High Uranium Content Research Articles

Chemical aspects of uranium behavior in soils: A review

Uranium has varying degrees of oxidation (+4 and +6) and is responsive to changes in the redox potential of the environment. It is deposited at the reduction barrier with the participation of biota and at the sorption barrier under oxidative conditions. Iron (hydr)oxides are the strongest sorbents of uranium. Uranium, being an element of medium biological absorption, can accumulate (relative to thorium) in the humus horizons of some soils. The high content of uranium in uncontaminated soils is most frequently inherited from the parent rocks in the regions of positive U anomalies: in the soils developed on oil shales and in the marginal zone of bogs at the reduction barrier. The development of nuclear and coal-fired power engineering resulted in the environmental contamination with uranium. The immobilization of anthropogenic uranium at artificial geochemical barriers is based on two preconditions: the stimulation of on-site metal-reducing bacteria or the introduction of strong mineral reducers, e.g., Fe at low degrees of oxidation.

청원지역 시추공 지하수의 수리화학 및 자연방사성물질 산출 특성

A test borehole was drilled in the Cheongwon area to investigate the relationship between geochemical environment and the natural occurrence of radioactive materials (uranium and Rn-222) in borehole groundwater. The borehole encountered mainly biotite schist and biotite granite, with minor porphyritic granite and basic dykes. Six groundwater samples were collected at different depths in the borehole using the double-packed system. The groundwater pH ranges from 5.66 to 8.34, and the chemical type of the groundwater is Ca-. The contents of uranium and Rn-222 in the groundwater are 0.03-683 ppb and 1,290-7,600 pCi/L, respectively. The contents of uranium and thorium in the rocks within the borehole are 0.51-23.4 ppm and 0.89-62.6 ppm, respectively. Microscope observations of the rock core and analyses by electron probe microanalyzer (EPMA) show that most of the radioactive elements occur in the biotite schist, within accessory minerals such as monazite and limenite in biotite, and in feldspar and quartz. The high uranium content of groundwater at depths of -50 to -70 m is due to groundwater chemistry (weakly alkaline pH, an oxidizing environment, and high concentrations of bicarbonate). The origin of Rn-222 could be determined by analyzing noble gas isotopes (e.g., and ).

Uranium in natural waters sampled within former uranium mining sites in Kazakhstan and Kyrgyzstan

New data are presented on 238U concentrations in surface and ground waters sampled at selected uranium mining sites in Kazakhstan and Kyrgyzstan and in water supplies of settlements located in the vicinity of these sites. Radiochemical neutron activation analysis (RNAA) was used for 238U determination in all cases. In addition, for data accuracy assessments purposes, a sub-set of these samples was analysed by high-resolution alpha spectrometry, following standard radiochemical separation and purification. Our data show that drinking waters sampled at various settlements located close to the uranium mining sites are characterised by relatively low uranium concentrations (1.9–35.9 μg L−1) compared to surface waters sampled within the same sites. The latter show high concentrations of total uranium, reflecting the influence from the radioactive waste generated as a result of uranium ore production.

Nuclear safety of spent fuel pool storage at nuclear power plants with VVER-1000: physical principles and structural solutions

The physical principles and structural solutions concerning nuclear safety in handling nuclear fuel at nuclear power plants with VVER-1000 are examined. It is shown that a structure of storage racks in the holding pools based on the spacing of hexahedral boron steel pipes, the structure acting as a combined neutron trap, will increase the pool capacity as compared with the loosely packed pools and will make the handling of nuclear fuel nuclear safe under normal operating conditions and during accidents. In the future, this construction will make it possible to use fuel assemblies with high uranium content and fuel enrichment above 5%.

Using pegmatite geochronology to constrain temporal events in the Adirondack Mountains

U-Pb laser ablation–multicollector–inductively coupled plasma–mass spectrometry (LA-MC-ICP-MS) ages have been determined from large zircon crystals separated from pegmatites of the Adirondack Mountains, New York. Emplacement and metamorphic ages ranging from 949 ± 10 to 1222 ± 12 Ma help constrain the timing of igneous, metamorphic, and deformational history of the region, and are associated with Shawinigan, Ottawan, and Rigolet orogenesis. Geologically reasonable ages were obtained from most zircon separates despite large size, a limited number of grains, high uranium and thorium contents, dark and opaque interiors, high density of fractures, and widespread areas of metamictization and Pb loss. However, few grains show zoning or differences in composition when viewed with the backscattered mode on the scanning electron microscope. Large, clear, internally featureless, U-poor grains yield the best constrained ages. U-Th-Pb monazite ages, determined by electron probe, vary from 874 ± 27 Ma to 297 ± 62; the younger age may reflect the timing of hydrothermal fluid infiltration related to late Acadian events. This study suggests that, with appropriate care, zircons from pegmatites are a reasonable target for LA-MC-ICP-MS geochronology, widening the current arsenal of sampling targets.

Assessment of Natural Uranium in the Ground Water around Jaduguda Uranium Mining Complex, India

Ground water ecosystem surrounding the uranium processing facility at Jaduguda, India has been studied for natural uranium distribution. Annual intake of uranium through drinking water for members of public residing around the uranium complex is found to be in the range of 41.8 Bq·y –1 - 44.4 Bq·y –1 . The intake and ingestion dose is appreciably low (<2 Sv·y –1 ) which is far below the WHO recommended level of 100 Sv·y –1 . The excess life time radiological risk due to uranium natural in drinking water is insignificant and found to be of the order of 10 –6 . Even the highest concentration of uranium was found to be 28 g·l –1 is away (at 1.5 to 5 km distance) from mining industry and well below the acceptable limit. The ground water in the area around the uranium facility is not affected by the mining activity. The ground water in three zones is safe and reflects the natural distribution of uranium.

A216 金属ウラン・ジルコニウムマトリックス燃料の特性に関する研究(OS8 高温ガス炉・高速炉・金属燃料)

The metallic uranium fuel with the metallic zirconium matrix (METMET fuel) is a dispersion type of fuel, and has been developed in A.A. Bochvar Institute, Russia. The primary advantages of METMET fuel are higher uranium content by 33% more than that of UO_2 fuel, low operation temperature of the fuel, and the extension of the core life. The nuclear characteristics of the small reactor with METMET fuel have been studied. As a feasibility calculation, we evaluated burn-up characteristics of METMET fuel and UO_2 fuel in pin cell geometry for comparison using calculation code SRAC2006. The result shows that the core life with METMET fuel is extended by up to 1.4 times longer. Furthermore, we investigated the core characteristics of a small reactor with METMET fuel. The concept of this small reactor is that the excess reactivity is suppressed during the cycle by initially loading the burnable poison, Gd_2O_3 in the fuel. This core resulted in 9.6 effective full power years as the core life, and the excess reactivity was less than 5%Δk/k during the whole core life.

Determination of Uranium in Rocks and Soils of South Cameroon by γ-ray Spectrometry

Analytical results of uranium concentration in rocks and soils collected in the area of Lolodorf of South Cameroon where a radiometric anomaly had been found by previous investigation are reported. The analysis has been carried out by γ-ray spectrometry using a Ge detector. Radioactivity concentration of 235U was determined by comparing peak count rates of samples with those of natural uranium standard sample. Radioactivity concentration of 238U was calculated from the 235U radioactivity concentration by assuming that the isotopic composition of 235U is 0.7200% of natural abundance. Difference of γ-ray self-absorption between the samples and uranium standard was accurately corrected by using a mass attenuation coefficient of samples and standard measured by using an external γ-ray source. The radioactivity concentrations in rocks ranged from 0.92±0.02 to 228±14Bq/kg(235U) and 20±5 to 4868±307Bq/kg(238U), while radioactivity concentrations in soils ranged from 3±1 to 63±2 Bq/kg(235U) and 71±19 to 1346±38 Bq/kg(238U). The γ-ray dose rates in air at 1m above the ground surface due to the high uranium concentration in soil samples were ranged from 33±9 to 622±18 nGy/h. The highest uranium concentration of about 0.04% in rock was found in the analysis. These results show that the uranium content in the studied areas is significantly high and the studied areas have a potential for uranium mining.

Distribution of uranium isotopes in surface water of the Llobregat river basin (Northeast Spain)

A study is presented on the distribution of 234U, 238U, 235U isotopes in surface water of the Llobregat river basin (Northeast Spain), from 2001 to 2006. Sixty-six superficial water samples were collected at 16 points distributed throughout the Llobregat river basin. Uranium isotopes were measured by alpha spectrometry (PIPS detectors). The test procedure was validated according to the quality requirements of the ISO17025 standard. The activity concentration for the total dissolved uranium ranges from 20 to 261 mBq L −1. The highest concentrations of uranium were detected in an area with formations of sedimentary rock, limestone and lignite. A high degree of radioactive disequilibrium was noted among the uranium isotopes. The 234U/ 238U activity ratio varied between 1.1 and 1.9 and the waters with the lowest uranium activity registered the highest level of 234U/ 238U activity ratio. Correlations between uranium activity in the tested water and chemical and physical characteristics of the aquifer were found.

Radioanalytical investigations of uranium concentrations in natural spring, mineral, spa and drinking waters in Hungary

Within this work, the activity concentrations of uranium isotopes (234U, 235U, and 238U) were analyzed in some of the popular and regularly consumed Hungarian mineral-, spring-, therapeutic waters and tap waters. Samples were selected randomly and were taken from different regions of Hungary (Balaton Upland, Bukk Mountain, Somogy Hills, Mezőfold, and Lake Heviz). Concentration (mBq L−1) of 234U, 235U, and 238U in the waters varied from 1.1 to 685.2, from <0.3 to 7.9, and from 0.8 to 231.6 respectively. In general, the highest uranium concentrations were measured in spring waters, while the lowest were found in tap waters. In most cases radioactive disequilibrium was observed between uranium isotopes (234U and 238U). The activity ratio between 234U and 238U varies from 0.57 to 4.97. The calculated doses for the analyzed samples of spring water are in the range 0.07–32.39 μSv year−1 with an average 4.32 μSv year−1. This is well below the 100 μSv year−1 reference level of the committed effective dose recommended by WHO and the EU Council. The other naturally occurring alpha emitting radionuclides (226Ra and 210Po) will be analyzed later to complete the dose assessment. This study provides preliminary information for consumers and authorities about their internal radiological exposure risk due to annual intake of uranium isotopes via water consumption.

Singular opportunity for unique insights into the nature of space/earth natural radiation effects on human brain disorders: International interdisciplinary approach

Non-coring based exploratory drilling was under taken in the sedimentary environment of Rangsohkham block, East Khasi Hills district to examine the eastern extension of existing uranium resources located at Domiasiat and Wakhyn in the Mahadek basin of Meghalaya (India).Although radiometric survey and radiometric analysis of surface grab/channel samples in the block indicate high uranium content but the gamma ray logging results of exploratory boreholes in the block, did not obtain the expected results. To understand this abrupt discontinuity between the two sets of data (surface and subsurface) multivariate statistical analysis of primordial radioactive elements (K40, U238 and Th232) was performed using the concept of representative subsurface samples, drawn from the randomly selected 11 boreholes of this block.The study was performed to a high confidence level (99%), and results are discussed for assessing the U and Th behavior in the block. Results not only confirm the continuation of three distinct geological formations in the area but also the uranium bearing potential in the Mahadek sandstone of the eastern part of Mahadek Basin.

VVER-440 fuel cycles based on fuel assemblies with larger uranium loads and higher uranium content

A long series of computational works validating possibilities for improving of VVER-440 fuel cycles has been completed at the Russian Science Center Kurchatov Institute. Work was performed on upgrading and improving VVER-440 fuel cycles on the basis of second-generation fuel assemblies which make it possible to increase the thermal power to 107-108% nominal 1375 MW(t) while preserving the operating time of the fuel loads. Fuel cycles based on second-generation fuel assemblies with a larger fuel load and average fuel enrichment to 4.87% are now under development. The fuel load in fuel assemblies is enlarged by eliminating the central opening in the fuel pellet of a fuel element and increasing the pellet diameter by decreasing the cladding thickness. The present article summarizes the work done on upgrading VVER-440 fuel cycles and shows the possibility and prospects for further improving the neutron-physical and operational characteristics of reactors by additionally optimizing fuel-assembly design and fuel-load arrangement.

The Impact of an Abandoned Uranium Mining Area on the Contamination of Agricultural Land in its Surroundings

This paper focuses on the influence of uranium tailing piles on the contamination of their immediate surroundings. The monitoring was carried out on arable land near Pribram in Central Bohemia, Czech Republic. The monitored arable land is located 600 m northeast of the bottom of the piles. In addition, the high uranium (U) content in the topsoil ranged from 40 to 220 ppm. A former portion of it was found in an exchangeable fraction (49%). Both of these facts make this land unsuitable for agricultural use. The sequential extraction discovered a shift in the U content among sample spots situated in and outside the path of the predominant wind direction. In the first group, uranium binds mainly to Fe/Mn oxides, while in the other samples, U is accumulated in the more mobilizable fractions.

On the influence of faulting on small-scale soil-gas radon variability: a case study in the Iberian Uranium Province

In order to evaluate the influence of faulting on the variability of geogenic radon at detailed scale (1:2000), data on gamma ray fluxes, U and Th concentrations in rocks, radon in soil-gas and radon in groundwater were collected in three target areas on the Oliveira do Hospital region (Central Portugal). This region stands on the Iberian Uranium Province, and is dominantly composed of Hercynian granites and metasedimentary rocks of pre-Ordovician age, crosscut by faults with dominant strike N35°E, N55°E and N75°E. Radiometric anomalies are frequent, associated with faults of the referred systems and metasedimentary enclaves; the analytical data confirms that these anomalies are produced by local high uranium contents in rocks and fault-filling materials ( n = 34, range 13–724 ppm), while other radiogenic elements are relatively constant (e.g. Th 4–30 ppm). Radon concentration in soil can be extremely high, up to 12,850 kBq m −3 ( n = 215), with a large proportion of results above 100 kBq m −3. Unsurprisingly, groundwater also shows high radon concentrations, with observed values in the range 150–4850 Bq.L −1 ( n = 17). From the results it is concluded that metasedimentary enclaves, as well as faults, can accumulate uranium from circulating fluids, and as a consequence, strongly locally enhance geogenic radon potential. Due to this fact, for the purpose of land use planning in such uranium-enriched regions, very detailed geological mapping is needed to precisely recognize radon high risk areas. A correlation between radon concentration in soil or in groundwater and gamma ray fluxes was established pointing to the possible use of these fluxes as a first step in assessing geogenic radon potential, at least to geological setting similar to the study area.

U-Pb (SIMS SHRIMP-II) age of volcanic rocks from the Tulukuev caldera (Streltsov Uranium-Ore Cluster, Eastern Transbaikalia)

The precision dating (U-Pb local by zircons, SHRIMP-II) of volcanic rocks in the unique uranium-bearing structure of Transbaikalia is performed for the first time. The basic conclusions are as follows. The volcanic activity in the Tulukuev caldera covers the period of not less than 30–35 mln years, within the period from (not later than) 162 to 128 mln years. Two stages of caldera evolution are established: the early (trachydacite-basalt) stage up to 154 mln years and the late (trachybasalt-rhyolite) stage from 142 to 128 mln years, with a 10 mln year break, which caused the deep erosion of the lower layer. Three phases of rhyolite magmatism are substantiated. The first one, 142 mln years, is the ejection of ignimbrites (microfelsitic rhyolites); the second one, 137–135 mln years, is the outflow of lavas of sanidine-morion rhyolites and subvolcanic and ring dyke intrusions. The third phase, 128 mln years, is connected with the occurrence of cesium-bearing perlites in the southwestern part of the caldera. The age of the granite-porphyries of the Krasnokamensk stock almost coincides with the precision data of the age of the uranium ores [4]. It is found that zircons from the granite-porphyries within the ore field of the Argunsk deposit have an anomalously high content of uranium. This fact can additionally testify to the time-and-spatial closeness of magmatism and processes of ore formation.

Shallow Groundwater and Cultivated Soil Suitability Assessments with Respect to Heavy Metal Content in the Köprübaşı U Mineralization Area (Manisa, Turkey)

Shallow groundwater and cultivated soil samples were collected from the area within Köprübaşi U mineralization and analyzed to determine U and selected heavy metals (Fe, Mn, Cu, As, Pb, Zn, Cr, Co and Ba). After this, the suitability of the shallow groundwater and soil samples were evaluated for irrigation, livestock watering and agricultural use, respectively. One groundwater sample (4) showed Mn-concentration of 112.6, exceeding the FAO (Ayers and Westcot 1985) livestock drinking limit (50 microg/l). Nevertheless, the amount of heavy metals including Fe, Cu, As, Pb, Zn, Cr and Co in groundwater is not high for irrigation and livestock drinking water standards cited by the FAO (Ayers and Westcot 1985). On the other hand, all cultivated soil samples have higher uranium concentrations than the typical concentration of natural uranium in soil (ATSDR 1999). The majority of the cultivated soil samples showed higher concentrations than the values for heavy metals (Fe, Mn, Cu, As, Pb, Zn, Cr, Co, Ba) found in normal soils of the world (Connor and Shacklette 1975). However, according to G.L.C guidelines, these soils are classified as uncontaminated with Mn, Cu, Pb, Zn and Cr, slightly contaminated with Ba and As.

Biomonitoring of environmental pollution by thorium and uranium in selected regions of the Republic of Kazakhstan

Two former uranium mines and a uranium reprocessing factory in the city of Aktau, Kazakhstan, may represent a risk of contaminating the surrounding areas by uranium and its daughter elements. One of the possible fingerprinting tools for studying the environmental contamination is using plant samples, collected in the surroundings of this city in 2007 and 2008. The distribution pattern of environmental pollution by uranium and thorium was evaluated by determining the thorium and uranium concentrations in plant samples ( Artemisia austriaca) from the city of Aktau and comparing these results with those obtained for the same species of plants from an unpolluted area (town of Kurchatov). The determination of the uranium and thorium concentrations in different parts of A. austriaca plants collected from the analyzed areas demonstrated that the main contamination of the flora in areas surrounding the city of Aktau was due to dust transported by the wind from the uranium mines. The results obtained demonstrate that all the areas surrounding Aktau have a higher pollution level due to thorium and uranium than the control area (Kurchatov). A few “hot points” with high concentrations of uranium and thorium were found near the uranium reprocessing factory and the uranium mines.

Geochemical evolution of uraniferous soda lakes in Eastern Mongolia

Extremely high concentrations of uranium (U) were discovered in shallow, groundwater-fed hyperalkaline soda lakes in Eastern Mongolia. A representative groundwater sample in this area is dilute and alkaline, pH = 7.9, with 10 mM TIC and 5 mM Cl−. In contrast, a representative lake water sample is pH ~ 10 with TIC and Cl− each more than 1,000 mM. Groundwater concentrations of U range from 0.03 to 0.43 μM L−1. Lake water U ranges from 0.24 to >62.5 μM, possibly the highest naturally occurring U concentrations ever reported in surface water. Strontium isotopes 87Sr/86Sr varied in groundwaters from 0.706192 to 0.709776 and in lakes 87Sr/86Sr varied from 0.708702 to 0.709432. High concentrations of U, Na, Cl−, and K correlate to radiogenic Sr in lake waters suggesting that U is sourced from local Cretaceous alkaline rhyolites. Uranium-rich groundwaters are concentrated by evaporation and U(VI) is chelated by CO 3 −2 to form the highly soluble UO2(CO3) 3 −4 . Modeled evaporation of lakes suggests that a U-mineral phase is likely to precipitate during evaporation.

Fuel of novel generation for PWR and as alternative to MOX fuel

To accomplish a further qualitative ramp in novel generation fuel development and to provide for the compatibility of electric power production we suggest to replace the container design fuel rod, the possibilities of which is practically exhausted, to dispersion type fuel elements (high uranium content fuel, U–Mo, U–Nb–Zr, U 3Si with Zr alloy matrix). The primary advantages of novel fuel are high uranium content (more than 15–50% in comparison with the standard UO 2 pelletized fuel rod), low temperature of fuel (<500 °C, cold fuel), the extension of burn-up (100 MW d/kgU) and serviceability under transient conditions. As a result – the increase of economic efficiency and lower cost of electrical power to be supplied to customer. The feasibility is demonstrated on the novel METMET fuel base to use combined U(Th)–PuO 2 fuel (an analog of MOX) fabricated by environmentally clean technology with improved fuel characteristics, which lead to nuclear fuel cycle closing. Novel approach to reprocessing of combined fuel is demonstrated, which allows to separate fissile material without chemical processes, with repeated use in CANDU or PWR reactors, which simplifies the closing of the fuel cycle.

Bioaccumulation of uranium 234U and 238U in marine birds

In the paper was presented results of our study about uranium 234U and 238U radioactivity in the marine birds samples, collected in the Polish area of the southern Baltic Sea. We chose 11 species of sea birds: three species permanently residing at southern Baltic, four species of wintering birds and three species of migrating birds. The obtained results indicated that uranium is very irregularly distributed in organs and tissues of marine birds. The highest uranium content is characterized in liver, rest of viscera and feathers, the smallest in skin and muscles. The uranium concentration was higher for carnivorous species (long-tailed duck (C. hyemalis), common eider (S. mollissima), lower for species eating fish (great cormorant (P. carbo), common guillemot (U. aalge), red-throated diver (G. stellata) and razorbill (A. tarda)), but the biggest amounts for herbivorous species [tufted duck (A. fuligula) and eurasian coot (F. atra)]. About 63–67% of uranium, which was located in feathers of two species of marine birds: razorbill (A. tarda) and long-tailed duck (C. hymealis), was apparently adsorbed, which suggests that uranium adsorption on the feathers may be an important transfer from air to water.