Areal distribution of 129I in west cumbrian solis

¹²⁹I has been released during operations at the BNFL nuclear fuel reprocessing plant at Sellafield in west Cumbria over the past thirty years with about 95% being discharged into the sea and 5% into the atmosphere. Soil samples have been taken within a 40 km radius of Sellafield to determine the extent to which the ¹²⁹I is deposited in the immediate vicinity of the plant. The ¹²⁹I content has been determined by a sensitive neutron activation technique and levels in soil were found to be elevated above global levels in all samples. The areal distribution of ¹²⁹I was consistent with direct deposition following release to the atmosphere from Sellafield and the relationship between ¹²⁹I activity and the distance from Sellafield was of a form predicted by atmospheric dispersion models. The absence of any observable return of ¹²⁹I from the sea has implications for assessments of dose.     

Spatial distribution of U isotopes in sea-water sediments, Red Sea, Egypt

Isotopes of uranium in the sea-water sediments collected from two different areas (El Hamraween harbour and Ras El Behar) on the Egyptian coast of the red sea have been studied using radiochemical separation procedures and alpha-particle spectrometry. Activity concentrations of ²³⁸U, ²³⁵U, ²³⁴U were calculated. The activities observed indicated enhanced radioactivity levels in sea-water sediments of El Hamraween harbour area due to the activities of phosphate shipment operation. Secular equilibrium between ²³⁴U and ²³⁸U was found in the analyzed samples. The average activity ratio of ²³⁵U/²³⁸U was close to the value 0.046 for uranium in nature.     

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.     

Use of HPGe gamma-ray spectrometry to assess the isotopic compositiion of uranium in soils

Gamma-ray spectrometry was used to determine uranium activity and investigate the presence of depleted uranium in soil samples collected from camping sites of the Greek expeditionary force in Kosovo. Assessment of 238U concentrations was based on measurements of the 63.3 keV and 92.38 keV emissions of its first daughter nuclide, 234Th. To determine the isotopic ratio of 238U/235U, secular equilibrium along the two radioactive series was first ensured and thereby the contribution of 235U under the 186 keV peak was deduced. The uranium activity in the samples varied from 48 to 112 Bq kg(-1), whereas the activity ratio of 238U/235U averaged 23.1+/-4.3.     

Determination of total content and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes by ICP-QMS

The aim of this work was to determine the concentrations and isotopic compositions of plutonium and uranium in environmental samples for safeguards purposes. An analytical method was developed with a plutonium and uranium separation procedure based on extraction chromatography (using 2 mL TEVA and UTEVA columns) and detection with a quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with a membrane desolvation system. Starting from blank swipes, the background equivalent concentration (BEC) was 8 fg for ²³⁹Pu and 1 ng ²³⁸U. The method was successfully applied to certified reference materials as well as to round robin samples obtained in the framework of the inter-laboratory exercise program, promoted by the Brazilian–Argentine Agency for Accounting and Control of Nuclear Materials (ABACC), together with the US Department of Energy (USDOE). After the introduction of an additional ion-exchange separation step, the methodology was applied to the IAEA-384 sediment reference sample with precise and accurate total plutonium and uranium, ²⁴⁰Pu/²³⁹Pu, ²⁴¹Pu/²³⁹Pu, ²³⁴U/²³⁸U and ²³⁵U/²³⁸U atomic ratio results.     

The marine impact of caesium-134 and -137 from the Chernobyl reactor accident

¹³⁴Cs and ¹³⁷Cs from the Chernobyl reactor accident were detected in UK shoreline seawater very quickly after activity from the accident reached this country. Concentrations were highest in areas adjacent to those where deposition over land was highest, but they declined quickly and did not reach radiologically significant levels in terms of public radiation exposure. Subsequently, the distribution in seawater was investigated further afield. Radiocaesium attributable to the Chernobyl accident was found to be widespread: it was readily distinguished from other sources by having a different ¹³⁷Cs:¹³⁴Cs ratio (about 2:1). Its presence was especially noticeable in northern UK waters rather than those to the south; much of the North Sea has been surveyed as well as the Norwegian Sea. Evidence of Chernobyl radiocaesium was found as far north as 70°N and in many of these areas, including the northern North Sea, it overshadowed the effect of BNFL (British Nuclear Fuels plc) Sellafield discharges, previously the main source of these radionuclides.     

High levels of natural radioactivity in biota from deep-sea hydrothermal vents: a preliminary communication

Hydrothermal deep-sea vent fauna is naturally exposed to a peculiar environment enriched in potentially toxic species such as sulphides, heavy metals and natural radionuclides. It is now well established that some of the organisms present in such an environment accumulate metals during their lifespan. Though only few radionuclide measurements are available, it seems likely that hydrothermal vent communities are exposed to high natural radiation doses. Various archived biological samples collected on the East Pacific Rise and the Mid-Atlantic Ridge in 1996, 2001 and 2002 were analysed by ICP-MS in order to determine their uranium contents (²³⁸U, ²³⁵U and ²³⁴U). In addition ²¹⁰Po–Pb were determined in 2 samples collected in 2002. Vent organisms are characterized by high U, and Po–Pb levels compared to what is generally encountered in organisms from outside hydrothermal vent ecosystems. Though the number of data is low, the results reveal various trends in relation to the site, the location within the mixing zone and/or the organisms' trophic regime.     

Suitable gamma energy for gamma-spectrometric determination of U in surface soil samples of a high rainfall area in India

The paper presents a systematic study on suitability of various gamma lines for monitoring of ²³⁸U activity in soil samples around a uranium mineralized zone of Kylleng Pyndengsohiong Mawthabah (Domiasiat), Meghalaya in India. The area lies in a plateau region which recieves the highest average annual rainfall (12,000 mm) in the world. The geochemical behaviour of the uranium and its daughter products at such wet climatic conditions imposes restrictions to assess ²³⁸U through gamma lines of radon decay products. Soil samples were collected from nine locations around the uranium mineralization zone for analysis. The ratio of the concentration of uranium obtained from gamma energies of radium daughter products to the 63.29 keV of ²³⁴Th was found to vary from 1.01 to 2.07, which indicates a pronounced disequilibrium between uranium and radium daughters. The results obtained from various gamma energies were validated from the data generated by Instrumental Neutron Activation Analysis (INAA) technique. The ²³⁸U activities from the two analytical methods show a well fitted regression line with correlation coefficient 0.99 which validates the reliability of 63.29 keV energy for estimation of uranium in such conditions.     

Concentration and characteristics of depleted uranium in biological and water samples collected in Bosnia and Herzegovina

During Balkan conflicts in 1994-1995, depleted uranium (DU) ordnance was employed and was left in the battlefield. Health concern is related to the risk arising from contamination of the environment with DU penetrators and dust. In order to evaluate the impact of DU on the environment and population in Bosnia and Herzegovina, radiological survey of DU in biological and water samples were carried out over the period 12-24 October 2002. The uranium isotopic concentrations in biological samples collected in Bosnia and Herzegovina, mainly lichens, mosses and barks, were found to be in the range of 0.27-35.7 Bq kg(-1) for (238)U, 0.24-16.8 Bq kg(-1) for (234)U, and 0.02-1.11 Bq kg(-1) for (235)U, showing uranium levels to be higher than in the samples collected at the control site. Moreover, the (236)U in some of the samples was detectable. The isotopic ratios of (234)U/(238)U showed DU to be detectable in many biological samples at most sites examined, but in very low levels. The presence of DU in the biological samples was as a result of DU contamination in air. The uranium concentrations in water samples collected in Bosnia and Herzegovina were found to be in the range of 0.27-16.2 m Bq l(-1) for (238)U, 0.41-15.6 m Bq l(-1) for (234)U and 0.012-0.695 m Bq l(-1) for (235)U, and two water samples were observed to be DU positive; these values are much lower than those in mineral water found in central Italy and below the WHO guideline for public drinking water. From radiotoxicological point of view, at this moment there is no significant radiological risk related to these investigated sites in terms of possible DU contamination of water and/or plants.     

A study of radionuclides, metals and stable lead isotope ratios in sediments and soils in the vicinity of natural U-mineralisation areas in the Northern Territory

Australian guidelines recommend that tailings materials from uranium (U) mining and milling be contained without any detrimental impact on the environment for at least 1000 years. Natural analogue sites are being investigated to determine if they can provide data on the rates of natural erosion processes which occur over these timescales, for input into predictive geomorphic computer models. This paper presents radionuclide, metal and stable lead (Pb) isotope data from sediment cores and surface soils in the vicinity of two mineralised areas in the Alligator Rivers Region.Surface scrapes from the natural Anomaly #2, south of the Ranger mineral lease, exhibit radiogenic ²⁰⁶Pb/²⁰⁷Pb and ²⁰⁸Pb/²⁰⁷Pb ratios, and elevated U and metal concentrations typical for a near surface U anomaly. In contrast, samples taken from the Koongarra mineral lease (KML) show radionuclide activity and metal concentrations similar to natural areas elsewhere in the Alligator Rivers Region and Pb isotope ratios are closer to present day average crustal ratios (PDAC), as the orebodies at KML are covered by surficial sand. A sediment core collected from Anbangbang Billabong, downstream of KML, exhibits small variations in Pb isotope ratios that indicate that approximately 1% of the upper sediments in the sediment core may be derived from material originating from the U anomaly at Koongarra.     

Americium,plutonium and uranium contamination and speciation in well waters,streams and atomic lakes in the Sarzhal region of the Semipalatinsk Nuclear Test Site,Kazakhstan

New data are reported on the concentrations, isotopic composition and speciation of americium, plutonium and uranium in surface and ground waters in the Sarzhal region of the Semipalatinsk Test Site, and an adjacent area including the settlement of Sarzhal. The data relate to filtered water and suspended particulate from (a) streams originating in the Degelen Mountains, (b) the Tel′kem 1 and Tel′kem 2 atomic craters, and (c) wells on farms located within the study area and at Sarzhal. The measurements show that ²⁴¹Am, ^239,240Pu and ²³⁸U concentrations in well waters within the study area are in the range 0.04–87 mBq dm⁻³, 0.7–99 mBq dm⁻³, and 74–213 mBq dm⁻³, respectively, and for ²⁴¹Am and ^239,240Pu are elevated above the levels expected solely on the basis of global fallout. Concentrations in streams sourced in the Degelen Mountains are similar, while concentrations in the two water-filled atomic craters are somewhat higher. Suspended particulate concentrations in well waters vary considerably, though median values are very low, at 0.01 mBq dm⁻³, 0.08 mBq dm⁻³ and 0.32 mBq dm⁻³ for ²⁴¹Am, ^239,240Pu and ²³⁸U, respectively. The ²³⁵U/²³⁸U isotopic ratio in almost all well and stream waters is slightly elevated above the ‘best estimate’ value for natural uranium worldwide, suggesting that some of the uranium in these waters is of test-site provenance. Redox analysis shows that on average most of the plutonium present in the microfiltered fraction of these waters is in a chemically reduced form (mean 69%; 95% confidence interval 53–85%). In the case of the atomic craters, the proportion is even higher. As expected, all of the americium present appears to be in a reduced form. Calculations suggest that annual committed effective doses to individual adults arising from the daily ingestion of these well waters are in the range 11–42 μSv (mean 21 μSv). Presently, the ground water feeding these wells would not appear to be contaminated with radioactivity from past underground testing in the Degelen Mountains or from the Tel′kem explosions.     

Carbon-14 discharges from the nuclear fuel cycle: 2. Local effects

Environemtnal ¹⁴C levels around various types of nuclear installations within the UK have been monitored during recent years. Enhanced ¹⁴C levels have been detected around both the nuclear fuel reprocessing plant as Sellafield and the thermal nuclear power station complex at Hunterston. From these measurements, the radiological impact of the ¹⁴C discharges on the local population is assessed. It is conservatively estimated that the ¹⁴CO₂ emissions from Sellafield between 1952 and 1985 could have delivered an 8·4 man Sv collective effective dose equivalent commitment to the population living within 40 km of the site. The maximum possible collective dose to the population within 15 km of Hunterston in 1984 was 15 × 10⁻³ man Sv. Conservative estimates of maximum annual effective dose equivalents to individuals around Sellafield and Hunterston are 0·2 mSv (in 1982) and 12 μSv (in 1984), respectively. These dose levels do not exceed the limits recommended by ICRP but the former value clearly indicates that, for the larger discharges at least, consideration and optimisation of ¹⁴C releases are fully justified. The same ¹⁴C measurements are also used to test the validity of two atmospheric dispersion models, the Gaussian plume and the so-called ‘hyperbolic’ models. The former is excellent in predicting downwind ¹⁴C levels around Hunterston but is unsatisfactory when applied to Sellafield, whereas the latter proves reliable at both sites. Further investigations suggest that the Gaussian plume model's poor performance at Sellafield can be explained by inaccurate input data.     

Reconstructing the history of 14C discharges from Sellafield: part 1--atmospheric discharges

14C specific activities, above ambient background levels, were determined in individual treerings (corresponding to the years 1950-1999) sectioned from an oak tree that was felled in autumn 1999, from a location 1.5 km east of the Sellafield nuclear fuel reprocessing plant in Cumbria. north-west England. The data were used to produce a new, improved, reconstruction of Sellafield's annual atmospheric 14C discharges between 1951 and 1999, using the most reliable discharge data set (1994-1999) as the primary basis for the determination of a new calibration factor that relates excess 14C activity in individual tree rings to the annual discharge during the corresponding year. The results indicate that the current British Nuclear Fuels plc (BNFL) estimate of total 14C discharges to the atmosphere prior to 1978 is significantly overestimated, while the current estimate of total 14C discharges after 1978 is very similar to that determined in this study. In this study, the total activity of 14C discharged to the atmosphere from Sellafield between 1951 and 1999 is estimated to be 259+/-63 TBq (at 2 std. dev.). The BNFL current estimate is 360TBq.     

MEAD (part II)-Predictions of radioactivity concentrations in the Irish Sea

The predictions from MEAD, a model that simulates the transport of radionuclides in the marine environment, are presented for the Irish Sea. MEAD predictions for (137)Cs and Pu(alpha) are presented following discharges from BNFL Sellafield and the predictions compared to measured data from near the discharge location and further a field in the Irish Sea. The model performs well in most circumstances given the uncertainties involved in both modelling and data collection although some inconsistencies in the predictions are found. MEAD is also compared to other models of radionuclide transport in the Irish Sea.     

Determination of depleted uranium in environmental samples by gamma-spectroscopic techniques

The military use of depleted uranium initiated the need for an efficient and reliable method to detect and quantify DU contamination in environmental samples. This paper presents such a method, based on the gamma spectroscopic determination of 238U and 235U. The main advantage of this method is that it allows for a direct determination of the U isotope ratio, while requiring little sample preparation and being significantly less labor intensive than methods requiring radiochemical treatment. Furthermore, the fact that the sample preparation is not destructive greatly simplifies control of the quality of measurements. Low energy photons are utilized, using Ge detectors efficient in the low energy region and applying appropriate corrections for self-absorption. Uranium-235 in particular is determined directly from its 185.72 keV photons, after analyzing the 235U-226Ra multiplet. The method presented is applied to soil samples originating from two different target sites, in Southern Yugoslavia and Montenegro. The analysis results are discussed in relation to the natural radioactivity content of the soil at the sampling sites. A mapping algorithm is applied to examine the spatial variability of the DU contamination.     

Uranium isotopes in groundwater from the continental intercalaire aquifer in Algerian Tunisian Sahara (Northern Africa)

The disequilibrium between ²³⁴U and ²³⁸U is commonly used as a tracer of groundwater flow. This paper aims to identify uranium contents and uranium isotopic disequilibria variation in groundwater sampled from deep Continental Intercalaire aquifer (southern Algeria and Tunisia). Large variations in both U contents (0.006–3.39 ppb) and ²³⁴U/²³⁸U activity ratios (0.4–15.38) are observed. We conduct a first assessment in order to verify whether the results of our investigation support and complete previous hydrogeological and isotopic studies. The dissolved U content and ²³⁴U/²³⁸U activity ratio data were plotted on a two-dimensional diagram that was successfully utilized on sharing the CI aquifer into different compartments submitted to different oxidising/reducing conditions and leads also to distinguished two preferential flow paths in the Nefzaoua/Chott Fejej discharge area. Uranium isotopes disequilibrium indicate that ranium chemistry is mainly controlled by water–rock interaction enhanced by long residence time recognised for this aquifer.     

Spatial distribution of uranium and thorium in the surface soil around proposed uranium mining site at Lambapur and its vertical profile in the Nagarjuna Sagar Dam

The understanding and evaluation of the possible interactions of various naturally occurring radionuclides in the world's third largest man-made dam, Nagarjuna Sagar located in Andhra Pradesh, India and built on river Krishna assumed significance with the finding of uranium deposits in locations near the dam. For the present work, surface soil samples from the mineralized area of Lambapur, Mallapuram, Peddagattu and sediment core samples from the Nagarjuna Sagar dam were analyzed for naturally occurring radionuclides namely uranium and thorium using gamma spectrometric technique. Also toxic elements lead and chromium were analysed by the Energy Dispersive X-ray Fluorescence Spectrometer (EDXRF) technique. Surface soil samples show a variation from 25 to 291 Bq/kg (2.02–23.5 mg/kg) for ²³⁸U and 32–311 Bq/kg (7.9–76.9 mg/kg) for ²³²Th. U/Th concentration ratio in surface soil samples ranged from 0.19 to 0.31 and was found comparable with the nation wise average of 0.26. The study of sediment core samples reflected higher U/Th concentration ratio of 0.30–0.33 in the bottom section of the core as compared to 0.22–0.25 in the upper section. The concentration ratio in the upper section of the core was similar to the ratio 0.23 found in the western Deccan Basalt region through which the river originates. A higher concentration of lead and chromium was observed in the upper section of the core compared to bottom section indicating the impact of river input on the geochemical character of dam sediment.     

Determination of U, Pu and Am isotopes in Irish Sea sediment by a combination of AMS and radiometric methods

Samples from a marine sediment core from the Irish Sea (54.416 N, 3.563 W) were analyzed for the isotopic composition of uranium, plutonium and americium by a combination of radiometric methods and AMS. The radiochemical procedure consisted of a Pu separation step by anion exchange, subsequent U separation by extraction chromatography using UTEVA^® and finally Am separation with TRU^® Resin.Additionally to radiometric determination of these isotopes by alpha spectrometry, the separated samples were also used for the determination of ²³⁶U/²³⁸U and plutonium isotope ratios by Accelerator Mass Spectrometry (AMS) at the VERA facility.     

Distribution and mobilization of U, Th and 226Ra in the plant-soil compartments of a mineralized uranium area in south-west Spain

The activity concentrations of natural uranium isotopes (238U and 234U), thorium isotopes (232Th, 230Th and 225Th) and 226Ra were studied in soil and vegetation samples from a disused uranium mine located in the Extremadura region in the south-west of Spain. The results allowed us to characterize radiologically the area close to the installation and one affected zone was clearly manifest as being dependent on the direction of the surface water flow from the mine. The activity concentration mean values (Bq/kg) in this zone were: 10,924, 10,900, 10,075 and 5,289 for 238U, 234U, 230Th and 226Ra, respectively, in soil samples and 1,050, 1,060, 768 and 1,141 for the same radionuclides in plant samples. In an unaffected zone, the activity concentration mean values (Bq/kg) were: 184, 190, 234 and 7251 for 235U, 234U, 230Th and 226Ra, respectively, in soil samples and 28. 29, 31 and 80 in plant samples. The activity concentrations obtained for 232Th and 228Th showed that the influence of the mine was only important for the uranium series radionuclides. The relative radionuclide mobilities were determined from the activity ratios. Correlations between radionuclide activity concentrations and stable element concentrations in the soil samples helped to understand the possible distribution paths for the natural radionuclides.     

Isotopic composition and origin of uranium and plutonium in selected soil samples collected in Kosovo

Soil samples collected from locations in Kosovo where depleted uranium (DU) ammunition was expended during the 1999 Balkan conflict were analysed for uranium and plutonium isotopes content (234U, 235U, 236U, 238U, 238Pu, (239 + 240)Pu). The analyses were conducted using gamma spectrometry (235U, 238U), alpha spectrometry (238Pu, (239 + 240)Pu), inductively coupled plasma-mass spectrometry (ICP-MS) (234U, 235U, 236U, 238U) and accelerator mass spectrometry (AMS) (236U)). The results indicated that whenever the U concentration exceeded the normal environmental values (approximately 2 to 3 mg/kg) the increase was due to DU contamination. 236U was also present in the released DU at a constant ratio of 236U (mg/kg)/238U (mg/kg) = 2.6 x 10(-5), indicating that the DU used in the ammunition was from a batch that had been irradiated and then reprocessed. The plutonium concentration in the soil (undisturbed) was about 1 Bq/kg and, on the basis of the measured 238Pu/(239 + 240)Pu, could be entirely attributed to the fallout of the nuclear weapon tests of the 1960s (no appreciable contribution from DU).