Radioactivity concentration in liquid and solid phases of scale and sludge generated in the petroleum industry

Scales and sludge generated during oil extraction and production can contain uranium, thorium, radium and other natural radionuclides, which can cause exposure of maintenance personnel. This work shows how the oil content can influence the results of measurements of radionuclide concentration in scale and sludge. Samples were taken from a PETROBRAS unit in Northeast Brazil. They were collected directly from the inner surface of water pipes or from barrels stored in the waste storage area of the E&P unit. The oil was separated from the solids with a Soxhlet extractor by using aguarras at 90+/-5 degrees C as solvent. Concentrations of 226Ra and 228Ra in the samples were determined before and after oil extraction by using an HPGe gamma spectrometric system. The results showed an increase in the radionuclide concentration in the solid (dry) phase, indicating that the above radionuclides concentrate mostly in the solid material.     

Traces of DU in samples of environmental bio-monitors (non-flowering plants, fungi) and soil from target sites of the Western Balkan region

This paper reports results of gamma and alpha spectrometric measurements for mosses, lichens, fungi and soil samples from areas in the Balkans targeted by depleted uranium (DU). Samples were collected in 2002 and 2003 in the vicinity of several villages, principally Han Pijesak (Bosnia and Herzegovina, hit by DU in 1995) and Bratoselce (South Serbia, hit by DU in 1999) and in lesser numbers from Gornja Stubla, Kosovo (which is identified as a high natural radon/thoron area) and Presevo close to the Kosovo border. In the course of gamma spectrometric measurements some results suggested samples with unusual high uranium contents which might be considered to be a signature for the presence of DU, although many samples had very high detection limits. Alpha spectrometric measurements directly proved the presence of DU for five samples, all from directly targeted places. These were samples of mosses, lichens and soil. For some samples homogeneity tests were applied which showed a rather even distribution of DU in these samples. No trace of DU was found in any sample from a dwelling.     

Radioactivity concentrations and dose assessment for soil samples around Adana, Turkey

The concentrations of natural radionuclides in surface soils around Adana, Turkey were determined using gamma ray spectrometry with an HPGe detector. The natural gamma ray radioactivity of the terrestrial radionuclides in air was calculated throughout different areas of Adana. The average activity concentrations of (238)U, (232)Th and (40)K were found to be 17.6, 21.1 and 297.5 Bq kg(-1), respectively. Outdoor gamma dose measurements in air 1m above ground level were determined by using a portable gamma scintillation detector. The gamma dose measurements in air were taken from the same places where soil samples were taken. Average outdoor gamma dose rates in sample stations were determined as 67 nGy h(-1). The annual effective dose to the public was found to be 82 microSv.     

Measurements of 60Co in spoons activated by neutrons during the JCO criticality accident at Tokai-mura in 1999

Neutron activated items from the vicinity of the place where the JCO criticality accident occurred have been used to determine the fluence of neutrons around the facility and in nearby residential areas. By using underground laboratories for measuring the activation products, it is possible to extend the study to also cover radionuclides with very low activities from long-lived radionuclides. The present study describes gamma-ray spectrometry measurements undertaken in a range of underground laboratories for the purpose of measuring (60)Co more than 2 years after the criticality event. The measurements show that neutron fluence determined from (60)Co activity is in agreement with previous measurements using the short-lived radionuclides (51)Cr and (59)Fe. Limits on contamination of the samples with (60)Co are evaluated and shown to not greatly affect the utility of neutron fluence determinations using (60)Co activation.     

Aerial measurements of artificial radionuclides in Germany in case of a nuclear accident

Gamma-ray spectrometric systems carried by helicopters prove to be indispensable for the surveillance of environmental radioactivity. The aerial measurements are an important tool for rapid and large-scale nuclide specific determination of soil contamination after an accidental release of radionuclides from a nuclear facility. Furthermore this technique is also applied for the determination of anomalies of elevated radioactivity of natural radionuclides, the detection of lost radioactive sources and geological mapping. For the measurements the helicopters are equipped with a NaI(Tl)-detector array and a high purity germanium-semiconductor (HPGe) detector. Especially with the HPGe-detector it is possible to clearly identify individual radionuclides. To improve and to guarantee the quality of this method several exercises with different fields of interest have been carried out during the last years. Thereby the main focus is on the improvement of the instrumentation, data handling and data analysis. The results of the airborne radionuclide measurements from the Black Forest which was performed in co-operation with the Swiss National Emergency Operation Centre, are presented here. During this exercise the gamma dose rate, soil contamination due to 137Cs and the specific activities of natural radionuclides in soil were determined.     

Elevated concentrations of primordial radionuclides in sediments from the Reedy River and surrounding creeks in Simpsonville, South Carolina

A gamma-ray survey and analysis of 16 riverbed samples from the Reedy River watershed near Simpsonville, SC were conducted and compared with national and international studies of primordial radionuclides. The study reported here follows on a recent discovery of anomalously high uranium concentrations in several private well waters in the area. An HPGe spectrometer was used for quantification of gamma emitting radionuclides in the sediments. All sediments contained radionuclides from the uranium and thorium series as well as (40)K. Uranium-238 concentrations in sediment samples ranged from 11.1 to 74.2Bqkg(-1). The measured radionuclide concentrations were compared with data from UNSCEAR and NURE reports. The river and stream sediment data were augmented by in situ NaI(Tl) gamma-ray spectrometer measurements. Comparisons between the ex situ and in situ measurements indicate equivalently distributed uranium in the surface soils and stream sediments, the source of which is likely attributed to the monazite belts that are known to exist in the area.     

Concentration of radionuclides in hydrosphere affected by Temelín Nuclear Power Plant in Czech Republic

The paper presents results of a long-term field study of the possible impact of Temelín NPP on the Vltava and Elbe Rivers. The study was divided into 2 stages: before and after the operation of the NPP. The main goal of the investigation before the operation (1989–2000) was to determine the background levels of radionuclides resulting from the tests of nuclear weapons and the Chernobyl accident for different components of the environment. The paper discusses also the risk of a river radioactive contamination due to the tritium discharges in wastewater from Temelín NPP. During the operation period of 2001–2006, the results of the monitoring did not detect any impact of Temelín NPP on the concentrations of activation and fission products in the hydrosphere, apart from tritium. The annual average tritium concentrations in the Vltava River correspond with the previously calculated predictions for the conditions of the average and minimum guaranteed flows. The maximum concentration of tritium of 26.6 Bq/l in Vltava River at Prague was observed after dry period in 2003.     

Natural radioactivity in phosphates, phosphogypsum and natural waters in Morocco

The contents of natural radionuclides (uranium, actinium and thorium series) were measured in sedimentary phosphate rock samples using high-resolution gamma spectrometry. Data obtained for uranium content (ppm) were compared with the results obtained by a method based on the measurements using solid-state nuclear track detectors (SSNTD) in the same samples. The potential leaching of radionuclides from sedimentary phosphate rock during the industrial production of the phosphoric acid was studied. The process of leaching of the radioisotopes from phosphogypsum was discussed. A method for the direct alpha counting of 226Ra thin source, elaborated by the deposition of Ra from aqueous solutions on manganese oxides film deposited on polyvinyl support, have been developed and applied for the determination of 226Ra in natural water samples. The results show that only the water sample from the mine area reveals the presence of 226Ra at a level of about 0.2 Bq l-1.     

Present status of 222Rn in groundwater in Extremadura

Radon-222 was measured in groundwater sources of Extremadura (Spain), analyzing 350 samples from private and public springs, wells, and spas by liquid scintillation counting (LSC) and gamma spectrometry. The (222)Rn activity concentrations ranged from 0.24 to 1168BqL(-1). The statistical analysis showed a log-normal distribution with a mean of (111+/-7)BqL(-1) and a median of (36+/-3)BqL(-1). A hydrogeological study revealed correlations between the activity concentration and the aquifer material's characteristics. A map of (222)Rn in groundwater was elaborated and compared with the natural gamma radiation map for this region. About 35% of the samples showed (222)Rn activity concentrations above the Euratom recommended limit of 100BqL(-1). Three uranium series radionuclides ((238)U, (234)U, and (226)Ra) were also assayed by alpha-particle spectrometry, estimating the annual effective dose due to the presence of these natural radionuclides in drinking water.     

Occurrence and behaviour of radionuclides in the Moselle River—Part III: Dispersion of radionuclides along the river course

Knowledge about propagation of radionuclides from nuclear power plants (NPPs) along the course of a river is of great interest in radioecological assessments. By use of a model previously applied in the cases of the Rhine and Weser Rivers, the distribution of various radionuclides released into the Moselle from the NPP Cattenom at normal operation is described with ⁵⁸Co, ⁶⁰Co and ^110mAg as tracers. A comparison of field measurements with calculated values revealed that the radionuclide concentrations in suspended matter and nuclide loads calculated from emission rates agreed with the measured data by a factor of less than two on average.Radionuclide concentrations and loads along the river course decrease mainly due to deposition of particulate radioactive matter in high-sedimentation areas and due to dilution with uncontaminated material from tributaries and other sources. The rate constants of both processes were evaluated, and the mean range of suspended radioactive particles in the Moselle was estimated. Moreover, this study showed anew that suspended matter has to be considered as the main carrier by which the radionuclides from NPPs may be transported over long distances.     

Deposition of gamma emitters from Chernobyl accident and their transfer in lichen-soil columns

Lichen-soil column samples were taken from several locations in the Southern Finland between 1986 and 2006. Columns were divided into three parts, upper lichen, lower lichen and underlying soil, and their gamma emitting radionuclides, (134)Cs, (137)Cs, (103)Ru, (95)Zr, (106)Ru, (110m)Ag, (125)Sb and (144)Ce, were measured with gamma spectrometry. Deposition values were calculated as Bq/m(2) for each sampling site. Distribution of various radionuclides in the three compartments as a function of time was determined. Both effective and ecological half-lives of all radionuclides were calculated for upper lichen, whole lichen and whole lichen-soil column. A linear relation was derived between the physical half-lives and effective half-lives for whole lichen and for whole lichen-soil column. Reindeer meat activity concentrations of various radionuclides and ensuing radiation doses to reindeer-herding people were also estimated for a hypothetical case where a similar high radioactive pollution, as was taken place in the Southern Finland, would have occurred in the reindeer-herding areas in the Finnish Lapland.     

Radioactivity in trinitite six decades later

The first nuclear explosion test, named the Trinity test, was conducted on July 16, 1945 near Alamogordo, New Mexico. In the tremendous heat of the explosion, the radioactive debris fused with the local soil into a glassy material named Trinitite. Selected Trinitite samples from ground zero (GZ) of the test site were investigated in detail for radioactivity. The techniques used included alpha spectrometry, high-efficiency gamma-ray spectrometry, and low-background beta counting, following the radiochemistry for selected radionuclides. Specific activities were determined for fission products (90Sr, 137Cs), activation products (60Co, 133Ba, 152Eu, 154Eu, 238Pu, 241Pu), and the remnants of the nuclear fuel (239Pu, 240Pu). Additionally, specific activities of three natural radionuclides (40K, 232Th, 238U) and their progeny were measured. The determined specific activities of radionuclides and their relationships are interpreted in the context of the fission process, chemical behavior of the elements, as well as the nuclear explosion phenomenology.     

Radiological maps for Trabzon, Turkey

The activity concentrations and absorbed gamma dose rates due to primordial radionuclides and ¹³⁷Cs have been ascertained in 222 soil samples in 18 counties of the Trabzon province of Turkey using a HPGe detector. The mean activity concentrations of ²³⁸U, ²³²Th, ⁴⁰K and ¹³⁷Cs in soil samples were 41, 35, 437 and 21 Bq kg⁻¹, respectively. Based on the measured concentrations of these radionuclides, the mean absorbed gamma dose in air was calculated as 59 nGy h⁻¹ and hence, the mean annual effective dose due to terrestrial gamma radiation was calculated as 72 μSv y⁻¹. In addition, outdoor in situ gamma dose rate (D) measurements were performed in the same 222 locations using a portable NaI detector and the annual effective dose was calculated to be 66 μSv y⁻¹ from these results. The results presented in this study are compared with other parts of Turkey. Radiological maps of the Trabzon province were composed using the results obtained from the study.     

Determination of indoor radon and soil radioactivity levels in Giresun, Turkey

Indoor radon survey and gamma activity measurements in soil samples were carried out in the Giresun province (Northeastern Turkey). The result of analysis of variance showed a relationship between indoor radon and radium content in soil (R(2)=0.54). It was found that indoor radon activity concentration ranged from 52 to 360 Bq m(-3) with an average value of 130 Bq m(-3). A model built by BEIR VI was used to predict the number of lung cancer deaths due to indoor radon exposure. It was found that indoor radon is responsible for 8% of all lung cancer deaths occurring in this province. (137)Cs activity concentration was measured 21 years after the Chernobyl accident. The results showed that (137)Cs activity concentration ranged from 41 to 1304 Bq kg(-1) with an average value of 307 Bq kg(-1). The indoor radon results and the geology of the studied area were discussed. Annual effective doses to the both radionuclides of natural origin and (137)Cs were estimated.     

The importance of physico-chemical parameters on the speciation of natural radionuclides in riverine ecosystems

External gamma radiation levels were measured in the catchment areas of the Sharavathi River and the dose rates in air were found to be in the range 26.0-61.0 nGy h⁻¹. Soil and sediment samples of the riverine environment were analysed for natural radionuclides such as ²²⁶Ra, ²³²Th and ⁴⁰K using a NaI(Tl) gamma spectrometer. The activity concentration of ²¹⁰Pb and ²¹⁰Po in soil and sediment samples was determined by radiochemical separation techniques. Evaluation of the activity concentration of radionuclides with grain size revealed an increase in the activity of ²²⁶Ra, ²³²Th and ⁴⁰K towards fine grain size. The activity concentrations for all isotopes in all samples were not significantly correlated with pH. However, the activity of ²¹⁰Po and ²¹⁰Pb in sediment showed a moderate positive correlation with organic matter content and a good correlation with clay content of sediment.     

Natural radioactivity in some major rivers of coastal Karnataka on the southwest coast of India

Systematic studies on radiation level and distribution of radionuclides have been carried out in riverine environs of three major rivers of coastal Karnataka, viz. Kali, Sharavathi and Netravathi. The ambient gamma radiation levels along three rivers were measured using a portable plastic scintillometer. Activity concentrations of (226)Ra, (232)Th and (40)K in soil, sediment and rock were measured using a NaI(Tl) gamma-ray spectrometer. In the Kali, Sharavathi and Netravathi riverbanks, the median values of absorbed gamma dose rates in air were found to be 44 nGy h(-1), 35 nGy h(-1) and 57 nGy h(-1), respectively. The highest activity of (226)Ra was found in riverbank soil samples of Sharavathi River. The highest activities of (232)Th and (40)K were found in riverbank soil and sediment samples of Netravathi River. In Kali River, the highest (226)Ra activity was recorded for rock samples. To assess the radiological hazard of natural radioactivity in the samples, absorbed gamma dose rates in air, radium equivalent activity, representative level index, external hazard index and internal hazard index associated with the radionuclides were calculated and compared with internationally recommended values. The representative level index (I(gammar)) values are high in sediment samples of Netravathi River. The radium equivalent activity (Ra(eq)), external hazard index (H(ex)) and internal hazard index (H(in)) values are high in rock samples of Kali River. The results of these investigations are presented and discussed in this paper.     

Natural radioactivity in farm soil and phosphate fertilizer and its environmental implications in Qena governorate, Upper Egypt

Samples of phosphate fertilizers and farm soils, taken to a depth of up to 30 cm in cultivated land, were collected over the Qena governorate, Upper Egypt. Activity concentration of background radionuclides such as (226)Ra, (232)Th and (40)K of these samples were determined by gamma-ray spectrometry. The results show that these radionuclides were present in concentrations of 366+/-10.5, 66.7+/-7.3 and 4+/-2.6 Bq/kg for phosphate fertilizers. For farm soil and Nile island's soil the corresponding values were 13.7+/-7, 12.3+/-4.6, 1233+/-646 and 11.9+/-6.7, 10.5+/-6.1, 1636+/-417 Bq/kg, respectively. The radium equivalent activity (Ra(eq)), the representative level index, I(gamma r), and absorbed dose in air for all samples were calculated. The data were discussed and compared with those given in the literature.     

Urban dose rates at Gävle, Göteborg and Lund

Besides gamma rays from ¹³⁷Cs emanating from the Chernobyl accident, gamma rays from natural radionuclides are a dominant source of radiation exposure to the public. Since people spend much more time indoors than outdoors the radiation dose obtained inside dwellings contributes greatly to individual and collective doses. Dose rate measurements were made at 20 locations within the city of Göteborg and at further 22 reference sites within a radius of 100 km. Measurements were also made at Gävle and Lund. The dose rates were measured with RNI intensimeters, TLD (LiF) meters and in in situ measurements using an HPGe. The ground cover was grass, asphalt, concrete slates or paving-stones. The dose rates varied between 0.05 and 0.25 μSv/h. Also performed in different ways, measurements made inside and outside buildings at both Göteborg and Gävle showed inside dose rates higher than outside dose rates.     

Accumulation and distribution of90Sr and137Cs in birch in the zone affected by liquid discharge from the Beloyarskaya Nuclear Power Plant

The data are presented that concern the accumulation and distribution of artificial radionuclides (⁹⁰Sr and¹³⁷Cs) in the aboveground organs of birch growing in the vicinity of the Beloyarskaya Nuclear Power Plant (NPP) in the permanently inundated part of the Ol'khovka swamp, on its banks periodically flooded with water, and in watershed areas not influenced by the swamp (control). Concentrations of both radionuclides in birch trees from the swamp and its banks were several times as high as in trees from the watershed. The distribution of⁹⁰Sr in birch trunk proved to be acropetal. Trees growing on the inundated part of the swamp and on dry land significantly differed in the distribution of¹³⁷Cs. The factors controlling the distribution and accumulation of both radionuclides in birch trees growing in these areas are discussed.     

Estimation of annual effective dose due to natural radioactive elements in ingestion of foodstuffs in tin mining area of Jos-Plateau, Nigeria

Soils and food crops from a former tin mining location in a high background radiation area on the Jos-Plateau, Nigeria were collected and analyzed by gamma spectrometry to measure their contents of 40K, 238U and 232Th. As well as collecting samples, in situ dose rates on farms were measured using a precalibrated survey meter. Activity concentrations determined in food crops were compared with the local food derivatives or diets to investigate the possible removal or addition of radionuclides during food preparation by cooking or other means. Potassium-40 was found to contribute the highest activity in all the food products. The activity concentration of 40K, 238U and 232Th in local prepared diets ranged between 60 and 494 Bq kg-1, between BDL and 48 Bq kg-1 and between BDL and 17 Bq kg-1, respectively. The internal effective dose to individuals from the consumption of the food types was estimated on the basis of the measured radionuclide contents in the food crops. It ranged between 0.2 microSv y-1 (beans) and 2164 microSv y-1 (yam) while the annual external gamma effective dose in the farms due to soil radioactivity ranged between 228 microSv and 4065 microSv.