Challenges associated with the behaviour of radioactive particles in the environment

Transfer of radionuclides through ecological systems: Lessons learned from 10 years of research within CERAD CoE

Norway's Centre of Excellence for Environmental Radioactivity (CERAD) research programme included studies on transfer of radionuclides in various ecosystems within the context of environmental risk assessment. This article provides highlights from 10 years of research within this topic and summarises lessons learnt from the process. The scope has been extensive, involving laboratory-based experiments, field studies and the implementation of transfer models quantifying radionuclide uptake directly from the surrounding environment and via food chains. Field studies have had a global span and have, inter alia, covered sites contaminated with radionuclides associated with particles, ranging from nanoparticles to fragments, due to nuclear accidents (e.g., Chornobyl and Fukushima accidents) along with sites having enhanced levels of naturally occurring radioactive materials (e.g., Fen Complex in Norway and Taboshar in Tajikistan). Focus has been put on speciation and kinetics in determining radionuclide behavior and fate as well as on the influence of environmental factors that are potentially critical for the transfer of radionuclides. In particular, seasonal factors have been shown to greatly affect the dynamics of 137Cs and 90Sr bioaccumulation and loss in freshwater fish. The work has led to the collation of organism-specific (i) parameters important for kinetic models, i.e., uptake and depuration rates, and (ii) steady-state concentration ratios, CRs, where the use of stable analogue CRs as proxies for radionuclides has been brought into question. Dynamic models have been developed and applied for radiocaesium transfer to reindeer, radionuclide transfer in Arctic marine systems, transfer to fish via water and feed and commonly used agricultural food-chain transfer models applied in the context of nuclear emergency preparedness. The CERAD programme should contribute substantially to the scientific community's understanding of radionuclide transfer in environmental systems.

Investigation of the distribution of transuranic radionuclides in marine sediment at the Montebello Islands, Western Australia

Three nuclear weapons tests were conducted in the 1950s at the Montebello Islands, Western Australia. The detonations were of different yields and configurations (two tower tests, one ship test), and led to substantial radionuclide contamination within the surrounding terrestrial and marine ecosystems. The region possesses great ecological and recreational significance, particularly within the marine environment. However, studies conducted so far have largely neglected the marine ecosystem which makes up the majority of the Montebello Island Marine Park and in which most test fallout would have deposited. Here we investigated the distribution of the transuranic radionuclides 238Pu, 239,240Pu and 241Am in marine sediment from the Montebello Islands. Marine sediment samples near Operation Mosaic G2 and Operation Hurricane were collected and analysed by gamma and alpha spectrometry. Activity concentrations of 239,240Pu across both series ranged from 45 to 2900 Bq kg-1, while 241Am levels ranged from 2.8 to 70 Bq kg-1. Higher activity concentrations were observed in sediment near the land-based, higher yield Mosaic G2 test, compared with the ship-based, lower yield Hurricane test. Sediment samples located closer to the detonation site were also observed to have higher activity concentrations. Radioactive particles of 0.94 mm and 1.5 mm in diameter were identified by analysis of size-fractioned sediment via investigation of 152Eu levels, photostimulated autoradiography and point gamma spectroscopy. Particles were confirmed to have transuranic radionuclide interiors, with surface coatings which were dominated by vitrified CaCO3. Their long-term resistance to weathering and subsequent persistence in the marine environment can therefore be attributed to their coated structural form. Our study confirms the persistence of transuranic radionuclides in Montebello Island marine sediment and highlights the need for additional studies to improve our understanding of the nuclear legacy in this region.

Comprehensive framework for overcoming scientific challenges related to assessing radioactive ultra-fine (nano/micro) particles transfer at the atmosphere-leaf interface

Food products are prone into contamination after a nuclear emission of radionuclides. While the mechanisms of emission and deposition of ultrafine radioactive particles are well documented, the transfer of these species from the atmosphere into plants is poorly assessed. This is evident in the lack of quantification of particles distributed within plants, especially regarding particles physical-chemical criteria to plant of different properties. Such knowledge gaps raise the concern about the representativeness of risk assessment tools designed for the transfer evaluation of ionic/soluble species to be qualified for simulating insoluble species exposure and proposes a possible underestimation. This highlights the possible need for special particle codes development to be implemented in models for future emissions. In addition, the later tools utilize transfer factors aggregating relevant sub-processes, suggesting another weak point in their overall reliability. As researchers specialized in the nuclear safety and protection, we intend in this perspective, to develop a compressive analysis of the interaction of ultrafine particles with plants of different specificities at different level processes starting from particles retention and gradual translocation to sink organs. This analysis is leveraged in providing insights for possible improvements in the current modeling tools for better real-life scenarios representation.

Assessment of exposures to firefighters from wildfires in heavily contaminated areas of the Chornobyl Exclusion Zone

The aim of this study was to assess the exposures received by firefighters engaged in extinguishing the large-scale wildfires in the most contaminated areas of the Ukrainian part of the Chornobyl Exclusion Zone in 2016 and 2020. The assessments are based on measurements of radionuclide airborne concentrations in the breathing zones of workers and at the aerosol sampling stations of the automated radiation monitoring system operated by SSE Ecocenter. During the wildfires, the radionuclide airborne concentrations increased by orders of magnitude compared to the background levels, reaching maximum values in the firefighting area of 1.20 ± 0.01 Bq m-3 for 90Sr, 0.18 ± 0.01 Bq m-3 for 137Cs, (1.8 ± 0.3) ∙10-4 Bq m-3 for 238Pu, (4.5 ± 0.7) ∙10-4 Bq m-3 for 239-240Pu, and (8.0 ± 1.3) ∙10-3 Bq m-3 for 241Pu. The internal effective doses to firefighters due to inhaled radionuclides did not exceed 2 μSv h-1 and were 3-5 times lower compared to the external dose of gamma radiation. Thus, the time of firefighting in the ChEZ will be limited by the external dose.

Environmental stability of a uranium-plutonium-carbide phase

A plutonium-rich carbide, (U,Pu)(Al,Fe)3C3, was discovered in a hot particle from the Maralinga nuclear testing site in South Australia. The particle was produced between 1960 and 1963 and has been exposed to ambient conditions since then. The new phase belongs to a group of ternary carbides known as 'derivative-MAX phases'. It formed at high temperature within an explosion cloud via rapid eutectic crystallisation from a complex Al-Fe-U-Pu-C-O melt, and is the major Pu host in this particle. Despite signs of volume expansion due to radiation damage, (U,Pu)(Al,Fe)3C3 remains highly X-ray crystalline 60 years after its formation, with no evidence of Pu leaching from the crystals. Our results highlight that the high-energy conditions of (sub-)critical explosions can create unexpected species. Even micro-particles of a derivative-MAX phase can effectively retain low-valence (metallic-like character) Pu under environmental conditions; the slow physical and chemical weathering of these particles may contribute to the slow release of radionuclides over decades, explaining constant low-levels of radionuclides observed in fauna. This study further suggests that rapidly quenched eutectic melts may be engineered to stabilise actinides in nuclear waste products, removing the need for hydrometallurgical processing.

Research progress on the analysis and application of radioactive hot particle

Radioactive hot particle is the particulate form of nuclear material that exists in the environment. The U, Pu, Am, Cs, and other radionuclides isotope in the hot particle contain abundant and accurate fingerprint information, such as the origin and age of the nuclear material. The acquisition and analysis of the key information in the hot particle can be equivalent to the analysis of bulk nuclear material, which could directly reflect the real situation of nuclear activities. Therefore, the single particle analysis of hot particles has become an irreplaceable key technology in nuclear safeguards inspection. The rapid identification, screening, locating, and accurate isotope analysis of hot particles from a large number of particles dispersed in environmental media or on the surface of other materials are one of the most important research field in nuclear emergency. In this review, the research process of the analytical methods for hot particles in the last decade was summarized, including the physical character of hot particles, and the techniques of localization, screening, and extraction of hot particles. Furthermore, we also focused on the mass spectrometry technology for the analysis of hot particle. The advantages and disadvantages of the most used mass spectrometry were summarized. Finally, the research trend for hot particle analysis methods was proposed.

Synchrotron-Based X-ray Fluorescence Imaging Elucidates Uranium Toxicokinetics in Daphnia magna

A combination of synchrotron-based elemental analysis and acute toxicity tests was used to investigate the biodistribution and adverse effects in Daphnia magna exposed to uranium nanoparticle (UNP, 3-5 nm) suspensions or to uranium reference (U_ref) solutions. Speciation analysis revealed similar size distributions between exposures, and toxicity tests showed comparable acute effects (UNP LC₅₀: 402 μg L^-1 [336-484], U_ref LC₅₀: 268 μg L^-1 [229-315]). However, the uranium body burden was 3- to 5-fold greater in UNP-exposed daphnids, and analysis of survival as a function of body burden revealed a ∼5-fold higher specific toxicity from the U_ref exposure. High-resolution X-ray fluorescence elemental maps of intact, whole daphnids from sublethal, acute exposures of both treatments revealed high uranium accumulation onto the gills (epipodites) as well as within the hepatic ceca and the intestinal lumen. Uranium uptake into the hemolymph circulatory system was inferred from signals observed in organs such as the heart and the maxillary gland. The substantial uptake in the maxillary gland and the associated nephridium suggests that these organs play a role in uranium removal from the hemolymph and subsequent excretion. Uranium was also observed associated with the embryos and the remnants of the chorion, suggesting uptake in the offspring. The identification of target organs and tissues is of major importance to the understanding of uranium and UNP toxicity and exposure characterization that should ultimately contribute to reducing uncertainties in related environmental impact and risk assessments.

Identification, isolation, and characterization of a novel type of Fukushima-derived microparticle

In the course of the Fukushima nuclear accident, radionuclides were released in various forms, including so-called radiocesium-bearing microparticles (CsMP). So far, four types of CsMP were described: Type A is smaller in size (< 10 μm), Types B, C, and D are larger (> 100 μm). In this work, we present a novel type of CsMP (proclaimed Type E). Three particles of Type E were extracted from a contaminated blade of grass that was sampled 1.5 km from the Fukushima Daiichi nuclear power plant in late 2011. They were located using autoradiography, isolated using an optical microscope and micromanipulator, and characterized using scanning electron microscopy, energy dispersive x-ray spectroscopy, and low-level gamma-ray spectrometry. Type E CsMPs are 10–20 μm in size and exhibit an unusually low and barely detectable 137Cs activity of only ≤ 10 mBq per particle. Their brittle and fragile character may indicate a high surface tension.

Fukushima and Chernobyl: Similarities and Differences of Radiocesium Behavior in the Soil-Water Environment

In the wake of Chernobyl and Fukushima accidents, radiocesium has become a radionuclide of most environmental concern. The ease with which this radionuclide moves through the environment and is taken up by plants and animals is governed by its chemical forms and site-specific environmental characteristics. Distinctions in climate and geomorphology, as well as ¹³⁷Cs speciation in the fallout, result in differences in the migration rates of ¹³⁷Cs in the environment and rates of its natural attenuation. In Fukushima areas, ¹³⁷Cs was strongly bound to soil and sediment particles, with its bioavailability being reduced as a result. Up to 80% of the deposited ¹³⁷Cs on the soil was reported to be incorporated in hot glassy particles (CsMPs) insoluble in water. Disintegration of these particles in the environment is much slower than that of Chernobyl-derived fuel particles. The higher annual precipitation and steep slopes in Fukushima-contaminated areas are conducive to higher erosion and higher total radiocesium wash-off. Among the common features in the ¹³⁷Cs behavior in Chernobyl and Fukushima are a slow decrease in the ¹³⁷Cs activity concentration in small, closed, and semi-closed lakes and its particular seasonal variations: increase in the summer and decrease in the winter.

Natural occurring radioactive materials (NORMs) from mining sites in Nigeria: A systematic review of geographical distribution and public health concern

Solid mineral mining activities have contributed to the distribution and uptake of radionuclides. This has increased the active concentration of naturally occurring radioactive materials NORMs in different environmental media with increased human health risks. This systematic review was aimed at assessing data on active concentration of naturally occurring radioactive materials in mining sites in Nigeria. Articles available on recognized data bases such as Google scholar, PubMed, Cochrane Library and Science Direct were used. Thirty-two studies were used for this systematic review after meeting the inclusion criteria. Reports of studies according to Geopolitical zones revealed 0% North-east, 4% for Southeast, 8% for South-South, 16% in North-West, 20% in South-West, and 52% from North-Central Nigeria. 50%, 45.2%, 50%, and 38.5% of included studies reported elevated active concentration of 232Th, 40K, 238U and 226Ra in soil above world regulatory standards of the ICRP, UNSCEAR and IAEA. Gross-alpha and gross-beta activity concentrations reference dose level (RDL) were exceeded in 83.3% and 80% of studies respectively with the highest values recorded in water 10.12Bq/l, and 14.63Bq/l from an artisanal gold mine in North-West Nigeria. These data agree with reports from other African countries, but lower than reports from China and India. NORMs may be of public health concerns notwithstanding the lean data from clinical and epidemiological studies in Nigeria. This study recommends a One Health approach on the radiological implications of mining sites in Nigeria.

Calibration and Validation of Calcium Carbonate Precipitation Potential (CCPP) Model for Strontium Quantification in Cold Climate Aquatic Environments

The ability to robustly quantify the potential for strontium precipitation and scaling in both natural surface waters and water infrastructure systems is limited. In some regions, both surface and ground water supplies contain significant concentrations of naturally occurring radionuclides, such as strontium, that can accumulate in water, soils and sediments, media, and living tissues. Methods for quantifying and predicting the potential for these occurrences are not readily available nor have they been tested and calibrated to cold region aquatic environments. Through extensive literature review, it was determined that a modified calcium carbonate precipitation potential (CCPP) model offered a scientifically credible approach to filling that knowledge gap in both the science and engineering of strontium fate and transport in water. The results from previous field and laboratory experiments were compiled to not only elucidate the fate and transport of strontium in water systems, but also to calculate the logarithmic distribution coefficient, λ, for strontium under co-precipitation conditions. Lambda (λ) is both time- and water-quality sensitive and must be measured as water mixes from source to receiving environment to determine continuous loss of Sr from the water phase. The data were collected to develop the strontium precipitation potential model that can be used in surface water quality assessment. The tool was then applied to pre-existing, publicly available, and extensive datasets for several rivers in Saskatchewan, Canada, to validate the model and produce estimates for strontium precipitation potential in those rivers.

Analogue Application of Behaviour and Transport of Naturally Occurring Strontium in Cold-Region Aquatic Environments to 90Sr

Quantification and scientific observations of the fate and transport of dissolved strontium in water systems, particularly cold climate water systems, are severely lacking. In this work, in an experiment conducted at a temperature of 6 °C, the observation of strontium precipitation along with calcium carbonate minerals from cold wastewater is investigated. ICP-MS is used for metal analyses where the distribution of the species and saturation state of minerals along with a surface complexation model was performed using the public-use USGS geochemical modeling software, PHREEQC (PH Redox Equilibrium (in C language)). Sample media were analyzed using XPS and Raman spectroscopy. The results suggest that the loss of strontium from natural waters is via the process of co-precipitation with calcite, a calcium carbonate polymorph. The observations and findings are intended to be useful to quantify the loss of 90Sr from the water, in the case of an unplanned release from a nuclear reactor-operated facility. The results indicate that the precipitation model is a robust and reliable approach to predicting and monitoring the behaviour and transport of strontium that may occur in natural environments as a result of an accidental nuclear release.

70-Year Anthropogenic Uranium Imprints of Nuclear Activities in Baltic Sea Sediments

A strongly stratified water structure and a densely populated catchment make the Baltic Sea one of the most polluted seas. Understanding its circulation pattern and time scale is essential to predict the dynamics of hypoxia, eutrophication, and pollutants. Anthropogenic ²³⁶U and ²³³U have been demonstrated as excellent transient tracers in oceanic studies, but unclear input history and inadequate long-term monitoring records limit their application in the Baltic Sea. From two dated Baltic sediment cores, we obtained high-resolution records of anthropogenic uranium imprints originating from three major human nuclear activities throughout the Atomic Era. Using the novel ²³³U/²³⁶U signature, we distinguished and quantified ²³⁶U inputs from global fallout (45.4-52.1%), Chernobyl accident (0.3-1.8%), and discharges from civil nuclear industries (46.1-54.3%) to the Baltic Sea. We estimated the total release of ²³³U (7-15 kg) from the atmospheric nuclear weapon testing and pinpointed the ²³³U peak signal in the mid-to-late 1950s as a potential time marker for the onset of the Anthropocene Epoch. This work also provides fundamental ²³⁶U data on Chernobyl accident and early discharges from civil nuclear facilities, prompting worldwide ²³³U-²³⁶U tracer studies. We anticipate our data to be used in a broader application in model-observation interdisciplinary research on water circulation and pollutant dynamics in the Baltic Sea.

The nature of Pu-bearing particles from the Maralinga nuclear testing site, Australia

The high-energy release of plutonium (Pu) and uranium (U) during the Maralinga nuclear trials (1955–1963) in Australia, designed to simulate high temperature, non-critical nuclear accidents, resulted in wide dispersion µm-sized, radioactive, Pu–U-bearing ‘hot’ particles that persist in soils. By combining non-destructive, multi-technique synchrotron-based micro-characterization with the first nano-scale imagining of the composition and textures of six Maralinga particles, we find that all particles display intricate physical and chemical make-ups consistent with formation via condensation and cooling of polymetallic melts (immiscible Fe–Al–Pu–U; and Pb ± Pu–U) within the detonation plumes. Plutonium and U are present predominantly in micro- to nano-particulate forms, and most hot particles contain low valence Pu–U–C compounds; these chemically reactive phases are protected by their inclusion in metallic alloys. Plutonium reworking was observed within an oxidised rim in a Pb-rich particle; however overall Pu remained immobile in the studied particles, while small-scale oxidation and mobility of U is widespread. It is notoriously difficult to predict the long-term environmental behaviour of hot particles. Nano-scale characterization of the hot particles suggests that long-term, slow release of Pu from the hot particles may take place via a range of chemical and physical processes, likely contributing to on-going Pu uptake by wildlife at Maralinga.

Partitioning of uranium in contaminated bottom sediments: The meaning of fractionation

Sequential extraction tests were used to study partitioning of U in the bottom sediments of two reservoirs that have been used for the temporary storage of nuclear waste at the "Mining and Chemical Combine" (Zheleznogorsk, Krasnoyarsk region, Russia). Various sequential extraction protocols were applied to the bottom sediment samples and the results compared with those obtained for laboratory-prepared simulated samples with different speciation and partitioning, e.g., U(VI) sorbed onto various inorganic minerals and organic matter, as well as uranium oxides. The distributions of uranium in fractions extracted from simulated and actual contaminated samples were compared to shed light on the speciation of U in the bottom sediments. X-ray absorption spectroscopy, X-ray diffraction, and scanning electron microscopy were also used to analyze the partitioning of U in contaminated sediments. We also compared the results obtained using the spectroscopic and microscopic techniques, as well as sequential extraction.

Differentiating Fukushima and Nagasaki plutonium from global fallout using 241Pu/239Pu atom ratios: Pu vs. Cs uptake and dose to biota

Plutonium (Pu) has been released in Japan by two very different types of nuclear events - the 2011 Fukushima accident and the 1945 detonation of a Pu-core weapon at Nagasaki. Here we report on the use of Accelerator Mass Spectrometry (AMS) methods to distinguish the FDNPP-accident and Nagasaki-detonation Pu from worldwide fallout in soils and biota. The FDNPP-Pu was distinct in local environmental samples through the use of highly sensitive ²⁴¹Pu/²³⁹Pu atom ratios. In contrast, other typically-used Pu measures (²⁴⁰Pu/²³⁹Pu atom ratios, activity concentrations) did not distinguish the FDNPP Pu from background in most 2016 environmental samples. Results indicate the accident contributed new Pu of ~0.4%-2% in the 0-5 cm soils, ~0.3%-3% in earthworms, and ~1%-10% in wild boar near the FDNPP. The uptake of Pu in the boar appears to be relatively uninfluenced by the glassy particle forms of fallout near the FDNPP, whereas the ^134,137Cs uptake appears to be highly influenced. Near Nagasaki, the lasting legacy of Pu is greater with high percentages of Pu sourced from the 1945 detonation (~93% soils, ~88% earthworm, ~96% boar). The Pu at Nagasaki contrasts with that from the FDNPP in having proportionately higher ²³⁹Pu and was distinguished by both ²⁴⁰Pu/²³⁹Pu and ²⁴¹Pu/²³⁹Pu atom ratios. However, compared with the contamination near the Chernobyl accident site, the Pu amounts at all study sites in Japan are orders of magnitude lower. The dose rates from Pu to organisms in the FDNPP and Nagasaki areas, as well as to human consumers of wild boar meat, have been only slightly elevated above background. Our data demonstrate the greater sensitivity of ²⁴¹Pu/²³⁹Pu atom ratios in tracing Pu from nuclear releases and suggest that the Nagasaki-detonation Pu will be distinguishable in the environment for much longer than the FDNPP-accident Pu.

Radiocesium distribution and mid-term dynamics in the ponds of the Fukushima Dai-ichi nuclear power plant exclusion zone in 2015-2019

This study analyzes the ¹³⁷Cs behavior in the ponds of Okuma Town from 2015 to 2019 in the Fukushima Dai-ichi nuclear power plant (FDNPP) exclusion zone. A decline in both particulate and dissolved ¹³⁷Cs activity concentrations was revealed. The decline rate constants for the particulate ¹³⁷Cs activity concentration were found to be higher than for the dissolved ¹³⁷Cs activity concentration. In terms of seasonality the dissolved ¹³⁷Cs concentrations were higher from June to October, depending on the specific pond and year, most likely due to temperature dependence of ¹³⁷Cs desorption from frayed edge sites of micaceous clay minerals. The apparent K_d(¹³⁷Cs) in the studied ponds, in absolute value, appeared to be much higher than that for closed and semi-closed lakes of the Chernobyl contaminated area; however, these were comparable to the values characteristic of the rivers and reservoirs of the FDNPP contaminated area. The apparent K_d(¹³⁷Cs) in the suspended sediment-water system was observed to decrease over time. It was hypothesized that this trend was associated with the decomposition of glassy hot particles. Relying on the theory of selective sorption and fixation, the exchangeable radiocesium interception potential, RIP^ex(K) was estimated using data on ¹³⁷Cs speciation in the surface bottom-sediment layer and its distribution in the sediment-water system. For the studied ponds, RIP^ex(K) was on the average 2050 mEq/kg, which is within the range of values measured in laboratory studies reported in the literature.

Current radiological situation in areas of Ukraine contaminated by the Chornobyl accident: Part 2. Strontium-90 transfer to culinary grains and forest woods from soils of Ivankiv district

Some of the highest ⁹⁰Sr activity concentrations recorded beyond the Chornobyl Exclusion Zone occur in the Ivankiv district of Ukraine, located approximately 50 km south of the power plant, an area which nonetheless remains important for agricultural production. Although characterized by soils with low exchangeable calcium values, which can enhance the bioavailability of certain radionuclides, information on the transfer of ⁹⁰Sr to food crops and trees in the region has remained limited to date. Analysis of 116 grain samples (wheat, rye, oat, barley or Triticale) collected from fields in 13 settlements in the region between 2011 and 2019 revealed ⁹⁰Sr and ¹³⁷Cs activity concentrations above Ukrainian limits in almost half of those samples, with annual averages exceeding this limit in four of those nine years (most recently in 2018) and with no clear evidence for a declining trend over time. Analysis of paired sandy soil samples from the same fields yielded concentration ratios for transfer of ⁹⁰Sr from soils to grains that were on average 3 times higher than that specified by the IAEA. In addition, three quarters of wood samples collected from the trunks of trees (primarily pines) from 12 locations in the same district between 2015 and 2019 contained ⁹⁰Sr activity concentrations in excess of the Ukrainian limits for firewood (60 Bq/kg), with levels more than four times that limit at one location and again no evidence for decline over time. A single sample of ash collected from a domestic wood-burning oven in the district contained ⁹⁰Sr at a level 25 times higher than in the most contaminated wood sample collected in this study. Overall these results reveal additional facets of the ongoing legacy of Chornobyl contamination within the Ivankiv district, and the diversity of pathways by which local residents may be exposed to radionuclides. They also highlight the dangers associated with the current lack of routine and comprehensive environmental and food monitoring programs within the region, especially at a time in which the use of locally-sourced wood for biomass energy generation is set to expand markedly.

The plutonium isotopes and strontium-90 determination in hot particles by characteristic X-rays

This paper reports the developed non-destructive methods for the plutonium isotopes and strontium-90 content determination in hot particles and other samples. The proposed methods are based on the measurement of the characteristic X-rays accompanying the decay of these radionuclides. For hot particles of NPP accident origin, the proposed method's error limits are 10-15% for hot particles (samples) with activity above 100 Bq and 15-20% for hot particles (samples) with activity less than 100 Bq. For explosive particles, the determination accuracy is 10-15% for activity more than 5 Bq and 20-30% for 0.1-5 Bq activity. The accuracy of the proposed method for determining ⁹⁰Sr in samples with its specific content of more than 10⁴ Bq/sample is 5%, with ~10² Bq/sample its content is 15-20%. The cost of one sample measurement and the processing time of these methods are significantly reduced compared to traditional studies. The proposed methods are reasonably simple measurement methods and can be carried out even in the field condition. They open up new possibilities for the quick search and study of hot particles and environmental samples.

Evaluation of uncertainties in environmental impact assessment of naturally occurring radiation exposure situations on example of undisturbed and legacy NORM sites in the Fen Complex, Norway

The risk from naturally occurring radioactive materials (NORM) has been extensively assessed, and this has led to the integration of specific NORM radiation protection requirements within the latest EU Directive 2013/59. Nevertheless, it has been internationally recognised that remaining NORM knowledge gaps and uncertainties now present similarly significant issues in addressing recent regulatory requirements. The multi-tiered nature of environmental impact assessment (EIA) implies per se possibility for uncertainties, but when EIA at radiation exposure sites includes consideration of sites with multiple radiation and contamination sources, different ecosystem transport pathways, effects and risks by applying different parameters and models, level of overall uncertainty increases. The results of EIA study in the Fen area in Norway, comprised of undisturbed and legacy NORM sites, have been evaluated in this analysis, in order to identify all existing input uncertainties and how they may impact the final conclusions, and thus, influence any subsequent decision-making. The main uncertainties have been identified in the measurement and exposure analysis tier, and were related to the heterogeneous distribution of radionuclides, radionuclide speciation, as well as to generic variability issues in the concepts used for mobility and biota uptake analysis (such as distribution coefficient, transfer factors and concentration ratios) as well as radioecological modelling. The uncertainties in the input values to the calculation of the dose arising from radon exposure in the Fen area led to an overall elevated uncertainty of the magnitude of the radiation exposure dose of humans. It has been concluded that an integrated, ecosystem-based approach with consideration of complexity of prevailing environmental conditions and interconnections must be applied to fully understand possible radiation effects and risks.

Validation of a fuel particle dissolution model with samples from the Red Forest within the Chernobyl exclusion zone

The contamination in the near exclusion zone of the Chernobyl nuclear power plant (ChNPP) with ⁹⁰Sr, ^238-240Pu and ²⁴¹Am is associated with irradiated nuclear fuel particles. Fit for purpose models enabling long term prediction of mobility and bioavailability of particle-associated radionuclides are crucial for radiation protection of humans and the environment, as well as for planning of remediation measures and future land use. In the present work, a dynamic fuel particle dissolution model developed in 1999-2002 is described and validated using data based on sampling in 2015. The model is based on the characterization of the radionuclide source term of the waste in a shallow sub-surface radioactive waste storage, trench #22, in the Chernobyl Pilot Site (CPS) located in the Red Forest, 2.5 km west of the ChNPP, as well as the description of physical and chemical properties of the fuel particles and subsequent radionuclide leaching into the soil solution. Transformation rate constants of the fuel particle dissolution model related to topsoil, radioactive waste trench and submerged materials, and drained cooling pond sediments, should largely control the mobility and bioavailability of radionuclides (e.g., solubility in the soil, migration to groundwater and transfer to plants). The predicting power of the Chernobyl fuel particle dissolution model with respect to radionuclide leaching dynamics was validated using samples from the same experimental site, showing that predicted particle leaching and subsequent mobility and bioavailability were within 46 ± 3% of the observed data. Therefore, linking source- and release-scenario dependent characteristics of radioactive particles to their potential weathering can provide information that can be implemented in impact assessments models for existing contaminated areas as well as for future events.

Effects of radiation on radial growth of Scots pine in areas highly affected by the Chernobyl accident

The effects of radiation on radial growth of Scots pine (Pinus sylvestris L.) affected by the Chernobyl accident were studied at five sites with different deposition levels. The study sites were chosen along a high gradient of depositions at the distance of a few hundred meters in the forests with similar forest characteristics. Air dose rates varied at the sites from the background values up to 30 μGy h^-1 as of December 1, 2016. Scots pine trees exposed to sub-lethal doses of 8.6-13.2 Gy at the "Red Forest" site did not demonstrate deviations in formation of annual rings 30 years after the Chernobyl accident compared to trees with lower doses and control trees. Variation with time in annual rings thickness did reveal that the effect of radiation in trees growing at the sites with different contamination not detectable in 1986 and 1987. Conversely, the effects were clear observed in a later period in 1989-1991, i.e. 3-5 years after the accident. Until 2000, there were statistically significant differences in the annual rings growth rates of Scots pine trees exposed to external absorbed dose rates of 4.4-6.7 mGy h^-1 as estimated for June 1, 1986 (or 19.5-30.0 μGy h^-1 as of December 1, 2016) compared with the trees of the other sites studied. The results comply with the conclusions from research with acute pine exposure conducted in the Kyshtym area in 1975-1984.

The transfer of 239+240Pu, 241Am, 137Cs and 90Sr to the tissues of horses

Horses are important food sources in several countries however, data on their radionuclide uptake is less available than for many other farm animals. Information on the transfer of artificial radioisotopes from the environment to the food supply is necessary for internal dose assessment and assuring the safety of the population relying on this food source. This study provides data for a less studied farm animal and, in the case of ²⁴¹Am and ^239+240Pu, relatively poorly studied radionuclides with respect to transfer to animal products. The transfer parameters for ^239+240Pu, ²⁴¹Am, ¹³⁷Cs and ⁹⁰Sr to the organs of 1-year old fillies, 10-year old mares and through the placental barrier into foetuses were quantified after 60-days feeding with contaminated soil or diet contaminated by a leachate solution. The transfer of radionuclides from ingested soil to tissues was generally lower, by up to three orders of magnitude, than from a diet contaminated by a leachate solution. The ingestion of soil is a particularly important source of radionuclide intake to grazing animals in the Semipalatinsk Test Site. For ²⁴¹Am there is a lack of available data, the two singular entries for mutton and beef in the IAEA handbook are higher than all values observed in the current study. The maximum observed transfer factor for ²⁴¹Am was 72 ± 22*10^-5 d kg^-1 FW in the liver of the mare fed with leachate contaminated feed. For ^239+240Pu the maximum transfer factor was 31.8 ± 8*10^-5 d kg^-1 FW observed also in the liver of the mare fed with leachate contaminated feed. The filly fed with leachate contaminated feed had the highest transfer parameter value for ¹³⁷Cs, 35.3*10^-3 d kg^-1 FW. The highest ⁹⁰Sr transfer factor was found in the ribs of the filly fed leachate contaminated feed, 720 ± 144 *10^-3 d kg^-1 FW. The results presented in this paper can be used to improve the current internal dose estimates from the ingestion of horse meat produced in the area, however they are based on a low sample size; future studies need to use a larger number of animals.

Optimising sampling strategies for emergency response: Soil sampling

The novel approach for optimising soil sampling strategies in areas affected by radionuclides is suggested. Major factors influencing the efficiency of soil sampling strategies, including (number of samples, sampling area size, sampling depth and spatial resolution of the sample sites are examined to provide optimisation of the soil sampling plan. The experimental field studies to validate the suggested approach were performed in 25 sampling units ranging from 1.2 × 1.2 m to 60 × 60 m size. The sampling units were selected on arable farmlands, natural meadow and former agricultural land), as well as coniferous and deciduous forests with contamination density of ¹³⁷Cs ranging from 2.8 kBq·m^-2 to 24.5 MBq·m^-2. The studied areas were contaminated by both the global fallout and the Chernobyl radioactive particles of different types. To determine the values of standard deviation of the log of the soil contamination density of ¹³⁷Cs, 25 to 256 soil samples were collected with an increment of 0.07-10 m within each sampling unit. It was found that the values of standard deviation of the log of the soil contamination density of ¹³⁷Cs were not dependent on the mean contamination density, the type of radioactive deposition and the landscape features. The mean value of standard deviation calculated for all sites studied was estimated as 0.44 ± 0.15 and 0.30 ± 0.10 for the sampling area 0.001 m² (∅37 mm) and 0.005 m² (∅80 mm) at the relative measurement uncertainties lower than 10% (CI = 95%). Concentrations of ¹³⁷Cs in the soil samples were statistically independent when sampling points were situated at a distance larger than 1 m one from each other. A simple method was developed for assessing minimum sample sizes required for estimation of the median or the geometric mean of radionuclide soil contamination with a relative uncertainty set by the user. The approach was also suggested for estimation of the uncertainty of soil contamination for the case of composite samples. The approach was implemented in the Ukrainian national requirements for assessment of quality of the soil.

Characterization of radioactive particles from the Dounreay nuclear reprocessing facility

Radioactive particles originating from nuclear fuel reprocessing at the United Kingdom Atomic Energy Authority's Dounreay Facility were inadvertently released to the environment in the late 1950s to 1970s and have subsequently been found on site grounds and local beaches. Previous assessments of risk associated with encountering a particle have been based on conservative assumptions related to particle composition and speciation. To reduce uncertainties associated with environmental impact assessments from Dounreay particles, further characterization is relevant. Results of particles available for this study showed variation between Dounreay Fast Reactor (DFR) and Materials Test Reactor (MTR) particles, reflecting differences in fuel design, release scenarios, and subsequent environmental influence. Analyses of DFR particles showed they are small (100-300 μm) and contain spatially correlated U and Nb. Molybdenum, part of the DFR fuel, was identified at atomic concentrations below 1%. Based on SR-based micrometer-scale X-ray Absorption Near Edge Structure spectroscopy (μ-XANES), U may be present as U(IV), and, based on a measured Nb/U atom ratio of ~2, stoichiometric considerations are commensurable with the presence of UNb₂O₇. The MTR particles were larger (740-2000 μm) and contained U and Al inhomogeneously distributed. Neodymium (Nd) was identified in atomic concentrations of around 1-2%, suggesting it was part of the fuel design. The presence of U(IV) in MTR particles, as indicated by μ-XANES analysis, may be related to oxidation of particle surfaces, as could be expected due to corrosion of UAl_x fuel particles in air. High ²³⁵U/²³⁸U atom ratios in individual DFR (3.2 ± 0.8) and MTR (2.6 ± 0.4) particles reflected the presence of highly enriched uranium. The DFR particles featured lower ¹³⁷Cs activity levels (2.00-9.58 kBq/particle) than the MTR (43.2-641 kBq ¹³⁷Cs/particle) particles. The activities of the dose contributing radionuclides ⁹⁰Sr/⁹⁰Y were proportional to ¹³⁷Cs (⁹⁰Sr/¹³⁷Cs activity ratio ≈ 0.8) and particle activities were roughly proportional to the size. Based on direct beta measurements, gamma spectrometry, and the VARSKIN6 model, contact dose rates were calculated to be approximately 74 mGy/h for the highest activity MTR particle, in agreement with previously published estimates.

Radioactive particles released from different sources in the Semipalatinsk Test Site

A total of 456 nuclear tests were performed from 1949 to 1989 at the Semipalatinsk Test Site (STS) in Kazakhstan, as part of the nuclear weapon test program of the USSR. To identify if radionuclides such as ¹³⁷Cs, ⁹⁰Sr, ²⁴¹Am, ^239+240Pu were associated with radioactive particles, soil samples were collected at selected contaminated sites (i.e. Experimental field, Excavation sites, Fallout plume sections, Background global fallout area, and Degelen Mountain) within the STS. A series of techniques have been applied to identify the size distributions of radionuclides, the prevalence of radioactive particles in soils, and the degree of leachability of particle associated radionuclides by different agents. In addition, selected particles were characterized non-destructively using digital autoradiography, environmental scanning electron microscopy (ESEM) and synchrotron radiation microscopic X-ray techniques. Radioactive particles were identified at all sites; large vitrified particles were identified at epicenters, and the size of particles decreased along the plume with distance from the epicenters. The radioactive particles identified varied in composition, size and leachability. In general, ¹³⁷Cs, ²⁴¹Am, ^239+240Pu were strongly associated with solid phases (90-99%) in soils, while ⁹⁰Sr exhibited much greater variability. The fraction of ⁹⁰Sr present in exchangeable forms was low close to epicenters, while the extractability increased along the plume as the particle size distribution decreased. The results suggest that at least four different types of radioactive particles are present at STS: 1) Relatively large spherical particles with a shiny glazed, melted surface with internal porous structure, and surface layers enriched in transuranic elements, identified at epicenters of detonations, 2) Vitrified irregular particles probably originating from debris of nuclear device with interactions from soil components, also identified at epicenters of detonations, 3) Particles with visually unchanged structure, containing micro-inclusions of fissile materials associated with soil components, also identified at epicenters; 4) Particles with amorphous structures associated with underground detonations, identified in soil in the vicinity of the entrance of the detonation tunnels at the Degelen Mountain. These were probably formed by secondary mechanisms due to sorption and fixation of radionuclides. Thus, the present work shows that the STS should be considered an important observatory site to link particle characteristics to specific sources and to release conditions as well as to ecosystem transfer of particle associated radionuclides.

Assessing relative biomarker responses in marine and freshwater bivalve molluscs following exposure to phosphorus 32 (32P): Application of genotoxicological and molecular biomarkers

Anthropogenic radionuclides can enter water bodies through accidental or controlled discharges. In order to assess their potential impact, understanding the link between exposure, tissue specific bioaccumulation and radiation dose rate, to biological or biomarker responses in aquatic biota is required. Adopting an integrated, multi-biomarker, multi-species approach, we have investigated potential biological responses induced by short-lived radionuclide, phosphorus-32 (³²P, radiophosphorus) in two ecologically important mussel species, the freshwater Dreissena polymorpha (DP) and marine Mytilus galloprovincialis (MG). Adult individuals were exposed to ³²P for 10 days, to acquire nominal whole-body average dose rates of 0.10, 1 and 10 mGy d^-1, which encompass a screening value of 10 μGy h^-1 (0.24 mGy d^-1), in accordance with the ERICA tool. Following exposure, a suite of genotoxic biomarkers (DNA damage, γ-H2AX induction and micronucleus [MN] formation) were measured in gill and digestive gland tissues, along with transcriptional expression of selected stress-related genes in both the species (i.e. hsp70/90, sod, cat and gst). Our results demonstrate the relationship between tissue specific dosimetry, where ³²P induced a dose-dependent increase, and biological responses independent of species. Gene expression analysis revealed little significant variation across species or tissues. Overall, MG appeared to be more sensitive to short-term damage (i.e. high DNA damage and γ-H2AX induction), particularly in digestive gland. This study contributes to limited knowledge on the transfer and biological impact of radionuclides within differing aquatic systems on a tissue specific level, aiding the development of adequate management and protective strategies.

90Sr Content in the Stemwood of Forests within Ukrainian Polissya

The consequences of the Chernobyl disaster continue to threaten humans and ecosystems across fallout gradient in Northern Ukraine and nearby. Forest ecosystems contain substantial stocks of long-lived radionuclide 90Sr which was leached from the fuel matrix during the disaster. Nowadays, there is a lack of information about current transfer factors (TF) of this radionuclide from soil to the stemwood of native tree species. We have estimated 90Sr content in the forest stemwood of three tree species utilizing models of their growth and yield and collected woody samplings. TFs provided here vary greatly across studied tree species (18.0 × 2.1±1, 8.7 × 2.8±1, and 10.4 × 6.0±1 n × 10−3 m2·kg−1 (geometrical mean (GM) ± geometrical standard deviation, GSD) for the above species, respectively) and together with indicators of soil contamination allow us to reliably assess local stocks in the stemwood. Silver birch stands are estimated to deposit the highest 90Sr stocks. Herewith, at 25 years old Black alder stands could accumulate higher stocks (up to 35 MBq·ha−1) under rich growth conditions. TFs obtained in this study substantially exceed values provided by the International Atomic Energy Agency for studied tree species and thus could entail respective restrictions on use of firewood across large areas in Ukrainian Polissya. Data provided here may be harnessed to support decisions of respective stakeholders to provide credibly safe management of the contaminated forest ecosystems.

Linking heterogeneous distribution of radiocaesium in soils and pond sediments in the Fukushima Daiichi exclusion zone to mobility and potential bioavailability

During the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident in 2011 significant amounts of radiocaesium were released into the atmosphere from the reactor units 1, 2 and 3. This caused a non-uniform deposition, in composition and direction, of ¹³⁴Cs and ¹³⁷Cs in the near field (<30 km) from the reactors. In this work, we elucidate the influence of speciation, including radioactive particles, on mobility and potential bioavailability of radiocaesium in soils and sediments from sites located in different directions and distances from the FDNPP. Samples collected in September 2016 were characterized and subjected to sequential chemical extractions and simulated gastrointestinal fluid leaching, and the ¹³⁷Cs and ¹³⁴Cs activities were determined in bulk, grain-size and extracted fractions. The results show that radiocaesium was mainly irreversibly bound and in an inert form. Combined, the two forms contained >90% of the activity present in soils and ~84% in sediments. Digital autoradiography revealed that the inert fraction was predominantly associated with heterogeneities, an indication of radioactive particles. The frequency of heterogeneities was correlated with ¹³⁷Cs activity concentrations, and both were in agreement with the ambient equivalent air doses measured in situ during sampling. Moreover, in situ gamma spectrometry measurements were used in the InSiCal software tool to derive ¹³⁴Cs and ¹³⁷Cs surface contamination. Soil activity concentrations and contamination density estimations, decay-corrected to the day of the FDNPP accident, resulted in ¹³⁴Cs/¹³⁷Cs ratios that match the reported release and deposition plumes from the reactor units. Overall, these results demonstrate the persistence of the particle contamination in the Fukushima near field and highlight the importance of including radioactive particles in environmental impact assessments.

Analytical techniques for charactering radioactive particles deposited in the environment

Since 1945, a series of nuclear and radiological sources have contributed to the release of radioactive particles containing refractory elements into the environment. Several years of research have demonstrated that the particle composition will depend on the source, while the release scenarios will influence particle properties of relevance for environmental transfer. Radioactive particles can also carry sufficient amount of radioactivity (MBq) and represent point sources of radiological concern. Most radiological assessment models, however, are based on bulk concentrations, assuming that radionuclides in the environment are evenly distributed. In contrast, radioactive particles and thereby doses are unevenly distributed, while leaching of radionuclides from particles prior to measurements can be partial, potentially leading to underestimation of inventories. For areas affected by particle contamination, information on particle characteristics controlling the particle weathering rates and remobilization of particle associated radionuclides will therefore be essential to reduce the overall uncertainties of the impact assessments. The present paper will focus on analytical strategies, from screening techniques applicable for identifying hot spots in the field, fractionation techniques and single particle extraction techniques as a preparatory mean to apply non-destructive solid state speciation techniques, till leaching techniques applied sequentially to obtain information on binding mechanisms, mobility and potential bioavailability. Thus, a combination of techniques should be utilized to characterize radioactive particles in order to improve environmental assessments for areas affected by radioactive particle fallout.

Nanometer-micrometer sized depleted uranium (DU) particles in the environment

Depleted uranium (DU) is a waste product from uranium enrichment that has several civilian and military applications. Significant amounts of DU in the form of particles or as fragments have been released into the environment as a consequence of military use of DU munitions, of industrial releases and of aircraft accidents. Thus, the present paper summarizes present knowledge on nanometer-micrometer sized depleted uranium (DU) particles collected in areas contaminated with such particles. Analysis of DU particles released to the environment has shown that uranium can be present in different crystalline structures and in different oxidation states. The weathering rates of DU particles and the subsequent remobilization of uranium species are also strongly connected to the oxidation state and crystalline phases of uranium, influencing the mobility and potential ecosystem transfer. Therefore, as has been observed for radioactive particles released from most nuclear events, the characteristics of DU particles can be linked to the source term and the release scenario as well as to environmental transformation processes. Although the radiation dose and radiotoxicity of DU is less than from natural occurring uranium, the mobility of U from oxidized DU and the associated chemical toxicity could be significantly higher than from natural UO₂. The present paper summarizes present knowledge on depleted uranium particles identified in the environment.

Plutonium and other radionuclides persist across marine-to-terrestrial ecotopes in the Montebello Islands sixty years after nuclear tests

Since the 1956 completion of nuclear testing at the Montebello Islands, Western Australia, this remote uninhabited island group has been relatively undisturbed (no major remediations) and currently functions as high-value marine and terrestrial habitat within the Montebello/Barrow Islands Marine Conservation Reserves. The former weapons testing sites, therefore, provide a unique opportunity for assessing the fate and behaviour of Anthropocene radionuclides subjected to natural processes across a range of shallow-marine to island-terrestrial ecological units (ecotopes). We collected soil, sediment and biota samples and analysed their radionuclide content using gamma and alpha spectrometry, photostimulated luminescence autoradiography and accelerator mass spectrometry. We found the activity levels of the fission and neutron-activation products have decreased by ~hundred-fold near the ground zero locations. However, Pu concentrations remain elevated, some of which are high relative to most other Australian and international sites (up to 25,050 Bq kg-1 of 239+240+241Pu). Across ecotopes, Pu ranked from highest to lowest in the following order: island soils > dunes > foredunes > marine sediments > and beach intertidal zone. Low values of Pu and other radionuclides were detected in all local wildlife tested including endangered species. Activity concentrations ranked (highest to lowest) terrestrial arthropods > terrestrial mammal and reptile bones > algae > oyster flesh > whole crab > sea turtle bone > stingray and teleost fish livers > sea cucumber flesh > sea turtle skin > teleost fish muscle. The three detonations (one from within a ship and two from 30 m towers) resulted in differing contaminant forms, with the ship detonation producing the highest activity concentrations and finer more inhalable particulate forms. The three sites are distinct in their 240/239Pu and 241/239Pu atom ratios, including the Pu transported by natural process or within migratory living organisms.

Environmental behaviour of radioactive particles from chernobyl

Long-term environmental behaviour of radioactive particles released during the Chernobyl accident and deposited in sandy topsoil in Ivankiv district of Kyiv Region (Ukraine), in radioactive trench waste materials from the Red forest, and in bottom sediments from the Cooling pond has been assessed. The efficiency of the models describing the dissolution/weathering rates of U fuel particles developed 15-20 years ago was tested, and their predictions for the dynamics of remobilization, mobility and plants uptake of ⁹⁰Sr were confirmed. It was found that at present in the topsoil and in radioactive trench waste material, total dissolution of fuel particles of low chemical stability (UO_2+x) has occurred and about half of the non-oxidized chemically stable fuel particles (UO₂) has also dissolved, indicating radiological stabilization of the environment and that the mobile fraction of radionuclides would be reduced in the future. The biological availability of ⁹⁰Sr in topsoil due to fuel particles dissolution has reached maximum values and further decrease is expected. The presence of chemically extra-stable fuel particles (U-Zr_y-O_x) in environments should be taken into account when the total radionuclides activity concentrations are assessed during radioactive materials management. It was shown that nearly half of the ⁹⁰Sr activity remained as part of the non-dissolved UO₂ fuel particles at the time of the study. Taking into consideration that 31 ± 4% of the radionuclide activities were still associated with non-dissolved chemically extra-stable particles (U-Zr_y-O_x) in radioactive trench waste materials from the Red forest, increased dissolution should not be expected in the near future. The physico-chemical form of radionuclides in air exposed sediments from the Cooling pond were determined, and results showed that about 70-80% of total ⁹⁰Sr, ²⁴¹Am and plutonium isotopes activity were associated with U fuel particles. The low dissolution rate of radionuclides from the pond sediments is attributed to prolonged slightly alkaline pH in the medium due to zebra mussel residues. According to new data, the emission value of ²³⁸Pu associated with fuel particles released during the Chernobyl accident amounted to 1.8 × 10¹³Bq (1.2% of the activity in the reactor) and ⁹⁰Sr amounted to 2.6 × 10¹⁵Bq (1.5% of the activity in the reactor).

Radioactive particles in the Yenisei River floodplain (Russia): Characterization, leaching and potential effects in the environment

The operation of the Mining-and-Chemical Combine (MCC), the largest producer of weapons-grade plutonium in Russia, has resulted in radioactive contamination of the Yenisei River floodplain. Investigations carried out in Novosibirsk and Krasnoyarsk institutes have shown that the floodplain of the Yenisei downstream of the MCC is contaminated by radioactive particles (RP) of various types and activities. Analytical characterization of the RP showed that most of them were fuel particles, which were carried into the Yenisei after incidents at the MCC reactors. The plutonium and caesium isotope ratios (²³⁸Pu/^239,240Pu; ¹³⁷Cs/¹³⁴Cs) vary substantially between the particles, indicating different source terms and time intervals when the RP were formed. In addition to fuel RP, there were particles that contained activation radionuclides. The experiment on dissolution of RP using the model solution (the simulated stomach fluid) showed different cumulative extractions of radionuclides from the particles: ⁶⁰Co and ¹³⁷Cs extractions were the lowest, the extracted fractions of europium and americium isotopes were the largest, and plutonium occupied an intermediate position. High concentrations of radionuclides in RP are sources of exposure of organisms in aquatic and terrestrial ecosystems to low radiation doses. The plant bioassays of the effects of γ-radiation from RP showed the effect of low doses of γ-radiation on growth parameters of aquatic plant Elodea canadensis growing in the Yenisei River floodplain. The presence of RP from different sources in the Yenisei River floodplain makes this region a unique site for studying environmental effects of the particles.

Radiological evaluation of the transuranic remaining contamination in Palomares (Spain): A historical review

This paper shows the studies carried out in Palomares (Almería, Spain) following the ground dispersion of nuclear material as a result of the air crash accident that took place in 1966, in which four nuclear bombs were involved. As a consequence of the Palomares accident, plutonium (Pu) and uranium (U) were dispersed over an area of approximately 2.3 km² due to the chemical explosion of two of them. The most relevant activities carried out by CIEMAT, along with other national and international institutions in the Palomares scenario are detailed. These activities, performed for over 50 years, focus mainly in the characterization of the contamination source, in the continuous environmental and personal radiological monitoring programs, in the construction of a detailed superficial and 3-D mapping distribution of the remaining contamination and in the evaluation of the bioavailability of the transuranics still remaining in the area.

Radioecology in CONFIDENCE: Dealing with uncertainties relevant for decision making

The CONFIDENCE project is performing research on uncertainties in emergency management and post-accident recovery. It concentrates on the early and transition phases of an emergency, but considers also longer-term decisions made during these phases. To ensure success, the project brings together expertise from four European Radiation Protection Research Platforms (NERIS, MELODI, ALLIANCE and EURADOS) and also from the area of social sciences and humanities. This paper presents an overview of the CONFIDENCE project with a focus on CONFIDENCE's consideration of the radioecology required to support emergency management and post-accident recovery. For instance, operational decisions concerning land and foodchain management rely on radioecological models that are at present mostly based on simple, but highly uncertain, transfer ratios to predict contamination in foodstuffs. CONFIDENCE will investigate if process-based models are better suited to reducing uncertainties associated with empirical ratio based models. Model improvements and uncertainty reduction might be also possible by better evaluating past experience from Chernobyl and Fukushima.