Activity Concentrations Of Primordial Radionuclides Research Articles

Using radial basis artificial neural networks to predict radiation hazard indices in geological materials.

The estimation of exposures to humans from the various sources of radiation is important. Radiation hazard indices are computed using procedures described in the literature for evaluating the combined effects of the activity concentrations of primordial radionuclides, namely, 238U, 232Th, and 40K. The computed indices are then compared to the allowed limits defined by International Radiation Protection Organizations to determine any radiation hazard associated with the geological materials. In this paper, four distinct radial basis function artificial neural network (RBF-ANN) models were developed to predict radiation hazard indices, namely, external gamma dose rates, annual effective dose, radium equivalent activity, and external hazard index. To make RBF-ANN models, 348 different geological materials' gamma spectrometry data were acquired from the literature. Radiation hazards indices predicted from each RBF-ANN model were compared to the radiation hazards calculated using gamma spectrum analysis. The predicted hazard indices values of each RBF-ANN model were found to precisely align with the calculated values. To validate the accuracy and the adaptability of each RBF-ANN model, statistical tests (determination coefficient (R2), relative absolute error (RAE), root mean square error (RMSE), Nash-Sutcliffe Efficiency (NSE)), and significance tests (F-test and Student's t-test) were performed to analyze the relationship between calculated and predicted hazard indices. Low RAE and RMSE values as well as high R2, NSE, and p-values greater than 0.95, 0.71, and 0.05, respectively, were found for RBF-ANN models. The statistical tests' results show that all RBF-ANN models created exhibit precise performance, indicating their applicability and efficiency in forecasting the radiation hazard indices of geological materials. All the RBF-ANN models can be used to predict radiation hazard indices of geological materials quite efficiently, according to the performance level attained.

Assessment of Activity Concentrations and Soil-to-Plant Transfer Factors of Natural Radioactivity in Rice Plant Components grown in Kano State, Nigeria

Transfer Factor (TF) depicts the percentage or fraction of natural radioactivity in the soil that is absorbed by different parts of a plant which are eventually transferred, directly or indirectly, to man during ingestion. Activity concentrations of primordial radionuclides were determined in farm soil and rice plant components (root, stem, leaf and seed) in six Local Government Areas (Bagwai, Bunkure, Dambatta, Garko, Kura and Wudil) renowned for production of rice in Kano State, Nigeria, using gamma-ray spectrometry method with sodium iodide scintillation detector. The mean activity concentrations of 40K, 238U and 232Th were: 509.51, 27.75, and 12.26 Bq.kg-1 correspondently in soil; 227.40, 14.24, and 5.19 Bq.kg-1 correspondingly in seed; 935.53, 32.73, and 7.29 Bq.kg-1 accordingly in leaf; 803.65, 16.72, and 6.76 Bq.kg-1 respectively in stem; and, 408.91, 30.03, and 10.31 Bq.kg-1 correspondingly in root. The mean concentrations of 40K reported in soil were greater than the world average of 400 Bq.kg-1, while those of 238U and 232Th were less than the world mean values of 35 Bq.kg-1 and 30 Bq.kg-1 respectively. The estimated mean of TFs of 40K, 238U and 232Th were: 0.52, 0.61, and 0.43 respectively in the seed; 1.95, 1.45, and 0.69 respectively in leaf; 1.72, 0.75, and 0.64 correspondingly in the stem; and, 0.85, 1.27, and 0.76 accordingly in the root. Except for a few plant samples where BDL were recorded for 238U and 232Th, all values of TFs were greater than the recommended values of 4.9 x 10-3 and 2.1 x10-4 given for 238U and 232Th...

Evaluation of radiological risk associated with local building materials commonly used in Northwestern Nigeria

In this study, potential radiological risk due to the activity concentrations of primordial radionuclides (226Ra, 232Th, and 40K) in commonly used local building materials (sand, clay, kaolin and gypsum) in Northwestern Nigeria were assessed using NaI (Tl) detector. The measured activity concentrations ranged from 47 to 63 Bq kg−1 for 226Ra, 24–32 Bq kg−1 for 232Th, and 219–257 Bq kg−1 for 40K respectively. The mean values of 232Th, and 40K for all samples were below the respective world averages of 45 and 420 Bq kg−1 with that of 226Ra for all the samples higher than the world average value of 32 Bq kg−1. The potential radiological risks were assessed by determining radium equivalent activity (Raeq), internal and external hazard indices (Hin and Hex), absorbed gamma dose rates (DR), internal annual effective dose rates (IAED), and annual gonadal dose equivalent (AGDE) and activity utilization index (AUI). The assessed parameters were found to range between 104 and 125 Bq kg−1, 0.99 to 1.15, 0.28 to 0.34, 48 to 58 nGyh−1, 0.76 to 0.86 mSvy−1, and 0.78 to 0.96 respectively. The Raeq and DR for all the analyzed samples were found to be within International recommended limits of 370 Bq kg−1 and 59 nGy h−1 as recommended by UNSCEAR.

Radionuclide concentrations in medicinal florae and committed effective dose through Ayurvedic medicines

Purpose: Ayurveda is one of the oldest systems of medicines in the world being practiced widely in the Indian subcontinent for more than 3000 years, and still remains as one of the important traditional health care systems. The Ayurvedic drugs are derived primarily from various parts of the plants, like root, leaf, flower, fruit or plant as a whole. Plants uptake minerals and other nutrients from the soil through their root system. Along with other minerals radionuclides present in the growing media also reach to the plant parts following the same pathway. Realizing the probable health hazards via the intake of Ayurvedic drugs, it is important to assess the concentration of natural radionuclides in commonly used medicinal plants.Materials and methods: NaI(Tl) scintillator-based gamma-ray spectrometry has been used to determine the activity concentrations of primordial radionuclides (226Ra, 232Th and 40K) in the most commonly used medicinal plant parts as ingredients of Ayurvedic medicines in India.Results and discussion: The average specific activity (Bqkg−1) of 226Ra, 232Th and 40K was found to be 43 ± 18, 36 ± 15 and 230 ± 46, respectively. The estimated annual committed effective doses due to the intake of common Ayurvedic medicines at prescribed dosage was found to be 39 ± 16 µSv y−1, which is quite low as compared with the radiation dose limit of 1 mSvy−1 from all natural sources, reported by the International Commission on Radiological Protection (ICRP-60).Conclusions: It is found categorically that intake of Ayurvedic medicines at normal dosage poses no radiological hazard to the individual. Present results are significant in the wake of myths that many hazardous materials including radioisotopes are present at higher levels. Obtained results also serve as a reference information for the distribution of radionuclides in medicinal plant species.

Background Radiation Measurement and the Assessment of Radiological Impacts due to Natural Radioactivity Around Itakpe Iron-Ore Mines

Mining activity and metal extraction processes have been identified as one of the major pathways through which natural radionuclides are accumulated in the terrestrial environment. Exposure to excessive radiation from natural radionuclides can cause deleterious health hazards to man. In this study therefore, the activity concentrations of primordial radionuclides (40K, 238U and 232Th) were measured in rock, soil, tailings and water samples collected from abandoned iron ore mines in order to estimate the radiological impacts associated with the previous mining and metal extraction activities within the environment of abandoned Itakpe iron-ore mines. Gamma spectrometry utilizing a well calibrated NaI(Tl) detector was employed for the measurements. Results show that the average activity concentrations of 40K, 238U and 232Th are 1084 ± 581, 11.0 ± 7.7 and 5.0 ± 1.8 Bq kg−1 respectively for rock samples and 415.6 ± 197.5, 12.8 ± 5.7 and 8.8 ± 5.8 Bq kg−1, respectively for soil samples. The activity concentrations of the three radionuclides are much lower in water samples compared to rocks and soil. Radiological hazard indices calculated from the activity concentrations show that the mining activities have little or no negative impacts on the environment as the radiological risk indices obtained are all lower than their permissible limits.

Radioactive map of soil at Mount Lebanon province and external dose assessment

A total of 150 samples were collected from uncultivated areas at 87 locations distributed uniformly along the Mount Lebanon province. Measurements were carried out using gamma spectrometers with high purity germanium detectors. The activity concentrations of primordial radionuclides ranged from 14.0 ± 2.0 to 132.0 ± 8.0 Bq kg−1 for 238U, from 5.4 ± 0.3 to 77.0 ± 3.0 Bq kg−1 for 232Th, from 12.0 ± 1.0 to 227.0 ± 10.0 Bq kg−1 for 226Ra, and from 10.7 ± 0.7 to 714.0 ± 16.0 Bq kg−1 for 40K, with average values of 37, 24, 46, and 206 Bq kg−1, respectively. The average activity concentrations of 238U and 232Th were comparable to the worldwide average value, while that of 40K was found to be half of the world average values stated in UNSCEAR (Sources, effects, and risks of ionizing radiation, United Nations, New York, 2000). The average value of 226Ra was found to be slightly higher than the worldwide value. The activity concentration of the 137Cs at the measurement time in 2015 was found to lie between 0.30 ± 0.06 and 102.00 ± 2.00 Bq kg−1 with an average of 23 Bq kg−1. Surface activity concentrations were calculated, and radioactive maps were plotted. The average value of total absorbed dose rate and the annual effective dose was found to be lower than the world average values. Radium equivalent and external hazard index were within the international recommended values.

Air Absorbed Dose Rate Measurements and External Dose Assessment by Car-Borne Survey in the Gold Mining Areas of Betare-Oya, Eastern-Cameroon

In order to assess radiological exposure of the public due to natural occurring radioactive materials from gold mining areas of Betare-Oya and vicinity, Eastern Cameroon, a preliminary study was carried out in 2015 for laboratory measurements of activity concentrations of primordial radionuclides. In terms of annual effective dose, results revealed a mean value of 0.34 mSv y-1. However, it was necessary to make air absorbed dose rate contour map for a detailed evaluation of external dose. For this purpose, a car-borne survey using a 3-in × 3-in NaI(Tl) scintillation spectrometer was carried out in Betare-Oya and vicinity. Absorbed dose rates in air ranged from 23 to 80 nGy h-1 with a mean value of 44 ± 7 nGy h-1. The average values of activity concentrations in soil of 40K, 238U and 232Th were 197 ± 21 Bq kg-1, 37 ± 13 Bq kg-1 and 32 ± 7 Bq kg-1 respectively. 232Th was found to be the main contributor to the absorbed dose rate in air from outdoor terrestrial radiation in the study areas with a mean value of 43%. External annual effective dose ranged from 0.17 to 0.60 mSv y-1 with a mean value of 0.33 ± 0.05 mSv y-1, in agreement with the result (0.34 mSv y-1) of the previous study performed in the same areas using gamma spectrometry in laboratory for radioactivity measurements in soil samples. This survey first and widely revealed an aspect of natural radiation exposures in soil mining areas of Eastern Cameroon.

Radiological monitoring and statistical approach of primordial and anthropogenic radionuclides in surface soil of Mami-water site in the Western Cameroon

The study referred to measure activity concentrations of some primordial radionuclides and anthropogenic of 137Cs in soil samples of Mami-water in the Menoua subdivision, Dschang employing gamma-ray spectrometry-based characterized Broad Energy Germanium (BE6350) detector and a comparison of radiological and safety impact parameters on human due to primordial radioactivity in soil with some internationally approved values. In addition, statistical analysis of primordial radionuclides of 226Ra, 232Th and 40K was performed to evaluate the distribution and the interrelation of radionuclides. Samples were randomly collected from a depth of about 0 to 5 cm from the top surface layer. Each of the sampling points was considered as being overlaid with a grid and subdivided into cells. The observed radioactivity level of 226Ra, 232Th and 40K in the investigated soil samples was compared with some published data available in some countries including Cameroon and observed varying within some reported data of radioactivity in soil from bauxite ore deposit. 235U and 137Cs were found in very few samples with a very low average of activity concentrations. In the majority of the samples, the observed radiological safety parameters seem to be greater than the internationally approved values. Consequently, using bricks made of soil as building materials might lead to an increase in radiation risk for the population. Multivariate statistical analysis of activity concentrations of primordial radionuclides performed showed an asymmetrical distribution with more peaked than Gaussian distribution and relatively flatter distribution of radionuclides in soil. In addition, a good positive interrelation between 226Ra and 232Th was observed and a weak negative one observed between 40K and 226Ra–232Th.

Assessment of natural radioactivity and gamma-ray dose in monazite rich black Sand Beach of Penang Island, Malaysia

Activity concentrations of primordial radionuclides in sand samples collected from the coastal beaches surrounding Penang Island have been measured using conventional γ-ray spectrometry, while in-situ γ-ray doses have been measured through use of a portable radiation survey meter. The mean activity concentrations for 226Ra, 232Th and 40K at different locations were found to be less than the world average values, while the Miami Bay values for 226Ra and 232Th were found to be greater, at 1023±47 and 2086±96Bqkg̶ 1 respectively. The main contributor to radionuclide enrichment in Miami Bay is the presence of monazite-rich black sands. The measured data were compared against literature values and also recommended limits set by the relevant international bodies. With the exception of Miami Bay, considered an elevated background radiation area that would benefit from regular monitoring, Penang island beach sands typically pose no significant radiological risk to the local populace and tourists visiting the leisure beaches.

Quantification and Radiological Risk Estimation Due to the Presence of Natural Radionuclides in Maiganga Coal, Nigeria.

Following the increasing demand of coal for power generation, activity concentrations of primordial radionuclides were determined in Nigerian coal using the gamma spectrometric technique with the aim of evaluating the radiological implications of coal utilization and exploitation in the country. Mean activity concentrations of 226Ra, 232Th, and 40K were 8.18±0.3, 6.97±0.3, and 27.38±0.8 Bq kg-1, respectively. These values were compared with those of similar studies reported in literature. The mean estimated radium equivalent activity was 20.26 Bq kg-1 with corresponding average external hazard index of 0.05. Internal hazard index and representative gamma index recorded mean values of 0.08 and 0.14, respectively. These values were lower than their respective precautionary limits set by UNSCEAR. Average excess lifetime cancer risk was calculated to be 0.04×10−3, which was insignificant compared with 0.05 prescribed by ICRP for low level radiation. Pearson correlation matrix showed significant positive relationship between 226Ra and 232Th, and with other estimated hazard parameters. Cumulative mean occupational dose received by coal workers via the three exposure routes was 7.69 ×10−3 mSv y-1, with inhalation pathway accounting for about 98%. All radiological hazard indices evaluated showed values within limits of safety. There is, therefore, no likelihood of any immediate radiological health hazards to coal workers, final users, and the environment from the exploitation and utilization of Maiganga coal.

Radioecological impacts of tin mining.

The tin mining activities in the suburbs of Jos, Plateau State, Nigeria, have resulted in technical enhancement of the natural background radiation as well as higher activity concentrations of primordial radionuclides in the topsoil of mining sites and their environs. Several studies have considered the radiological human health risks of the mining activity; however, to our knowledge no documented study has investigated the radiological impacts on biota. Hence, an attempt is made to assess potential hazards using published data from the literature and the ERICA Tool. This paper considers the effects of mining and milling on terrestrial organisms like shrubs, large mammals, small burrowing mammals, birds (duck), arthropods (earth worm), grasses, and herbs. The dose rates and risk quotients to these organisms are computed using conservative values for activity concentrations of natural radionuclides reported in Bitsichi and Bukuru mining areas. The results suggest that grasses, herbs, lichens, bryophytes and shrubs receive total dose rates that are of potential concern. The effects of dose rates to specific indicator species of interest are highlighted and discussed. We conclude that further investigation and proper regulations should be set in place in order to reduce the risk posed by the tin mining activity on biota. This paper also presents a brief overview of the impact of mineral mining on biota based on documented literature for other countries.

Health and ecological hazards due to natural radioactivity in soil from mining areas of Nasarawa State, Nigeria

Nasarawa State is located in north central Nigeria and it is known as Nigeria's home of solid minerals. It is endowed with barite, copper, zinc, tantalite and granite. Continuous releases of mining waste and tailings into the biosphere may result in a build-up of radionuclides in air, water and soil. This work therefore aims to measure the activity concentration levels of primordial radionuclides in the soil/sediment samples collected from selected mines of the mining areas of Nasarawa State. The paper also assesses the radiological and radio ecological impacts of mining activities on the residents of mining areas and their environment. The activity concentrations of primordial radionuclides (226Ra, 232Th and 40K) in the surface soils/sediment samples were determined using sodium iodide-thallium gamma spectroscopy. Seven major mines were considered with 21 samples taken from each of the mines for radiochemistry analysis. The human health hazard assessment was conducted using regulatory methodologies set by the United Nations Scientific Committee on the Effects of Atomic Radiation, while the radio ecological impact assessment was conducted using the ERICA tool v. 1.2. The result shows that the activity concentrations of 40K in the water ways of the Akiri copper and the Azara barite mines are 60 and 67 % higher than the world average value for 40K, respectively. In all mines, the annual effective dose rates (mSv y−1) were less than unity, and a maximum annual gonadal dose of 0.58 mSv y−1 is received at the Akiri copper mine, which is almost twice the world average value for gonadal dose. The external hazard indices for all the mines were less than unity. Our results also show that mollusc-gastropod, insect larvae, mollusc-bivalve and zooplankton are the freshwater biotas with the highest dose rates ranging from 5 to 7 µGy h−1. These higher dose rates could be associated with zinc and copper mining at Abuni and Akiri, respectively. The most exposed terrestrial reference organisms are lichen and bryophytes. In all cases, the radio ecological risks are not likely to be discernible. This paper presents a pioneer data for ecological risk from ionizing contaminants due to mining activity in Nasarawa State, Nigeria. Its methodology could be adopted for future work on radioecology of mining.

Laboratory measurements of natural radioactivity in selected igneous rocks of the Opava Mountains region

The paper presents results of laboratory gamma–ray measurements of six igneous rocks from the Opava Mountains. The Opava Mountains are located in the Eastern Sudetes and represent their furthest eastern range. They run almost latitudinally along the Polish border with the Czech Republic. The Opava Mountains are situated mostly in the Czech Republic. Only a small fragment between Glucholazy in the west and Prudnik in the east is situated in Poland (Janeczek et al. 1991) . The study area is built of rocks of different ages and lithologies. The Opava Mountains belong to the western part of the Upper Silesia Block, which together with the Brno Block form a structure that is called the Brunovistulicum. The mountains consist of five structural stages: the Žulova Massif, the Desna Series, the Vbrna Series, the Andělska-Hora Formation and the Horn-Benesov Formation, which run longitudinally (Żaba et al. 2005). The activities of naturally occurring radionuclides were measured using a portable GX3020 gamma-ray workstation. The system is based on a high-purity germanium (HPGe) detector with 32% relative efficiency and energy resolutions of 0.8 keV at 122 keV and 1.7 keV at 1330 keV.). The activity concentrations of 40 K varied from 519 Bqkg -1 (paragneiss, Glucholazy/Mikulice) to 1559 Bqkg -1 (weathered granite, Slawniowice), while those of 228 Ac ( 232 Th series) from 7.2 Bqkg -1 (weathered granite, Slawniowice) to 70.6 Bqkg -1 (migmatitic gneiss, Nadziejow). The activities associated with 226 Ra ( 238 U series) ranged from 5.5 Bqkg -1 (weathered granite, Slawniowice) to 52.2 Bqkg -1 (gneiss, Kamienna Gora). Measured activity concentrations were compared with the average activity concentration of 40 K, 228 Ac ( 232 Th) and 226 Ra ( 238 U) for similar types of rocks. For the authors’ knowledge, this paper presents the first experimental data concerning activity concentrations of primordial radionuclides in the igneous rocks in the Opava Mountains.

Natural radioactivity and associated radiation hazards of some commonly used building materials in southwest Nigeria

The activity concentrations of primordial radionuclides ( 40 K, 226 Ra and 232 Th) in five different types of commonly used building materials in southwest Nigeria were measured using a low-background NaI(Tl) detector coupled to an IBM-compatible multichannel analyzer. The highest mean concentration of 40 K, which was 887.5 ± 101.3 Bq.kg -1 , was obtained in gravel. Also, the highest mean concentrations of 226 Ra and 232 Th were obtained, respectively, in sand and brick samples. The lowest mean concentrations of 40 K, 226 Ra and 232 Th, respectively, were obtained in brick and cement sample. The annual gonadal effective dose (AGED) and other radiological parameters were estimated from the activity concentrations of the radionuclides. The highest mean values of the AGED and radium equivalent activity concentration obtained were 359.1 μSv.y -1 and 110.9 Bq.kg -1 , respectively. All these radiological parameters were below the maximum permissible levels recommended for safe use of materials in building construction. It can therefore be concluded that these materials do not pose any radiological hazard to the dwellers of buildings constructed with them.

Background in the context of land contaminated with naturally occurring radioactive material

The financial implications of choosing a particular threshold for clearance of radioactively contaminated land are substantial, particularly when one considers the volume of naturally occurring radioactive material (NORM) created each year by the production and combustion of fossil fuels and the exploitation of industrial minerals. Inevitably, a compromise needs to be reached between the level of environmental protection sought and the finite resources available for remediation. In the case of natural series radionuclides, any anthropogenic input is always superimposed on the inventory already present in the soil; this ‘background’ inventory is conventionally disregarded when assessing remediation targets. Unfortunately, the term is not well defined and the concept of ‘background dose’ is open to alternative interpretations. In this paper, we address the issue of natural background from a geochemical rather than from a solely radiological perspective, illustrating this with an example from the china clay industry. We propose a simple procedure for decision making based on activity concentrations of primordial radionuclides and their progeny. Subsequent calculations of dose need to take into account the mineralogical and chemical characteristics of the contamination, which in the case of NORM are invariably reflected in uranium series disequilibrium.

Environmental radioactivity evaluation in the coastal stretch of Bay of Bengal from Pondycherry to Velanganni (South East coast of India)

Background: Since the Madras Atomic Power Station, Kalpakkam and Kudankulam Nuclear Power Plant, Kudankulam are sited in Bay of Bengal coast, radiological study of this coastal environment is imperative to assess the impact of operation of nuclear power plant, if any, on the radioactivity profile of the coast. Materials and Methods: In the present study the environmental radioactivity was evaluated by measuring activity concentrations of primordial radionuclides namely 238 U, 232 Th and 40 K. in the beach sand samples using high purity germanium gamma ray spectrometry. 10 sampling stations were fixed along a 290 km coastal stretch of Bay of Bengal from Pondycherry to Velangannni. Results: The activity concentration of 238 U is always much less than that of 232 Th and 40 K and it ranged from 9 Bq/kg (Pondicherry coast) to 93 Bq/kg (Karaikal coast). However, 232 Th concentration fluctuated from 12 Bq/kg (Pichavaram Mangrove) to 1075 Bq/kg (Karaikal coast). The activity concentration of 40 K varied within a narrow range from 162 Bq/kg to 474 Bq/kg. The distribution of primordial radioactivity was non-uniform along the entire stretch of Bay of Bengal. The elevated levels of 232 Th were recorded in Karaikal coast (S7) (1075 Bq/kg), Tirumullaivasal coast (S4) (215 Bq/kg), and Nagapattinam coast (S9) (146 Bq/kg) and attributed to the presence of thorium-rich monazite as beach placer in coastal sands. Conclusion: The total absorbed gamma dose contributed by the activity of 238 U, 232 Th, and 40 K varied between 29 nGy/h and 308 nGy/h with a GM value of 64.4 nGy/h. Similarly, the annual effective dose recorded for Bay of Bengal ranged from 0.04 mSv/year to 0.38 mSv/year, indicating that the Bay of Bengal, in general, falls under Normal Background Radiation Area.

Assessment of radiological hazards of clay bricks fabricated in the Punjab province of Pakistan

The Punjab is the most populous among the four provinces of Pakistan, which has around 72 million of people and 205 344 km(2) of land. The majority of the population of this province lives in houses made of clay bricks that contain variable amounts of naturally occurring radioactive material (NORM). The concentration level of NORM in clay bricks used to construct dwellings may pose health hazards to inhabitants if it exceeds the permissible limits. For radiological surveillance, activity concentrations of the primordial radionuclides (40)K, (226)Ra and (232)Th were measured in 140 brick samples collected from 35 districts of the Punjab province. A high-purity germanium gamma-ray detector coupled with a personal computer-based multichannel analyzer was employed for the measurement of activity concentrations of primordial radionuclides in the brick samples. The province-wide average activity concentrations and the range (given in parenthesis) of (40)K, (226)Ra and (232)Th were found to be 624 ± 133 (299-918), 35 ± 7 (21-47) and 42 ± 8 (22-58) Bq kg(-1), respectively. The values lie within the range of activity concentration values for clay bricks of some countries of Asia. Potential radiological constraint was checked in the form of hazard indices calculated from the measured activity concentrations; the indices were found to be less than their limiting values. Indoor external dose was calculated for a standard size room made of clay bricks, and the dose rate was 159 ± 30 (83-219) nGy h(-1). The average value of the dose rate is comparable to that of Asian countries and is about twice the worldwide average value. Annual effective dose E(ff) in the bricks-made room was calculated and the average value of the dose was 0.80 mSv y(-1), which is about twice the worldwide background value of 0.41 mSv y(-1).

Radioactivity in food in Belgrade city

The activity concentrations of 40K, 238U, 226Ra, 232Th and 137Cs were measured using the gamma spectrometric method in different food chain samples from the area of the City of Belgrade during the periods May-June 2007 and May-June 2008. Relatively high activities of 40K and 137Cs were detected in the soil. These results indicate that 137Cs is present in the area of Belgrade even 20 years after the nuclear accident in the Chernobyl nuclear power plant. However, in the samples of feedstuffs, animal products and bio indicators (meat of wild animals and fish), activity concentrations of primordial radionuclides and 137Cs were low and below the detection limits. The results of these trials have shown that investigated animal products from the natural environment around Belgrade are radioactivity safe.

Activity concentrations of primordial radionuclides in sediments of surface – water dams in southwest Nigeria – a baseline survey

The radionuclide contents of sediment samples collected from 20 surface-water dams in southwestern Nigeria have been determined by low-level gamma-spectroscopy. The average concentration of 40 K in each of the dams varied between 110.9 ± 11.9 Bq kg -1 and 1025.9 ± 36.8 Bq kg -1 with an overall mean (± SD) of 549.3 ± 247.6 Bq kg -1 while that of 238 U varied from 17.1 ± 3.6 to 51.9 ± 8.7 Bq kg -1 with an overall mean (± SD) of 27.6 ± 8.5 Bq kg -1 and that of 232 Th varied from 26.2 ± 3.6 Bq kg -1 to 130.1 ± 23.7 Bq kg -1 with overall mean (± SD) of 62.0 ± 26.1 Bq kg -1 . The variability of the values shows the wide disparity in the measured activity concentrations. The mean radium equivalent of 158.9 Bq kg -1 was calculated for the sediments in the dams. No artificial gamma emitting radionuclide was detected in the samples.

Radiometric assessment of natural radioactivity levels of bituminous soil in Agbabu, southwest Nigeria

Activity concentrations of primordial radionuclides ( 226Ra, 232Th and 40K) in bituminous soil samples and viscous bitumen sample from Agbabu bitumen deposit, southwest Nigeria, has been measured using a high-resolution (HpGe detector) γ -spectrometry. The average values of 226Ra, 232Th and 40K obtained are lower than the global average values. The Th/U activity ratio is comparable to values reported in literature. The average absorbed dose rate in outdoor air at a height of 1 m above the ground level was found to be 12.65 ± 3.19 nGy h - 1 , which is below the corresponding worldwide population weighted average value of 60 nGy h - 1 . Both radium equivalent and representative level index values measured are lower than the internationally accepted limits for building and road construction materials. The results of the study indicate that the area has low background radiation level; as such no significant radiological hazard is expected in the area.