Surrogate Elements Research Articles

Study on Separation of Rhenium, a Surrogate Element of Fissiogenic Technetium, from Aqueous Matrices Using Ion-Selective Extraction Chromatographic Resins

Long-lived fissiogenic technetium, 99Tc (half-life, 2.11 × 105 yrs), is a byproduct of the 235U and 239Pu fission in nuclear reactors and is a major component in nuclear waste. Hence, the monitoring of 99Tc activity in the environmental samples is essential. Techniques used to measure 99Tc in environmental samples include radiometric and non-radiometric approaches. Inductively coupled plasma mass spectrometry (ICP-MS) has some advantages among the methods due to its high sample throughput, better selectivity, and commercial availability. Rhenium (Re) is often used as the non-isotopic tracer during 99Tc measurement by ICP-MS. From this perspective, studying the separation behavior of Re from the aqueous matrix can provide helpful insight regarding the ecological monitoring of 99Tc. In the current work, three extraction chromatographic resins (ECRs), MetaSEP AnaLig Tc-01, MetaSEP AnaLig Tc-02, and Eichrom TRU, have been used to separate Re from the aqueous matrix. Operating variables, such as solution pH, choice of eluent and eluent concentration, matrix cation effect, and retention capacity, have been studied to optimize the separation protocol. The extraction and recovery behavior of Re was used to interpret the selectivity behavior of the ECRs. The Re separation factor at optimized operating conditions comparing with Mo and Ru (interfering elements during the measurement by ICP-MS) for Meta SEP AnaLig Tc-01, Meta SEP AnaLig Tc-02, and Eichrom TRU resin, respectively, are SFRe/Mo~32, 16.51, and ∞ (metal not retained at all), while SFRe/Ru~∞, 3.25, 5437. In terms of selectivity and retention capacity, MetaSEP AnaLig Tc-01 is the better choice for selective separation of Re, and, assumably so, also Tc, from the aqueous matrices.

Extraction Behavior of Some Elements from Leaching Solution of Simulated Nuclear Fuel

The crush-leach process was investigated as a method to treat GEN IV simulated ceramic-coated reactor fuel. Simulated ceramic-coated fuel was prepared using fine carbon as a coating and surrogate elements for fuel, the method retained the bulk of the carbon components in elemental form, which is favorable for achieving waste reduction goals. Simulated ceramic-coated fuel was crushed and nitric acid was added to the fines as slurry that led to rapid and effective leaching of the heavy metal. The leaching process of simulated crushed ceramic-coated fuel and extraction behavior of the separated leaching solution was tested at the laboratory scale. Results showed that carbon used in the preparation of stimulated fuel was difficult to be separated by filtered, indicating the need to carefully control particle size and/or use alternative solid-liquid separation methods. Foams or emulsions was not observed during the solvent extraction step, which indicated that measurement of the distribution ratios for actinides elements were slightly larger than predicted by previous models. This increase may be due to small concentrations of organics; however the experimental results are not conclusive. Although the results do not strongly indicate effects by a contaminating organic agent, the organic species may exist in small concentrations. Such an organic species could affect the extraction behavior of the solvent if it accumulates over time.

Actinide Drawdown From LiCl-KCl Eutectic Salt via Galvanic/chemical Reactions Using Rare Earth Metals

This study proposes a method of separating uranium (U) and minor actinides from rare earth (RE) elements in the LiCl-KCl salt system. Several RE metals were used to reduce UCl3 and MgCl2 from the eutectic LiCl-KCl salt systems. Five experiments were performed on drawdown U and plutonium (Pu) surrogate elements from RECl3-enriched LiCl-KCl salt systems at 773 K. Via the introduction of RE metals into the salt system, it was observed that the UCl3 concentration can be lowered below 100 ppm. In addition, UCl3 was reduced into a powdery form that easily settled at the bottom and was successfully collected by a salt distillation operation. When the RE metals come into contact with a metallic structure, a galvanic interaction occurs dominantly, seemingly accelerating the U recovery reaction. These results elucidate the development of an effective and simple process that selectively removes actinides from electrorefining salt, thus contributing to the minimization of the influx of actinides into the nuclear fuel waste stream.

Characterisation and disposability assessment of multi-waste stream in-container vitrified products for higher activity radioactive waste

Materials from GeoMelt® In-Container Vitrification (ICV)™ of simulant UK nuclear wastes were characterised to understand the partitioning of elements, including inactive surrogates for radionuclide species of interest, within the heterogeneous products. Aqueous durability analysis was performed to assess the potential disposability of the resulting wasteforms. The vitrification trial aimed to immobilise a variety of simulant legacy waste streams representative of decommissioning operations in the UK, including plutonium contaminated material, Magnox sludges and ion-exchange materials, which were vitrified upon the addition of glass forming additives. Two trials with different wastes were characterised, with the resultant vitreous wasteforms comprising olivine and pyroxene crystalline minerals within glassy matrices. Plutonium surrogate elements were immobilised within the glassy fraction rather than partitioning into crystalline phases. All vitrified products exhibited comparable or improved durability to existing UK high level waste vitrified nuclear wasteforms over a 28 day period.

Real-time Monitoring of Biomarkers in Serum for Early Diagnosis of Target Disease

Real-time monitoring of biomarkers has important applications in immediately determining, for example, disease progress or therapeutic effects to clinical decisions in the fields of diagnosis, prognosis and therapy. However, technologies developed in this area require frequent sample drawings, unattended analysis in situ, secure online monitoring, and, above all, patient’s safety, so from this point of view are still in their infancy. Current research activity in the area has been restricted to the extent of monitoring physical signals while glucose is the only biomarker generally monitored in real-time. To realize the future of unattended analysis, our research group has investigated various immuno-analytical concepts that enable, in particular, repetitive measurements of target biomarkers in a continuous or semi-continuous manner. The key actors in these achievements were monoclonal antibodies with unique characteristics, raised in our group, that potentially allow for real-time monitoring of target disease markers from tiny ionic molecules to complex proteins. Furthermore, we have investigated surrogate elements (e.g. receptors and cytokines) that translate cellular response to measurable signals, enabling us to determine the functional properties of analytes. In this review, continuous and semi-continuous monitoring techniques of different markers for acute myocardial infarction are presented.

Priorities for conservation of endemic trees and shrubs of Iran: Important Plant Areas (IPAs) and Alliance for Zero Extinction (AZE) in SW Asia

Owing to narrow geographical distribution, endemic species indicates higher vulnerability than other taxa, so they have been used as surrogate elements to identify the priorities. Little attention has been paid to distribution patterns, hot spots, and conservative zones of endemic trees and shrubs in scale of Iran. The main purpose of this study was to identify and introduce the Important Plant Areas (IPAs) as well as Alliance for Zero Extinction (AZEs) of endemic trees and shrubs in Iran. The total number of endemic trees and shrubs in the studied area included 75 species belonging to 32 genera of 22 plant families. Chorological elements mainly (65:86.6%) belong to the Irano-Turanian region. The geomorphological barriers have confined plant immigrations in the north-south as well as east-west slopes, appearing as a center of plant speciation in Iran. Our results indicate a significant percentage (36.2%) of these endemics classified in the threatened categories. Central as well as southern Zagros, Central Alborz and with more limited range N. Zagros, Kopet Dagh as well SW Iran are classified as AZE under both Criteria of AZE.

Large-scale simulation of mantle convection based on a new matrix-free approach

In this paper, we report on a two-scale approach for efficient matrix-free finite element simulations. It is an extended version of our previous conference publication [1]. The proposed method is based on surrogate element matrices constructed by low order polynomial approximations. It is applied to a Stokes-type PDE system with variable viscosity as is a key component in mantle convection models. We set the ground for a rigorous performance analysis inspired by the concept of parallel textbook multigrid efficiency and study the weak scaling behavior on SuperMUC, a peta-scale supercomputer system. For a complex geodynamical model, we achieve, on up to 47 250 compute cores, a parallel efficiency of 93% for application of the discrete operator and 83% for a complete Uzawa V-cycle including the coarse grid solve. Our largest simulation uses a trillion (O(1012)) degrees of freedom for a global mesh resolution of 1.5 km. Applicability of our new approach for geodynamical problems is demonstrated by investigating dynamic topography for classical benchmark settings as well as for high-resolution models with lateral viscosity variations.

A data-driven dynamics simulation framework for railway vehicles

ABSTRACTThe finite element (FE) method is essential for simulating vehicle dynamics with fine details, especially for train crash simulations. However, factors such as the complexity of meshes and the distortion involved in a large deformation would undermine its calculation efficiency. An alternative method, the multi-body (MB) dynamics simulation provides satisfying time efficiency but limited accuracy when highly nonlinear dynamic process is involved. To maintain the advantages of both methods, this paper proposes a data-driven simulation framework for dynamics simulation of railway vehicles. This framework uses machine learning techniques to extract nonlinear features from training data generated by FE simulations so that specific mesh structures can be formulated by a surrogate element (or surrogate elements) to replace the original mechanical elements, and the dynamics simulation can be implemented by co-simulation with the surrogate element(s) embedded into a MB model. This framework consists of a series of techniques including data collection, feature extraction, training data sampling, surrogate element building, and model evaluation and selection. To verify the feasibility of this framework, we present two case studies, a vertical dynamics simulation and a longitudinal dynamics simulation, based on co-simulation with MATLAB/Simulink and Simpack, and a further comparison with a popular data-driven model (the Kriging model) is provided. The simulation result shows that using the legendre polynomial regression model in building surrogate elements can largely cut down the simulation time without sacrifice in accuracy.

Abundances in Galactic bulge planetary nebulae from optical, ultraviolet and infrared observations

Iron suffers from high levels of depletion in the highly ionized environments of planetary nebulae, making the direct determination of undepleted elemental iron abundances difficult. Zinc, which does not suffer from the same depletion effects as iron, may be used as a surrogate element to measure iron abundances as there is an approximately constant zinc-to-iron ratio across a wide range of metallicities. In this paper, we report zinc abundances of six Galactic Bulge planetary nebulae determined from new observations taken with ISAAC on the Very Large Telescope, Chile, prior to the instrument's decommissioning as well as a further three based upon literature observations. UVES data of the sample planetary nebulae are presented and have been used to derive abundances, temperatures and densities of a variety of elements and ions. The abundances derived from the UVES data agree well with results from the literature. [Zn/H], determined from the ISAAC observations, is found to be generally sub-solar and [O/Zn] is found to be either consistent or enriched with respect to Solar.

Thermal expansion of the nuclear fuel-sodium reaction product Na3(U0.84(2),Na0.16(2))O4 - Structural mechanism and comparison with related sodium-metal ternary oxides

Na3.16(2)UV,VI0.84(2)O4 is obtained from the reaction of sodium with uranium dioxide under oxygen potential conditions typical of a sodium-cooled fast nuclear reactor. In the event of a breach of the steel cladding, it would be the dominant reaction product forming at the rim of the mixed (U,Pu)O2 fuel pellets. High-temperature X-ray diffraction measurements show that a distortion of the uranium environment in Na3.16(2)UV,VI0.84(2)O4 results in a strongly anisotropic thermal expansion. A comparison with several related sodium metallates Nan-2Mn+On-1 - including Na3SbO4 and Na3TaO4, whose crystal structures are reported for the first time - has allowed us to assess the role played in the lattice expansion by the Mn+ cation radius and the Na/M ratio. On this basis, the thermomechanical behavior of the title compound is discussed, along with those of several related double oxides of sodium and actinide elements, surrogate elements, or fission products.

Development of novel synthetic muscle tissues for sports impact surrogates

Impact injuries are commonplace in sport and often lead to performance detriment and debilitation. Personal Protective Equipment (PPE) is prescribed as a mandatory requirement in most sports where these impacts are likely to occur, though the methods of governance and evaluation criteria often do not accurately represent sports specific injury scenarios. One of the key shortcomings of such safety test standards is the human surrogate to which the PPE is affixed; this typically embodies unrepresentative geometries, masses, stiffness and levels of constraint when compared to humans.A key aspect of any human surrogate element is the simulant material used. Most previous sports specific surrogates tend to use off-the-shelf silicone blends to represent all the soft tissue structures within the human limb segment or organ; this approach potentially neglects important human response phenomena caused by the different tissue structures.This study presents an investigation into the use of bespoke additive cure Polydimethysiloxane (PDMS) silicone blends to match the reported mechanical properties of human relaxed and contracted skeletal muscle tissues. The silicone simulants have been tested in uniaxial compression through a range of strain rates and fit with a range of constitutive hyperelastic models (Mooney Rivlin, Ogden and Neo Hookean) and a viscoelastic Prony series.

Zinc abundances of planetary nebulae

Zinc is a useful surrogate element for measuring Fe/H as, unlike iron, it is not depleted in the gas phase media. Zn/H and O/Zn ratios have been derived using the [Zn IV] emission line at 3.625um for a sample of nine Galactic planetary nebulae, seven of which are based upon new observations using the VLT. Based on photoionization models, O/O++ is the most reliable ionisation correction factor for zinc that can readily be determined from optical emission lines, with an estimated accuracy of 10% or better for all targets in our sample. The majority of the sample is found to be sub-solar in [Zn/H]. [O/Zn] in half of the sample is found to be consistent with Solar within uncertainties, whereas the remaining half are enhanced in [O/Zn]. [Zn/H] and [O/Zn] as functions of Galactocentric distance have been investigated and there is little evidence to support a trend in either case.

Corrosion Study of SIMFUEL in Aerated Carbonate Solution Containing Calcium and Silicate

ABSTRACTThe corrosion behavior of simulated spent nuclear fuel (SIMFUEL) was investigated using electrochemical impedance spectroscopy and solution chemistry analyses. The SIMFUEL was exposed to aerated solutions of NaCl+NaHCO3 with and without calcium (Ca) and silicate. Two SIMFUEL compositions were studied, representing spent nuclear fuel (SNF) corresponding to 3 or 6 at % burnup in terms of fission product equivalents of surrogate elements. For all tested cases, the polarization resistance increased with increased immersion time, indicating possible blocking effects due to accumulation of corrosion products on the SIMFUEL surface. The potential-pH diagram suggests formation of schoepite that may cause the increase in the polarization resistance. The addition of Ca and silicate produced no measureable change in the polarization resistance measured at the corrosion potential. The dissolution rate ranged from 1 to 3 mg/m2-day, which is similar to the range of dissolution rates for SIMFUEL and SNF reported in the literature for comparable conditions. SIMFUEL burnup did not have a major effect on the dissolution rate. Analysis of the solution chemistry shows that uranium is the dominant element dissolved in the posttest solutions, and the dissolution rates calculated from uranium (U) concentrations are consistent with the dissolution rates obtained from impedance measurements. Simulated-fission product elements (i.e., barium, molybdenum, strontium, and zirconium) dissolved from the SIMFUEL electrode at a relatively high rate. Sorption test results indicated significant sorption of U onto the oxide formed on stainless steel. Electrochemical methods were found to be effective for measuring the uranium dissolution rate in real time.

ChemInform Abstract: Using Phosphonates to Probe Structural Differences Between Transuranium Elements and Their Proposed Surrogates

AbstractReview: 41 refs.

USING PHOSPHONATES TO PROBE STRUCTURAL DIFFERENCES BETWEEN TRANSURANIUM ELEMENTS AND THEIR PROPOSED SURROGATES

A variety of transuranium phosphonates have now been prepared and structurally characterized allowing for comparisons to be made with other metal ions that have been proposed to be surrogates for transuranics (e.g., Zr4+, Ce4+, Th4+, and U4+). The phosphonates that will be discussed in this work include Np(CH3PO3)(CH3PO3H)(NO3)(H2O)·H2O, Pu(CH3PO3)2, M[CH2(PO3)2](H2O)n (M=Ce, Th, U, Np, Pu; n = 0 − 2), and UO2An(H2O)2[CH2(PO3)(PO3H)]2 (An = Th, Np, Pu). Through the examination of these structures, rare coordination geometries for actinides have been uncovered. Simple periodic trends based solely on ionic radii are absent. However, there are examples where surrogate elements adopt the same composition and structure as transuranics, such as Pu(CH3PO3)2 versus Zr(CH3PO3)2.

Incorporation of cerium and neodymium in uranyl phases

The potential for incorporating rare earth elements (REE) into/onto crystalline compounds has been evaluated by precipitating uranyl phases from aqueous solutions containing either cerium or neodymium. These REEs serve both as monitors for evaluating the potential repository behavior of REE radionuclides, and as surrogate elements for actinides (e.g., Ce4+ and Nd3+ for Pu4+ and Am3+, respectively). The present experiments examined the behavior of REE in the presence of ianthinite ([U24+(UO2)4O6(OH)4(H2O)4](H2O)5), becquerelite (Ca(UO2)6O4(OH)6(H2O)8), and other uranyl hydroxide compounds commonly noted as alteration products during the corrosion of UO2, spent nuclear fuel, and naturally occurring uraninite. The results of these experiments demonstrate that significant quantities of both cerium (Kd=1020) and neodymium (Kd=840) are incorporated within the uranium alteration phases and suggest that ionic substitution and/or adsorption to the uranyl phases can play a key role in the limiting the mobility of REE (and by analogy, actinide elements) in a nuclear waste repository.

Incorporation of Cerium and Neodymium in a Uranyl Hydroxide Solid

ABSTRACTThe migration behavior of radionuclides in a nuclear-waste repository will be influenced, in part, by their equilibrium solubilities in the presence of radionuclide-bearing solids and/or adsorption affinities as trace components onto the surfaces of solid host phases. Uranium phases that precipitate on the surface of altered spent nuclear fuel may thus influence the mobility of radionuclides released in the near-field environment, since by proximity, these will be the first phases that the radionuclides encounter following their release from the spent fuel matrix.We have evaluated the potential for incorporating radionuclides into crystalline compounds by precipitating uranyl phases from aqueous solutions containing dissolved rare earth elements (REE; 2.1 ppm Ce4+, 4.6 ppm Ce4+, or 286 ppm Nd3+). Rare earth elements serve both as monitors for evaluating the potential behavior of REE radionuclides and as surrogate elements for the actinides (e.g., Ce4+ and Nd3+ for Pu4+ and Am3+, respectively). Although the crystalline compound that formed in the present set of experiments has not been positively identified, x-ray diffraction profiles suggest the presence of a uranyl hydroxide (UO2(OH)2) as the principal reaction product. An analysis of the crystalline products indicate a progressive decrease in concentration of cerium; from 26, to 20, and finally 11 ppm for crystals produced in 7-, 35-, and 190-day tests, respectively (Kd = 14, 11, 3, respectively). Results with neodymium display a similar trend, with concentrations in the solid decreasing from 1240 to 922 ppm between 7 and 35 days of reaction (Kd = 14 and 11, respectively). The decreasing concentration of REEs in the uranyl crystals can be correlated with both a coarsening in crystal size and a decrease in the concentration of dissolved uranium over time. Thus, REE incorporation in the crystalline solids decreases in conjunction with a decrease in the ratio of surface area/volume of the crystals, a decrease in the rate of crystal growth as uranium concentrations are lowered, or both. These data also suggest that adsorption of REE (and by analogy, actinides) onto crystal surfaces and subsequent trapping by crystal overgrowth processes may play key roles in the limiting the mobility of radionuclides in a nuclear waste repository.

B207 アークプラズマ加熱によるジルカロイ廃材の溶融 : 加熱条件と溶融状態および溶融時の核種挙動

Among the various reprocessing wastes to be generated by future nuclear fuel cycles, the volume of hulls and end-pieces of cladded fuel structure segments must be reduced. Although are plasma melting has been considered a possible method, zircaloy, a major hull component, has an extremely high melting point, and experimental verification of are plasma melting has not been completed in Japan. In the study, we performed melting and solidification experiments in a small-sized are plasma melting furnace containing a graphite crucible, using unused zircaloy waste as simulated hull material. Its melting behavior was studied with respect to the following parameters : heating energy and heating atmosphere, and the method of introduction of the waste into the furnace. The study showed that for efficient melting, a small amount of waste at a time should be introduced into a nonwater-cooled crucible and that the waste should be briefly exposed to plasma. According to thermodynamic properties such as saturated vapor pressure of lanthanide elements and transuranic elements, surrogate elements are selected to simulate migration behavior of TRU elements during thermal plasma melting of TRU wastes. These elements are simultaneously melted by thermal plasma heating with zircaloy. The surrogate elements have a tendency not to migrate into dust.

Feasibility Limits in Using Cerium as a Surrogate for Plutonium Incorporation in Zircon, Zirconia and Pyrochlore

ABSTRACTCerium is a well-known surrogate element for Pu that is widely used in experiments on the synthesis and study of ceramic waste forms for actinide immobilization. Cathodoluminescence (CL) images and emission spectra from synthetic zircon, (Zr,…)SiO4, cubic zirconia, (Zr,Y,Gd,…)O2 and pyrochlore, Ca(Hf,Gd,…)Ti2O7, individually doped with Ce and Pu were investigated. It was determined that some of the Ce, which was added as Ce4+ in the form of CeO2, was converted to the 3+ valence state during synthesis of zircon-based ceramics by sintering in air and in argon gas. However, Pu-doped zircon synthesized in air under the same conditions does not exhibit the CL emission of Pu3+. Analysis of CL spectra of cubic zirconia doped with Ce as well as Pu suggests that both ions are in the tetra-valent state in these synthetic materials. However, the CL peak of Ce-doped zirconia is almost identical to that of pure zirconia (2.6 eV). The CL peak for Pu-doped zirconia is shifted to 2.4 eV. No CL emission of Ce3+ or Pu3+ was observed in pyrochlore samples. The CL spectra for Ce-and Pu-doped pyrochlore samples were almost identical. We suggest that under oxidizing conditions Ce is good surrogate of Pu for experiments on the synthesis of pyrochlore-based and acceptable enough for zirconia- based ceramics. The use of Ce as Pu surrogate for zircon-based ceramics should be considered as limited.

Evaluation of Phase- and Element Distribution After Non-Traditional In Situ Vitrification (NTISV) at Los Alamos National Laboratory on a Simulated Adsorption Bed

A cold test demonstration of the Geosafe® Non-TraditionalIn-Situ Vitrification technology (NTISV) was performed at a simulated adsorption bed by using commercial-scale equipment. A successful demonstration of NTISV at Los Alamos National Laboratory (LANL) is expected to provide a useful technology for remediation needs of EM-40 in the U.S. Department of Energy (DOT) complex on legacy buried waste containing organics and radionuclides in geological environments. Therefore, a simulated test bed including surrogates was prepared to evaluate the impact this technology has on immobilizing radionuclides. The total volume of the cold demonstration vitrification was 3.1 m × 4.6 m × 4.9 m resulting in 176,667 kg of glass or glassy constituents. A drill core sample was removed from the glass monolith and divided into 13 samples to gain spatial (vertical) information about (a) vitrification progress, (b) phase distribution, and (c) element distribution. Based upon optical microscopy, least square and Rietveld refinement of the X-ray diffraction data, the phase constitution was determined and a temperature profile estimated. The glass compositions as well as the concentrations of surrogates and trace metals were analyzed by using X-ray Fluorescence Analysis, Electron-beam Microprobe Analysis, and Scanning Electron Microscopy. In the main melting zone, in the depth range 3.7 m to 6.3 m, NTISV successfully vitrified the geological formation (Bandelier Tuffl Unit 2/3 of Tshirege) and convert it mainly into 98-99 wt.-% silicate-based glass and 1-2 wt.-% iron-based metal inclusions. Within this zone the glass compositions have been found to be nearly constant and the surrogate elements (cerium and cesium) are distributed homogeneously.