Assessment of the natural radioactivity using two techniques for the measurement of radionuclide concentration in building materials used in Japan

Natural radionuclides and radiological risk assessment in the stream and river sediments of a high background natural radiation area Kanyakumari, India

The Kanyakumari coast is known to be a high background natural radiation area due to the placer deposits of heavy minerals such as ilmenite, monazite, and rutile. The Kanyakumari river sediments that could be the source of the elevated amounts of natural radionuclides in the coastal sands have been studied in this paper. The activity concentrations of primordial radionuclides 226Ra, 232Th, and 40K were determined using high-purity germanium (HPGe) gamma-ray spectrometry. The mean activity concentrations of 226Ra, 232Th, and 40K were found to be 75 Bq kg-1, 565 Bq kg-1, and 360 Bq kg-1, respectively. The mean absorbed dose rate was 395 nGy h-1. Radiological hazard parameters were studied and compared with the world average values. The contribution of 232Th to the total dose rate was found to be higher than that of the two other radionuclides. The high mean ratio of 232Th/226Ra suggested an enrichment of 232Th and the occurrence of 226Ra leaching due to an oxidizing environment. Principal component analysis (PCA) was carried out for the radionuclides in order to discriminate the source of the sediments. This study provides new insights into the distribution of natural radionuclides in sediments of rivers and streams.

Distribution of natural radionuclides in NORM samples from North Abu Rusheid area, Egypt

The North Abu Rusheid area in Egypt is a well-known high background natural radiation area (HBNRA) due to the existence of naturally occurring radioactive materials (NORMs) in mylonitic rocks. In this study, 27 rock samples were selected for dose estimation studies. ²³⁸U and ²³²Th were measured using inductively coupled plasma mass spectrometry (ICP-MS) and ⁴⁰K was measured using sodium iodide (thallium) gamma-ray spectroscopy. The ranges of activity concentrations (Bq/kg) of ²³⁸U, ²³²Th and ⁴⁰K in the samples varied from 270 ± 2 to 2120 ± 29, 350 ± 2 to 1840 ± 27 and 20 ± 2 to 1390 ± 35 with mean values of 980 ± 349, 770 ± 351, and 640 ± 402 Bq/kg, respectively. The radiological hazard parameters were estimated from activity concentrations of ²³⁸U, ²³²Th and ⁴⁰K and compared to United Nations Scientific Committee on the Effects of Atomic Radiation (UNSCEAR) values. The present study revealed that the hazard parameters were several times higher than the worldwide averages. The U/Th concentration ratio ranged from 0.7 to 3 and could be attributed to the presence of kasolite, uranothorite, zircon, and columbite in mylonitic rocks. From the radiological protection viewpoint, it is necessary to monitor natural radionuclides in these rocks prior to their use in residential and commercial construction materials.

Advances in the management of radioactive wastes and radionuclide contamination in environmental compartments: a review

Several anthropogenic activities produce radioactive materials into the environment. According to reports, exposure to high concentrations of radioactive elements such as potassium (⁴⁰K), uranium (²³⁸U and ²³⁵U), and thorium (²³²Th) poses serious health concerns. The scarcity of reviews addressing the occurrence/sources, distribution, and remedial solutions of radioactive contamination in the ecosystems has fueled data collection for this bibliometric survey. In rivers and potable water, reports show that several parts of Europe and Asia have recorded radionuclide concentrations much higher than the permissible level of 1 Bq/L. According to various investigations, activity concentrations of gamma-emitting radioactive elements discovered in soils are higher than the global average crustal values, especially around mining activities. Adsorption technique is the most prevalent remedial method for decontaminating radiochemically polluted sites. However, there is a need to investigate integrated approaches/combination techniques. Although complete radionuclide decontamination utilizing the various technologies is feasible, future research should focus on cost-effectiveness, waste minimization, sustainability, and rapid radionuclide decontamination. Radioactive materials can be harnessed as fuel for nuclear power generation to meet worldwide energy demand. However, proper infrastructure must be put in place to prevent catastrophic disasters.

RADIOLOGICAL IMPACT OF USING DECORATIVE GRANITE AS AN ATTENUATOR OF IONIZING RADIATION

Granite is a widely available rock, which can be used as a shielding material, for bulk in the form of the aggregate in concrete. It has the weakness that it is more radioactive than many other rocks, which can be used in concrete. This paper looks at its properties as a shielding material and the activity level. Thus, the concentrations of 226Ra, 232Th and 40K, in granite were measured using a high pure germanium detector (HPGe). They were ranged from (15 ± 4 to 49 ± 5) Bq kg-1 for 226Ra, (22 ± 4 to 78 ± 4 Bq kg-1) for 232Th and (791 ± 13 to 1231 ± 15 Bq kg-1) for 40K. Radiological indices of radium equivalent concentration (Raeq), external (Hex), internal (Hin) and annual effective dose were less than worldwide recommended limits. The results emphasized, the granite samples had no radiation hazard. Nevertheless, the mass attenuation coefficients of granite samples were measured for the gamma rays of energy range 122-1408 keV. The mass attenuation coefficients of the studied granite samples were ranged from 0.05 to 0.15 cm2 g-1. In addition, the average the half-value layer of granite was varied from 1.8 cm for 122 keV to 5.2 cm for 1408 keV. The results are that the attenuation characteristics are typical and match the values given by NIST for 'concrete' and that the activity levels of the samples examined are acceptable. Thus the granite may be used as an attenuator for ionizing radiation.

COMPARISON OF GAMMA ABSORBED DOSE RATES IN THE AIR MEASURED WITH A PORTABLE SURVEY METER AND THE SOIL RADIOACTIVITY MEASUREMENTS

To compare the measurement results of a portable survey meter with a soil-based dose rate assessment method, the gamma absorbed dose rates in the air were measured at 27 sites. The soil-based gamma absorbed dose rates in the air were calculated using established conversion factors and the activity concentrations of 226Ra, 232Th and 40K of the soil at the sites. The gamma absorbed dose rate averages of the portable survey meter, and computing from the activity concentrations in the soil were 65.8 ± 4.26 and 64.8 ± 3.68 nGy⋅h-1, respectively. A significant positive correlation was found in the comparison between the evaluated gamma absorbed dose rates from soil radioactivity and in the air. Conversion factors based on the local soils converting to the absorbed dose rate were computed from the portable survey meter data and the soil activity concentrations, and it was compared with others.

Correlation between Ground 222Rn and 226Ra and Long-Term Risk Assessment at the at the Bauxite Bearing Area of Fongo-Tongo, Western Cameroon

The aim of the current work was to study natural radioactivity in soil and the correlation between 222Rn and 226Ra in the ground and to assess the onsite and indoor long-term excess cancer risk at the bauxite bearing area of Fongo-Tongo in Western Cameroon. 222Rn was measured in the ground at a depth of one meter, using Markus 10 detector. 226Ra, 232Th, and 40K activity concentrations were measured in soil by two techniques, in situ and laboratory gamma spectrometry. The mean values of 222Rn concentrations in the ground were 69 ± 18 kBqm−3 for Fongo-Tongo and 82 ± 34 kBq m−3 for the locality of Dschang, respectively. The mean values of 226Ra, 232Th, and 40K activity concentrations obtained with in situ gamma spectrometry were 129 ± 22, 205 ± 61, and 224 ± 39 Bq kg−1 for 226Ra, 232Th, and 40K, respectively, and those obtained by laboratory gamma spectrometry were 129 ± 23, 184 ± 54, and 237 ± 44 Bq kg−1, respectively. A strong correlation between 222Rn and 226Ra activity concentrations determined by in situ and laboratory measurements (R2 = 0.86 and 0.88, respectively) was found. In addition, it is shown that the total excess cancer risk has a maximum value of 8.6 × 10−3 at T = 0 year and decreases progressively in the long term. It is also shown that 226Ra makes a major contribution, i.e., above 70%, to the total excess cancer risk.

A FEASIBILITY TEST FOR QUICK RADON RISK ASSESSMENT BY MEASURING AN IN SITU RADIATION DOSE RATE

Radon concentration was estimated using an accumulation chamber equipped with AlphaGUARD radon monitor. It varies from 12.6 ± 1.20 to 363 ± 19.3 Bq m-3 with a mean value of 180 ± 11.2 Bq m-3. A good correlation between radium content and radon concentrations was obtained of R = 0.754, which suggests that radium is the main reason of releasing radon to the atmosphere. Radon emanation coefficient and exhalation rate were also calculated. Furthermore, the radiation dose rate was measured with a high-pressure ionization chamber detector. The radiation dose rate was strongly correlated with the radon concentration and exhalation rate of R = 0.85 and 0.63. The obtained results support our idea that the radiation dose rate can be a good indicator to the radon level in the atmosphere. In addition, the dependence of radon concentration on the water content was discussed.

ASSESSMENT OF RADIOLOGICAL HAZARDS OF USING PETROLEUM RAW MATERIALS AND THEIR WASTE

Activity concentrations of 238U, 232Th and 40K in raw and waste petroleum materials (Egypt and Kuwait) were measured using gamma ray spectrometer. The average values of 226Ra, 232Th and 40K were 21.1 ± 3.2, 7.6 ± 1.3 and 88.4 ± 8.2 Bq kg-1 for Egyptian samples while for Kuwaiti samples, they were 25.2 ± 3.4, 6.1 ± 2.2 and 67.8 ± 6.4 Bq kg-1, respectively. All samples had activity less than the exemption level recommended by the International Atomic Energy Agency. Moreover, radiological indices of radium equivalent, external, internal, alpha and gamma indices and radiation dose as well were calculated and their values were lower than the recommended regulatory limits. Thus, radiation exposure to petroleum materials did not present a significant radiological hazard.

Comparative study of precise measurements of natural radionuclides and radiation dose using in-situ and laboratory γ-ray spectroscopy techniques

In this study, in-situ and laboratory γ-ray spectroscopy techniques were compared to evaluate the activity concentration of natural radionuclides in soil. The activity concentrations of 238U (226Ra), 232Th, and 40K in the soil in 11 sites were simultaneously measured with in-situ portable HPGe and the NaI(Tl) detectors. In parallel, 55 soil samples collected from these sites were analyzed with a laboratory γ-ray spectroscopy technique (HPGe). A strong correlation was observed between the in-situ and laboratory HPGe techniques with a linear correlation coefficient (R2) of 0.99 for 226Ra and 232Th and 0.975 for 40K, respectively. The in-situ HPGe technique shows a strong correlation with the NaI(Tl) detector. γ-Rays cps of 226Ra, 232Th, and 40K of the NaI (Tl) detector were then converted to specific activities (Bq kg-1 unit) in soil using the empirical formulas obtained in this study. The absorbed dose rate in air at 1 m height above ground due to these radionuclides was calculated using the Beck's formula and the results were compared with measured values obtained with an high pressure ionization chamber. The results of the calculated and measured dose rate show a strong correlation of R2 = 0.96. The reliability and precision of analytical spectroscopy techniques of radioactivity and radiation dose were confirmed in this work.

Radiological survey of the covered and uncovered drilling mud depository

In petroleum engineering, the produced drilling mud sometimes contains elevated amounts of natural radioactivity. In this study, a remediated Hungarian drilling mud depository was investigated from a radiological perspective. The depository was monitored before and after a clay layer was applied as covering. In this study, the ambient dose equivalent rate H*(10) of the depository has been measured by a Scintillator Probe (6150AD-b Dose Rate Meter). Outdoor radon concentration, radon concentration in soil gas, and in situ field radon exhalation measurements were carried out using a pulse-type ionization chamber (AlphaGUARD radon monitor). Soil gas permeability (k) measurements were carried out using the permeameter (RADON-JOK) in situ device. Geogenic radon potentials were calculated. The radionuclide content of the drilling mud and cover layer sample has been determined with an HPGe gamma-spectrometer. The gamma dose rate was estimated from the measured radionuclide concentrations and the results were compared with the measured ambient dose equivalent rate. Based on the measured results before and after covering, the ambient dose equivalent rates were 76 (67-85) nSv/h before and 86 (83-89) nSv/h after covering, radon exhalation was 9 (6-12) mBq/m²s before and 14 (5-28) mBq/m²s after covering, the outdoor radon concentrations were 11 (9-16) before and 13 (10-22) Bq/m³after covering and the soil gas radon concentrations were 6 (3-8) before and 24 (14-40) kBq/m³ after covering. Soil gas permeability measurements were 1E-11 (7E-12-1E-11) and 1E-12 (5E-13-1E-12) m² and the calculated geogenic radon potential values were 6 (3-8) and 12 (6-21) before and after the covering. The main radionuclide concentrations of the drilling mud were C_U-238 12 (10-15) Bq/kg, C_Ra-226 31 (18-40) Bq/kg, C_Th-232 35 (33-39) Bq/kg and C_K-40 502 (356-673) Bq/kg. The same radionuclide concentrations in the clay were C_U-238 31 (29-34) Bq/kg, C_Ra-226 45 (40-51) Bq/kg, C_Th-232 58 (55-60) Bq/kg and C_K-40 651 (620-671) Bq/kg. According to our results, the drilling mud depository exhibits no radiological risk from any radiological aspects (radon, radon exhalation, gamma dose, etc.); therefore, long term monitoring activity is not necessary from the radiological point of view.

Natural radioactivity in some building materials and assessment of the associated radiation hazards

The results of the specific activities of 232Th, 226Ra and 40K measured in samples of commonly used building materials in Bosnia and Herzegovina are presented. Measurements were performed by gamma-ray spectrometer with coaxial HPGe detector. The surface radon exhalation and mass exhalation rates for selected building materials were also measured. The determined values of specific activities were in range from 3.16±0.81 Bq kg−1 to 64.79±6.16 Bq kg−1 for 232Th, from 2.46±0.95 Bq kg−1 to 53.89 ±3.67 Bq kg−1 for 226Ra and from 28.44±7.28 Bq kg−1 to 557.30±93.38 Bq kg−1 for 40K. The radium equivalent activity, the activity concentration index, the external and internal hazard indices as well as the absorbed dose rate in indoor air and the corresponding annual effective dose, due to gamma-ray emission from the radioactive nuclides in the building material, were evaluated in order to assess the radiation hazards for people. The measured specific activities of the natural radioactive nuclides in all investigated building materials were compared with the published results for building materials from other European countries. It can be noted that the results from this study are similar to the data for building materials from neighbouring countries and for building materials used in the EU Member States. The radiological hazard parameters of the building materials were all within the recommended limits for safety use.

Effect of energy-efficient measures in building construction on indoor radon in Russia

The effect of implementation of energy-efficient measures in building construction was studied. Analysis includes study of indoor radon in energy-efficient buildings in Ekaterinburg, Russia, and results of radiation measurements in 83 regions of Russia conducted within the regional programmes. The forecast distribution of radon concentration in Ekaterinburg was built with regard to the city development programme. With Ekaterinburg taken as representative case, forecast distribution of radon concentration in Russia in 2030 was built. In comparison with 2000, average radon concentration increases by a factor of 1.42 in 2030 year; percentage above the reference level 300 Bq/m3 increases by a factor of 4 in 2030 year. It is necessary to perceive such an increase with all seriousness and to prepare appropriate measures for optimization of protection against indoor radon. Despite the high uncertainty, reconstructed distribution of radon concentration can be applied for justification of measures to be incorporated in the radon mitigation strategy.

Optimizing laboratory-based radon flux measurements for sediments

Radon flux via diffusion from sediments and other materials may be determined in the laboratory by circulating air through the sample and a radon detector in a closed loop. However, this approach is complicated by the necessity of having to determine the total air volume in the system and accounting for any small air leaks that can arise if using extended measurement periods. We designed a simple open-loop configuration that includes a measured mass of wet sediment and water inside a gas-tight reaction flask connected to a drying system and a radon-in-air analyzer. Ambient air flows through two charcoal columns before entering the reaction vessel to eliminate incoming radon. After traveling through the reaction flask, the air passes the drier and the radon analyzer and is then vented. After some time, the radon activity will reach a steady state depending upon the airflow rate. With this approach, the radon flux via diffusion is simply the product of the steady-state radon activity (Bq/m(3)) multiplied by the airflow rate (mL/min). We demonstrated that this setup could produce good results for materials that produce relatively high radon fluxes. We also show that a modified closed system approach, including radon removal of the incoming air by charcoal filtration in a bypass, can produce very good results including samples with very low emission rates.

Evaluation of radionuclide concentrations and associated radiological hazard indexes in building materials used in Egypt

Radionuclide concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in different types of building materials used in Egypt were measured using gamma-ray spectroscopy. The results showed relatively moderate radionuclide concentrations for all samples except granite, which showed extremely high concentrations of 78.75 ± 2.36, 2.82 ± 0.11 and 2.37 ± 0.07 kBq kg⁻¹ for ²²⁶Ra, ²³²Th and ⁴⁰K, respectively. The radiological hazard indexes of radium equivalent activity (Raeq), external hazard index (Hex) and internal hazard index (Hin), due to the presence of those radionuclides in the investigated building materials, were calculated. The released radon from the selected samples was measured using the AlphaGUARD radon monitor in order to use its value to calculate the radon emanation coefficient and the radon exhalation rate. The alpha equivalent dose (dose from indoor radon generated from building materials) was calculated using the measured values of the radium concentration and the radon emanation coefficient.

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.

Radioactivity measurement of primordial radionuclides in and dose evaluation from marble and glazed tiles used as covering building materials in Turkey

Measurements of the natural radioactivity arising from primordial radionuclides ((226)Ra, (232)Th and (40)K) in marble and glazed tile samples used covering building materials in Turkey were carried out by gamma-ray spectrometer with a high purity germanium detector. The mean activity concentrations of the (226)Ra, (232)Th and (40)K in marble and glazed tile samples were found as 8.2, 5.5 and 58.1 Bq kg(-1) and 81.2, 65.4 and 450.1 Bq kg(-1), respectively. The radiation doses received by occupants of buildings in which the sample marble and glazed tiles might be used are estimated using measured activity concentrations of constituent primordial radionuclides and dose conversion factors evaluated by the European Commission from models of tile use. Results obtained are presented for each radionuclide, analysed and compared with relevant national and international legislation, guidance and report, and with the results obtained from other studies. Results show that the use of such decorative building materials in the construction of domestic homes or workplaces in Turkey is unlikely to lead to any significant radiation exposure to the occupants.

Natural radioactivity in rocks of the Modane-Aussois region (SE France)

The activity concentrations of ⁴⁰K, ²³²Th, and ²³⁸U in the characteristic rocks of the Modane-Aussois region (Western Alps, France) were determined using an HPGe gamma-ray spectrometry system. The activity concentrations of ⁴⁰K varied from 18 Bqkg⁻¹ (limestone dolomite) to 392 Bqkg⁻¹ (calcschist), while those of ²³²Th varied from 0.7 Bqkg⁻¹ (limestone dolomite) to 18 Bqkg⁻¹ (calcschist). The activities associated with ²³⁸U ranged from 9 (quartzite) to 29 Bqkg⁻¹ (dolomite). In the investigated rock samples, concentrations of ²³⁸U (ppm) and ⁴⁰K (%) had a strong negative correlation.

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

Health hazard from natural radioactivity in Brazilian granites, covering the walls and floor in a typical dwelling room, was assessed by indirect methods to predict external gamma-ray dose rates and radon concentrations. The gamma-ray dose rate was estimated by a Monte Carlo simulation method and validated by in-situ measurements with a NaI spectrometer. Activity concentrations of (232)Th, (226)Ra, and (40)K in an extensive selection of Brazilian commercial granite samples measured by using gamma-ray spectrometry were found to be 4.5-450 Bq kg(-1), 4.9-160 Bq kg(-1) and 190-2029 Bq kg(-1), respectively. The maximum external gamma-ray dose rate from floor and walls covered with the Brazilian granites in the typical dwelling room (5.0 m × 4.0 m area, 2.8 m height) was found to be 120 nGy h(-1), which is comparable with the average worldwide exposure to external terrestrial radiation of 80 nGy h(-1) due to natural sources, proposed by United Nations Scientific Committee on the Effects of Atomic Radiation. Radon concentrations in the room were also estimated by a simple mass balance equation and exhalation rates calculated from the measured values of (226)Ra concentrations and the material properties. The results showed that the radon concentration in the room ventilated adequately (0.5 h(-1)) will be lower than 100 Bq m(-3), value recommended as a reference level by the World Health Organization.

A comparative study of thorium activity in NORM and high background radiation area

Several industrial processes are known to enrich naturally occurring radioactive materials (NORM). To assess such processes with respect to their radiological relevance, characteristic parameters describing this enrichment will lead to interesting information useful to UNSCEAR. In case of mineral treatment plants, the high temperatures used in smelting and refining processes lead to high concentrations of (238)U and (232)Th. Also due to thermal power combustion, concentration of U and Th in the fly ash increases manifold. NORM samples were collected from a Thailand mineral treatment plant and Philippine coal-fired thermal power plants for investigation. Some studies are initiated from a high background radiation area near Gopalpur of Orissa state in India. These NORM samples were analysed by gamma-ray spectrometry as well as inductively coupled plasma mass spectrometry. The radioactivity in case of Orissa soil samples is found to be mainly contributed from thorium. This study attempts to evaluate levels of thorium activity in NORM samples.