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Contamination map of the Maralinga test sites based on a 1987 aerial survey of 241 Am (as an indicator of plutonium). The largest plumes are associated with the approximately 22 kg of plutonium dispersed from safety tests conducted at the Taranaki site. The most contaminated areas were remediated in the 1990s. Reprinted from Ref. 266 with permission of MARTAC.

Contamination map of the Maralinga test sites based on a 1987 aerial survey of 241 Am (as an indicator of plutonium). The largest plumes are associated with the approximately 22 kg of plutonium dispersed from safety tests conducted at the Taranaki site. The most contaminated areas were remediated in the 1990s. Reprinted from Ref. 266 with permission of MARTAC.

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This chapter discusses key aspects related to the assessment of the environmental impact of plutonium, such as sources, speciation, and underlying processes important for ecosystem transfer, mobility, and bioavailability.

Citations

... In excess of 6 t of Pu was released to the environment during underground and atmospheric testing of nuclear weapons. 1 For example, at the Hanford Reservation, WA, U.S.A., it is estimated that tens of kilograms of Pu and other actinide elements 2,3 were discharged into the subsurface between 1945 and 1990 at roughly 20 different locations. 2 The use of nuclear power for both civil and military applications has also led to Pu production, with 2630 t of Pu accumulated, 1 and an additional ≈70 t of Pu is added to the global inventory annually from electricity production. ...
... In excess of 6 t of Pu was released to the environment during underground and atmospheric testing of nuclear weapons. 1 For example, at the Hanford Reservation, WA, U.S.A., it is estimated that tens of kilograms of Pu and other actinide elements 2,3 were discharged into the subsurface between 1945 and 1990 at roughly 20 different locations. 2 The use of nuclear power for both civil and military applications has also led to Pu production, with 2630 t of Pu accumulated, 1 and an additional ≈70 t of Pu is added to the global inventory annually from electricity production. 4 Currently, at nuclear power plants across the U.S., 6000 t of spent fuel are stored temporarily with no permanent storage solution. ...
... If Pu is incorporated into the growing calcite crystals in any appreciable quantity, its concentration in the aqueous solution will decrease through time. Analysis of aliquots of the barrier solutions for the PuVI-1500 and PuVI-700 experiments sampled over time (1,2,3,4,8,9, and 12 days) reveals a decrease in the Pu concentration starting at day 3, at which time crystals have started to form (Figure 3). After 12 days, approximately 30 and 15% of Pu remains in the barrier solution in the PuVI-1500 and PuVI-700 experiments, respectively. ...
... Plutonium is widely spread in the environment because of nuclear weapons testing, accidental and controlled releases of radioactive materials from nuclear facilities, etc. (Harley, 1980;Thakur, Ward, 2018;Geckeis et al., 2019;Romanchuk et al., 2020). Inland waters receive plutonium with atmospheric fallouts, direct discharges of liquid wastes from nuclear facilities, and washouts from the water catchment area. ...
... Compared to other artificial radionuclides of similar origin, 239 Pu and 240 Pu, being an alpha emitter, dominate the long-term radiotoxicity in the environment due to their long physical half-lives, 24,110 years and 6563 years, respectively (Chu et al., 1999). Speciation and further behavior of plutonium in the environment depends on the initial source and form of discharged plutonium, local geochemistry and other environmental factors and can vary as environmental conditions change (Salbu, 2000;Sukhorukov et al., 2004;Lindt et al., 2006;Skipperud, Salbu, 2015;Bolsunovsky and Melgunov, 2019;Geckeis et al., 2019;Romanchuk et al., 2020). Biota plays an important role in the transfer of plutonium in the environment through biosorption and bioaccumulation. ...
... The ratio of activity concentrations of plutonium isotopes is used as an indicator of the origin and age of plutonium contamination in the environment (Kershaw et al., 1995;Thakur and Ward, 2018;Geckeis et al., 2019;Kuzmenkova et al., 2020). The 238 Pu/ 239,240 Pu activity ratios in sediments of the Yenisei rose from 0.05 in 2012 to 0.29 in 2014. ...
Article
MOX-fuel production and spent nuclear fuel reprocessing started recently at the Mining-and-Chemical Combine (MCC, Zheleznogorsk, Russia) have caused an increase in controlled releases of plutonium to the Yenisei River. In this study, we analyzed time-dependent trends of plutonium (239,240Pu and ²³⁸Pu) in biota and bottom sediments of the Yenisei during 2008–2019, to estimate comparatively the potential of abundant representatives of biota as bio-monitors of contamination of the Yenisei by plutonium. Gamma-emitting radionuclides (⁴⁰ K; ⁶⁰Co; ¹³⁷Cs; ¹⁵²Eu; ²⁴¹Am) were measured in environmental samples of the Yenisei as well. Samples of bottom sediments, water moss (Fontinalis antipyretica), shining pondweed (Potamogeton lucens), caddisfly larvae with casings (Apatania crymophila), and amphipods (Eulimnogammarus viridis and Palaseopsis cancelloides) were collected downstream and upstream of the radioactive discharge site. Environmental samples of the Yenisei collected downstream of the radioactive discharge site differed considerably in activity concentrations of plutonium but were similar in time-dependent trends of plutonium, reflecting the trends of annual discharges of plutonium. In 2018, the year of a sharp increase in controlled discharge of plutonium, the concentration of 239,240Pu in water moss (26 Bq kg⁻¹ d.w.) was higher than in sediments (14 Bq kg⁻¹ d.w.). In other years, the highest activity concentration of 2391,240Pu was observed in bottom sediments. In view of the higher magnitude of increase in plutonium concentration, water moss and shining pondweed can be considered as more sensitive indicators of increased fresh releases of plutonium than bottom sediments. Taking into account the food-related mechanism of plutonium uptake by amphipods, this representative of biota can be regarded as a sensitive monitor of bioavailable plutonium in the Yenisei.
... Pu and Am are present as cations, while Se mostly occurs in the shape of the negative ions selenite or selenate; Pu and Se are redox-sensitive while Am is not. The properties and the behaviour of these elements in the environment have been extensively reviewed in the literature [12][13][14][15][16] and will not be described in detail here. ...
Article
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The component additive model UNiSeCs II for simulating the physicochemical behaviour of the radionuclides americium, plutonium and selenium in agricultural soils is presented. The model is validated by estimating the distribution coefficients (K d ) of these elements measured in batch experiments from the literature. For all three elements, the resulting average relative deviations from the experimental values are smaller than a factor of 2.5. This indicates that the model has the potential to significantly improve the predictions of radioecological models that normally use tabulated K d values from the IAEA which are known to have large uncertainties. Using UNiSeCs II, the soil solution parameters most important for the partitioning of Am, Pu and Se are identified by single parameter variations.
... The consensus among the international community is that the most favored means of disposal for high-level and long-lived radioactive wastes is in a deep geologic repository. 63,64 To support international waste disposal efforts, interactions and processes that could potentially lead to the release of radionuclides into the geosphere in case of water intrusion or damage to the integrity of such a facility must be well understood. Of these radionuclides, plutonium is important due to its prevalence in both defense and commercial waste and defense related transuranic waste, high alpha radiotoxicity, and long half-life (t½ 239 Pu = 2.41•10 4 a), which allows it to persist and contribute to the overall activity of the waste for over one hundred thousand years. ...
Thesis
This dissertation explores the behavior of plutonium in the presence of ethylenediaminetetraacetic acid (EDTA) under environmentally- and repository-relevant boundary conditions. There are two main research foci: (i) defining the binary interactions between plutonium and EDTA and (ii) probing the impact of major cations of environmental relevance (Ca(II), Fe(II/III)) on the interactions of plutonium and EDTA. The first area of research utilized undersaturation solubility studies, spectrophotometry, and advanced spectroscopic methods as a function of pH and time to investigate the speciation, solubility, and redox reactions in binary Pu-EDTA systems. The second area of research highlights the role of aqueous Ca(II) and iron oxide minerals within Pu-EDTA systems through the use of undersaturation solubility studies, advanced spectroscopic techniques, theoretical modeling efforts, and ternary sorption studies. The results of this dissertation indicate that the investigation of binary systems is not enough to develop a comprehensive understanding of the fate and transport of plutonium; the interplay between different environmental interactions can significantly impact the long-term mobility of plutonium in environmental settings and must be understood to further waste disposal and remediation/containment efforts.
... Essential to reprocessing is the dissolution of the spent fuel, a procedure that increases the potential for contaminant release in liquid waste discharges (Choppin et al., 2013). Reports on radioactive particles found in the vicinity of reprocessing sites indicate that the dissolution of fuel may be incomplete and that residual fuel fragments and particles in the discharges can give rise to radioactive particle contamination in the environment such as in the case of Krasnoyarsk-26, Sellafield, and Dounreay reprocessing facilities (Bolsunovsky et al., 2017;Dennis et al., 2007;Geckeis et al., 2019;Lind, 2006). Failure to recognize the presence of radioactive particles, defined by the International Atomic Energy Agency (IAEA) as "a localized aggregation of radioactive atoms that give rise to an inhomogeneous distribution of radionuclides significantly different from that of the matrix background", may have a number of serious consequences (IAEA, 2011). ...
Article
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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 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%. Results indicated U may be present as U(IV), and, based on a measured U/Nb 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. Results indicate U(IV) presence in MTR particles which may be related to oxidation of the surface. 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 (0.8 ⁹⁰Sr/¹³⁷Cs) 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.
... Various methods were used to identify and isolate radioactive particles. At NMBU, particles were identified using digital autoradiography using Imaging plates (Molecular Dynamics) and a Typhoon (GE Healthcare) scanner (Geckeis et al., 2019;Salbu and Lind, 2020), or by means of sample splitting combined with gamma spectrometry (Bunzl, 1997;IAEA, 2011). Isolated particles were fixed onto carbon double-faced sticky tape and mounted onto Al stubs for further identification of particles in Zeiss EVO 50 variable pressure Environmental Scanning Electron Microscope (ESEM) with an Inca EDX analytical system (Oxford Instruments, Oxford, UK) including a Si(Li) detector (Lind et al., 2013). ...
... The absorption tomograms of the particles from site P2 (HP-08, Figs. 10-12) reveal that below the smooth and regular exterior, several phases of strongly different densities are present as well as quasi-circular vesicles (Figs. 10 and 11), e.g., similar to what has been reported for Trinitite material from the World's first nuclear detonation (Fahey et al., 2010;Holliday et al., 2017), for fallout particles from tower shots at Nevada test site (Miller, 1963;Crocker et al., 1966), and for ellipsoidal and transparent glassy fallout particles from British nuclear tests (Breakaway, Round 4, Maralinga; Mosaic G2, Monte Bello Island) in Australia (Salbu et al., 2018;Geckeis et al., 2019). This may reflect that these particles are formed by condensation/solidification from liquid/gaseous state at high temperature and pressure. ...
... In the particles from epicentres within the Experimental field being subjected to spatially resolved SR based XRDP/XRF analysis, U and Pu are highly correlated (Fig. 12e), similar to that observed at other contaminated sites (e.g., Tel'kem I and II at STS, Palomares, Thule and McGuire Air Force Base), previously determined for actinide containing particles originating from nuclear weapon material (Geckeis et al., 2019;Lind, 2006;Lind et al., 2007). Accelerator mass spectrometry (AMS) measurements of aqua regia leachates of the particle in Fig. 9b yielded a 240 Pu/ 239 Pu atom ratio of 0.040 � 0.009 (Lind, 2006), in agreement with the value of 0.0438 � 0.0001 reported by (Beasley et al., 1998) for a single surface soil sample collected at Ground Zero. ...
Article
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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 extract-ability 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 ra-dionuclides. 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.
... Transferring the particle sample to sensitive EM (electron microscopy) techniques combined with energy dispersive X-ray analysis (EDX), the elemental distribution of particle surfaces can be characterized. For submicrons (nanoparticles, colloids), transmission electron microscopy (e.g., analytical TEM with EDX) is needed to identify Table 1 Analytical tools for characterization of radioactive colloids and particles in environmental samples (modified from IAEA (2011), Salbu et al. (2015) and Geckeis et al., (2019)). ...
Article
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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.
Article
Anthropogenic radionuclides, including long-lived heavy actinides such as americium and curium, represent the primary long-term challenge for management of nuclear waste. The potential release of these wastes into the environment necessitates understanding their interactions with biogeochemical compounds present in nature. Here, we characterize the interactions between the heavy actinides, Am3+ and Cm3+, and the natural lanthanide-binding protein, lanmodulin (LanM). LanM is produced abundantly by methylotrophic bacteria, including Methylorubrum extorquens, that are widespread in the environment. We determine the first stability constant for an Am3+-protein complex (Am3LanM) and confirm the results with Cm3LanM, indicating a ∼5-fold higher affinity than that for lanthanides with most similar ionic radius, Nd3+ and Sm3+, and making LanM the strongest known heavy actinide-binding protein. The protein’s high selectivity over 243Am’s daughter nuclide 239Np enables lab-scale actinide-actinide separations as well as provides insight into potential protein-driven mobilization for these actinides in the environment. The luminescence properties of the Cm3+-LanM complex, and NMR studies of Gd3+-LanM, reveal that lanmodulin-bound f-elements possess two coordinated solvent molecules across a range of metal ionic radii. Finally, we show under a wide range of environmentally relevant conditions that lanmodulin effectively outcompetes desferrioxamine B, a hydroxamate siderophore previously proposed to be important in trivalent actinide mobility. These results suggest that natural lanthanide-binding proteins such as lanmodulin may play important roles in speciation and mobility of actinides in the environment; it also suggests that protein-based biotechnologies may provide a new frontier in actinide remediation, detection, and separations.
Article
Actinium is an elusive element with untamed properties and represents a peculiar case in the periodic table, as its isotopes are all radioactive, the longest-lived one having only a 22-year half-life, and the availability of actinium isotopes remains very low (microgram level, at best), hindering research on its compounds. Despite being a natural element discovered more than 120 years ago, and despite an increasing interest in using one of its isotopes (²²⁵Ac) for highly efficient cancer therapies, the chemistry of actinium is still largely unknown relative to other elements. Since Ac is the first element of the actinide series, it is accepted that its ion, Ac³⁺, is the most voluminous trivalent cation of the periodic table. However, the structural data available on Ac³⁺ compounds are scarce and have mainly been collected in the 1940-1960′s, when actinide chemistry was still in its infancy, and have not been put in perspective with the advances in the chemistry of other elements, making it difficult to accurately evaluate its actual size and coordination chemistry. Herein, we review progress made on the chemistry of lanthanides and actinides and reevaluate the structural data published on Ac³⁺ since the era of the Manhattan Project. The data are combined across different spectroscopic and characterization methods and presented in the context of periodic trends. When considering crystallographic data, solution chemistry results, and the nuclear properties of actinium isotopes, it appears that some structural parameters ascribed to the Ac³⁺ ion may have been overestimated. This review can guide researchers interested in actinide sciences and those who are pursuing the development of actinium-based radiotherapies, from isotope production to clinical trials.
Article
The impact of calcium on the solubility and redox behavior of the Pu(IV)-EDTA system was investigated using a combination of undersaturation solubility studies and advanced spectroscopic techniques. Batch solubility experiments were conducted in 0.1 M NaCl-NaOH-HCl-EDTA-CaCl2 solutions at constant [EDTA] = 1∙10⁻³ M, 1 ≤ pHm ≤ 11, and 1∙10⁻³ M ≤ [CaCl2] ≤ 2∙10⁻² M. Additional samples targeted brine systems represented by 3.5 M CaCl2 and WIPP simulated brine. Redox conditions were buffered with hydroquinone (pe + pH ≈ 9.5) with selected samples prepared in the absence of any redox buffer. All experiments were performed at T = 22 °C under Ar atmosphere. In-situ X-ray absorption spectroscopy indicated that PuO2(ncr,hyd) was the solubility-controlling phase during the lifetime of all experiments and that aqueous plutonium was present in the +IV oxidation state across all experimental conditions except at pHm ≈ 1, where a small fraction of Pu(III) was also identified. Current thermodynamic models overestimate Pu(IV)-EDTA solubility in the absence of calcium by approximately 1–1.5 log10-units and do not describe the nearly pH-independent, increased solubility observed with increased calcium concentrations. The ternary Pu(IV)-OH-EDTA system without calcium was reevaluated using solubility data obtained in this work and reported in the literature. An updated thermodynamic model including the complexes Pu(OH)(EDTA)⁻, Pu(OH)2(EDTA)²⁻, and Pu(OH)3(EDTA)³⁻ was derived. Solubility data collected in the presence of calcium follows a pH-independent trend (log m(Pu)tot vs. pHm), which can only be explained by assuming the formation of a quaternary complex, tentatively defined as CaPu(OH)4(EDTA)²⁻, in solution. The significant enhancement of plutonium solubility observed in the investigated brine systems supports the formation of a quaternary complex that is not outcompeted by Ca(EDTA)²⁻, even in concentrated CaCl2 solutions. Although the exact stoichiometry of the complex may need to be revisited, this new quaternary complex has a pronounced impact on plutonium predominance diagrams over a broad range of pH, pe, and calcium concentrations that are relevant to nuclear waste disposal.