Mixed Pellets Research Articles

Characterization of ThO2 and (Th,U)O2 pellets consolidated from NSD-sol gel derived nanoparticles

Sinterable ThO2 and mixed 70%ThO2-30%UO2 nanopowders were synthesized and calcined at a low temperature by surfactant assisted sol-gel process using three different nonionic structure directing (NSD) agents: TritonX100, Polysorbate 80 and Polysorbate 20. The produced powder samples, with high surface area and micro and meso pores, were pressed and sintered to form high density ThO2 and (Th,U)O2 pellets. The calculated green and sintered densities of the fabricated pellets, and the results of their microstructural characteristics studies, utilizing SEM images, show that developed synthesizing method yields a satisfactory sinterability of the synthesized ThO2 and ThO2-UO2 nanopowders at low temperature. Also, the final grain size of the pellets reached less than a micrometer in size. The ThO2 and (Th,U)O2 pellets fabricated by synthesized powder using Triton X100 had a higher density and better grain growth. The uranium presence in the mixed oxide pellets led to better sinterability and more normal grain growth.

Characterization of the δ13C signatures of anthropogenic CO2 emissions in the Greater Toronto Area, Canada

In urban environments, carbon dioxide (CO2) is emitted from a variety of anthropogenic and biogenic sources. The isotopic ratio δ13CO2 has been widely used to source apportion CO2 as different sources have distinct isotopic fingerprints; the disadvantage of this technique is that δ13CO2 signatures are often spatially and temporally specific. We present a study characterizing the δ13CO2 signatures of the dominant anthropogenic sources of CO2 in the Greater Toronto Area (GTA). Refined gasoline and diesel fuel were sampled from various stations around the GTA in three separate campaigns (April, July and November 2015) to assess the variability of their δ13CO2 signatures. Mean winter δ13CO2 signatures for refined gasoline were measured to be −27.58 ± 0.52 ‰ and −28.12 ± 0.43 ‰ (uncertainties represent the standard deviation in sample signatures) in April and November respectively while the mean summer signature was measured to be −28.09 ± 0.34 ‰. Diesel fuel samples δ13CO2 signatures from the same campaign periods were measured to be −29.09 ± 0.34 ‰, −29.47 ± 0.29 ‰, and −29.28 ± 0.21 ‰, respectively. We hypothesize that inter-seasonal variability in signatures is likely a result of the use of different parent crude petroleum. We found no significant impacts from octane grade, fuel distributor or municipality the fuel was purchased from on the measured δ13CO2 signatures. Other transportation fuels that were measured include dyed-diesel (δ13CO2 signature = −29.3 ± 0.20 ‰) and jet fuel (δ13CO2 signature = −29.5 ± 0.20 ‰), which were both different than measurements made for the same fuels in other locations globally. To account for emissions from residential and commercial heating and electricity production, a variety of fuels were characterized in this study. The primary heating fuel used in the GTA, natural gas, was measured to have a δ13CH4 signature of −44.2 ± 0.20 ‰. Anthracite coal (a fuel that was used prior to 2014 for electricity) was measured to have a δ13CO2 signature of −23.8 ± 0.20 ‰, which is fairly consistent with coal samples measured elsewhere. With the transition in Ontario from coal to biomass-fueled power generation, softwood, hardwood and mixed wood pellets were sampled from two distributors in the GTA and measured δ13CO2 signatures were −25.0 ± 0.20 ‰, −26.8 ± 0.20 ‰, and −25.8 ± 0.20 ‰, respectively. Using these measured signatures, we performed a sensitivity analysis to quantify the precision required for continuous ambient measurements to separately identify fuel type using δ13CO2 as the sole tracer. The local signatures were also used in a mass balance calculation to quantify the relative contribution of two end-members (with the signatures of −44 ‰ and −28 ‰) to total measured CO2 in the GTA in 2014.

Pelletization of brown coal and rice bran in Indonesia: Characteristics of the mixture pellets including safety during transportation

With the aim of utilizing brown coal as fuel in co-firing power plants, a technique for the pelletization of brown coal and rice bran has been developed. By mixing rice bran with brown coal, the calorific value of brown coal was improved and its safety during transportation increased. The calorific value of the mixed pellets with 50% brown coal and 50% rice bran reached 15MJ/kg, and their durability was sufficiently high at 98%. This technique of pelletization decreases the manufacturing costs because thermal energy for dewatering and drying is not required. In addition, it is beneficial because it uses agricultural residues. Further, if the ratio of brown coal was reduced to below 50%, the mixed pellets did not act as a pyrophoric material (a self-heating substance).

Evaluation of Mechanical Parameters of Pellets

The paper dealt with the evaluation of mechanical properties of the cylinder wheat straw, rapeseed straw and 50/50 % mixed wheat and rapeseed straw pellet samples. The pellets were made by the granulating machine MGL 200 (Kovonovak). The compressive loading curves of dependencies of stress on strain were realised by the test stand Andilog Stentor 1000 (Andilog Technologies, Vitrolles, France). Certain mechanical parameters were determined, namely the initial force (force at 10 % of compress strain), force in maximum of loading curve, strain in maximum of loading curve, initial stress (stress at 10 % of compression strain), stress in maximum of loading curve and modulus of elasticity. Mean value of the initial force was maximal for mixed straw pellet samples 52.49 N. Mean values of the initial force of the wheat straw samples and the rapeseed straw samples were smaller and almost identical 43.58 N and 43.12 N. Mean values of the initial stress of loading curve, of the wheat straw samples reached 1.46 MPa, the rapeseed straw samples reached value 1.40 MPa and the mixed straw samples reached value 1.63 MPa. Mean value of the force in maximum of loading curve was also maximal for mixed straw pellet samples 213.26 N. Mean values of the force in maximum of loading curve of the wheat straw samples reached 178.11 N. The rapeseed straw samples reached value 95.95 N and the mixed straw samples reached value 213.26 N. Mean values of the stress in maximum of loading curve, of the wheat straw samples reached 5.93 MPa, the rapeseed straw samples reached value 3.11 MPa and the mixed straw samples reached value 7.10 MPa Mean values of the modulus of elasticity, of the wheat straw samples reached 18.27 MPa, the rapeseed straw samples reached value 13.08 MPa and the mixed straw samples reached value 14.97 MPa. Significant correlations of the mechanical parameters pellet samples were observed among initial force and initial stress and modulus of elasticity. Significant correlations of force in maximum with stress and strain in the maximum were observed.

Effects of a completely pelleted diet on growth performance in Holstein heifers.

Forage neutral detergent fiber (NDF) content and particle size are important factors that affect rumen function. The aim of the current study was to evaluate the effects on rumen health, NDF digestibility, and animal performance of pelleting a forage-based diet. Eight Holstein heifers (age 336±30d, body weight 346±35kg) were randomly assigned to a repeated crossover design. Animals were housed in tie-stalls and fed for ad libitum intake. The study included 4 periods of 3 wk, the first 2 wk for adaptation to the diet and the last wk for data collection. Diets had the same ingredients but had a different physical form: total mixed ration (TMR) and pellet (diameter=8mm). The physically effective NDF (peNDF) differed between the 2 treatments (39.8 and 11.8% of NDF in the TMR and pellet diets, respectively). During the trial, dry matter intake (DMI), water intake, rumination time, rumen temperature, and pH were evaluated daily. Fecal samples were collected in wk3 of each period to determine total-tract digestibility of the potential digestible (pd)NDF. Average daily gain and feed conversion ratio were calculated at the end of each period. With the pellet diet, DMI, DMI/body weight, and water consumption were higher. We observed no significant difference in average daily gain or feed conversion ratio. Rumination time was lower for the pellet diet than for the TMR diet (241 vs. 507min/d, respectively). Diet had no effect on rumen temperature or rumen pH. The total-tract digestibility of the pdNDF was greater with the TMR diet than with the pellet diet (90.25 vs. 86.82% pdNDF, respectively). The results of the current study suggest that a complete-feed pellet diet was well accepted by the animals, as demonstrated by higher DMI. Rumination time was reduced with the pellet diet, but rumen pH was not different. The pdNDF digestibility was high for both diets, but significantly higher for the TMR diet. Given that animal performance was similar between the 2 diets, although they differed with respect to DMI and fiber digestion, we hypothesize that the 2 diets had different retention times, related to their physical form. A complete-feed pellet diet formulated to provide a sufficient level of NDF from forages could be fed to growing ruminants without apparent negative effects on rumen health and animal productivity, at least for a short period. More research over a longer growing period is needed before recommending this feeding strategy for growing heifers.

A comparative study of biomass pellet and biomass-sludge mixed pellet: Energy input and pellet properties

Pelletization has been widely used for mass and energy densification of biomass. As the demand for pellets increases, the conventional raw materials will be insufficient. In this study, the feasibility of sludge mixed with biomass pellets as a solid fuel was researched. Sludge mixed pellets and pure biomass pellets were investigated to evaluate the energy consumption and pellet properties, including proximate analysis, moisture adsorption, pellet density, Meyer hardness, volume expansion, higher heating value and combustion characteristics. The results showed that sludge mixed pellets had reduced energy input, increased hardness, decreased moisture absorption rate and improved combustion characteristics compared with pure biomass pellets. However, the increased ash content of sludge mixed pellets should be noted. These results indicate that there is a balance between an improvement in fuel quality and an increase in ash content. The sludge mixed pellets could be a suitable solid fuel.

Evaluation of ammonium adsorption in biochar-fixed beds for treatment of anaerobically digested swine slurry: Experimental optimization and modeling

Fixed-bed column experiments were performed to investigate the effect of influent concentration, flow rate, and adsorbent bed depth on ammonium adsorption from anaerobically digested swine slurry using three types of biochar made from corncobs (MCB), hardwood (WB), and mixed sawdust pellets (MSB). WB performed better than the other two biochar types with a maximum sorption capacity of 67–114mg/g due to its superior surface area and larger pore volume. Ammonium adsorption kinetics and dynamics depended on the influent NH4+-N concentration, applied inflow flow rate, and the depth of the fixed bed. Maximum sorption capacities under influent NH4+-N concentration of 500mg/L, were identified to be 114.2mg/g, 108.9mg/g, and 24.7mg/g at inflow rate of 15mL/min for WB, MCB, and MSB, respectively. The data shows that using deeper beds and applying lower flow rates could be a better strategy to increase ammonium adsorption in biochar-fixed beds. Moreover, three kinetic models (Thomas, Adams–Bohart (BDST), and Yoon–Nelson) were applied to the experimental data to predict breakthrough curves and determine characteristic adsorption parameters for process design. The applied models fitted data in the order: Thomas (R2=0.971)>BDST (R2=0.960)>Yoon-Nelson (R2=0.940). It was concluded that ammonium adsorption in biochar-fixed beds could be an effective method for routine cyclic treatment of slurry. However, further effluent polishing is required to meet discharge requirements.

Co-pelletization of sewage sludge and biomass: Thermogravimetric analysis and ash deposits

In this study, the combustion behaviors of sludge–biomass mixed pellets with different sludge ratios in air atmosphere were investigated by thermogravimetric analysis. The pellets consisted of sludge and Chinese fir or rice straw with sludge ratios of 0%, 25%, 50%, 75% and 100%, respectively. The thermogravimetric data were applied for kinetic analysis using the Coats and Redfern (CR) equation. Results showed that there were four main stages such as dehydration, volatile oxidation, char burning and burnout during thermal decomposition of pellets. The reactivities of sludge–biomass pellets were improved by the increment of the mixing ratio of biomass. In addition, the potential slagging behaviors of the resultant ashes were evaluated by X-ray fluorescence (XRF). The suitable sludge to biomass ratio should consider the combustion properties and ash slagging deposition of pellets. It is inappropriate for the production of sludge–straw pellet in the present state due to the high ash slagging potential.

Sensing performance of dielectric sensor in mixed melting polymer pellets for waste plastic separation

Physical value of dielectric properties among relative permittivity, dielectric loss and loss tangent of mixed melting polymer pellets were measured under temperature variance condition and measurement frequency from 0.5MHz to 5MHz in order to develop a real-time non-intrusive measurement technique for high performance waste plastic separation. Various volume fractions of non-polar polyethylene (PE) and polar polyethylene terephthalate (PET) were used as the mixed polymer pellets. As the results, with the volume fractions of PET from 0.05 to 0.22, as the temperature is increased up to melting point temperature and above mold temperature, the relative permittivity is decreased as the temperature is increased. However over melting temperature up to the mold temperature, the relative permittivity is slightly increased as the temperature is increased. On the other hand, the dielectric loss and loss tangent are not affected by the temperature variance, and the dielectric loss and loss tangent are increased as the measurement frequency is increased. As the conclusions, at molding temperature 180°C (453K), the highest sensitivity of dielectric property is the relative permittivity. Meanwhile, the highest linearity relationship between PET volume fraction and predicted relative permittivity is achieved at the measurement frequency of 5MHz. From relative permittivity measurement in these conditions, the performance to distinguish PET volume fraction 0.05 from PE volume fraction 0.95 is achieved in the mixed melting polymer pellets. Therefore, the relative permittivity measurement for waste plastic separation has a possibility to achieve the high purity recycled plastics as compared with conventional methods.

Quantification of rare earth elements using laser-induced breakdown spectroscopy

A study of the optical emission as a function of concentration of laser-ablated yttrium (Y) and of six rare earth elements, europium (Eu), gadolinium (Gd), lanthanum (La), praseodymium (Pr), neodymium (Nd), and samarium (Sm), has been evaluated using the laser-induced breakdown spectroscopy (LIBS) technique. Statistical methodology using multivariate analysis has been used to obtain the sampling errors, coefficient of regression, calibration, and cross-validation of measurements as they relate to the LIBS analysis in graphite-matrix pellets that were doped with elements at several concentrations. Each element (in oxide form) was mixed in the graphite matrix in percentages ranging from 1% to 50% by weight and the LIBS spectra obtained for each composition as well as for pure oxide samples. Finally, a single pellet was mixed with all the elements in equal oxide masses to determine if we can identify the elemental peaks in a mixed pellet. This dataset is relevant for future application to studies of fission product content and distribution in irradiated nuclear fuels. These results demonstrate that LIBS technique is inherently well suited for the future challenge of in situ analysis of nuclear materials. These studies also show that LIBS spectral analysis using statistical methodology can provide quantitative results and suggest an approach in future to the far more challenging multielemental analysis of ~20 primary elements in high-burnup nuclear reactor fuel.

A method for the preparation of sustained release-coated Metoprolol Succinate pellet-containing tablets

The purpose of this study was to develop a method to prepare Metoprolol Succinate (MS) sustained release pellets and compress them into pellet-containing tablets without losing sustained release property. The drug layered pellets were coated with Eudragit NE 30D to obtain a sustained release (SR) property. The mechanical properties and permeability of the coating film were tailored by adjusting the proportion of talc in the coating dispersion and the weight gain of the coating film. Pellets with different MS release rates were tested and then mixed together by different ratios to optimize drug release rate. The mixed pellets were compressed into tablets with cushioning excipients. The results showed that when the ratio of talc and coating material was 1:4, the coating operation could be conducted successfully without pellet conglutination and the mechanical property of the coating film was enhanced to withstand the compress force during tableting. Blending SR-coated pellets of 20% weight gain with SR-coated pellets of 40% weight gain at the ratio of 1:5 could produce a constant and desired drug release rate. The formulation and the procedure developed in the study were suitable to prepare MS pellet-containing tablets with selected SR properties.

An original precipitation route toward the preparation and the sintering of highly reactive uranium cerium dioxide powders

The preparation of dense U1−xCexO2 mixed dioxides pellets was achieved from the initial precipitation of highly reactive precursors. In a first step, a wet chemistry route, based on the mixture of U4+ and Ce4+ in acidic solution with large excess of NH4OH, was set up to reach the precipitation of the cations. The solid phase was then dried under vacuum to avoid aggregation phenomena. Further characterization of the powders by XRD, EDS and TEM revealed the formation of hydrated U1−xCexO2⋅nH2O that probably resulted from the aging of hydroxide compounds. Also, microscopy investigations evidenced the nanosized character of the powder which was associated to high values of specific surface area, typically in the 100–150m2g−1 range.The behavior of U1−xCexO2⋅nH2O versus temperature was investigated in a second part. If the increase of the heat temperature allowed one to observe an improvement of the crystallization state linked with the growth of crystallites, it was also accompanied by a strong decrease of the powders reactivity. On this basis, sintering tests were conducted in reducing atmosphere on the compounds as prepared. Dilatometry experiments indicated a low densification temperature compared to other ways of preparation reported in the literature. Also, the pellets prepared after firing at different temperatures (1350–1550°C) showed that a wide range of microstructures was achievable. Particularly, bulk materials with densities of 90–95% of the calculated value could be prepared with average grain size ranging from around 100nm to more than 5μm. This simple process of elaboration of dense materials from highly reactive hydrated oxide precursor thus appears as a very interesting way to prepare actinide oxides materials.

Effect of particle size and addition of cocoa pod husk on the properties of sawdust and coal pellets

The continuous increase of the world energy demand, the rise of fossil fuels costs, and the strong environmental policies around the globe are some of the reasons for the wood pellets industry increase. However, there are some other available biomass feedstocks capable of being densified for energy production. Among the various options, the use of mixed biomass pellets is becoming remark-able due to the wide variety of species, although more research is needed in order to enhance the mechanical properties of these pellets. This study aims to identify the effect of particle size on the mechanical properties of sawdust and coal pellets when cocoa pod husks are used as an additive. Cocoa pod husks have a similar composition to sawdust and less sulfur and nitrogen than coal. Thus, the use of this additive might decrease the environmental impact during coal pellets combustion. Results show an attractive potential of cocoa pod husks grinds for pellet production, an increase of the durability of coal pellets mixed with this raw material, and similar performance between cocoa pod husks and sawdust pellets. The compression ratio, the compressive and impact resistance varied linearly with the addition of cocoa pod husks.

Combined calcium looping and chemical looping combustion cycles with CaO–CuO pellets in a fixed bed reactor

The feasibility of using integrated CaO/CuO-based pellets in combined calcium and chemical looping cycles in a fixed bed was investigated with emphasis on CO2 capture performance. Three types of pellets were tested, namely; integrated core-in-shell CaO/CuO-based pellets; integrated homogeneous CaO/CuO-based pellets; and mixed CaO-based pellets and CuO-based pellets. Redox cycles consisted of oxidation/carbonation at 650°C in 15% CO2; 4% O2, and N2 balance, and reduction/calcination at 850°C in a CO/H2 mixture. The results showed that mixed pellets exhibited the highest CO2 uptakes of 0.11g CO2/g bed in the first cycle and 0.07g/g after 11 cycles (corresponding to CaO conversions of 32.1% and 19%, respectively). This enhanced performance was attributed to the significantly higher pore volume and surface area in the calcined CaO-based pellets, which were superior to those of integrated CaO/CuO-based pellets. The reduction of CuO to Cu2O was found to be partially irreversible, with ∼45% of copper oxide in the pellets in the form of Cu2O despite the excess O2 in the oxidizing environment. It was also noted that cycled core-in-shell pellets were the most susceptible to fragmentation, indicating the low mechanical strength of these pellets. It was concluded that combined calcium and chemical looping cycles in a fixed bed system is a feasible process providing suitable pellets are used. Incorporating CuO in CaO-based pellets reduces the porosity of the pellets, thus compromises CO2 uptake. Among the three groups of pellets, mixed pellets are the most promising for CaL–CLC processes due to their better performance, easier manufacturing, and better quality control than integrated pellets.

聚乙烯塑料–煤粉与铁精矿混合球团性能研究

采用煤粉混合聚乙烯废塑料与铁精矿制备含碳球团，对所得混合含碳球团特性进行了试验研究。结果表明，在一定的物料粒度、水分含量、膨润土加入量条件下，配加聚乙烯塑料的混合含碳球团的冷态性能增强，塑料加入量越多，球团冷态强度越好，以干球强度提高更为明显。焙烧还原后，1:1的聚乙烯煤粉混合还原剂球团(或1:2)比煤粉球团强度增强，且对还原后的球团进行矿相分析发现，配加聚乙烯塑料能够改善自还原过程的热质条件，促进还原反应的进行，且还原区域集中在聚乙烯塑料颗粒周围。 Experimental researches on characteristics of the mixed pellets containing carbon which are made from pulverized coal mixed with polyethylene plastic and iron ore were carried out. The results show that under certain material particle size, moisture content percent and certain amount of bentonite conditions, cold state performance of pellets containing carbon mixed with addition of polyethylene plastic is reinforced, meaning that the more amount of plastic added in the mixed pellets, the better the cold strength to increase the strength of the dry bulb apparently. After the roasting reduction, strength of pulverized reductant polyethylene pellets with mixed rates of 1:1 (or 1:2) is better than that of pulverized coal pellet, and mineralogical analysis on polyethylene pellets shows that the addition of polyethylene plastic can improve the conditions of the reducing process heat and promote the reducing reaction, and the reducing area concentrates around the polyethylene plastic particles.

Miscanthus Giganteus Biomass for Sustainable Energy in Small Scale Heating Systems

Abstract Miscanthus giganteus biomass has a very good quality for combustion (similar as a light coal or wood, up to 19.6 MJ/kg dry matter) and has positive ecological impact for marginal land that makes this crop suitable as bioenergy resources for small scale heating systems. The most important technology to make easily available Miscanthus giganteus feedstock on the market is biomass briquetting or pelleting. This study was conducted to determine the capability of mixing Miscanthus giganteus biomass with other vegetable biomass (straw, wood sawdust, or other energetic plants) to obtain briquettes and pellets. Different characteristics were studied as: percentage of variable biomass mixed with Miscanthus (30%, 50%, 70%), humidity variation (wt = 9 – 13%) and quality of final product. The efficient densification process of various biomass plants depends on these properties and on used technologies. Combustion properties of mixed biomass briquettes and pellets (ash content and composition, calorific values, emissions characteristics) have been determined as well. Results are showing that slag problems may be disturbing the combustion process and that the temperature is a critical factor (best results in combustion efficiency are above 1000 °C). In order to ensure the productivity for making available constantly processed products (briquettes, pellets), different heating installations need adjustments to increase the efficiency for mixed biomass combustion.

Total mixed ration pellets for light fattening lambs: effects on animal health

Fifty male Merino lambs (6 to 8 weeks, 14.1 kg; n=10 per group) were used to study the effect of feeding system: barley straw in long form and concentrate pellets in separate troughs (Control), ad libitum alfalfa supplemented with concentrate in separate troughs (Alfalfa) or including various levels of ground barley straw in concentrate pellets (B05, B15 and B25 for 50, 150 and 250 g barley straw/kg), on rumen characteristics, acid-base status, blood cell counts and lymphocyte stimulation. Alfalfa lambs had the heaviest digestive tract contents, highest rumen pH values, lowest volatile fatty acid concentration, highest papillae counts and best mucosa colour and the greatest blood pCO2 values, lowest sodium and chloride and highest potassium concentrations (P<0.05). Including ground barley straw in the concentrate pellet or providing straw in long form separately from the concentrate reduces rumen pH and darkens ruminal mucosa as compared with alfalfa-fed lambs, thus affecting acid-base status.

Fuel Properties of Woody Pellets in Domestic Markets of Korea

This study investigated physical properties and combustion gas characteristics for 8 types of wood pellets (4 domestic and 4 imported products) distributed in the domestic market. Results showed that most pellet types were first-grade pellets in the wood pellet quality standards in Korea with the exception of 3 pellet types from K company (second-grade in mechanical durability), G company (off-grade in nitrogen content) and P company (second-grade in ash percentage). Mixed pellets which contained more lignin and sap content were higher in mechanical durability (%) than that of white pellets. From the combustion gas analysis results, NOx emitted from all pellets combustion was at acceptable levels for national emission standard of the Clean Air Conservation Act except for pellets from G company. In addition, CO levels from all types of wood pellets were acceptable except for pellets from D company and domestic pellets were higher CO levels than imported pellets. These results indicate the higher CO levels in domestic pellets due to the usage of forest thinning materials including logging debris which usually had the high content of bark.

Stable carbon fractionation in size-segregated aerosol particles produced by controlled biomass burning

Six different biomass fuel types (wood pellets, sunflower stalk pellets, straw pellets, buckwheat shells, mixed biomass waste pellets, and grain screenings) and wastewater sludge pellets were burned under controlled conditions to determine the effect of the biomass type on the emitted particulate matter mass and stable carbon isotope composition of bulk and size-segregated particles. Aerosol particles were sampled using the total suspended particle (TSP) sampler and a micro-orifice uniform deposit impactor (MOUDI). The results demonstrated that particle emissions were dominated by the submicron particles (size <1µm) in all biomass types. However, significant differences in emissions of submicron particles and their dominant sizes were found between different biomass fuels. The isotopic fractionation between aerosol particles and original biomass material varied from −0.94±0.23‰ to 1.12±0.16‰. The largest negative fractionation −0.94±0.23‰ was obtained for the wood pellet fuel type while the largest positive isotopic fractionation (1.12±0.16‰) was observed during the grain screenings combustion. The carbon isotope composition of MOUDI samples compared very well with the isotope composition of TSP samples indicating consistency of the results. The measurements of the stable carbon isotope ratio in size-segregated aerosol particles suggested that combustion processes could strongly affect isotopic fractionation in aerosol particles of different sizes thereby potentially affecting an interpretation of ambient atmospheric observations.

Impact of the cation distribution homogeneity on the americium oxidation state in the U0.54Pu0.45Am0.01O2−x mixed oxide

The impact of the cation distribution homogeneity of the U0.54Pu0.45Am0.01O2−x mixed oxide on the americium oxidation state was studied by coupling X-ray diffraction (XRD), electron probe micro analysis (EPMA) and X-ray absorption spectroscopy (XAS). Oxygen-hypostoichiometric Am-bearing uranium–plutonium mixed oxide pellets were fabricated by two different co-milling based processes in order to obtain different cation distribution homogeneities. The americium was generated from β− decay of 241Pu. The XRD analysis of the obtained compounds did not reveal any structural difference between the samples. EPMA, however, revealed a high homogeneity in the cation distribution for one sample, and substantial heterogeneity of the U–Pu (so Am) distribution for the other. The difference in cation distribution was linked to a difference in Am chemistry as investigated by XAS, with Am being present at mixed +III/+IV oxidation state in the heterogeneous compound, whereas only Am(IV) was observed in the homogeneous compound. Previously reported discrepancies on Am oxidation states can hence be explained by cation distribution homogeneity effects.