Natural Uranium Concentration Research Articles

Use of Biomphalaria glabrata as a bioindicator of groundwater quality under the influence of NORM

The Brazilian northeast is known to have sedimentary areas that contain minerals with anomalous concentrations of naturally occurring radioactive material (NORM). This characteristic can contribute to the elevation of natural radiation in the air, soil, and groundwater. Due to the inefficiency of drinking water distribution in this region, the use of water from wells has become essential for the population. Therefore, the objective of this research was to monitor the concentration of 238U and 232Th associated with biomonitoring with the species of mollusc Biomphalaria glabrata in waters of residential artesian wells, used for domestic consumption, in the municipalities of Abreu e Lima and São José do Sabugi, Brazil. To check the concentration of 238U and 232Th, ICP-MS was used. For biomonitoring, ecotoxicity techniques such as embryotoxicity and genotoxicity were used. The monitoring results confirmed high concentrations of natural uranium in one of the residential artesian wells, the data being above the limit allowed by the Ministry of Health of Brazil, whose study reference is the World Health Organization (WHO). The results of the bioassays showed embryotoxicity, with malformations and deaths in the exposed organisms being observed. The comet assay showed that groundwater caused changes in the mollusc's DNA, indicating genotoxicity. The bioassays suggest that embryotoxicity and genotoxicity were caused mainly by the high concentration of natural uranium. Therefore, the bioindicator B. glabrata was shown to be sensitive to the toxic effects of anomalous concentrations of NORM present in groundwater.

Unconventional uranium in China's phosphate rock: Review and outlook

Some phosphate rock contains elevated concentrations of natural uranium. China is the largest phosphate rock producing country in the world and will soon have the largest uranium requirements in the world as well. Most phosphate rock deposits in China show low uranium concentrations (20–30 mg/kg) so that the recovery of radiotoxic heavy metals is neither economically appropriate nor ecologically necessary. China does, however, also have elevated uranium concentrations (≥90 mg/kg) in phosphate rock deposits in Sichuan and Yunnan. We estimate that China could have recovered nearly 648 metric tU (1.43 million lb U3O8) from those mines in 2016. The amount corresponds to 9.7% of the total reported uranium requirements in this year or 39.3% of reported domestic uranium production in 2016. The future uranium recovery potential may be even higher in total numbers (1158 tU or 3.01 million lb U3O8 in 2030). The main reason are potentially increasing imports of phosphate rock from large exporting countries such as Morocco that show higher average uranium content. In addition, medium- to lower-grade domestic phosphate rock resources with larger shares of accompanying heavy metals, that include rare earths and uranium, will have to be processed. Although the uranium supply for China is currently not at risk, the supply security could be further increased by obtaining unconventional uranium from domestic and imported phosphate rock.

Uranium isotopes concentrations in surface water samples for Al-Manathera and Al-Heerra regions of An-Najaf, Iraq

In this work, the concentrations of natural uranium, uranium isotopes, and the annual effective dose in the surface water for both of Al-Manathera and Al-Heerra regions of An-Najaf, Iraq were determined using a solid state, nuclear track detector, type (CR-39). The results show that the average of uranium concentrations in Al-Manathera and Al-Heerra regions were 1.75 ± 0.202 µg/l and 1.07 ± 0.152 µg/l respectively. The average of activities of 238U, 235U and 234U in Al-Manathera were in 6.48 ± 0.250, 0.100 ± 0.011 and 2.18 ± 0.252 Bq/l, while in Al-Heerra, they were 1.27 ± 0.188, 0.061 ± 0.008 and 1.33 ± 0.189 Bq/l, respectively. The total average of the annual effective dose of natural uranium in all water samples to the adult members of the population for both of Al-Manathera and Al-Heerra regions were 0.152 ± 0.017 µSv/y and 0.093 ± 0.012 µSv/y respectively. In addition, the outcomes demonstrate that uranium levels in the samples of water from Al-Manathera region were far toxic than the samples of Al-Heerra region, as they included uranium levels and total annual effective dose in all water samples of water that comply with the worldwide limits that are approved by International Commission on Radiological Protection (ICRP Publication, Ottawa, 21:1–3; ICRP, Recommendations of the International Commission on Radiological Protection, ICRP Publication, Ottawa, 1990 and Pergamum Press, Oxford; ICRP, Annals of the ICRP. ICRP publication 65, Pergamum Press, Oxford, 1993) which states that safe limits are (1.9 µg/L and 1 mSv/y) respectively. For that reason, one may conclude that the radioactive isotopes are not considered dangerous in case humans consumed it.

THERMOLUMINESCENT DOSIMETRY IN THE EVALUATION OF NATURAL RADIOACTIVITY INDOOR OF HOMES NEAR THE URANIUM DEPOSIT OF PARAÍBA, BRAZIL.

High levels of primordial radionuclides have been reported in soils and rocks of São José de Espinharas, in the state of Paraiba, Brazil. These radionuclides are derived from high concentrations of natural uranium and thorium from a mine in the region. Thus, there is a need for a dosimetric evaluation in the area near the mine and the surrounding cities. In this study, the annual effective dose was analyzed in 178 points of five cities. The measurements were performed using thermoluminescent dosimetry with LiF:Mg, Ti (TLD-100). The annual effective dose from environmental exposure varied from 0.71 to 2.07 mSv, with an arithmetic mean of 0.99 mSv. This average is more than twice the estimated value for indoor environments adopted by the UNSCEAR, which is 0.41 mSv. These results will allow establishing reference values for background radiation of the region and criteria to infer a stochastic risk for the local population.

Comparing of the uranium concentration in tap water samples at Al-Manathera and Al-Herra Regions of Al-Najaf, Iraq

In this work, uranium concentrations and annual effective dose in tap water samples for Al-Manathera and Al-Herra Regions of Al-Najaf, Iraq were determined using a solid-state nuclear track detector (CR-39 detector). Furthermore, we determined the uranium isotopes (238U, 235U and 234U) for all tap water samples under study. The tap water samples are collected nearly from all regions of Al-Manathera and Al-Herra for 22 regions. Thus, the total studied samples are 40. The results indicate that, the average values of uranium concentrations and the annual effective dose in Al-Manathera were larger than the average value at Al-Herra Regions. We concluded that the average value of the uranium concentrations and total average of the annual effective dose in tap waters samples under study were lower than the recommended value of ICRP (1.9 μg/l) and 1 mSv respectively. Therefore, most of the samples could be used without any healthy risk depending on the level of natural uranium concentrations.

Investigating Uranium Concentrations in Groundwaters in the State of Idaho Using Kinetic Phosphorescence Analysis and Inductively Coupled Plasma Mass Spectrometry.

The determination of uranium concentrations in natural water samples is of great interest due to the environmental consequences of this radionuclide. In this study, 380 groundwater samples from various locations within the state of Idaho were analyzed using two different techniques. The first method was Kinetic Phosphorescence Analysis (KPA), which gives the total uranium concentrations in water samples. The second analysis method was inductively coupled plasma mass spectrometry (ICP- MS). This method determines the total uranium concentration as well as the separate isotope concentrations of uranium. The U/U isotopic ratio was also measured for each sample to confirm that there was no depleted or enriched uranium present. The results were compared and mapped separately from each other. The study also found that in some areas of the state, natural uranium concentrations are relatively high.

Natural radioactivity content in Bulgarian drinking waters and consequent dose estimation.

Natural radioactivity in drinking water from Bulgaria was determined in 994 samples. Nine hundred and seventeen of them are from the Southwestern part of the country. The measured activity of natural uranium, (226)Ra, gross alpha and gross beta activity varied from 20 (5) ng l(-1) to 0.11 (3) mg l(-1), MDA to 0.39 (6) Bq l(-1), MDA to 6.23 (39) Bq l(-1) and 0.030 (7) Bq l(-1) to 0.98 (22) Bq l(-1), respectively. Approximately 33% of the investigated waters exceeded a gross alpha activity of 0.1 Bq l(-1), 1.8% a natural uranium concentration of 0.03 mg l(-1) and 1% an (226)Ra concentration of 0.15 Bq l(-1). Annual effective dose from natural radionuclides ranges from 0.0175 (43) µSv to 95.5 (2.6) µSv. Median values of the contribution of the (226)Ra and uranium to the indicative dose are 10.22 and 0.21 µSv y(-1), respectively. Poor relationships between (226)Ra/nat.U (r, 0.12) and for gross beta activity/natural uranium (nat.U) (r, 0.29) were observed. The relationships between nat.U/gross alpha activity (r, 0.50) and for gross alpha activity/gross beta activity (r, 0.52) concentration distributions were stronger.

Determination Uranium Concentrations and Effective Dose of Drinking Water for Nineveh Governorate—Iraq, Using Kinetic Phosphorescence Analyzer (KPA)

In this work, the concentrations of natural Uranium and the annual effective dose (ET in Sv·y-1) in drinking water for Nineveh Governorate in northern Iraq were determined using a pulsed-laser Kinetic Phosphorescence Analyzer (KPA). Furthermore, the relationship between pH for water samples and the concentration of Uranium was studied. The drinking water samples are taken approximately from all regions of Nineveh as; 15 samples of tap water are taken from refinery stations, 13 samples of water samples are taken from wells that are used for drinking, and 18 samples of drinking water are withdrawn from wells in Adayyah region (this region is located near nuclear wastes site). Thus, the total studied samples are 46. The results of Uranium concentration for all samples ranged from 2.61 ± 0.08 to 9.14 ± 0.012 μg·L-1 with an overall average value about 5.87 ± 0.046 μg·L-1, and the total annual effective dose ranged from 2.3 to 8.04 μSv·y-1. The results also showed that the pH number increases with increasing Uranium concentration and have, in general, high values in well water.

Uranium in Kosovo’s drinking water

The results of this paper are an initiation to capture the drinking water and/or groundwater elemental situation in the youngest European country, Kosovo. We aim to present a clear picture of the natural uranium concentration in drinking water and/or groundwater as it is distributed to the population of Kosovo. Nine hundred and fifty-one (951) drinking water samples were analyzed by inductively coupled plasma mass spectrometry (ICPMS). The results are the first countrywide interpretation of the uranium concentration in drinking water and/or groundwater, directly following the Kosovo war of 1999. More than 98% of the samples had uranium concentrations above 0.01μgL−1, which was also our limit of quantification. Concentrations up to 166μgL−1 were found with a mean of 5μgL−1 and median 1.6μgL−1 were found. Two point six percent (2.6%) of the analyzed samples exceeded the World Health Organization maximum acceptable concentration of 30μgL−1, and 44.2% of the samples exceeded the 2μgL−1 German maximum acceptable concentrations recommended for infant food preparations.

Uranium Speciation in Drinking Water from Drilled Wells in Southern Finland and Its Potential Links to Health Effects

Exceptionally high concentrations of natural uranium have been found in drinking water originating from drilled wells in Southern Finland. However, no clear clinical symptoms have been observed among the exposed population. Hence a question arose as to whether uranium speciation could be one reason for the lack of significant adverse health effects. Uranium species were determined using time-resolved laser-induced fluorescence spectroscopy. We performed multi-element chemical analyses in these water samples, and predictive calculations were carried out using up-to-date thermodynamic data. The results indicated good agreement between measurements and modeling. The low toxicity of Finnish bedrockwater may be due to the predominance of two calcium-dependent species, Ca2UO2(CO3)3(aq) and CaUO2(CO3)3(2-), whose nontoxicity for cells has been described previously. This interdisciplinary study describes chemical speciation of drinking water with elevated uranium concentrations and the potential consequence on health. From these results, it appears that modeling could be used for a better understanding of uranium toxicity of drinking water in the event of contamination.

Hafnium and Uranium Contributions to Soft Error Rate at Ground Level

Current technologies are sensitive to low Linear Energy Transfer particles such as alphas. These particles can be spontaneously produced by some radioactive elements, called alpha-emitters. Here, we investigate two examples of emitters, Hafnium and Uranium. By calculating the disintegration rate in a modern technology with hafnium dioxide, we show that hafnium has no incidence on Soft Error Rate. Moreover, from Monte Carlo simulations, we point out that natural Uranium concentration in a silicon wafer lead to a Soft Error Rate comparable to that due to neutrons at ground level.

Rapid measurements of concentrations of natural uranium in process stream samples via gamma spectrometry at an extraction facility

A new application of gamma spectrometry in the efficient measurement of natural uranium in the process stream at an extraction plant is described here. The inherent nuclear properties of uranium viz. emanation of characteristic gamma rays (185.7 keV) has been exploited for the determination of concentrations ranging from 5 to 450 g l −1 by passive photon counting of 185.7 keV gamma rays from 235U isotope for a maximum of 3–10 min per sample. This technique is totally matrix independent unlike other instrumental analytical techniques like wavelength dispersive X-ray fluorescence spectrometry and UV–vis spectrophotometry. Solution samples of aqueous and organic phase can be directly counted without the requirement of sample preparation. A MINIM-based gamma spectrometer consisting of a multichannel pulse height analyzer and a 3 in. × 3 in. well-type NaI(Tl) scintillation detector with an approximately 2 in. thick lead shield has been employed for the measurements. The results are compared with those obtained by potentiometry and wavelength dispersive X-ray fluorescence spectrometry (WD-XRF). Relative standard deviation of 1–5% has been obtained depending upon the concentration of uranium, which is more than adequate for routine process control samples. This paper also discusses in detail the problems associated with the determination of high concentrations of uranium in using 63 and 93 keV gamma rays emanating from 234Th ( t 1/2 24 days) the immediate daughter of 238U isotope in samples that have attained secular equilibrium and the limitations of these energies in the routine analysis of freshly extracted uranium.

Assessment of occupational exposure to uranium by indirect methods needs information on natural background variations

Urine monitoring is the preferred method to determine exposure to soluble compounds of uranium in workplaces. The interpretation of uranium contents in workers bioassay samples requires knowledge on uranium excretion and its dependence on intake by diet. Exceptionally high concentrations of natural uranium in private drinking water sources have been measured in the granite areas of Southern Finland. Consequently, high concentrations of natural uranium have been observed in the urine and hair samples of people using water from their own drilled wells. Natural uranium content in urine and hair samples of family members, who use uranium-rich household water, have been analyzed by using ICP-MS. The uranium concentrations both in urine and hair samples of the study subjects were significantly higher than the world-wide average values. In addition, gammaspectrometric methods have been tested for determining uranium in hair samples. This method can be used only for samples with highly elevated uranium concentrations.

Measurements of natural uranium concentration and isotopic composition with permil‐level precision by inductively coupled plasma–quadrupole mass spectrometry

A new analytical technique using inductively coupled plasma–quadrupole mass spectrometry (ICP‐QMS) has been developed that produces permil‐level precision in the measurement of uranium concentration ([U]) and isotopic composition (δ234U) in natural materials. A 233U‐236U double spike method was used to correct for mass fractionation during analysis. To correct for ratio drifting, samples were bracketed by uranium standard measurements. A sensitivity of 6–7 × 108 cps/ppm was generated with a sample solution uptake rate of 30 μL/min. With a measurement time of 15–20 min, standards of 30‐ng uranium produced a within‐run precision better than 3‰ (±2 R.S.D.) for δ234U and better than 2‰ for [U]. Replicate measurements made on standards show that a between‐run reproducibility of 3.5‰ for δ234U and 2‰ for [U] can be achieved. ICP‐QMS data of δ234U and [U] in seawater, coral, and speleothem materials are consistent with the data measured by other ICP‐MS and TIMS techniques. Advantages of the ICP‐QMS method include low cost, easy maintenance, simple instrumental operation, and few sample preparation steps. Sample size requirements are small, such as 10–14 mg of coral material. The results demonstrate that this technique can be applied to natural samples with various matrices.

INTERNAL DOSE ASSESSMENT OF NATURAL URANIUM FROM DRINKING WATER BASED ON BIOKINETIC MODELING AND INDIVIDUAL BIOASSAY MONITORING: A STUDY OF A FINNISH FAMILY

Since the later 1960's, a nationwide survey on natural radionuclides in drinking water showed high concentrations of natural uranium (U) in Finland, especially in uraniferous granite areas. In order to assess the radiation dose from the natural uranium to individuals, the concentrations of natural uranium in drinking water of the drilled wells were determined by radiochemical and alpha spectrometric methods. Uranium contents were measured in the urinary samples of five members of a Finnish family by means of inductively coupled plasma-mass spectrometry. Correspondingly, theoretical biokinetic modeling of natural uranium incorporated for the same persons were performed with the aid of follow-up interviews. The ICRP biokinetic compartmental model and the age-dependent transfer rates for uranium were used to model the intake, transfer, distribution, retention, and excretion of (234)U and (238)U, respectively, from the drinking water for each person of the family. The organ absorbed dose, equivalent dose, and effective dose were evaluated for each family member at time intervals using specific effective energy values calculated by the SEECAL program and compared with recommended values. The modeled urinary excretion rates were found to be mostly higher than the measured values by a factor of three. The mean annual effective dose for this family is 8 muSv y(-1). By comparing the measured and calculated data, estimation of retrospective radiation exposure based on biokinetic modeling and bioassay method is enhanced and, vice versa, the biokinetic and dosimetric models are tested and verified.

Solubility of UO2HPO4 in seawater

The solubility of UO2HPO4 in normal seawater of 35‰ salinity was studied. The solubility of U(VI) phosphates in seawater increases nonlinearly with decreasing acidity (by two orders of magnitude per pH unit) due to formation of strong hydroxo, carbonate and, probably, phosphate complexes. At pH > 7.5, UO2HPO4 dissolves congruently. With decreasing pH to 6.9–7.2, UO2HPO4 is converted to UO2(H2PO4)2. The solubility of U(VI) phosphates in seawater considerably exceeds the natural uranium concentrations in seawater and pore solutions of the bottom sediments. Therefore, these compounds cannot form intrinsic minerals in the oceanic bottom sediments. The possibility of accumulation of U(VI) in sea phosphorites due to its chemisorption in the form of surface uranyl phosphate complexes is discussed.

(n,f)-radiography as a means to investigate plants for their contamination with natural and technogenic uranium

Plants which grow in an area where uranium mining took place have been investigated for their uranium content by applying neutron-fission radiography [(n,f)-radiography]. The uranium was either assimilated by the plant from uranium-bearing soil or deposited at the leaves by uranium-bearing dust particles. Human activities like mining and refinement of uranium ores release technogenic uranium in the environment and increase the concentration of this α-emitting element. The technogenic uranium contributes to radioactive pollution. In addition to the natural amount of uranium in dust, water and the fertile (humus) soil layer, the technogenic uranium may increase the effect of uranium on the human organism. In order to perform efficient radiation protection, one has to obtain knowledge about the sources of radiation. The discovery of open sources which release uranium to the environment is of great importance because of the large biological effect of the α-particles emitted by the uranium. Leaves, roots and soil have been sampled at different locations in the territory of a former uranium ore mine, in the surrounding area and in a forest at the edge of the city of Ronneburg, where a small plot is known for its high natural uranium concentration. The plastic foil “Lavsan” was used as track detector, and the irradiation was performed with a fluence of 10 16 neutrons cm −2. (n,f)-radiography applied to plants yields information about the presence of local α-emitting sources of uranium and their location. The density of the fission fragment tracks enables the estimation of the uranium concentration.

Fission-track analysis of uranium distribution in granitic rocks

The natural uranium concentration and distribution in three granitoids from Australia has been used to develop an understanding of the geochemical processes which control its behaviour in the natural environment and the potential behaviour of some analogue elements within a crystalline high-level radioactive waste (HLW) repository environment. In the Coles Bay Granite, Olympic Dam granite and the Kambalda Granodiorite, fission-track micromapping has been used to identify primary and secondary distribution between four main mineralogical locales: (1) Background U; (2) Resistate U; (3) Secondary U; and (4) Fracture U. Minor concentrations of total U are present as Background U in the major rock-forming minerals whereas Resistate U, contributed by the accessory minerals, comprises up to 60% of total U. Two modes of redistribution of primary U are evident: (1) in the secondary minerals, particularly Fe- and Ti-hydroxides; and (2) on alteration minerals which infill microfractures. The association of U with these secondary and fracture-infilling minerals indicates that it has been redistributed during post-magmatic hydrothermal alteration and possibly by recent groundwater-rock interaction. The most important geochemical processes involved in this U redistribution include mobilisation and fixation through complex decoupling and redox reactions, and retention by secondary minerals through adsorption and ionic exchange. The effect of these processes upon natural U redistribution may be considered as an analogue of geochemical processes around a HLW repository. This work shows that a degree of post-magmatic alteration of a granite increases the proportion of secondary minerals of high sorption capacity present, which may thus enhance the radionuclide retardation capability of the granitoids.

A direct determination of 239Pu in femtomole range in aquatic solution by neutron activation

A method is presented which facilitates the direct determination of 239Pu in aquatic solution by the (n,f) reaction with reactor neutrons and subsequent gamma spectrometry without chemical elaboration. Trace impurities of water constituent heavy metal elements are simultaneously determined through their (n, γ) reactions. The sensitivity attained by this method is 1.6×10−15 mol/l 239Pu by measuring the fission product pairs 132Te/132I or 140Ba/140La. The trace impurities determined in the range of 10−8∼10−13 mol/l give an insight into the chemical behaviour of Pu in a given water. The natural uranium concentration plays a role to limit the Pu determination on the one hand and to help understanding the chemical behaviour of Pu on the other hand.

Uranium in the superficial sediments of the North Sea

The recent increase in media interest in pollution of the marine environment by radioactive materials, engendered by the accident to the ‘Mont Louis” off the Belgian coast, has prompted us to report the results of a survey of natural uranium concentrations in the surface sediments of the English North Sea. Samples were collected as part of a routine offshore survey that took place between 1971 and 1978, and uranium determinations were performed by delayed newtron activation analysis. The results show that, apart from one or two areas, levels are generally below the average crustal abundance for the major rock types.