Preparation and characterization of loess sediment for use as a reference material in the annual radiation dose determination for luminescence dating

Loess sediment was prepared and characterized with well-established K, Th and U contents, and corresponding ⁴⁰K, ²³²Th and ^235,238U activities, intended for use as a reference material in the annual radiation dose determination for luminescence dating. To this purpose, loess was collected in Volkegem, Belgium, and — after drying, pulverizing and homogenizing — characterized via k ₀-INAA and HPGe gamma-ray spectrometry. This led to 12 kg material with a grain size below 50 μm, with established K, Th and U homogeneity, with the ²³²Th and ²³⁸U decay series proven to be in equilibrium, and with the following K, Th and U reference data: K = 16.5±1.5 g·kg⁻¹ (⁴⁰K = 497±45 Bq·kg⁻¹); Th = 10.4±0.6 mg·kg⁻¹ (²³²Th = 42.2±2.5 Bq·kg⁻¹); U = 2.79±0.12 mg·kg⁻¹ (²³⁸U = 34.5±1.5 Bq·kg⁻¹; ²³⁵U = 1.59±0.09 Bq·kg⁻¹; ^235+238U = 36.1±1.7 Bq·kg⁻¹). These data were confirmed via comparison with the results from NaI(Tl) field gamma-ray spectrometry, thick-source ZnS alpha-counting and thick-source GM beta-counting (after converting all data to Gy·ka⁻¹). The reference material is available (as aliquots up to 200 g) from the Ghent Luminescence Laboratory to all interested luminescence dating laboratories upon motivated request.     

Concentration of natural radionuclides in and around Padubidri on the coastal Karnataka,India

The activity concentrations of natural radionuclides viz. ²³²Th, ²²⁶Ra and ⁴⁰K were measured in soil samples of Padubidri on the coastal Karnataka, the site for the proposed coal based thermal power station, using gamma-ray spectrometry to establish a baseline data on radioactivity levels in the environment of the region. The activity concentration of ²³²Th varies in the range of 38.5–115.5 Bq·kg⁻¹ with a mean value of 66.0 Bq·kg⁻¹, the activity concentration of ²²⁶Ra varies in the range 35.3–72.5 Bq·kg⁻¹ with a mean value of 53.5 Bq·kg⁻¹ and that of ⁴⁰K varies in the range of 307.5–550.9 Bq·kg⁻¹ with a mean value of 419.3 Bq·kg⁻¹. The radium equivalent activity varies in the range of 140.0–242.9 Bq·kg⁻¹ with a mean value of 180.2 Bq·kg⁻¹. The correlation between ²²⁶Ra and ⁴⁰K, ²³²Th and ⁴⁰K and ²²⁶Ra and ²³²Th was studied from the results of the concentration of these naturally occurring radionuclides. The calculated dose rates in air due to these naturally occurring radionuclides varies in the range of 66.0–110.0 nGy·h⁻¹ with a mean dose rate of 83.1 nGy·h⁻¹.     

Natural radioactivity and indoor radiation measurements in buildings and building materials in Gobichettipalayam town

Samples of natural and manufactured building materials used by the people of Gobichettipalayam town have been analyzed for ²²⁶Ra, ²³²Th and ⁴⁰K using gamma-ray spectrometry. Radium equivalent activity of the materials has been measured using the formula given by OECD and the geometric mean value of sand, clay and cements are found to be 53.53 Bq·kg⁻¹, 89.09 Bq·kg⁻¹ and 72.25 Bq·kg⁻¹, respectively. The radium equivalent activities obtained in the building materials are all well below the acceptable limit. The indoor gamma-dose has been measured using thermoluminescence dosimeters and it was found in the range of 1051.2–3946.0 μGy/year. The annual effective indoor gamma radiation dose to the people of Gobichettipalayam town has been found to be 0.8 mSv/y.     

Radiation dose due to radon,thoron and their decay products in indoor environment of Khurja City,U.P., India

Inhalation of radon, thoron and their decay products can cause a significant health hazard when present in enhanced levels in the indoor environment like a human dwelling. In the present work a set of indoor radon and thoron measurements was carried out using time-integrated passive twin cup dosimeters containing LR-115 Type II solid state nuclear track detectors in different houses of Khurja City in Bulandshahar district of U.P. in India, built of the same type of building materials. The radon gas concentration was found to vary from 9.18 to 23.19 Bq m^?3 with an average value of 16.02 Bq m^?3 (SD = 3.68) and the thoron gas concentration varied from 2.78 to 9.03 Bq m^?3 with an average value of 5.36 Bq m^?3 (SD = 1.58). The radon progeny concentration ranged from 0.99 to 2.51 mWL with an average value of 1.77 mWL (SD = 0.40) and the concentration of thoron progeny was found to vary from 0.30 to 0.98 mWL with an average value of 0.58 mWL (SD = 0.17). The annual effective dose varied from 0.27 to 0.67 mSv year^?1 with an average value of 0.47 mSv year^?1(SD = 0.10).     

Radioactivity of coals and fly ashes

The level and the behavior of the naturally occurring primordial radionuclides ²³⁸U, ²²⁶Ra, ²¹⁰Pb, ²³²Th, ²²⁸Ra and ⁴⁰K in coals and fly ashes are described. The activity concentrations of the examined coals and originated from coal mines in Greece ranged from 117 to 435 Bq·kg⁻¹ for ²³⁸U, from 44 to 255 Bq·kg⁻¹ for ²²⁶Ra, from 59 to 205 Bq·kg⁻¹ for ²¹⁰Pb, from 9 to 41 Bq·kg⁻¹ for ²²⁸Ra and from 59 to 227 Bq·kg⁻¹ for ⁴⁰K. These levels are comparable to those appeared in coals of different countries worldwide. The activity concentrations of the examined fly ashes and produced in coal-fired power plants in Greece ranged from 263 to 950 Bq·kg⁻¹ for ²³⁸U, from 142 to 605 Bq·kg⁻¹ for ²²⁶Ra, from 133 to 428 Bq·kg⁻¹ for ²¹⁰Pb, from 27 to 68 Bq·kg⁻¹ for ²²⁸Ra and from 204 to 382 Bq·kg⁻¹ for ⁴⁰K. The results showed that there is an enrichment of the radionuclides in fly ash relative to the input coal during the combustion process. The enrichment factors (EF) ranged from 0.60 to 0.76 for ²³⁸U, from 0.69 to 1.07 for ²²⁶Ra, from 0.57 to 0.75 for ²¹⁰Pb, from 0.86 to 1.11 for ²²⁸Ra and from 0.95 to 1.10 for ⁴⁰K.     

Concentration of radionuclides in building and ceramic materials of Bangladesh and evaluation of radiation hazard

The concentration of radioactive²²⁶Ra,²³²Th and⁴⁰K in building and ceramic materials of Bangladesh was investigated by γ-spectrometry with two HPGe detectors. Radium equivalent activities, representative level index values, criterion formula, emanation coefficients and²²²Rn mass exhalation rates were estimated for the radiation hazard of the natural radioactivity in the materials. The activity concentrations of the natural radionuclides, radium equivalent activities, emanation coefficients and²²²Rn mass exhalation rates are compared with the corresponding values for building and ceramic materials of different countries. The radium equivalent activities in the samples varied between 30.9 (mosaic stone) and 328.0 Bq·kg⁻¹ (gypsum). The emanation coefficient of the materials ranged from 7.83 (cement) to 33.0% (soil) and the²²²Rn mass exhalation rate ranged from 2.31 (stone chips) to 118.0 μBq·kg⁻¹·s⁻¹ (gypsum).     

Radon and thoron progeny levels in air samples at Udagamandalam region of Nilgiris in India

Measurement of concentration of radon and thoron daughter products in various indoor environment covering four seasons of a year in Udagamandalam Taluk of Nilgiris biosphere has been carried out using a high volume air sampler to asses the inhalation dose to the population which delivers higher dose than the radon and thoron gas alone. The potential alpha-energy concentrations of the radon and thoron progeny ranged from 0.97 to 12.72 mWL and from 1.63 to 15.83 mWL with a geometric mean of 6.02 and 7.89 mWL, respectively, taking all seasons into account. These measurements have yielded a wealth of data on the variation among the indoor radon and thoron progeny in various places during different seasons. The radon and thoron progeny levels are higher in winter seasons and are less in summer season with autumn and spring data lie in between winter and summer. Using the dose conversion factor for indoor exposures given in UNSCEAR 93 report the internal equivalent dose to the inhalation of radon progeny is evaluated to be 1357 mSv^.y^–1 and the corresponding annual effective dose equivalent value has been found to be 2.13 mSv^.y^–1. It can be observed that the mean value of radon is higher than the Indian average. Also it is found the radon and thoron progeny levels are higher in the case of houses built with rock and granite and in tiled type houses of nearly 100 years old. The levels are less in the case of houses built with brick and cement. The observed results for different types of houses and seasons are discussed in this paper.     

Radioactivity measurements and radiation dose assessments due to natural radiation in Karabük (Turkey)

In this work, the radionuclide activity concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K in surface soils and radon levels in dwellings of Karabük, Turkey were determined in order to evaluate the environmental radioactivity. Concentrations of ²²⁶Ra, ²³²Th and ⁴⁰K radionuclides were determined using gamma spectrometry with using HPGe detector. The etch track detectors (CR-39) were used to determine the distribution of radon concentrations. The average activity concentrations for ²²⁶Ra, ²³²Th and ⁴⁰K were found as 21.0, 23.5 and 363.5 Bq kg⁻¹, respectively. The calculated average annual effective dose equivalent from the outdoor terrestrial gamma radiation from ²²⁶Ra, ²³²Th and ⁴⁰K is 53.5 μSv y⁻¹. The average radon concentration and annual effective dose equivalent of ²²²Rn in Karabük dwellings were obtained 131.6 Bqm⁻³ and 3.32 mSv y⁻¹, respectively. The evaluated data were compared with the data obtained from different countries.     

Study of radon,thoron and their progeny levels in indoor environment of Firozabad city in U.P., India

Twin cup pin-hole dosimeters having LR-115 as the detector were used to measure the concentration of radon and thoron in the dwellings of Firozabad city of Uttar Pradesh State in India. The mean values of radon, thoron, radon progeny and thoron progeny concentrations were found to be 37.4 Bqm^?3, 13.7 Bqm^?3, 4.0 and 1.5 mWL respectively. The average value of annual effective dose equivalent to the inhabitants of Firozabad city was found to be 1.1 mSv and is below the action level as recommended by the ICRP.     

Natural radioactivity and its gamma dose rate in Mission (Texas) soils

The activity concentration of radionuclides in ²³⁸U, ²³²Th, and ⁴⁰K were determined in Mission (Texas) surface soils through gamma-ray spectrometry measurements using hyper pure germanium detector. Activity concentrations of ²³⁸U, ²³²Th, and ⁴⁰K were 13–32 Bq kg^?1 (mean value: 23 Bq kg^?1), 17–47 Bq kg^?1 (mean value: 31 Bq kg^?1), and 100–460 Bq kg^?1 (mean value: 300 Bq kg^?1) respectively. The absorbed gamma dose rate in air from these soils were found in the range of 23 to 56 nGy h^?1 with an average value of 42 nGy h^?1. The contribution to the absorbed gamma dose rate in air was observed as 26 % from ²³⁸U, 45 % from ²³²Th, and 29 % from ⁴⁰K. The outdoor annual effective dose equivalent varied between 28 and 69 μSv y^?1 with the mean value of 52 μSv y^?1.The evaluated data were compared with the data from different countries and also with the world mean value.     

Radiological assessment of natural and fallout radioactivity in the soil of Chamba and Dharamshala areas of Himachal Pradesh,India

This paper presents the results of measurement of natural and fallout radioactivity in soil samples of Chamba and Dharamshala areas in Himachal Pradesh, India. Spatial distribution of ²³⁸U, ²²⁶Ra, ²³²Th, ⁴⁰K, ¹³⁷Cs was determined using High resolution gamma-ray spectrometry. The mean activity concentration in Chamba region due to ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs was 32.3, 58.4, 588.3, and 10.9 Bq kg⁻¹, respectively, whereas in Dharamshala it was 35.7, 61.3, 594.9, 10.0 Bq kg⁻¹, respectively. Absorbed gamma dose rate (D) in air was calculated using appropriate dose conversion factors, which was varying from 45 to 103 nGy h⁻¹. To control the radiation exposure due to natural radioactivity in soil, if it is used as building materials, radium equivalent activity (Ra_eq) and activity index were also evaluated. Radium equivalent activity calculated for the soil ranged from 95.5 to 234.2 Bq kg⁻¹ with average of 171.0 Bq kg⁻¹.The calculated Activity concentration index was ranged from 0.34 to 0.85 with an average value of 0.64. The natural and fallout radioactivity in soil of this region is comparable with Indian average and other parts of the world. The percentage contribution of ²³⁸U, ²³²Th and ⁴⁰K and ¹³⁷Cs to the average external gamma dose rate was 22, 46, 32, 2%, respectively. This shows that the dose contribution due to fallout radioactivity is negligible as compared to the natural radioactivity.     

Contents of238Pu,239,240Pu and137Cs in sediments and shore depositions of the Vltava river in 1995–1996

The²³⁸Pu,^239,240Pu and¹³⁷Cs concentrations in sediments and shore deposition samples of the Vltava river were determined.^239,240Pu and¹³⁷Cs concentrations in sediment samples (five locations) ranged from 19.6 to 124.8 mBq·kg⁻¹ and from 1.8 to 28.2 Bq·kg⁻¹, respectively. The²³⁸Pu,^239,240Pu and¹³⁷Cs concentrations in shore deposition samples (four locations) ranged from 2 to 16.8, from 26.8 to 477.2 mBq·kg⁻¹, and from 1.6 to 86.3 Bq·kg⁻¹, respectively. The superficial activity of studied radionuclides in shore deposition areas was determined and radionuclide origin at studied locations was discussed.     

Determination of naturally occurring radionuclides in selected rocks from Hetaunda area,central Nepal

The specific activities of the naturally occurring radionuclides ²³⁸U, ²³²Th, and ⁴⁰K were measured in rock samples from the Hetaunda area, central Nepal, using gamma spectrometry. The specific activities were found to be in the range of 17–95 Bq kg⁻¹ for ²³⁸U, 24–260 Bq kg⁻¹ for ²³²Th and 32–541 Bq kg⁻¹ for ⁴⁰K. From these data absorbed dose rates in air and annual effective doses were calculated and compared with respective data from the UNSCEAR compilation. The results from our study open the door to the safe applicability of most of the investigated materials as a cheep building material.     

Radon exhalation potential and natural radioactivity in soil collected from the surrounding area of a thermal power plant

Journal of Radioanalytical and Nuclear Chemistry - In the present study, radon (222Rn), thoron (220Rn) exhalation rates, and the specific activities of 238U,232Th, and 40K of 75 soil samples...     

Natural radioactivity of spring water used as spas in Spain

Spring waters used as spas may contain significant amounts of natural radionuclides, so, in some circunstances, a radiation protection issue can arise for the population and/or the spas workers. EU has identified some groups of employees to be exposed to natural radiation in the 1996 Euratom Directive. Among these are workers of thermal spas who may be exposed to high radiation doses due to high radon concentrations in indoor air. In order to evaluate the potencial risk of the spring waters used as spas, gross-α and gross-β activity, ²²⁶Ra and ²²²Rn concentration levels were measured in 82 spas all over the country. Gross-alpha and gross-beta concentrations ranged from LLD to 17 Bq·l⁻¹ and from LLD to 60 Bq·l⁻¹, respectively. ²²⁶Ra concentrations ranged from <4 to 3,660 mBq·l⁻¹. ²²²Rn concentrations ranged from <4 to 1868 Bq·l⁻¹. Correlations between ²²⁶Ra concentrations and gross-α activity were obtained.     

Evaluation of natural gamma radiation and absorbed gamma dose in soil and rocks of Perambalur district (Tamil Nadu,India)

The activity concentrations and absorbed gamma dose of primordial radionuclides ²³⁸U, ²³²Th and ⁴⁰K were determined employing γ-ray spectrometry in 31 soil samples from the land area earmarked for house construction in Perambalur district and 14 rock samples from quarries that supply stones for the entire district. The soil samples registered relatively a higher mean value of 13.2 Bq kg^?1 for ²³⁸U, 66 Bq kg^?1 for ²³²Th and 340.3 Bq kg^?1 for ⁴⁰K as compared to mean values for rock samples (²³⁸U—8.0 Bq kg^?1; ²³²Th—65.1 Bq kg^?1; ⁴⁰K—199.1 Bq kg^?1). The mean absorbed gamma dose rate for soil (61.4 nGy h^?1) marginally exceeded the prescribed limit of 55 nGy h^?1 while, rocks registered the mean absorbed gamma dose rate of 10.4 nGy h^?1. The mean radium equivalent activity was distinctly higher in soil (130.6 Bq kg^?1) than in rock (20.0 Bq kg^?1). However, these values were lower than the limit (370 Bq kg^?1) set by OECD for building materials. It is evident from the data that the soil and rocks do not pose any radiological risk for house constructions in Perambalur district.     

Application of radiochemical methods and dispersion model in the study of environmental pollution in Brazil

Methodologies for analysis of anthropogenic and natural radionuclides in marine samples were developed and applied in environmental samples. Results of systematic measurements of these radionuclides have showed that artificial radioactivity levels are in agreement with the values from the regions not affected directly by nuclear accidents or nuclear reprocessing plant discharges and are due to the global fallout. The average concentration of¹³⁷Cs is of 1.4 Bq·m⁻³ in seawater, ranges from 13 to 220 mBq·kg⁻¹ in fish, and from 0.4 to 1.8 Bq·kg⁻¹ for sediments.⁹⁰Sr levels in seawater are of 1.8 Bq·m⁻³ and in fish vary from 19 to 75 mBq·kg⁻¹. Sediments present concentrations of⁹⁰Sr lower than 0.8 Bq·kg⁻¹ and for^239+240Pu of 0.03 to 0.18 Bq·kg⁻¹.²¹⁰Po levels in fish range from 0.5 to 5.3 Bq·kg⁻¹. The data generated represent reference values for our country and are used to estimate the intake levels of these radionuclides by consuming of marine products.     

Determination and spatial distribution of <Superscript>137</Superscript>Cs in soils,mosses and lichens near Kavanayen,Venezuela

The activity of ¹³⁷Cs was determined in soils, mosses, lichens and other vegetation along the Caruay River and near the town of Kavanayen. The range of values for the soils was from <1.2 Bq·kg⁻¹ of ¹³⁷Cs (our detection limit) to 14.1 Bq·kg⁻¹. The range of ¹³⁷Cs activities in the mosses ranged from 9.9 to 17.9 Bq·kg⁻¹ with a mean value of 13.4±4 Bq·kg⁻¹; all the moss samples were found along the river. While the ¹³⁷Cs activities in the lichens ranged from 9.1 to 29.8 Bq·kg⁻¹; the two values along the river were about three factors higher than the one near Kavanayen. It was concluded that the ¹³⁷Cs activities in the soils, mosses and lichens are much higher along the river in respect to the nearby town of Kavanayen.     

Levels of <Superscript>232</Superscript>Th activity in the South Adriatic Sea marine environment of Montenegro

²³²Th activities in the South Adriatic Sea-water, surface sediment, mud with detritus, seagrass (Posidonia oceanica) samples, and the mullet (Mugilidae) species Mugil cephalus, as well as soil and sand from the Montenegrin Coast, were measured using the six-crystal spectrometer PRIPYAT-2M, which has relatively high detection efficiency and a good sensitivity, and allows a short acquisition time, and measuring samples of any shape, without preliminary preparation and calibration measurements for different sample geometries. An average ²³²Th activity concentration in surface soil layer is found to be 40.33 Bq kg⁻¹, while in sand—4.7 Bq kg⁻¹. The absorbed dose rate in air due to ²³²Th gamma radiation from surface soil layer ranged from 11.76 to 63.39 nGy h⁻¹, with a mean of 24.06 nGy h⁻¹. Corresponding average annual effective dose rate has been found to be 0.03 mSv y⁻¹. The absorbed dose rates due to the thorium gamma radiation in air at 1 m above sand surface on the Montenegrin beaches have been found to be from 0.41 to 9.08 nGy h⁻¹, while annual effective dose rates ranged from 0.0005 to 0.011 mSv y⁻¹. ²³²Th activity concentration in seawater ranged from 0.06 to 0.22 Bq L⁻¹, as in the mullet (Mugil cephalus) whole individuals from 0.63 to 1.67 Bq kg⁻¹. Annual intake of ²³²Th by human consumers of this fish species has been estimated to provide an effective dose of about 0.003 mSv y⁻¹.     

Assessment of natural radioactivity in silt samples from Moticher lake near Kakrapar Atomic Power Station,India

The naturally occurring radioisotopes such as ²³⁸U, ²³²Th and ⁴⁰K in the silt samples collected from Moticher lake, Gujarat were evaluated. The activity of ²³⁸U, ²³²Th and ⁴⁰K was found to be 4.4-9.7 Bq kg⁻¹ with a mean 6.4 ± 1.3 Bq kg⁻¹, 10.5–21.2 Bq kg⁻¹ with a mean 15.6 ± 2.5 Bq kg⁻¹ and 102–231 Bq kg⁻¹ with a mean 160 ± 40 Bq kg⁻¹, respectively. The depth profile study could not reveal any significant vertical correlation on radioactivity levels of ²³⁸U, ²³²Th and ⁴⁰K. Radium equivalent activity (Ra_eq), external hazard index (H _ex) and internal hazard index (H _int) were calculated by using the activity of ²³⁸U or ²²⁶Ra, ²³²Th and ⁴⁰K in silt samples. Annual Effective Dose Equivalent (AEDE) level in Moticher silt was found to be 24.8 ± 5.0 μSv year⁻¹, which is much lower than the worldwide average value. The relative contribution to dose due to ²³⁸U and ²³²Th series were found to be 14% and 53%, followed by the contribution of 33% due to ⁴⁰K.