Natural radioactivity and external dose assessment of surface soils in Vietnam

In this study, natural radioactivity in surface soils of Vietnam and external dose assessment to human population, deduced from activities of (226)Ra, (232)Th and (40)K nuclides, were determined. From 528 soil samples collected in 63 provinces of Vietnam, including five centrally governed cities, the average activities were obtained and equal to 42.77 ± 18.15 Bq kg(-1) for (226)Ra, 59.84 ± 19.81 Bq kg(-1) for (232)Th and 411.93 ± 230.69 Bq kg(-1) for (40)K. The outdoor absorbed dose rates (OADRs) in air at 1 m above the ground level for 63 provinces were calculated, and their average value was 71.72 ± 24.72 nGy h(-1), with a range from 17.45 to 149.40 nGy h(-1). The population-weighted OADR of Vietnam was 66.70 nGy h(-1), which lies in the range of 18-93 nGy h(-1) found in the World. From the OADRs obtained, it was estimated that the outdoor annual effective dose and indoor annual effective dose to the population were 0.082 and 0.458 mSv, which are higher than the corresponding values 0.07 and 0.41 mSv, respectively, of the World. The radium equivalent activity Ra(eq) and the external hazard index H(ex) of surface soils of Vietnam are lower than the corresponding permissible limits of 370 Bq kg(-1) and 1, respectively. Therefore, soil from Vietnam is safe for the human population when it is used as a building material.     

Radioactivity of coals and ashes from Catalağzi coal-fired power plant in Turkey

The ?atala?z? coal-fired power plant (CFPP) is the Turkish CFPP that uses the hard coals produced in Zonguldak, located in the West Black Sea region of the country. Gamma-ray spectrometry was used to determine (226)Ra, (232)Th and (40)K contents in pulverised coal, bottom ash and fly ash samples. The natural radionuclide concentrations in pulverised coal ranged from 29 to 61 Bq kg(-1) for (226)Ra, from 32 to 55 Bq kg(-1) for (232)Th and from 229 to 414 Bq kg(-1) for (40)K. The fly ash fraction gave concentrations ranging from 80 to 98 Bq kg(-1) for (226)Ra, from 64 to 85 Bq kg(-1) for Th and from 754 to 992 Bq kg(-1) for (40)K, respectively. The enrichment factors from coal to fly ashes are 1.7, 2.24 and 2.6 for (232)Th, (226)Ra and (40)K, respectively. Therefore, it is advisable to monitor the environmental impact of the power plant.     

Measurement of natural radioactivity in beach sands from Rizhao bathing beach, China

The natural radioactivity of (226)Ra, (232)Th and (40)K was determined for beach sand samples collected from Rizhao bathing beach, China, using gamma ray spectrometry. The measured activity in beach sand ranges from 7.6 to 17.2, 7.8 to 25.1 and 883.4 to 1313.6 Bq kg(-1) for (226)Ra, (232)Th and (40)K with mean values of 12.0, 15.2 and 1079.2 Bq kg(-1), respectively. The activity concentrations of (226)Ra and (232)Th in beach sands are lower, while (40)K is higher than the world average. The radium equivalent activity in all beach sand samples is lower than the safe limit set in the OECD report (370 Bq kg(-1)). The values of the external hazard index are less than unity. The mean outdoor air absorbed dose rate is 59.8 nGy h(-1) and the corresponding outdoor effective dose rate is 0.073 mSv y(-1).     

Measurement of radioactivity in the soil of Bahawalpur division, Pakistan

Bahawalpur is the largest division of the Punjab province in Pakistan. It is larger than many countries of the world. Gamma activity from the naturally occurring radionuclides namely 226Ra, 232Th, the primordial radionuclide 40K and the artificial radionuclide 137Cs was measured in the soil of the Bahawalpur division using gamma spectrometry technique. The mean activity of 226Ra, 232Th, 40K and 137Cs were found to be 32.9 +/- 0.9, 53.6 +/- 1.4, 647.4 +/- 14.1 and 1.5 +/- 0.2 Bq kg(-1), respectively. The mean radium equivalent activity Raeq, external hazard index, internal hazard index and terrestrial absorbed dose rate for the area under study are 158.5 +/- 4.1 Bq kg(-1), 0.4, 0.5 and 77.32 nGy h(-1), respectively. The annual effective dose equivalent to the public was found to be 0.5 mSv.     

Natural radioactivity content of granite tiles used in Greece

Measurements of (226)Ra, (232)Th and (40)K activity concentrations in commercial granite tiles imported in Greece were performed using gamma-ray spectrometry. The activity concentration of (226)Ra, (232)Th and (40)K ranged from 1 to 434, 2 to 239 and 71 to 1576 Bq kg(-1), respectively. The calculated activity concentration index (I) values for all granite samples examined were found to be within the EC limit values for superficial and other materials with restricted use.     

Radioactivity level in Chinese building ceramic tile

The activity concentrations of (226)Ra, (232)Th and (40)K have been determined by gamma ray spectrometry. The concentrations of (226)Ra, (232)Th and (40)K range from 158.3 to 1087.6, 91.7 to 1218.4, and 473.8 to 1031.3 Bq kg(-1) for glaze, and from 63.5 to 131.4, 55.4 to 106.5, and 386.7 to 866.8 Bq kg(-1) for ceramic tile, respectively. The measured activity concentrations for these radionuclides were compared with the reported data of other countries and with the typical world values. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)) and internal hazard index (H(in)) associated with the radionuclides were calculated. The Ra(eq) values of all ceramic tiles are lower than the limit of 370 Bq kg(-1). The values of H(ex) and H(in) calculated according to the Chinese criterion for ceramic tiles are less than unity. The Ra(eq) value for the glaze of glazed tile collected from some areas are >370 Bq kg(-1).     

Study on radionuclides in granite quarries of Bangalore rural district, Karnataka, India

Studies on natural radiation levels and radionuclides were carried out extensively in the environment of granite quarries of Kanakapura, Ramanagara Taluks and Bidadi Hobli in Bangalore rural District and Bangalore city. The indoor and outdoor gamma exposure rate in air was measured using an environmental dosemeter, and it is converted into absorbed dose using suitable conversion factor. The activity concentrations of natural radionuclides in rock samples and also in soil samples were measured using an HPGe gamma-ray spectrometer. The results reveal that the activity concentrations of (226)Ra, (232)Th and (40)K in rocks are found to be vary from 32.2 to 163.6, 128.3 to 548.6 and 757.4 to 1418.4 Bq kg(-1), respectively, with corresponding arithmetic mean values of 93.2, 306.2 and 1074.4 Bq kg(-1). Activity concentrations of (226)Ra, (232)Th and (40)K in soil samples were found to vary from 32.4 to 55.2, 39.9 to 214.3 and 485.4 to 1150.2 Bq kg(-1), respectively, with corresponding arithmetic mean values of 40.7, 93.1 and 750.4 Bq kg(-1). The average activity levels of all these radionuclides are above the global average. This is consistent with the geological and geo-chemical significance of the rocks of the area under investigation. The results of these systematic investigations are discussed in detail and compared with the literature values represented for other environments.     

Natural radionuclides content and associated dose rates in fine-grained sediments from Patras-Rion sub-basins, Greece

The activity concentrations of the natural radionuclides (238)U, (226)Ra, (232)Th and (40)K were measured in soil samples collected from the Patras-Rion sub-basins (Southern Greece) and were found to be 28, 27, 30 and 483 Bq kg(-1), respectively. These values compare well with the average Greek and worldwide values for crustal soil and sedimentary rocks. The mean (226)Ra/(238)U activity ratio was close to 1, implying secular radioactive equilibrium in the uranium series. All soil samples have Ra(eq) values lower than the limit of 370 Bq kg(-1), indicating their safe use in brick production. The average annual terrestrial absorbed dose rate in air was 51±14 nGy h(-1), and the average annual effective dose 0.06±0.02 mSv y(-1), which is consistent with the average worldwide exposure to external terrestrial radiation outdoors (0.07 mSv y(-1)). Non-significant differences between soils with different age and depositional environments were found, which could be attributed to a common source of sediments.     

Measurement of natural radioactivity and assessment of associated radiation hazards in soil around Baoji second coal-fired thermal power plant, China

Activity concentrations of natural radionuclides (226)Ra, (232)Th and (40)K in soil around Baoji Second coal-fired thermal power plant of China were determined using gamma ray spectrometry. The mean activity concentrations of (226)Ra, (232)Th and (40)K in soil were found to be 40.3 ± 3.5, 59.6 ± 3.1 and 751.2 ± 12.4 Bq kg(-1), respectively, which are all higher than the corresponding average values in Shaanxi, Chinese and world soil. The radium equivalent activity (Ra(eq)), the air absorbed dose rate (D), the annual effective dose (E), the external hazard index (H(ex)) and internal hazard index (H(in)) were evaluated and compared with the internationally reported or reference values. All the soil samples have Ra(eq) lower than the limit of 370 Bq kg(-1) and H(ex) and H(in) less than unity. The overall mean outdoor terrestrial gamma air absorbed dose rate is ～86.6 ± 3.4 nGy h(-1) and the corresponding outdoor annual effective dose is 0.106 ± 0.004 mSv, which is higher than the worldwide average (0.07 mSv y(-1)) for outdoor's annual effective dose.     

Measurements of activity concentrations of naturally occurring radionuclides in soil samples from Punjab province of Pakistan and assessment of radiological hazards

The natural level of radioactivity in soil is one of the major causes of external gamma rays exposure. It was considered imperative to measure gamma-ray activity concentrations due to naturally occurring, potentially hazardous radionuclides from 232Th, 226Ra and 40K in soil samples from Punjab, the most populated province of Pakistan. The activity concentrations were measured in soil samples collected from all 34 district headquarters of Punjab province using a P-type coaxial high purity germanium (HPGe)-based gamma-ray spectrometer having a relative efficiency of 60%. The mean activity concentrations for 232Th, 226Ra and 40K were found to be 41 +/- 8, 35 +/- 7 and 615 +/- 143 Bq kg(-1), respectively in soil samples from all 34 district headquarters of Punjab. The mean values of radium equivalent index (Ra(eq)) and total annual external gamma radiation dose were found to be 141 +/- 27 Bq kg(-1)and 0.38 mSv, respectively. Since these estimated radiological impact assessment factors are lower than the recommended values there seems to be no potential radiological health hazard associated with the soils from the district headquarters in the Punjab province of Pakistan. Geological studies show that most of the soils in Punjab have developed on the extensive fluviatile deposits of five rivers and a stable ratio of natural activity concentrations is observed in soil samples of the areas under study.     

Radioactivity concentrations and dose assessment in surface soil samples from east and south of Marmara region, Turkey

The activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were measured in surface soil samples from East and South of Marmara region, Turkey. The physico-chemical parameters (organic matter, CaCO3 contents and pH-value) of the soil samples were determined in the samples collected from 100 sampling stations. The average activity concentrations of 137Cs, 40K, 232Th, 238U and 226Ra were found to be 27.46+/-21.84, 442.51+/-189.85, 26.63+/-15.90, 21.77+/-12.08 and 22.45+/-13.31 Bq kg(-1), respectively. The mean value of total annual external gamma radiation dose equivalent for the natural radionuclides was calculated to be 54.86 microSv. The current data were compared with those found in the other locations of Turkey and different countries.     

Environmental gamma radiation measurement in district Swat, Pakistan

External exposure to environmental gamma ray sources is an important component of exposure to the public. A survey was carried out to determine activity concentration levels and associated doses from (226)Ra, (232)Th, (40)K and (137)Cs by means of high-resolution gamma ray spectrometry in the Swat district, famous for tourism. The mean concentrations for (226)Ra, (232)Th and (40)K were found to be 50.4 +/- 0.7, 34.8 +/- 0.7 and 434.5 +/- 7.4 Bq kg(-1), respectively, in soil samples, which are slightly more than the world average values. However, (137)Cs was only found in the soil sample of Barikot with an activity concentration of 34 +/- 1.2 Bq kg(-1). Only (40)K was determined in vegetation samples with an average activity of 172.2 +/- 1.7 Bq kg(-1), whereas in water samples, all radionuclides were found below lower limits of detection. The radium equivalent activity in all soil samples is lower than the limit set in the Organisation for Economic Cooperation and Development report (370 Bq kg(-1)). The value of the external exposure dose has been determined from the content of these radionuclides in soil. The average terrestrial gamma air absorbed dose rate was observed to be 62.4 nGy h(-1), which yields an annual effective dose of 0.08 mSv. The average value of the annual effective dose lies close to the global range of outdoor radiation exposure given in United Nations Scientific Committee on the Effects of Atomic Radiation. However, the main component of the radiation dose to the population residing in the study area arises from cosmic ray due to high altitude.     

Assessment of the radiological hazards due to naturally occurring radionuclides in soil samples collected from the north western areas of Pakistan

(226)Ra, (232)Th and (40)K were measured in soil samples, these were collected from different localities of the North West Frontier Province and Federally Administered Tribal Areas, Pakistan. In order to measure the specific activities in these samples P-type coaxial high purity germanium based gamma-ray spectrometer was used. Average values of the measured activities of (226)Ra, (232)Th and (40)K were 26 +/- 11, 39 +/- 17 and 485 +/- 177 Bq kg(-1), respectively. Average radium equivalent activity was found to be 122 +/- 42 Bq kg(-1). External and internal hazard indices were also calculated and found to be 0.33 +/- 0.12 and 0.40 +/- 0.14, respectively. Average effective dose received due to gamma rays was 0.34 +/- 0.12 mSv y(-1). Measured natural radioactivity, hazard indices and effective doses received by the population were found within the recommended limits. The aim of this work was to make a baseline data of natural radioactive elements for the soil of the area and to assess it radiological significance if used as a building material for the construction of houses.     

Determination of natural radioactivity in building materials used in Tunisian dwellings by gamma ray spectrometry

The radioisotopic content of 17 samples of natural and manufactured building materials collected in Tunisia have been analysed by using gamma spectrometry. From the measured gamma ray spectra, activity concentrations are determined for (232)Th, (226)Ra, (235)U and (40)K. The total effective dose and the activity concentration index are calculated applying the dose criteria recommended by the European Union for building materials. The results of (226)Ra, (232)Th and (40)K found in Tunisian building materials indicate that radium and thorium concentrations do not exceed 40 Bq kg(-1), but potassium concentration varies between 50 and 1215 Bq kg(-1). The total effective dose rates per person indoors are determined to be between 0.07 and 0.86 mSv y(-1). Only two materials exceed the reference level of 0.3 mSv y(-1). The activity concentration index is <1.     

Annual effective dose due to natural radionuclides in building blocks in eight cities of Southwestern Nigeria

The specific absorbed dose rates due to (226)Ra, (232)Th and (40)K in building blocks have been determined for a model dwelling dimension of 3.6 x 3.6 x 3.0 m(3), wall thickness 10 cm and density of 1.73 x 10(3) kg m(-3) in eight cities across Southwestern Nigeria. The Mustonen method of calculating gamma-ray annual exposure rate from the radioactivity concentrations (Bq kg(-1)) of (226)Ra, (232)Th and (40)K in the blocks have been adopted with modifications to suit the Nigerian situation. The specific absorbed dose rates obtained were as follows: 11.36, 14.94 and 0.92 microGy y(-1) per Bq kg(-1) for (226)Ra, (232)Th and (40)K, respectively. These dose rates were used to calculate the annual effective dose in the model dwelling. The annual effective dose obtained varied between 209.20 (Osogbo) and 400.36 microSv y(-1) (Abeokuta). The values are in the range of values obtained for the German Democratic Republic (309 microSv y(-1)) and Jordan (470 microSv y(-1)).     

Assessment of radiological hazards of naturally occurring radioactive materials in cement industry

A study on the radiological hazard in Portland cement due to the presence of naturally occurring radioactive materials is being carried out. The Portland cement manufactured in the Islamabad/Rawalpindi region of Pakistan, intermediate products (clinker) and the various raw materials which compose the product have been analysed for (226)Ra, (232)Th and (40)K using a gamma spectrometry system with a N-type high-purity germanium detector of 80 % relative efficiency. From the measured gamma ray spectra, specific activities were determined. The mean values of the total specific activity of (226)Ra, (232)Th and (40)K are 34.2±11.9, 29.1±3.6 and 295.1±66.9 Bq kg(-1), respectively in Portland cement, 28.4±8.7, 11.3±1.7 and 63.1±17.3 Bq kg(-1), respectively in lime stone, 8.2±1.9, 16.2±3.9 and 187.7±53.2 Bq kg(-1), respectively in gypsum, 34.7±13.1, 41.2±6.7 and 187.6±17.2 Bq kg(-1), respectively in clay, 41.1±11.8, 39.3±6.9 and 195.1±29.2 Bq kg(-1), respectively in latrite and 51.1±18.2, 23.2±1.2 and 258.4±15.3 Bq kg(-1), respectively in clinker. The radium equivalent activities (Ra(eq)), external hazard index (H(ex)), internal hazard index (H(in)), absorbed dose rate in air (D) and annual effective dose rate (E(eff)) were also determined. The measured activity concentrations for these radio nuclides and radiological indices were compared with the reported national and international data. All these measured values are comparable with the worldwide data reported in UNSCEAR publications.     

Natural radioactivity measurements in rock samples of Cuihua Mountain National Geological Park, China

The concentrations of the natural radionuclides namely 40K, 232Th and 226Ra in rock samples collected from Cuihua Mountain National Geological Park of China have been determined using a NaI(Tl) detector. The concentrations of 226Ra, 232Th and 40K in the studied rock samples range from 10.7 to 34.8, 19.9 to 53.6 and 642.7 to 1609.9 Bq kg(-1) with an average of 20.4, 30.1 and 1009.5 Bq kg(-1), respectively. The concentrations of these radionuclides are compared with the typical world values. To evaluate the radiological hazard of the natural radioactivity, the radium equivalent activity, the air absorbed dose rate, the annual effective dose rate, the representative level index and the values of both external and internal hazard indices were evaluated and compared with the internationally approved values. The radium equivalent activity values of all rock samples are lower than the limit of 370 Bq kg(-1). The values of H ex and H in are less than unity. The mean outdoor air absorbed dose rate is 69.7 nGy h(-1), and the corresponding outdoor effective dose rate is 0.086 mSv y(-1).     

Natural radionuclides contents and radon exhalation rates in building materials used in South Korea

The natural radionuclide (226Ra, 232Th and 40K) contents of building materials commonly used in South Korea have been determined by a gamma ray spectroscopy system using a high purity germanium detector. The radon exhalation rates and emanation coefficients of building materials have also been studied. The average concentrations of 226Ra, 232Th and 40K in building materials were in the range of 6.47-271 Bq.kg-1, N.D.-89.9 Bq.kg-1 and 16.8-1081 Bq.kg-1, respectively. The average radon exhalation rates and emanation coefficients were in the range of 0.0061-0.2404 Bq.kg-1.h-1 and 2.39-11.5%, respectively.     

Natural and artificial radionuclide measurements and radioactivity assessment of soil samples in eastern Sichuan province (China)

The activity concentrations of natural and artificial radionuclides were measured in the eastern region of Sichuan province (China). One hundred and ninety-three soil samples from this region were collected and analysed by high-purity germanium gamma spectrometry. The measured results show that the average radioactivity concentrations of (226)Ra, (232)Th, (40)K and (137)Cs in the soil samples are 26, 49, 440 and 6 Bq kg(-1), respectively. The calculated average radium equivalent activity is 130 Bq kg(-1), which is less than the recommended limit of 370 Bq kg(-1). The absorbed dose rate and annual effective dose are 60 nGy h(-1) and 74 μSv, respectively. This is the first time the absorbed dose rate in the east region of Sichuan has been mapped. Overall, the environmental radiation background is greater in the southern part of the area studied than in the northern.     

Assessment of radionuclide level in topsoil samples for partial areas of Tibet, China

By using high-purity germanium gamma spectroscopy, specific activities of naturally occurring and man-made radionuclides were determined in topsoil samples collected from Nyingch, Lhasa and Xigazê of Tibet Autonomous Region, China. The average activity concentrations of (226)Ra, (232)Th and (40)K were 25.1 ± 0.7, 67.1 ± 2.8 and 608.6 ± 12.9 Bq kg(-1), respectively. The activity concentration of (137)Cs was found to vary from <0.3 (minimum detection concentration) to 46.2 Bq kg(-1) with an average of 4.3 ± 0.5 Bq kg(-1). By using the results of (226)Ra, (232)Th and (40)K in the sampled soils, the average outdoor gamma dose rate in air was calculated as 77.5 ± 23.2 nGy h(-1). Furthermore, the average outdoor annual effective dose from terrestrial radiation was 0.10 mSv. The external hazard index in this work varied from 0.20 to 0.70 with an average of 0.40 ± 0.14. The external exposure from terrestrial radiation will not pose any significant radiological threat to the population resident in the studied areas.