The Saltstone Disposal Facility on the Savannah River Site in South Carolina disposes of Low-Level Waste in a reducing-grout waste form. Reducing grout is presently being evaluated as a subsurface disposal waste form at several other locations in the United States, as well as in Europe and Asia. The objective of this study was to collect core samples directly from the Saltstone Disposal Facility and measure desorption distribution coefficients (Kd; radionuclide concentration ratio of saltstone:liquid; (Bq/kg)/Bq/L)) and desorption apparent solubility values (ksp; radionuclide aqueous concentration (moles/L)). An important attribute of this study was that these tests were conducted with actual aged, grout waste form materials, not small-volume simulants prepared in a laboratory. The reducing grout is comprised of blast furnace slag, Class F fly ash, ordinary portland cement, and a radioactive salt waste solution generated during nuclear processing. The grout sample used in this study underwent hydrolyzation in the disposal facility for 30 months prior to measuring radionuclide leaching. Leaching experiments were conducted either in an inert (no oxygen) atmosphere to simulate conditions within the saltstone monolith prior to aging (becoming oxidized) or they were exposed to atmosphere conditions to simulate conditions of an aged saltstone. Importantly, these experiments were designed not to be diffusion limited, that is, the saltstone was ground finely and the suspensions were under constant agitation during the equilibration period. Under oxidized conditions, measured Tc Kd values were 10 mL/g, which was appreciably greater than the historical best-estimate value of 0.8 mL/g. This difference is likely the result of a fraction of the Tc remaining in the less soluble Tc(IV) form, even after extensive oxidation during the experiment. Under oxidized and reducing conditions, the measured Ba and Sr (both divalent alkaline earth metals) Kd value were more than an order of magnitude greater than historical best-estimate values of 100 mL/g. The unexpectedly high Ba and Sr Kd values were attributed to these radionuclides having sufficient time to age (form strong bonds) in the sulfur-rich saltstone sample. Apparent ksp values under reducing conditions were 10-9 mol/L Tc and 10-13 mol/L Pu, consistent with values measured with surrogate materials. Measured apparent Ba, Sr, and Th ksp values were significantly greater than historical best-estimates. The implications of the generally greater Kd values and lower ksp values in these measurements is that these cementitious waste forms have greater radionuclide retention than was previously estimated based on laboratory studies using surrogate materials. This work represents the first leaching study performed with an actual aged, reducing-grout sample and as such provides an important comparison to studies conducted with surrogate materials, and provides high pedigree data for other programs around the world evaluating reducing grouts as a wasteform for subsurface nuclear waste disposal.

The Fukushima Daiichi Nuclear Power Plant accident released considerable radionuclides into the environment. Radioactive particles, composed mainly of SiO2, emerged as distinctive features, revealing insights into the accident\'s dynamics. While studies extensively focused on high-volatile radionuclides like Cs, investigations into low-volatile nuclides such as 90Sr and Pu remain limited. Understanding their abundance in radioactive particles is crucial for deciphering the accident\'s details, including reactor temperatures and injection processes. Here, we aimed to determine 90Sr and Pu amounts in radioactive particles and provide essential data for understanding the formation processes and conditions within the reactor during the accident. We employed radiochemical analysis on nine radioactive particles and determined the amounts of 90Sr and Pu in these particles. 90Sr and Pu quantification in radioactive particles showed that the 90Sr/137Cs radioactivity ratio (corrected to March 11, 2011) aligned with core temperature expectations. However, the 239+240Pu/137Cs activity ratio indicated nonvolatile Pu introduction, possibly through fuel fragments. Analyzing 90Sr and Pu enhances our understanding of the Fukushima Daiichi accident. Deviations in 239+240Pu/137Cs activity ratios underscore nonvolatile processes, emphasizing the accident\'s complexity. Future research should expand this data set for a more comprehensive understanding of the accident\'s nuances.

Glaciers are recognized as repositories for atmospheric pollutants, however, due to climate change and enhanced melting rates, they are rapidly transitioning from being repositories to secondary sources of such apollutants. Artificial radionuclides are one of the pollutants found on glaciers that efficiently accumulate onto glacier surfaces within cryoconite deposits; a dark, often biogenic sediment. This work provides information about the accumulation, distribution and sources of plutonium (Pu) isotopes in cryoconite samples from glaciers worldwide. Plutonium is an artificial radionuclide spread into the environment in the last decades as a consequence of nuclear test explosions, accidents and nuclear fuel re-processing. Samples collected from 49 glaciers across nine regions of Earth are considered. Activity concentrations of plutonium in cryoconite are orders of magnitude higher than in other environmental matrices typically used for environmental monitoring (e.g. lichens, mosses, soils and sediments), particularly in the Northern Hemisphere. Isotopic ratios indicate that plutonium contamination of cryoconite is dominated by the global signal of stratospheric fallout related to atmospheric nuclear tests. However, specific glaciers in Svalbard reveal a signature compatible with a contribution from the re-entry of the SNAP-9A satellite in 1964, which was equipped with a 238Pu radioisotope thermoelectric generator. Similarly, an excess of 238Pu is observed in cryoconite from the Exploradores Glacier (Chile). This could be associated with the November 1996 crash of the automatic Interplanetary Station \"Mars \'96\" which was carrying a 238Pu thermoelectric generator. This is the first time ever that an isotopic evidence for this event is reported. These findings highlight the role that cryoconite can play in reconstructing the radioactive contamination history of different glaciated regions of the Earth.

Climate change poses an immediate threat to tropical soils with changes in rainfall patterns resulting in accelerated land degradation processes. To ensure the future sustainability of arable land, it is essential to improve our understanding of the factors that influence soil erosion processes. This work aimed to evaluate patterns of soil erosion using the activity of plutonium isotopes (Pu) at sites with different land use and clearance scale in the Winam Gulf catchment of Lake Victoria in Kenya. Erosion rates were modelled at potential erosive sites using the MODERN model to understand small-scale erosion processes and the effect of different management practices. The lowest soil redistribution rates for arable land were 0.10 Mg ha-1 yr-1 showing overall deposition, resulting from community-led bottom-up mitigation practices. In contrast erosion rates of 8.93 Mg ha-1 yr-1 were found in areas where steep terraces have been formed. This demonstrates the significance of community-led participation in effectively managing land degradation processes. Another key factor identified in the acceleration of soil erosion rates was the clearance of land with an increased rate of erosion over three years reported (0.45 to 0.82 Mg ha-1 yr-1) underlining the importance vegetation cover plays in limiting soil erosion processes. This novel application of fallout plutonium as a tracer, highlights its potential to inform the understanding of how soil erosion processes respond to land management, which will better support implementation of effective mitigation strategies.

The ability to distinguish multiple forms of plutonium from one another, such as oxide and metal, is paramount in areas of nuclear nonproliferation and international safeguards. In its metal form, plutonium can be readily used in a nuclear weapon, while oxide forms are associated with nuclear reactor fuel. Oxide-based plutonium forms emit neutrons with an energy spectrum that is significantly different from the fission neutrons that are emitted from plutonium metal. Organic scintillation detectors output pulses that are proportional to the neutron energy deposited, and therefore present a means of distinguishing these plutonium forms based on their energy spectra. In this work, metal and oxide forms of plutonium were measured using a handheld detection system based on an organic glass scintillator. Monte Carlo modeling of these experiments was performed to provide insight into the origin of the features in the observed light output spectra. Through analysis of multiple regions of these spectra, in a matter of minutes we were able to unambiguously discriminate oxide and metal plutonium forms from one another and from a plutonium-beryllium neutron source, which was considered for comparison because these sources are commonly used in industrial applications. The ability to discriminate weapons-usable material from nuclear reactor fuel has applications in nuclear treaty verification and safeguards.

Sorption of Pu(VI) onto synthesized goethite under oxidizing and normal conditions was investigated, which revealed its pH dependence on different solid/liquid ratios. Pu speciation upon sorption on the solid phase was characterized via extended X-ray absorption fine structure (EXAFS) spectroscopy, while that in solution was assessed using ultraviolet-visible (UV-Vis) spectroscopy and liquid-liquid extraction. The obtained results demonstrate differences in plutonium behavior in the studied systems. Pu(VI) remains hexavalent on the goethite surface and in solution under oxidizing conditions. While Pu(IV) is stabilized on the mineral and Pu(V) is found in solution under normal conditions. This study provides the thermodynamic descriptions of these reactions.

Radiation imaging is extensively applied in nuclear industry for various purposes including fuel characterization. Accurate quantitative evaluation of these radiographic images is difficult by the existing manual process and therefore image analytical methods have been attempted. The method of wavelet transform analysis has been applied on Gamma autoradiography (GAR) images of experimental (U, Pu)O2 mixed oxide (MOX) fuel pins with the objective to investigate the effectiveness of the method for fuel homogeneity characterization. The method was found effective to carry out quantified estimations of size and relative plutonium concentration of the heterogeneous portions in the fuel. The results were validated with theoretically simulated results as practical standards and calibrations are not possible in these samples. The results of wavelet transformation analysis were found to be more accurate with reference to the theoretically simulated values in comparison with conventional pixel analysis applied on the original GAR images.

UNASSIGNED: Plutonium and iron share a common metabolism in terms of their transportation and accumulation in the human body. This study examined their concentrations in livers with different states of health, and the effects of fatty degeneration and cirrhosis on their accumulation in the liver.
UNASSIGNED: We determined the concentrations of plutonium and iron in autopsy liver samples from 1976-1979. Using statistical analysis, we investigated the relationships between the different variables.
UNASSIGNED: The burdens of 239,240Pu and Fe correlated positively (Rs = 0.411) in the healthy livers, but not in the livers that had pathological findings. In contrast to the Fe content, the 239,240Pu content in the fatty degenerated or cirrhotic livers was significantly lower than that in normal livers. This difference may suggest that plutonium and iron do not accumulate or are not excreted in the same way in fatty degenerated and cirrhotic livers. The reaction mechanisms for the binding and excretion of plutonium, particularly in a fatty degenerated liver, are not yet fully known.

When environmental impact and risks associated with radioactive contamination of ecosystems are assessed, the source term and deposition must be linked to ecosystem transfer, biological uptake and effects in exposed organisms. Thus, a well-defined source term is the starting point for transport, dose, impact and risk models. After the Chornobyl accident, 3-4 tons of spent nuclear fuel were released and radioactive particles were important ingrediencies of the actual source term. As Chornobyl particles were observed in many European countries, some scientists suggested that radioactive particles were \"a peculiarity of the Chornobyl accident.\" In contrast, research over the years has shown that a major fraction of refractory elements such as uranium (U) and plutonium (Pu) released to the environment has been released as particles following a series of past events such as nuclear weapons tests, non-criticality accidents involving nuclear weapons, military use of depleted uranium ammunition, and nuclear reactor accidents. Radioactive particles and colloids have also been observed in discharges from nuclear installations to rivers or to regional seas and are associated with nuclear waste dumped at sea. Furthermore, radioactive particles have been identified at uranium mining and tailing sites as well as at other NORM sites such as phosphate or oil and gas industrial facilities. Research has also demonstrated that particle characteristics such as elemental composition depend on the emitting source, while characteristics such as size distribution, structure, and oxidation state influencing ecosystem transfer will also depend on the release scenarios. Thus, access to advanced particle characteristic techniques is essential within radioecology. After deposition, localized heterogeneities such as particles will be unevenly distributed in the environment. Thus, inventories can be underestimated, and impact and risk assessments of particle contaminated areas may suffer from unacceptable large uncertainties if radioactive particles are ignored. The present paper will focus on key sources contributing to the release of radioactive particles to the environments, as well as linking particle characteristics to ecosystem behavior and potential biological effects.

Plutonium, as well as fission products such as 137Cs, had been released into the earth environment in 1945 after the first atmospheric nuclear explosion of plutonium bomb in the desert of New Mexico (USA, July 16) and later over Nagasaki (August 9), followed then by many other explosions. Thus, plutonium cycling in the atmosphere and ocean has become a major public concern as a result of the radiological and chemical toxicity of plutonium. However, plutonium isotopes and 137Cs are important transient tracers of biogeochemical and physical processes in the environment, respectively. In this review, we show that both physical and chemical approaches are needed to comprehensively understand the behaviors of plutonium in the atmosphere and ocean. In the atmosphere, plutonium and 137Cs attach with aerosols; thus, plutonium moves according to physical and chemical processes in connection with aerosols; however, since plutonium is a chemically reactive element, its behavior in an aqueous environment is more complicated, because biogeochemical regulatory factors, in addition to geophysical regulatory factors, must be considered. Meanwhile, 137Cs is chemically inert in aqueous environments. Therefore, the biogeochemical characteristics of plutonium can be elucidated through a comparison with those of 137Cs, which show conservative properties and moves according to physical processes. Finally, we suggest that monitoring of both plutonium and 137Cs can help elucidate geophysical and biogeochemical changes from climate changes.