in Turkey

It is very important to determine the levels of the natural radioactivity in construction materials and radon exhalation rate from these materials for assessing potential exposure risks for the residents. The present study deals with 22 different granite samples employed as decoration stones in constructions in Turkey. The natural radioactivity in granite samples was measured by gamma-ray spectrometry with an HPGe detector. The activity concentrations of (226)Ra, (232)Th and (40)K were found to be in the range of 10-187, 16-354 and 104-1630 Bq kg(-1), respectively. The radon surface exhalation rate and the radon mass exhalation rate estimated from the measured values of (226)Ra content and material properties varied from 1.3 to 24.8 Bq m(-2) h(-1) with a mean of 10.5±1.5 Bq m(-2) h(-1) and 0.03-0.64 Bq kg(-1) h(-1) with a mean of 0.27±0.04 Bq kg(-1) h(-1), respectively. Radon concentrations in the room caused from granite samples estimated using a mass balance equation varied from 23 to 461 Bq m(-3) with a mean of 196±27 Bq m(-3). Also the gamma index (Iγ), external indoor annual effective dose (Eγ) and annual effective dose due to the indoor radon exposure (ERn) were estimated as the average value of 1.1±0.1, 0.16±0.02 mSv and 5.0±0.7 mSv, respectively, for the granite samples.

Natural radioactivity and radiation index of the major plutonic bodies in Greece

The natural radioactivity of the major plutonic bodies in Greece, as well as the assessment of any potential health hazard due to their usage as decorative building materials is studied. One hundred and twenty one samples from every major plutonic body in Greece, including various rock-types from gabbro to granite, have been measured for their natural radioactivity using γ-spectrometry methodology. According to the experimental results, the natural radioactivity levels were ranged up to 315 Bq kg(-1) for (226)Ra, up to 376 Bq kg(-1) for (232)Th and up to 1632 Bq kg(-1) for (40)K, with arithmetic mean values and standard deviations of 74 (±51), 85 (±54) and 881 (±331) Bq kg(-1) respectively, which are below the international representative mean values for granite stones. The excess on the effective dose received annually indoors due to granite tiles usage is estimated considering a standard room model where granite tiles with 1.5 cm in thickness cover only the floor of the room. The increment on the external γ-radiation effective dose rate shows a Gaussian distribution well dispersed below 0.3 mSv y(-1), presenting a mean value of 0.14 (±0.06) mSv y(-1). In case of the internal α-radiation a log-normal distribution is appeared scattering below 0.5 mSv y(-1) with a mean value 0.19 (±0.13) mSv y(-1), for a well-ventilated living environment. In case of a poor-ventilated room the increment on internal effective dose rate is estimated with a mean value 0.27 (±0.19) mSv y(-1) scattering below 0.8 mSv y(-1). The majority of the samples increase the external as well as the internal dose less than 30% of the maximum permitted limit of the effective dose rate. Therefore, at least from radiological point of view, the plutonic rocks of Greece could be safely used as decorative building materials.

Calculation of gamma radiation dose rate and radon concentration due to granites used as building materials in Iran

Natural radioactivity concentrations in granite building materials that are commonly used in Iran have been surveyed by using a gamma-ray spectrometry system, using a high-purity germanium detector. Health hazards from gamma radiation doses due to granite and radon concentration have been calculated. The dose rate of exposure from granite building materials on humans is obtained as a result of an external exposure from gamma-emitting radionuclides in the granites. Another mode of exposure is from the inhalation of the decay products of (222)Ra and (220)Ra. The average concentrations of (232)Th, (226)Ra and (40)K were in the ranges of 6.5-172.2, 3.8-94.2 and 556.9-1539.2 Bq kg(-1), respectively. The radon exhalation rates have also been studied and values were in the range of 0.32 ± 0.01 to 7.86 ± 1.65 Bq m(-2) h(-1). For two models of standard living rooms (5.0 m × 4.0 m area; 2.8 m), the radon concentration (Ci) and the absorbed dose (D) rates were calculated and the results were found to be 10.64-29.32 Bq m(-3), 3.84-68.02 nGy h(-1) and 0.02-0.33 mSv y(-1) for Model 1, 10.07-15.38 Bq m(-3) and 2.29-39.99 nGy h(-1) for Model 2, respectively. According to our estimations, mechanical ventilation systems (λν = 0.5 h(-1)) in a room all granite samples would produce radon concentration <100 Bq m(-3).

Radioactivity and gamma-dose rates observed at the Morungaba granites, Southeastern Brazil

A ground gamma-ray survey was conducted over part of a large granitic body located near the city of Campinas, eastern São Paulo State, Brazil. The dominant rock types are K-feldspar porphyries-rich granites, porphyritic biotite and hornblend-bearing granites, fine to medium-grained monzogranites and medium to gross grained, biotite and muscovite-bearing monzogranites. The radioactive element distribution reflects local geology, in part re-worked by weathering, and the most radioactive rocks are the K-feldspar-rich granites. The rate of the absorbed dose by the air reflects the integrated effects of the radioactive elements distribution. Most of the observed values vary between 67 and 130 nGy h(-1) and with localised spots with the absorbed dose rate values up to 193 nGy h(-1) and low values of ∼25 nGy h(-1). The mean air absorbed dose rate for the studied area is 77 nGy h(-1).