Conclusions on plutonium separation from atmospheric krypton-85 measured at various distances from the Karlsruhe reprocessing plant

For wide-area atmospheric monitoring, krypton-85 is the best indicator for clandestine plutonium separations. The detection and false alarm rates were determined from weekly samples at five different distances from the Karlsruhe reprocessing plant between 1985 and 1988. The detection rate for the separation of 4 kg of plutonium per week was found to be as high as 80-90% at a distance of less than 1 km, 70% at 5 km, 40% at 39 km, and 15% at 130 km. At distances up to 40 km, the false alarm rate is less than 3.5%. On average, the fuel released 28 TBq krypton-85 per kg plutonium. For weapons-grade plutonium, the krypton signal would be lower by a factor of 2. Hence, the given percentages correspond to the detection probabilities for the separation of a significant quantity (8 kg) of plutonium per weekly sample under the specific meteorological conditions of the WAK. The minimum separation rates that could have been detected are 2 gram of weapons-grade plutonium per week at a distance of less than 1 km, 40 g/week at 5 km, 200 g/week at 39 km, and 1000 g/week at 130 km.     

Simulating mesoscale transport and diffusion of radioactive noble gases using the Lagrangian particle dispersion model

In order to simulate the impact of mesoscale wind fields and to assess potential capability of atmospheric Lagrangian particle dispersion model (LPDM) as an emergency response model for the decision supports, two different simulations of LPDM with the mesoscale prognostic model MM5 (Mesoscale Model ver. 5) were driven. The first simulation of radioactive noble gas ((85)Kr exponent) emitted during JCO accident occurred from 30 September to 3 October 1999 at Tokai, Japan showed that the first arriving short pulse was found in Tsukuba located at 60km away from the accidental area. However, the released radioactive noble gas was transported back to the origin site about 2 days later due to the mesoscale meteorological wind circulation, enhancing the levels of (85)Kr with the secondary peak in Tsukuba. The second simulation of atmospheric dilution factors (the ratio of concentration to the emission rate, chi/Q), during the underground nuclear test (UNT) performed by North Korea showed that high chi/Q moved to the eastward and extended toward southward in accordance with the mesoscale atmospheric circulations generated by mesoscale prognostic model MM5. In comparison with the measurements, the simulated horizontal distribution patterns of (85)Kr during the JCO are well accord with that of observation in Tsukuba such as the existence of secondary peak which is associated with the mesoscale circulations. However, the simulated level of (85)Kr anomaly was found to be significantly lower than the observations, and some interpretations on these discrepancies were described. Applications of LPDM to two mesoscale emergency response dispersion cases suggest the potential capability of LPDM to be used as a decision support model provided accurate emission rate of accident in case of a large accident.     

An improved method for Kr analysis by liquid scintillation counting and its application to atmospheric Kr determination

Atmospheric ⁸⁵Kr concentration at Fukuoka, Japan was determined by an improved ⁸⁵Kr analytical method using liquid scintillation counting (LSC). An average value of 1.54 ± 0.05 Bq m⁻³ was observed in 2008, which is about two times that measured in 1981 at Fukuoka, indicating a 29 mBq y⁻¹ rate of increase as an average for these 27 years. The analytical method developed involves collecting Kr from air using activated charcoal at liquid N₂ temperature and purifying it using He at dry ice temperature, followed by Kr separation by gas chromatography. An overall Kr recovery of 76.4 ± 8.1% was achieved when Kr was analyzed in 500-1000 l of air. The Kr isolated by gas chromatography was collected on silica gel in a quartz glass vial cooled to liquid N₂ temperature and the activity of ⁸⁵Kr was measured with a low-background LS counter. The detection limit of ⁸⁵Kr activity by the present analytical method is 0.0015 Bq at a 95% confidence level, including all propagation errors, which is equivalent with ⁸⁵Kr in 1.3 l of the present air under the analytical conditions of 72.1% counting efficiency, 0.1597 cps background count rate, and 76.4% Kr recovery.     

Krypton-85 in the atmosphere 1950–1977: a data review

For over 20 years the radioactive noble gas ⁸⁵Kr, the product of nuclear industry, has been released to the environment mainly from nuclear fuel reprocessing plants. Owing to its relatively long half-life $\text{T(}\text{1}\text{2}\text{= 10.76}\text{y}\text{)}$ and the absence of other appreciable sinks, a cumulative buildup of ⁸⁵Kr in the atmosphere is observed. The mean ⁸⁵Kr surface air activity in the northern hemisphere has increased from about 20 dpm/mmol Kr in 1950 to about 750 dpm/mmol Kr in 1977. In recent years, a substantial slow-down of the ⁸⁵Kr emission rate to the atmosphere has been observed. The published data indicate rather good mixing of ⁸⁵Kr in the northern hemisphere, but a gradient is observed in the southern hemisphere due to the fact that all nuclear fuel reprocessing plants are situated in the northern hemisphere and due to poor mixing of the atmosphere in the meridional direction.This paper summarizes nearly all of the data on ⁸⁵Kr activity in the atmosphere published up to the middle of 1978. The spatio-temporal distribution of ⁸⁵Kr atmospheric activity is discussed. Some forecasts of future ⁸⁵Kr concentration in the atmosphere and its possible ecological consequences are also presented.     

Application of ICP-QMS for the determination of plutonium in environmental samples for safeguards purposes

Aiming to determine the plutonium amount as well as its isotopic composition, in particular, in swipe samples for safeguards purposes, an analytical method was developed with a plutonium separation step based on extraction chromatography using 2 cm TEVA columns and detection with quadrupole ICP-MS applying an ultra-sonic nebulizer coupled with membrane desolvation system. The method was successfully applied to New Brunswick plutonium certified reference materials as well as to Lawrence Livermore National Laboratory round robin samples, based on the round robin samples provided by the Institute for Reference Materials and Measurements (Belgium), as part of the Regular European Interlaboratory Measurement Evaluation Programme (REIMEP), campaign 16 (isotopic abundances of plutonium in plutonium nitrate samples), with a total plutonium amount between 1 and 0.25 ng per sample. After the introduction of an additional separation step, it was also possible to carry out precise and accurate total plutonium, (240)Pu/(239)Pu, (241)Pu/(239)Pu and (242)Pu/(239)Pu atom ratios determination in sediment sample showing its applicability to environmental samples in general, reaching a detection limit equivalent to 5 mBq(239)Pu kg(-1).     

85Kr atmospheric concentration in Bratislava from 1980 to 1983

A cryogenic-chromatographic method for determination of ⁸⁵Kr in the atmosphere is presented. Sampling of the air on the activated-charcoal, chromatographic separation of Krypton from the other air components and radioactivity measurement are described in details. The activity of ⁸⁵Kr is measured by small proportional counters with sensitive volumes of 5 and 10 cm³. Results of the measurements of ⁸⁵Kr air concentration in Bratislava from 1980 to 1983 are presented and compared with other ⁸⁵Kr data measured in Europe.     

Apparent 85Kr ages of groundwater within the Royal watershed, Maine, USA

Specific 85Kr activity is mapped from 264 domestic and municipal wells sampled during 2002-2004 in the Royal watershed (361 km2), Maine. Gas samples are collected at 20 m, 40 m, and > 50 m interval depths within the unconfined aquifers. Gas extraction for 85Kr from wells is obtained directly via a wellhead methodology avoiding conventional collection of large sample volumes. Atmospheric 85Kr input to the recharge environment is estimated at 1.27 Bq m(-3) by time-series analyses of weighted monthly precipitation (2001-2004). Numerical simulation of Kr gas transport through the variable unsaturated zones to the water table suggests up to 12-year time lags locally, thus biasing the 85Kr groundwater ages. Apparent 85Kr ages suggest that approximately 70% of groundwater near 20 m depth was recharged less than 30 years BP (2004). Mass-age transport modeling suggests that post mid-1950s recharge penetrates to part of the basin's floor and that older groundwater seeps from the underlying fractured bedrock may occur.     

A new compilation of the atmospheric 85krypton inventories from 1945 to 2000 and its evaluation in a global transport model

This paper gives the yearly (85)Kr emissions of all known reprocessing facilities, which are the main sources of (85)Kr in the atmosphere since 1945, for the years 1945 until 2000. According to this inventory 10,600 PBq (Peta=10(15)) of (85)Kr have been globally emitted from the year 1945 until the end of 2000. The global atmospheric inventory at the end of the year 2000 amounts to 4800 PBq. These emissions have been incorporated into the ECHAM4 atmospheric general circulation model as point sources. Monthly mean model results are compared with measurements made at different locations and times. The influence of each source on the measured concentrations at various locations is studied. The calculated concentrations are found to give reasonably good agreement with the observations, indicating that the emission inventory is realistic. Although, at all northern hemispheric observation sites the model tends to slightly overestimate the concentrations. A possible reason for this overestimation can be found in model features (coarse resolution in time and space). The most prominent discrepancy that is consistently repeated at all northern hemispheric stations occurs in the early 1990s. This could most likely be related to an overestimate of sources. Possibly, the Russian emissions declined earlier than assumed in the current database. Another discrepancy between observations and simulations indicating an incompleteness of the release data is found at some southern hemispheric sites. The variability of their observations could only be explained by regional sources. However, several spikes occur after 1992 when no reprocessing facility is known to be in operation in the southern hemisphere. Production of isotopes for radiopharmaceuticals like technetium-99m from highly enriched uranium is the most likely explanation.     

Radioisotope contaminations from releases of the Tomsk-Seversk nuclear facility (Siberia, Russia)

Soils have been sampled in the vicinity of the Tomsk-Seversk facility (Siberia, Russia) that allows us to measure radioactive contaminations due to atmospheric and aquatic releases. Indeed soils exhibit large inventories of man-made fission products including 137Cs (ranging from 33,000 to 68,500 Bq m(-2)) and actinides such as plutonium (i.e. 239+240Pu from 420 to 5900 Bq m(-2)) or 241Am (160-1220 Bq m(-2)). Among all sampling sites, the bank of the Romashka channel exhibits the highest radioisotope concentrations. At this site, some short half-life gamma emitters were detected as well indicating recent aquatic discharge in the channel. In comparison, soils that underwent atmospheric depositions like peat and forest soils exhibit lower activities of actinides and 137Cs. Soil activities are too high to be related solely to global fallout and thus the source of plutonium must be discharges from the Siberian Chemical Combine (SCC) plant. This is confirmed by plutonium isotopic ratios measured by ICP-MS; the low 241Pu/239Pu and 240Pu/239Pu atomic ratios with respect to global fallout ratio or civil nuclear fuel are consistent with weapons grade signatures. Up to now, the influence of Tomsk-Seversk plutonium discharges was speculated in the Ob River and its estuary. Isotopic data from the present study show that plutonium measured in SCC probably constitutes a significant source of plutonium in the aquatic environment, together with plutonium from global fallout and other contaminated sites including Tomsk, Mayak (Russia) and Semipalatinsk (Republic of Kazakhstan). It is estimated that the proportion of plutonium from SCC source can reach 45% for 239Pu and 60% for 241Pu in the sediments.     

Removal of radionuclides at a waterworks

A waterworks with an average production rate of 1.3 m3 s(-1), providing several large cities in the province of Scania with drinking water has been studied regarding its capacity to remove several natural and anthropogenic radionuclides. The raw water is surface water from lake Bolmen which is transported through an 80 km long tunnel in the bedrock before it enters the waterworks. The method used for purification is a combination of coagulation-flocculation and filtration in sand filters. Two different purification lines are currently in use, one using Al2(SO4)3 as a coagulant and one using FeCl3. After coagulation and flocculation the precipitate is removed and the water is passed through two different sand filters (rapid filtration and slow filtration). Water samples were collected at the lake, the inlet to the waterworks, after each of the flocculation basins (Al2(SO4)3 and FeCl3), after rapid filtration and from the municipal distribution network. The samples were analysed with respect to their content of uranium, thorium, polonium, radium, plutonium and caesium. The results show a high removal capacity for uranium (about 85%), thorium (>90%), plutonium (>95%) and polonium (>90% in the coagulation-flocculation process) while caesium, strontium and radium pass through the purification process with almost unchanged activity concentrations. During transportation of the water in the tunnel it was also observed that infiltration of groundwater leads to a change in isotopic ratios and/or activity concentrations for the naturally occurring radionuclides and plutonium.     

Plutonium bioaccumulation in seabirds

The aim of the paper was plutonium (²³⁸Pu and ^239+240Pu) determination in seabirds, permanently or temporarily living in northern Poland at the Baltic Sea coast. Together 11 marine birds species were examined: 3 species permanently residing in the southern Baltic, 4 species of wintering birds and 3 species of migrating birds. The obtained results indicated plutonium is non-uniformly distributed in organs and tissues of analyzed seabirds. The highest plutonium content was found in the digestion organs and feathers, the smallest in skin and muscles. The plutonium concentration was lower in analyzed species which feed on fish and much higher in herbivorous species. The main source of plutonium in analyzed marine birds was global atmospheric fallout.     

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.     

In situ metrology of 85Kr plumes released by the COGEMA La Hague nuclear reprocessing plant

The IRSN (Institut de Radioprotection et de S?reté Nucléaire, France) has started an in situ study of the behaviour of atmospheric releases close-by the COGEMA La Hague nuclear reprocessing plant. The study is designed to improve information on the dispersion of radioactive pollutants very close to the emission point--a 100 m height chimney. In this situation, close to the emission and height of the emission, Gaussian models generally used to predict the behaviour of atmospheric releases are not well adapted. The study is based on the characterisation of the 85Kr emitted during normal operations of the reprocessing process. Temporal and spatial variations of the plume shape were investigated with intensive in situ measurements. Live in situ techniques to measure the electrons and the photons emitted by the 85Kr have been implemented and will be described. Preliminary results showing the interest of the techniques were presented. Variations of the dose rates created by the photon flux of a plume were directly measured and correlated to other quantities.     

Plutonium in sheep faeces as an indicator of deposition on vegetation

In order to study the deposition on vegetation of plutonium arising from the testing of nuclear weapons and discharges from nuclear facilities, sheep faeces were collected from the South-west and North of England. The plutonium content of faeces has been shown to be a reproducible and sensitive indicator of deposition on herbage and, with this technique, plutonium discharged from the Sellafield Works of British Nuclear Fuels LImited can be detected 60 km from the site. On moorland pastures the concentration of ^239+240Pu in faeces, expressed as activity per gram of ash, is roughly equal numerically to the deposit of plutonium on 1 m² of vegetation.Some of the plutonium ingested by a grazing sheep is absorbed and the highest concentrations are found in liver. The liver of a sheep grazing on pasture where the ^239+240Pu concentration in faeces was about 2 pCi (74 mBq) g⁻¹ of ash, was found to contain <1% of the Generalised Derived Limit for mutton and offal, and the meat <0·001%.     

Ecophysiology of Steppe Mouse Subspecies <Emphasis Type="Italic">Mus spicilegius spicilegus</Emphasis>, Peteni, 1883 (Rodentia,Mammalia) at the South Boundary of its Distribution

Diet, food preferences and main ecophysiological characteristics such like energy requirements and thermoregulation characteristics of Mus spicilegus spicilegus (Petenyi, 1882) were studied. The most preferred foods for the mice were seeds of weed species that composed more than 85% of their diet. The results of food selection experiments shows that the total daily consumption by mice is 2.77 ± 0.76 g/animal/day or 5.5 kJ/g/day or 84.9 kJ/animal/day. From the total daily energy consumption 16.4% go back to nature in the form of feces and urine and the rest 83.6% animals utilized for assimilation. The results of the temperature preferences for Mus s. spicilegus shows preferred temperature zone from around 26 to 36°C where mice spent about 72% of the experimental time. The lowest value of oxygen consumption for resting metabolism rate (RMR) was registered at 30°C–3.20 ± 0.71 cm³ O₂/g/h. It is possible to consider that the thermoneutral zone is around these temperature values. The obtained results give reason to conclude that from an ecophysiologycal point of view the climate in the south boundary of distribution provides optimal conditions for species development. The main cause for population decreasing probably is the loss of open habitats including natural steppe grasslands.     

4-Nonylphenol and bisphenol A in Swedish food and exposure in Swedish nursing women

4-Nonylphenol (NP) and bisphenol A (BPA) are phenolic substances used in high volumes by the industry. Studies on cells and in experimental animals have shown that both these compounds can be classified as estrogenic hormone disrupters. Information about the exposure of humans to NP and BPA is still scarce, especially regarding levels in human blood. The first aim of this study was to investigate possible sources of NP and BPA exposure from food, by analyzing the levels of NP and BPA from a Swedish food market basket, based on the Swedish per capita food consumption. A second aim was to investigate blood serum levels of NP and BPA, as well as NP-ethoxylates, among young women in Sweden (n = 100). Moreover, associations between food consumption and blood NP and BPA levels were studied. In food, NP was to some extent found at levels above limit of quantification (LOQ 20 ng/g fresh weight) in fruits, cereal products, vegetables, and potatoes. BPA levels above LOQ (2 ng/g fresh weight) were found in fish, meats, potatoes, and dairy products. The estimated mean intakes per capita were (medium bound) 27 μg NP/day and 3.9 μg BPA/day, showing that food is a source of BPA and NP in the general Swedish population. In blood serum, free NP above limit of detection (LOD 0.5 ng/g) was detected in 46% of the study participants while detectable levels of total NP (LOD 0.8 ng/g) were observed in 43%. The corresponding percentages for BPA were 25% and 22%, respectively. The results indicate that there is a continuous source of exposure to NP and BPA that is high enough for free NP and BPA to be detected in some consumers. Among the participants with quantifiable levels of free and total NP (n = 38), 85% (median, range: 38–112%) of the NP was present as free NP. For BPA 76% (49–109%) was detected as free BPA (n = 15). All women had levels of ethoxylates of NP below LOD (0.1–0.7 ng/g). A significantly higher total consumption of fruits and vegetables was reported in questionnaires by participants with NP levels at or above LOD than among women with levels below LOD. This result is supporting the market basket results of relatively high NP levels in these types of food.     

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.     

Estimating the date corresponding to the horizon of the first detection of 137Cs and 239+240Pu in sediment cores

The anthropogenic bomb fallout nuclides 137Cs and plutonium isotopes (240Pu, 239Pu) are important chronometers for the determination of recent sediment accumulation rates using sediment cores collected from various water bodies. One of the crucial time horizons used to date sediment core profiles corresponds to the date of first detection of these nuclides. Although atmospheric nuclear testing began during the mid-1940s, the year corresponding to a nuclide's first detection when measured in 2006 depends on a number of factors including fallout history, radioactive half-life, gamma/alpha detection limits, geographic latitude and the accumulated thickness of the sediment section. This paper reports estimations of the year of first detection in sediment profiles of fallout 137Cs and Pu measured by gamma and alpha spectrometry, respectively. We find that for the latitude 30-40 degrees south of the equator the year of first detection for 137Cs is 1955. The date is earlier in the northern hemisphere due to higher fallout rates. Due to better measurement sensitivity first detection of Pu is generally earlier than 137Cs by 1-2 years.     

Retention and translocation of foliar applied 239,240Pu and 241Am, as compared to 137Cs and 85Sr, into bean plants (Phaseolus vulgaris)

Foliar transfer of 241Am, 239,240Pu, 137Cs and 85Sr was evaluated after contamination of bean plants (Phaseolus vulgaris) at the flowering development stage, by soaking their first two trifoliate leaves into contaminated solutions. Initial retentions of 241Am (27%) and 239,240Pu (37%) were higher than those of 137Cs and 85Sr (10-15%). Mean fraction of retained activity redistributed among bean organs was higher for 137Cs (20.3%) than for 239,240Pu (2.2%), 241Am (1%) or 85Sr (0.1%). Mean leaf-to-pod translocation factors (Bq kg(-1) dry weight pod/Bq kg(-1) dry weight contaminated leaves) were 5.0 x 10(-4) for 241Am, 2.7 x 10(-6) for 239,240Pu, 5.4 x 10(-2) for 137Cs and 3.6 x 10(-4) for 85Sr. Caesium was mainly recovered in pods (12.8%). Americium and strontium were uniformly redistributed among leaves, stems and pods. Plutonium showed preferential redistribution in oldest bean organs, leaves and stems, and very little redistribution in forming pods. Results for americium and plutonium were compared to those of strontium and caesium to evaluate the consistency of the attribution of behaviour of strontium to transuranium elements towards foliar transfer, based on translocation factors, as stated in two radioecological models, ECOSYS-87 and ASTRAL.     

Estimates of (239+240)Pu inventories in Gdańsk Bay and Gdańsk basin

This paper presents and discusses the results of (239+240)Pu determinations in different components of Gdańsk bay and Gdańsk basin ecosystem, as well as estimated sources and inventories of plutonium in these basins. The total plutonium (239+240)Pu activities deposited in Gdańsk bay and Gdańsk basin sediments are 1.18 TBq and 3.77 TBq, respectively. Two rivers, the Vistula and Neman rivers, and atmospheric fallout were distinguished as the main sources of plutonium in these basins. In seawater (with suspended matter included) there is about 2.33 GBq (239+240)Pu (0.2% of total activity) in Gdańsk bay and 9.92 GBq (239+240)Pu (0.3% of total activity) in Gdańsk basin. In both cases, 56% of (239+240)Pu is associated with suspended matter. Organisms contain 3.81 MBq in Gdańsk bay and 7.45 MBq (239+240)Pu in Gdańsk basin. From this value in Gdańsk bay 82.1% of plutonium is associated with zoobenthos, 13.6% with phytobenthos, 1.6% with phytoplankton, 1.5% with zooplankton and 1.2% with fish. In Gdańsk basin, 83.2% is associated with zoobenthos, 7.5% with phytobenthos, 3.6% with phytoplankton, 3.2% with zooplankton and 2.5% with fish.