WorldWideScience

Sample records for americium silicides

  1. Preparation of americium amalgam

    International Nuclear Information System (INIS)

    The authors describe a method for the electrochemical preparation of an americium amalgam from americium dioxide and americium 241 and 243 for use in determining the physicochemical properties of the alloy. Moessbauer spectra were made using neptunium dioxide, in the neptunium 237 form, as an absorber. Results show that electrolysis produces a homogeneous amalgam that gives an unoxidized product on vacuum distillation at 200 degrees C

  2. Preparation of americium amalgam

    International Nuclear Information System (INIS)

    Using the method of NGR-spectroscopy with the aid of 241Am isotope chemical state of transuranium elements in the volume and on the surface of amalgams is studied. Amalgam preparation was realized in a simplified electrolytic cell. It is shown that in the process of amalgam preparation the first order of reaction as to actinide is observed; americium is distributed gradually over the volume and it is partially sorbed by the surface of glass capillary. NGR spectrum of dry residue after mercury distillation at 200 deg C points to the presence of americium-mercury intermetal compounds

  3. 1976 Hanford americium accident

    Energy Technology Data Exchange (ETDEWEB)

    Heid, K R; Breitenstein, B D; Palmer, H E; McMurray, B J; Wald, N

    1979-01-01

    This report presents the 2.5-year medical course of a 64-year-old Hanford nuclear chemical operator who was involved in an accident in an americium recovery facility in August 1976. He was heavily externally contaminated with americium, sustained a substantial internal deposition of this isotope, and was burned with concentrated nitric acid and injured by flying debris about the face and neck. The medical care given the patient, including the decontamination efforts and clinical laboratory studies, are discussed. In-vivo measurements were used to estimate the dose rates and the accumulated doses to body organs. Urinary and fecal excreta were collected and analyzed for americium content. Interpretation of these data was complicated by the fact that the intake resulted both from inhalation and from solubilization of the americium embedded in facial tissues. A total of 1100 ..mu..Ci was excreted in urine and feces during the first 2 years following the accident. The long-term use of diethylenetriaminepentate (DTPA), used principally as the zinc salt, is discussed including the method, route of administration, and effectiveness. To date, the patient has apparently experienced no complications attributable to this extensive course of therapy, even though he has been given approximately 560 grams of DTPA. 4 figures, 1 table.

  4. Chemistry of americium

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, W.W.

    1976-01-01

    Essential features of the descriptive chemistry of americium are reviewed. Chapter titles are: discovery, atomic and nuclear properties, collateral reading, production and uses, chemistry in aqueous solution, metal, alloys, and compounds, and, recovery, separation, purification. Author and subject indexes are included. (JCB)

  5. The Biokinetic Model of Americium

    Institute of Scientific and Technical Information of China (English)

    2011-01-01

    To improve in vivo measurements for detecting internal exposure from transuranium radio nuclides, such as neptunium, plutonium, americium, the bioknetic model was studied. According to ICRP report (1993, 1995, 1997) and other research, the

  6. Americium product solidification and disposal

    International Nuclear Information System (INIS)

    The americium product from the TRUEX processing plant needs to be converted into a form suitable for ultimate disposal. An evaluation of the disposal based on safety, number of process steps, demonstrated operability of the processes, production of low-level alpha waste streams, and simplicity of maintenance with low radiation exposures to personnel during maintenance, has been made. The best process is to load the americium on a cation exchange resin followed by calcination or oxidation of the resin after loading

  7. Optical properties of beta-iron silicide, ruthenium silicide and osmium silicide: Semiconducting transition metal silicides

    Science.gov (United States)

    Birdwell, Anthony Glen

    2001-09-01

    Various optical techniques were used to study the semiconducting transition metal silicides of β- FeSi2, Ru2Si3, and OsSi2. The Raman spectra of ion beam synthesized (IBS) β-FeSi 2 were shown to provide evidence of a net tensile stress in these IBS materials. Possible origins of the observed stress were suggested and a simple model was proposed in order to calculate a value of the observed stress. A correlation between the tensile stress, the nature of the band gap, and the resulting light emitting properties of IBS β-FeSi2 was suggested. The photoreflectance (PR) spectra of IBS β- FeSi2 reveals a direct gap at 0.815 eV and were shown to agree with the band gap value obtained by photoluminescence (PL) once the adjustments for the temperature difference and trap related recombination effects were made. This provides very convincing evidence for intrinsic light emission from IBS β- FeSi2. Furthermore, a model was developed that helps to clarify the variety of inconsistent results obtained by optical absorption measurements. When the results of PL and PR were inserted into this model, a good agreement was obtained with our measured optical absorption results. We also obtained PR spectra of β-FeSi 2 thin films grown by molecular beam epitaxy. These spectra reveal the multiple direct transitions near the fundamental absorption edge of β-FeSi 2 that were predicted by theory. We suggest an order of these critical point transitions following the trends reported in the theoretical investigations. Doping these β-FeSi2 thin films with small amounts of chromium was shown to have a measurable effect on the interband optical spectra. We also report on the effects of alloying β- FeSi2 with cobalt. A decrease in the critical point transitions nearest the fundamental absorption edge was observed as the cobalt concentration increased. Finally, Raman spectroscopy was used to study the vibrational properties of β-FeSi2. The measured Raman spectra agreed very well with the

  8. On Silicides in High Temperature Titanium Alloys

    Directory of Open Access Journals (Sweden)

    C. Ramachandra

    1986-04-01

    Full Text Available High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr5Si3(S1 and (TiZr6 Si3 (S2, have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatment on the distribution of silicides have been pointed out. The effect of silicides on mechanical properties and fracture of the commercial alloy IMI 685 is also indicated.

  9. METHOD OF FORMING TANTALUM SILICIDE ON TANTALUM SURFACES

    Science.gov (United States)

    Bowman, M.G.; Krikorian, N.H.

    1961-10-01

    A method is described for forming a non-corrosive silicide coating on tantalum. The coating is made through the heating of trirhenium silicides in contact with the tantalum object to approximately 1400 deg C at which temperature trirhenium silicide decomposes into rhenium and gaseous silicons. The silicon vapor reacts with the tantalum surface to form a tantalum silicide layer approximately 10 microns thick. (AEC)

  10. Spectrochemical analysis of curium and americium samples

    International Nuclear Information System (INIS)

    Spectrochemical procedures have been developed to determine impurities in americium and curium samples. The simultaneous separation of many impurity elements from the base material (americium and curium) is carried out with extraction and extraction-chromatographic methods using di-2-ethylhexylphosphoric acid. It is shown that part of the elements are separated with extraction or sorption of americium and curium; the other part with the Talspeak process. Two fractions in the extraction chromatography and three fractions in the extraction separation of americium and curium, containing impurities, are analyzed separately by a.c. or d.c. arc spectrography. To increase the sensitivity of the spectrographic analysis and accelerate the burn-up of impurities from the crater of the carbon electrode bismuth fluoride and sodium chloride were used as chemically active substances. The extraction of impurities from weighed quantities of americium and curium samples of 5 to 10 mg permits the lower limit of determined impurity concentrations to be extended to 1 x 10-4 to 5 x 10-3% m/m. (author)

  11. New silicides for new niobium protective coatings

    International Nuclear Information System (INIS)

    Efforts to improve at high temperature the oxidation resistance of pure niobium or commercial niobium alloys have led to the development of a pack cementation process for the co-deposition of Si, Ti, Cr and Fe. Owing to the knowledge of the quaternary Nb(Ti)-T-Cr-Si phase diagrams (T=Fe or Co or Ni) and of the crystallographic features of phases present in the silicide coatings, new protective coatings have been applied on pure niobium and Cb752 alloy. The results of the crystallographic study of three new silicides isostructural with Nb3Fe3CrSi6, in which Nb is substituted by Ti and Fe by Co or Ni are reported. The oxidation performances of two new coatings mainly consisting of such a silicide are also outlined. (orig.)

  12. Pyrochemical technology of plutonium and americium preparation and purification

    International Nuclear Information System (INIS)

    Pyrochemical tecnology of metallic plutonium and americium preparation and purification is considered. Investigations into plutonium dioxide reduction up to metal; plutonium electrolytic refining in molten salts; plutonium extraction from the molten salts and preparation of americium dioxide and metallic americium from its tetrafluoride are described

  13. Aqueous Chloride Operations Overview: Plutonium and Americium Purification/Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Kimball, David Bryan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Skidmore, Bradley Evan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-06-22

    Acqueous Chloride mission is to recover plutonium and americium from pyrochemical residues (undesirable form for utilization and storage) and generate plutonium oxide and americium oxide. Plutonium oxide is recycled into Pu metal production flowsheet. It is suitable for storage. Americium oxide is a valuable product, sold through the DOE-OS isotope sales program.

  14. On Silicides in High Temperature Titanium Alloys

    OpenAIRE

    Ramachandra, C.; Vakil Singh; P. Rama Rao

    1986-01-01

    High temperature titanium alloys like IMI 685 contain small amounts of silicon (~ 0.25 wt. per cent) to improve creep resistance. Different types of silicides, namely Ti5Si3 (TiZr)5Si3(S1) and (TiZr)6 Si3 (S2), have been observed to precipitate in various silicon-bearing titanium alloys depending upon their composition and heat treatment. The precipitation of silicides, their orientation relationship with the matrix in different alloys, and the beneficial influence of thermo-mechanical treatm...

  15. Synthesis and design of silicide intermetallic materials

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.; Castro, R.G.; Butt, D.P. [Los Alamos National Lab., NM (United States)] [and others

    1997-04-01

    The overall objective of this program is to develop structural silicide-based materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation and corrosion resistance for applications of importance to the U.S. processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature materials and important applications in major energy-intensive U.S. processing industries. The program presently has a number of developing industrial connections, including a CRADA with Schuller International Inc. targeted at the area of MoSi{sub 2}-based high temperature materials and components for fiberglass melting and processing applications. The authors are also developing an interaction with the Institute of Gas Technology (IGT) to develop silicides for high temperature radiant gas burner applications, for the glass and other industries. Current experimental emphasis is on the development and characterization of MoSi{sub 2}-Si{sub 3}N{sub 4} and MoSi{sub 2}-SiC composites, the plasma spraying of MoSi{sub 2}-based materials, and the joining of MoSi{sub 2} materials to metals.

  16. On the kinetics of platinum silicide formation

    NARCIS (Netherlands)

    Faber, Erik J.; Wolters, Rob A.M.; Schmitz, Jurriaan

    2011-01-01

    In this work, the kinetics of platinum silicide formation for thin Pt films (50 nm) on monocrystalline <100> silicon is investigated via in situ resistance measurements under isothermal (197–275 °C) conditions. For Pt2Si diffusion limited growth was observed. For PtSi formation, however, no linear r

  17. 1976 Hanford americium exposure incident: psychological aspects

    International Nuclear Information System (INIS)

    Accidents involving exposure to radiation or radioactive materials may involve an unusual degree of emotional trauma. Methods that may be employed in dealing with such trauma are discussed in relation to a specific accident in which a radiation worker was injured and seriously contaminated with americium-241

  18. Microwave absorption properties of Ni/(C, silicides) nanocapsules

    Science.gov (United States)

    Jiang, Jingjing; Wang, Han; Guo, Huaihong; Yang, Teng; Tang, Wen-Shu; Li, Da; Ma, Song; Geng, Dianyu; Liu, Wei; Zhang, Zhidong

    2012-05-01

    The microwave absorption properties of Ni/(C, silicides) nanocapsules prepared by an arc discharge method have been studied. The composition and the microstructure of the Ni/(C, silicides) nanocapsules were determined by means of X-ray diffraction, X-ray photoelectric spectroscopy, and transmission electron microscope observations. Silicides, in the forms of SiOx and SiC, mainly exist in the shells of the nanocapsules and result in a large amount of defects at the `core/shell' interfaces as well as in the shells. The complex permittivity and microwave absorption properties of the Ni/(C, silicides) nanocapsules are improved by the doped silicides. Compared with those of Ni/C nanocapsules, the positions of maximum absorption peaks of the Ni/(C, silicides) nanocapsules exhibit large red shifts. An electric dipole model is proposed to explain this red shift phenomenon.

  19. Palladium silicide - a new contact for semiconductor radiation detectors

    International Nuclear Information System (INIS)

    Silicide layers can be used as low resistance contacts in semiconductor devices. The formation of a metal rich palladium silicide Pd2Si is discussed. A palladium film 100A thick is deposited at 3000C and the resulting silicide layer used as an ohmic contact in an n + p silicon detector. This rugged contact has electrical characteristics comparable with existing evaporated gold contacts and enables the use of more reproducible bonding techniques. (author)

  20. Production of Mo-99 using low-enriched uranium silicide

    International Nuclear Information System (INIS)

    Over the last several years, uranium silicide fuels have been under development as low-enriched uranium (LEU) targets for Mo-99. The use of LEU silicide is aimed at replacing the UAlx alloy in the highly-enriched uranium dissolution process. A process to recover Mo-99 from low-enriched uranium silicide is being developed at Argonne National Laboratory. The uranium silicide is dissolved in alkaline hydrogen peroxide. Experiments performed to determine the optimum dissolution procedure are discussed, and the results of dissolving a portion of a high-burnup (>40%) U3Si2 miniplate are presented. Future work related to Mo-99 separation and waste disposal are also discussed

  1. Solution synthesis of metal silicide nanoparticles.

    Science.gov (United States)

    McEnaney, Joshua M; Schaak, Raymond E

    2015-02-01

    Transition-metal silicides are part of an important family of intermetallic compounds, but the high-temperature reactions that are generally required to synthesize them preclude the formation of colloidal nanoparticles. Here, we show that palladium, copper, and nickel nanoparticles react with monophenylsilane in trioctylamine and squalane at 375 °C to form colloidal Pd(2)Si, Cu(3)Si, and Ni(2)Si nanoparticles, respectively. These metal silicide nanoparticles were screened as electrocatalysts for the hydrogen evolution reaction, and Pd(2)Si and Ni(2)Si were identified as active catalysts that require overpotentials of -192 and -243 mV, respectively, to produce cathodic current densities of -10 mA cm(-2).

  2. Fusion silicide coatings for tantalum alloys.

    Science.gov (United States)

    Warnock, R. V.; Stetson, A. R.

    1972-01-01

    Calculation of the performance of fusion silicide coatings under simulated atmospheric reentry conditions to a maximum temperature of 1810 K (2800 F). Both recently developed and commercially available coatings are included. Data are presented on oxidation rate with and without intentional defecting, the influence of the coatings on the ductile-brittle bend transition temperature, and the mechanical properties. Coatings appear capable of affording protection for at least 100 simulated cycles to 2600 F and 63 cycles to 2800 F.

  3. Silicides and germanides for nano-CMOS applications

    Energy Technology Data Exchange (ETDEWEB)

    Kittl, J.A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)], E-mail: kittlj@imec.be; Opsomer, K.; Torregiani, C.; Demeurisse, C.; Mertens, S.; Brunco, D.P.; Van Dal, M.J.H.; Lauwers, A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2008-12-05

    An overview of silicides and germanides for nano-CMOS applications is presented. The historical evolution describing the migration from the use of Ti silicide to Co silicide to Ni silicide as contacting material is first discussed. These changes in silicide material were mainly motivated by the inability to form the target low resistivity silicide phase in small structures due to low nucleation density. This issue was found first for the low resistivity C54 TiSi{sub 2} at linewidths below 200 nm and later for the low resistivity CoSi{sub 2}, at linewidths below 40 nm. A detailed description of scalability and thermal stability issues for NiSi is then presented. No nucleation issues were found in small structures for NiSi, which grows by diffusion or interface limited kinetics with Ni as main moving species. However, silicidation can be excessive in small structures due to Ni diffusion from surrounding areas, resulting in thicker films than targeted in small devices. This can be controlled by using a silicidation process with two rapid thermal processing steps, the first one to control the amount of Ni reacted and the second one to convert the silicide to the target low resistivity monosilicide phase. One of the main issues for applications of NiSi is its low thermal stability: thin NiSi films agglomerate at relatively low temperatures. The process window and thermal stability of Ni and Pt-based films reacted with Si, Si:Ge and Si:C substrates is reviewed. Addition of Ge is shown to degrade thermal stability while addition of C or Pt improves it. Contact resistivity considerations and implementation of dual band-edge silicides are discussed, as well as promising results for the extension of Ni-based silicides to future nodes. Finally a brief overview of germanides is presented discussing NiGe and PdGe as main candidates.

  4. High temperature protective silicide coatings for titanium-niobium alloys

    International Nuclear Information System (INIS)

    The accomplished investigation of heat resistance of silicide coatings on titanium - (30-50)% niobium alloys has revealed that the coatings ensure reliable corrosion protection up to 1100 deg due to formation of heat resistant disilicides and a silicon dioxide layer on alloy surface. Silicide coatings possess particular ductility

  5. Thermal Stability of Magnesium Silicide/Nickel Contacts

    Science.gov (United States)

    de Boor, J.; Droste, D.; Schneider, C.; Janek, J.; Mueller, E.

    2016-10-01

    Magnesium silicide-based materials are a very promising class of thermoelectric materials with excellent potential for thermoelectric waste heat recovery. For the successful application of magnesium silicide-based thermoelectric generators, the development of long-term stable contacts with low contact resistance is as important as material optimization. We have therefore studied the suitability of Ni as a contact material for magnesium silicide. Co-sintering of magnesium silicide and Ni leads to the formation of a stable reaction layer with low electrical resistance. In this paper we show that the contacts retain their low electrical contact resistance after annealing at temperatures up to 823 K for up to 168 h. By employing scanning electron microscope analysis and time-of-flight (ToF)-secondary ion mass spectrometry, we can further show that elemental diffusion is occurring to a very limited extent. This indicates long-term stability under practical operation conditions for magnesium silicide/nickel contacts.

  6. The growth and applications of silicides for nanoscale devices.

    Science.gov (United States)

    Lin, Yung-Chen; Chen, Yu; Huang, Yu

    2012-03-01

    Metal silicides have been used in silicon technology as contacts to achieve high device performance and desired device functions. The growth and applications of silicide materials have recently attracted increasing interest for nanoscale device applications. Nanoscale silicide materials have been demonstrated with various synthetic approaches. Solid state reaction wherein high quality silicides form through diffusion of metal atoms into silicon nano-templates and the subsequent phase transformation caught significant attention for the fabrication of nanoscale Si devices. Very interestingly, studies on the diffusion and phase transformation processes at the nanoscale have indicated possible deviations from the bulk and the thin film system. Here we present a review of fabrication, growth kinetics, electronic properties and device applications of nanoscale silicides formed through solid state reaction.

  7. Incentives for transmutation of americium in thermal reactors

    International Nuclear Information System (INIS)

    This report describes possible benefits when americium is irradiated in a thermal reactor. If all plutonium is partitioned from spent fuel, americium is the main contributor to the radiotoxicity of spent fuel upto several thousands of years of storage. It is shown that americium can be transmuted to other nuclides upon irradiation in a thermal reactor, leading to a 50% reduction of the radiotoxicity of neptunium, which can be an important contributor to the dose due to leakage of nuclides after one million years of storage. The radiotoxicity of americium can be reduced considerably after irradiation for 3 to 6 years in a thermal reactor with thermal neutron flux of 1014 cm-2s-1. The strongly α and neutron emitting transmutation products can most probably not be recycled again, so a transmutation process is suggested in which americium is irradiated for 3 to 6 years and then put to final storage. It is shown that the radiotoxicity of the transmuation products after a storage time of about one hundred years can be considerably reduced compared to the radiotoxicity of the initial americium. The same holds for the α activity and heat emission of the transmutation products. Because plutonium in spent fuel contributes for about 80% to the radiotoxicity upto 105 years of storage, recycling and transmutation of plutonium has first priority. Transmutation of americium is only meaningful when the radiotoxicity of plutonium is reduced far below the radiotoxicity of americium. (orig.)

  8. Surface complexation modeling of americium sorption onto volcanic tuff.

    Science.gov (United States)

    Ding, M; Kelkar, S; Meijer, A

    2014-10-01

    Results of a surface complexation model (SCM) for americium sorption on volcanic rocks (devitrified and zeolitic tuff) are presented. The model was developed using PHREEQC and based on laboratory data for americium sorption on quartz. Available data for sorption of americium on quartz as a function of pH in dilute groundwater can be modeled with two surface reactions involving an americium sulfate and an americium carbonate complex. It was assumed in applying the model to volcanic rocks from Yucca Mountain, that the surface properties of volcanic rocks can be represented by a quartz surface. Using groundwaters compositionally representative of Yucca Mountain, americium sorption distribution coefficient (Kd, L/Kg) values were calculated as function of pH. These Kd values are close to the experimentally determined Kd values for americium sorption on volcanic rocks, decreasing with increasing pH in the pH range from 7 to 9. The surface complexation constants, derived in this study, allow prediction of sorption of americium in a natural complex system, taking into account the inherent uncertainty associated with geochemical conditions that occur along transport pathways.

  9. Infrared spectra of semiconducting silicides nanolayers

    Energy Technology Data Exchange (ETDEWEB)

    Baleva, M; Atanassov, A [Faculty of Physics, St. Kl. Ohridski University of Sofia, 5 J. Bourchier Blvd., 1164 Sofia (Bulgaria); Marinova, M [Solid State Physics Section, Department of Physics, Aristotle University of Thessaloniki, 54124 Thessaloniki (Greece)], E-mail: baleva@phys.uni-sofia.bg

    2008-05-01

    The infrared absorption is studied of samples consisting of a Si matrix with unburied nanolayers of the semiconducting silicides {beta}-FeSi{sub 2} and Mg{sub 2}Si. Features additional to those due to the transversal optical phonons of the compounds are observed. The features are interpreted in the framework of the appearance of surface and interface phonon polaritons, which absorb the light. Insofar as the frequencies of the longitudinal optical (LO) phonon-polariton modes are close to those of the LO phonon frequencies, the infrared transmittance of nanolayers can be regarded as a method for direct determination of these frequencies.

  10. Electrochemical oxidation of americium in nitric medium: study of reaction mechanisms; Oxydation de l'americium par voie electrochimique: etude des mecanismes

    Energy Technology Data Exchange (ETDEWEB)

    Picart, S.; Chartier, D.; Donnet, L.; Adnet, J.M. [CEA Valrho, (DCC/DRRV/SPHA), 30 - Marcoule (France)

    2000-07-01

    One alternative selected by the CEA for partitioning minor actinides from aqueous solutions containing fission products is the selective extraction of oxidized americium. This is the SESAME process (Selective Extraction and Separation of Americium by Means of Electrolysis) aimed to convert americium to oxidation state (VI) and then extract it with a specific extractant of high valences. This paper presents the study of the electrochemical oxidation of americium in nitric medium which represents an important stage of the process. The reaction can be divided into two main steps: oxidation of americium (III) to americium (IV), and then of americium (IV) to americium (VI). For the first oxidation step, a ligand L is needed to stabilize the intermediate species americium (IV) which disproportionates in its free form into americium (III) and (V). Phospho-tungstate or silico-tungstate are appropriate ligands because they are stable in concentrated nitric acid and show a great affinity for metallic cations at oxidation state (IV) (Table 1 lists the stability constants of americium (IV) complexes). The presence of the lacunary poly-anion lowers the potential of the americium (IV) / americium (Ill) redox pair (see Figure 5 for the diagram of the apparent formal potential of americium versus ligand concentration). This makes it thermodynamically possible to oxidize americium (III) into americium (IV) at the anode of an electrolyzer in nitric acid. For the second oxidation step, a strong oxidant redox mediator, like silver (II), is needed to convert complexed americium at oxidation state (IV) to oxidation state (V). The AmVL complex is then hydrolyzed to yield americyle (V) aqua ion. A spectroscopic Raman study with {sup 18}O labeled species showed that the oxygen atoms of the americyle moiety came from water. This indicates that water hydrolyzes the americium (V) complex to produce americyle (V) aqua ion, AmO{sub 2}{sup +}. This cation reacts with silver (Il) to give

  11. Higher Americium Oxidation State Research Roadmap

    Energy Technology Data Exchange (ETDEWEB)

    Mincher, Bruce J. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Law, Jack D. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Goff, George S. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Moyer, Bruce A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Burns, Jon D. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Lumetta, Gregg J. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Sinkov, Sergey I. [Pacific Northwest National Lab. (PNNL), Richland, WA (United States); Shehee, Thomas C. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL); Hobbs, David T. [Savannah River Site (SRS), Aiken, SC (United States). Savannah River National Lab. (SRNL)

    2015-12-18

    The partitioning of hexavalent Am from dissolved nuclear fuel requires the ability to efficiently oxidize Am(III) to Am(VI) and to maintain that oxidation state for a length of time sufficient to perform the separation. Several oxidants have been, or are being developed. Chemical oxidants include Ag-catalyzed ozone, Ag-catalyzed peroxydisulfate, Cu(III) periodate, and sodium bismuthate. Hexavalent americium has also now successfully been prepared by electrolysis, using functionalized electrodes. So-called auto-reduction rates of Am(VI) are sufficiently slow to allow for separations. However, for separations based on solvent extraction or ion exchange using organic resins, the high valence state must be maintained under the reducing conditions of the organic phase contact, and a holding oxidant is probably necessary. Until now, only Cu(III) periodate and sodium bismuthate oxidation have been successfully combined with solvent extraction separations. Bismuthate oxidation provided the higher DAm, since it acts as its own holding oxidant, and a successful hot test using centrifugal contactors was performed. For the other oxidants, Ag-catalyzed peroxydisulfate will not oxidize americium in nitric acid concentrations above 0.3 M, and it is not being further investigated. Peroxydisulfate in the absence of Ag catalysis is being used to prepare Am(V) in ion exchange work, discussed below. Preliminary work with Ag-catalyzed ozone has been unsuccessful for extractions of Am(VI) from 6.5 M HNO3, and only one attempt at extraction, also from 6.5 M HNO3, using the electrolytic oxidation has been attempted. However, this high acid concentration was based on the highest Am extraction efficiency using the bismuthate oxidant; which is only sparingly soluble, and thus the oxidation yield is based on bismuthate solubility. Lower acid concentrations may be sufficient with alternative oxidants and work with Ag-ozone, Cu(III) and electrolysis is on-going. Two non

  12. Silicide precipitation strengthened TiAl

    Energy Technology Data Exchange (ETDEWEB)

    Noda, T. [Special Steel Research Laboratory, Daido Steel Co. Ltd., 2-30 Daido-cho, Minami-ku, Nagoya 457 (Japan); Okabe, M. [Special Steel Research Laboratory, Daido Steel Co. Ltd., 2-30 Daido-cho, Minami-ku, Nagoya 457 (Japan); Isobe, S. [Special Steel Research Laboratory, Daido Steel Co. Ltd., 2-30 Daido-cho, Minami-ku, Nagoya 457 (Japan); Sayashi, M. [Materials Research Laboratory, Nissan Research Center, Nissan Motor Co. Ltd., 1 Natushima-cho, Yokosuka 237 (Japan)

    1995-02-28

    Precipitation of a titanium silicide Ti{sub 5}Si{sub 3} was found to be beneficial to improvement of the creep resistance of a fully lamellar Ti-48Al-1.5Cr cast alloy without the sacrifice of tensile properties. The addition of 0.26-0.65 mol% Si generates fine precipitates less than 200 nm in size during aging at 900 C for 5 h. The precipitates are effective obstacles to dislocation motion and raise the stress exponents of power law creep significantly. The specific creep strength of Si-containing alloys is better than that of a conventional Ni-base cast superalloy Inconel 713C at 800 C for 10000 h. ((orig.))

  13. Plutonium and Americium Geochemistry at Hanford: A Site Wide Review

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J.; Felmy, Andrew R.

    2012-08-23

    This report was produced to provide a systematic review of the state-of-knowledge of plutonium and americium geochemistry at the Hanford Site. The report integrates existing knowledge of the subsurface migration behavior of plutonium and americium at the Hanford Site with available information in the scientific literature regarding the geochemistry of plutonium and americium in systems that are environmentally relevant to the Hanford Site. As a part of the report, key research needs are identified and prioritized, with the ultimate goal of developing a science-based capability to quantitatively assess risk at sites contaminated with plutonium and americium at the Hanford Site and the impact of remediation technologies and closure strategies.

  14. Mixed chelation therapy for removal of plutonium and americium

    International Nuclear Information System (INIS)

    Iron-binding compounds, 2,3-dihydroxybenzoic acid (DHBA), 2-hydroxybenzoic acid (HBA), and 2-(acetyloxy)benzoic acid (ABA), were tested for their ability to remove americium and plutonium from rats following intraperitioneal injection of the radionuclides as citrates (pH 5). Treatments, 2 mmol/kg, were given on days 3, 6, 10, 12 and 14 following the actinide injection. DHBA and HBA caused about a 20% decrease in liver retention of americium compared to the control value, and DHB caused a similar effect for plutonium. The above agents, co-administered with 0.5 mmol polyaminopolycarboxylic acid (PAPCA)-type chelons, did not change tissue retention of americium and plutonium from that due to the PAPCAs alone. Administration of americium and plutonium to the same rats is useful for studying removal agents since the two actinides behave independently in their biological disposition and response to removal

  15. Gamma-sources on the basis of metallic americium-241

    International Nuclear Information System (INIS)

    A batch of gamma-radiation sources has been manufactured from metallic americium-241 of isotopic purity, its activity varying from 0.08 to 0.93 GBq. The cores of the sources are high-purity americium metal condensate on a tantalum or stainless steel substrate prepared by thermal decomposition of 241Pu-241Am alloy in a high vacuum. 7 refs., 1 tab

  16. Aqueous Chloride Operations Overview: Plutonium and Americium Purification/Recovery

    Energy Technology Data Exchange (ETDEWEB)

    Gardner, Kyle Shelton [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Kimball, David Bryan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Skidmore, Bradley Evan [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2016-09-28

    These are a set of slides intended for an information session as part of recruiting activities at Brigham Young University. It gives an overview of aqueous chloride operations, specifically on plutonium and americium purification/recovery. This presentation details the steps taken perform these processes, from plutonium size reduction, dissolution, solvent extraction, oxalate precipitation, to calcination. For Americium recovery, it details the CLEAR (chloride extraction and actinide recovery) Line, oxalate precipitation and calcination.

  17. Pyrochemical investigations into recovering plutonium from americium extraction salt residues

    International Nuclear Information System (INIS)

    Progress into developing a pyrochemical technique for separating and recovering plutonium from spent americium extraction waste salts has concentrated on selective chemical reduction with lanthanum metal and calcium metal and on the solvent extraction of americium with calcium metal. Both techniques are effective for recovering plutonium from the waste salt, although neither appears suitable as a separation technique for recycling a plutonium stream back to mainline purification processes. 17 refs., 13 figs., 2 tabs

  18. Rare earth silicide nanowires on silicon surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Wanke, Martina

    2008-11-10

    The growth, structure and electronic properties of rare earth silicide nanowires are investigated on planar and vicinal Si(001) und Si(111) surfaces with scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and angle-resolved photoelectron spectroscopy (ARPES). On all surfaces investigated within this work hexagonal disilicides are grown epitaxially with a lattice mismatch of -2.55% up to +0.83% along the hexagonal a-axis. Along the hexagonal c-axis the lattice mismatch is essentially larger with 6.5%. On the Si(001)2 x 1 surface two types of nanowires are grown epitaxially. The socalled broad wires show a one-dimensional metallic valence band structure with states crossing the Fermi level. Along the nanowires two strongly dispersing states at the anti J point and a strongly dispersing state at the anti {gamma} point can be observed. Along the thin nanowires dispersing states could not be observed. Merely in the direction perpendicular to the wires an intensity variation could be observed, which corresponds to the observed spacial structure of the thin nanowires. The electronic properties of the broad erbium silicide nanowires are very similar to the broad dysprosium silicide nanowires. The electronic properties of the DySi{sub 2}-monolayer and the Dy{sub 3}Si{sub 5}-multilayer on the Si(111) surface are investigated in comparison to the known ErSi{sub 2}/Si(111) and Er{sub 3}Si{sub 5}/Si(111) system. The positions and the energetic locations of the observed band in the surface Brillouin zone will be confirmed for dysprosium. The shape of the electron pockets in the (vector)k {sub parallel} space is elliptical at the anti M points, while the hole pocket at the anti {gamma} point is showing a hexagonal symmetry. On the Si(557) surface the structural and electronic properties depend strongly on the different preparation conditions likewise, in particular on the rare earth coverage. At submonolayer coverage the thin nanowires grow in wide areas

  19. Silicide Nanowires for Low-Resistance CMOS Transistor Contacts.

    Science.gov (United States)

    Zollner, Stefan

    2007-03-01

    Transition metal (TM) silicide nanowires are used as contacts for modern CMOS transistors. (Our smallest wires are ˜20 nm thick and ˜50 nm wide.) While much research on thick TM silicides was conducted long ago, materials perform differently at the nanoscale. For example, the usual phase transformation sequences (e.g., Ni, Ni2Si, NiSi, NiSi2) for the reaction of thick metal films on Si no longer apply to nanostructures, because the surface and interface energies compete with the bulk energy of a given crystal structure. Therefore, a NiSi film will agglomerate into hemispherical droplets of NiSi by annealing before it reaches the lowest-energy (NiSi2) crystalline structure. These dynamics can be tuned by addition of impurities (such as Pt in Ni). The Si surface preparation is also a more important factor for nanowires than for silicidation of thick TM films. Ni nanowires formed on Si surfaces that were cleaned and amorphized by sputtering with Ar ions have a tendency to form NiSi2 pyramids (``spikes'') even at moderate temperatures (˜400^oC), while similar Ni films formed on atomically clean or hydrogen-terminated Si form uniform NiSi nanowires. Another issue affecting TM silicides is the barrier height between the silicide contact and the silicon transistor. For most TM silicides, the Fermi level of the silicide is aligned with the center of the Si band gap. Therefore, silicide contacts experience Schottky barrier heights of around 0.5 eV for both n-type and p-type Si. The resulting contact resistance becomes a significant term for the overall resistance of modern CMOS transistors. Lowering this contact resistance is an important goal in CMOS research. New materials are under investigation (for example PtSi, which has a barrier height of only 0.3 eV to p-type Si). This talk will describe recent results, with special emphasis on characterization techniques and electrical testing useful for the development of silicide nanowires for CMOS contacts. In collaboration

  20. Electrochemical oxidation of americium in nitric medium: study of reaction mechanisms

    International Nuclear Information System (INIS)

    One alternative selected by the CEA for partitioning minor actinides from aqueous solutions containing fission products is the selective extraction of oxidized americium. This is the SESAME process (Selective Extraction and Separation of Americium by Means of Electrolysis) aimed to convert americium to oxidation state (VI) and then extract it with a specific extractant of high valences. This paper presents the study of the electrochemical oxidation of americium in nitric medium which represents an important stage of the process. The reaction can be divided into two main steps: oxidation of americium (III) to americium (IV), and then of americium (IV) to americium (VI). For the first oxidation step, a ligand L is needed to stabilize the intermediate species americium (IV) which disproportionates in its free form into americium (III) and (V). Phospho-tungstate or silico-tungstate are appropriate ligands because they are stable in concentrated nitric acid and show a great affinity for metallic cations at oxidation state (IV) (Table 1 lists the stability constants of americium (IV) complexes). The presence of the lacunary poly-anion lowers the potential of the americium (IV) / americium (Ill) redox pair (see Figure 5 for the diagram of the apparent formal potential of americium versus ligand concentration). This makes it thermodynamically possible to oxidize americium (III) into americium (IV) at the anode of an electrolyzer in nitric acid. For the second oxidation step, a strong oxidant redox mediator, like silver (II), is needed to convert complexed americium at oxidation state (IV) to oxidation state (V). The AmVL complex is then hydrolyzed to yield americyle (V) aqua ion. A spectroscopic Raman study with 18O labeled species showed that the oxygen atoms of the americyle moiety came from water. This indicates that water hydrolyzes the americium (V) complex to produce americyle (V) aqua ion, AmO2+. This cation reacts with silver (Il) to give americyle (VI) ion. Figure

  1. Formation of Silicide Coating layer on U-Mo Powder

    Energy Technology Data Exchange (ETDEWEB)

    Nam, Ji Min; Kim, Sunghwan; Lee, Kyu Hong [Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

    2014-05-15

    High-density U-Mo alloys are regarded as promising candidates for advanced research reactor fuel as they have shown stable irradiation performance when compared to other uranium alloys and compounds. However, interaction layer formation between the U-Mo alloys and Al matrix degrades the irradiation performance of U-Mo Dispersion fuel. Therefore, the addition of Ti in U-Mo alloys, the addition of Si in a Al matrix, and silicide or nitride coating on the surface of U-Mo particles have been proposed to inhibit the interaction layer growth. In this study, U-Mo alloy powder was produced using a centrifugal atomization method. In addition, silicide coating layers were fabricated by several mixing process changes on the surface of the U-Mo particles. The coated powders were characterized by using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDAX). Decreased annealing duration did not affect the forming of silicide coating layers on the surface of U-7wt%Mo powders. The variation in the mixing ratio between U-7wt%Mo and Si powders had an effect on the quality of silicide coating on the U-7wt%Mo powders. The weight of Si powders should be smaller than that of U-7wt%Mo powders for better silicide coating when it comes to the mixing ratio.

  2. Submicron Features in Higher Manganese Silicide

    Directory of Open Access Journals (Sweden)

    Yatir Sadia

    2013-01-01

    Full Text Available The world energy crisis had increased the demand for alternative energy sources and as such is one of the topics at the forefront of research. One way for reducing energy consumption is by thermoelectricity. Thermoelectric effects enable direct conversion of thermal into electrical energy. Higher manganese silicide (HMS, MnSi1.75 is one of the promising materials for applications in the field of thermoelectricity. The abundance and low cost of the elements, combined with good thermoelectric properties and high mechanical and chemical stability at high temperatures, make it very attractive for thermoelectric applications. Recent studies have shown that Si-rich HMS has improved thermoelectric properties. The most interesting of which is the unusual reduction in thermal conductivity. In the current research, transmission (TEM and scanning (SEM electron microscopy as well as X-ray diffraction methods were applied for investigation of the govern mechanisms resulting in very low thermal conductivity values of an Si-rich HMS composition, following arc melting and hot-pressing procedures. In this paper, it is shown that there is a presence of sub-micron dislocations walls, stacking faults, and silicon and HMS precipitates inside each other apparent in the matrix, following a high temperature (0.9 Tm hot pressing for an hour. These are not just responsible for the low thermal conductivity values observed but also indicate the ability to create complicate nano-structures that will last during the production process and possibly during the application.

  3. Applicability of insoluble tannin to treatment of waste containing americium

    International Nuclear Information System (INIS)

    The applicability of insoluble tannin adsorbent to the treatment of aqueous waste contaminated with americium has been investigated. Insoluble tannin is considered highly applicable because it consists of only carbon, hydrogen and oxygen and so its volume can be easily reduced by incineration. This report describes measurements of the americium distribution coefficient in low concentration nitric acid. The americium distribution coefficients were found to decrease with increasing concentration of nitric acid and sodium nitrate, and with increasing temperature. At 25 C in 2.0 x 10-3 M HNO3, the distribution coefficient was found to be 2000 ml g-1. The adsorption capacity was determined by column experiments using europium as a simulant of americium, and found to be 7 x 10-3 mmol g-1-dried tannin in 0.01 M HNO3 at 25 C, which corresponds to approximately 1.7 mg-241Am/g-adsorbent(dried). The prospect of applying the adsorbent to the treatment of aqueous waste contaminated with americium appears promising. (orig.)

  4. Formation of cobalt silicide by ion beam mixing

    Science.gov (United States)

    Min, Ye; Burte, Edmund P.; Ryssel, Heiner

    1991-07-01

    The formation of cobalt silicides by arsenic ion implantation through a cobalt film which causes a mixing of the metal with the silicon substrate was investigated. Furthermore, cobalt suicides were formed by rapid thermal annealing (RTA). Sheet resistance and silicide phases of implanted Co/Si samples depend on the As dose. Ion beam mixing at doses higher than 5 × 10 15 cm -2 and RTA at temperatures T ⩾ 900° C result in almost equal values of Rs. RBS and XRD spectra of these samples illustrate the formation of a homogeneous CoSi 2 layer. Significant lateral growth of cobalt silicide beyond the edge of patterned SiO 2 was observed in samples which were only subjected to an RTA process ( T ⩾ 900 ° C), while this lateral suicide growth could be reduced efficiently by As implantation prior to RTA.

  5. Reaction layers structure of silicide coatings on niobium alloys

    International Nuclear Information System (INIS)

    This paper reports on fused silicide coatings that are used to protect niobium alloys against high temperature oxidation. Quantitative electron microprobe analysis was used to characterize the complex multilayer structure of Si-20w/oFE-20w/oCR fused silicide coating on four niobium containing alloys: niobium, Cb752, WC3009, and Nb-46.5 Ti. The outer coating layer structure on all four alloys was similar, consisting of either two or three phases. The three phase outer coating layer on the niobium, WC3009, and the Nb-Ti substrate alloys was determined to be made of two MSi phases and one MSi2 phase. This outer MSi2 phase contained base alloy elements. Coated samples were compared using cyclic oxidation testing. The fused silicide coating structure and protectiveness were determined to be a function of the base alloy composition

  6. Oxidation resistance of composite silicide coatings on niobium

    International Nuclear Information System (INIS)

    This paper reports the oxidation of NbSi2-MoSi2 composite silicide coatings produced by diffusive siliconizing of molybdenum films on a niobium surface. Molybdenum-coated niobium was siliconized and an x-ray microspectral analysis of the composite silicide coating showed the phase composition to be an ca 80-um-thick outer molybdenum disilicide film with a characteristic coarsely crystalline columnar structure, and inner ca 20-um film of niobium disilicide consisting of the tiny columnar crystals, and a substrate/coating interface comprising a thin, 2-3 um film of lower silicide, i.e., Nb5Si3. The average grain sizes, unit cell parameters, and x-ray determined densities of the Mo films obtained by various methods are shown

  7. Si-Ge Nano-Structured with Tungsten Silicide Inclusions

    Science.gov (United States)

    Mackey, Jon; Sehirlioglu, Alp; Dynys, Fred

    2014-01-01

    Traditional silicon germanium high temperature thermoelectrics have potential for improvements in figure of merit via nano-structuring with a silicide phase. A second phase of nano-sized silicides can theoretically reduce the lattice component of thermal conductivity without significantly reducing the electrical conductivity. However, experimentally achieving such improvements in line with the theory is complicated by factors such as control of silicide size during sintering, dopant segregation, matrix homogeneity, and sintering kinetics. Samples are prepared using powder metallurgy techniques; including mechanochemical alloying via ball milling and spark plasma sintering for densification. In addition to microstructural development, thermal stability of thermoelectric transport properties are reported, as well as couple and device level characterization.

  8. Mo SILICIDE SYNTHISIS BY DUAL ION BEAM DEPOSITION

    Institute of Scientific and Technical Information of China (English)

    T.H. Zhang; Z.Z. Yi; X.Y. Wu; S.J. Zhang; Y.G. Wu; X. Zhang; H.X. Zhang; A.D. Liu; X.J. Zhang

    2002-01-01

    Mo silicides MosSi3 with high quality were prepared using ion beam deposition equip-ment with two Filter Metal Vacuum Arc Deposition (FMEVAD). When the numberof alternant deposition times was 198, total thickness of the coating is 40nm. Thecoatings with droplet free can be readily obtained, so the surface is smooth. TEMobservation shows that Mo and Si alternant deposition coating is conpact structure.The fine Mo silicide grains densely distributed in the coating. The coating adherenceon silicon is excellent.

  9. Transition Metal Silicide Nanowires Growth and Electrical Characterization

    Institute of Scientific and Technical Information of China (English)

    PENG Zu-Lin; LIANG S.; DENG Luo-Gen

    2009-01-01

    We report the characterization of self-assembled epitaxially grown transition metal,Fe,Co,Ni,silicide nanowires(TM-NW)growth and electrical transport properties.NWs grown by reactive deposition epitaxy on various silicon surfaces show a dimension of 10nm by 5nm,and several micrometers in length.NW orientations strongly depend on substrate crystal orientation,and follow the substrate symmetry.By using conductive-AFM(c-AFM),the electron transport properties of one single NW were measured,the resistivity of crystalline nickel silicide NW was estimated to be 2×10~(-2) Ω·cm.

  10. Salvage of plutonium-and americium-contaminated metals

    International Nuclear Information System (INIS)

    Melt-slagging techniques were evaluated as a decontamination and consolidation step for metals contaminated with oxides of plutonium and americium. Experiments were performed in which mild steel, stainless steel, and nickel metals contaminated with oxides of plutonium and americium were melted in the presence of silicate slags of various compositions. The metal products were low in contamination, with the plutonium and americium strongly fractionated to the slags. Partition coefficients (plutonium in slag/plutonium in steel) of 7*10/sup 6/ with borosilicate slag and 3*10/sup 6/ for calcium, magnesium silicate slag were measured. Decontamination of metals containing as much as 14,000 p.p.m. plutonium appears to be as efficient as that of metals with plutonium levels of 400 p.p.m. Staged extraction, that is, a remelting of processed metal with clean slag, results in further decontamination of the metal. 10 refs

  11. Deposition of aluminide and silicide based protective coatings on niobium

    International Nuclear Information System (INIS)

    We compare aluminide and alumino-silicide composite coatings on niobium using halide activated pack cementation (HAPC) technique for improving its oxidation resistance. The coated samples are characterized by SEM, EDS, EPMA and hardness measurements. We observe formation of NbAl3 in aluminide coating of Nb, though the alumino-silicide coating leads to formation primarily of NbSi2 in the inner layer and a ternary compound of Nb-Si-Al in the outer layer, as reported earlier (Majumdar et al. ). Formation of niobium silicide is preferred over niobium aluminide during alumino-silicide coating experiments, indicating Si is more strongly bonded to Nb than Al, although equivalent quantities of aluminium and silicon powders were used in the pack chemistry. We also employ first-principles density functional pseudopotential-based calculations to calculate the relative stability of these intermediate phases and the adhesion strength of the Al/Nb and Si/Nb interfaces. NbSi2 exhibits much stronger covalent character as compared to NbAl3. The ideal work of adhesion for the relaxed Al/Nb and Si/Nb interfaces are calculated to be 3226 mJ/m2 and 3545 mJ/m2, respectively, indicating stronger Nb-Si bonding across the interface.

  12. Deposition of aluminide and silicide based protective coatings on niobium

    Science.gov (United States)

    Majumdar, S.; Arya, A.; Sharma, I. G.; Suri, A. K.; Banerjee, S.

    2010-11-01

    We compare aluminide and alumino-silicide composite coatings on niobium using halide activated pack cementation (HAPC) technique for improving its oxidation resistance. The coated samples are characterized by SEM, EDS, EPMA and hardness measurements. We observe formation of NbAl3 in aluminide coating of Nb, though the alumino-silicide coating leads to formation primarily of NbSi2 in the inner layer and a ternary compound of Nb-Si-Al in the outer layer, as reported earlier (Majumdar et al. [11]). Formation of niobium silicide is preferred over niobium aluminide during alumino-silicide coating experiments, indicating Si is more strongly bonded to Nb than Al, although equivalent quantities of aluminium and silicon powders were used in the pack chemistry. We also employ first-principles density functional pseudopotential-based calculations to calculate the relative stability of these intermediate phases and the adhesion strength of the Al/Nb and Si/Nb interfaces. NbSi2 exhibits much stronger covalent character as compared to NbAl3. The ideal work of adhesion for the relaxed Al/Nb and Si/Nb interfaces are calculated to be 3226 mJ/m2 and 3545 mJ/m2, respectively, indicating stronger Nb-Si bonding across the interface.

  13. A swelling model of LEU silicide fuel for KMRR

    International Nuclear Information System (INIS)

    A lot of efforts have been made internationally to understand the irradiation behavior and the safety characteristics of uranium silicide fuel. One of the important irradiation performance characteristics of the silicide dispersion fuel element is the diametral increase resulting from fuel swelling. This paper represents an attempt to develop the physical model for the swelling, DFSWELL, by modelling the basic irradiation behavior observed from in-reactor experiments. The most important part of developing the swelling model is the identification of the controlling physical processes. The swelling of the silicide fuel is comprised of the volume change due to three major components; (i) the formation of an interfacial layer between the fuel particle and matrix, (ii) the accumulation of gas bubble nucleation, (iii) the accumulation of solid fission products. In this study, the swelling of the fuel element is quantitatively estimated by considering temperature, fission rate, solid fission product build-up and gas bubble behavior. The DFSWELL model which takes into account the above physical components predicts well the absolute magnitude of silicide fuel swelling in accordance with the power histories in comparison with the experimental data

  14. 1976 Hanford americium exposure incident: overview and perspective

    International Nuclear Information System (INIS)

    Salient features of the 1976 Hanford americium exposure incident are discussed. Comparisons are made with previous human and animal exposure data, and conclusions drawn relative to the injured workman, to health physics practices, and to the adequacy of current exposure limits

  15. Study of nickel silicide formation by physical vapor deposition techniques

    Science.gov (United States)

    Pancharatnam, Shanti

    Metal silicides are used as contacts to the highly n-doped emitter in photovoltaic devices. Thin films of nickel silicide (NiSi) are of particular interest for Si-based solar cells, as they form at lower temperature and consume less silicon. However, interfacial oxide limits the reduction in sheet resistance. Hence, different diffusion barriers were investigated with regard to optimizing the conductivity and thermal stability. The formation of NiSi, and if it can be doped to have good contact with the n-side of a p-n junction were studied. Reduction of the interfacial oxide by the interfacial Ti layer to allow the formation of NiSi was observed. Silicon was treated in dilute hydrofluoric acid for removing the surface oxide layer. Ni and a Ti diffusion barrier were deposited on Si by physical vapor deposition (PVD) methods - electron beam evaporation and sputtering. The annealing temperature and time were varied to observe the stability of the deposited film. The films were then etched to observe the retention of the silicide. Characterization was done using scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and Rutherford back scattering (RBS). Sheet resistance was measured using the four-point probe technique. Annealing temperatures from 300°C showed films began to agglomerate indicating some diffusion between Ni and Si in the Ti layer, also supported by the compositional analysis in the Auger spectra. Films obtained by evaporation and sputtering were of high quality in terms of coverage over substrate area and uniformity. Thicknesses of Ni and Ti were optimized to 20 nm and 10 nm respectively. Resistivity was low at these thicknesses, and reduced by about half post annealing at 300°C for 8 hours. Thus a low resistivity contact was obtained at optimized thicknesses of the metal layers. It was also shown that some silicide formation occurs at temperatures starting from 300°C and can thus be used to make good silicide contacts.

  16. Texture in thin film silicides and germanides: A review

    Science.gov (United States)

    De Schutter, B.; De Keyser, K.; Lavoie, C.; Detavernier, C.

    2016-09-01

    Silicides and germanides are compounds consisting of a metal and silicon or germanium. In the microelectronics industry, silicides are the material of choice for contacting silicon based devices (over the years, CoSi2, C54-TiSi2, and NiSi have been adopted), while germanides are considered as a top candidate for contacting future germanium based electronics. Since also strain engineering through the use of Si1-xGex in the source/drain/gate regions of MOSFET devices is an important technique for improving device characteristics in modern Si-based microelectronics industry, a profound understanding of the formation of silicide/germanide contacts to silicon and germanium is of utmost importance. The crystallographic texture of these films, which is defined as the statistical distribution of the orientation of the grains in the film, has been the subject of scientific studies since the 1970s. Different types of texture like epitaxy, axiotaxy, fiber, or combinations thereof have been observed in such films. In recent years, it has become increasingly clear that film texture can have a profound influence on the formation and stability of silicide/germanide contacts, as it controls the type and orientation of grain boundaries (affecting diffusion and agglomeration) and the interface energy (affecting nucleation during the solid-state reaction). Furthermore, the texture also has an impact on the electrical characteristics of the contact, as the orientation and size of individual grains influences functional properties such as contact resistance and sheet resistance and will induce local variations in strain and Schottky barrier height. This review aims to give a comprehensive overview of the scientific work that has been published in the field of texture studies on thin film silicide/germanide contacts.

  17. Reduction Rates for Higher Americium Oxidation States in Nitric Acid

    Energy Technology Data Exchange (ETDEWEB)

    Grimes, Travis Shane [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mincher, Bruce Jay [Idaho National Lab. (INL), Idaho Falls, ID (United States); Schmitt, Nicholas C [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2015-09-30

    The stability of hexavalent americium was measured using multiple americium concentrations and nitric acid concentrations after contact with the strong oxidant sodium bismuthate. Contrary to our hypotheses Am(VI) was not reduced faster at higher americium concentrations, and the reduction was only zero-order at short time scales. Attempts to model the reduction kinetics using zero order kinetic models showed Am(VI) reduction in nitric acid is more complex than the autoreduction processes reported by others in perchloric acid. The classical zero-order reduction of Am(VI) was found here only for short times on the order of a few hours. We did show that the rate of Am(V) production was less than the rate of Am(VI) reduction, indicating that some Am(VI) undergoes two electron-reduction to Am(IV). We also monitored the Am(VI) reduction in contact with the organic diluent dodecane. A direct comparison of these results with those in the absence of the organic diluent showed the reduction rates for Am(VI) were not statistically different for both systems. Additional americium oxidations conducted in the presence of Ce(IV)/Ce(III) ions showed that Am(VI) is reduced without the typical growth of Am(V) observed in the systems sans Ce ion. This was an interesting result which suggests a potential new reduction/oxidation pathway for Am in the presence of Ce; however, these results were very preliminary, and will require additional experiments to understand the mechanism by which this occurs. Overall, these studies have shown that hexavalent americium is fundamentally stable enough in nitric acid to run a separations process. However, the complicated nature of the reduction pathways based on the system components is far from being rigorously understood.

  18. Synthesis and characterization of uranium-americium mixed oxides

    International Nuclear Information System (INIS)

    Americium isotopes represent a significant part of high-level and long-lived nuclear waste in spent fuels. Among the envisaged reprocessing scenarios, their transmutation in fast neutron reactors using uranium-americium mixed-oxide pellets (U1-xAmxO2±δ) is a promising option which would help decrease the ecological footprint of ultimate waste repository sites. In this context, this thesis is dedicated to the study of such compounds over a wide range of americium contents (7.5 at.% ≤ Am/(U+Am) ≤ 70 at.%), with an emphasis on their fabrication from single-oxide precursors and the assessment of their structural and thermodynamic stabilities, also taking self-irradiation effects into account. Results highlight the main influence of americium reduction to Am(+III), not only on the mechanisms of solid-state formation of the U1-xAmxO2±δ solid solution, but also on the stabilization of oxidized uranium cations and the formation of defects in the oxygen sublattice such as vacancies and cub-octahedral clusters. In addition, the data acquired concerning the stability of U1-xAmxO2±δ compounds (existence of a miscibility gap, vaporization behavior) were compared to calculations based on new thermodynamic modelling of the U-Am-O ternary system. Finally, α-self-irradiation-induced structural effects on U1-xAmxO2±δ compounds were analyzed using XRD, XAS and TEM, allowing the influence of americium content on the structural swelling to be studied as well as the description of the evolution of radiation-induced structural defects. (author)

  19. Ni based silicides for 45 nm CMOS and beyond

    Energy Technology Data Exchange (ETDEWEB)

    Lauwers, Anne [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)]. E-mail: lauwersa@imec.be; Kittl, Jorge A. [IMEC, Texas Instruments (Belgium); Van Dal, Mark J.H. [IMEC, Philips Research Leuven (Belgium); Chamirian, Oxana [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Pawlak, Malgorzata A. [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Potter, Muriel de [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Lindsay, Richard [IMEC, Kapeldreef 75, 3001 Leuven (Belgium); Raymakers, Toon [Philips Research Laboratories, Prof. Holstlaan 4, 5656 AA Eindhoven (Netherlands); Pages, Xavier [IMEC, ASM Belgium (Belgium); Mebarki, Bencherki [Applied Materials (Belgium); Mandrekar, Tushar [Applied Materials Inc., Santa Clara, CA (United States); Maex, Karen [IMEC, Kapeldreef 75, 3001 Leuven (Belgium)

    2004-12-15

    Material issues that impact the applicability of Ni based silicides to CMOS flows were studied, including the excessive silicidation of narrow features, the growth kinetics of Ni{sub 2}Si and NiSi on single-crystalline and poly-crystalline silicon and the thermal degradation mechanisms. Ni{sub 2}Si was found to grow by diffusion controlled kinetics with an activation energy of about 1.55 eV on single-crystalline Si. As a result, the excessive silicidation in small features can be reduced in a 2-step Ni-silicide process by reducing the thermal budget of the first RTP step. The mechanisms of thermal degradation of NiSi were studied. Thin NiSi films were found to degrade morphologically while still in the monosilicide phase. Thick NiSi films degrade morphologically at low temperatures and by transformation to NiSi{sub 2} at high temperatures. The reaction of Ni with SiGe substrates and the effect of Ge on the thermal degradation of the Ni-germanosilicide were investigated. Activation energies for the thermal degradation of Ni(SiGe) on SiGe were found to be significantly smaller than the values found for the thermal degradation of NiSi on pure Si. The effect of alloying Ni with Pt or Ta was studied. NiSi films alloyed with Pt or Ta are found to be thermally more stable compared to pure NiSi. Alloying with Pt was found to improve the thermal stability of NiSi on narrow poly-Si gates. The kinetics of Ni{sub 2}Si and NiSi formation on poly silicon were determined as well as their dependence on dopants. The presence of B in high doses was found to slow down the silicide formation significantly. Dopant segregation to the NiSi/oxide interface was observed, which is believed to be responsible for the observed shifts in work function. The sheet resistance of fully Ni-silicided 100 nm poly Si/oxide stacks is found to be stable up to 800 deg. C.

  20. Development and Oxidation Resistance of B-doped Silicide Coatings on Nb-based Alloy

    International Nuclear Information System (INIS)

    Halide-activated pack cementation was utilized to deposit B-doped silicide coating. The pack powders were consisted of 3 Wt.%NH4Cl, 7 Wt.%Si, 90 Wt.%Al2O3+TiB2. B-doped silicide coating was consisted of two layers, an outer layer of NbSi2 and an inner layer of Nb5Si3. Isothermal oxidation resistance of B-doped silicide coating was tested at 1250 .deg. C in static air. B-doped silicide coating had excellent oxidation resistance, because continuous SiO2 scale which serves as obstacle of oxygen diffusion was formed after oxidation

  1. Infrared and Raman characterization of beta iron silicide

    Science.gov (United States)

    Lefki, K.; Muret, P.; Bustarret, E.; Boutarek, N.; Madar, R.; Chevrier, J.; Derrien, J.; Brunel, M.

    1991-12-01

    Samples of beta-iron silicide were prepared by three different methods : solid phase reaction on silicon (111), on a monocrystaline FeSi substrate, and from the melt. These samples have been characterized by x-ray diffraction and investigated by Infrared and Raman spectroscopies. The infrared and Raman lines are compared with theoretical predictions given by the factor group analysis of the silicide primitive cell, which yields the number and the symmetry of the different modes. We relate the red shift of the Infrared and Raman lines on samples with smaller lattice parameters to the presence of Iron vacancies in films deposited on silicon, in agreement with the sign of the thermoelectric power.

  2. Oxidation behavior of molybdenum silicides and their composites

    Energy Technology Data Exchange (ETDEWEB)

    Natesan, K.; Deevi, S. C.

    2000-04-03

    A key materials issue associated with the future of high-temperature structural silicides is the resistance of these materials to oxidation at low temperatures. Oxidation tests were conducted on Mo-based silicides over a wide temperature range to evaluate the effects of alloy composition and temperature on the protective scaling characteristics and testing regime for the materials. The study included Mo{sub 5}Si{sub 3} alloys that contained several concentrations of B. In addition, oxidation characteristics of MoSi{sub 2}-Si{sub 3}N{sub 4} composites that contained 20--80 vol.% Si{sub 3}N{sub 4} were evaluated at 500--1,400 C.

  3. Titanium-based silicide quantum dot superlattices for thermoelectrics applications.

    Science.gov (United States)

    Savelli, Guillaume; Stein, Sergio Silveira; Bernard-Granger, Guillaume; Faucherand, Pascal; Montès, Laurent; Dilhaire, Stefan; Pernot, Gilles

    2015-07-10

    Ti-based silicide quantum dot superlattices (QDSLs) are grown by reduced-pressure chemical vapor deposition. They are made of titanium-based silicide nanodots scattered in an n-doped SiGe matrix. This is the first time that such nanostructured materials have been grown in both monocrystalline and polycrystalline QDSLs. We studied their crystallographic structures and chemical properties, as well as the size and the density of the quantum dots. The thermoelectric properties of the QDSLs are measured and compared to equivalent SiGe thin films to evaluate the influence of the nanodots. Our studies revealed an increase in their thermoelectric properties-specifically, up to a trifold increase in the power factor, with a decrease in the thermal conductivity-making them very good candidates for further thermoelectric applications in cooling or energy-harvesting fields.

  4. Fracture of niobium-base silicide coated alloy

    International Nuclear Information System (INIS)

    Mechanical properties and character of fracture of Nb-W-Mo-Zr-C alloy composition with complex by composition and structure silicide coating under different states of stage-by-stage coating are studied. Structural features, character of fracture from ductile to quasibrittle transcrystalline one and, respectively, the composition plasticity level are defined by interrelation of fracture processes in coating, matrix plastic flow and possibility and way of stress relaxation on their boundary

  5. Neptunium and americium control for international non-proliferation regime

    International Nuclear Information System (INIS)

    It was decided in the IAEA Board of Governors Meeting held in Sept. 1999 that Neptunium and Americium could be diverted for manufacturing nuclear weapon or explosives, so that appropriate measures should be taken for the prevention of proliferation of these materials. It is expected to take relatively long time for settling down the aligned system dealing with the above materials because the present regulatory statement was prepared on the basis of voluntary offers from the States concerned. The necessity of preventive measures is being convinced among Member States, but it would not be easy to take voluntary participation in detail because of their respective interests. It is expected that this paper could contribute to the effective response as to the international commitments as well as for protecting the domestic nuclear industry and R and D area through analysis on the IAEA's approach on Neptunium and Americium

  6. Thermophysical properties of americium-containing barium plutonate

    International Nuclear Information System (INIS)

    Polycrystalline specimens of americium-containing barium plutonate have been prepared by mixing the appropriate amounts of (Pu0.91Am0.09)O2 and BaCO3 powders followed by reacting and sintering at 1600 K under the flowing gas atmosphere of dry-air. The sintered specimens had a single phase of orthorhombic perovskite structure and were crack-free. Elastic moduli were determined from longitudinal and shear sound velocities. Debye temperature was also determined from sound velocities and lattice parameter measurements. Thermal conductivity was calculated from measured density at room temperature, literature values of heat capacity and thermal diffusivity measured by laser flash method in vacuum. Thermal conductivity of americium-containing barium plutonate was roughly independent of temperature and registered almost the same magnitude as that of BaPuO3 and BaUO3. (author)

  7. 1976 Hanford americium-exposure incident: decontamination and treatment facility

    International Nuclear Information System (INIS)

    An injured worker, contaminated with over 6 mCi of americium-241, required special treatment and housing for 4 months. This paper is a description of the design and management of the facility in which most of the treatment and housing occurred. The problems associated with contamination control, waste handling, supplies, and radiological concerns during the two-stage transfer of the patient from a controlled situation to his normal living environment are discussed in detail

  8. Ingestion Pathway Transfer Factors for Plutonium and Americium

    Energy Technology Data Exchange (ETDEWEB)

    Blanchard, A.

    1999-07-28

    Overall transfer factors for major ingestion pathways are derived for plutonium and americium. These transfer factors relate the radionuclide concentration in a given foodstuff to deposition on the soil. Equations describing basic relationships consistent with Regulatory Guide 1.109 are followed. Updated values and coefficients from IAEA Technical Reports Series No. 364 are used when a available. Preference is given to using factors specific to the Savannah River Site.

  9. Method for removal of plutonium impurity from americium oxides and fluorides

    Science.gov (United States)

    FitzPatrick, John R.; Dunn, Jerry G.; Avens, Larry R.

    1987-01-01

    Method for removal of plutonium impurity from americium oxides and fluorides. AmF.sub.4 is not further oxidized to AmF.sub.6 by the application of O.sub.2 F at room temperature, while plutonium compounds present in the americium sample are fluorinated to volatile PuF.sub.6, which can readily be separated therefrom, leaving the purified americium oxides and/or fluorides as the solid tetrafluoride.

  10. Gut uptake factors for plutonium, americium and curium

    International Nuclear Information System (INIS)

    Data on estimates of the absorption of plutonium, americium and curium from the human gut based on measurements of uptake in other mammalian species are reviewed. It is proposed that for all adult members of the public ingesting low concentrations of plutonium in food and water, 0.05% would be an appropriate value of absorption except when the conditions of exposure are known and a lower value can be justified. For dietary intakes of americium and curium, the available data do not warrant a change from the ICRP value of 0.05%. For newborn children ingesting americium, curium and soluble forms of plutonium, a value of 1% absorption is proposed for the first 3 months of life during which the infant is maintained on a milk diet. It is proposed that a value of 0.5% should be used for the first year of life to take account of the gradual maturation of the gut. In considering the ingestion of insoluble oxides of plutonium by infants, it is proposed that absorption is taken as 0.1% for the first 3 months and 0.05% for the first year. (author)

  11. Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

    Directory of Open Access Journals (Sweden)

    Vlasova M.

    2002-01-01

    Full Text Available The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 in the mixture, silicide formation occurs also as a result of the reduction of silica by silicon and silicon carbide. The sintering of synthesized composite SiC-chromium silicides powders at a high temperature under a high pressure (T = 2073 K, P = 5 GPa is accompanied by the destruction of cc-SiC particles, the cc/3 transition in silicon carbide and deformation distortions of the lattices of chromium silicides.

  12. Mechanochemical synthesis and spark plasma sintering of the cerium silicides

    International Nuclear Information System (INIS)

    Highlights: • Ce5Si3, Ce3Si2, CeSi, CeSi2−x and CeSi2 were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce5Si3, Ce3Si2, CeSi, CeSi2−y, and CeSi2−x, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce5Si4 was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides

  13. Mechanochemical synthesis and spark plasma sintering of the cerium silicides

    Energy Technology Data Exchange (ETDEWEB)

    Alanko, Gordon A.; Jaques, Brian; Bateman, Allyssa [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Butt, Darryl P., E-mail: darrylbutt@boisestate.edu [Department of Materials Science and Engineering, College of Engineering, Boise State University, 1910 University Drive, Boise, ID 83725 (United States); Center for Advanced Energy Studies, 995 University Boulevard, Idaho Falls, ID 83401 (United States)

    2014-12-15

    Highlights: • Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−x} and CeSi{sub 2} were mechanochemically synthesized. • Temperature and pressure were monitored to investigate reaction progress. • All syntheses proceeded through a MSR event followed by rapid solid-state diffusion. • Milling time before MSR correlates well with effective heat of formation. • Some synthesized material was densified by spark plasma sintering. - Abstract: The cerium silicides, Ce{sub 5}Si{sub 3}, Ce{sub 3}Si{sub 2}, CeSi, CeSi{sub 2−y}, and CeSi{sub 2−x}, have been prepared from the elements by mechanochemical processing in a planetary ball mill. Preparation of the cerium silicide Ce{sub 5}Si{sub 4} was unsuccessfully attempted and potential reasons for this are discussed. Temperature and pressure of the milling vial were monitored in situ to gain insight into the mechanochemical reaction kinetics, which include a mechanically-induced self-propagating reaction (MSR). Some prepared powders were consolidated by spark plasma sintering to high density. Starting materials, as-milled powders, and consolidated samples were characterized by X-ray diffraction, scanning electron microscopy, and energy dispersive spectroscopy. The results obtained help elucidate key questions in mechanochemical processing of intermetallics, showing first phase formation similar to thin films, MSR ignition times that are composition- and milling speed-dependent, and sensitivity of stable compound formation on the impact pressure. The results demonstrate mechanochemical synthesis as a viable technique for rare earth silicides.

  14. Immobilization of Uranium Silicide in Sintered Iron-Phosphate Glass

    International Nuclear Information System (INIS)

    This work is a continuation of a previous one performed in vitrification of uranium silicide in borosilicate and iron-silicate glasses, by sintering.We present the results obtained with an iron-phosphate glass developed at our laboratory and we compare this results with those obtained with the above mentioned glasses. The main objective was to develop a method as simple as possible, so as to get a monolithic glass block with the appropriate properties to be disposed in a deep geological repository.The thermal transformation of the uranium silicide was characterized by DTA/TG analysis and X-ray diffraction.We determined the evolution of the crystalline phases and the change in weight.Calcined uranium silicide was mixed with natural U3O8, the amount of U3O8 was calculated to simulate an isotopic dilution of 4%.This material was mixed with powdered iron-phosphate glass (in wt.%: 64,9 P2O5; 22,7 Fe2O3; 8,1 Al2O3; 4,3 Na2O) in different proportions (in wt%): 7%, 10% y 15%.The powders were pressed and sintered at temperatures between 585 y 670 °C. Samples of the sintered pellet were prepared for the lixiviation tests (MCC-1P: monolithic samples; deionised water; 90° C; 7, 14 and 28 days).The samples showed a quite good durability (0,6 g.m-2.day-1), similar to borosilicate glasses.The microstructure of the glass samples showed that the uranium particles are much better integrated to the glass matrix in the iron-phosphate glasses than in the borosilicate or iron-silicate glasses.We can conclude that the sintered product obtained could be a good alternative for the immobilization of nuclear wastes with high content of uranium, as the ones arising from the conditioning of research reactors spent fuels

  15. Airborne plutonium-239 and americium-241 concentrations measured from the 125-meter Hanford Meteorological Tower

    International Nuclear Information System (INIS)

    Airborne plutonium-239 and americium-241 concentrations and fluxes were measured at six heights from 1.9 to 122 m on the Hanford meteorological tower. The data show that plutonium-239 was transported on nonrespirable and small particles at all heights. Airborne americium-241 concentrations on small particles were maximum at the 91 m height

  16. 10 CFR 31.8 - Americium-241 and radium-226 in the form of calibration or reference sources.

    Science.gov (United States)

    2010-01-01

    ... 10 Energy 1 2010-01-01 2010-01-01 false Americium-241 and radium-226 in the form of calibration or... BYPRODUCT MATERIAL § 31.8 Americium-241 and radium-226 in the form of calibration or reference sources. (a..., americium-241 or radium-226 in the form of calibration or reference sources: (1) Any person in a...

  17. Postirradiation analysis of experimental uranium-silicide dispersion fuel plates

    International Nuclear Information System (INIS)

    Low-enriched uranium silicide dispersion fuel plates were irradiated to maximum burnups of 96% of 235U. Fuel plates containing 33 v/o U3Si and U3Si2 behaved very well up to this burnup. Plates containing 33 v/o U3Si-Al pillowed between 90 and 96% burnup of the fissile atoms. More highly loaded U3Si-Al plates, up to 50 v/o were found to pillow at lower burnups. Plates containing 40 v/o U3Si showed an increase swelling rate around 85% burnup. 5 refs., 10 figs

  18. Uncertainty analysis of doses from ingestion of plutonium and americium.

    Science.gov (United States)

    Puncher, M; Harrison, J D

    2012-02-01

    Uncertainty analyses have been performed on the biokinetic model for americium currently used by the International Commission on Radiological Protection (ICRP), and the model for plutonium recently derived by Leggett, considering acute intakes by ingestion by adult members of the public. The analyses calculated distributions of doses per unit intake. Those parameters having the greatest impact on prospective doses were identified by sensitivity analysis; the most important were the fraction absorbed from the alimentary tract, f(1), and rates of uptake from blood to bone surfaces. Probability distributions were selected based on the observed distribution of plutonium and americium in human subjects where possible; the distributions for f(1) reflected uncertainty on the average value of this parameter for non-specified plutonium and americium compounds ingested by adult members of the public. The calculated distributions of effective doses for ingested (239)Pu and (241)Am were well described by log-normal distributions, with doses varying by around a factor of 3 above and below the central values; the distributions contain the current ICRP Publication 67 dose coefficients for ingestion of (239)Pu and (241)Am by adult members of the public. Uncertainty on f(1) values had the greatest impact on doses, particularly effective dose. It is concluded that: (1) more precise data on f(1) values would have a greater effect in reducing uncertainties on doses from ingested (239)Pu and (241)Am, than reducing uncertainty on other model parameter values and (2) the results support the dose coefficients (Sv Bq(-1) intake) derived by ICRP for ingestion of (239)Pu and (241)Am by adult members of the public.

  19. Recovery of americium-241 from aged plutonium metal

    International Nuclear Information System (INIS)

    After separation and purification, both actinides were precipitated as oxalates and calcined. A large-scale process was developed using dissolution, separation, purification, precipitation, and calcination. Efforts were made to control corrosion, to avoid product contamination, to keep the volume of process and waste solutions manageable, and to denitrate solutions with formic acid. The Multipurpose Processing Facility (MPPF), designed for recovery of transplutonium isotopes, was used for the first time for the precipitation and calcination of americium. Also, for the first time,, large-scale formic acid denitration was performed in a canyon vessel at SRP

  20. Effect of 241-americium on bone marrow stroma

    International Nuclear Information System (INIS)

    The regulation of haemopoiesis occurs via complex interactions between the stroma and the haemopoietic cells. An attempt to further clarifying the mechanisms and the exact role of the stroma in the regulation was made in a study. Results revealed that the murine bone marrow stromal cells are highly radiosensitive after injection with 241-americium and can thus be considered as a target population after internal contamination. In addition, observations are made which may be important for risk estimation for the developing animal and during pregnancy. Contamination in utero and by lactation shows persistent damage up to 1 year after contamination at an average annual dose of 5 cGy. (author)

  1. Transient and End Silicide Phase Formation in Thin Film Ni/polycrystalline-Si Reactions for Fully Silicided Gate Applications

    Energy Technology Data Exchange (ETDEWEB)

    Kittl,J.; Pawlak, M.; Torregiani, C.; Lauwers, A.; Demeurisse, C.; Vrancken, C.; Absil, P.; Biesemans, S.; Coia, C.; et. al

    2007-01-01

    The Ni/polycrystalline-Si thin film reaction was monitored by in situ x-ray diffraction during ramp annealings, obtaining a detailed view of the formation and evolution of silicide phases in stacks of interest for fully silicided gate applications. Samples consisted of Ni (30-170 nm)/polycrystalline-Si (100 nm)/SiO2 (10-30 nm) stacks deposited on (100) Si. The dominant end phase (after full silicidation) was found to be well controlled by the deposited Ni to polycrystalline-Si thickness ratio (tNi/tSi), with formation of NiSi2 ( {approx} 600 C), NiSi ( {approx} 400 C), Ni3Si2 ( {approx} 500 C), Ni2Si, Ni31Si12 ( {approx} 420 C), and Ni3Si ( {approx} 600 C) in stacks with tNi/tSi of 0.3, 0.6, 0.9, 1.2, 1.4, and 1.7, respectively. NiSi and Ni31Si12 were observed to precede formation of NiSi2 and Ni3Si, respectively, as expected for the phase sequence conventionally reported. Formation of Ni2Si was observed at early stages of the reaction. These studies revealed, in addition, the formation of transient phases that appeared and disappeared in narrow temperature ranges, competing with formation of the phases expected in the conventional phase sequence. These included the transient formation of NiSi and Ni31Si12 in stacks in which these phases are not expected to form (e.g., tNi/tSi of 1.7 and 0.9, respectively), at temperatures similar to those in which these phases normally grow.

  2. Preferential decorporation of americium by pulmonary administration of DTPA dry powder after inhalation of aged PuO2 containing americium in rats

    International Nuclear Information System (INIS)

    After inhalation of plutonium oxides containing various percentages of americium in rats, we identified an acellular transient pulmonary compartment, the epithelial lining fluid (ELF), in which a fraction of actinide oxides dissolve prior to absorption and subsequent extrapulmonary deposit. Chelation therapy is usually considered to be poorly efficient after inhalation of actinide oxides. However, in the present study, prompt pulmonary administration of diethylenetriaminepentaacetic acid (DTPA) as a dry powder led to a decrease in actinide content in ELF together with a limitation of bone and liver deposits. Because americium is more soluble than plutonium, higher amounts of americium were found in ELF, extrapulmonary tissues and urine. Our results also demonstrated that the higher efficacy of DTPA on americium compared to plutonium in ELF induced a preferential inhibition of extrapulmonary deposit and a greater urinary excretion of americium compared to plutonium. All together, our data justify the use of an early and local DTPA treatment after inhalation of plutonium oxide aerosols in which americium can be in high proportion such as in aged compounds. (authors)

  3. Nonuniformity effects in a hybrid platinum silicide imaging device

    Science.gov (United States)

    Dereniak, Eustace L.; Perry, David L.

    1992-05-01

    The objective of this project was twofold. The first objective was to characterize the Hughes Aircraft Company CRC-365 platinum silicide imaging device in a starting infrared sensor system. The CRC-365 is a hybrid 256 x 256 IR focal plane array that operates in the 3-5 micrometer thermal infrared band. A complete sensor and computer interface were built for these tests, using, plans provided by the Rome Laboratory at Hanscom AFB. Testing of the device revealed largely satisfactory performance, with notable exception in the areas of temporal response, temporal noise, and electrical crosstalk. The second objective of this research was to advance the understanding of how detector nonuniformity effects reduce the performance of sensors of this type. Notable accomplishments in this area included a complete linear analysis of corrected thermal imaging in platinum silicide sensors, a nonlinear analysis of the CRC-365's expected performance, analysis of its actual performance when operated with nonuniformity correction, and the development of a new figure of merit. It was demonstrated that the CRC-365 is capable of maintaining background-noise-limited performance over at least a 40 K target temperature range, when operated with two-point nonuniformity correction.

  4. Atomic size effects studied by transport in single silicide nanowires

    Science.gov (United States)

    Miccoli, I.; Edler, F.; Pfnür, H.; Appelfeller, S.; Dähne, M.; Holtgrewe, K.; Sanna, S.; Schmidt, W. G.; Tegenkamp, C.

    2016-03-01

    Ultrathin metallic silicide nanowires with extremely high aspect ratios can be easily grown, e.g., by deposition of rare earth elements on semiconducting surfaces. These wires play a pivotal role in fundamental research and open intriguing perspectives for CMOS applications. However, the electronic properties of these one-dimensional systems are extremely sensitive to atomic-sized defects, which easily alter the transport characteristics. In this study, we characterized comprehensively TbSi2 wires grown on Si(100) and correlated details of the atomic structure with their electrical resistivities. Scanning tunneling microscopy (STM) as well as all transport experiments were performed in situ using a four-tip STM system. The measurements are complemented by local spectroscopy and density functional theory revealing that the silicide wires are electronically decoupled from the Si template. On the basis of a quasiclassical transport model, the size effect found for the resistivity is quantitatively explained in terms of bulk and surface transport channels considering details of atomic-scale roughness. Regarding future applications the full wealth of these robust nanostructures will emerge only if wires with truly atomically sharp interfaces can be reliably grown.

  5. Work function characterization of solution-processed cobalt silicide

    Science.gov (United States)

    Shihab Ullah, Syed; Robinson, Matt; Hoey, Justin; Sky Driver, M.; Caruso, A. N.; Schulz, Douglas L.

    2012-06-01

    Cobalt silicide thin films were prepared by spin-coating liquid cyclohexasilane-based inks onto silicon substrates followed by a thermal treatment. The work function of the solution-processed Co-Si was determined by both capacitance-voltage (C-V) measurements of metal-oxide-semiconductor (MOS) structures as well as by ultraviolet photoemission spectroscopy (UPS). Variable frequency C-V of MOS structures with silicon oxide layers of variable thickness showed that solution-processed metal silicide films exhibit a work function of 4.36 eV with one Co-Si film on Si giving a UPS-derived work function of 4.80 eV. Similar work function measurements were collected for vapor-deposited MOS capacitors where Al thin films were prepared according to standard class 100 cleanroom handling techniques. In both instances, the work function values established by the electrical measurements were lower than those measured by UPS and this difference appears to be a consequence of parasitic series resistance.

  6. Kilogram-scale purification of americium by ion exchange

    Energy Technology Data Exchange (ETDEWEB)

    Wheelwright, E. J.

    1979-01-01

    Sequential anion and cation exchange processes have been used for the final purification of /sup 241/Am recovered during the reprocessing of aged plutonium metallurgical scrap. Plutonium was removed by absorption of Dowex 1, X-3.5 (30 to 50 mesh) anion exchange resin from 6.5 to 7.5 M HNO/sub 3/ feed solution. Following a water dilution to 0.75 to 1.0 M HNO/sub 3/, americium was absorbed on Dowex 50W, X-8 (50 to 100 mesh) cation exchange resion. Final purification was accomplished by elution of the absorbed band down 3 to 4 successive beds of the same resin, preloaded with Zn/sup 2 +/, with an NH/sub 4/OH buffered chelating agent. The recovery of mixed /sup 241/Am-/sup 243/Am from power reactor reprocessing waste has been demonstrated. Solvent extraction was used to recover a HNO/sub 3/ solution of mixed lanthanides and actinides from waste generated by the reprocessng of 13.5 tons of Shippingport Power Reactor blanket fuel. Sequential cation exchange band-displacement processes were then used to separate americium and curium from the lanthanides and then to separate approx. 60 g of /sup 244/Cm from 1000 g of mixed /sup 241/Am-/sup 243/Am.

  7. Analytical performance of radiochemical method for americium determination in urine

    International Nuclear Information System (INIS)

    This paper presents an analytical method developed and adapted for separation and analysis of Plutonium (Pu) isotopes and Americium (Am) in urine samples. The proposed method will attend the demand of internal exposure monitoring program for workers involved mainly with dismantling rods and radioactive smoke detectors. In this experimental procedure four steps are involved as preparation of samples, sequential radiochemical separation, preparation of the source for electroplating and quantification by alpha spectrometry. In the first stage of radiochemical separation, plutonium is conventionally isolated employing the anion exchange technique. Americium isolation is achieved sequentially by chromatographic extraction (Tru.spec column) from the load and rinse solutions coming from the anion exchange column. The 243Am tracer is added into the sample as chemical yield monitors and to correct the results improving the precision and accuracy. The mean recovery obtained is 60%, and the detection limit for 24h urine sample is 1.0 mBq L-1 in accordance with the literature. Based in the preliminary results, the method is appropriate to be used in monitoring programme of workers with a potential risk of internal contamination. (author)

  8. Development of separation techniques of americium from reprocessing solution

    International Nuclear Information System (INIS)

    Americium(Am) and neptunium(Np) finally transfer to the waste stream in the current PUREX reprocessing process. As an option, some methods have been developed to recover Am and Np from the waste stream to decrease long-term toxicity of the high level waste. The most stable valence state of Am is III, but TBP (tri-n-butyl phosphate) which is an extractant used in the PUREX reprocessing does not extract Am(III). Therefore, some special extractants have been developed to recover Am(III). However, they also extract rare-earth elements(REs), which necessitates the separation process for Am from REs. We have been developing a separation process which consists of valence control of Am to the VI state and its extraction with TBP. This process allows Am recovery from reprocessing solution and Am separation from REs simultaneously. Americium(III) is oxidized to Am(VI) by electrochemical oxidation and chemical oxidation using peroxodisulfate ammonium and silver nitrate. The latter was adopted here because the chemical oxidation reaction proceeds faster than the electrochemical method. Reaction mechanisms of oxidation and extraction were investigated. Based on the mechanisms, we found that extraction efficiency could be improved and waste generation could be minimized. (author)

  9. Monocrystalline molybdenum silicide based quantum dot superlattices grown by chemical vapor deposition

    Science.gov (United States)

    Savelli, Guillaume; Silveira Stein, Sergio; Bernard-Granger, Guillaume; Faucherand, Pascal; Montès, Laurent

    2016-09-01

    This paper presents the growth of doped monocrystalline molybdenum-silicide-based quantum dot superlattices (QDSL). This is the first time that such nanostructured materials integrating molybdenum silicide nanodots have been grown. QDSL are grown by reduced pressure chemical vapor deposition (RPCVD). We present here their crystallographic structures and chemical properties, as well as the influence of the nanostructuration on their thermal and electrical properties. Particularly, it will be shown some specific characteristics for these QDSL, such as a localization of nanodots between the layers, unlike other silicide based QDSL, an accumulation of doping atoms near the nanodots, and a strong decrease of the thermal conductivity obtained thanks to the nanostructuration.

  10. Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

    OpenAIRE

    Yuryev, V. A.; Chizh, K. V.; Chapnin, V.A.; Mironov, S.A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P.; Senkov, V. M.; Nalivaiko, O. Y.; Novikau, A. G.; Gaiduk, P. I.

    2015-01-01

    Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si$_3$N$_4$/SiO$_2$/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si...

  11. Formation and Oxidation Resistance of Silicide Coatings for Mo and Mo-Based Alloys

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The forming process of silicide coatings on pure Mo and Mo-base alloys, obtained by the gasphase deposition method, has been studied by examining the microstructure of coatings and the relationship between coating thickness and process parameters. It was shown that the growth of coatings was diffusion-controlled, the diffusion of silicon to be coated into Mo or Mo-base alloys was mainly responsible for the formation of silicide. The relationship between initial silicide thickness and oxidation resistance was also investigated, and the equation of service life of the coatings at high temperature in air is presented.

  12. Silicidation in Pd/Si thin film junction-Defect evolution and silicon surface segregation

    Energy Technology Data Exchange (ETDEWEB)

    Abhaya, S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India); Amarendra, G. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)], E-mail: amar@igcar.gov.in; Venugopal Rao, G.; Rajaraman, R.; Panigrahi, B.K.; Sastry, V.S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603102 (India)

    2007-09-25

    Depth resolved positron annihilation studies on Pd/Si thin film system have been carried out to investigate silicide phase formation and vacancy defect production induced by thermal annealing. The evolution of defect sensitive S-parameter clearly indicates the presence of divacancy defects across the interface, due to enhanced Si diffusion beyond 870 K consequent to silicide formation. Corroborative glancing incidence X-ray diffraction (GIXRD), Auger electron spectroscopy (AES) and Rutherford backscattering spectrometry (RBS) have elucidated the aspects related to silicide phase formation and Si surface segregation.

  13. Selective leaching studies of deep-sea sediments loaded with americium, neptunium and plutonium

    International Nuclear Information System (INIS)

    A series of selective leaching experiments were undertaken to investigate the solid phase speciation and distribution of americium, neptunium and plutonium which had been experimentally loaded onto different marine sediment types. The chemical leaches employed showed rather poor selectivity but certain trends were evident. Adsorption was not by ion exchange. Americium showed a preferential affinity for carbonate and plutonium for organic matter. Neptunium appeared to have no preferential affinities. Americium was sorbed by acetic acid residues (CaCO3 removed) and by unleached carbonate-rich sediments with equal efficiency. This indicates that it is able to diversify its solid phase affinity/distribution depending upon which solid phases are available. (author)

  14. Formation of interface silicides at room temperature in pulsed laser deposited Ti thin films on Si

    International Nuclear Information System (INIS)

    Interface characterization of pulsed laser deposited (PLD) Ti thin films on Si substrates using secondary ion mass spectrometry (SIMS), grazing incidence X-ray diffraction (GIXRD) and grazing incidence X-ray reflectivity (GIXRR) reveals the growth of titanium silicides (predominantly C54-TiSi2) layers at room temperature. These silicides nucleate and grow only at higher temperatures if deposited by other physical vapor deposition techniques. The films have been subjected to isothermal and isochronal annealing under vacuum with a view to enhancing interface reaction and interdiffusion. The silicide phase formation at room temperature is due to the energetic Ti species available in PLD plume. The silicides formed in PLD have exhibited high thermal stability

  15. Stress Evolution During Ni-Si Compound Formation for Fully Silicided (FUSI) Gates

    Energy Technology Data Exchange (ETDEWEB)

    Torregiani,C.; Van Bockstael, C.; Detavernier, C.; Lavoie, C.; Lauwers, A.; Maex, K.; Kittl, J.

    2007-01-01

    The stress (force) evolution during the formation of different Ni silicide phases was monitored by in situ curvature measurements, for the reaction of thin Ni films of various thicknesses with 100 nm polycrystalline-Si deposited on oxidized (1 0 0) Si substrates. The silicide phase formation was also monitored by in situ X-ray diffraction, allowing to match and interpret the stress evolution in terms of the formation of the different silicide phases. We found that stresses developed during the formation of the different silicides can be explained qualitatively in terms of the corresponding volume changes at the reacting interfaces. Furthermore, the matching between XRD and force curve reveals that the highest compressive stress is related to the formation of the Ni31Si12 phase, and that the stress formed is relaxed when the reaction is completed.

  16. Advanced Lightweight Silicide and Nitride Based Materials for Turbo-Engine Applications.

    OpenAIRE

    Drawin, S.; Justin, J.F.

    2011-01-01

    International audience Refractory metal silicides and nitride-based ceramics combine two properties that may lead to substantial reductions in aircraft fuel consumption : compared to the most advanced nickel-based superalloys presently used in aeronautical turbines, they can withstand higher temperatures and may have lower densities. Niobium silicide-based alloys and silicon nitride / molybdenum disilicide composites are currently being developed for turbine hot section components for both...

  17. SiGeHBTs on Bonded SOI Incorporating Buried Silicide Layers

    OpenAIRE

    Bain, M.; El Mubarek, H A; Bonar, J. M.; Wang, Y.; Buiu, O.; Gamble, H.; Armstrong, B M; Hemment, P L; Hall, S.; Ashburn, P.

    2005-01-01

    A technology is described for fabricating SiGe hetero-junction bipolar transistors (HBTs) on wafer-bonded silicon-on-insulator (SOI) substrates that incorporate buried tungsten silicide layers for collector resistance reduction or buried groundplanes for crosstalk suppression. The physical structure of the devices is characterized using cross section transmission electron microscopy, and the electrical properties of the buried tungsten silicide layer are characterized using sheet resistance m...

  18. SiGe HBTs on bonded SOI incorporating buried silicide layers

    OpenAIRE

    Bain, M.; El Mubarek, A. W.; Bonar, J. M.; Wang, Y.; Buiu, O.; Gamble, H.; Armstrong, B M; Hemment, P. L. F.; Hall, Steven; Ashburn, Peter

    2005-01-01

    A technology is described for fabricating SiGe heterojunction bipolar transistors (HBTs) on wafer-bonded silicon-on-insulator (SOI) substrates that incorporate buried tungsten silicide layers for collector resistance reduction or buried groundplanes for crosstalk suppression. The physical structure of the devices is characterized using cross section transmission electron microscopy, and the electrical properties of the buried tungsten silicide layer are characterized using sheet resistance me...

  19. Information for irradiation and post-irradiation of the silicide fuel element prototype P-07

    International Nuclear Information System (INIS)

    Included in the 'Silicides' Project, developed by the Nuclear Fuels Department of the National Atomic Energy Commission (CNEA), it is foreseen the qualification of this type of fuel for research reactors in order to be used in the Argentine RA-3 reactor and to confirm the CNEA as an international supplier. The paper presents basic information on several parameters corresponding to the new silicide prototype, called P-07, to be taken into account for its irradiation, postirradiation and qualification. (author)

  20. Status of the atomized uranium silicide fuel development at KAERI

    Energy Technology Data Exchange (ETDEWEB)

    Kim, C.K.; Kim, K.H.; Park, H.D.; Kuk, I.H. [Korea Atomic Energy Research Institute, Taejon (Korea, Republic of)

    1997-08-01

    While developing KMRR fuel fabrication technology an atomizing technique has been applied in order to eliminate the difficulties relating to the tough property of U{sub 3}Si and to take advantage of the rapid solidification effect of atomization. The comparison between the conventionally comminuted powder dispersion fuel and the atomized powder dispersion fuel has been made. As the result, the processes, uranium silicide powdering and heat treatment for U{sub 3}Si transformation, become simplified. The workability, the thermal conductivity and the thermal compatibility of fuel meat have been investigated and found to be improved due to the spherical shape of atomized powder. In this presentation the overall developments of atomized U{sub 3}Si dispersion fuel and the planned activities for applying the atomizing technique to the real fuel fabrication are described.

  1. Europium Silicide – a Prospective Material for Contacts with Silicon

    Science.gov (United States)

    Averyanov, Dmitry V.; Tokmachev, Andrey M.; Karateeva, Christina G.; Karateev, Igor A.; Lobanovich, Eduard F.; Prutskov, Grigory V.; Parfenov, Oleg E.; Taldenkov, Alexander N.; Vasiliev, Alexander L.; Storchak, Vyacheslav G.

    2016-05-01

    Metal-silicon junctions are crucial to the operation of semiconductor devices: aggressive scaling demands low-resistive metallic terminals to replace high-doped silicon in transistors. It suggests an efficient charge injection through a low Schottky barrier between a metal and Si. Tremendous efforts invested into engineering metal-silicon junctions reveal the major role of chemical bonding at the interface: premier contacts entail epitaxial integration of metal silicides with Si. Here we present epitaxially grown EuSi2/Si junction characterized by RHEED, XRD, transmission electron microscopy, magnetization and transport measurements. Structural perfection leads to superb conductivity and a record-low Schottky barrier with n-Si while an antiferromagnetic phase invites spin-related applications. This development opens brand-new opportunities in electronics.

  2. Capping of rare earth silicide nanowires on Si(001)

    International Nuclear Information System (INIS)

    The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along (111) lattice planes. This behavior is related to strain due to the lattice mismatch between the Si overlayer and the nanowires

  3. Capping of rare earth silicide nanowires on Si(001)

    Energy Technology Data Exchange (ETDEWEB)

    Appelfeller, Stephan; Franz, Martin; Kubicki, Milan; Dähne, Mario [Institut für Festkörperphysik, Technische Universität Berlin, 10623 Berlin (Germany); Reiß, Paul; Niermann, Tore; Lehmann, Michael [Institut für Optik und Atomare Physik, Technische Universität Berlin, 10623 Berlin (Germany); Schubert, Markus Andreas [IHP–Leibniz-Institut für innovative Mikroelektronik, 15236 Frankfurt (Oder) (Germany)

    2016-01-04

    The capping of Tb and Dy silicide nanowires grown on Si(001) was studied using scanning tunneling microscopy and cross-sectional high-resolution transmission electron microscopy. Several nanometers thick amorphous Si films deposited at room temperature allow an even capping, while the nanowires maintain their original structural properties. Subsequent recrystallization by thermal annealing leads to more compact nanowire structures and to troughs in the Si layer above the nanowires, which may even reach down to the nanowires in the case of thin Si films, as well as to V-shaped stacking faults forming along (111) lattice planes. This behavior is related to strain due to the lattice mismatch between the Si overlayer and the nanowires.

  4. Postirradiation analysis of experimental uranium-silicide dispersion fuel plates

    Energy Technology Data Exchange (ETDEWEB)

    Hofman, G.L.; Neimark, L.A.

    1985-01-01

    Low-enriched uranium silicide dispersion fuel plates were irradiated to maximum burnups of 96% of /sup 235/U. Fuel plates containing 33 v/o U/sub 3/Si and U/sub 3/Si/sub 2/ behaved very well up to this burnup. Plates containing 33 v/o U/sub 3/Si-Al pillowed between 90 and 96% burnup of the fissile atoms. More highly loaded U/sub 3/Si-Al plates, up to 50 v/o were found to pillow at lower burnups. Plates containing 40 v/o U/sub 3/Si showed an increase swelling rate around 85% burnup. 5 refs., 10 figs.

  5. Attempt to produce silicide fuel elements in Indonesia

    International Nuclear Information System (INIS)

    After the successful experiment to produce U3Si2 powder and U3Si2-Al fuel plates using depleted U and Si of semiconductor quality, silicide fuel was synthesized using x-Al available at the Fuel Element Production Installation (FEPI) at Serpong, Indonesia. Two full-size U3Si2-Al fuel elements, having similar specifications to the ones of U3O8-Al for the RSG-GAS (formerly known as MPR-30), have been produced at the FEPI. All quality controls required have been imposed to the feeds, intermediate, as well as final products throughout the production processes of the two fuel elements. The current results show that these fuel elements are qualified from fabrication point of view, therefore it is expected that they will be permitted to be tested in the RSG-GAS, sometime by the end of 1989, for normal (∝50%) and above normal burn-up. (orig.)

  6. Mechanical, elastic and thermodynamic properties of crystalline lithium silicides

    CERN Document Server

    Schwalbe, Sebastian; Trepte, Kai; Biedermann, Franziska; Mertens, Florian; Kortus, Jens

    2016-01-01

    We investigate crystalline thermodynamic stable lithium silicides phases (LixSiy) with density functional theory (DFT) and a force-field method based on modified embedded atoms (MEAM) and compare our results with experimental data. This work presents a fast and accurate framework to calculate thermodynamic properties of crystal structures with large unit cells with MEAM based on molecular dynamics (MD). Mechanical properties like the bulk modulus and the elastic constants are evaluated in addition to thermodynamic properties including the phonon density of states, the vibrational free energy and the isochoric/isobaric specific heat capacity for Li, Li12Si7, Li7Si3, Li13Si4, Li15Si4, Li21Si5, Li17Si4, Li22Si5 and Si. For a selected phase (Li13Si4) we study the effect of a temperature dependent phonon density of states and its effect on the isobaric heat capacity.

  7. Pretreatment of americium/curium solutions for vitrification

    International Nuclear Information System (INIS)

    Vitrification will be used to stabilize an americium/curium (Am/Cm) solution presently stored in F-Canyon for eventual transport to the heavy isotope programs at Oak Ridge National Laboratory. Prior to vitrification, an in-tank oxalate precipitation and a series of oxalic/nitric acid washes will be used to separate these elements and lanthanide fission products from the bulk of the uranium and metal impurities present in the solution. Pretreatment development experiments were performed to understand the behavior of the lanthanides and the metal impurities during the oxalate precipitation and properties of the precipitate slurry. The results of these experiments will be used to refine the target glass composition allowing optimization of the primary processing parameters and design of the solution transfer equipment

  8. Plutonium and americium in sediments of Lithuanian lakes

    International Nuclear Information System (INIS)

    The assessment of contribution of the global and the Chernobyl NPP (Nuclear Power Plant) accident plutonium and americium to plutonium pollution in sediments of Lithuanian lakes is presented. Theoretical evaluation of activity ratios of 238Pu/239+240Pu and 241Pu/239+240Pu in the reactor of unit 4 of the Chernobyl NPP before the accident was performed by means of the ORIGEN-ARP code from the SCALE 4.4A program package. Non-uniform distribution of radionuclides in depositions on the Lithuanian territory after nuclear weapon tests and the Chernobyl NPP accident is experimentally observed by measuring the lake sediment pollution with actinides. The activity concentration of sediments polluted with plutonium ranges from 2.0 ± 0.5 Bq/kg d.w. (dry weight) in Lake Asavelis to 14 ± 2 Bq/kg d.w. in Lake Juodis. The ratio of activity concentrations of plutonium isotopes 238Pu/239+240Pu measured by α-spectrometry in the 10-cm-thick upper layer of bottom sediment varies from 0.03 in Lake Juodis to 0.3 in Lake Zuvintas. The analysis of the ratio values shows that the deposition of the Chernobyl origin plutonium is prevailing in southern and south-western regions of Lithuania. Plutonium of nuclear weapon tests origin in sediments of lakes is observed on the whole territory of Lithuania, and it is especially distinct in central Lithuania. The americium activity due to 241Pu decay after the Chernobyl NPP accident and global depositions in bottom sediments of Lithuanian lakes has been evaluated to be from 0.9 to 5.7 Bq/kg. (author)

  9. Synthesis and design of silicide intermetallic materials. 1998 annual progress report

    Energy Technology Data Exchange (ETDEWEB)

    Petrovic, J.J.; Castro, R.G.; Butt, D.P.; Park, Y.; Vaidya, R.U.; Hollis, K.J.; Kung, H.H.

    1999-03-01

    The overall objective of this program is to develop structural silicide-based materials with optimum combinations of elevated temperature strength/creep resistance, low temperature fracture toughness, and high temperature oxidation and corrosion resistance for applications of importance to the US processing industry. A further objective is to develop silicide-based prototype industrial components. The ultimate aim of the program is to work with industry to transfer the structural silicide materials technology to the private sector in order to promote international competitiveness in the area of advanced high temperature materials and important applications in major energy-intensive US processing industries. The program presently has a number of developing industrial connections, including a CRADA with Johns Manville Corporation targeted at the area of MoSi{sub 2}-based high temperature materials and components for fiberglass melting and processing applications. The authors are also developing an interaction with the Institute of Gas Technology (IGT) to develop silicides for high temperature radiant gas burner applications, for the glass and other industries. With Combustion Technology Inc., they are developing silicide-based periscope sight tubes for the direct observation of glass melts. With Accutru International Corporation, they are developing silicide-based protective sheaths for self-verifying temperature sensors which may be used in glass furnaces and other industrial applications. The progress made on the program in this period is summarized.

  10. Synthesis of Co-silicides and fabrication of microwavepower device using MEVVA source implantation

    Institute of Scientific and Technical Information of China (English)

    张通和; 吴瑜光; 钱卫东; 刘要东; 张旭

    2002-01-01

    Co synthesis silicides with good properties were prepared using MEVVA ion implantation with flux of 25-125 mA/cm2 to does of 5×1017/cm2. The structure of the silicides was investigated using X-ray diffraction (XRD) and transmission electron microscopy (TEM). TEM analysis shows that if the ion dose is greater than 2×1017/cm2, a continuous silicide layer will be formed. The sheet resistance of Co silicide decreases with an increase in ion flux and ion dose. The formation of silicides with CoSi and CoSi2 are identified by XRD analysis. After annealing, the sheet resistance decreases further. A continuous silicide layer with a width of 90-133 nm is formed. The optimal implantation condition is that the ion flux and dose are 50 mA/cm2 and 5×1017/cm2, respectively. The optimal annealing temperature and time are 900℃ and 10 s, respectively. The ohmic contact for power microwave transistors is fabricated using Co ion implantation technique for the first time. The emitter contact resistance and noise of the transistors decrease markedly; the microwave property has been improved obviously.

  11. Kinetic parameters of transformation of americium and plutonium physicochemical forms in podsol soils

    International Nuclear Information System (INIS)

    Kinetic parameters of transformation of americium and plutonium physicochemical forms have been estimated and the prognosis of fixing and remobilization of these nuclides in podsol soils have been made on that basis in the work. (authors)

  12. Calibration procedures for in vivo sodium iodide spectrometry of plutonium and americium in the human lung

    International Nuclear Information System (INIS)

    This paper describes the calibration techniques and associated error analysis for the in vivo measurement by NaI spectrometry of heavy elements in the lung, specifically plutonium and americium. A very brief description of the instrumentation system is included

  13. Relativistic density functional theory modeling of plutonium and americium higher oxide molecules

    Science.gov (United States)

    Zaitsevskii, Andréi; Mosyagin, Nikolai S.; Titov, Anatoly V.; Kiselev, Yuri M.

    2013-07-01

    The results of electronic structure modeling of plutonium and americium higher oxide molecules (actinide oxidation states VI through VIII) by two-component relativistic density functional theory are presented. Ground-state equilibrium molecular structures, main features of charge distributions, and energetics of AnO3, AnO4, An2On (An=Pu, Am), and PuAmOn, n = 6-8, are determined. In all cases, molecular geometries of americium and mixed plutonium-americium oxides are similar to those of the corresponding plutonium compounds, though chemical bonding in americium oxides is markedly weaker. Relatively high stability of the mixed heptoxide PuAmO7 is noticed; the Pu(VIII) and especially Am(VIII) oxides are expected to be unstable.

  14. Effects of temperature dependent pre-amorphization implantation on NiPt silicide formation and thermal stability on Si(100)

    Energy Technology Data Exchange (ETDEWEB)

    Ozcan, Ahmet S.; Wall, Donald [IBM Semiconductor Research and Development Center, 2070 Route 52, Hopewell Junction, New York 12533 (United States); Jordan-Sweet, Jean; Lavoie, Christian [IBM T. J. Watson Research Center, 1101 Kitchawan Road, Yorktown Heights, New York 10598 (United States)

    2013-04-29

    Using temperature controlled Si and C ion implantation, we studied the effects of pre-amorphization implantation on NiPt alloy silicide phase formation. In situ synchrotron x-ray diffraction and resistance measurements were used to monitor phase and morphology evolution in silicide films. Results show that substrate amorphization strongly modulate the nucleation of silicide phases, regardless of implant species. However, morphological stability of the thin films is mainly enhanced by C addition, independently of the amorphization depth.

  15. Distribution of uranium, americium and plutonium in the biomass of freshwater macrophytes

    Energy Technology Data Exchange (ETDEWEB)

    Zotina, T.A.; Kalacheva, G.S.; Bolsunovsky, A.YA. [Institute of Biophysics SB RAS, Akademgorodok, Krasnoyarsk (Russian Federation)

    2010-07-01

    Accumulation of uranium ({sup 238}U), americium ({sup 241}Am) and plutonium ({sup 242}Pu) and their distribution in cell compartments and biochemical components of the biomass of aquatic plants Elodea canadensis, Ceratophyllum demersum, Myrioplyllum spicatum and aquatic moss Fontinalis antipyretica have been investigated in laboratory batch experiments. Isotopes of uranium, americium and plutonium taken up from the water by Elodea canadensis apical shoots were mainly absorbed by cell walls, plasmalemma and organelles. A small portion of isotopes (about 6-13 %) could be dissolved in cytoplasm. The major portion (76-92 %) of americium was bound to cell wall cellulose-like polysaccharides of Elodea canadensis, Myriophyllum spicatum, Ceratophyllum demersum and Fontinalis antipyretica, 8-23 % of americium activity was registered in the fraction of proteins and carbohydrates, and just a small portion (< 1%) in lipid fraction. The distribution of plutonium in the biomass fraction of Elodea was similar to that of americium. Hence, americium and plutonium had the highest affinity to cellulose-like polysaccharides in Elodea biomass. Distribution of uranium in the biomass of Elodea differed essentially from that of transuranium elements: a considerable portion of uranium was recorded in the fraction of protein and carbohydrates (51 %). From our data we can assume that uranium has higher affinity to carbohydrates than proteins. (authors)

  16. Theory of Interface States at Silicon / Transition - - Silicide Interfaces.

    Science.gov (United States)

    Lim, Hunhwa

    The Si/NiSi(,2)(111) interface is of both fundamental and techno- logical interest: From the fundamental point of view, it is the best characterized of all semiconductor/metal interfaces, with two well-determined geometries (A and B) involving nearly perfect bonding. (This is because Si and NiSi(,2) have nearly the same lattice spacing.) Consequently, a theoretical treatment of this system makes sense--as it would not for messier systems--and one can have some confidence that the theoretical predictions are relevant to experimental observa- tions. From the technological point of view, Si/NiSi(,2) is representative of the class of semiconductor/metal interfaces that are currently of greatest interest in regard to electronic devices--Si/transition -metal-silicide interfaces. The calculations of this dissertation are for the intrinsic interface states of Si/NiSi(,2)-A geometry. These calculations also provide a foundation for later studies of defects at this interface, and for studies of other related systems, such as CoSi(,2). The calculations employ empirical tight-binding Hamiltonians for both Si and NiSi(,2) (with the parameters fitted to prior calculations of the bulk band structures, which appear to be in agreement with the available experimental data on bulk Si and NiSi(,2)). They also employ Green's function techniques--in particular, the subspace Hamiltonian technique. Our principal results are the following: (1) Interface state disper- sion curves are predicted along the symmetry lines (')(GAMMA)(')M, (')M(')K and (')K(')(GAMMA) of the surface Brillouin zone. (2) A prominent band of interface states is found which disperses downward from an energy within the Si band gap to an energy below the Si valence band edge E(,(upsilon)) as the planar wavevector (')k increases from (')(GAMMA) ((')k = 0) to (')M or (')K (symmetry points at boundary of the surface Brillouin zone). This band of inter- face states should be observable. It produces a peak in the surface

  17. Effect of americium-241 on luminous bacteria. Role of peroxides

    Energy Technology Data Exchange (ETDEWEB)

    Alexandrova, M., E-mail: maka-alexandrova@rambler.r [Siberian Federal University, Svobodny 79, 660041 Krasnoyarsk (Russian Federation); Rozhko, T. [Siberian Federal University, Svobodny 79, 660041 Krasnoyarsk (Russian Federation); Vydryakova, G. [Institute of Biophysics SB RAS, Akademgorodok 50, 660036 Krasnoyarsk (Russian Federation); Kudryasheva, N. [Siberian Federal University, Svobodny 79, 660041 Krasnoyarsk (Russian Federation); Institute of Biophysics SB RAS, Akademgorodok 50, 660036 Krasnoyarsk (Russian Federation)

    2011-04-15

    The effect of americium-241 ({sup 241}Am), an alpha-emitting radionuclide of high specific activity, on luminous bacteria Photobacterium phosphoreum was studied. Traces of {sup 241}Am in nutrient media (0.16-6.67 kBq/L) suppressed the growth of bacteria, but enhanced luminescence intensity and quantum yield at room temperature. Lower temperature (4 {sup o}C) increased the time of bacterial luminescence and revealed a stage of bioluminescence inhibition after 150 h of bioluminescence registration start. The role of conditions of exposure the bacterial cells to the {sup 241}Am is discussed. The effect of {sup 241}Am on luminous bacteria was attributed to peroxide compounds generated in water solutions as secondary products of radioactive decay. Increase of peroxide concentration in {sup 241}Am solutions was demonstrated; and the similarity of {sup 241}Am and hydrogen peroxide effects on bacterial luminescence was revealed. The study provides a scientific basis for elaboration of bioluminescence-based assay to monitor radiotoxicity of alpha-emitting radionuclides in aquatic solutions. - Highlights: {yields} Am-241 in water solutions (A = 0.16-6.7 kBq/L) suppresses bacterial growth.{yields} Am-241 (A = 0.16-6.7 kBq/L) stimulate bacterial luminescence. {yields} Peroxides, secondary radiolysis products, cause increase of bacterial luminescence.

  18. High Quality Factor Platinum Silicide Microwave Kinetic Inductance Detectors

    CERN Document Server

    Szypryt, P; Ulbricht, G; Bumble, B; Meeker, S R; Bockstiegel, C; Walter, A B

    2016-01-01

    We report on the development of Microwave Kinetic Inductance Detectors (MKIDs) using platinum silicide as the sensor material. MKIDs are an emerging superconducting detector technology, capable of measuring the arrival times of single photons to better than two microseconds and their energies to around ten percent. Previously, MKIDs have been fabricated using either sub-stoichiometric titanium nitride or aluminum, but TiN suffers from spatial inhomogeneities in the superconducting critical temperature and Al has a low kinetic inductance fraction, causing low detector sensitivity. To address these issues, we have instead fabricated PtSi microresonators with superconducting critical temperatures of 944$\\pm$12~mK and high internal quality factors ($Q_i \\gtrsim 10^6$). These devices show typical quasiparticle lifetimes of $\\tau_{qp} \\approx 30$--$40~\\mu$s and spectral resolution, $R = \\lambda / \\Delta \\lambda$, of 8 at 406.6~nm. We compare PtSi MKIDs to those fabricated with TiN and detail the substantial advanta...

  19. Simulated Fission Gas Behavior in Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Mo, Kun [Argonne National Lab. (ANL), Argonne, IL (United States); Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States); Harp, Jason [Argonne National Lab. (ANL), Argonne, IL (United States)

    2016-09-15

    As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U3Si2) at LWR conditions need to be well-understood. However, existing experimental post-irradiation examination (PIE) data are limited to the research reactor conditions, which involve lower fuel temperature compared to LWR conditions. This lack of appropriate experimental data significantly affects the development of fuel performance codes that can precisely predict the microstructure evolution and property degradation at LWR conditions and therefore evaluate the qualification of U3Si2 as an AFT for LWRs. Considering the high cost, long timescale, and restrictive access of the in-pile irradiation experiments, this study aims to utilize ion irradiation to simulate the inpile behavior of the U3Si2 fuel. Both in situ TEM ion irradiation and ex situ high-energy ATLAS ion irradiation experiments were employed to simulate different types of microstructure modifications in U3Si2. Multiple PIE techniques were used or will be used to quantitatively analyze the microstructure evolution induced by ion irradiation so as to provide valuable reference for the development of fuel performance code prior to the availability of the in-pile irradiation data.

  20. Mixing of Al into uranium silicides reactor fuels

    International Nuclear Information System (INIS)

    SEM observations have shown that irradiation induced interaction of the aluminum cladding with uranium silicide reactor fuels strongly affects both fission gas and fuel swelling behaviors during fuel burn-up. The authors have used ion beam mixing, by 1.5 MeV Kr, to study this phenomena. RBS and the 27Al(p, γ) 28Si resonance nuclear reaction were used to measure radiation induced mixing of Al into U3Si and U3Si2 after irradiation at 300 C. Initially U mixes into the Al layer and Al mixes into the U3Si. At a low dose, the Al layer is converted into UAl4 type compound while near the interface the phase U(Al.93Si.07)3 grows. Under irradiation, Al diffuses out of the UAl4 surface layer, and the lower density ternary, which is stable under irradiation, is the final product. Al mixing into U3Si2 is slower than in U3Si, but after high dose irradiation the Al concentration extends much farther into the bulk. In both systems Al mixing and diffusion is controlled by phase formation and growth. The Al mixing rates into the two alloys are similar to that of Al into pure uranium where similar aluminide phases are formed

  1. Silicidation in Ni/Si thin film system investigated by X-ray diffraction and Auger electron spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Abhaya, S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Amarendra, G. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)]. E-mail: amar@igcar.gov.in; Kalavathi, S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Gopalan, Padma [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Kamruddin, M. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Tyagi, A.K. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Sastry, V.S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India); Sundar, C.S. [Materials Science Division, Indira Gandhi Centre for Atomic Research, Kalpakkam 603 102 (India)

    2007-02-15

    Silicide formation induced by thermal annealing in Ni/Si thin film system has been investigated using glancing incidence X-ray diffraction (GIXRD) and Auger electron spectroscopy (AES). Silicide formation takes place at 870 K with Ni{sub 2}Si, NiSi and NiSi{sub 2} phases co-existing with Ni. Complete conversion of intermediate silicide phases to the final NiSi{sub 2} phase takes place at 1170 K. Atomic force microscopy measurements have revealed the coalescence of pillar-like structures to ridge-like structures upon silicidation. A comparison of the experimental results in terms of the evolution of various silicide phases is presented.

  2. Anisotropic thermal expansion of Ni, Pd and Pt germanides and silicides

    Science.gov (United States)

    Geenen, F. A.; Knaepen, W.; Moens, F.; Brondeel, L.; Leenaers, A.; Van den Berghe, S.; Detavernier, C.

    2016-07-01

    Silicon or germanium-based transistors are nowadays used in direct contact with silicide or germanide crystalline alloys for semiconductor device applications. Since these compounds are formed at elevated temperatures, accurate knowledge of the thermal expansion of both substrate and the contact is important to address temperature depending effects such as thermal stress. Here we report the linear coefficients of thermal expansion of Ni-, Pd- and Pt-based mono-germanides, mono-silicides and di-metal-silicides as determined by powder-based x-ray diffraction between 300 and 1225 K. The investigated mono-metallic compounds, all sharing the MnP crystal structure, as well as Pd2Si and Pt2Si exhibit anisotropic expansion. By consequence, this anisotropic behaviour should be taken into account for evaluating the crystal unit’s cell at elevated temperatures.

  3. Role of Ti3Al/silicides on tensile properties of Timetal 834 at various temperatures

    Indian Academy of Sciences (India)

    K V Sai Srinadh; Nidhi Singh; V Singh

    2007-12-01

    Extremely fine coherent precipitates of ordered Ti3Al and relatively coarse incoherent precipitates of 2 silicide exist together in the near -titanium alloy, Timetal 834, in the dual phase matrix of primary and transformed . In order to assess the role of these precipitates, three heat treatments viz. WQ, WQ–A and WQ–OA, were given to have no precipitates, Ti3Al and silicide and only silicide precipitates in the respective conditions. Tensile properties in the above three heat treated conditions were determined at room temperature, 673 K and 873 K. It was observed that largely Ti3Al precipitates were responsible for increase in the yield strength and decrease in ductility in this alloy.

  4. Comparison of JRR-4 core neutronic performance between silicide fuel and TRIGA fuel

    International Nuclear Information System (INIS)

    Neutronic analyses on the JRR-4 core loaded with 20 wt% Low Enriched Uranium (LEU) fuels have been performed using SRAC code system. The LEU fuels studied in this work are ETR type silicide one and TRIGA one. For each type of them, parametrical analyses were done as the function of uranium loading in the fuel element to see changes of core excess reactivity, thermal neutron flux, fuel burnup and so on. From many cell and whole core calculations, following results have obtained. (a) A uranium density of 3.8 g/cm3 is a good value of the Silicide fuel for JRR-4. (b) In the case of TRIGA fuel, a uranium weight fraction of 40% to the total TRIGA fuel pin weight is one of adequate values. (c) The silicide core shows a good performance on the thermal neutron flux (d) and the TRIGA core can achieve a very high burnup. (author)

  5. Silicide Nanopowders as Low-Cost and High-Performance Thermoelectric Materials

    Science.gov (United States)

    Chen, Renkun

    2013-06-01

    Thermoelectric devices directly convert heat into electricity and are very attractive for waste heat recovery and solar energy utilization. If thermoelectric devices can be made sufficiently efficient and inexpensive, then they will become a transformative energy technology that can tap a significant portion (10-20%) of the vast amount of heat existing in nature as well as industrial processes. Nanopowders of Earth-abundant, silicide-based materials, such as Mg2Si and its alloys, provide a unique opportunity to realize this goal. This article will present an overview of recent advances in the synthesis and thermoelectric properties of silicide-based nanostructured materials.

  6. Mechanoactivation of chromium silicide formation in the SiC-Cr-Si system

    OpenAIRE

    Vlasova M.; Kakazey M.; Gonzales-Rodriguez J.G.; Dominguez G.; Ristić Momčilo M.; Scherbina O.; Tomila T.; Isaeva L.; Timofeeva I.I.; Bukov A.

    2002-01-01

    The processes of simultaneous grinding of the components of a SiC-Cr-Si mixture and further temperature treatment in the temperature range 1073-1793 K were studied by X-ray phase analysis, IR spectroscopy, electron microscopy, and X-ray microanalysis. It was established that, during grinding of the mixture, chromium silicides form. A temperature treatment completes the process. Silicide formation proceeds within the framework of the diffusion of silicon into chromium. In the presence of SiO2 ...

  7. Effect of copper on phase formation process in boron-silicide layers on niobium and tantalum

    International Nuclear Information System (INIS)

    The influence of copper additions on regularities of growth, phase- and structure formation of borosilicide coatings produced by siliconizing preliminarily borated niobium and tantalum was studied. Rolled sheets of niobium and tantalum with impurity content less than 0.02 % (mass) were used for the coating application. Copper introduction into saturating medium affects growth rate, phase- and structure formation of silicide phases on niobium and tantalum. It also permits obtaining alternating boride and silicide layers, which is probably the only way of the composition fabrication, which can be of interest, when developing coatings with preset properties

  8. Progress in alkaline peroxide dissolution of low-enriched uranium metal and silicide targets

    International Nuclear Information System (INIS)

    This paper reports recent progress on two alkaline peroxide dissolution processes: the dissolution of low-enriched uranium metal and silicide (U3Si2) targets. These processes are being developed to substitute low-enriched for high-enriched uranium in targets used for production of fission-product 9'9Mo. Issues that are addressed include (1) dissolution kinetics of silicide targets, (2) 99Mo lost during aluminum dissolution, (3) modeling of hydrogen peroxide consumption, (4) optimization of the uranium foil dissolution process, and (5) selection of uranium foil barrier materials. Future work associated with these two processes is also briefly discussed. (author)

  9. Use of silicide fuel in the Ford Nuclear Reactor - to lengthen fuel element lifetimes

    Energy Technology Data Exchange (ETDEWEB)

    Bretscher, M.M.; Snelgrove, J.L. [Argonne National Lab., IL (United States); Burn, R.R.; Lee, J.C. [Univ. of Michigan, Ann Arbor, MI (United States). Phoenix Memorial Lab.

    1995-12-31

    Based on economic considerations, it has been proposed to increase the lifetime of LEU fuel elements in the Ford Nuclear Reactor by raising the {sup 235}U plate loading from 9.3 grams in aluminide (UAl{sub x}) fuel to 12.5 grams in silicide (U{sub 3}Si{sub 2}) fuel. For a representative core configuration, preliminary neutronic depletion and steady state thermal hydraulic calculations have been performed to investigate core characteristics during the transition from an all-aluminide to an all-silicide core. This paper discusses motivations for this fuel element upgrade, results from the calculations, and conclusions.

  10. 10 CFR 32.57 - Calibration or reference sources containing americium-241 or radium-226: Requirements for license...

    Science.gov (United States)

    2010-01-01

    ... or radium-226: Requirements for license to manufacture or initially transfer. 32.57 Section 32.57... americium-241 or radium-226: Requirements for license to manufacture or initially transfer. An application... containing americium-241 or radium-226, for distribution to persons generally licensed under § 31.8 of...

  11. Separation and determination of americium in low-level alkaline waste of NPP origin

    Science.gov (United States)

    Todorov, B.; Djingova, R.; Nikiforova, A.

    2006-01-01

    The aim of this work is to develop a short and cost-saving procedure for the determination of 241Am in sludge sample of the alkaline low-level radioactive waste (LL LRAW) collected from Nuclear Power Plant “Kozloduy”. The determination of americium was a part of a complex analytical approach, where group actinide separation was achieved. An anion exchange was used for separation of americium from uranium, plutonium and iron. For the separation of americium extraction with diethylhexyl phosphoric acid (DEHPA) was studied. The final radioactive samples were prepared by micro co-precipitation with NdF3, counted by alpha and gamma spectrometry. The procedure takes 2 hours. The recovery yield of the procedure amounts to (95 ± 1.5)% and the detection limit is 53 mBq/kg 241Am (t=150 000 s). The analytical procedure was applied for actual liquid wastes and results were compared to standard procedure.

  12. Water splitting and electricity with semiconducting silicides in sunlight

    Energy Technology Data Exchange (ETDEWEB)

    Demuth, Martin [Max-Planck-Institut fuer Bioanorganische Chemie, Muelheim an der Ruhr (Germany); H2 Solar GmbH, Loerrach (Germany); Kerpen, Klaus; Kuklya, Andriy; Wuestkamp, Marc-Andre [Max-Planck-Institut fuer Kohlenforschung, Muelheim an der Ruhr (Germany)

    2010-07-01

    Generation of hydrogen and oxygen from water is described using mainly the semiconductor titanium disilicide as catalyst and halogen light which closely mimics solar radiation. The reactions are carried out under non-aerobic conditions, i.e., under nitrogen. High efficiencies are reached at 1.1-1.2 bar pressure. In the first phase of these reactions the catalytically active centers are built up. During this phase of reaction the kinetics of the water splitting process is growing in and leads to a linear dependence in the further course of the reactions which consists of >96% water splitting to yield hydrogen and oxygen in a 2:1 ratio. Hydrogen is partially and reversibly stored physically, depending on temperature. Oxygen behaves differently since it is stored entirely under the applied reaction conditions (50-80 C and light) and can be liberated from storage upon heating the slurries in the dark. This allows convenient separation of hydrogen and oxygen. The stability of titanium disilicide has been positively tested over several months. This material is abundant and inexpensive besides that it absorbs most of the solar radiation. Further, XRD and XPS studies show that titanium disilicide is 80% crystalline and the oxide formation is limited to a few molecular layers in depth. By using labeled water it was shown that labeled dioxygen appears in the gas phase of such reactions, this showing definitively that hydrogen evolution occuring here stems from photochemical splitting of water. Further, water splitting is part of a project which involves photoelectrochemistry and in which the silicides are used as light-receiving electrode and transition metal-coated anodes serve to split water. (orig.)

  13. Silicon Framework-Based Lithium Silicides at High Pressures.

    Science.gov (United States)

    Zhang, Shoutao; Wang, Yanchao; Yang, Guochun; Ma, Yanming

    2016-07-01

    The bandgap and optical properties of diamond silicon (Si) are not suitable for many advanced applications such as thin-film photovoltaic devices and light-emitting diodes. Thus, finding new Si allotropes with better bandgap and optical properties is desirable. Recently, a Si allotrope with a desirable bandgap of ∼1.3 eV was obtained by leaching Na from NaSi6 that was synthesized under high pressure [Nat. Mater. 2015, 14, 169], paving the way to finding new Si allotropes. Li is isoelectronic with Na, with a smaller atomic core and comparable electronegativity. It is unknown whether Li silicides share similar properties, but it is of considerable interest. Here, a swarm intelligence-based structural prediction is used in combination with first-principles calculations to investigate the chemical reactions between Si and Li at high pressures, where seven new compositions (LiSi4, LiSi3, LiSi2, Li2Si3, Li2Si, Li3Si, and Li4Si) become stable above 8.4 GPa. The Si-Si bonding patterns in these compounds evolve with increasing Li content sequentially from frameworks to layers, linear chains, and eventually isolated Si ions. Nearest-neighbor Si atoms, in Cmmm-structured LiSi4, form covalent open channels hosting one-dimensional Li atom chains, which have similar structural features to NaSi6. The analysis of integrated crystal orbital Hamilton populations reveals that the Si-Si interactions are mainly responsible for the structural stability. Moreover, this structure is dynamically stable even at ambient pressure. Our results are also important for understanding the structures and electronic properties of Li-Si binary compounds at high pressures. PMID:27302244

  14. Isotopic and elemental composition of plutonium/americium oxides influence pulmonary and extra-pulmonary distribution after inhalation in rats

    International Nuclear Information System (INIS)

    The biodistribution of plutonium and americium has been studied in a rat model after inhalation of two PuO2 powders in lungs and extra-pulmonary organs from 3 d to 3 mo. The main difference between the two powders was the content of americium (approximately 46% and 4.5% of total alpha activity). The PuO2 with a higher proportion of americium shows an accelerated transfer of activity from lungs to blood as compared to PuO2 with the lower americium content, illustrated by increased urinary excretion and higher bone and liver actinide retention. The total alpha activity measured reflects mostly the americium biological behavior. The activity contained in epithelial lining fluid, recovered in the acellular phase of broncho-alveolar lavages, mainly contains americium, whereas plutonium remains trapped in macrophages. Epithelial lining fluid could represent a transitional pulmonary compartment prior to translocation of actinides to the blood and subsequent deposition in extra-pulmonary retention organs. In addition, differential behaviors of plutonium and americium are also observed between the PuO2 powders with a higher dissolution rate for both plutonium and americium being obtained for the PuO2 with the highest americium content. Our results indicate that the biological behavior of plutonium and americium after translocation into blood differ two-fold: (1) for the two actinides for the same PuO2 aerosol, and (2) for the same actinide from the two different aerosols. These results highlight the importance of considering the specific behavior of each contaminant after accidental pulmonary intake when assessing extra-pulmonary deposits from the level of activity excreted in urine or for therapeutic strategy decisions. (authors)

  15. Isotopic and elemental composition of plutonium/americium oxides influence pulmonary and extra-pulmonary distribution after inhalation in rats.

    Science.gov (United States)

    Van der Meeren, A; Grémy, O

    2010-09-01

    The biodistribution of plutonium and americium has been studied in a rat model after inhalation of two PuO(2) powders in lungs and extra-pulmonary organs from 3 d to 3 mo. The main difference between the two powders was the content of americium (approximately 46% and 4.5% of total alpha activity). The PuO(2) with a higher proportion of americium shows an accelerated transfer of activity from lungs to blood as compared to PuO(2) with the lower americium content, illustrated by increased urinary excretion and higher bone and liver actinide retention. The total alpha activity measured reflects mostly the americium biological behavior. The activity contained in epithelial lining fluid, recovered in the acellular phase of broncho-alveolar lavages, mainly contains americium, whereas plutonium remains trapped in macrophages. Epithelial lining fluid could represent a transitional pulmonary compartment prior to translocation of actinides to the blood and subsequent deposition in extra-pulmonary retention organs. In addition, differential behaviors of plutonium and americium are also observed between the PuO(2) powders with a higher dissolution rate for both plutonium and americium being obtained for the PuO(2) with the highest americium content. Our results indicate that the biological behavior of plutonium and americium after translocation into blood differ two-fold: (1) for the two actinides for the same PuO(2) aerosol, and (2) for the same actinide from the two different aerosols. These results highlight the importance of considering the specific behavior of each contaminant after accidental pulmonary intake when assessing extra-pulmonary deposits from the level of activity excreted in urine or for therapeutic strategy decisions.

  16. Schottky barrier MOSFET structure with silicide source/drain on buried metal

    Institute of Scientific and Technical Information of China (English)

    Li Ding-Yu; Sun Lei; Zhang Sheng-Dong; Wang Yi; Liu Xiao-Yan; Han Ru-Qi

    2007-01-01

    In this paper, we propose a novel Schottky barrier MOSFET structure, in which the silicide source/drain is designed on the buried metal (SSDOM). The source/drain region consists of two layers of silicide materials. Two Schottky barriers are formed between the silicide layers and the silicon channel. In the device design, the top barrier is lower and the bottom is higher. The lower top contact barrier is to provide higher on-state current, and the higher bottom contact barrier to reduce the off-state current. To achieve this, ErSi is proposed for the top silicide and CoSi2 for the bottom in the n-channel case. The 50 nm n-channel SSDOM is thus simulated to analyse the performance of the SSDOM device. In the simulations, the top contact barrier is 0.2e V (for ErSi) and the bottom barrier is 0.6 eV (for CoSi2).Compared with the corresponding conventional Schottky barrier MOSFET structures (CSB), the high on-state current of the SSDOM is maintained, and the off-state current is efficiently reduced. Thus, the high drive ability (1.2 mA/μm at Vds = 1 V, Vgs = 2 V) and the high Ion/Imin ratio (106) are both achieved by applying the SSDOM structure.

  17. Core-hole effects in the x-ray-absorption spectra of transition-metal silicides

    NARCIS (Netherlands)

    WEIJS, PJW; CZYZYK, MT; VANACKER, JF; SPEIER, W; GOEDKOOP, JB; VANLEUKEN, H; HENDRIX, HJM; DEGROOT, RA; VANDERLAAN, G; BUSCHOW, KHJ; WIECH, G; FUGGLE, JC

    1990-01-01

    We report systematic differences between the shape of the Si K x-ray-absorption spectra of transition-metal silicides and broadened partial densities of Si p states. We use a variety of calculations to show that the origin of these discrepancies is the core-hole potential appropriate to the final st

  18. X-ray Emission and Absorption Studies of Silicides in Relation to their Electronic Structure

    NARCIS (Netherlands)

    Weijs, P.J.W.; Wiech, G.; Zahorowski, W.; Speier, W.; Goedkoop, J.B.; Czyzyk, Marek; Acker, J.F. van; Leuken, E. van; Groot, R.A. de; Laan, G. van der; Sarma, D.D.; Kumar, L.; Buschow, K.H.J.; Fuggle, J.C.

    1990-01-01

    The valence bands and conduction bands of about 30 transition metal silicides (of which we concentrate on 4 here) have been investigated by measurements of Si X-ray emission bandsspectra, X-ray absorption spectra near the Si K (1s) edge, photoemission spectra, and Bremsstrahlung Isochromat spectra.

  19. Carbon mediated reduction of silicon dioxide and growth of copper silicide particles in uniform width channels

    DEFF Research Database (Denmark)

    Pizzocchero, Filippo; Bøggild, Peter; Booth, Tim

    2013-01-01

    We show that surface arc-discharge deposited carbon plays a critical intermediary role in the breakdown of thermally grown oxide diffusion barriers of 90 nm on a silicon wafer at 1035°C in an Ar/H2 atmosphere, resulting in the formation of epitaxial copper silicide particles in ≈ 10 μm wide...

  20. Synthesis and characterization of silicide coating on niobium alloy produced using molten salt method

    International Nuclear Information System (INIS)

    Nb based alloys are promising structural materials for high temperature reactors due to their strength at higher temperatures. However Nb based alloys undergoes substantial oxidation at high temperatures. In order to improve its oxidation resistance property at high temperatures (>400 °C) a protective layer must be provided to avoid direct contact of the component to atmospheric oxygen. In the present work, attempts have been made to obtain silicide coatings on Nb alloy using molten salt method. In this method, deposition of silicon is a multistep process. Metallic Si produced by the subsequent reactions in the molten salt diffuses and an oxidation resistant silicide coating forms on the surface of substrate. To study the variation in the thickness of coated layer on the Nb alloy, experiments were carried out at different temperature and time periods. These silicide coated samples were characterized using optical, SEM and XRD techniques. Based on these results mechanism of silicide coating on Nb alloys has been discussed in detail. (author)

  1. Mechanical properties of niobium alloy with molybdenum-hafnium-silicide coating

    International Nuclear Information System (INIS)

    The method of bending loading permits studying mechanical characteristics (σ σ0.2 and deflection f) in the composite of niobium alloy with silicide coating on molybdenum and hafnium base. Results of mechanical characteristics are compared with microstructural peculiarities of the failure development. Criteria which determine strength and plastic properties of the composite as dependent on the structural state are established

  2. A thermodynamic assessment for synthesizing transition metal silicides by the combustion synthesis process

    International Nuclear Information System (INIS)

    Transition metal silicides have important applications in various disciplines. These include uses as interconnects in chips, as coatings, as heating elements, etc. As their uses increased, various processing techniques were adopted to produce them. These vary from chemical/physical vapor deposition, rapid thermal processing, and sputtering for thin film processing; traditional vacuum casting and powder metallurgical routes are used to produce bulk samples. In this paper, the authors are interested in those transition metal silicides which have the potential for use in the bulk form, possibly in the aerospace or other demanding applications. The primary requirements are high refractoriness, low density, high strength and good oxidation resistance. It is the oxidation resistance that makes the silicides better candidates as compared to the other intermetallics. Meschter argued that most engineering materials retain substantial strength up to 80% of their melting points. Therefore, for an operating temperature of 1500C, the melting point of the typical candidate may be 1950C, while the limit in density can be defined by the density of Ni (8.75 gn/cc). As an alterative, combustion synthesis (CS) processing may prove to be a viable route for producing these transition metal silicides. In this process, and exothermic reaction is initiated in a compact containing stoichiometric mixture of elemental powders

  3. High pressure studies on uranium and thorium silicide compounds: Experiment and theory

    DEFF Research Database (Denmark)

    Yagoubi, S.; Heathman, S.; Svane, A.;

    2013-01-01

    , for ThSi, USi and USi2, respectively. At ambient conditions, the uranium silicides crystallize in tetragonal structures (space groups: I4/mmm for USi and I41/amd for USi2), while ThSi adopts an orthorhombic structure (space group: Pbnm) (including an anharmonic analysis of the silicon). These structures...

  4. Influence of Rapid Thermal Ramp Rate on Phase Transformation of Titanium Silicides

    Energy Technology Data Exchange (ETDEWEB)

    Bailey, Glenn; Hu, Yao, Zhi; Smith, Paul Martin; Tay, Sing Pin; Thakur, Randhir; Yang, Jiting

    1999-05-03

    ULSI technology requires low resistance, stable silicides formed on small geometry lines. Titanium disilicide (TiSiz), which is the most widely used silicide for ULSI applications, exists in two crystallographic phases: the high resistance, metastable C49 phase and the low resistance, stable C54 phase. The major issue with TiSiz is the increasing thermal budget required to transform the C49 phase into the low resistance C54 phase as linewiths decrease below 0.25 pm. Annealing above 900"C to obtain this transformation often results in thermal degradation, so it is desirable to reduce the transformation temperature. The transformation temperature has been shown to be a fi.mction of many factors including microstructure, grain size, and impurities. In this paper we report an investig+ion of rapid thermal silicidation of titanium films (250, 400, and 600 A) on single crystalline silicon at temperatures from 300 to 1000"C. The ramp rates for these experiments are 5, 30, 70, and 200oC/s. The transformation temperature decreases as the ramp rate increases and as the initial film thickness increases. Scanning electron microscopy (SEM) is used to analyze the resultant film microstructure. The ramp rate influence on Ti silicidation is also investigated on polycrystalline Si lines with widths ranging from 0.27 to 3.0 pm.

  5. Adsorption-desorption characteristics of plutonium and americium with sediment particles in the estuarine environment: studies using plutonium-237 and americium-241

    International Nuclear Information System (INIS)

    The particle formation of plutonium and americium, their adsorption onto fresh water sediments and the desorption from the sediments in sea water were studied in the Laboratory under simulated river-estuary conditions, using γ-emitting plutonium-237 and americium-241. The results of the experiments show that the particle formation of plutonium depends on its valence states, on pH and on the salinity of the medium. For river water at pH4, some 25%, 20% and 30% of the added 237Pu was in particulate form, larger than 0.45 μm, for Pu (III), Pu (IV) and Pu (VI), respectively, while 65%, 90% and 50% of the respective valence states was associated with particles at pH 8. In sea water the general pattern remains similar, although Pu (VI) is more soluble in sea water owing to higher ligand concentrations for carbonate and bicarbonate complexes. The pH-dependency of particle formation of Am (III) is more steep than that of plutonium and seems to be influenced by colloidal substances occurring in the experimental media. The adsorption-desorption characteristics of plutonium and americium with the sediment in river water as well as sea water reflect the characteristics of their particle formation, being dependent upon such properties as valence states, the pH and salinity of the medium. A sewage effluent added to the media has small but measurable effects on the adsorption-desorption processes of plutonium. (author)

  6. Thermal Stability Study from Room Temperature to 1273 K (1000 °C) in Magnesium Silicide

    Science.gov (United States)

    Stefanaki, Eleni-Chrysanthi; Hatzikraniotis, Euripides; Vourlias, George; Chrissafis, Konstantinos; Kitis, George; Paraskevopoulos, Konstantinos M.; Polymeris, George S.

    2016-10-01

    Doped magnesium silicide has been identified as a promising and environmentally friendly advanced thermoelectric material in the temperature range between 500 K and 800 K (227 °C and 527 °C). Besides the plethora of magnesium silicide thermoelectric advantages, it is well known for its high sensitivity to oxidation. Oxidation is one of the primary instability mechanisms of degradation of high-temperature Mg2Si thermoelectric devices, as in the presence of O2, Mg2Si decomposes to form MgO and Si. In this work, commercial magnesium silicide in bulk form was used for thermal stability study from room temperature to 1273 K (1000 °C). Various techniques such as DTA-TG, PXRD, and FTIR have been applied. Moreover, the application of thermoluminescence (TL) as an effective and alternative probe for the study of oxidation and decomposition has been exploited. The latter provides qualitative but very helpful hints toward oxidation studies. The low-detection threshold of thermoluminescence, in conjunction with the chemical composition of the oxidation byproducts, consisting of MgO, Mg2SiO4, and SiO2, constitute two powerful motivations for further investigating its viable use as proxy for instability/decomposition studies of magnesium silicide. The partial oxidation reaction has been adopted due to the experimental fact that magnesium silicide is monitored throughout the heating temperature range of the present study. Finally, the role of silicon dioxide to the decomposition procedure, being in amorphous state and gradually crystallizing, has been highlighted for the first time in the literature. Mg2Si oxidation takes place in two steps, including a mild oxidation process with temperature threshold of 573 K (300 °C) and an abrupt one after 773 K (500 °C). Implications on the optimum operational temperature range for practical thermoelectric (TE) applications have also been briefly discussed.

  7. Cesium-137 and americium-241 distribution by granulometric fractions of soil at Azgir test site grounds

    International Nuclear Information System (INIS)

    In measurements of radionuclide specific content in surface soil layer of contaminated territories it is important to determine in what agglomerations of soil particles there is the highest radionuclide concentration. For this purpose granulometric composition of soil at Azgir test site was studied and cesium-137 and americium-241 distribution by soil fractions was researched. (author)

  8. Apparatus for fabrication of americium- beryllium neutron sources prevents capsule contamination

    Science.gov (United States)

    Mohr, W. C.; Van Loom, J. A.

    1967-01-01

    Modified gloved enclosure is used to fill a capsule with a mixture of americium and beryllium radioactive powders to seal weld the opening, and to test it for leaks. It contains a horizontal partition, vortex mixer, mounting press, welder, test vessel, and radiation shielding to prevent surface contamination.

  9. Evaluation of the readsorption of plutonium and americium in dynamic fractionations of environmental solid samples

    DEFF Research Database (Denmark)

    Petersen, Roongrat; Hou, Xiaolin; Hansen, Elo Harald

    2008-01-01

    extractions. The degree of readsorption in dynamic and conventional batch extraction systems are compared and evaluated by using a double-spiking technique. A high degree of readsorption of plutonium and americium (>75%) was observed in both systems, and they also exhibited similar distribution patterns...

  10. Effect of bone-status on retention and distribution of americium-241 in bones of small rodents

    International Nuclear Information System (INIS)

    Forced physical exercise before and after application of americium-241 resulted in only small changes in bone-structure and behaviour of the radionuclide in bone. Feeding of a low phosphorus or low calcium diet resulted in an increased excretion of americium from bone, whereby Zn-DTPA as chelating agent removed an additional fraction of the radionuclide from bone. Low calcium diet and simultaneous continuous infusion of pharmacological doses of vitamin D-hormones didn't increase the excretion of americium more than the low calcium diet alone. (orig.)

  11. Exchange reactions of plutonium with silicides and estimation of the enthalpy of the formation of Pu5Si3

    International Nuclear Information System (INIS)

    An approximate ΔHof,298 value has been determined for Pu5Si3 through a study of exchange reactions of selected metal silicides with plutonium. The reactions were carried out by arc-melting. Results show that Pu5Si3 is intermediate in stability between V3Si and Mo3Si, and has a ΔHof,298 of -52±13 kJ/g-atom. Estimates of ΔHof,298 for the higher plutonium silicides are: Pu3Si2 -54, PuSi -60, Pu3Si5 -58, and PuSi2 -56 kJ/g-atom with uncertainties of ±18 kJ/g-atom. The plutonium silicides are found to be more stable than both the thorium and uranium silicides. (orig.)

  12. Impact of silicide layer on single photon avalanche diodes in a 130 nm CMOS process

    Science.gov (United States)

    Cheng, Zeng; Palubiak, Darek; Zheng, Xiaoqing; Deen, M. Jamal; Peng, Hao

    2016-09-01

    Single photon avalanche diode (SPAD) is an attractive solid-state optical detector that offers ultra-high photon sensitivity (down to the single photon level), high speed (sub-nanosecond dead time) and good timing performance (less than 100 ps). In this work, the impact of the silicide layer on SPAD’s characteristics, including the breakdown voltage, dark count rate (DCR), after-pulsing probability and photon detection efficiency (PDE) is investigated. For this purpose, two sets of SPAD structures in a standard 130 nm complementary metal oxide semiconductor (CMOS) process are designed, fabricated, measured and compared. A factor of 4.5 (minimum) in DCR reduction, and 5 in PDE improvements are observed when the silicide layer is removed from the SPAD structure. However, the after-pulsing probability of the SPAD without silicide layer is two times higher than its counterpart with silicide. The reasons for these changes will be discussed.

  13. Interaction and diffusion transport of americium in soils

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez-Guinart, Oriol; Rigol, Anna; Vidal, Miquel [Analytical Chemistry department, Faculty of Chemistry, University of Barcelona, Marti i Franques 1-11, 08028, Barcelona (Spain)

    2014-07-01

    The final disposal of High Level Radioactive Wastes (HLRW) is based on its long-term storage in underground facilities located in geological stable sites with a multi-barrier system, the so called Deep Geological Repositories (DGR), that will keep HLRW confined for >10.000 years. After this period of time, leachates rich in long-live radioisotopes might escape from DGR and start to transport towards the biosphere. There is still a lack of information concerning the interaction and transport in soils of some radionuclides present in HLRW, especially for radionuclides that present a high sorption, such as americium (Am). Having reliable information about the mobility of radionuclides in soils is crucial in order to develop risk assessment models and to take proper decisions in case of soil contamination. The aim of the present work was, by means of laboratory scale experiments, to study the interaction and, for first time, to evaluate the diffusion transport of {sup 241}Am in soils. The {sup 241}Am interaction in soils was assessed by applying sorption batch assays to 20 soil samples with contrasted edaphic properties which allowed us to quantify the solid-liquid distribution coefficient (K{sub d}) and desorption percentage. K{sub d} (Am) values ranged from 10{sup 3} to 10{sup 5} L kg{sup -1} and desorption percentages were always less than 2% which denoted a high capacity of the soil to incorporate the Am and a low reversibility of the sorption process. The influence of soil properties in {sup 241}Am interaction was studied by means of multiple linear and multivariate regressions. Although a single correlation between K{sub d} (Am) values and a soil property was not found, the main properties affecting {sup 241}Am interaction in soils were soil pH, carbonate and organic matter contents in the soil. Finally, additional batch assays at different controlled pH were done to study Am sorption as a function of the contact solution pH. A variation of the Am sorption

  14. SKIN DOSIMETRY IN CONDITIONS OF ITS CONSTANT SURFACE CONTAMINATION WITH SOLUTIONS OF PLUTONIUM-239 AND AMERICIUM-241

    Directory of Open Access Journals (Sweden)

    E. B. Ershov

    2012-01-01

    Full Text Available The article considers, on the basis of experimental data, the issue of assessing dose burdens to the skin basal layer in conditions of its permanent contamination with solutions of plutonium-239 and americium-241 and subsequent decontamination.

  15. Influence of biofilms on migration of uranium, americium and europium in the environment; Einfluss von Biofilmen auf das Migrationsverhalten von Uran, Americium und Europium in der Umwelt

    Energy Technology Data Exchange (ETDEWEB)

    Baumann, Nils; Zirnstein, Isabel; Arnold, Thuro

    2015-07-01

    The report on the influence of biofilms on migration of uranium, americium and europium in the environment deals with the contamination problems of uranium mines such as SDAG WISMUT in Saxonia and Thuringia. In mine waters microorganisms form a complex microbiological biocoenosis in spite of low pH values and high heavy metal concentrations including high uranium concentrations. The analyses used microbiological methods like confocal laser scanning microscopy and molecular-biological techniques. The interactions of microorganism with fluorescent radioactive heavy metal ions were performed with TRLFS (time resolved laser-induced fluorescence spectroscopy).

  16. Photoluminescence from neodymium silicide thin films formed by MEVVA ion source

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    Neodymium silicides were synthesized by Nd ion implanted into Si substrates with the aid of a metal vaporvacuum arc (MEVVA) ion source. The blender of Nd5Si4 and NdSi2was formed in a neodymium-implanted silicon thinfilm during the as-implanted state, but there was only single neodymium silicide compound in the post-annealed state,and the phase changed from NdSi2 to Nd5Si4 with increasing annealing temperature. The blue-violetluminescence excited by ultra-violet was observed at the room temperature (RT), and the intensity of photoluminescence(PL) increased with increasing the neodymium ion fluence. Moreover,the photoluminescence was closely dependent onthe temperature of rapid thermal annealing (RTA). A mechanism ofphotoluminescence was discussed.

  17. Development of fused slurry silicide coatings for tantalum reentry heat shields

    Science.gov (United States)

    Warnock, R. V.; Stetson, A. R.

    1972-01-01

    A fused slurry silicide coating was developed to provide atmospheric reentry protection for the 90Ta-lOW alloy. Overlaying the silicide with a highly refractory glass greatly improved total lifetime and reliability of the coating system. Low pressure, slow cycle lifetimes in excess of 100 cycles were consistently recorded for 1700 K - 13 and 1300 N/sq m test conditions. A minimum of 25 cycles was obtained for 1810 K - 1300 N/sq m conditions. About 50 simulated reentry cycles (variable temperature, pressure, and stress) were endured by coated 1-inch miniature heat shield panels when exposed to a maximum of 1700 K and either internal or external pressure conditions.

  18. Development of a fused slurry silicide coating for the protection of tantalum alloys

    Science.gov (United States)

    Packer, C. M.; Perkins, R. A.

    1974-01-01

    Results are reported of a research program to develop a reliable high-performance, fused slurry silicide protective coating for a tantalum-10 tungsten alloy for use at 1427 to 1538 C at 0.1 to 10 torr air pressure under cyclic temperature conditions. A review of silicide coating performance under these conditions indicated that the primary wear-out mode is associated with widening of hairline fissures in the coating. Consideration has been given to modifying the oxidation products that form on the coating surface to provide a seal for these fissures and to minimize their widening. On the basis of an analysis of the phase relationships between silica and various other oxides, a coating having the slurry composition 2.5Mn-33Ti-64.5Si was developed that is effective in the pressure range from 1 to 10 torr.

  19. RA-3 reactor core with uranium silicide fuel elements P-07 type

    International Nuclear Information System (INIS)

    Following the studies on the utilization of fuel elements (FE) containing uranium silicide, core of the RA-3 was analyzed with several calculation models. At first, the present situation, i.e. the core charged with normal FE (U3O8), has been analyzed to validate the simulation methodology comparing with experimental results and to establish reference data to 5 and 10 MW able to be compared with future new situations. Also, CITVAP's nuclear data libraries to be used in irradiation experiment planning were completed. The results were satisfactory and were applied to the study of the core containing P-07 FE [U3Si2], in face of a future core change. Comparing with the performance of the U3O8FE, the silicides ones show the following advantages: - average burnup: 45 % greater; -extraction burnup increase 12 %; and, -the residence time [in full power days] could be a 117 % greater. (author)

  20. Mössbauer spectroscopy study of surfactant sputtering induced Fe silicide formation on a Si surface

    Science.gov (United States)

    Beckmann, C.; Zhang, K.; Hofsäss, H.; Brüsewitz, C.; Vetter, U.; Bharuth-Ram, K.

    2015-12-01

    The formation of Fe silicides in surface ripple patterns, generated by erosion of a Si surface with keV Ar and Xe ions and simultaneous co-deposition of Fe, was investigated with conversion electron Mössbauer spectroscopy, atomic force microscopy and Rutherford backscattering spectrometry. For the dot and ripple patterns studied, we find an average Fe concentration in the irradiated layer between 6 and 25 at.%. The Mössbauer spectra clearly show evidence of the formation of Fe disilicides with Fe content close to 33 at.%, but very little evidence of the formation of metallic Fe particles. The results support the process of ion-induced phase separation toward an amorphous Fe disilicide phase as pattern generation mechanism. The observed amorphous phase is in agreement with thermodynamic calculations of amorphous Fe silicides.

  1. Liquid-liquid extraction separation and sequential determination of plutonium and americium in environmental samples by alpha-spectrometry

    International Nuclear Information System (INIS)

    A procedure is described by which plutonium and americium can be determined in environmental samples. The sample is leached with nitric acid and hydrogen peroxide, and the two elements are co-precipitated with ferric hydroxide and calcium oxalate. The calcium oxalate is incinerated at 4500 and the ash is dissolved in nitric acid. Plutonium is extracted with tri-n-octylamine solution in xylene from 4M nitric acid and stripped with ammonium iodide/hydrochloric acid. Americium is extracted with thenoyltrifluoroacetone solution in xylene at pH 4 together with rare-earth elements and stripped with 1M nitric acid. Americium and the rare-earth elements thus separated are sorbed on Dowex 1 x 4 resin from 1M nitric acid in 93% methanol, the rare-earth elements are eluted with 0.1M hydrochloric acid/0.5M ammonium thiocyanate/80% methanol and the americium is finally eluted with 1.5M hydrochloric acid in 86% methanol. Plutonium and americium in each fraction are electro-deposited and determined by alpha-spectrometry. Overall average recoveries are 81% for plutonium and 59% for americium. (author)

  2. Behavior of silicon in nitric media. Application to uranium silicides fuels reprocessing

    International Nuclear Information System (INIS)

    Uranium silicides are used in some research reactors. Reprocessing them is a solution for their cycle end. A list of reprocessing scenarios has been set the most realistic being a nitric dissolution close to the classic spent fuel reprocessing. This uranium silicide fuel contains a lot of silicon and few things are known about polymerization of silicic acid in concentrated nitric acid. The study of this polymerization allows to point out the main parameters: acidity, temperature, silicon concentration. The presence of aluminum seems to speed up heavily the polymerization. It has been impossible to find an analytical technique smart and fast enough to characterize the first steps of silicic acid polymerization. However the action of silicic species on emulsions stabilization formed by mixing them with an organic phase containing TBP has been studied, Silicon slows down the phase separation by means of oligomeric species forming complex with TBP. The existence of these intermediate species is short and heating can avoid any stabilization. When non irradiated uranium silicide fuel is attacked by a nitric solution, aluminum and uranium are quickly dissolved whereas silicon mainly stands in solid state. That builds a gangue of hydrated silica around the uranium silicide particulates without preventing uranium dissolution. A small part of silicon passes into the solution and polymerize towards the highly poly-condensed forms, just 2% of initial silicon is still in molecular form at the end of the dissolution. A thermal treatment of the fuel element, by forming inter-metallic phases U-Al-Si, allows the whole silicon to pass into the solution and next to precipitate. The behavior of silicon in spent fuels should be between these two situations. (author)

  3. Silicide Coating Fabricated by HAPC/SAPS Combination to Protect Niobium Alloy from Oxidation.

    Science.gov (United States)

    Sun, Jia; Fu, Qian-Gang; Guo, Li-Ping; Wang, Lu

    2016-06-22

    A combined silicide coating, including inner NbSi2 layer and outer MoSi2 layer, was fabricated through a two-step method. The NbSi2 was deposited on niobium alloy by halide activated pack cementation (HAPC) in the first step. Then, supersonic atmospheric plasma spray (SAPS) was applied to obtain the outer MoSi2 layer, forming a combined silicide coating. Results show that the combined coating possessed a compact structure. The phase constitution of the combined coating prepared by HAPC and SAPS was NbSi2 and MoSi2, respectively. The adhesion strength of the combined coating increased nearly two times than that for single sprayed coating, attributing to the rougher surface of the HAPC-bond layer whose roughness increased about three times than that of the grit-blast substrate. After exposure at 1200 °C in air, the mass increasing rate for single HAPC-silicide coating was 3.5 mg/cm(2) because of the pest oxidation of niobium alloy, whereas the combined coating displayed better oxidation resistance with a mass gain of only 1.2 mg/cm(2). Even more, the combined coating could significantly improve the antioxidation ability of niobium based alloy at 1500 °C. The good oxidation resistance of the combined silicide coating was attributed to the integrity of the combined coating and the continuous SiO2 protective scale provided by the oxidation of MoSi2. PMID:27243944

  4. Calculation of xenon 135 poisoning reactivity of RSG-GAS silicide fuelled

    International Nuclear Information System (INIS)

    Calculation of xenon 135 poisoning reactivity of RSG-GAS silicide fuelled. One of the important reactivity effects during reactor operation is a xenon poisoning, the reactivity depends on the power and time operation of reactor. The calculation was performed for RSG-GAS oxide 2,96 gr U/cc, silicide 2,96 gr U/cc silicide 3,55 gr U/cc fuelled using Xen Sam code, that is the xen sam code reform. In Xen Sam code, the xenon concentration is obtained by solving the simultaneous differential equation by means of limit different method. The results showed that the calculation values are close to the experiments. The equilibrium xenon reactivity will be higher if there is the increasing in the uranium density, while there is no significant change in the peak of xenon and dead time of the reactor. It shown that there is no influence in xenon reactivity for the same power levels and operation time more than 50 hours. At the other hand, if the operation time lest than 50 hours, there will be influences in equilibrium xenon reactivity, peak xenon and dead time reactor. For different power levels with the same operation time will be a significant influence to the xenon reactivity

  5. Palladium silicide formation under the influence of nitrogen and oxygen impurities

    Science.gov (United States)

    Ho, K. T.; Lien, C.-D.; Nicolet, M.-A.

    1985-01-01

    The effect of impurities on the growth of the Pd2Si layer upon thermal annealing of a Pd film on 100 line-type and amorphous Si substrates is investigated. Nitrogen and oxygen impurities are introduced into either Pd or Si which are subsequently annealed to form Pd2Si. The complementary techniques of Rutherford backscattering spectrometry, and N-15(p, alpha)C-12 or O-18(p, alpha)N-15 nuclear reaction, are used to investigate the behavior of nitrogen or oxygen and the alterations each creates during silicide formation. Both nitrogen and oxygen retard the silicide growth rate if initially present in Si. When they are initially in Pd, there is no significant retardation; instead, an interesting snow-plowing effect of N or O by the reaction interface of Pd2Si is observed. By using N implanted into Si as a marker, Pd and Si appear to trade roles as the moving species when the silicide front reaches the nitrogen-rich region.

  6. Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

    Energy Technology Data Exchange (ETDEWEB)

    Yuryev, V. A., E-mail: vyuryev@kapella.gpi.ru; Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P. [A. M. Prokhorov General Physics Institute of the Russian Academy of Sciences, 38 Vavilov Street, Moscow 119991 (Russian Federation); Senkov, V. M. [P. N. Lebedev Physical Institute of the Russian Academy of Sciences, 53 Leninskiy Avenue, Moscow 119991 (Russian Federation); Nalivaiko, O. Y. [JSC “Integral” – “Integral” Holding Management Company, 121A, Kazintsa I. P. Street, Minsk 220108 (Belarus); Novikau, A. G.; Gaiduk, P. I. [Belarusian State University, 4 Nezavisimosti Avenue, 220030 Minsk (Belarus)

    2015-05-28

    Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si{sub 3}N{sub 4}/SiO{sub 2}/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy. Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about −2%/ °C in the temperature interval from 25 to 50 °C.

  7. Pt silicide/poly-Si Schottky diodes as temperature sensors for bolometers

    Science.gov (United States)

    Yuryev, V. A.; Chizh, K. V.; Chapnin, V. A.; Mironov, S. A.; Dubkov, V. P.; Uvarov, O. V.; Kalinushkin, V. P.; Senkov, V. M.; Nalivaiko, O. Y.; Novikau, A. G.; Gaiduk, P. I.

    2015-05-01

    Platinum silicide Schottky diodes formed on films of polycrystalline Si doped by phosphorus are demonstrated to be efficient and manufacturable CMOS-compatible temperature sensors for microbolometer detectors of radiation. Thin-film platinum silicide/poly-Si diodes have been produced by a CMOS-compatible process on artificial Si3N4/SiO2/Si(001) substrates simulating the bolometer cells. Layer structure and phase composition of the original Pt/poly-Si films and the Pt silicide/poly-Si films synthesized by a low-temperature process have been studied by means of the scanning transmission electron microscopy; they have also been explored by means of the two-wavelength X-ray structural phase analysis and the X-ray photoelectron spectroscopy. Temperature coefficient of voltage for the forward current of a single diode is shown to reach the value of about -2%/ °C in the temperature interval from 25 to 50 °C.

  8. Influence of environmental factors on the gastrointestinal absorption of plutonium and americium

    International Nuclear Information System (INIS)

    The absorption of plutonium and americium from the gastrointestinal tract was studied, using adult hamsters and rabbits. Both actinides were administered as inorganic compounds, as organic complexes with naturally occurring chelating agents, and in a biologically incorporated form in liver tissues. The absorption of the tetravalent and hexavalent forms of plutonium were compared and the effect of protracted administration at very low concentrations was investigated. In addition, plutonium uptake from contaminated sediments and grass, collected near a nuclear-fuel reprocessing plant, was measured. The results of these studies suggest that chronic exposure of man to plutonium and americium in food and water will not lead to any substantial increase in their gastrointestinal absorption above the values currently recommended by the International Commission on Radiological Protection to define the occupational exposure of workers

  9. Electrodeposition of americium on a liquid cadmium cathode from a molten salt bath

    International Nuclear Information System (INIS)

    A high-activity experiment involving the electrode position of americium on a liquid cadmium cathode from a LiCl-KCl eutectic with about 3 g of AmO2 was conducted in a shielded cell in the ATALANTE complex. After describing the electrolyzer and the experimental conditions, the authors discuss the preparation of the LiCl-KCl-AmCl3 solution and briefly review its electrochemical properties. It was clearly confirmed that Am(III) reduction on an inert solid cathode occurs in two steps forming Am(II) before Am(0), whereas only one reduction step was observed on liquid cadmium. The main results of this study concern americium electrode position on the liquid cadmium cathode (recovery yields, current densities, problems encountered). The solvent properties of cadmium for actinide/lanthanide separation are discussed. (authors)

  10. Analysis of americium-beryllium neutron source composition using the FRAM code

    Energy Technology Data Exchange (ETDEWEB)

    Hypes, P. A. (Philip A.); Bracken, D. S. (David S.); Sampson, Thomas E.; Taylor, W. A. (Wayne A.)

    2002-01-01

    The FRAM code was originally developed to analyze high-resolution gamma spectra from plutonium items. Its capabilities have since been expanded to include analysis of uranium spectra. The flexibility of the software also enables a capable spectroscopist to use FRAM to analyze spectra in which neither plutonium nor uranium is present in significant amounts. This paper documents the use of FRAM to determine the {sup 239}Pu/{sup 241}Am, {sup 243}Am/{sup 241}Am, {sup 237}Np/{sup 241}Am, and {sup 239}Np/{sup 241}Am ratios in americium-beryllium neutron sources. The effective specific power of each neutron source was calculated from the ratios determined by FRAM in order to determine the americium mass of each of these neutron sources using calorimetric assay. We will also discuss the use of FRAM for the general case of isotopic analysis of nonplutonium, nonuranium items.

  11. Experimental Insight into the Radiation Resistance of Zirconia-Based Americium Ceramics

    International Nuclear Information System (INIS)

    Our works shows that the americium pyrochlore 241Am2Zr2O7 undergoes a phase transition to a defect-fluorite structure along with an unusual volume contraction when subjected to internal radiation from α-emitting actinides. Disorder relaxation proceeds through the simultaneous formation of cation anti sites and oxygen Frenkel pairs. X-ray absorption spectroscopy at the Am-LII and the Zr-K edges reveals that Am-O polyhedra show an increasing disorder with increasing exposure. In contrast, the Zr-O polyhedral units remain highly ordered, while rotating along edges and corners, thereby reducing the structural strain imposed by the growing disorder around americium. We believe it is this particular property of the compound that provides the remarkable resistance to radiation (≥9.4 * 1018) α-decay events g-1 or 0.80 dpa). (authors)

  12. Standard test method for quantitative determination of americium 241 in plutonium by Gamma-Ray spectrometry

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    1994-01-01

    1.1 This test method covers the quantitative determination of americium 241 by gamma-ray spectrometry in plutonium nitrate solution samples that do not contain significant amounts of radioactive fission products or other high specific activity gamma-ray emitters. 1.2 This test method can be used to determine the americium 241 in samples of plutonium metal, oxide and other solid forms, when the solid is appropriately sampled and dissolved. 1.3 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  13. Calcium and zinc DTPA administration for internal contamination with plutonium-238 and americium-241.

    Science.gov (United States)

    Kazzi, Ziad N; Heyl, Alexander; Ruprecht, Johann

    2012-08-01

    The accidental or intentional release of plutonium or americium can cause acute and long term adverse health effects if they enter the human body by ingestion, inhalation, or injection. These effects can be prevented by rapid removal of these radionuclides by chelators such as calcium or zinc diethylenetriaminepentaacetate (calcium or zinc DTPA). These compounds have been shown to be efficacious in enhancing the elimination of members of the actinide family particularly plutonium and americium when administered intravenously or by nebulizer. The efficacy and adverse effects profile depend on several factors that include the route of internalization of the actinide, the type, and route time of administration of the chelator, and whether the calcium or zinc salt of DTPA is used. Current and future research efforts should be directed at overcoming limitations associated with the use of these complex drugs by using innovative methods that can enhance their structural and therapeutic properties.

  14. Final Radiological Assessment of External Exposure for CLEAR-Line Americium Recovery Operations

    Energy Technology Data Exchange (ETDEWEB)

    Davis, Adam C. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Belooussova, Olga N. [Los Alamos National Lab. (LANL), Los Alamos, NM (United States); Hetrick, Lucas Duane [Los Alamos National Lab. (LANL), Los Alamos, NM (United States)

    2014-11-12

    Los Alamos National Laboratory is currently planning to implement an americium recovery program. The americium, ordinarily isotopically pure 241Am, would be extracted from existing Pu materials, converted to an oxide and shipped to support fabrication of americium oxide-beryllium neutron sources. These operations would occur in the currently proposed Chloride Extraction and Actinide Recovery (CLEAR) line of glove boxes. This glove box line would be collocated with the currently-operational Experimental Chloride Extraction Line (EXCEL). The focus of this document is to provide an in-depth assessment of the currently planned radiation protection measures and to determine whether or not further design work is required to satisfy design-goal and ALARA requirements. Further, this document presents a history of americium recovery operations in the Department of Energy and high-level descriptions of the CLEAR line operations to provide a basis of comparison. Under the working assumptions adopted by this study, it was found that the evaluated design appears to mitigate doses to a level that satisfies the ALARA-in-design requirements of 10 CFR 835 as implemented by the Los Alamos National Laboratory procedure P121. The analyses indicate that extremity doses would also meet design requirements. Dose-rate calculations were performed using the radiation transport code MCNP5 and doses were estimated using a time-motion study developed in consort with the subject matter expert. A copy of this report and all supporting documentation are located on the Radiological Engineering server at Y:\\Rad Engineering\\2013 PROJECTS\\TA-55 Clear Line.

  15. Bidentate organophosphorus extraction of americium and plutonium from Hanford Plutonium Reclamation Facility waste

    Energy Technology Data Exchange (ETDEWEB)

    Schulz, W.W.

    1974-09-01

    Applicability of bidentate organiphosphorus reagents to recovery of americium and plutonium from Hanford's Plutonium Reclamation Facility acid (approx. 2M HNO/sub 3/) waste stream (CAW solution) was studied. A solvent extraction process which employs a 30% DHDECMP (dihexyl-N, N-diethylcarbamylmethylene phosphonate)-CCl/sub 4/ extractant was devised and successfully tested in mixer-settler runs with actual CAW solution. Substitution of DHDECMP for DBBP eliminates the need to perform careful neutralization of unbuffered CAW soluton and increases overall americium recovery from the present 60 to 80% level to greater than or equal to 90%. Disadvantages to such substitution include the high cost (approx. $50/liter) of DHDECMP and the need to purify it (by acid (6M HCl) hydrolysis and alkaline washing) from small amounts of an unidentified impurity which prevents stripping of americium with dilute HNO/sub 3/. Distribution data obtained in this study confirm Siddall's earlier contention that bidentate organophosphorus regents can be used to remove actinides from concentrated high-level Purex process acid waste; a conceptual flowsheet for such an extraction process is given.

  16. Local solid phase growth of few-layer graphene on silicon carbide from nickel silicide supersaturated with carbon

    Energy Technology Data Exchange (ETDEWEB)

    Escobedo-Cousin, Enrique; Vassilevski, Konstantin; Hopf, Toby; Wright, Nick; O' Neill, Anthony; Horsfall, Alton; Goss, Jonathan [School of Electrical and Electronic Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom); Cumpson, Peter [School of Mechanical and Systems Engineering, Newcastle University, Newcastle upon Tyne NE1 7RU (United Kingdom)

    2013-03-21

    Patterned few-layer graphene (FLG) films were obtained by local solid phase growth from nickel silicide supersaturated with carbon, following a fabrication scheme, which allows the formation of self-aligned ohmic contacts on FLG and is compatible with conventional SiC device processing methods. The process was realised by the deposition and patterning of thin Ni films on semi-insulating 6H-SiC wafers followed by annealing and the selective removal of the resulting nickel silicide by wet chemistry. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) were used to confirm both the formation and subsequent removal of nickel silicide. The impact of process parameters such as the thickness of the initial Ni layer, annealing temperature, and cooling rates on the FLG films was assessed by Raman spectroscopy, XPS, and atomic force microscopy. The thickness of the final FLG film estimated from the Raman spectra varied from 1 to 4 monolayers for initial Ni layers between 3 and 20 nm thick. Self-aligned contacts were formed on these patterned films by contact photolithography and wet etching of nickel silicide, which enabled the fabrication of test structures to measure the carrier concentration and mobility in the FLG films. A simple model of diffusion-driven solid phase chemical reaction was used to explain formation of the FLG film at the interface between nickel silicide and silicon carbide.

  17. A two-step annealing process for Ni silicide formation in an ultra-thin body RF SOI MOSFET

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Chang-Geun [Nano-Bio Electric Devices Team, IT Convergence Technology Research Division, ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon 305-350 (Korea, Republic of)], E-mail: cgahn@etri.re.kr; Kim, Tae-Youb; Yang, Jong-Heon; Baek, In-Bok [Nano-Bio Electric Devices Team, IT Convergence Technology Research Division, ETRI, 161 Gajeong-dong, Yuseong-gu, Daejeon 305-350 (Korea, Republic of); Cho, Won-ju [Department of Electronic Materials Engineering, Kwangwoon University, Seoul 139-701 (Korea, Republic of); Lee, Seongjae [Quantum Photonic Science Research Center and BK21 Program Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791 (Korea, Republic of)

    2008-02-15

    A two-step annealing process for Ni silicide formation in an ultra-thin body (UTB) RF SOI MOSFET is proposed to prevent a dramatic increase of the gate leakage current from the in-diffusion of Ni into the channel. The first step of the annealing process was performed at a low temperature for di-nickel silicide (Ni{sub 2}Si) formation, resulting in no in-diffusion of Ni into the channel. Next, the second step of the annealing process was performed at 500 deg. C for the formation of mono-nickel silicide (NiSi). Finally, the optimized Ni silicide SD with low resistance (5 {omega}/{open_square}) and a low leakage current was achieved on the UTB. Using the proposed two-step silicide process, UTB RF MOSFET with a gate length of 50 nm a 20-nm UTB was successfully fabricated and showed the good RF properties with a cut-off frequency of 138 GHz.

  18. The new ternary silicide Gd5CoSi2: Structural, magnetic and magnetocaloric properties

    International Nuclear Information System (INIS)

    Gd5CoSi2 was prepared by annealing at 1003 K. Its investigation by the X-ray powder diffraction shows that the ternary silicide crystallizes in a tetragonal structure deriving from the Cr5B3-type (I4/mcm space group; a=7.5799(4) and c=13.5091(12) A as unit cell parameters). The Rietveld refinement shows a mixed occupancy on the (8h) site between Si and Co atoms. Magnetization and specific heat measurements performed on Gd5CoSi2 reveal a ferromagnetic behaviour below TC=168 K. This magnetic ordering is associated to an interesting magnetocaloric effect; the adiabatic temperature change ΔTad is about 3.1 and 5.9 K, respectively, for a magnetic field change of 2 and 4.6 T. -- Graphical abstract: The adiabatic temperature change ΔTad was determined by combining the heat capacity measurements and the magnetization data. As expected, a peak near the Curie temperature of the Gd5CoSi2 ternary silicide is observed, with a maximum of ΔTad around 3.1 and 5.9 K for ΔH=2 and 4.6 T, respectively. Display Omitted Research Highlights: → We prepare and characterize for the first time the ternary silicide Gd5CoSi2. → Gd5CoSi2 crystallizes in the tetragonal structure deriving from the Cr5B3-type. → Gd5CoSi2 shows a ferromagnetic behaviour below 168 K associated with magnetocaloric properties.

  19. X-ray photoemission spectromicroscopy of titanium silicide formation in patterned microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Singh, S.; Solak, H.; Cerrina, F. [Univ. of Wisconsin-Madison, Stoughton, WI (United States)] [and others

    1997-04-01

    Titanium silicide has the lowest resistivity of all the refractory metal silicides and has good thermal stability as well as excellent compatibility with Al metallization. It is used as an intermediate buffer layer between W vias and the Si substrate to provide good electrical contact in ULSI technology, whose submicron patterned features form the basis of the integrated circuits of today and tomorrow, in the self aligned silicide (salicide) formation process. TiSi{sub 2} exists in two phases: a metastable C49 base-centered orthorhombic phase with specific resistivity of 60-90 {mu}{Omega}-cm that is formed at a lower temperature (formation anneal) and the stable 12-15 {mu}{Omega}-cm resistivity face-centered orthorhombic C54 phase into which C49 is transformed with a higher temperature (conversion anneal) step. C54 is clearly the target for low resistivity VLSI interconnects. However, it has been observed that when dimensions shrink below 1/mic (or when the Ti thickness drops below several hundred angstroms), the transformation of C49 into C54 is inhibited and agglomeration often occurs in fine lines at high temperatures. This results in a rise in resistivity due to incomplete transformation to C54 and because of discontinuities in the interconnect line resulting from agglomeration. Spectromicroscopy is an appropriate tool to study the evolution of the TiSi2 formation process because of its high resolution chemical imaging ability which can detect bonding changes even in the absence of changes in the relative amounts of species and because of the capability of studying thick {open_quotes}as is{close_quotes} industrial samples.

  20. Combustion synthesis of molybdenum silicides and borosilicides for ultrahigh-temperature structural applications

    Science.gov (United States)

    Alam, Mohammad Shafiul

    Molybdenum silicides and borosilicides are promising structural materials for gas-turbine power plants. A major challenge, however, is to simultaneously achieve high oxidation resistance and acceptable mechanical properties at high temperatures. For example, molybdenum disilicide (MoSi2) has excellent oxidation resistance and poor mechanical properties, while Mo-rich silicides such as Mo5Si3 (called T 1) have much better mechanical properties but poor oxidation resistance. One approach is based on the fabrication of MoSi2-T 1 composites that combine high oxidation resistance of MoSi2 and good mechanical properties of T1. Another approach involves the addition of boron to Mo-rich silicides for improving their oxidation resistance through the formation of a borosilicate surface layer. In particular, Mo 5SiB2 (called T2) phase is considered as an attractive material. In the thesis, MoSi2-T1 composites and materials based on T2 phase are obtained by mechanically activated SHS. Use of SHS compaction (quasi-isostatic pressing) significantly improves oxidation resistance of the obtained MoSi2-T1 composites. Combustion of Mo-Si-B mixtures for the formation of T2 phase becomes possible if the composition is designed for the addition of more exothermic reactions leading to the formation of molybdenum boride. These mixtures exhibit spin combustion, the characteristics of which are in good agreement with the spin combustion theory. Oxidation resistance of the obtained Mo-Si-B materials is independent on the concentration of Mo phase in the products so that the materials with a higher Mo content are preferable because of better mechanical properties. Also, T2 phase has been obtained by the chemical oven combustion synthesis technique.

  1. Effect of Annealing Temperature on the Formation of Silicides and the Surface Morphologies of PtSi Films

    Institute of Scientific and Technical Information of China (English)

    2001-01-01

    The effect of annealing temperature on the formation of the PtSi phase, distribution of silicides and the surface morphologies of silicides films is investigated by XPS, AFM. It is shown that the phase sequences of the films change from Pt-Pt2Si-PtSi-Si to Pt+Pt2Si+PtSi-PtSi-Si or Pt+Pt2Si+PtSi-PtSi-Si with an increase of annealing temperature and the reason for the formation of mixed layers is discussed.

  2. Electrochemical deposition of coating from carbide, boride and silicide of IV-VIA group metals in ion melts

    International Nuclear Information System (INIS)

    The prehistory of the development of methods of production of metal-like refractory coatings (titanium, tantalum, niobium, vanadium, zirconium carbides, borides and silicides) with the help of high-temperature electrochemical synthesis (HTES) in ionic melts is described. A review is made on studies into the process of HTES of refractory metal borides, carbides and silicides, manufacture conditions for the coatings and electrolyte compositions (oxide, oxide-fluoride, chloride, chloride-fluoride melts). Structure and properties of coatings produced by the method of HTES are under consideration

  3. Silicidation of Mo-alloyed ytterbium: Mo alloying effects on microstructure evolution and contact properties

    International Nuclear Information System (INIS)

    In this study, we investigated the effects of Mo addition to Yb as a contact material with Si for metal–oxide-semiconductor field-effect transistors (MOSFETs) to mitigate oxidation problems, a persistent problem for rare-earth metal-based contacts (such as Yb/Si and Er/Si). Our thorough materials characterization using transmission electron microscopy and X-ray diffraction unravels Mo segregation during silicidation and its effect against oxidation. I–V characteristics, measured from Schottky diodes produced from the samples, reflect such microstructure evolution and demonstrate a strong improvement in contact properties at high temperatures

  4. High-Temperature Compatible Nickel Silicide Thermometer And Heater For Catalytic Chemical Microreactors

    DEFF Research Database (Denmark)

    Jensen, Søren; Quaade, U.J.; Hansen, Ole

    2005-01-01

    Integration of heaters and thermometers is important for agile and accurate control and measurement of the thermal reaction conditions in microfabricated chemical reactors (microreactors). This paper describes development and operation of nickel silicide heaters and temperature sensors...... for temperatures exceeding 700 °C. The heaters and thermometers are integrated with chemical microreactors for heterogeneous catalytic conversion of gasses, and thermally activated catalytic conversion of CO to CO2 in the reactors is demonstrated. The heaters and thermometers are shown to be compatible...... with operation temperatures exceeding 700 °C....

  5. Magnetization reversal of ultrathin Fe film grown on Si(111) using iron silicide template

    Institute of Scientific and Technical Information of China (English)

    He Wei; Zhan Qing-Feng; Wang De-Yong; Chen Li-Jun; Sun Young; Cheng Zhao-Hua

    2007-01-01

    Ultrathin Fe films were epitaxially grown on Si(111) by using an ultrathin iron silicide film with p(2 × 2) surface reconstruction as a template. The surface structure and magnetic properties were investigated in situ by low energy electron diffraction (LEED), scanning tunnelling microscopy (STM), and surface magneto-optical effect (SMOKE). Polar SMOKE hysteresis loops demonstrate that the Fe ultrathin films with thickness t< 6 ML (monolayers) exhibit perpendicular magnetic anisotropy. The characters of M-H loops with the external magnetic field at difference angles and the angular dependence of coercivity suggest that the domain-wall pinning plays a dominant role in the magnetization reversal process.

  6. Transient behavior of silicide plate-type fuel during reactivity initiated accident conditions

    International Nuclear Information System (INIS)

    The results of transient experiments using a low enriched uranium silicide mini-plate fuel (19 w/o 235U, 4.8gU/c.c.) for research reactors are described. Studies were addressed mainly to clarifying 1) fuel failure threshold and failure mechanism, and 2) dimensional stability of the fuel plate at the temperature ranged from 140degC to 970degC. The pulse irradiation of the mini-plate fuels was performed in the Nuclear Safety Research Reactor (NSRR) at the Japan Atomic Energy Research Institute (JAERI). (author)

  7. Oxidation resistant silicide coatings for Nbss/Nb5Si3 in-situ composites

    International Nuclear Information System (INIS)

    Oxidation protective silicide coatings for the new Nbss/Nb5Si3 in-situ composites were prepared by molten salt method. The experiment results indicated that the majority phase in the coating was NbSi2. More Nb5Si3 was formed at the interface between the substrate and NbSi2 layer during the oxidation. The oxidation resistance of the composites was improved by the coating, significantly. The improvement in the oxidation resistance of the composites maybe mainly attributed to the formation of large amount of SiO2 and Al2O3 on surface of coating. (orig.)

  8. Synthesis of metallic silicide fullerenes and the characteristics thereof by mass spectrometry

    Institute of Scientific and Technical Information of China (English)

    CHEN YiChi; GUO Liang; ZHU LiQun

    2007-01-01

    Direct current arc discharge is used for the study on the synthesis of metallofullerenes (MFs) to discover whether there exist metallic silicide fullerenes and silicon fullerenes. The resultant components are isolated by the multistage high-performance liquid chromatography (HPLC) and analyzed with the Time-of-Flight (TOF) mass spectrometry. Results show that there exist fullerenes such as SiC69, YSi2C64, YSi2C78, Y3Si2C78 as well as Y2Si2C90 which are structurally similar to (Y2C2)@C82.

  9. Synthesis of metallic silicide fullerenes and the characteristics thereof by mass spectrometry

    Institute of Scientific and Technical Information of China (English)

    2007-01-01

    Direct current arc discharge is used for the study on the synthesis of metallo-fullerenes (MFs) to discover whether there exist metallic silicide fullerenes and silicon fullerenes. The resultant components are isolated by the multistage high-performance liquid chromatography (HPLC) and analyzed with the Time-of-Flight (TOF) mass spectrometry. Results show that there exist fullerenes such as SiC69, YSi2C64, YSi2C78, Y3Si2C78 as well as Y2Si2C90 which are structurally similar to (Y2C2)@C82.

  10. Tungsten silicide contacts to polycrystalline silicon and silicon-germanium alloys

    Energy Technology Data Exchange (ETDEWEB)

    Srinivasan, G. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom)]. E-mail: g.srinivasan@ee.qub.ac.uk; Bain, M.F. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Bhattacharyya, S. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Baine, P. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Armstrong, B.M. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); Gamble, H.S. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom); McNeill, D.W. [Northern Ireland Semiconductor Research Centre, School of Electrical and Electronic Engineering, Queen' s University, Ashby Building, Stranmillis Road, Belfast BT9 5AH, Northern Ireland (United Kingdom)

    2004-12-15

    Silicon-germanium alloy layers will be employed in the source-drain engineering of future MOS transistors. The use of this technology offers advantages in reducing series resistance and decreasing junction depth resulting in reduction in punch-through and SCE problems. The contact resistance of metal or metal silicides to the raised source-drain material is a serious issue at sub-micron dimensions and must be minimised. In this work, tungsten silicide produced by chemical vapour deposition has been investigated as a contact metallization scheme to both boron and phosphorus doped polycrystalline Si{sub 1-} {sub x} Ge {sub x} , with 0 {<=}x {<=} 0.3. Cross bridge Kelvin resistor (CKBR) structures were fabricated incorporating CVD WSi{sub 2} and polycrystalline SiGe. Tungsten silicide contacts to control polysilicon CKBR structures have been shown to be of high quality with specific contact resistance {rho} {sub c} values 3 x 10{sup -7} ohm cm{sup 2} and 6 x 10{sup -7} ohm cm{sup 2} obtained to boron and phosphorus implanted samples respectively. The SiGe CKBR structures show that the inclusion of Ge yields a reduction in {rho} {sub c} for both dopant types. The boron doped SiGe exhibits a reduction in {rho} {sub c} from 3 x 10{sup -7} to 5 x 10{sup -8} ohm cm{sup 2} as Ge fraction is increased from 0 to 0.3. The reduction in {rho} {sub c} has been shown to be due to (i) the lowering of the tungsten silicide Schottky barrier height to p-type SiGe resulting from the energy band gap reduction, and (ii) increased activation of the implanted boron with increased Ge fraction. The phosphorus implanted samples show less sensitivity of {rho} {sub c} to Ge fraction with a lowest value in this work of 3 x 10{sup -7} ohm cm{sup 2} for a Ge fraction of 0.3. The reduction in specific contact resistance to the phosphorus implanted samples has been shown to be due to increased dopant activation alone.

  11. On the structural and electronic properties of Ir-silicide nanowires on Si(001) surface

    Science.gov (United States)

    Fatima, Can Oguz, Ismail; ćakır, Deniz; Hossain, Sehtab; Mohottige, Rasika; Gulseren, Oguz; Oncel, Nuri

    2016-09-01

    Iridium (Ir) modified Silicon (Si) (001) surface is studied with Scanning Tunneling Microscopy/Spectroscopy (STM/STS) and Density Functional Theory (DFT). A model for Ir-silicide nanowires based on STM images and ab-initio calculations is proposed. According to our model, the Ir adatom is on the top of the substrate dimer row and directly binds to the dimer atoms. I-V curves measured at 77 K shows that the nanowires are metallic. DFT calculations confirm strong metallic nature of the nanowires.

  12. Americium(3) coordination chemistry: An unexplored diversity of structure and bonding

    Energy Technology Data Exchange (ETDEWEB)

    Fedosseev, A.M.; Grigoriev, M.S.; Budantseva, N.A. [A.N. Frumkin Institute of Physical Chemistry and Electrochemistry, Moscow (Russian Federation); Guillaumont, D.; Den Auwer, Ch.; Moisy, Ph. [CEA Marcoule, Nuclear Energy Division, RadioChemistry and Processes Department, 30 (France); Le Naour, C.; Simoni, E. [CNRS, University Paris-11 Orsay, IPN, 91 - Orsay (France)

    2010-06-15

    The comparison of the physicochemical behavior of the actinides with that of the lanthanides can be justified by the analogy of their electronic structure, as each of the series is made up of elements corresponding to the filling of a given (n)f atomic shell. However relatively few points of comparison are available, given the lack of available structure for trans-plutonium(III) elements and the additional difficulty of stabilizing coordination complexes of uranium(III) to plutonium(III). This contribution is a focal point of trans-plutonium(III) chemistry and, more specifically, of some americium compounds that have been recently synthesized, all related with hard acid oxygen donor ligands that may be involved in the reprocessing chain of nuclear fuel. After a brief review of the solid hydrates and aquo species for the lanthanide and actinide families, we discuss two types of ligands that have in common three carboxylic groups, namely the amino-tri-acetic acid and the citric acid anions. The additional roles of the nitrogen atom for the first one and of the hydroxy function for the second one are discussed. Accordingly, five new complexes with either americium or lanthanides elements are described: [Co(NH{sub 3}){sub 6}][M(NTA){sub 2}(H{sub 2}O)].8H{sub 2}O with M Nd, Yb and Am, and [Co(NH{sub 3}){sub 6}]{sub 2}K[M{sub 3}(Cit){sub 4}(H{sub 2}O){sub 3}].18H{sub 2}O with Nd and Am cations. In all cases the americium complexes are isostructural with their lanthanide equivalents. (authors)

  13. Americium(3) coordination chemistry: An unexplored diversity of structure and bonding

    International Nuclear Information System (INIS)

    The comparison of the physicochemical behavior of the actinides with that of the lanthanides can be justified by the analogy of their electronic structure, as each of the series is made up of elements corresponding to the filling of a given (n)f atomic shell. However relatively few points of comparison are available, given the lack of available structure for trans-plutonium(III) elements and the additional difficulty of stabilizing coordination complexes of uranium(III) to plutonium(III). This contribution is a focal point of trans-plutonium(III) chemistry and, more specifically, of some americium compounds that have been recently synthesized, all related with hard acid oxygen donor ligands that may be involved in the reprocessing chain of nuclear fuel. After a brief review of the solid hydrates and aquo species for the lanthanide and actinide families, we discuss two types of ligands that have in common three carboxylic groups, namely the amino-tri-acetic acid and the citric acid anions. The additional roles of the nitrogen atom for the first one and of the hydroxy function for the second one are discussed. Accordingly, five new complexes with either americium or lanthanides elements are described: [Co(NH3)6][M(NTA)2(H2O)].8H2O with M Nd, Yb and Am, and [Co(NH3)6]2K[M3(Cit)4(H2O)3].18H2O with Nd and Am cations. In all cases the americium complexes are isostructural with their lanthanide equivalents. (authors)

  14. MARIOS: Irradiation of UO{sub 2} containing 15% americium at well defined temperature

    Energy Technology Data Exchange (ETDEWEB)

    D' Agata, E., E-mail: elio.dagata@ec.europa.eu [European Commission, Joint Research Centre, Institute for Energy - P.O. Box 2, 1755 ZG Petten (Netherlands); Hania, P.R. [Nuclear Research and Consultancy Group, P.O. Box 25, 1755 ZG Petten (Netherlands); Bejaoui, S. [Commissariat a l' Energie Atomique, DEC CEA-Cadarache, 13108 St. Paul lez Durance Cedex (France); Sciolla, C.; Wyatt, T.; Hannink, M.H.C. [Nuclear Research and Consultancy Group, P.O. Box 25, 1755 ZG Petten (Netherlands); Herlet, N.; Jankowiak, A. [Commissariat a l' Energie Atomique DTEC CEA Marcoule, 30207 Bagnols sur Ceze Cedex (France); Klaassen, F.C. [Nuclear Research and Consultancy Group, P.O. Box 25, 1755 ZG Petten (Netherlands); Bonnerot, J.-M. [Commissariat a l' Energie Atomique, DEC CEA-Cadarache, 13108 St. Paul lez Durance Cedex (France)

    2012-01-15

    Highlights: Black-Right-Pointing-Pointer MARIOS is designed to check the behaviour of Minor Actinide Blanket Module concept. Black-Right-Pointing-Pointer Main requirement of the experiment is an accurate control of the temperature. Black-Right-Pointing-Pointer The swelling and the helium release will be the main output of the experiment. Black-Right-Pointing-Pointer A complementary experiment (DIAMINO), will be performed in the next future. - Abstract: Americium is a strong contributor to the long term radiotoxicity of high activity nuclear waste. Transmutation by irradiation in nuclear reactors of long-lived nuclides like {sup 241}Am is, therefore, an option for the reduction of radiotoxicity and residual power packages as well as the repository area. The MARIOS irradiation experiment is the latest of a series of experiments on americium transmutation (e.g. EFTTRA-T4, EFTTRA-T4bis, HELIOS). MARIOS experiment is carried out in the framework of the 4-year project FAIRFUELS of the EURATOM 7th Framework Programme (FP7). During the past years of experimental work in the field of transmutation and tests of innovative nuclear fuel containing americium, the release or trapping of helium as well as swelling has shown to be the key issue for the design of such kinds of target. Therefore, the main objective of the MARIOS experiment is to study the in-pile behaviour of UO{sub 2} containing minor actinides (MAs) in order to gain knowledge on the role of the microstructure and of the temperature on the gas release and on fuel swelling. The MARIOS experiment will be conducted in the HFR (high flux reactor) in Petten (The Netherlands) and will start in the beginning of 2011. It has been planned that the experiment will last 11 cycles, corresponding to 11 months. This paper covers the description of the objective of the experiment, as well as a general description of the design of the experiment.

  15. Speciation of americium in seawater and accumulation in the marine sponge Aplysina cavernicola.

    Science.gov (United States)

    Maloubier, Melody; Michel, Hervé; Solari, Pier Lorenzo; Moisy, Philippe; Tribalat, Marie-Aude; Oberhaensli, François R; Dechraoui Bottein, Marie Yasmine; Thomas, Olivier P; Monfort, Marguerite; Moulin, Christophe; Den Auwer, Christophe

    2015-12-21

    The fate of radionuclides in the environment is a cause of great concern for modern society, seen especially in 2011 after the Fukushima accident. Among the environmental compartments, seawater covers most of the earth's surface and may be directly or indirectly impacted. The interaction between radionuclides and the marine compartment is therefore essential for better understanding the transfer mechanisms from the hydrosphere to the biosphere. This information allows for the evaluation of the impact on humans via our interaction with the biotope that has been largely undocumented up to now. In this report, we attempt to make a link between the speciation of heavy elements in natural seawater and their uptake by a model marine organism. More specifically, because the interaction of actinides with marine invertebrates has been poorly studied, the accumulation in a representative member of the Mediterranean coralligenous habitat, the sponge Aplysina cavernicola, was investigated and its uptake curve exposed to a radiotracer (241)Am was estimated using a high-purity Ge gamma spectrometer. But in order to go beyond the phenomenological accumulation rate, the speciation of americium(III) in seawater must be assessed. The speciation of (241)Am (and natural europium as its chemically stable surrogate) in seawater was determined using a combination of different techniques: Time-Resolved Laser-Induced Fluorescence (TRLIF), Extended X-ray Absorption Fine Structure (EXAFS) at the LIII edge, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM) and the resulting data were compared with the speciation modeling. In seawater, the americium(III) complex (as well as the corresponding europium complex, although with conformational differences) was identified as a ternary sodium biscarbonato complex, whose formula can be tentatively written as NaAm(CO3)2·nH2O. It is therefore this chemical form of americium that is

  16. Speciation of americium in seawater and accumulation in the marine sponge Aplysina cavernicola.

    Science.gov (United States)

    Maloubier, Melody; Michel, Hervé; Solari, Pier Lorenzo; Moisy, Philippe; Tribalat, Marie-Aude; Oberhaensli, François R; Dechraoui Bottein, Marie Yasmine; Thomas, Olivier P; Monfort, Marguerite; Moulin, Christophe; Den Auwer, Christophe

    2015-12-21

    The fate of radionuclides in the environment is a cause of great concern for modern society, seen especially in 2011 after the Fukushima accident. Among the environmental compartments, seawater covers most of the earth's surface and may be directly or indirectly impacted. The interaction between radionuclides and the marine compartment is therefore essential for better understanding the transfer mechanisms from the hydrosphere to the biosphere. This information allows for the evaluation of the impact on humans via our interaction with the biotope that has been largely undocumented up to now. In this report, we attempt to make a link between the speciation of heavy elements in natural seawater and their uptake by a model marine organism. More specifically, because the interaction of actinides with marine invertebrates has been poorly studied, the accumulation in a representative member of the Mediterranean coralligenous habitat, the sponge Aplysina cavernicola, was investigated and its uptake curve exposed to a radiotracer (241)Am was estimated using a high-purity Ge gamma spectrometer. But in order to go beyond the phenomenological accumulation rate, the speciation of americium(III) in seawater must be assessed. The speciation of (241)Am (and natural europium as its chemically stable surrogate) in seawater was determined using a combination of different techniques: Time-Resolved Laser-Induced Fluorescence (TRLIF), Extended X-ray Absorption Fine Structure (EXAFS) at the LIII edge, Attenuated Total Reflectance Fourier Transform Infrared (ATR-FTIR) spectroscopy and Scanning Electron Microscopy (SEM) and the resulting data were compared with the speciation modeling. In seawater, the americium(III) complex (as well as the corresponding europium complex, although with conformational differences) was identified as a ternary sodium biscarbonato complex, whose formula can be tentatively written as NaAm(CO3)2·nH2O. It is therefore this chemical form of americium that is

  17. Americium characterization by X-ray fluorescence and absorption spectroscopy in plutonium uranium mixed oxide

    International Nuclear Information System (INIS)

    Plutonium uranium mixed oxide (MOX) fuels are currently used in nuclear reactors. The actinides in these fuels need to be analyzed after irradiation for assessing their behaviour with regard to their environment and the coolant. In this work the study of the atomic structure and next-neighbour environment of Am in the (Pu,U)O2 lattice in an irradiated (60 MW d kg−1) MOX sample was performed employing micro-X-ray fluorescence (µ-XRF) and micro-X-ray absorption fine structure (µ-XAFS) spectroscopy. The chemical bonds, valences and stoichiometry of Am (∼0.66 wt%) are determined from the experimental data gained for the irradiated fuel material examined in its peripheral zone (rim) of the fuel. In the irradiated sample Am builds up as Am3+ species within an [AmO8]13− coordination environment (e.g. >90%) and no (III XAFS spectra recorded for the irradiated MOX sub-sample in the rim zone for a 300 μm×300 μm beam size area investigated over six scans of 4 h. The records remain constant during multi-scan. The analysis of the XAFS signal shows that Am is found as trivalent in the UO2 matrix. This analytical work shall open the door of very challenging analysis (speciation of fission product and actinides) in irradiated nuclear fuels. - Highlights: • Americium was characterized by microX-ray absorption spectroscopy in irradiated MOX fuel. • The americium redox state as determined from XAS data of irradiated fuel material was Am(III). • In the sample, the Am3+ face an AmO813− coordination environment in the (Pu,U)O2 matrix. • The americium dioxide is reduced by the uranium dioxide matrix

  18. Fabrication of uranium–americium mixed oxide pellet from microsphere precursors: Application of CRMP process

    Energy Technology Data Exchange (ETDEWEB)

    Remy, E. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Picart, S., E-mail: sebastien.picart@cea.fr [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Delahaye, T. [Fuel Cycle Technology Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Jobelin, I. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Lebreton, F.; Horlait, D. [Fuel Cycle Technology Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Bisel, I. [Radiochemistry and Processes Department, CEA, Nuclear Energy Division, F-30207 Bagnols-sur-Cèze (France); Blanchart, P. [Heterogeneous Materials Research Group, Centre Européen de la Céramique, F-87068 Limoges (France); Ayral, A. [Institut Européen des Membranes, CNRS-ENSCM-UM2, CC47, University Montpellier 2, F-34095 Montpellier cedex 5 (France)

    2014-10-15

    Highlights: • Dust free process for (U,Am)O{sub 2} transmutation target fabrication. • Synthesis of U{sub 0.9}Am{sub 0.1}O{sub 2} mixed oxide microspheres from ion exchange resin. • Fabrication of dense U{sub 0.9}Am{sub 0.1}O{sub 2} pellet with 95% TD from mixed oxide microspheres. - Abstract: Mixed uranium–americium oxides are one of the materials envisaged for Americium Bearing Blankets dedicated to transmutation in fast neutron reactors. Recently, several processes have been developed in order to validate fabrication flowchart in terms of material specifications such as density and homogeneity but also to suggest simplifications for lowering industrial costs and hazards linked to dust generation of highly contaminating and irradiating compounds. This study deals with the application of an innovative route using mixed oxide microspheres obtained from metal loaded resin bead calcination, called Calcined Resin Microsphere Pelletization (CRMP). The synthesis of mixed oxide microsphere precursor of U{sub 0.9}Am{sub 0.1}O{sub 2±δ} is described as well as its characterisation. The use of this free-flowing precursor allows the pressing and sintering of one pellet of U{sub 0.9}Am{sub 0.1}O{sub 2±δ}. The ceramic obtained was characterised and results showed that its microstructure is dense and homogeneous and its density attains 95% of the theoretical density. This study validates the scientific feasibility of the CRMP process applied to the fabrication of uranium and americium-containing materials.

  19. Influence of biofilms on migration of uranium, americium and europium in the environment

    International Nuclear Information System (INIS)

    The report on the influence of biofilms on migration of uranium, americium and europium in the environment deals with the contamination problems of uranium mines such as SDAG WISMUT in Saxonia and Thuringia. In mine waters microorganisms form a complex microbiological biocoenosis in spite of low pH values and high heavy metal concentrations including high uranium concentrations. The analyses used microbiological methods like confocal laser scanning microscopy and molecular-biological techniques. The interactions of microorganism with fluorescent radioactive heavy metal ions were performed with TRLFS (time resolved laser-induced fluorescence spectroscopy).

  20. Plutonium and americium in arctic waters, the North Sea and Scottish and Irish coastal zones

    DEFF Research Database (Denmark)

    Hallstadius, L.; Aarkrog, Asker; Dahlgaard, Henning;

    1986-01-01

    Plutonium and americium have been measured in surface waters of the Greenland and Barents Seas and in the northern North Sea from 1980 through 1984. Measurements in water and biota, Fucus, Mytilus and Patella, were carried out in North-English and Scottish waters in 1982 and Fucus samples were...... plutonium from the latter to Spitsbergen waters. Fallout plutonium in Arctic waters has a residence time of the order of several years, while for Pu from Sellafield we estimate mean residence times of 11–15 months in Scottish waters and, tentatively, 1·5-3 y during transport from the North Channel (north...

  1. Comparison of acid leachate and fusion methods to determine plutonium and americium in environmental samples

    International Nuclear Information System (INIS)

    The Analytical Chemistry Laboratory at Argonne National Laboratory performs radiochemical analyses for a wide variety of sites within the Department of Energy complex. Since the chemical history of the samples may vary drastically from site to site, the effectiveness of any analytical technique may also vary. This study compares a potassium fluoride-pyrosulfate fusion technique with an acid leachate method. Both normal and high-fired soils and vegetation samples were analyzed for both americium and plutonium. Results show both methods work well, except for plutonium in high-fired soils. Here the fusion method provides higher accuracy

  2. Purification of used scintillation liquids containing the alpha emitters americium and plutonium

    International Nuclear Information System (INIS)

    In Sweden, alpha radioactive waste liquids with an activity over some kBq per waste container cannot be sent for final storage. Therefore, in this work, a method for a purification of alpha active scintillation cocktails was developed. Until today (March, 2013) more than 20 L of scintillation liquids have successfully been purified from americium and plutonium. The products of the process are a solid fraction that can be sent to final storage and a practically non-radioactive liquid fraction that can be sent to municipal incineration. (author)

  3. Study of the extraction and the purification of americium and trivalent actinides contained in effluents with supported liquid membranes

    International Nuclear Information System (INIS)

    The supported liquid membrane technique is studied and developed for americium recovery from uranium or plutonium matrices and decontamination of liquid radioactive wastes. First tests on uranium-nickel solutions with a flat membrane showed the easiness of the operation and the efficiency of the process. Acid-resistant (10 N), interchangeable elements with hollow fibers, are developed and also a computerized automatic device. The different tests on americium solutions demonstrate the feasibility and the reliability of the system. Influence of various parameters on transfer kinetics is investigated

  4. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    Science.gov (United States)

    Harp, Jason M.; Lessing, Paul A.; Hoggan, Rita E.

    2015-11-01

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ± 0.06 g/cm3. Additional characterization of the pellets by scanning electron microscopy and X-ray diffraction has also been performed. Pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon.

  5. Uranium silicide pellet fabrication by powder metallurgy for accident tolerant fuel evaluation and irradiation

    International Nuclear Information System (INIS)

    In collaboration with industry, Idaho National Laboratory is investigating uranium silicide for use in future light water reactor fuels as a more accident resistant alternative to uranium oxide base fuels. Specifically this project was focused on producing uranium silicide (U3Si2) pellets by conventional powder metallurgy with a density greater than 94% of the theoretical density. This work has produced a process to consistently produce pellets with the desired density through careful optimization of the process. Milling of the U3Si2 has been optimized and high phase purity U3Si2 has been successfully produced. Results are presented from sintering studies and microstructural examinations that illustrate the need for a finely ground reproducible particle size distribution in the source powder. The optimized process was used to produce pellets for the Accident Tolerant Fuel-1 irradiation experiment. The average density of these pellets was 11.54 ±0.06 g/cm3. Additional characterization of the pellets by scaning electron microscopy and X-ray diffraction has also been performed. As a result, pellets produced in this work have been encapsulated for irradiation, and irradiation in the Advanced Test Reactor is expected soon

  6. Microstructure of the irradiated U 3Si 2/Al silicide dispersion fuel

    Science.gov (United States)

    Gan, J.; Keiser, D. D.; Miller, B. D.; Jue, J.-F.; Robinson, A. B.; Madden, J. W.; Medvedev, P. G.; Wachs, D. M.

    2011-12-01

    The silicide dispersion fuel of U 3Si 2/Al is recognized as the best performance fuel for many nuclear research and test reactors with up to 4.8 gU/cm 3 fuel loading. An irradiated U 3Si 2/Al dispersion fuel ( 235U ˜ 75%) from the high-flux side of a fuel plate (U0R040) from the Reduced Enrichment for Research and Test Reactors (RERTR)-8 test was characterized using transmission electron microscopy (TEM). The fuel was irradiated in the Advanced Test Reactor (ATR) for 105 days. The average irradiation temperature and fission density of the U 3Si 2 fuel particles for the TEM sample are estimated to be approximately 110 °C and 5.4 × 10 27 f/m 3. The characterization was performed using a 200-kV TEM. The U/Si ratio for the fuel particle and (Si + Al)/U for the fuel-matrix-interaction layer are approximately 1.1 and 4-10, respectively. The estimated average diameter, number density and volume fraction for small bubbles (fuel particle are ˜94 nm, 1.05 × 10 20 m -3 and ˜11%, respectively. The results and their implication on the performance of the U 3Si 2/Al silicide dispersion fuel are discussed.

  7. Magnesium and Manganese Silicides For Efficient And Low Cost Thermo-Electric Power Generation

    Energy Technology Data Exchange (ETDEWEB)

    Trivedi, Sudhir B. [Brimrose Technology Corporation; Kutcher, Susan W. [Brimrose Technology Corporation; Rosemeier, Cory A. [Brimrose Technology Corporation; Mayers, David [Brimrose Technology Corporation; Singh, Jogender [Pennsylvania State University

    2013-12-02

    Thermoelectric Power Generation (TEPG) is the most efficient and commercially deployable power generation technology for harvesting wasted heat from such things as automobile exhausts, industrial furnaces, and incinerators, and converting it into usable electrical power. We investigated the materials magnesium silicide (Mg2Si) and manganese silicide (MnSi) for TEG. MgSi2 and MnSi are environmentally friendly, have constituent elements that are abundant in the earth's crust, non-toxic, lighter and cheaper. In Phase I, we successfully produced Mg2Si and MnSi material with good TE properties. We developed a novel technique to synthesize Mg2Si with good crystalline quality, which is normally very difficult due to high Mg vapor pressure and its corrosive nature. We produced n-type Mg2Si and p-type MnSi nanocomposite pellets using FAST. Measurements of resistivity and voltage under a temperature gradient indicated a Seebeck coefficient of roughly 120 V/K on average per leg, which is quite respectable. Results indicated however, that issues related to bonding resulted in high resistivity contacts. Determining a bonding process and bonding material that can provide ohmic contact from room temperature to the operating temperature is an essential part of successful device fabrication. Work continues in the development of a process for reproducibly obtaining low resistance electrical contacts.

  8. Preliminary investigations on the use of uranium silicide targets for fission Mo-99 production

    Energy Technology Data Exchange (ETDEWEB)

    Cols, H.; Cristini, P.; Marques, R.

    1997-08-01

    The National Atomic Energy Commission (CNEA) of Argentine Republic owns and operates an installation for production of molybdenum-99 from fission products since 1985, and, since 1991, covers the whole national demand of this nuclide, carrying out a program of weekly productions, achieving an average activity of 13 terabecquerel per week. At present they are finishing an enlargement of the production plant that will allow an increase in the volume of production to about one hundred of terabecquerel. Irradiation targets are uranium/aluminium alloy with 90% enriched uranium with aluminium cladding. In view of international trends held at present for replacing high enrichment uranium (HEU) for enrichment values lower than 20 % (LEU), since 1990 the authors are in contact with the RERTR program, beginning with tests to adapt their separation process to new irradiation target conditions. Uranium silicide (U{sub 3}Si{sub 2}) was chosen as the testing material, because it has an uranium mass per volume unit, so that it allows to reduce enrichment to a value of 20%. CNEA has the technology for manufacturing miniplates of uranium silicide for their purposes. In this way, equivalent amounts of Molybdenum-99 could be obtained with no substantial changes in target parameters and irradiation conditions established for the current process with Al/U alloy. This paper shows results achieved on the use of this new target.

  9. Study of temperature dependent zirconium silicide phases in Zr/Si structure by differential scanning calorimetry

    International Nuclear Information System (INIS)

    The differential scanning calorimetry (DSC) technique is employed to study the formation of different silicide compounds of Zr thin-film deposited on a 100 μm-thick Si (1 0 0) substrate by dc sputtering. A detailed analysis shows that silicide layers start growing at  ∼246 °C that changes to stable ZrSi2 at 627 °C via some compounds with different stoichiometric ratios of Zr and Si. It is further observed that oxygen starts reacting with Zr at  ∼540 °C but a stoichiometric ZrO2 film is formed after complete consumption of Zr metal at 857 °C. A further rise in temperature changes a part of ZrSi2 to Zr-Silicate. The synchrotron radiation-based grazing incidence x-ray diffraction and x-ray photoelectron spectroscopy studies also corroborate the above findings. Atomic force microscopy is also carried out on the samples. It is evident from the observations that an intermixing and nucleation of Zr and Si occur at lower temperature prior to the formation of the interfacial silicate layer. Zr-Silicate formation takes place only at a higher temperature. (paper)

  10. Mitigation of interfacial silicide reactions for electroplated CoPt films on Si substrates

    Science.gov (United States)

    Oniku, Ololade D.; Arnold, David P.

    2015-12-01

    We report in this paper the influence of film thickness on the material and magnetic properties of electroplated CoPt permanent magnets. Layers of CoPt magnets with film thicknesses ranging from 0.5 μm to 5 μm are deposited into photoresist molds (3.5 mm x 3.5 mm square and 5 μm x 50 μm arrays) on a (100)Si substrate coated with 10 nm/100 nm Ti/Cu adhesion/seed layer. Results show an unexpected reduction in magnetic properties for films below 2 μm thick. This effect is determined to be a consequence of metal-silicide reactions at the substrate interface during annealing leading to the formation of a non-magnetic layer at the interface. Subsequently, a TiN diffusion-barrier layer is added to inhibit the silicide reaction and thereby maintain strong magnetic properties (Hci ∼800 kA/m, Mr/Ms = 0.8) in micron- thick electroplated CoPt layers.

  11. Prospect of Uranium Silicide fuel element with hypostoichiometric (Si ≤3.7%)

    International Nuclear Information System (INIS)

    An attempt to obtain high uranium-loading in silicide dispersion fuel element using the fabrication technology applicable nowadays can reach Uranium-loading slightly above 5 gU/cm3. It is difficult to achieve a higher uranium-loading than that because of fabricability constraints. To overcome those difficulties, the use of uranium silicide U3Si based is considered. The excess of U is obtained by synthesising U3Si2 in Si-hypostoichiometric stage, without applying heat treatment to the ingot as it can generate undesired U3Si. The U U will react with the matrix to form U alx compound, that its pressure is tolerable. This experiment is to consider possibilities of employing the U3Si2 as nuclear fuel element which have been performed by synthesising U3Si2-U with the composition of 3.7 % weigh and 3 % weigh U. The ingot was obtained and converted into powder form which then was fabricated into experimental plate nuclear fuel element. The interaction between free U and Al-matrix during heat-treatment is the rolling phase of the fuel element was observed. The study of the next phase will be conducted later

  12. "Nanoparticle-in-alloy" approach to efficient thermoelectrics: silicides in SiGe.

    Science.gov (United States)

    Mingo, N; Hauser, D; Kobayashi, N P; Plissonnier, M; Shakouri, A

    2009-02-01

    We present a "nanoparticle-in-alloy" material approach with silicide and germanide fillers leading to a potential 5-fold increase in the thermoelectric figure of merit of SiGe alloys at room temperature and 2.5 times increase at 900 K. Strong reductions in computed thermal conductivity are obtained for 17 different types of silicide nanoparticles. We predict the existence of an optimal nanoparticle size that minimizes the nanocomposite's thermal conductivity. This thermal conductivity reduction is much stronger and strikingly less sensitive to nanoparticle size for an alloy matrix than for a single crystal one. At the same time, nanoparticles do not negatively affect the electronic conduction properties of the alloy. The proposed material can be monolithically integrated into Si technology, enabling an unprecedented potential for micro refrigeration on a chip. High figure-of-merit at high temperatures (ZT approximately 1.7 at 900 K) opens up new opportunities for thermoelectric power generation and waste heat recovery at large scale.

  13. Organometallic halide perovskite/barium di-silicide thin-film double-junction solar cells

    Science.gov (United States)

    Vismara, R.; Isabella, O.; Zeman, M.

    2016-04-01

    Barium di-silicide (BaSi2) is an abundant and inexpensive semiconductor with appealing opto-electrical properties. In this work we show that a 2-μm thick BaSi2-based thin-film solar cell can exhibit an implied photo-current density equal to 41.1 mA/cm2, which is higher than that of a state-of-the-art wafer-based c-Si hetero-junction solar cell. This performance makes BaSi2 an attractive absorber for high-performing thin-film and multi-junction solar cells. In particular, to assess the potential of barium di-silicide, we propose a thin-film double-junction solar cell based on organometallic halide perovskite (CH3NH3PbI3) as top absorber and BaSi2 as bottom absorber. The resulting modelled ultra-thin double-junction CH3NH3PbI3 / BaSi2 (< 2 μm) exhibits an implied total photo-current density equal to 38.65 mA/cm2 (19.84 mA/cm2 top cell, 18.81 mA/cm2 bottom cell) and conversion efficiencies up to 28%.

  14. Effect of annealing on magnetic properties and silicide formation at Co/Si interface

    Indian Academy of Sciences (India)

    Shivani Agarwal; V Ganesan; A K Tyagi; I P Jain

    2006-11-01

    The interaction of Co (30 nm) thin films on Si (100) substrate in UHV using solid state mixing technique has been studied. Cobalt was deposited on silicon substrate using electron beam evaporation at a vacuum of 4 × 10-8 Torr having a deposition rate of about 0.1 Å/s. Reactivity at Co/Si interface is important for the understanding of silicide formation in thin film system. In the present paper, cobalt silicide films were characterized by atomic force microscopy (AFM) and secondary ion mass spectroscopy (SIMS) in terms of the surface and interface morphologies and depth profile, respectively. The roughness of the samples was found to increase up to temperature, 300°C and then decreased with further rise in temperature, which was due to the formation of crystalline CoSi2 phase. The effect of mixing on magnetic properties such as coercivity, remanence etc at interface has been studied using magneto optic Kerr effect (MOKE) techniques at different temperatures. The value of coercivity of pristine sample and 300°C annealed sample was found to be 66 Oe and 40 Oe, respectively, while at high temperature i.e. 748°C, the hysteresis disappears which indicates the formation of CoSi2 compound.

  15. Contribution to the prediction of americium, plutonium and neptunium behaviour in the geosphere: chemical data

    International Nuclear Information System (INIS)

    An exhaustive bibliographic review on hydrolysis of americium gives the stability constants, at zero ionic strength. No evidence of Am(OH)4- formation was found by solubility studies up to pH 2 (CO3)3 characterised by its X-ray diffraction pattern is studied at a high ionic strength. All the published results on Am in carbonate media are reinterpreted using these stability constants (Am-OH-CO3 complexes are not needed). No evidence of Am(CO3)45- formation was found by spectrophotometry up to 3M. Literature results are used to determine the formal redox potentials at pH = 9.4 and to calculate the formation constants, at zero ionic strength. The formation of complexes between americium and humic materials (purified fulvic and humic acids) has been studied by a spectrophotometric technique. The results are interpreted by the formation of a 1:1 complexe. Solubility of the solid PuO2(CO3) is measured in bicarbonate media at high ionic strength, to obtain the solubility product and formation constants of the PuO2(CO3)i2-2i complexes

  16. Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology.

    Science.gov (United States)

    Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

    2015-12-03

    This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm(2), and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p(+-)n homojunction through the formation of re-grown crystalline silicon layer (~5-10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method.

  17. Aluminium alloyed iron-silicide/silicon solar cells: A simple approach for low cost environmental-friendly photovoltaic technology

    Science.gov (United States)

    Kumar Dalapati, Goutam; Masudy-Panah, Saeid; Kumar, Avishek; Cheh Tan, Cheng; Ru Tan, Hui; Chi, Dongzhi

    2015-12-01

    This work demonstrates the fabrication of silicide/silicon based solar cell towards the development of low cost and environmental friendly photovoltaic technology. A heterostructure solar cells using metallic alpha phase (α-phase) aluminum alloyed iron silicide (FeSi(Al)) on n-type silicon is fabricated with an efficiency of 0.8%. The fabricated device has an open circuit voltage and fill-factor of 240 mV and 60%, respectively. Performance of the device was improved by about 7 fold to 5.1% through the interface engineering. The α-phase FeSi(Al)/silicon solar cell devices have promising photovoltaic characteristic with an open circuit voltage, short-circuit current and a fill factor (FF) of 425 mV, 18.5 mA/cm2, and 64%, respectively. The significant improvement of α-phase FeSi(Al)/n-Si solar cells is due to the formation p+-n homojunction through the formation of re-grown crystalline silicon layer (~5-10 nm) at the silicide/silicon interface. Thickness of the regrown silicon layer is crucial for the silicide/silicon based photovoltaic devices. Performance of the α-FeSi(Al)/n-Si solar cells significantly depends on the thickness of α-FeSi(Al) layer and process temperature during the device fabrication. This study will open up new opportunities for the Si based photovoltaic technology using a simple, sustainable, and los cost method.

  18. Influence of Al addition on phase transformation and thermal stability of nickel silicides on Si(0 0 1)

    International Nuclear Information System (INIS)

    Highlights: ► The presence of Al slows down the Ni2Si–NiSi phase transformation but significantly promotes the NiSi2−xAlx formation. ► The behavior of phase transformation strongly depends on the Al concentration of the initial Ni1−xAlx alloys. ► The Ni0.91Al0.09/Si system exhibits remarkably improved thermal stability, even after high temperature annealing for 1000 s. ► The relationship between microstructures, electrical property, and thermal stability of Ni(Al) silicides is discussed. -- Abstract: The influence of Al addition on the phase transformation and thermal stability of Ni silicides on (0 0 1)Si has been systematically investigated. The presence of Al atoms is found to slow down the Ni2Si–NiSi phase transformation but significantly promote the NiSi2−xAlx formation during annealing. The behavior of phase transformation strongly depends on the Al concentration of the initial Ni1−xAlx alloys. Compared to the Ni0.95Pt0.05/Si and Ni0.95Al0.05/Si system, the Ni0.91Al0.09/Si sample exhibits remarkably enhanced thermal stability, even after high temperature annealing for 1000 s. The relationship between microstructures, electrical property, and thermal stability of Ni silicides is discussed to elucidate the role of Al during the Ni1−xAlx alloy silicidation. This work demonstrated that thermally stable Ni1−xAlx alloy silicides would be a promising candidate as source/drain (S/D) contacts in advanced complementary metal–oxide-semiconductor (CMOS) devices

  19. The distribution of plutonium-239 and americium-241 in the Syrian hamster following its intravenous administration as citrate

    International Nuclear Information System (INIS)

    Actinide distribution in various tissues and the skeleton of hamsters by liquid scintillation counting or isotope dilution. For plutonium 57% of activity was concentrated in the skeleton and more than 90% in the liver and skeleton after seven days. For americium the liver retained more than 50% of total activity and 25% was excreted in urine within seven days. (U.K.)

  20. EURADOS intercomparison on measurements and Monte Carlo modelling for the assessment of Americium in a USTUR leg phantom

    International Nuclear Information System (INIS)

    A collaboration of the EURADOS working group on 'Internal Dosimetry' and the United States Transuranium and Uranium Registries (USTUR) has taken place to carry out an intercomparison on measurements and Monte Carlo modelling determining americium deposited in the bone of a USTUR leg phantom. Preliminary results and conclusions of this intercomparison exercise are presented here. (authors)

  1. Anomalous aryl strengthening of americium and europium complexes during extraction by alkylenediphosphine dioxides from perchloric acid media

    International Nuclear Information System (INIS)

    Extraction of americium and europium from perchlorate environments by solutions of three types of methylenediphosphine dioxides, namely (C6H5)P(O)(CH2)sub(n)(O)P(C6H5)2, (C6H5)2P(O)CH2(O)P(C8H17)2 and (C8H17)2P(O)(CH2)sub(n)(O)P(C8H17)2 has been studied (n is 1 or 2 ) The diluents used have been dichlorethane and chloroform. In perchlorate environments the distribuiton coefficients of americium and europium have proved to be by about 3 orders of magnitude higher than in nitric acid environments, i.e. in perchlorate media the complexes are far more stable. Separation coefficients of americium and REE in perchloric acid soutions are much higher than in nitrate environments. The average value of Am/Eu separation coeffecient at 1-5 M acidity was about 6 (with dichlorethane as diluent) or about 7 (with chloroform as diluent). The complexes essentially exist as trisolvated. Americium complexes display anomalous stability increase upon being diluted: by about 2 orders of magnitude with dichlorethane and by up to 3 orders of magnitude with chloroform used as diluent

  2. Investigations of neutron characteristics for salt blanket models; integral fission cross section measurements of neptunium, plutonium, americium and curium isotopes

    International Nuclear Information System (INIS)

    Neutron characteristics of salt blanket micromodels containing eutectic mixtures of sodium, zirconium, and uranium fluorides were measured on FKBN-2M, BIGR and MAKET facilities. The effective fission cross sections of neptunium, plutonium, americium, and curium isotopes were measured on the neutron spectra formed by micromodels. (author)

  3. Understanding and Improving High-Temperature Structural Properties of Metal-Silicide Intermetallics

    Energy Technology Data Exchange (ETDEWEB)

    Bruce S. Kang

    2005-10-10

    The objective of this project was to understand and improve high-temperature structural properties of metal-silicide intermetallic alloys. Through research collaboration between the research team at West Virginia University (WVU) and Dr. J.H. Schneibel at Oak Ridge National Laboratory (ORNL), molybdenum silicide alloys were developed at ORNL and evaluated at WVU through atomistic modeling analyses, thermo-mechanical tests, and metallurgical studies. In this study, molybdenum-based alloys were ductilized by dispersing MgAl2O4 or MgO spinel particles. The addition of spinel particles is hypothesized to getter impurities such as oxygen and nitrogen from the alloy matrix with the result of ductility improvement. The introduction of fine dispersions has also been postulated to improve ductility by acting as a dislocation source or reducing dislocation pile-ups at grain boundaries. The spinel particles, on the other hand, can also act as local notches or crack initiation sites, which is detrimental to the alloy mechanical properties. Optimization of material processing condition is important to develop the desirable molybdenum alloys with sufficient room-temperature ductility. Atomistic analyses were conducted to further understand the mechanism of ductility improvement of the molybdenum alloys and the results showed that trace amount of residual oxygen may be responsible for the brittle behavior of the as-cast Mo alloys. For the alloys studied, uniaxial tensile tests were conducted at different loading rates, and at room and elevated temperatures. Thermal cycling effect on the mechanical properties was also studied. Tensile tests for specimens subjected to either ten or twenty thermal cycles were conducted. For each test, a follow-up detailed fractography and microstructural analysis were carried out. The test results were correlated to the size, density, distribution of the spinel particles and processing time. Thermal expansion tests were carried out using thermo

  4. Purification of scintillation cocktails containing the alpha emitters americium and plutonium

    International Nuclear Information System (INIS)

    One efficient way of measuring alpha emitters is by the usage of liquid scintillation counting (LSC). A liquid sample is placed in a vial containing a scintillation cocktail. The alpha particles excite electrons in the surrounding liquid, and when they are de-excited photons are emitted. The photons are detected and the activity can be quantified. LSC has a high efficiency for alpha radiation and is therefore a fast and easy way for measuring alpha emitting samples. One drawback is that it does not differentiate very well between alpha energies; measurements of for example curium and plutonium simultaneously are impossible and demand other techniques. Another drawback is the production of a liquid alpha active waste. In Sweden alpha radioactive waste liquids with an activity over some kBq per waste container cannot be sent for final storage. If, however, the activity of the liquids could be reduced by precipitation of the actinides, it would be possible to send away the liquid samples to municipal incineration. In this work a method for a purification of alpha active scintillation cocktails was developed. The method was first tried on a lab scale, and then scaled up. Until today (March, 2013) more than 20 liters of scintillation liquids have successfully been purified from americium and plutonium at Chalmers University of Technology in Sweden. The four scintillation cocktails used were Emulsifier Safe®, Hionic-Fluor®, Ultima Gold AB® and Ultima Gold XR®. The scintillation cocktails could all be purified from americium with higher yield than 95%. The yield was kept when the liquids were mixed. Also plutonium could be precipitated with a yield over 95% in all cocktails except in Hionic-Fluor® (>55%). However, that liquid in particular could be purified (>95%) by mixing it with the three other cocktails. Up-scaling was performed to a batch size of 6-8 L of scintillation cocktail. In neither the americium nor the plutonium system, adverse effects of increasing the

  5. Modified fused silicide coatings for tantalum (Ta-10W) reentry heat shields

    Science.gov (United States)

    Packer, C. M.; Perkins, R. A.

    1973-01-01

    Results are presented of a program of research to develop a reliable, high performance, fused slurry silicide coating for the Ta-10W alloy. The effort was directed toward developing new and improved formulations for use at 2600 to 2800 F (1700 to 1811 K) in an atmospheric reentry thermal protection system with a 100-mission capability. Based on a thorough characterization of isothermal and cyclic oxidation behavior, bend transition temperatures, room- and elevated-temperature tensile properties, and creep behavior, a 2.5 Mn-33Ti-64.5Si coating (designated MTS) provides excellent protection for the Ta-10W alloy in simulated reentry environments. An extensive analysis of the oxidation behavior and characteristics of the MTS coating in terms of fundamental mechanisms also is presented.

  6. Hydrogen generation systems utilizing sodium silicide and sodium silica gel materials

    Science.gov (United States)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-07-14

    Systems, devices, and methods combine reactant materials and aqueous solutions to generate hydrogen. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Multiple inlets of varied placement geometries deliver aqueous solution to the reaction. The reactant materials and aqueous solution are churned to control the state of the reaction. The aqueous solution can be recycled and returned to the reaction. One system operates over a range of temperatures and pressures and includes a hydrogen separator, a heat removal mechanism, and state of reaction control devices. The systems, devices, and methods of generating hydrogen provide thermally stable solids, near-instant reaction with the aqueous solutions, and a non-toxic liquid by-product.

  7. Hydrogen generation systems and methods utilizing sodium silicide and sodium silica gel materials

    Science.gov (United States)

    Wallace, Andrew P.; Melack, John M.; Lefenfeld, Michael

    2015-08-11

    Systems, devices, and methods combine thermally stable reactant materials and aqueous solutions to generate hydrogen and a non-toxic liquid by-product. The reactant materials can sodium silicide or sodium silica gel. The hydrogen generation devices are used in fuels cells and other industrial applications. One system combines cooling, pumping, water storage, and other devices to sense and control reactions between reactant materials and aqueous solutions to generate hydrogen. Springs and other pressurization mechanisms pressurize and deliver an aqueous solution to the reaction. A check valve and other pressure regulation mechanisms regulate the pressure of the aqueous solution delivered to the reactant fuel material in the reactor based upon characteristics of the pressurization mechanisms and can regulate the pressure of the delivered aqueous solution as a steady decay associated with the pressurization force. The pressure regulation mechanism can also prevent hydrogen gas from deflecting the pressure regulation mechanism.

  8. The fabrication of metal silicide nanodot arrays using localized ion implantation

    Energy Technology Data Exchange (ETDEWEB)

    Han, Jin; Kim, Tae-Gon; Min, Byung-Kwon; Lee, Sang Jo, E-mail: bkmin@yonsei.ac.kr [School of Mechanical Engineering, Yonsei University, Seoul 120-749 (Korea, Republic of)

    2010-12-03

    We propose a process for fabricating nanodot arrays with a pitch size of less than 25 nm. The process consists of localized ion implantation in a metal thin film on a Si wafer using a focused ion beam (FIB), followed by chemical etching. This process utilizes the etching resistivity changes of the ion beam irradiated region that result from metal silicide formation by ion implantation. To control the nanodot diameter, a threshold ion dose model is proposed using the Gaussian distribution of the ion beam intensities. The process is verified by fabricating nanodots with various diameters. The mechanism of etching resistivity is investigated via x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES).

  9. Chemical vapour deposition of tungsten and tungsten silicide layers for applications in novel silicon technology

    CERN Document Server

    Li, F X

    2002-01-01

    This work was a detailed investigation into the Chemical Vapour Deposition (CVD) of tungsten and tungsten silicide for potential applications in integrated circuit (IC) and other microelectronic devices. These materials may find novel applications in contact schemes for transistors in advanced ICs, buried high conductivity layers in novel Silicon-On-Insulator (SOI) technology and in power electronic devices. The CVD techniques developed may also be used for metal coating of recessed or enclosed features which may occur in novel electronic or electromechanical devices. CVD of tungsten was investigated using the silicon reduction reaction of WF sub 6. W layers with an optimum self-limiting thickness of 100 nm and resistivity 20 mu OMEGA centre dot cm were produced self-aligned to silicon. A hydrogen passivation technique was developed as part of the wafer pre-clean schedule and proved essential in achieving optimum layer thickness. Layers produced by this approach are ideal for intimate contact to shallow junct...

  10. Fabrication of uranium silicide dispersion fuel by atomization for research reactor

    International Nuclear Information System (INIS)

    Atomizing technology has been developed to eliminate the difficulties in comminution of the tough U3Si and to take advantage of the spherical shape and the rapid solidification. The comparison between the conventional dispersion fuel with comminuted powder and the newly developed fuel with atomized powder has been made. As a result, the processes, powdering uranium silicide and heat treatment to U3Si, become simplified. The extruding pressure of blended powder with atomized powder was lower than that of blended powder with comminuted powder. The elongation of the atomization processed fuel meat was much higher than that of comminution processed fuel meats. It appears that the loading density of U3Si in fuel meat can be increased by using atomized U3Si powder. The thermal conductivity and the thermal compatibility of fuel meat have been investigated and found to be much improved due to the spherical shape of atomized powder. (author)

  11. Discovery of Brownleeite: a New Manganese Silicide Mineral in an Interplanetary Dust Particle

    Science.gov (United States)

    Keller, Lindsay P.; Nakamura-Messenger, Keiko; Clemett, Simon J.; Messenger, Scott; Jones, John H.; Palma, Russell L.; Pepin, Robert O.; Klock, Wolfgang; Zolensky, Michael E.; Tatsuoka, Hirokazu

    2011-01-01

    The Earth accretes approximately 40,000 tons of cosmic dust annually, originating mainly from the disintegration of comets and collisions among asteroids. This cosmic dust, also known as interplanetary dust particles (IDPs), is a subject of intense interest since it is made of the original building blocks of our Solar System. Although the specific parent bodies of IDPs are unknown, the anhydrous chondritic-porous IDPs (CP-IDPs) subset has been potentially linked to a cometary source. The CP-IDPs are extremely primitive materials based on their unequilibrated mineralogy, C-rich chemistry, and anomalous isotopic signatures. In particular, some CP-IDPs escaped the thermal, aqueous and impact shock processing that has modified or destroyed the original mineralogy of meteorites. Thus, the CP-IDPs represent some of the most primitive solar system materials available for laboratory study. Most CP-IDPs are comprised of minerals that are common on Earth. However, in the course of an examination of one of the CP-IDPs, we encountered three sub-micrometer sized grains of manganese silicide (MnSi), a phase that has heretofore not been found in nature. In the seminar, we would like to focus on IDP studies and this manganese silicide phase that has been approved as the first new mineral identified from a comet by the International Mineralogical Association (IMA) in 2008. The mineral is named in honour of Donald E. Brownlee, an American astronomer and a founder of the field of cosmic dust research who is the principal investigator of the NASA Stardust Mission that collected dust samples from Comet 81P/Wild-2 and returned them to Earth. Much of our current view and understanding of the early solar system would not exist without the pioneering work of professor Don Brownlee in the study of IDPs.

  12. A thermodynamic study of actinide oxide targets/fuels for americium transmutation

    International Nuclear Information System (INIS)

    A thermodynamic study was performed on the systems Am-O, AmOx-MgO, AmOx-MgAl2O4, Pu-Mg-O and U-Mg-O. Both experimental work (X-ray analyses, oxygen potential measurements etc.) and calculations on the phase diagrams involved were made. The reaction between americium oxide and spinel is expected to form the compound AmAlO3. Isothermal sections have been calculated for AmOx-(MgO, Al2O3), Pu-Mg-O and U-Mg-O at 2000 K using the software package ''Thermo-Calc''. Thermodynamic equilibrium data were used to predict the behaviour of actinide oxides in a reactor. The implication of the results for the technological application is discussed, with emphasis on the effects of the high oxygen potential of AmO2 as compared to the conventional fuel, i.e. UO2. (author)

  13. The uptake of plutonium-239, 240, americium-241, strontium-90 into plants

    International Nuclear Information System (INIS)

    This report describes the results of measurements on the uptake of plutonium, americium, strontium-90 and caesium-137 into peas, beet, oats, sweet corn, tomatoes and vegetable marrow grown in tubs containing radioactively-contaminated silts. The silts had been taken from an area of West Cumbria commonly referred to as the Ravenglass estuary. The experiments are categorised as being carried out under non-standard conditions because of the manner in which the radioactivity came to be incorporated into the growth medium. The growth medium was representative of conditions which could arise when the estuarine silt moves inland under the influence of wind and tide and mixes with the adjacent farm land. The silt had been contaminated by radioactive effluents from the nuclear fuels reprocessing plant at Sellafield and this contamination had been brought about by natural means. (Auth.)

  14. Complex formation of trivalent americium with salicylic acid at very low concentrations

    International Nuclear Information System (INIS)

    For the first time, the complexation of americium(III) with salicylic acid was studied at trace metal concentrations using a 2.0 m Long Path Flow Cell for UV-vis spectroscopy. The detection limit of Am(III) in aqueous solution at pH 3.0 was found to be 5 x 10-9 M. Two Am(III)-salicylate complexes were formed at pH 5.0 in 0.1 M NaClO4, indicated by a clear red shift of the absorption maximum. The absorption spectra obtained from spectrophotometric titration were analyzed by means of factor analysis and complex stabilities were calculated to be log β110 = 2.56 ± 0.08 and log β120 = 3.93 ± 0.19. (author)

  15. Standard practice for The separation of americium from plutonium by ion exchange

    CERN Document Server

    American Society for Testing and Materials. Philadelphia

    2001-01-01

    1.1 This practice describes the use of an ion exchange technique to separate plutonium from solutions containing low concentrations of americium prior to measurement of the 241Am by gamma counting. 1.2 This practice covers the removal of plutonium, but not all the other radioactive isotopes that may interfere in the determination of 241Am. 1.3 This practice can be used when 241Am is to be determined in samples in which the plutonium is in the form of metal, oxide, or other solid provided that the solid is appropriately sampled and dissolved (See Test Methods C758, C759, and C1168). 1.4 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

  16. Transportability Class of Americium in K Basin Sludge under Ambient and Hydrothermal Processing Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Delegard, Calvin H.; Schmitt, Bruce E.; Schmidt, Andrew J.

    2006-08-01

    This report establishes the technical bases for using a ''slow uptake'' instead of a ''moderate uptake'' transportability class for americium-241 (241Am) for the K Basin Sludge Treatment Project (STP) dose consequence analysis. Slow uptake classes are used for most uranium and plutonium oxides. A moderate uptake class has been used in prior STP analyses for 241Am based on the properties of separated 241Am and its associated oxide. However, when 241Am exists as an ingrown progeny (and as a small mass fraction) within plutonium mixtures, it is appropriate to assign transportability factors of the predominant plutonium mixtures (typically slow) to the Am241. It is argued that the transportability factor for 241Am in sludge likewise should be slow because it exists as a small mass fraction as the ingrown progeny within the uranium oxide in sludge. In this report, the transportability class assignment for 241Am is underpinned with radiochemical characterization data on K Basin sludge and with studies conducted with other irradiated fuel exposed to elevated temperatures and conditions similar to the STP. Key findings and conclusions from evaluation of the characterization data and published literature are summarized here. Plutonium and 241Am make up very small fractions of the uranium within the K Basin sludge matrix. Plutonium is present at about 1 atom per 500 atoms of uranium and 241Am at about 1 atom per 19000 of uranium. Plutonium and americium are found to remain with uranium in the solid phase in all of the {approx}60 samples taken and analyzed from various sources of K Basin sludge. The uranium-specific concentrations of plutonium and americium also remain approximately constant over a uranium concentration range (in the dry sludge solids) from 0.2 to 94 wt%, a factor of {approx}460. This invariability demonstrates that 241Am does not partition from the uranium or plutonium fraction for any characterized sludge matrix. Most

  17. Oxidation-resistant Ge-doped silicide coating on Cr-Cr2Nb alloys by pack cementation

    International Nuclear Information System (INIS)

    The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating on Cr-Cr2Nb alloys in a single processing step. The morphology and composition of the coating depended both on the pack composition and processing schedule and also on the composition and microstructure of the substrate. Higher Ge content in the pack suppressed the formation of CrSi2 and reduced the growth kinetics of the coating. Ge was not homogeneously distributed in the coatings. Under cyclic and isothermal oxidation conditions, the Ge-doped silicide coating protected the Cr-Nb alloys from significant oxidation and from pesting by the formation of a Ge-doped silica film. (orig.)

  18. Effect of P+ ions on the microstructure and the nature of the formed silicides in the Cr/Si system

    International Nuclear Information System (INIS)

    The effect of the phosphorus on the microstructure and on the nature of the formed silicide in the annealed Cr/Si system is studied. The chromium layer is deposited by electron gun evaporation on the undoped and P+ doped monocrystalline silicon. Cross-sectional transmission electron microscopy (XTEM) investigation of the samples, annealed at 475 deg. C for different times, shows that the presence of phosphorus leads to the formation of CrSi2 disilicide, free of defects, and Cr3Si silicide for lower and higher annealing times, respectively. In the case of undoped substrate the formed CrSi2 disilicide is stable and contains a high concentration of stacking faults when the chromium is partially consumed

  19. Production Cycle for Large Scale Fission Mo-99 Separation by the Processing of Irradiated LEU Uranium Silicide Fuel Element Targets

    OpenAIRE

    Abdel-Hadi Ali Sameh

    2013-01-01

    Uranium silicide fuels proved over decades their exceptional qualification for the operation of higher flux material testing reactors with LEU elements. The application of such fuels as target materials, particularly for the large scale fission Mo-99 producers, offers an efficient and economical solution for the related facilities. The realization of such aim demands the introduction of a suitable dissolution process for the applied U3Si2 compound. Excellent results are achieved by the oxidiz...

  20. Dimensional stability of low enriched uranium silicide plate-type fuel for research reactors at transient conditions

    International Nuclear Information System (INIS)

    This paper describes the result of transient experiments using low enriched uranium silicide plate-type fuel for research reactors. The pulse irradiation was carried out at Nuclear Safety Research Reactor (NSRR) in Japan Atomic Energy Research Institute. The results obtained were: (1) At fuel plate temperature of below 400degC, a good dimensional stability of the tested fuel was kept. No fuel failure occurred. (2) At a plate temperature of about 540degC, a local crack was initiated on the Al-3% Mg alloy cladding. Once the cladding temperature exceeded the melting point of 640degC, the fuel plate was degraded much by increased bowing and cracking of the denuded fuel meat occurred after relocation of molten Al cladding. Despite of these degradation, neither fragmentation of the fuel plate nor mechanical energy generation occurred up to the cladding temperature of 971degC. (3) At the temperatures of around 925degC, the reaction of silicide particles with molten Al in the matrix and that of cladding occurred, forming Al riched U (Al, Si) compounds and Si riched (U, Si) compounds at the outermost surface of the silicide particles. (author)

  1. Pack cementation Cr-Al coating of steels and Ge-doped silicide coating of Cr-Nb alloy

    Energy Technology Data Exchange (ETDEWEB)

    He, Y.R.; Zheng, M.H.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States)

    1995-08-01

    Carbon steels or low-alloy steels used in utility boilers, heat exchangers, petrochemical plants and coal gasification systems are subjected to high temperature corrosion attack such as oxidation, sulfidation and hot corrosion. The pack cementation coating process has proven to be an economical and effective method to enhance the corrosion resistance by modifying the surface composition of steels. With the aid of a computer program, STEPSOL, pack cementation conditions to produce a ferrite Cr-Al diffusion coating on carbon-containing steels by using elemental Cr and Al powders have been calculated and experimentally verified. The cyclic oxidation kinetics for the Cr-Al coated steels are presented. Chromium silicide can maintain high oxidation resistance up to 1100{degrees}C by forming a SiO{sub 2} protective scale. Previous studies at Ohio State University have shown that the cyclic oxidation resistance of MOSi{sub 2} and TiSi{sub 2} can be further improved by Ge addition introduced during coating growth. The halide-activated pack cementation process was modified to produce a Ge-doped silicide diffusion coating in a single processing step for the ORNL-developed Cr-Nb advanced intermetallic alloy. The oxidation behavior of the silicide-coated Cr-Nb alloy was excellent: weight gain of about 1 mg/cm{sup 2} upon oxidation at 1100{degrees}C in air for 100 hours.

  2. The behaviour under irradiation of molybdenum matrix for inert matrix fuel containing americium oxide (CerMet concept)

    Science.gov (United States)

    D'Agata, E.; Knol, S.; Fedorov, A. V.; Fernandez, A.; Somers, J.; Klaassen, F.

    2015-10-01

    Americium is a strong contributor to the long term radiotoxicity of high activity nuclear waste. Transmutation by irradiation in nuclear reactors or Accelerator Driven System (ADS, subcritical reactors dedicated to transmutation) of long-lived nuclides like 241Am is therefore an option for the reduction of radiotoxicity of waste packages to be stored in a repository. In order to safely burn americium in a fast reactor or ADS, it must be incorporated in a matrix that could be metallic (CerMet target) or ceramic (CerCer target). One of the most promising matrix to incorporate Am is molybdenum. In order to address the issues (swelling, stability under irradiation, gas retention and release) of using Mo as matrix to transmute Am, two irradiation experiments have been conducted recently at the High Flux Reactor (HFR) in Petten (The Netherland) namely HELIOS and BODEX. The BODEX experiment is a separate effect test, where the molybdenum behaviour is studied without the presence of fission products using 10B to "produce" helium, the HELIOS experiment included a more representative fuel target with the presence of Am and fission product. This paper covers the results of Post Irradiation Examination (PIE) of the two irradiation experiments mentioned above where molybdenum behaviour has been deeply investigated as possible matrix to transmute americium (CerMet fuel target). The behaviour of molybdenum looks satisfying at operating temperature but at high temperature (above 1000 °C) more investigation should be performed.

  3. Consideration of the effect of lymph-node deposition upon the measurement of plutonium and americium in the lungs

    International Nuclear Information System (INIS)

    Measurement of an inhaled radionuclide by external photon counting includes quantities which may be contained in lymph nodes, as well as quantities in the lungs. An overestimate of the lung burden can result, if a portion of the radionuclide were present in the lymph nodes. This problem is analyzed with respect to the measurement of inhaled plutonium containing plutonium-241 and americium-241, when americium-241 has been used as a tracer for the plutonium. Equations are derived which yield the amounts of americium and of plutonium in the lungs and in the lymph nodes as a function of time after exposure and for various translocation and retention parameters. Count histories (count profiles) of actual exposure cases are compared with calculated count profiles in order to gain insight into possible values of the translocation and retention parameters. Comparison is also made with calculated count profiles using values of translocation and retention parameters recommended by the International Commission on Radiological Protection (ICRP) for use with the Task Group Lung Model. The magnitude of the possible overestimate (error factor) was calculated for combinations o

  4. HELIOS: the new design of the irradiation of U-free fuels for americium transmutation

    Energy Technology Data Exchange (ETDEWEB)

    D' Agata, E. [European Commission, Joint Research Centre, Institute for Energy, P.O. Box 2, 1755 ZG Petten (Netherlands); Klaassen, F.; Sciolla, C. [Nuclear Research and Consultancy Group, Dept. Life Cycle and Innovations, P.O. Box 25 1755 ZG Petten (Netherlands); Fernandez-Carretero, A. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, 76125 Karlsruhe (Germany); Bonnerot, J.M. [Commissariat a l' Energie Atomique, DEC/SESC/LC2I CEA-Cadarache, 13108 St. Paul lez Durance Cedex (France)

    2009-06-15

    Americium is one of the radioactive elements that mostly contribute to the radiotoxicity of the nuclear spent fuel. Transmutation of long-lived nuclides like Americium is an option for the reduction of the mass, the radiotoxicity and the decay heat of nuclear waste. The HELIOS irradiation experiment is the last evolution in a series of experiments on americium transmutation. The previous experiments, EFTTRA-T4 and T4bis, have shown that the release or trapping of helium is the key issue for the design of such kind of target. In fact, the production of helium, which is characteristic of {sup 241}Am transmutation, is quite significant. The experiment is carried out in the framework of the 4-year project EUROTRANS of the EURATOM 6. Framework Programme (FP6). Therefore, the main objective of the HELIOS experiment is to study the in-pile behaviour of U-free fuels such as CerCer (Pu, Am, Zr)O{sub 2} and Am{sub 2}Zr{sub 2}O{sub 7}+MgO or CerMet (Pu, Am)O{sub 2}+Mo in order to gain knowledge on the role of the fuel microstructure and of the temperature on the gas release and on the fuel swelling. The experiment was planned to be conducted in the HFR (High Flux Reactor) in Petten (The Netherlands) starting the first quarter of 2007. Because of the innovative aspects of the fuel, the fabrication has had some delays as well as the final safety analyses of the original design showed some unexpected deviation. Besides, the HFR reactor has been unavailable since August 2008. Due to the reasons described above, the experiment has been postponed. HELIOS should start in the first quarter of 2009 and will last 300 full power days. The paper will cover the description of the new design of the irradiation experiment HELIOS. The experiment has been split in two parts (HELIOS1 and HELIOS2) which will be irradiated together. Moreover, due to the high temperature achieved in cladding and to the high amount of helium produced during transmutation the experiment previously designed for a

  5. Rate Theory Modeling and Simulations of Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States); Ye, Bei [Argonne National Lab. (ANL), Argonne, IL (United States); Mei, Zhigang [Argonne National Lab. (ANL), Argonne, IL (United States); Hofman, Gerard [Argonne National Lab. (ANL), Argonne, IL (United States); Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States)

    2015-12-10

    Uranium silicide (U3Si2) fuel has higher thermal conductivity and higher uranium density, making it a promising candidate for the accident-tolerant fuel (ATF) used in light water reactors (LWRs). However, previous studies on the fuel performance of U3Si2, including both experimental and computational approaches, have been focusing on the irradiation conditions in research reactors, which usually involve low operation temperatures and high fuel burnups. Thus, it is important to examine the fuel performance of U3Si2 at typical LWR conditions so as to evaluate the feasibility of replacing conventional uranium dioxide fuel with this silicide fuel material. As in-reactor irradiation experiments involve significant time and financial cost, it is appropriate to utilize modeling tools to estimate the behavior of U3Si2 in LWRs based on all those available research reactor experimental references and state-of-the-art density functional theory (DFT) calculation capabilities at the early development stage. Hence, in this report, a comprehensive investigation of the fission gas swelling behavior of U3Si2 at LWR conditions is introduced. The modeling efforts mentioned in this report was based on the rate theory (RT) model of fission gas bubble evolution that has been successfully applied for a variety of fuel materials at devious reactor conditions. Both existing experimental data and DFT-calculated results were used for the optimization of the parameters adopted by the RT model. Meanwhile, the fuel-cladding interaction was captured by the coupling of the RT model with simplified mechanical correlations. Therefore, the swelling behavior of U3Si2 fuel and its consequent interaction with cladding in LWRs was predicted by the rate theory modeling, providing valuable information for the development of U3Si2 fuel as an accident

  6. Anomalous aryl strengthening of complexes at americium and europium extraction with alkylenediphospine dioxide from perchloric media

    International Nuclear Information System (INIS)

    Studied was the extraction of americium(3) and europium(3) from perchlorate solutions(0.001 M) with dioxides of alkylenediphosphines of three types: aryl Ph2P(O)CH2(O)PPh2(briefly 4P), and Ph2P(O)(CH2)2(O)PPh2, mixed Ph2P(O)CH2(O)P(C8H17)2 (or 2Ph2Oct) and alkyl (C8H17)2P(O)CH2(O)P(C8H17)2 (or 4 Oct). Trisolvates of MeS3x(ClO4)3 are predominantly formed but americium disolvates are also present upon dilution with dichloroethane. For 4Ph,2Ph2Oct and 4 Oct the concentration is, respectively, 1015, 2x1014, and 1013; for disolvates by 4 orders of magnitude lower which is, nevertheless, by 2 orders of magnitude higher than for nitric acid solutions. The separation coefficient of β Am/Eu for 4Ph attains 6-8. As in the case of nitrate solutions, an anomalous aryl strengthening of the complexes is observed: an increase in the distribution coefficients and extraction constants in the series of 4 Oct - 2Ph 2 Oct - 4Ph, in spite of the introduction of electronegative aryl substituents into the dioxide molecule, which reduce electron density on oxygen atoms and basicity of dioxides. In contrast to nitric acid solutions, observed is a nonlinear effect of a change in basicity on extraction properties upon dilution with dichloroethane (dioxide of 2Ph2 Oct does not occupy an intermediate position but is close to 4Ph). Upon dilution with chloroform the dependence is linear and anomalous effect rises due to a different nature of interactions of dioxides with chloroform. When the bridge increases up to ethylene, an anomalous strengthening of the complexes disappears. However, the distribution coefficients upon extraction with alkyl dioxide are considerably lower, which can be explained by a stronger extraction of perchloric acid

  7. Characterization of novel heterophasic powdered silicide-type material for high-temperature protection systems

    International Nuclear Information System (INIS)

    Novel multicomponent heterophasic powdered material of silicide-type is presented. The powdered material is intended for forming high-temperature protective multifunction coatings able to protect different hot-loaded structural elements of aerospace industry from refractory metals alloys under severe oxidizing conditions in high-enthalpy and super/hypersonic oxygen-containing gas flows. The powdered material base on complexly composition of Si-Ti-Mo system modified with B,Y,W. Technological conception of its obtaining and powder making process are examined. The powders were worked out in accordance with early performed functional structural model of special materials for coatings with the increased self-healing ability. The coatings can be deposited from the specially prepared abovementioned powders by plasma spraying processes or any one of other coating methods ensuring the conservation of morphological peculiarities of microstructure and phase composition of powdered material (detonation spraying technique, from slurry ...). Finally the results of some properties of novel heterophasic silicidetype powders and some properties of protective coating deposited on the niobium base alloys by means of plasma spraying technique are presented. (author)

  8. Burnup determination of silicide MTR fuel elements (20% 235U) in the LFR laboratory

    International Nuclear Information System (INIS)

    The LFR facility is a radiochemical laboratory designed and constructed with a hot-cells line, a glove-box and a fume hood, all of them suited to work radioactive materials. At the beginning of the LFR operation a series of dissolutions of MTR irradiated silicide fuel elements was performed, and determined its isotopic composition of 235U, 239Pu and 148Nd (the last one as burn up monitor), by the thermal ionization mass spectrometry (TIMS). These assays are linked to the IAEA RLA/4/018 Regional Project 'Management of Spent Fuel from Research Reactors'. It is concluded that this technique of burn up measurement is powerful and accurate when properly applied, and permit to validate the calculation codes when isotopic dilution is performed. It is worth noticed the LFR capacity to carry on different research and development programs in the nuclear fuel cycle field, such as the previously mentioned absolute burn up measurements, or the evaluation of radioactive waste immobilization processes and researches on burnable poisons. (author)

  9. The ability of silicide coating to delay the catastrophic oxidation of vanadium under severe conditions

    Science.gov (United States)

    Chaia, N.; Mathieu, S.; Rouillard, F.; Vilasi, M.

    2015-02-01

    V-4Cr-4Ti vanadium alloy is a potential cladding material for sodium-cooled fast-neutron reactors (SFRs). However, its affinity for oxygen and the subsequent embrittlement that oxygen induces causes a need for an oxygen diffusion barrier, which can be obtained by manufacturing a multi-layered silicide coating. The present work aims to evaluate the effects of thermal cycling (using a cyclic oxidation device) and tensile and compressive stresses (using the three-point flexure test) on the coated alloy system. Tests were performed in air up to 1100 °C, which is 200 °C higher than the accidental temperature for SFR applications. The results showed that the VSi2 coating was able to protect the vanadium substrate from oxidation for more than 400 1-h cycles between 1100 °C and room temperature. The severe bending applied to the coated alloy at 950 °C using a load of 75 MPa did not lead to specimen breakage. It can be suggested that the VSi2 coating has mechanical properties compatible with the V-4Cr-4Ti alloy for SFR applications.

  10. The whole-core LEU silicide fuel demonstration in the JMTR

    Energy Technology Data Exchange (ETDEWEB)

    Aso, Tomokazu; Akashi, Kazutomo; Nagao, Yoshiharu [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)] [and others

    1997-08-01

    The JMTR was fully converted to LEU silicide (U{sub 3}Si{sub 2}) fuel with cadmium wires as burnable absorber in January, 1994. The reduced enrichment program for the JMTR was initiated in 1979, and the conversion to MEU (enrichment ; 45%) aluminide fuel was carried out in 1986 as the first step of the program. The final goal of the program was terminated by the present LEU conversion. This paper describes the results of core physics measurement through the conversion phase from MEU fuel core to LEU fuel core. Measured excess reactivities of the LEU fuel cores are mostly in good agreement with predicted values. Reactivity effect and burnup of cadmium wires, therefore, were proved to be well predicted. Control rod worth in the LEU fuel core is mostly less than that in the MEU fuel core. Shutdown margin was verified to be within the safety limit. There is no significant difference in temperature coefficient of reactivity between the MEU and LEU fuel cores. These results verified that the JMTR was successfully and safely converted to LEU fuel. Extension of the operating cycle period was achieved and reduction of spend fuel elements is expected by using the fuel with high uranium density.

  11. Status of core conversion with LEU silicide fuel in JRR-4

    Energy Technology Data Exchange (ETDEWEB)

    Nakajima, Teruo; Ohnishi, Nobuaki; Shirai, Eiji [Japan Atomic Energy Research Institute, Ibaraki-ken (Japan)

    1997-08-01

    Japan Research Reactor No.4 (JRR-4) is a light water moderated and cooled, 93% enriched uranium ETR-type fuel used and swimming pool type reactor with thermal output of 3.5MW. Since the first criticality was achieved on January 28, 1965, JRR-4 has been used for shielding experiments, radioisotope production, neutron activation analyses, training for reactor engineers and so on for about 30 years. Within the framework of the RERTR Program, the works for conversion to LEU fuel are now under way, and neutronic and thermal-hydraulic calculations emphasizing on safety and performance aspects are being carried out. The design and evaluation for the core conversion are based on the Guides for Safety Design and Evaluation of research and testing reactor facilities in Japan. These results show that the JRR-4 will be able to convert to use LEU fuel without any major design change of core and size of fuel element. LEU silicide fuel (19.75%) will be used and maximum neutron flux in irradiation hole would be slightly decreased from present neutron flux value of 7x10{sup 13}(n/cm{sup 2}/s). The conversion works are scheduled to complete in 1998, including with upgrade of the reactor building and utilization facilities.

  12. Experimental studies of thermal and chemical interactions between oxide and silicide nuclear fuels with water

    Energy Technology Data Exchange (ETDEWEB)

    farahani, A.A.; Corradini, M.L. [Univ. of Wisconsi, Madison, WI (United States)

    1995-09-01

    Given some transient power/cooling mismatch is a nuclear reactor and its inability to establish the necessary core cooling, energetic fuel-coolant interactions (FCI`s commonly called `vapor explosions`) could occur as a result of the core melting and coolant contact. Although a large number of studies have been done on energetic FCI`s, very few experiments have been performed with the actual fuel materials postulated to be produced in severe accidents. Because of the scarcity of well-characterized FCI data for uranium allows in noncommercial reactors (cermet and silicide fuels), we have conducted a series of experiments to provide a data base for the foregoing materials. An existing 1-D shock-tube facility was modified to handle depleted radioactive materials (U{sub 3}O{sub 8}-Al, and U{sub 3}Si{sub 2}-Al). Our objectives have been to determine the effects of the initial fuel composition and temperature and the driving pressure (triggering) on the explosion work output, dynamic pressures, transient temperatures, and the hydrogen production. Experimental results indicate limited energetics, mainly thermal interactions, for these fuel materials as compared to aluminum where more chemical reactions occur between the molten aluminum and water.

  13. Oxidation behavior of niobium aluminide intermetallics protected by aluminide and silicide diffusion coatings

    International Nuclear Information System (INIS)

    The isothermal and cyclic oxidation behavior of a new class of damage-tolerant niobium aluminide (Nb3Al-xTi-yCr) intermetallics is studied between 650 C and 850 C. Protective diffusion coatings were deposited by pack cementation to achieve the siliciding or aluminizing of substrates with or without intervening Mo or Ni layers, respectively. The compositions and microstructures of the resulting coatings and oxidized surfaces were characterized. The isothermal and cyclic oxidation kinetics indicate that uncoated Nb-40Ti-15Al-based intermetallics may be used up to ∼750 C. Alloying with Cr improves the isothermal oxidation resistance between 650 C and 850 C. The most significant improvement in oxidation resistance is achieved by the aluminization of electroplated Ni interlayers. The results suggest that the high-temperature limit of niobium aluminide-based alloys may be increased to 800 C to 850 C by aluminide-based diffusion coatings on ductile Ni interlayers. Indentation fracture experiments also indicate that the ductile nickel interlayers are resistant to crack propagation in multilayered aluminide-based coatings

  14. Crystal structure of the ternary silicide Gd2Re3Si5

    Directory of Open Access Journals (Sweden)

    Vitaliia Fedyna

    2014-12-01

    Full Text Available A single crystal of the title compound, the ternary silicide digadolinium trirhenium pentasilicide, Gd2Re3Si5, was isolated from an alloy of nominal composition Gd20Re30Si50 synthesized by arc melting and investigated by X-ray single-crystal diffraction. Its crystal structure belongs to the U2Mn3Si5 structure type. All atoms in the asymmetric lie on special positions. The Gd site has site symmetry m..; the two Mn atoms have site symmetries m.. and 2.22; the three Si atoms have site symmetries m.., ..2 and 4.. . The coordination polyhedra of the Gd atoms have 21 vertices, while those of the Re atoms are cubooctahedra and 13-vertex polyhedra. The Si atoms are arranged as tricapped trigonal prisms, bicapped square antiprisms, or 11-vertex polyhedra. The crystal structure of the title compound is also related to the structure types CaBe2Ge2 and W5Si3. It can be represented as a stacking of Gd-centred polyhedra of composition [GdSi9]. The Re atoms form infinite chains with an Re—Re distance of 2.78163 (5 Å and isolated squares with an Re—Re distance of 2.9683 (6 Å.

  15. The Comparison Of Silicon Analysis For The Uranium Silicide Fuel Using Spectrophotometrical And Gravimetrical Methods

    International Nuclear Information System (INIS)

    The analysis of silicon content in the uranium silicide fuel spectro-photometrical and gravimetrical method have been performed. The nitrous oxide-acetylene was used in the atomic absorption spectrophotometry (AAS) on the wave length of 251.6 nm, and the mixture of ammonium hepta molybdate complexes and SnC12 as reductor were applied during analysis by UV-VIS spectrophotometry (UV-VIS) on the wave length of 757.5 mm. The reagent of HCLO4 and HNO3 were used for determining Si content by gravimetrical methods. The results of this comparison is as follows: the accuracy result is around 96.37 % + 0.24 % for the Si concentration up to 300 ppm (the AAS), is 138.60 % = 0.43 % for the Si concentration range between 0.1-1.5 ppm (UV-VIS), and is 51.13 % + 0.8 % for 1 gram of Si (gravimetry). The results also show that the lowest analytical error is obtained by AAS method

  16. Americium-based oxides: Dense pellet fabrication from co-converted oxalates

    Energy Technology Data Exchange (ETDEWEB)

    Horlait, Denis; Lebreton, Florent [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze (France); Gauthé, Aurélie [CEA, DEN, DRCP/SERA/LCAR, 30207 Bagnols-sur-Cèze (France); Caisso, Marie [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze (France); Arab-Chapelet, Bénédicte; Picart, Sébastien [CEA, DEN, DRCP/SERA/LCAR, 30207 Bagnols-sur-Cèze (France); Delahaye, Thibaud, E-mail: thibaud.delahaye@cea.fr [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze (France)

    2014-01-15

    Mixed oxides are used as nuclear fuels and are notably envisaged for future fuel cycles including plutonium and minor actinide recycling. In this context, processes are being developed for the fabrication of uranium–americium mixed-oxide compounds for transmutation. The purpose of these processes is not only the compliance with fuel specifications in terms of density and homogeneity, but also the simplification of the process for its industrialization as well as lowering dust generation. In this paper, the use of a U{sub 0.85}Am{sub 0.15}O{sub 2±δ} powder synthesized by oxalate co-conversion as a precursor for dense fuel fabrications is assessed. This study notably focuses on sintering, which yielded pellets up to 96% of the theoretical density, taking advantage of the high reactivity and homogeneity of the powder. As-obtained pellets were further characterized to be compared to those obtained via processes based on the UMACS (Uranium Minor Actinide Conventional Sintering) process. This comparison highlights several advantages of co-converted powder as a precursor for simplified processes that generate little dust.

  17. Study of biosorbents application on the treatment of radioactive liquid wastes with americium-241

    International Nuclear Information System (INIS)

    The use of nuclear energy for many different purposes has been intensified and highlighted by the benefits that it provides. Medical diagnosis and therapy, agriculture, industry and electricity generation are examples of its application. However, nuclear energy generates radioactive wastes that require suitable treatment ensuring life and environmental safety. Biosorption and bioaccumulation represent an emergent alternative for the treatment of radioactive liquid wastes, providing volume reduction and physical state change. This work aimed to study biosorbents for the treatment of radioactive liquid wastes contaminated with americium-241 in order to reduce the volume and change the physical state from liquid to solid. The biosorbents evaluated were Saccharomyces cerevisiae immobilized in calcium alginate beads, inactivated and free cells of Saccharomyces cerevisiae, calcium alginate beads, Bacillus subtilis, Cupriavidus metallidurans and Ochrobactrum anthropi. The results were quite satisfactory, achieving 100% in some cases. The technique presented in this work may be useful and viable for implementing at the Waste Management Laboratory of IPEN - CNEN/SP in short term, since it is an easy and low cost method. (author)

  18. Mutual separation of americium(III) and europium(III) using glycolamic acid and thioglycolamic acid

    Energy Technology Data Exchange (ETDEWEB)

    Suneesh, A.S.; Venkatesan, K.A.; Syamala, K.V.; Antony, M.P.; Vasudeva Rao, P.R. [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Fuel Chemistry Div.

    2012-07-01

    The extractants, bis(2-ethylhexyl)diglycolamicacid (HDEHDGA) and bis(2-ethylhexy)thiodiglycolamic acid (HDEHSDGA) were synthesized and characterized by {sup 1}H and {sup 13}C NMR, mass and IR spectroscopy. The extraction behaviour of {sup (152+154})Eu(III) and {sup 241}Am(III) from nitric acid medium by a solution of HDEHDGA (or HDEHSDGA) in n-dodecane (n-DD) was studied for the mutual separation of actinides and lanthanides. The effect of various parameters such as the pH, concentrations of HDEHDGA, HDEHSDGA, sodium nitrate, N,N,N',N'-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN) and diethylenetriaminepentaacetic acid (DTPA) on the separation factor (SF) of americium(III) over europium(III) and vice versa was studied, and the conditions needed for the preferential separation were optimised. The results show that HDEHDGA exhibits higher extraction for {sup (152+154)}Eu(III) and HDEHSDGA shows the superior selectivity for {sup 241}Am(III). (orig.)

  19. Determination of plutonium americium and curium in soil samples by solvent extraction with trioctylphosphine oxide

    International Nuclear Information System (INIS)

    A method of Pu, Am and Cm determination in soil samples, which was developed for analyzing samples from territories subjected to radioactive contamination as a result of the Chernobyl accident is described. After preliminary treatment the samples were leached by solution of 7 mol/l HNO23+0.3 mol/l KBrO3 during heating. Pu was isolated by extraction with 0.05 mol TOPO from 7 mol/l HNO3. 144Ce and partially remaining in water phase isotopes of Zr, U and Th were isolated in an extraction-chromatographic column with TOPO and PbO2. Then Am and Cm were extracted by 0.2 mol/l TOPO from solution 1 mol/l HLact+0.07 mol/l DTPA+1 mol/l Al(NO3)3. Alpha-activity of both extracted products was determined in liquid scintillation counter. Chemical yield of plutonium counted to 85±10%, that of americium and curium -75±10%. 17 refs

  20. Development and Testing of an Americium/Lanthanide Separation Flowsheet Using Sodium Bismuthate

    Energy Technology Data Exchange (ETDEWEB)

    Jack Law; Bruce Mincher; Troy Garn; Mitchell Greenhalgh; Nicholas Schmitt; Veronica Rutledge

    2014-04-01

    The separation of Am from the lanthanides and curium is a key step in proposed advanced fuel cycle scenarios. The partitioning and transmutation of Am is desirable to minimize the long-term heat load of material interred in a future high-level waste repository. A separation process amenable to process scale-up remains elusive. Given only subtle chemistry differences within and between the ions of the trivalent actinide and lanthanide series this separation is challenging ; however, higher oxidation states of americium can be prepared using sodium bismuthate and separated via solvent extraction using diamylamylphosphonate (DAAP) extraction. Among the other trivalent metals only Ce is also oxidized and extracted. Due to the long-term instability of Am(VI) , the loaded organic phase is readily selectively stripped to partition the actinide to a new acidic aqueous phase. Batch extraction distribution ratio measurements were used to design a flowsheet to accomplish this separation. Additionally, crossflow filtration was investigated as a method to filter the bismuthate solids from the feed solution prior to extraction. Results of the filtration studies, flowsheet development work and flowsheet performance testing using a centrifugal contactor are detailed.

  1. Speciation and bioavailability of Americium-241 in the fresh water environment

    International Nuclear Information System (INIS)

    Due to its anthropogenic origin, the transuranic americium 241 confronts physiologists with the intriguing question, which mechanisms are involved in the incorporation or elimination of such artificial elements in biological cycles. The investigations on the speciation and bioavailability of 241Am in the freshwater environment aim to establish a relation between the behavior of 241Am in freshwater ecosystems and its availability for biota. In the limnic environment, most often characterized by a high organic load and a low conductivity, the effect of complexation of 241Am with humic acids and competition with trivalent cations such as A1 and Fe, were proven to be significant on the speciation of 241Am. Based on the registration of the 241Am uptake by a large number of freshwater organisms, the crayfish Astacus leptodactylus Eschscholtz was chosen to study the whole-body uptake of 241Am, its corresponding organ distribution and its retention in the animal. The share of external fixation and ingestion in the global uptake, and the effect of speciation on it, were studied more carefully. Other aspects in this physiological part were: the kinetics of 241Am in the hemolymph and the hepatopancreas, and its subcellular distribution in the digestive gland. Finally, by comparing the physiology of 241Am with some other metals (240Pu, 64Cu, 198Au) with analogous or contradictional properties, we tried to find out whether the behavior of 241Am in organisms can be explained from its chemical characteristics

  2. Solution speciation of plutonium and Americium at an Australian legacy radioactive waste disposal site.

    Science.gov (United States)

    Ikeda-Ohno, Atsushi; Harrison, Jennifer J; Thiruvoth, Sangeeth; Wilsher, Kerry; Wong, Henri K Y; Johansen, Mathew P; Waite, T David; Payne, Timothy E

    2014-09-01

    During the 1960s, radioactive waste containing small amounts of plutonium (Pu) and americium (Am) was disposed in shallow trenches at the Little Forest Burial Ground (LFBG), located near the southern suburbs of Sydney, Australia. Because of periodic saturation and overflowing of the former disposal trenches, Pu and Am have been transferred from the buried wastes into the surrounding surface soils. The presence of readily detected amounts of Pu and Am in the trench waters provides a unique opportunity to study their aqueous speciation under environmentally relevant conditions. This study aims to comprehensively investigate the chemical speciation of Pu and Am in the trench water by combining fluoride coprecipitation, solvent extraction, particle size fractionation, and thermochemical modeling. The predominant oxidation states of dissolved Pu and Am species were found to be Pu(IV) and Am(III), and large proportions of both actinides (Pu, 97.7%; Am, 86.8%) were associated with mobile colloids in the submicron size range. On the basis of this information, possible management options are assessed. PMID:25126837

  3. Solution speciation of plutonium and Americium at an Australian legacy radioactive waste disposal site.

    Science.gov (United States)

    Ikeda-Ohno, Atsushi; Harrison, Jennifer J; Thiruvoth, Sangeeth; Wilsher, Kerry; Wong, Henri K Y; Johansen, Mathew P; Waite, T David; Payne, Timothy E

    2014-09-01

    During the 1960s, radioactive waste containing small amounts of plutonium (Pu) and americium (Am) was disposed in shallow trenches at the Little Forest Burial Ground (LFBG), located near the southern suburbs of Sydney, Australia. Because of periodic saturation and overflowing of the former disposal trenches, Pu and Am have been transferred from the buried wastes into the surrounding surface soils. The presence of readily detected amounts of Pu and Am in the trench waters provides a unique opportunity to study their aqueous speciation under environmentally relevant conditions. This study aims to comprehensively investigate the chemical speciation of Pu and Am in the trench water by combining fluoride coprecipitation, solvent extraction, particle size fractionation, and thermochemical modeling. The predominant oxidation states of dissolved Pu and Am species were found to be Pu(IV) and Am(III), and large proportions of both actinides (Pu, 97.7%; Am, 86.8%) were associated with mobile colloids in the submicron size range. On the basis of this information, possible management options are assessed.

  4. Orientation relationship between alpha-prime titanium and silicide S2 in alloy Ti-6Al-5Zr-0. 5Mo-0. 25Si

    Energy Technology Data Exchange (ETDEWEB)

    Ramachandra, C.; Singh, V.

    1985-03-01

    Orientation relationships between the silicide S2 and the matrix of alpha-prime platelets are established for the titanium alloy 685 (Ti-6Al-5Zr-0.5Mo-0.25Si), a near-alpha alloy designed for the high-temperature components of jet engines. A stereogram showing the parallel planes of alpha-prime and S2 is presented for the alloy in the water-quenched and aged condition. A table is also presented which lists the parallel planes of the matrix and the silicide along with the misfit parameters. The results obtained are compared with the orientation relationships reported in the literature. 14 references.

  5. A study of plutonium and americium concentrations in seaspray on the southern Scottish coast

    International Nuclear Information System (INIS)

    Seaspray and seawater have been collected from the southern Scottish coast and, for comparison, Cumbria in northwest England during 1989 and 1991. The occurrence of sea-to-land transfer of the actinides plutonium and americium in seaspray was observed on these coasts using muslin screens (a semi-quantitative technique most efficient for collecting large spray droplets) and high volume conventional air samplers. The actinides and fine particulate in the spray were present in relatively higher concentrations than measured in the adjacent seawater, i.e. the spray was enriched in particulate actinides. The net efficiency of the muslim screens in collecting airborne plutonium isotopes and 241Am generally appeared to be about 20%. A review of earlier published concentrations of 239+240Pu and 241Am measured in aerosol and deposition for over a year several tens of metres inland was carried out. This suggested that airborne activities are up to a factor of 5 times higher in Cumbria than southern Scotland. However, neither the new data collected in 1989 and 1991 nor this older data suggests any enhancement of seaspray actinide enrichment in southern Scotland compared to Cumbria. This finding contrasts with earlier, more limited, comparisons that have been carried out which suggested such a difference. There is clear evidence of considerable localised spatial and temporal variability in aerosol actinide enrichment over the beaches in both areas. Enrichments varies between 20 and 500 relative to the adjacent surf zone waters. However, the average enrichment in spray based on the continuous measurements made further inland is likely to be at the lower end of this range. (author)

  6. Biosorption of Americium-242 by saccharomyces cerevisiae: preliminary evaluation and mechanism

    International Nuclear Information System (INIS)

    As an important radioisotope in nuclear industry and other fields, americium-241 is one of the most serious contamination concerns duo to its high radiation toxicity and long half-life. In this experiment, the biosorption of 241Am from solution by a fungus, Saccharomyces cerevisiae (S. cerevisiae), and the effects of various experimental conditions on the biosorption and the mechanism were explored. The preliminary results showed that S. cerevisiae is a very efficient biosorbent. An average of more than 99% of the total 241Am could be removed by S. cerevisiae of 2.1g/L (dry weight) from 241Am solutions of 2.22MBq/L -555 MBq/L (Co). The adsorption equilibrium was achieved within 1 hour and the optimum pH ranged 1-3. The culture times of more than 16 hours were suitable and the efficient adsorption of 241Am by the S. cerevisiae could be noted. The biosorption of 241Am by the decomposed cell wall, protoplasm or cell membrane of S. cerevisiae was same efficient as by the intact fungus, but the some components of S. cerevisiae, such as protein and acylation group had obvious effect on adsorption. When the concentrations of coexistent Eu3+, Nd3+ were 100 times more than that of 241Am, the adsorption rates would drop to 65%. However, most of the investigated acidic ions have no significant influence on the 241Am adsorption but minute change of pH value, while the saturated EDTA can strong inhibit the biosorption of 241Am.. (authors)

  7. Transport of plutonium, americium, and curium from soils into plants by roots

    International Nuclear Information System (INIS)

    For assessing the dose from radionuclides in agricultural products by ingestion it is necessary to know the soil to plant transfer factors. The literature was entirely investigated, in order to judge the size of the soil to plant transfer factors. In total, 92 publications - from 1948 to 1978 -have been evaluated. As result, transfer factors from 10-9 to 10-3 have been found for Plutonium, and from 10-6 to 1 for Americium. For Curium only few data are available in literature. The considerable variation of the measured transfer factors is based on the dependence of these transfer factors from the ion exchange capacity of soils, from the amount of organic materials, from the pH-value, and from the mode of contamination. There are, in any case, contradictory data, although there has been detected a dependence of the transfer factors from these parameters. Chelating agenst increase the transfer factors to approximately 1300. As well, fertilizers have an influence on the size of the transfer factors - however, the relationships have been scarcely investigated. The distribution of actinides within the individual parts of plants has been investigated. The highest concentrations are in the roots; in the plant parts above ground the concentration of actinides decreases considerably. The most inferior transfer factors were measured for the respective seed or fruits. The soil to plant transfer factors of actinides are more dependend on the age of the plants within one growing period. At the beginning of the period, the transfer factor is considerably higher than at the end of this period. With respect to plants with a growing period of several years, correlations are unknown. (orig.)

  8. The treatment of liquid radioactive waste containing Americium by using a cation exchange method

    International Nuclear Information System (INIS)

    A research in the treatment of a liquid radioactive waste containing americium has been done. The liquid radioactive waste used in this research was standard solution of U dan Ce with the initial activity of 100 ppm. The experimental investigation is aimed at a study of the effects of the waste pH, the column dimension of IR-120 cation exchanger which is expressed as L/D, the flow rate of a liquid waste and the influence of thiocyanate as a complex agent against the efficiency of a decontamination for uranium and cerium element. The experiment was done by passing downward the feed of uranium and cerium solution into an IR-120 type of cation exchanger with the L/D of 11.37. From the experimental parameters done in this research where the influence of waste pH was varied from 3 - 8, the geometric column (L/D) 11.37, the liquid flow rate was from 2.5 - 10 ml/m and the thiocyanate concentration was between 100 ppm-500 ppm can be concluded that the optimum operational condition for the ion exchange achieved were the waste pH for uranium = 4 and the waste pH for cerium = 6, the flow rate = 2.5 ml/men. From the given maximum value of DF for uranium = 24 (DE = 95.83%) and of DF for cerium = 40 (DE = 97.5%), it can also be concluded that this investigation is to be continued in order that the greater value of DF/DE can be achieved

  9. M(5)-silicon (M= titanium, niobium, molybdenum) based transition-metal silicides for high temperature applications

    Science.gov (United States)

    Tang, Zhihong

    2007-12-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600ºC. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2 and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500ºC. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500ºC by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L ↔ Nbss + NbB was determined to occur at 2104+/-5°C by DTA.

  10. Fuel loading and homogeneity analysis of HFIR design fuel plates loaded with uranium silicide fuel

    International Nuclear Information System (INIS)

    Twelve nuclear reactor fuel plates were analyzed for fuel loading and fuel loading homogeneity by measuring the attenuation of a collimated X-ray beam as it passed through the plates. The plates were identical to those used by the High Flux Isotope Reactor (HFIR) but were loaded with uranium silicide rather than with HFIR's uranium oxide fuel. Systematic deviations from nominal fuel loading were observed as higher loading near the center of the plates and underloading near the radial edges. These deviations were within those allowed by HFIR specifications. The report begins with a brief background on the thermal-hydraulic uncertainty analysis for the Advanced Neutron Source (ANS) Reactor that motivated a statistical description of fuel loading and homogeneity. The body of the report addresses the homogeneity measurement techniques employed, the numerical correction required to account for a difference in fuel types, and the statistical analysis of the resulting data. This statistical analysis pertains to local variation in fuel loading, as well as to ''hot segment'' analysis of narrow axial regions along the plate and ''hot streak'' analysis, the cumulative effect of hot segment loading variation. The data for all twelve plates were compiled and divided into 20 regions for analysis, with each region represented by a mean and a standard deviation to report percent deviation from nominal fuel loading. The central regions of the plates showed mean values of about +3% deviation, while the edge regions showed mean values of about -7% deviation. The data within these regions roughly approximated random samplings from normal distributions, although the chi-square (χ2) test for goodness of fit to normal distributions was not satisfied

  11. Rate Theory Modeling and Simulation of Silicide Fuel at LWR Conditions

    Energy Technology Data Exchange (ETDEWEB)

    Miao, Yinbin [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Ye, Bei [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Hofman, Gerard [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Yacout, Abdellatif [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division; Gamble, Kyle [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation; Mei, Zhi-Gang [Argonne National Lab. (ANL), Argonne, IL (United States). Nuclear Engineering Division

    2016-08-29

    As a promising candidate for the accident tolerant fuel (ATF) used in light water reactors (LWRs), the fuel performance of uranium silicide (U3Si2) at LWR conditions need to be well-understood. In this report, rate theory model was developed based on existing experimental data and density functional theory (DFT) calculations so as to predict the fission gas behavior in U3Si2 at LWR conditions. The fission gas behavior of U3Si2 can be divided into three temperature regimes. During steady-state operation, the majority of the fission gas stays in intragranular bubbles, whereas the dominance of intergranular bubbles and fission gas release only occurs beyond 1000 K. The steady-state rate theory model was also used as reference to establish a gaseous swelling correlation of U3Si2 for the BISON code. Meanwhile, the overpressurized bubble model was also developed so that the fission gas behavior at LOCA can be simulated. LOCA simulation showed that intragranular bubbles are still dominant after a 70 second LOCA, resulting in a controllable gaseous swelling. The fission gas behavior of U3Si2 at LWR conditions is benign according to the rate theory prediction at both steady-state and LOCA conditions, which provides important references to the qualification of U3Si2 as a LWR fuel material with excellent fuel performance and enhanced accident tolerance.

  12. Use of radioisotopes in the study of tetracycline analytical application. Extraction of compounds formed between tetracycline and neptunium and americium elements

    International Nuclear Information System (INIS)

    The behavior of tetracycline as complexing agent, in solvent extraction studies of neptunium and americium, using benzyl alcohol as the organic phase, is presented. By using radioactive tracers of 239Np and 241Am the extraction percent of these elements were determined as a function of pH in the absence and in the presence of several masking agents. The influence of shaking time and the use of different types of supporting eletrolytes upon the extraction behavior was also studied. The extraction curves obtained using EDTA as masking agent show that tetracycline can be used for neptunium and americium separation. In this condition neptunium is extracted into the organic phase and americium remains in the aqueous phase. (Author)

  13. Effect of a long-term release of plutonium and americium into an estuarine and coastal sea ecosystem

    International Nuclear Information System (INIS)

    This paper discusses the general problem of speciation of plutonium and americium in aquatic ecosystems and the implications relative to their fate in those systems. The following conclusions were reached: several oxidation states of plutonium coexist in the natural environment; the effect of environmental changes such as pH and Esub(h) values and complexes are probably the cause of these various oxidation states; a clearer definition of the 'concentration factor' should be given in view of the important role the sediments play in supplying plutonium for transfer through the food web. (author)

  14. EFFECT OF COMPOSITION OF SELECTED GROUNDWATERS FROM THE BASIN AND RANGE PROVINCE ON PLUTONIUM, NEPTUNIUM, AND AMERICIUM SPECIATION.

    Science.gov (United States)

    Rees, Terry F.; Cleveland, Jess M.; Nash, Kenneth L.

    1984-01-01

    The speciation of plutonium, neptunium, and americium was determined in groundwaters from four sources in the Basin and Range Province: the lower carbonate aquifer, Nevada Test Site (NTS) (Crystal Pool); alluvial fill, Frenchman Flat, NTS (well 5C); Hualapai Valley, Arizona (Red Lake south well); and Tularosa Basin, New Mexico (Rentfrow well). The results were interpreted to indicate that plutonium and, to a lesser extent, neptunium are least soluble in reducing groundwaters containing a large concentration of sulfate ion and a small concentration of strongly complexing anions. The results further emphasize the desirability of including studies such as this among the other site-selection criteria for nuclear waste repositories.

  15. Microstructure and elemental distribution of americium-containing MOX fuel under the short-term irradiation tests

    International Nuclear Information System (INIS)

    In order to investigate the effect of americium addition to MOX fuels on the irradiation behavior, the 'Am-1' program is being conducted in JAEA. The Am-1 program consists of two short-term irradiation tests of 10-minute and 24-hour irradiations and a steady-state irradiation test. The short-term irradiation tests were successfully completed and the post irradiation examinations (PIEs) are in progress. The PIEs for Am-containing MOX fuels focused on the microstructural evolution and redistribution behavior of Am at the initial stage of irradiation and the results to date are reported. (author)

  16. Development of a methodology for the determination of americium and thorium by ICP-AES and their inter-element effect

    International Nuclear Information System (INIS)

    Due to the scarcity of good quality uranium resources, the growth of nuclear technology in India is dependent on the utilization of the vast thorium resources. Therefore, Advance Heavy Water Reactor is going to acquire significant role in the scenario of Indian nuclear technology, where (Th, Pu)O2 will be utilized as fuel in the outermost ring of the reactor core. This will lead to a complex matrix containing thorium as well as americium, which is formed due to β-decay of plutonium. The amount of americium is dependent on the burn up and the storage time of the Pu based fuels. In the present case, attempt was made to develop a method for the determination of americium as well as thorium by ICP-AES. Two emission lines of americium were identified and calibration curves were established for determination of americium. Though the detection limit of 283.236 nm line (5 ng mL-1) of americium was found to be better than that of 408.930 nm (11 ng mL-1), the former line is significantly interfered by large amount of thorium. Three analytical lines (i.e. 283.242, 283.730 and 401.913 nm) of thorium were identified and calibration curves were established along with their detection limits. It was observed that 283.242 and 401.913 nm line are having similar detection limits (18 and 13 ng mL-1, respectively) which are better than that of 283.730 nm (60 ng mL-1). This can be attributed to the high background of 283.273 nm channel of thorium. The spectral interference study revealed that even small amount of americium has significant contribution on 283.242 nm channel of thorium while the other two channels remain practically unaffected. Considering both these facts, spectral interference and analytical performance (detection limits and sensitivity), it was concluded that 401.913 nm line is the best analytical line out of the three lines for determination of thorium in presence of americium. (author)

  17. Hot wire chemical vapor deposition: limits and opportunities of protecting the tungsten catalyzer from silicide with a cavity

    Energy Technology Data Exchange (ETDEWEB)

    Frigeri, P.A. [Dept. de Fisica Aplicada i Optica, Universitat de Barcelona, Barcelona-08028 (Spain); Nos, O., E-mail: oriol_nos@ub.ed [Dept. de Fisica Aplicada i Optica, Universitat de Barcelona, Barcelona-08028 (Spain); Ecotecnia (ALSTOM Group) (Spain); Bengoechea, S.; Frevert, C.; Asensi, J.M.; Bertomeu, J. [Dept. de Fisica Aplicada i Optica, Universitat de Barcelona, Barcelona-08028 (Spain)

    2009-04-30

    Hot Wire Chemical Vapor Deposition (HW-CVD) is one of the most promising techniques for depositing the intrinsic microcrystalline silicon layer for the production of micro-morph solar cells. However, the silicide formation at the colder ends of the tungsten wire drastically reduces the lifetime of the catalyzer, thus limiting its industrial exploitation. A simple but interesting strategy to decrease the silicide formation is to hide the electrical contacts of the catalyzer in a long narrow cavity which reduces the probability of the silane molecules to reach the colder ends of the wire. In this paper, the working mechanism of the cavity is elucidated. Measurements of the thickness profile of the silicon deposited in the internal walls of the cavity have been compared with those predicted using a simple diffusion model based on the assumption of Knudsen flow. A lifetime study of the protected and unprotected wires has been carried out. The different mechanisms which determine the deterioration of the catalyzer have been identified and discussed.

  18. Effects of nitrogen annealing on surface structure, silicide formation and magnetic properties of ultrathin films of Co on Si(100)

    Indian Academy of Sciences (India)

    Ganesh K Rajan; Shivaraman Ramaswamy; C Gopalakrishnan; D John Thiruvadigal

    2012-02-01

    Effects of nitrogen annealing on structural and magnetic properties of Co/Si (100) up to 700°C has been studied in this paper. Ultrathin Co films having a constant thickness of 50 Å were grown on Si (100) substrates using electron-beam evaporation under very high vacuum conditions at room temperature. Subsequently, the samples were annealed at temperatures ranging from 100–700°C in a nitrogen environment at atmospheric pressure. Sample quality and surface morphology were examined using atomic force microscopy. Silicide formation and the resultant variation in crystallographic arrangement were studied using X-ray diffractometer. The magnetization measurements done using a vibrating sample magnetometer indicate a decrease in coercivity and retentivity values with increase in annealing temperature. Resistivity of the samples measured using a four-point probe set up shows a decrease in resistivity with increase in annealing temperature. Formation of various silicide phases at different annealing temperatures and the resultant variation in the magnetic susceptibility has been thoroughly studied and quantified in this work.

  19. Thermal Stability and Growth Behavior of Erbium Silicide Nanowires Self-Assembled on a Vicinal Si(001) Surface

    Institute of Scientific and Technical Information of China (English)

    DING Tao; SONG Jun-Qiang; LI Juan; CAI Qun

    2011-01-01

    Erbium silicide nanowires are self-assembled on vicinal Si(Ool) substrates after electron beam evaporation and post annealing at 63(fC In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged. Meanwhile, a structural transition from hexagonal AIB2 phase to tetragonal ThSi'2 phase is revealed with high-resolution transmission electron microscopy. It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires. Additionally, a multiple deposition-annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.%@@ Erbium silicide nanowires are self-assembled on vicinal Si(001) substrates after electron beam evaporation and post annealing at 630℃ In-situ scanning tunneling microscopy investigations manifest that the nanowires will successively shrink and transform into a nanoisland with annealing prolonged.Meanwhile, a structural transition from hexagonal AlB phase to tetragonal ThSi phase is revealed with high-resolution transmission electron microscopy.It is also found that the nanowires gradually expand to embed into the substrates during the growth process, which has much influence on the shape instability of nanowires.Additionally, a multiple deposition- annealing treatment is given as a novel growth method to strengthen the controlled fabrication of nanowires.

  20. Influence of layout parameters on snapback characteristic for a gate-grounded NMOS device in 0.13-μm silicide CMOS technology

    Institute of Scientific and Technical Information of China (English)

    Jiang Yuxi; Li Jiao; Ran Feng; Cao Jialin; Yang Dianxiong

    2009-01-01

    r of the GGNMOS devices under high ESD current stress, and design area-efficient ESD protection circuits to sustain the required ESD level.Optimized layout rules for ESD protection in 0.13-μm silicide CMOS technology are also presented.

  1. Effect of radiolysis on leachability of plutonium and americium from 76-101 glass. [Glass containing 2 mole % plutonium

    Energy Technology Data Exchange (ETDEWEB)

    Nash, K.L.; Fried, S.; Friedman, A.M.; Susak, N.; Rickert, P.; Sullivan, J.C.; Karim, D.P.; Lam, D.J.

    1982-01-01

    One aspect of the leachability of actinide-bearing glass which has not been adequately addressed is the effect of radiolysis of the system (glass-water) on the amount of actinides liberated from the glass. In the present study, we have investigated the leaching of plutonium and americium from 76-101 glass samples (containing 2 mole % plutonium) in the presence of a one megaRad/hour gamma-radiation field. The presence of the radiation field was found to increase the leaching rate of both plutonium and americium by a factor of five. Speciation studies of the plutonium in the leachate indicate that the plutonium is present predominantly in the higher oxidation states, Pu(V) and Pu(VI) and that it is significantly associated with colloidal particles. Examination of the glass surfaces with x-ray photoemission spectroscopy, XPS, both before and after leaching was carried out; these studies showed lower surface concentrations of plutonium in the samples of glass leached in the radiation field. 1 figure, 3 tables.

  2. Osteosarcoma induction by plutonium-239, americium-241 and neptunium-237 : the problem of deriving risk estimates for man

    International Nuclear Information System (INIS)

    Spontaneous bone cancer (osteosarcoma) represents only about 0.3% of all human cancers, but is well known to be inducible in humans by internal contamination with radium-226 and radium-224. plutonium-239, americium-241 and neptunium-237 form, or will form, the principal long-lived alpha particle emitting components of high activity waste and burnt-up nuclear fuel elements. These three nuclides deposit extensively in human bone and although, fortunately, no case of a human osteosarcoma induced by any of these nuclides is known, evidence from animal studies suggests that all three are more effective than radium-226 in inducing osteosarcoma. The assumption that the ratio of the risk factors, the number of osteosarcoma expected per 10000 person/animal Gy, for radium-226 and any other bone-seeking alpha-emitter will be independent of animal species has formed the basis of all the important studies of the radiotoxicity of actinide nuclides in experimental animals. The aim of this communication is to review the risk factors which may be calculated from the various animal studies carried out over the last thirty years with plutonium-237, americium-241 and neptunium-237 and to consider the problems which may arise in extrapolating these risk factors to homo sapiens

  3. Experimental Study on Behavior of Americium in Pyrochemical Process of Nitride Fuel Cycle

    International Nuclear Information System (INIS)

    R and D on the transmutation of long-lived minor actinides (MA) by the accelerator-driven system (ADS) using nitride fuels is underway at JAEA. In regard to reprocessing technology, pyrochemical process has several advantages in case of treating spent fuel with large decay heat and fast neutron emission, and recovering highly enriched N-15. In the pyrochemical reprocessing, plutonium and MA are dissolved in LiCl-KCl eutectic melts and selectively recovered into liquid cadmium (Cd) cathode by molten salt electrorefining. The electrochemical behavior in LiCl-KCl eutectic melts and the subsequent nitride formation behavior of plutonium and MA recovered in liquid Cd cathode are investigated. In this paper, recent results on electrochemical study of americium (Am) on electrolyses of AmN in LiCl-KCl eutectic melts and nitride formation of Am recovered in the liquid Cd cathode are presented. Electrochemical behavior of Am on anodic dissolution of AmN and recovery of Am into a liquid Cd cathode by electrolyses in LiCl-KCl eutectic melts was investigated by transient electrochemical techniques. The formal standard potential of Am(III)/Am(0) obtained with the liquid Cd electrode is more positive than that calculated for the solid metal electrode. The potential shift is considered to be attributed to the lowering of the activity of Am by the formation of the intermetallic compound with Cd. Potentiostatic electrolyses of AmN in LiCl-KCl eutectic melts containing AmCl3 at 773 K were carried out. Nitrogen gas generated by the anodic dissolution of AmN was observed, and the current efficiency was obtained from the ratio of the amount of released nitrogen gas and the passed electric charge to be 20 - 28 %. Am was recovered as Am-Cd alloy in the liquid Cd cathode, in which AmCd6 type phase was identified besides Cd phase. The recovered Am was converted to AmN by the nitridation-distillation combined method, in which the Am-Cd alloy was heated in nitrogen gas stream at 973 K. These

  4. Synthesis and characterization of β-phase iron silicide nano-particles by chemical reduction

    Energy Technology Data Exchange (ETDEWEB)

    Sen, Sabyasachi [Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Gogurla, Narendar [Department of Physics, Indian Institute of Technology, Kharagpur 721302 (India); Banerji, Pallab [Materials Science Centre, Indian Institute of Technology, Kharagpur 721302 (India); Guha, Prasanta K. [Department of Electronics & Electrical Communication Engineering, Indian Institute of Technology, Kharagpur 721302 (India); Pramanik, Panchanan, E-mail: pramanik1946@gmail.com [Department of Basic Science, MCKV Institute of Engineering, Howrah, Liluah 711204 (India)

    2015-10-15

    Graphical abstract: - Highlights: • β-FeSi{sub 2} nano-particle was synthesized by reducing with Mg and by diluting with MgO. • XRD profile shows the iron di-silicide phase to be semiconducting β-FeSi{sub 2}. • HRTEM and FESEM images indicate the β-FeSi{sub 2}average particle size to be 60–70 nm. • Absorption, reflectance and PL spectroscopy show band gap to be direct 0.87 eV. • Nano-β-FeSi{sub 2}is p-type with hole density of 4.38 × 10{sup 18} cm{sup −3} and mobility 8.9 cm{sup 2}/V s. - Abstract: Nano-particles of β-FeSi{sub 2} have been synthesized by chemical reduction of a glassy phase of [Fe{sub 2}O{sub 3}, 4SiO{sub 2}] by Mg-metal where MgO is used as diluent to prevent the agglomeration of nano crystallites into micro-particles and also act as a negative catalyst for the formation of other phases. The sample is characterized by XRD, FESEM, HRTEM, EDX, ultra-violet-visible-infrared and PL spectroscopy and electronic properties have been investigated by Hall measurement. XRD profile shows that the synthesized powder consists of purely β-FeSi{sub 2} semiconducting phase. The average crystallite size of β-FeSi{sub 2} is determined to be around 65.4 nm from XRD peaks as well as from FESEM also. The optical absorption and PL spectroscopy shows that synthesized β-FeSi{sub 2} phase is a direct band gap semiconductor with a value of 0.87 eV. Hall measurements show that β-FeSi{sub 2} nano-particles is p-type with hole concentration of 4.38 × 10{sup 18} cm{sup −3} and average hole mobility of 8.9 cm{sup 2}/V s at 300 K.

  5. Narrow bandgap semiconducting silicides: Intrinsic infrared detectors on a silicon chip

    Science.gov (United States)

    Mahan, John E.

    1990-01-01

    Work done during the final report period is presented. The main technical objective was to achieve epitaxial growth on silicon of two semiconducting silicides, ReSi2 and CrSi2. ReSi2 thin films were grown on (001) silicon wafers by vacuum evaporation of rhenium onto hot substrates in ultrahigh vacuum. The preferred epitaxial relationship was found to be ReSi2(100)/Si(001) with ReSi2(010) parallel to Si(110). The lattice matching consists of a common unit mesh of 120 A(sup 2) area, and a mismatch of 1.8 percent. Transmission electron microscopy revealed the existence of rotation twins corresponding to two distinct but equivalent azimuthal orientations of the common unit mesh. MeV He(+) backscattering spectrometry revealed a minimum channeling yield of 2 percent for an approximately 1,500 A thick film grown at 650 C. Although the lateral dimension of the twins is on the order of 100 A, there is a very high degree of alignment between the ReSi2(100) and the Si(001) planes. Highly oriented films of CrSi2 were grown on (111) silicon substrates, with the matching crystallographic faces being CrSi2(001)/Si(111). The reflection high-energy electron diffraction (RHEED) patterns of the films consist of sharp streaks, symmetrically arranged. The predominant azimuthal orientation of the films was determined to be CrSi2(210) parallel to Si(110). This highly desirable heteroepitaxial relationship has been obtained previously by others; it may be described with a common unit mesh of 51 A(sup 2) and mismatch of 0.3 percent. RHEED also revealed the presence of limited film regions of a competing azimuthal orientation, CrSi2(110) parallel to Si(110). A channeling effect for MeV He(+) ions was not found for this material. Potential commercial applications of this research may be found in silicon-integrated infrared detector arrays. Optical characterizations showed that semiconducting ReSi2 is a strong absorber of infrared radiation, with the adsorption constant increasing above 2 x

  6. LIBS Spectral Data for a Mixed Actinide Fuel Pellet Containing Uranium, Plutonium, Neptunium and Americium

    Energy Technology Data Exchange (ETDEWEB)

    Judge, Elizabeth J. [Los Alamos National Laboratory; Berg, John M. [Los Alamos National Laboratory; Le, Loan A. [Los Alamos National Laboratory; Lopez, Leon N. [Los Alamos National Laboratory; Barefield, James E. [Los Alamos National Laboratory

    2012-06-18

    Laser-induced breakdown spectroscopy (LIBS) was used to analyze a mixed actinide fuel pellet containing 75% UO{sub 2}/20% PuO{sub 2}/3% AmO{sub 2}/2% NpO{sub 2}. The preliminary data shown here is the first report of LIBS analysis of a mixed actinide fuel pellet, to the authors knowledge. The LIBS spectral data was acquired in a plutonium facility at Los Alamos National Laboratory where the sample was contained within a glove box. The initial installation of the glove box was not intended for complete ultraviolet (UV), visible (VIS) and near infrared (NIR) transmission, therefore the LIBS spectrum is truncated in the UV and NIR regions due to the optical transmission of the window port and filters that were installed. The optical collection of the emission from the LIBS plasma will be optimized in the future. However, the preliminary LIBS data acquired is worth reporting due to the uniqueness of the sample and spectral data. The analysis of several actinides in the presence of each other is an important feature of this analysis since traditional methods must chemically separate uranium, plutonium, neptunium, and americium prior to analysis. Due to the historic nature of the sample fuel pellet analyzed, the provided sample composition of 75% UO{sub 2}/20% PuO{sub 2}/3% AmO{sub 2}/2% NpO{sub 2} cannot be confirm without further analytical processing. Uranium, plutonium, and americium emission lines were abundant and easily assigned while neptunium was more difficult to identify. There may be several reasons for this observation, other than knowing the exact sample composition of the fuel pellet. First, the atomic emission wavelength resources for neptunium are limited and such techniques as hollow cathode discharge lamp have different dynamics than the plasma used in LIBS which results in different emission spectra. Secondly, due to the complex sample of four actinide elements, which all have very dense electronic energy levels, there may be reactions and

  7. Preconcentration of low levels of americium and plutonium from waste waters by synthetic water-soluble metal-binding polymers with ultrafiltration

    International Nuclear Information System (INIS)

    A preconcentration approach to assist in the measurement of low levels of americium and plutonium in waste waters has been developed based on the concept of using water-soluble metal-binding polymers in combination with ultrafiltration. The method has been optimized to give over 90% recovery and accountability from actual waste water. (author)

  8. Theoretical investigation of pressure-induced structural transitions in americium using GGA+U and hybrid density functional theory methods

    DEFF Research Database (Denmark)

    Verma, Ashok K.; Modak, P.; Sharma, Surinder M.;

    2013-01-01

    First-principles calculations have been performed for americium (Am) metal using the generalized gradient approximation + orbital-dependent onsite Coulomb repulsion via Hubbard interaction (GGA+U) and hybrid density functional theory (HYB-DFT) methods to investigate various ground state propertie...

  9. Physical, Mechanical, and Structural Properties of Highly Efficient Nanostructured n- and p-Silicides for Practical Thermoelectric Applications

    Science.gov (United States)

    Gelbstein, Yaniv; Tunbridge, Jonathan; Dixon, Richard; Reece, Mike J.; Ning, Huanpo; Gilchrist, Robert; Summers, Richard; Agote, Iñigo; Lagos, Miguel A.; Simpson, Kevin; Rouaud, Cedric; Feulner, Peter; Rivera, Sergio; Torrecillas, Ramon; Husband, Mark; Crossley, Julian; Robinson, Ivan

    2014-06-01

    Cost-effective highly efficient nanostructured n-type Mg2Si1- x Sn x and p-type higher manganese silicide (HMS) compositions were prepared for the development of practical waste heat generators for automotive and marine thermoelectric applications, in the frame of the European Commission (EC)-funded PowerDriver project. The physical, mechanical, and structural properties were fully characterized as part of a database-generation exercise required for the thermoelectric converter design. A combination of high maximal ZT values of ˜0.6 and ˜1.1 for the HMS and Mg2Si1- x Sn x compositions, respectively, and adequate mechanical properties was obtained.

  10. Theoretical investigation of superconductivity in ternary silicide NaAlSi with layered diamond-like structure

    Science.gov (United States)

    Tütüncü, H. M.; Karaca, Ertuǧrul; Srivastava, G. P.

    2016-04-01

    We have investigated the electronic structure, phonon modes and electron-phonon coupling to understand superconductivity in the ternary silicide NaAlSi with a layered diamond-like structure. Our electronic results, using the density functional theory within a generalized gradient approximation, indicate that the density of states at the Fermi level is mainly governed by Si p states. The largest contributions to the electron-phonon coupling parameter involve Si-related vibrations both in the x-y plane as well as along the z-axis in the x-z plane. Our results indicate that this material is an s-p electron superconductor with a medium level electron-phonon coupling parameter of 0.68. Using the Allen-Dynes modification of the McMillan formula we obtain the superconducting critical temperature of 6.98 K, in excellent agreement with experimentally determined value of 7 K.

  11. I-V-T studies on Ni-silicide/n-Si(100) contacts formed by Ti-Ni-Si solid state reaction

    Institute of Scientific and Technical Information of China (English)

    Zhu Shi-Yang; Ru Guo-Ping; Zhou Jia; Huang Yi-Ping

    2005-01-01

    The current-voltage (I-V) characteristics of Ni silicide/n-Si(100) contacts, which were formed from solid-state reaction of Ni-Si with a thin Ti capping layer at different annealing temperatures, were measured at temperatures ranging from 80K to room temperature. The low temperature I-V curves exhibit an excess current at the low bias region which is significantly larger than that predicted by the traditional thermionic emission (TE) model. A doubleSchottky barrier height (SBH) model simplified from Tung's pinch-off model is used to analyse the measured I-V curves,from which the extent of the SBH inhomogeneity can be extracted. Higher annealing temperature results in larger SBH inhomogeneity, implying the degradation of the silicide film uniformity. The thin Ti capping layer increases slightly both the NiSi phase transfer temperature and the thermal stability of the formed NiSi film.

  12. Vertically grown multiwalled carbon nanotube anode and nickel silicide integrated high performance microsized (1.25 μl) microbial fuel cell

    KAUST Repository

    Mink, Justine E.

    2012-02-08

    Microbial fuel cells (MFCs) are an environmentally friendly method for water purification and self-sustained electricity generation using microorganisms. Microsized MFCs can also be a useful power source for lab-on-a-chip and similar integrated devices. We fabricated a 1.25 μL microsized MFC containing an anode of vertically aligned, forest type multiwalled carbon nanotubes (MWCNTs) with a nickel silicide (NiSi) contact area that produced 197 mA/m 2 of current density and 392 mW/m 3 of power density. The MWCNTs increased the anode surface-to-volume ratio, which improved the ability of the microorganisms to couple and transfer electrons to the anode. The use of nickel silicide also helped to boost the output current by providing a low resistance contact area to more efficiently shuttle electrons from the anode out of the device. © 2012 American Chemical Society.

  13. Behavior of silicon in nitric media. Application to uranium silicides fuels reprocessing; Comportement du silicium en milieu nitrique. Application au retraitement des combustibles siliciures d'uranium

    Energy Technology Data Exchange (ETDEWEB)

    Cheroux, L

    2001-07-01

    Uranium silicides are used in some research reactors. Reprocessing them is a solution for their cycle end. A list of reprocessing scenarios has been set the most realistic being a nitric dissolution close to the classic spent fuel reprocessing. This uranium silicide fuel contains a lot of silicon and few things are known about polymerization of silicic acid in concentrated nitric acid. The study of this polymerization allows to point out the main parameters: acidity, temperature, silicon concentration. The presence of aluminum seems to speed up heavily the polymerization. It has been impossible to find an analytical technique smart and fast enough to characterize the first steps of silicic acid polymerization. However the action of silicic species on emulsions stabilization formed by mixing them with an organic phase containing TBP has been studied, Silicon slows down the phase separation by means of oligomeric species forming complex with TBP. The existence of these intermediate species is short and heating can avoid any stabilization. When non irradiated uranium silicide fuel is attacked by a nitric solution, aluminum and uranium are quickly dissolved whereas silicon mainly stands in solid state. That builds a gangue of hydrated silica around the uranium silicide particulates without preventing uranium dissolution. A small part of silicon passes into the solution and polymerize towards the highly poly-condensed forms, just 2% of initial silicon is still in molecular form at the end of the dissolution. A thermal treatment of the fuel element, by forming inter-metallic phases U-Al-Si, allows the whole silicon to pass into the solution and next to precipitate. The behavior of silicon in spent fuels should be between these two situations. (author)

  14. Morphological and electrical properties of self-assembled iron silicide nanoparticles on Si(0 0 1) and Si(1 1 1) substrates

    Science.gov (United States)

    Molnár, G.; Dózsa, L.; Erdélyi, R.; Vértesy, Z.; Osváth, Z.

    2015-12-01

    Epitaxial iron silicide nanostructures are grown by solid phase epitaxy on Si(0 0 1) and Si(1 1 1), and by reactive deposition epitaxy on Si(0 0 1) substrates. The formation process is monitored by reflection high-energy electron diffraction. The morphology, size, and electrical properties of the nanoparticles are investigated by scanning electron microscopy, by electrically active scanning probe microscopy, and by confocal Raman spectroscopy. The results show that the shape, size, orientation, and density of the nanoobjects can be tuned by self-assembly, controlled by the lattice misfit between the substrates and iron silicides. The size distribution and shape of the grown nanoparticles depend on the substrate orientation, on the initial thickness of the evaporated iron, on the temperature and time of the annealing, and on the preparation method. The so-called Ostwald ripening phenomena, which state that the bigger objects develop at the expense of smaller ones, controls the density of the nanoparticles. Raman spectra show the bigger objects do not contain β-FeSi2 phase. The different shape nanoparticles exhibit small, about 100 mV barrier compared to the surrounding silicon. The local leakage current of the samples measured by conductive AFM using a Pt coated Si tip is localized in a few nanometers size sites, and the sites which we assume are very small silicide nanoparticles or point defects.

  15. Interaction transfer of silicon atoms forming Co silicide for Co/√(3)×√(3)R30°-Ag/Si(111) and related magnetic properties

    Energy Technology Data Exchange (ETDEWEB)

    Chang, Cheng-Hsun-Tony; Fu, Tsu-Yi; Tsay, Jyh-Shen, E-mail: jstsay@phy.ntnu.edu.tw [Department of Physics, National Taiwan Normal University, Taipei 116, Taiwan (China)

    2015-05-07

    Combined scanning tunneling microscopy, Auger electron spectroscopy, and surface magneto-optic Kerr effect studies were employed to study the microscopic structures and magnetic properties for ultrathin Co/√(3)×√(3)R30°-Ag/Si(111). As the annealing temperature increases, the upward diffusion of Si atoms and formation of Co silicides occurs at temperature above 400 K. Below 600 K, the √(3)×√(3)R30°-Ag/Si(111) surface structure persists. We propose an interaction transferring mechanism of Si atoms across the √(3)×√(3)R30°-Ag layer. The upward transferred Si atoms react with Co atoms to form Co silicide. The step height across the edge of the island, a separation of 0.75 nm from the analysis of the 2 × 2 structure, and the calculations of the normalized Auger signal serve as strong evidences for the formation of CoSi{sub 2} at the interface. The interaction transferring mechanism for Si atoms enhances the possibility of interactions between Co and Si atoms. The smoothness of the surface is advantage for that the easy axis of magnetization for Co/√(3)×√(3)R30°-Ag/Si(111) is in the surface plane. This provides a possible way of growing flat magnetic layers on silicon substrate with controllable silicide formation and shows potential applications in spintronics devices.

  16. Simultaneous aluminizing and chromizing of steels to form (Fe,Cr){sub 3}Al coatings and Ge-doped silicide coatings of Cr-Zr base alloys

    Energy Technology Data Exchange (ETDEWEB)

    Zheng, M.; He, Y.R.; Rapp, R.A. [Ohio State Univ., Columbus, OH (United States). Dept. of Materials Science and Engineering

    1997-12-01

    A halide-activated cementation pack involving elemental Al and Cr powders has been used to achieve surface compositions of approximately Fe{sub 3}Al plus several percent Cr for low alloy steels (T11, T2 and T22) and medium carbon steel (1045 steel). A two-step treatment at 925 C and 1150 C yields the codeposition and diffusion of aluminum and chromium to form dense and uniform ferrite coatings of about 400 {micro}m thickness, while preventing the formation of a blocking chromium carbide at the substrate surfaces. Upon cyclic oxidation in air at 700 C, the coated steel exhibits a negligible 0.085 mg/cm{sup 2} weight gain for 1900 one-hour cycles. Virtually no attack was observed on coated steels tested at ABB in simulated boiler atmospheres at 500 C for 500 hours. But coatings with a surface composition of only 8 wt% Al and 6 wt% Cr suffered some sulfidation attack in simulated boiler atmospheres at temperatures higher than 500 C for 1000 hours. Two developmental Cr-Zr based Laves phase alloys (CN129-2 and CN117(Z)) were silicide/germanide coated. The cross-sections of the Ge-doped silicide coatings closely mimicked the microstructure of the substrate alloys. Cyclic oxidation in air at 1100 C showed that the Ge-doped silicide coating greatly improved the oxidation resistance of the Cr-Zr based alloys.

  17. Stability of penta- and hexavalent americium in the solutions of sodium peroxydisulfate and sodium bromate at intensive internal α-irradiation

    International Nuclear Information System (INIS)

    The spectrometric method has been used for studying the dependence of the rates of radiolytic reduction of Am(5) and (6) on the initial concentration of sodium persulfate and bromate, Am(5) and (6), acidity, and the dose rate of inner alpha-irradiation of the solutions. The high dose rates of inner alpha-irradiation of solutions (up to 3.25x1021 eV/lxmin-250Ci/l) have been attained with the aid of curium isotopes. The stability of americium (6) ions towards the action of ionizing radiation in solutions of sodium persulfate and bromate has been shown to be considerable lower than that of americium (5). The chemical difference has been shown in radiolytic behaviour between Am(5) and Am(6) ions in solutions of sodium persulfate and bromate. The equations have been derived showing the dependence of the rates of Am(6) and Am(5) reduction of different variables

  18. Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium-americium mixed oxides

    Science.gov (United States)

    Prieur, D.; Lebreton, F.; Martin, P. M.; Caisso, M.; Butzbach, R.; Somers, J.; Delahaye, T.

    2015-10-01

    Uranium-americium mixed oxides are potential compounds to reduce americium inventory in nuclear waste via a partitioning and transmutation strategy. A thorough assessment of the oxygen-to-metal ratio is paramount in such materials as it determines the important underlying electronic structure and phase relations, affecting both thermal conductivity of the material and its interaction with the cladding and coolant. In 2011, various XAS experiments on U1-xAmxO2±δ samples prepared by different synthesis methods have reported contradictory results on the charge distribution of U and Am. This work alleviates this discrepancy. The XAS results confirm that, independently of the synthesis process, the reductive sintering of U1-xAmxO2±δ leads to the formation of similar fluorite solid solution indicating the presence of Am+III and U+V in equimolar proportions.

  19. THE FIRST ISOLATION OF AMERICIUM IN THE FORM OF PURE COMPOUNDS - THE SPECIFIC ALPHA-ACTIVITY AND HALF-LIFE OF Am241

    Energy Technology Data Exchange (ETDEWEB)

    Cunningham, B.B.; Asprey, L.B.

    1950-07-20

    The microgram scale isolation and preparation of pure compounds of americium is described. Data are presented to show that the alpha-half-life of the isotope Am{sup 241} is 490 {+-} 14 years. The absorption spectrum of Am(III) in 1M nitric acid in the range 3500-8000 mu is given. The wave lengths of 10 of the most prominent lines in the copper spark emission spectrum of americium are given to the nearest 0.01 {angstrom}. Evidence is presented to show that the potential for the Am(III)-Am(IV) couple in acid solution is more negative than -2v and that the potential for the Am(II)-Am(III) couple is more positive than +0.9v.

  20. A Density Functional Study of Atomic Hydrogen and Oxygen Chemisorption on the Relaxed (0001) Surface of Double Hexagonal Close Packed Americium

    OpenAIRE

    Dholabhai, P. P.; Atta-Fynn, R.; A.K. Ray

    2009-01-01

    Ab initio total energy calculations within the framework of density functional theory have been performed for atomic hydrogen and oxygen chemisorption on the (0001) surface of double hexagonal packed americium using a full-potential all-electron linearized augmented plane wave plus local orbitals method. Chemisorption energies were optimized with respect to the distance of the adatom from the relaxed surface for three adsorption sites, namely top, bridge, and hollow hcp sites, the adlayer str...

  1. Experimental study of Americium-241 biokinetics in Homarus Gammarus lobster. Analysis of the accumulation and detoxication mechanisms at the sub-cellular level

    International Nuclear Information System (INIS)

    The Americium 241 radioelement accumulation and elimination rate and mechanisms in the lobster organism have been experimentally studied; incorporation and detoxification capacities of each organ are evaluated. The existence of various biological compartments is shown; the major role of the digestive gland in accumulation of the radioelement, its distribution towards the various organs, and its resorption is comprehensively described, with an analysis at the subcellular and molecular levels. 401 p., 65 fig., 43 tab., 428 ref

  2. A new method for the determination of plutonium and americium using high pressure microwave digestion and alpha-spectrometry or ICP-SMS

    International Nuclear Information System (INIS)

    Plutonium and americium are radionuclides particularly difficult to measure in environmental samples because they are a-emitters and therefore necessitate a careful separation before any measurement, either using radiometric methods or ICP-SMS. Recent developments in extraction chromatography resins such as EichromR TRU and TEVA have resolved many of the analytical problems but drawbacks such as low recovery and spectral interferences still occasionally occur. Here, we report on the use of the new EichromR DGA resin in association with TEVA resin and high pressure microwave acid leaching for the sequential determination of plutonium and americium in environmental samples. The method results in average recoveries of 83 ± 15% for plutonium and 73 ± 22% for americium (n = 60), and a less than 10% deviation from reference values of four IAEA reference materials and three samples from intercomparisons exercises. The method is also suitable for measuring 239Pu in water samples at the μBq/l level, if ICP-SMS is used for the measurement. (author)

  3. An experimental study of americium-241 biokinetics in the Lobster Homarus Gammarus. Analysis of the accumulation/storage and detoxification processes at the subcellular level

    International Nuclear Information System (INIS)

    An experimental study of americium-241 kinetics has been conducted in the lobster Homarus gammmarus. The investigations were conducted at all the levels from the whole body to the subcellular and molecular levels. The animals were contaminated by a single or chronic ingestion of 241 Am labelled mussels. Assessments of accumulation, elimination and distribution of the radionuclide were established on organisms kept in the laboratory; they made it possible to demonstrate the importance of the digestive gland in the radionuclide transfer pathways. The preliminary results led to structural then ultrastructural investigations of the digestive gland in association with radioautographic studies and cellular extractions methods. Four cellular types were demonstrated, only two of them being implied in the radionuclide retention, the former being responsible for americium intake and the latter for its long-term retention. By means of biochemical techniques, subcellular accumulation was studied and the organelles implied in the nuclide retention were specified. Finally, a method of cellular nuclei dissociation was developed; it made it possible to analyse the molecular nature of americium ligands and to demonstrate the function of the protein nuclear matrix in the nuclide retention

  4. Comparative XRPD and XAS study of the impact of the synthesis process on the electronic and structural environments of uranium–americium mixed oxides

    Energy Technology Data Exchange (ETDEWEB)

    Prieur, D., E-mail: dam.prieur@gmail.com [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Lebreton, F. [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze cedex (France); Martin, P.M. [CEA, DEN, DEC/SESC/LLCC, 13108 Saint-Paul-Lez-Durance cedex (France); Caisso, M. [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze cedex (France); Butzbach, R. [Helmholtz Zentrum Dresden Rossendorf (HZDR), Institute of Radiochemistry, P.O. Box 10119, 01314 Dresden (Germany); Somers, J. [European Commission, Joint Research Centre, Institute for Transuranium Elements, P.O. Box 2340, D-76125 Karlsruhe (Germany); Delahaye, T. [CEA, DEN, DTEC/SDTC/LEMA, 30207 Bagnols-sur-Cèze cedex (France)

    2015-10-15

    Uranium–americium mixed oxides are potential compounds to reduce americium inventory in nuclear waste via a partitioning and transmutation strategy. A thorough assessment of the oxygen-to-metal ratio is paramount in such materials as it determines the important underlying electronic structure and phase relations, affecting both thermal conductivity of the material and its interaction with the cladding and coolant. In 2011, various XAS experiments on U{sub 1−x}Am{sub x}O{sub 2±δ} samples prepared by different synthesis methods have reported contradictory results on the charge distribution of U and Am. This work alleviates this discrepancy. The XAS results confirm that, independently of the synthesis process, the reductive sintering of U{sub 1−x}Am{sub x}O{sub 2±δ} leads to the formation of similar fluorite solid solution indicating the presence of Am{sup +III} and U{sup +V} in equimolar proportions. - Graphical abstract: Formation of (U{sup IV/V},Am{sup III})O{sup 2} solid solution by sol–gel and by powder metallurgy. - Highlights: • Uranium–americium mixed oxides were synthesized by sol–gel and powder metallurgy. • Fluorite solid solutions with similar local environment have been obtained. • U{sup V} and Am{sup III} are formed in equimolar proportions.

  5. Production Cycle for Large Scale Fission Mo-99 Separation by the Processing of Irradiated LEU Uranium Silicide Fuel Element Targets

    Directory of Open Access Journals (Sweden)

    Abdel-Hadi Ali Sameh

    2013-01-01

    Full Text Available Uranium silicide fuels proved over decades their exceptional qualification for the operation of higher flux material testing reactors with LEU elements. The application of such fuels as target materials, particularly for the large scale fission Mo-99 producers, offers an efficient and economical solution for the related facilities. The realization of such aim demands the introduction of a suitable dissolution process for the applied U3Si2 compound. Excellent results are achieved by the oxidizing dissolution of the fuel meat in hydrofluoric acid at room temperature. The resulting solution is directly behind added to an over stoichiometric amount of potassium hydroxide solution. Uranium and the bulk of fission products are precipitated together with the transuranium compounds. The filtrate contains the molybdenum and the soluble fission product species. It is further treated similar to the in-full scale proven process. The generated off gas stream is handled also as experienced before after passing through KOH washing solution. The generated alkaline fluoride containing waste solution is noncorrosive. Nevertheless fluoride can be selectively bonded as in soluble CaF2 by addition of a mixture of solid calcium hydroxide calcium carbonate to the sand cement mixture used for waste solidification. The generated elevated amounts of LEU remnants can be recycled and retargeted. The related technology permits the minimization of the generated fuel waste, saving environment, and improving processing economy.

  6. Crystal Structure and Thermoelectric Properties of Lightly Vanadium-Substituted Higher Manganese Silicides (Mn1-x V x )Si γ )

    Science.gov (United States)

    Miyazaki, Yuzuru; Hamada, Haruki; Hayashi, Kei; Yubuta, Kunio

    2016-09-01

    To further enhance the thermoelectric (TE) properties of higher manganese silicides (HMSs), dissipation of layered precipitates of MnSi phase as well as optimization of hole carrier concentration are critical. We have prepared a lightly vanadium-substituted solid solution of HMS, (Mn1-x V x )Si γ , by a melt growth method. A 2% substitution of manganese with vanadium is found to dissipate MnSi precipitates effectively, resulting in a substantial increase in the electrical conductivity from 280 S/cm to 706 S/cm at 800 K. The resulting TE power factor reaches 2.4 mW/K2-m at 800 K, more than twice that of the V-free sample. The total thermal conductivity did not change significantly with increasing x owing to a reduction of the lattice contribution. As a consequence, the dimensionless figure of merit zT of the melt-grown samples increased from 0.26 ± 0.01 for x = 0 to 0.59 ± 0.01 for x = 0.02 at around 800 K.

  7. Use of radioanalytical methods for determination of uranium, neptunium, plutonium, americium and curium isotopes in radioactive wastes

    International Nuclear Information System (INIS)

    Activated charcoal is a common type of radioactive waste that contains high concentrations of fission and activation products. The management of this waste includes its characterization aiming the determination and quantification of the specific radionuclides including those known as Difficult-to-Measure Radionuclides (RDM). The analysis of the RDM's generally involves complex radiochemical analysis for purification and separation of the radionuclides, which are expensive and time-consuming. The objective of this work was to define a methodology for sequential analysis of the isotopes of uranium, neptunium, plutonium, americium and curium present in a type of radioactive waste, evaluating chemical yield, analysis of time spent, amount of secondary waste generated and cost. Three methodologies were compared and validated that employ ion exchange (TI + EC), extraction chromatography (EC) and extraction with polymers (ECP). The waste chosen was the activated charcoal from the purification system of primary circuit water cooling the reactor IEA-R1. The charcoal samples were dissolved by acid digestion followed by purification and separation of isotopes with ion exchange resins, extraction and chromatographic extraction polymers. Isotopes were analyzed on an alpha spectrometer, equipped with surface barrier detectors. The chemical yields were satisfactory for the methods TI + EC and EC. ECP method was comparable with those methods only for uranium. Statistical analysis as well the analysis of time spent, amount of secondary waste generated and cost revealed that EC method is the most effective for identifying and quantifying U, Np, Pu, Am and Cm present in charcoal. (author)

  8. Intramolecular sensitization of americium luminescence in solution: shining light on short-lived forbidden 5f transitions.

    Science.gov (United States)

    Sturzbecher-Hoehne, M; Yang, P; D'Aléo, A; Abergel, R J

    2016-06-14

    The photophysical properties and solution thermodynamics of water soluble trivalent americium (Am(III)) complexes formed with multidentate chromophore-bearing ligands, 3,4,3-LI(1,2-HOPO), Enterobactin, and 5-LIO(Me-3,2-HOPO), were investigated. The three chelators were shown to act as antenna chromophores for Am(III), generating sensitized luminescence emission from the metal upon complexation, with very short lifetimes ranging from 33 to 42 ns and low luminescence quantum yields (10(-3) to 10(-2)%), characteristic of Near Infra-Red emitters in similar systems. The specific emission peak of Am(III) assigned to the (5)D1 → (7)F1 f-f transition was exploited to characterize the high proton-independent stability of the complex formed with the most efficient sensitizer 3,4,3-LI(1,2-HOPO), with a log β110 = 20.4 ± 0.2 value. In addition, the optical and solution thermodynamic features of these Am(III) complexes, combined with density functional theory calculations, were used to probe the influence of electronic structure on coordination properties across the f-element series and to gain insight into ligand field effects.

  9. Nano-cerium vanadate: a novel inorganic ion exchanger for removal of americium and uranium from simulated aqueous nuclear waste.

    Science.gov (United States)

    Banerjee, Chayan; Dudwadkar, Nilesh; Tripathi, Subhash Chandra; Gandhi, Pritam Maniklal; Grover, Vinita; Kaushik, Chetan Prakash; Tyagi, Avesh Kumar

    2014-09-15

    Cerium vanadate nanopowders were synthesized by a facile low temperature co-precipitation method. The product was characterized by X-ray diffraction and transmission electron microscopy and found to consist of ∼25 nm spherical nanoparticles. The efficiency of these nanopowders for uptake of alpha-emitting radionuclides (233)U (4.82 MeV α) and (241)Am (5.49 MeV α, 60 keV γ) has been investigated. Thermodynamically and kinetically favorable uptake of these radionuclides resulted in their complete removal within 3h from aqueous acidic feed solutions. The uptake capacity was observed to increase with increase in pH as the zeta potential value decreased with the increase in pH but effect of ionic strength was insignificant. Little influence of the ions like Sr(2+), Ru(3+), Fe(3+), etc., in the uptake process indicated CeVO4 nanopowders to be amenable for practical applications. The isotherms indicated predominant uptake of the radioactive metal ions in the solid phase of the exchanger at lower feed concentrations and linear Kielland plots with positive slopes indicated favorable exchange of the metal ions with the nanopowder. Performance comparison with the other sorbents reported indicated excellent potential of nano-cerium vanadate for removing americium and uranium from large volumes of aqueous acidic solutions.

  10. Distribution of plutonium, americium, and several rare earth fission product elements between liquid cadmium and LiCl-KCl eutectic

    International Nuclear Information System (INIS)

    Separation factors were measured that describe the partition between molten cadmium and molten LiCl-KCl eutectic of plutonium, americium, praseodymium, neodymium, cerium, lanthanum, gadolinium, dysprosium, and yttrium. The temperature range was 753-788 K, and the range of concentrations was that allowed by the sensitivity of the chemical analysis methods. Mean separation factors were derived for Am-Pu, Nd-Am, Nd-Pu, Nd-Pr, Gd-La, Dy-La, La-Ce, La-Nd, Y-La, and Y-Nd. Where previously published data were available, agreement was good. For convenience, the following series of separation factors relative to plutonium was derived by combining the measured separation factors: Pu, 1.00 (basis); Am, 1.54; Pr, 22.0; Nd, 23.4; Ce, 26; La, 70; Gd, 77; Dy, 270; Y, 3000. These data are used in calculating the distribution of the actinide and rare earth elements in the prochemical reprocessing of spent fuel from the Integral Fast Reactor. (orig.)

  11. Evaluation of synthetic water-soluble metal-binding polymers with ultrafiltration for selective concentration of americium and plutonium

    International Nuclear Information System (INIS)

    Routine counting methods and ICP-MS are unable to directly measure the new US Department of Energy (DOE) regulatory level for discharge waters containing alpha-emitting radionuclides of 30 pCi/L total alpha or the 0.05 pCi/L regulatory level for Pu or Am activity required for surface waters at the Rocky Flats site by the State of Colorado. This inability indicates the need to develop rapid, reliable, and robust analytical techniques for measuring actinide metal ions, particularly americium and plutonium. Selective separation or preconcentration techniques would aid in this effort. Water-soluble metal-binding polymers in combination with ultrafiltration are shown to be an effective method for selectively removing dilute actinide ions from acidic solutions of high ionic strength. The actinide-binding properties of commercially available water-soluble polymers and several polymers which have been reported in the literature were evaluated. The functional groups incorporated in the polymers were pyrrolidone, amine, oxime, and carboxylic, phosphonic, or sulfonic acid. The polymer containing phosphonic acid groups gave the best results with high distribution coefficients and concentration factors for 241Am(III) and 238Pu(III)/(IV) at pH 4 to 6 and ionic strengths of 0.1 to 4

  12. Characteristics of plutonium and americium contamination at the former U.K. atomic weapons test ranges at Maralinga and Emu

    International Nuclear Information System (INIS)

    Physico-chemical studies on environmental plutonium are described, which provide data integral to an assessment of dose for the inhalation of artificial actinides by Australian Aborigines living a semi-traditional lifestyle at Maralinga and Emu, sites of U.K. atomic weapons tests between 1953 and 1963. The most significant area, from a radiological perspective, is the area contaminated by plutonium in a series of ''one point'' safety trials in which large quantities of plutonium were dispersed explosively at a location known as Taranaki. The activity distribution of plutonium and americium with particle size is quite different from the mass distribution, as a considerably higher proportion of the activity is contained in the finer (inhalable) fraction than of the mass. Except in areas which were disturbed through ploughing during a cleanup in 1967, most the activity remains in the top 1 cm of the surface. Much of the activity is in particulate form, even at distances > 20 km from the firing sites, and discrete particles have been located even at distances beyond 100 km. Data are presented which permit the assessment of annual committed doses through the inhalation pathway, for Aborigines living a semi-traditional lifestyle in the areas affected by the Taranaki firings in particular. (author)

  13. Modification by H-termination in growth process of titanium silicide on Si(0 0 1)-2 x 1 observed with scanning tunneling microscopy

    International Nuclear Information System (INIS)

    Formation processes of titanium silicide on hydrogen-terminated H/Si(0 0 1)-2 x 1 surface are studied at the atomic scale with a scanning tunneling microscopy (STM). Square-shaped nanoislands were observed on the Ti/H/Si(0 0 1) surface after annealed at 873-1073 K. These are the epitaxial nanoislands moderately grown due to the local orientation relationship between C49-TiSi2 and Si(0 0 1), because passivation by surface hydrogen on Si(0 0 1) suppresses active and complex bond formation of Ti-Si.

  14. The effect of silicide ceramic coatings on the high-temperature strength and plasticity of niobium alloys of the Nb-W-Mo-Zr system

    International Nuclear Information System (INIS)

    A study is made into short-term rupture strength and plasticity of 5VMTs alloy of Nb-W-Mo-Zr system and a 5VMTs-silicide ceramic coating composite material in vacuum, inert environment and in the air within a temperature range of 290-2070 K. The kinetics of defect generation and development both in the protective coating and the matrix is studied. The values of limiting plastic strains are determined at which the composite materials preserves its carrying capacity in high temperature aggressive and oxidizing gaseous media

  15. The role of natural organic matter in the migration behaviour of americium in the Boom Clay - Part 1: migration experiments

    International Nuclear Information System (INIS)

    Full text of publication follows: In demonstrating the suitability of Boom Clay as reference site for studying the disposal of radioactive waste, the role of the relatively high amount of Natural Organic Matter (NOM) present in the Boom Clay on the mobility of critical radionuclides needs to be investigated thoroughly. It is generally accepted that trivalent actinides and lanthanides form strong complexes with humic substances. Complexation of these trivalent radionuclides with NOM present in the Boom Clay may therefore have two opposite effects. If complexed by the aqueous phase NOM (the mobile NOM), the radionuclide transport will be governed by the mobility of these dissolved radionuclide- NOM species. If complexed by the solid phase NOM (the immobile NOM) the migration will be retarded. One of the aims of the EC projects TRANCOM-Clay and TRANCOM-II was to investigate the role of mobile NOM as radionuclide carrier in order to develop a conceptual model for inclusion in a performance assessment (PA) model. The migration behaviour of Americium (used as an analogue for the critical radionuclide Pu) was investigated by complexing 241Am with radiolabelled (14C-labelled) NOM before passing through undisturbed Boom Clay cores contained in columns. The use of two different radionuclides, allows the migration behaviour of both the NOM and the Am to be followed. The results of the migration experiments showed that the Am-NOM complexes dissociated when they came into contact with Boom Clay and that the bulk of Am became immobilised (either as Am complexed to immobile NOM or sorbed to the mineral phase). Only a small percentage of the complex persisted as 'stabilised' Am-OM complex which exhibited slow dissociation kinetics upon moving through the Boom Clay. When the applied radionuclide source also contains Am in the form of an inorganic solid phase (when Am is applied above the solubility limit), a continuous source of Am exists to form 'temporarily stabilised' Am

  16. Experimental study of Americium-241 biokinetics in Homarus Gammarus lobster. Analysis of the accumulation and detoxication mechanisms at the sub-cellular level; Etude experimentale des biocinetiques de l`americium-241 chez le homard homarus gammarus. Analyse des mecanismes d`accumulation et de detoxication au niveau subcellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Paquet, F.

    1991-12-01

    The Americium 241 radioelement accumulation and elimination rate and mechanisms in the lobster organism have been experimentally studied; incorporation and detoxification capacities of each organ are evaluated. The existence of various biological compartments is shown; the major role of the digestive gland in accumulation of the radioelement, its distribution towards the various organs, and its resorption is comprehensively described, with an analysis at the subcellular and molecular levels. 401 p., 65 fig., 43 tab., 428 ref.

  17. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Zhihong Tang

    2007-12-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti{sub 5}Si{sub 3}-based alloys was investigated. Oxidation behavior of Ti{sub 5}Si{sub 3}-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti{sub 5}Si{sub 3} by nucleation and growth of nitride subscale. Ti{sub 5}Si{sub 3.2} and Ti{sub 5}Si{sub 3}C{sub 0.5} alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi{sub 2} coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo{sub 3}Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo{sub 3}Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nb{sub ss} (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} Nb{sub SS} + NbB was determined to occur at 2104 {+-} 5 C by DTA.

  18. Nano-cerium vanadate: A novel inorganic ion exchanger for removal of americium and uranium from simulated aqueous nuclear waste

    Energy Technology Data Exchange (ETDEWEB)

    Banerjee, Chayan; Dudwadkar, Nilesh [Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tripathi, Subhash Chandra, E-mail: sctri001@gmail.com [Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Gandhi, Pritam Maniklal [Fuel Reprocessing Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Grover, Vinita [Waste Management Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Kaushik, Chetan Prakash [Chemistry Division, Bhabha Atomic Research Centre, Mumbai 400085 (India); Tyagi, Avesh Kumar, E-mail: aktyagi@barc.gov.in [Waste Management Division, Bhabha Atomic Research Centre, Mumbai 400085 (India)

    2014-09-15

    Highlights: • Template free, low temperature synthesis of CeVO{sub 4} nanopowders. • Thermodynamically and kinetically favourable uptake of Am(III) and U(VI) exhibited. • K{sub d} and ΔG° values for Am(III) and U(VI) uptake in pH 1–6 are reported. • Interdiffusion coefficients and zeta potential values in pH 1–6 are reported. • Possible application in low level aqueous nuclear waste remediation. - Abstract: Cerium vanadate nanopowders were synthesized by a facile low temperature co-precipitation method. The product was characterized by X-ray diffraction and transmission electron microscopy and found to consist of ∼25 nm spherical nanoparticles. The efficiency of these nanopowders for uptake of alpha-emitting radionuclides {sup 233}U (4.82 MeV α) and {sup 241}Am (5.49 MeV α, 60 keV γ) has been investigated. Thermodynamically and kinetically favorable uptake of these radionuclides resulted in their complete removal within 3 h from aqueous acidic feed solutions. The uptake capacity was observed to increase with increase in pH as the zeta potential value decreased with the increase in pH but effect of ionic strength was insignificant. Little influence of the ions like Sr{sup 2+}, Ru{sup 3+}, Fe{sup 3+}, etc., in the uptake process indicated CeVO{sub 4} nanopowders to be amenable for practical applications. The isotherms indicated predominant uptake of the radioactive metal ions in the solid phase of the exchanger at lower feed concentrations and linear Kielland plots with positive slopes indicated favorable exchange of the metal ions with the nanopowder. Performance comparison with the other sorbents reported indicated excellent potential of nano-cerium vanadate for removing americium and uranium from large volumes of aqueous acidic solutions.

  19. Plutonium, americium and radiocaesium in the marine environment close to the Vandellos I nuclear power plant before decommissioning

    International Nuclear Information System (INIS)

    The Vandellos nuclear power plant (NPP), releasing low-level radioactive liquid waste to the Mediterranean Sea, is the first to be decommissioned in Spain, after an incident which occurred in 1989. The presence, distribution and uptake of various artificial radionuclides (radiocaesium, plutonium and americium) in the environment close to the plant were studied in seawater, bottom sediments and biota, including Posidonia oceanica, fish, crustaceans and molluscs. Seawater, sediments and Posidonia oceanica showed enhanced levels in the close vicinity of the NPP, although the effect was restricted to its near environment. Maximum concentrations in seawater were 11.6±0.5 Bq m-3 and 16.9±1.2 mBq m-3 for 137Cs and 239,240Pu, respectively. When sediment concentrations were normalized to excess 210Pb, they showed both the short-distance transport of artificial radionuclides from the Vandellos plant and the long-distance transport of 137Cs from the Asco NPP. Posidonia oceanica showed the presence of various gamma-emitters attributed to the impact of the Chernobyl accident, on which the effect of the NPP was superimposed. Seawater, sediment and Posidonia oceanica collected near the plant also showed an enhancement of the plutonium isotopic ratio above the fallout value. The uptake of these radionuclides by marine organisms was detectable but limited. Pelagic fish showed relatively higher 137Cs concentrations and only in the case of demersal fish was the plutonium isotopic ratio increased. The reported levels constitute a set of baseline values against which the impact of the decommissioning operations of the Vandellos I NPP can be studied

  20. Molten salt extraction (MSE) of americium from plutonium metal in CaCl2-KCl-PuCl3 and CaCl2-PuCl3 salt systems

    International Nuclear Information System (INIS)

    Molten salt extraction (MSE) of americium-241 from reactor-grade plutonium has been developed using plutonium trichloride salt in stationary furnaces. Batch runs with oxidized and oxide-free metal have been conducted at temperature ranges between 750 and 945C, and plutonium trichloride concentrations from one to one hundred mole percent. Salt-to-metal ratios of 0.10, 0.15, and 0 30 were examined. The solvent salt was either eutectic 74 mole percent CaCl2 endash 26 mole percent KCl or pure CaCl2. Evidence of trivalent product americium, and effects of temperature, salt-to-metal ratio, and oxide contamination on the americium extraction efficiency are given. 24 refs, 20 figs, 13 tabs

  1. Transfer across the human gut of environmental plutonium, americium, cobalt, caesium and technetium: studies with cockles (Cerastoderma edule) from the Irish Sea.

    Science.gov (United States)

    Hunt, G J

    1998-06-01

    Our previous studies have indicated lower values of the gut transfer factor ('f1 values') for plutonium and americium in winkles (Littorina littorea) than adopted by ICRP. The present study was undertaken primarily to investigate whether this observation extends to other species. Samples of cockles (Carastoderma edule) from Ravenglass, Cumbria were eaten by volunteers who provided 24 h samples of urine and faeces. Urine samples indicated f1 values for cockles which were higher than for winkles; for plutonium these ranged overall up to 7 x 10(-4) with an arithmetic mean in the range (2-3) x 10(-4), and for americium up to 2.6 x 10(-4) with an arithmetic mean of 1.2 x 10(-4). Limited data based on volunteers eating cockles from the Solway suggest that f1 values for americium may be greater at distance from Sellafield. The measured values compare with 5 x 10(-4) used by the ICRP for environmental forms of both elements, which would appear to provide adequate protection when calculating doses from Cumbrian cockles. Data for other nuclides were obtained by analysing faecal samples from the volunteers who ate the Ravenglass cockles. Cobalt-60 showed an f1 value in the region of 0.2, twice the value currently used by ICRP. For 137Cs, variabilities were indicated in the range 0.08 to 0.43, within the ICRP value of f1 = 1.0. Technetium-99 gave f1 values up to about 0.6, in reasonable conformity with the ICRP value of 0.5.

  2. Transfer across the human gut of environmental plutonium, americium, cobalt, caesium and technetium: studies with cockles (Cerastoderma edule) from the Irish Sea

    Energy Technology Data Exchange (ETDEWEB)

    Hunt, G.J. [CEFAS Laboratory, Lowestoft, Suffolk NR33 0HT (United Kingdom)

    1998-06-01

    Our previous studies have indicated lower values of the gut transfer factor ('f{sub L} values') for plutonium and americium in winkles (Littorina littorea) than adopted by ICRP. The present study was undertaken primarily to investigate whether this observation extends to other species. Samples of cockles (Cerastoderma edule) from Ravenglass, Cumbria were eaten by volunteers who provided 24 samples of urine and faeces. Urine samples indicated f{sub L} values for cockles which were higher than for winkles; for plutonium these ranged overall up to 7x10{sup -4} with an arithmetic mean in the range (2-3)x10{sup -4}, and for americium up to 2.6x10{sup -4} with an arithmetic mean of 1.2x10{sup -4}. Limited data based on volunteers eating cockles from the Solway suggest that f{sub L} values for americium may be greater at distance from Sellafield. The measured values compare with 5x10{sup -4} used by the ICRP for environmental forms of both elements, which would appear to provide adequate protection when calculating doses from Cumbrian cockles. Data for other nuclides were obtained by analysing faecal samples from the volunteers who ate the Ravenglass cockles. Cobalt-60 showed an f{sub L} value in the region of 0.2, twice the value currently used by ICRP. For {sup 137}Cs, variabilities were indicated in the range 0.08 to 0.43, within the ICRP value of f{sub L}=1.0. Technetium-99 gave f{sub L} values up to about 0.6, in reasonable conformity with the ICRP value of 0.5. (author)

  3. Determination by gamma-ray spectrometry of the plutonium and americium content of the Pu/Am separation scraps. Application to molten salts; Determination par spectrometrie gamma de la teneur en plutonium et en americium de produits issus de separation Pu/Am. Application aux bains de sels

    Energy Technology Data Exchange (ETDEWEB)

    Godot, A. [CEA Valduc, Dept. de Traitement des Materiaux Nucleaires, 21 - Is-sur-Tille (France); Perot, B. [CEA Cadarache, Dept. de Technologie Nucleaire, Service de Modelisation des Transferts et Mesures Nucleaires, 13 - Saint-Paul-lez-Durance (France)

    2005-07-01

    Within the framework of plutonium recycling operations in CEA Valduc (France), americium is extracted from molten plutonium metal into a molten salt during an electrolysis process. The scraps (spent salt, cathode, and crucible) contain extracted americium and a part of plutonium. Nuclear material management requires a very accurate determination of the plutonium content. Gamma-ray spectroscopy is performed on Molten Salt Extraction (MSE) scraps located inside the glove box, in order to assess the plutonium and americium contents. The measurement accuracy is influenced by the device geometry, nuclear instrumentation, screens located between the sample and the detector, counting statistics and matrix attenuation, self-absorption within the spent salt being very important. The purpose of this study is to validate the 'infinite energy extrapolation' method employed to correct for self-attenuation, and to detect any potential bias. We present a numerical study performed with the MCNP computer code to identify the most influential parameters and some suggestions to improve the measurement accuracy. A final uncertainty of approximately 40% is achieved on the plutonium mass. (authors)

  4. An experimental study of americium-241 biokinetics in the Lobster Homarus Gammarus. Analysis of the accumulation/storage and detoxification processes at the subcellular level; Etude experimentale des biocinetiques de l`americium-241 chez le homard homarus gammarus. Analyse des mecanismes d`accumulation et de detoxication au niveau subcellulaire

    Energy Technology Data Exchange (ETDEWEB)

    Paquet, F.

    1993-01-01

    An experimental study of americium-241 kinetics has been conducted in the lobster Homarus gammmarus. The investigations were conducted at all the levels from the whole body to the subcellular and molecular levels. The animals were contaminated by a single or chronic ingestion of {sup 241} Am labelled mussels. Assessments of accumulation, elimination and distribution of the radionuclide were established on organisms kept in the laboratory; they made it possible to demonstrate the importance of the digestive gland in the radionuclide transfer pathways. The preliminary results led to structural then ultrastructural investigations of the digestive gland in association with radioautographic studies and cellular extractions methods. Four cellular types were demonstrated, only two of them being implied in the radionuclide retention, the former being responsible for americium intake and the latter for its long-term retention. By means of biochemical techniques, subcellular accumulation was studied and the organelles implied in the nuclide retention were specified. Finally, a method of cellular nuclei dissociation was developed; it made it possible to analyse the molecular nature of americium ligands and to demonstrate the function of the protein nuclear matrix in the nuclide retention.

  5. Dissertation on the computer-based exploitation of a coincidence multi parametric recording. Application to the study of the disintegration scheme of Americium 241

    International Nuclear Information System (INIS)

    After having presented the meaning of disintegration scheme (alpha and gamma emissions, internal conversion, mean lifetime), the author highlights the benefits of the use of multi-parametric chain for the recording of correlated parameters, and of the use of a computer for the analysis of bi-parametric information based on contour lines. Using the example of Americium 241, the author shows how these information are obtained (alpha and gamma spectrometry, time measurement), how they are chosen, coded, analysed and stored, and then processed by contour lines

  6. Revealing lithium-silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy.

    Science.gov (United States)

    Ogata, K; Salager, E; Kerr, C J; Fraser, A E; Ducati, C; Morris, A J; Hofmann, S; Grey, C P

    2014-01-01

    Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies.

  7. Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content

    Science.gov (United States)

    Redondo-Cubero, A.; Galiana, B.; Lorenz, K.; Palomares, FJ; Bahena, D.; Ballesteros, C.; Hernandez-Calderón, I.; Vázquez, L.

    2016-11-01

    We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe+ ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.

  8. Revealing lithium-silicide phase transformations in nano-structured silicon-based lithium ion batteries via in situ NMR spectroscopy.

    Science.gov (United States)

    Ogata, K; Salager, E; Kerr, C J; Fraser, A E; Ducati, C; Morris, A J; Hofmann, S; Grey, C P

    2014-01-01

    Nano-structured silicon anodes are attractive alternatives to graphitic carbons in rechargeable Li-ion batteries, owing to their extremely high capacities. Despite their advantages, numerous issues remain to be addressed, the most basic being to understand the complex kinetics and thermodynamics that control the reactions and structural rearrangements. Elucidating this necessitates real-time in situ metrologies, which are highly challenging, if the whole electrode structure is studied at an atomistic level for multiple cycles under realistic cycling conditions. Here we report that Si nanowires grown on a conducting carbon-fibre support provide a robust model battery system that can be studied by (7)Li in situ NMR spectroscopy. The method allows the (de)alloying reactions of the amorphous silicides to be followed in the 2nd cycle and beyond. In combination with density-functional theory calculations, the results provide insight into the amorphous and amorphous-to-crystalline lithium-silicide transformations, particularly those at low voltages, which are highly relevant to practical cycling strategies. PMID:24488002

  9. Self-organised silicide nanodot patterning by medium-energy ion beam sputtering of Si(100): local correlation between the morphology and metal content.

    Science.gov (United States)

    Redondo-Cubero, A; Galiana, B; Lorenz, K; Palomares, F J; Bahena, D; Ballesteros, C; Hernandez-Calderón, I; Vázquez, L

    2016-11-01

    We have produced self-organised silicide nanodot patterns by medium-energy ion beam sputtering (IBS) of silicon targets with a simultaneous and isotropic molybdenum supply. Atomic force microscopy (AFM) studies show that these patterns are qualitatively similar to those produced thus far at low ion energies. We have determined the relevance of the ion species on the pattern ordering and properties. For the higher ordered patterns produced by Xe(+) ions, the pattern wavelength depends linearly on the ion energy. The dot nanostructures are silicide-rich as assessed by x-ray photoelectron spectroscopy (XPS) and emerge in height due to their lower sputtering yield, as observed by electron microscopy. Remarkably, a long wavelength corrugation is observed on the surface which is correlated with both the Mo content and the dot pattern properties. Thus, as assessed by electron microscopy, the protrusions are Mo-rich with higher and more spaced dots on their surface whereas the valleys are Mo-poor with smaller dots that are closer to each other. These findings indicate that there is a correlation between the local metal content of the surface and the nanodot pattern properties both at the nanodot and the large corrugation scales. These results contribute to advancing the understanding of this interesting nanofabrication method and aid in developing a comprehensive theory of nanodot pattern formation and evolution.

  10. Electrical properties of amorphous and epitaxial Si-rich silicide films composed of W-atom-encapsulated Si clusters

    Energy Technology Data Exchange (ETDEWEB)

    Okada, Naoya, E-mail: okada-naoya@aist.go.jp [Japan Science and Technology Agency, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012 (Japan); Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); Uchida, Noriyuki [Nanoelectronics Research Institute, National Institute of Advanced Industrial Science and Technology, 1-1-1 Higashi, Tsukuba, Ibaraki 305-8562 (Japan); Kanayama, Toshihiko [Institute of Applied Physics, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8573 (Japan); National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, Ibaraki 305-8568 (Japan)

    2015-03-07

    We investigated the electrical properties and derived the energy band structures of amorphous Si-rich W silicide (a-WSi{sub n}) films and approximately 1-nm-thick crystalline WSi{sub n} epitaxial films (e-WSi{sub n}) on Si (100) substrates with composition n = 8–10, both composed of Si{sub n} clusters each of which encapsulates a W atom (WSi{sub n} clusters). The effect of annealing in the temperature range of 300–500 °C was also investigated. The Hall measurements at room temperature revealed that a-WSi{sub n} is a nearly intrinsic semiconductor, whereas e-WSi{sub n} is an n-type semiconductor with electron mobility of ∼8 cm{sup 2}/V s and high sheet electron density of ∼7 × 10{sup 12 }cm{sup −2}. According to the temperature dependence of the electrical properties, a-WSi{sub n} has a mobility gap of ∼0.1 eV and mid gap states in the region of 10{sup 19 }cm{sup −3} eV{sup −1} in an optical gap of ∼0.6 eV with considerable band tail states; e-WSi{sub n} has a donor level of ∼0.1 eV with sheet density in the region of 10{sup 12 }cm{sup −2} in a band gap of ∼0.3 eV. These semiconducting band structures are primarily attributed to the open band-gap properties of the constituting WSi{sub n} cluster. In a-WSi{sub n}, the random network of the clusters generates the band tail states, and the formation of Si dangling bonds results in the generation of mid gap states; in e-WSi{sub n}, the original cluster structure is highly distorted to accommodate the Si lattice, resulting in the formation of intrinsic defects responsible for the donor level.

  11. Characterization of complex carbide–silicide precipitates in a Ni–Cr–Mo–Fe–Si alloy modified by welding

    Energy Technology Data Exchange (ETDEWEB)

    Bhattacharyya, D., E-mail: dhb@ansto.gov.au; Davis, J.; Drew, M.; Harrison, R.P.; Edwards, L.

    2015-07-15

    Nickel based alloys of the type Hastelloy-N™ are ideal candidate materials for molten salt reactors, as well as for applications such as pressure vessels, due to their excellent resistance to creep, oxidation and corrosion. In this work, the authors have attempted to understand the effects of welding on the morphology, chemistry and crystal structure of the precipitates in the heat affected zone (HAZ) and the weld zone of a Ni–Cr–Mo–Fe–Si alloy similar to Hastelloy-N™ in composition, by using characterization techniques such as scanning and transmission electron microscopy. Two plates of a Ni–Cr–Mo–Fe–Si alloy GH-3535 were welded together using a TiG welding process without filler material to achieve a joint with a curved molten zone with dendritic structure. It is evident that the primary precipitates have melted in the HAZ and re-solidified in a eutectic-like morphology, with a chemistry and crystal structure only slightly different from the pre-existing precipitates, while the surrounding matrix grains remained unmelted, except for the zones immediately adjacent to the precipitates. In the molten zone, the primary precipitates were fully melted and dissolved in the matrix, and there was enrichment of Mo and Si in the dendrite boundaries after solidification, and re-precipitation of the complex carbides/silicides at some grain boundaries and triple points. The nature of the precipitates in the molten zone varied according to the local chemical composition. - Graphical abstract: Display Omitted - Highlights: • Ni-based alloy with Cr, Mo, Si, Fe and C was welded, examined with SEM, EBSD, and TEM. • Original Ni{sub 2}(Mo,Cr){sub 4}(Si,C) carbides changed from equiaxed to lamellar shape in HAZ. • Composition and crystal structure remained almost unchanged in HAZ. • Original carbides changed to lamellar Ni{sub 3}(Mo,Cr){sub 3}(Si,C) in some cases in weld metal. • Precipitates were mostly incoherent, but semi-coherent in some cases in weld

  12. Inhaled americium dioxide

    International Nuclear Information System (INIS)

    This project includes experiments to determine the effects of Zn-DTPA therapy on the retention, translocation and biological effects of inhaled 241AmO2. Beagle dogs that received inhalation exposure to 241AmO2 developed leukopenia, clincial chemistry changes associated with hepatocellular damage, and were euthanized due to respiratory insufficiency caused by radiation pneumonitis 120 to 131 days after pulmonary deposition of 22 to 65 μCi 241Am. Another group of dogs that received inhalation exposure to 241AmO2 and were treated daily with Zn-DTPA had initial pulmonary deposition of 19 to 26 μCi 241Am. These dogs did not develop respiratory insufficiency, and hematologic and clinical chemistry changes were less severe than in the non-DTPA-treated dogs

  13. Study of the phase composition of silicide coatings, based on layered Nb-Mo structures, obtained by vacuum-arc deposition

    Science.gov (United States)

    Lozovan, A. A.; Betsofen, S. Ya; Lenkovets, A. S.

    2016-07-01

    A multilayer composite ∼1000 μm in thickness, formed by niobium and molybdenum layers (number of layers n = 230), is obtained by vacuum-arc deposition with subsequent siliconization of the surface layers at a temperature of 1200 °C. Layer-by-layer phase analysis is performed by X-ray diffraction and scanning electron microscopy. It is found that in the surface layers ∼130 μm in thickness, single-phase silicides (Nb x Mo1- x )Si2 are formed with the hexagonal C40 structure (Strukturbericht designations). Alternating layers of solid solutions based on niobium and molybdenum with a body-centered cubic (BCC) lattice are observed within the composite. The formation of solid solutions caused by heating of the coating leads to convergence of the values of the linear thermal expansion coefficient and Young's modulus at the interface between the layers.

  14. Thermite reduction of Ta{sub 2}O{sub 5}/SiO{sub 2} powder mixtures for combustion synthesis of Ta-based silicides

    Energy Technology Data Exchange (ETDEWEB)

    Yeh, C.L., E-mail: clyeh@fcu.edu.tw [Department of Aerospace and Systems Engineering, Feng Chia University, 100 Wenhwa Rd., Seatwen, Taichung 40724, Taiwan (China); Huang, Y.S. [Department of Aerospace and Systems Engineering, Feng Chia University, 100 Wenhwa Rd., Seatwen, Taichung 40724, Taiwan (China)

    2011-05-26

    Highlights: > Solid state combustion involving thermite reduction of Ta{sub 2}O{sub 5} and SiO{sub 2} was firstly performed for the formation of tantalum silicides, including TaSi{sub 2}, Ta{sub 5}Si{sub 3}, Ta{sub 2}Si, and Ta{sub 3}Si. > Two thermite mixtures, Al-Ta{sub 2}O{sub 5} and Al-Ta{sub 2}O{sub 5}-SiO{sub 2}, were adopted and their influence on the combustion characteristics and phase constituents of the final products was studied. > A high degree of phase evolution forming Al{sub 2}O{sub 3}-added TaSi{sub 2} and Ta{sub 5}Si{sub 3} was achieved by adopting the thermite mixture of Al-Ta{sub 2}O{sub 5} in the Ta-Si combustion system. > Variations of the combustion temperature and flame-front velocity with sample stoichiometry were presented. - Abstract: Tantalum silicides (including TaSi{sub 2}, Ta{sub 5}Si{sub 3}, Ta{sub 2}Si, and Ta{sub 3}Si) were prepared by solid state combustion of the Ta-Si reaction system involving thermite reduction of Ta{sub 2}O{sub 5} and SiO{sub 2}. The thermite-based combustion is self-sustaining and contributes to the in situ formation of tantalum silicides along with Al{sub 2}O{sub 3}. The combustion front temperature and propagation velocity increased with the extent of thermite reactions for the systems adopting the thermite mixture of Al-Ta{sub 2}O{sub 5}, while both of them decreased for those using Al, Ta{sub 2}O{sub 5}, and SiO{sub 2} as the thermite reagents. Among four silicide compounds, a better degree of phase evolution was observed for TaSi{sub 2} and Ta{sub 5}Si{sub 3} when compared to that of Ta{sub 2}Si and Ta{sub 3}Si. The XRD analysis indicated the presence of a small amount of Ta{sub 5}Si{sub 3} in the TaSi{sub 2}-Al{sub 2}O{sub 3} composite. On the formation of Ta{sub 5}Si{sub 3} with Al{sub 2}O{sub 3}, the minor phase was Ta{sub 2}Si for the Al-Ta{sub 2}O{sub 5}-containing system. In addition to Ta{sub 2}Si, an intermediate phase TaSi{sub 2} was detected when the Al-Ta{sub 2}O{sub 5}-SiO{sub 2} mixture was

  15. BASIC program to compute uranium density and void volume fraction in laboratory-scale uranium silicide aluminum dispersion plate-type fuel

    International Nuclear Information System (INIS)

    BASIC program simple and easy to operate has been developed to compute uranium density and void volume fraction for laboratory-scale uranium silicide aluminum dispersion plate-type fuel, so called miniplate. An example of the result of calculation is given in order to demonstrate how the calculated void fraction correlates with the microstructural distribution of the void in a miniplate prepared in our laboratory. The program is also able to constitute data base on important parameters for miniplates from experimentally-determined values of density, weight of each constituent and dimensions of miniplates. Utility programs pertinent to the development of the BASIC program are also given which run in the popular MS-DOS environment. All the source lists are attached and brief description for each program is made. (author)

  16. Safety evaluation report related to the evaluation of low-enriched uranium silicide-aluminum dispersion fuel for use in non-power reactors

    Energy Technology Data Exchange (ETDEWEB)

    1988-07-01

    Low-enriched uranium silicide-aluminum dispersion plate-type fuels have been extensively researched and developed under the international program, Reduced Enrichment in Research and Test Reactors. The international effort was led by Argonne National Laboratory (ANL) in the United States. This evaluation is based primarily on reports issued by ANL that discuss and summarize the developmental tests and experiments, including postirradiation examinations, of both miniature and full-sized plates of prototypical fuel compositions. This evaluation concludes that plate-type fuels suitable and acceptable for use in research and test reactors can be fabricated with U/sub 3/Si/sub 2/-Al dispersion compacts with uranium densities up to 4.8 g/cm/sup 3/. 4 refs., 1 fig.

  17. Silicides for VLSI applications

    CERN Document Server

    Murarka, Shyam P

    1983-01-01

    Most of the subject matter of this book has previously been available only in the form of research papers and review articles. I have not attempted to refer to all the published papers. The reader may find it advantageous to refer to the references listed.

  18. Recovery of Americium-241 from lightning rod by the method of chemical treatment; Recuperacion del Americio-241 provenientes de los pararrayos por el metodo de tratamiento quimico

    Energy Technology Data Exchange (ETDEWEB)

    Cruz, W.H., E-mail: wcruz@ipen.gob.pe [Instituto Peruano de Energia Nuclear (GRRA/IPEN), Lima (Peru). Division de Gestion de Residuos Radiactivos

    2013-07-01

    About 95% of the lightning rods installed in the Peruvian territory have set in their structures, pose small amounts of radioactive sources such as Americium-241 ({sup 241}Am), fewer and Radium 226 ({sup 226}Ra) these are alpha emitters and have a half life of 432 years and 1600 years respectively. In this paper describes the recovery of radioactive sources of {sup 241}Am radioactive lightning rods using the conventional chemical treatment method using agents and acids to break down the slides. The {sup 241}Am recovered was as excitation source and alpha particle generator for analysing samples by X Ray Fluorescence, for fixing the stainless steel {sup 241}Am technique was used electrodeposition. (author)

  19. Partitioning studies in China and the separation of americium and fission product rare earths with dialkyl phosphinic acid and its thio-substituted derivatives

    International Nuclear Information System (INIS)

    Studies on the TRPO extractions process for recovering actinides from highly active waste (HAW) and its application to the pretreatment of Chinese HAW are described. The removal of Sr by di-cyclohexyl 18 crown 6 and the removal of Cs by spherical titanium ferrous hexa-cyanate from acidic waste are also described. Results of the extraction of trivalent americium and fission product rare earths (FPREs) by dialkyl-phosphinic, dialkyl-mono-thio-phosphinic and dialkyl-di-thio-phosphinic acids are reported. Dialkyl-thio-phosphinic acid (commercial product Cyanex 301, alkyl =2, 4, 4-methyl-pentyl) shows very high selectivity towards Am. Using 1M Cyanex 301 -kerosene as extractant, 99.9 % Am can be separated from 0.5M(Pr+Nd)(NO3)3 solution with 3-4 extraction stages and 3-4 scrubbing stages. (authors)

  20. Theoretical and experimental study of the bio-geochemical behaviour of americium 241 in simplified rhizosphere conditions. Application to a calcareous agricultural soil

    International Nuclear Information System (INIS)

    Americium 241, is one of the most radio-toxic contaminant produced during the nuclear fuel cycle. It can be found in all environmental compartments, in particular the soils. The main goals of this study are to identify, quantify and model the effect of the main factors controlling the mobility of 241Am in the rhizosphere and the agricultural soils. The physico-chemical parameters of the soil and of the soil solution, the potential role of microorganisms on the sorption-desorption processes, and the speciation of americium in solution have been more particularly studied. 241Am remobilization has been studied at the laboratory using leaching experiments performed in controlled conditions on reworked calcareous soils artificially contaminated with 241Am. The soil samples have been washed out in different hydrodynamic conditions by solutions with various compositions. The eluted solution has been analyzed (pH, conductivity, ionic composition, Fetot, organic acids, 241Am) and its bacterial biomass content too. The overall results indicate that 241Am remobilization is contrasted and strongly linked with the condition under study (pH, ionic strength, glucose and/or citrate concentration). Therefore, a solution in equilibrium with the soil or containing small exudate concentrations (10-4 M) re-mobilizes only a very small part of the americium fixed on the solid phase. The desorption of 241Am corresponds to a solid/liquid coefficient of partition (Kd) of about 105 L.kg-1. A significant addition of glucose induces an important dissolution of soil carbonates by the indirect action of microorganisms, but does not significantly favor the 241Am remobilization. On the other hand, the presence of strong citrate concentrations (≥ 10-2 M) allows 300 to 10000 time greater re-mobilizations by the complexing of 241Am released after the dissolution of the carrying phases. Finally, the colloidal transport of 241Am has been systematically observed in a limited but significant extend and

  1. Safe handling of kilogram amounts of fuel-grade plutonium and of gram amounts of plutonium-238, americium-241 and curium-244

    International Nuclear Information System (INIS)

    During the past 10 years about 600 glove-boxes have been installed at the Institute for Transuranium Elements at Karlsruhe. About 80% of these glove-boxes have been designed and equipped for handling 100-g to 1-kg amounts of 239Pu containing 8-12% 240Pu (low-exposure plutonium). A small proportion of the glove-boxes is equipped with additional shielding in the form of lead sheet or lead glass for work with recycled plutonium. In these glove-boxes gram-amounts of 241Am have also been handled for preparation of Al-Am targets using tongs and additional shielding inside the glove-boxes themselves. Water- and lead-shielded glove-boxes equipped with telemanipulators have been installed for routine work with gram-amounts of 241Am, 243Am and 244Cm. A prediction of the expected radiation dose for the personnel is difficult and only valid for a preparation procedure with well-defined preparation steps, owing to the fact that gamma dose-rates depend strongly upon proximity and source seize. Gamma radiation dose measurements during non-routine work for 241Am target preparation showed that handling of gram amounts leads to a rather high irradiation dose for the personnel, despite lead or steel glove-box shielding and shielding within the glove-boxes. A direct glove-hand to americium contact must be avoided. For all glove-handling of materials with gamma radiation an irradiation control of the forearms of the personnel by, for example, thermoluminescence dosimeters is necessary. Routine handling of americium and curium should be executed with master-slave equipment behind neutron and gamma shielding. (author)

  2. AISI304不锈钢表面硅化物渗层的制备与抗氧化性能%Preparation of silicide layer on AISI 304 stainless steel and oxidation resistance

    Institute of Scientific and Technical Information of China (English)

    安亮; 贾建刚; 马勤; 李鹏

    2011-01-01

    采用ω(NaCl)∶ω(KCl)∶ω(NaF)=2∶2∶1(摩尔比,下同)的中性熔融盐作为载体,ω(Na2SiF6)∶ω(Si)=8∶2粉末做为渗硅剂,800℃下渗硅10 h可实现在AISI 304不锈钢表面形成厚度约500μm的富含Cr、Ni合金元素的Fe3Si型硅化物渗层。采用X射线衍射仪(XRD)分析了渗硅层的物相组成,用附带能量色散谱仪(EDS)附件的扫描电子显微镜(SEM)研究了渗层截面的形貌和成分。结果表明,渗层以Fe3Si相为主,Cr在渗层中含量低于其在304不锈钢基体中含量,而Fe和Ni在%Fe3Si type silicide layer containing Cr and Ni alloying elements with a thickness of about 500 μm on AISI 304 stainless steel were formed in molten salts at 800 ℃ for 10 h using molten mixture of ω(Na2SiF6)∶ωSi=8∶2 as siliconizing agent and the molten halogenide of alkali metals of ω(NaCl)∶ω(KCl)∶ω(NaF)=2∶2∶1 as siliconizing agent carrier.The phase of the silicide layer was analyzed by X-ray diffraction.The micro structure and composition of the silicide layer were studied by scanning electron microscope(SEM) with energy dispersive X-ray spectrometer(EDS)attachment.The results show that the silicide layer mainly consists of Fe3Si.The content of Cr in silicide layer is lower than in AISI 304 steel matrix,while the same contents of Fe and Ni in the layer and in the matrix are observed.The oxidation kinetic curves of the Fe3Si type silicide layer at both 800 ℃ and 900 ℃ obey a parabolic rule.The high temperature oxidation properties of the silicide layer are a little better than that of the AISI 304 steel matrix at 800 ℃.A catastrophic failure of AISI 304 steel occurs at 900 ℃,while the high temperature oxidation properties of the silicide layer at 900 ℃ are better than that at 800 ℃.The composite oxide film containing SiO2 and Cr3O4 resuled from the uphill diffusion of Cr and Si at 900 ℃ accounts for the excellent high temperature

  3. Actinide Oxidation State and O/M Ratio in Hypostoichiometric Uranium-Plutonium-Americium U0.750Pu0.246Am0.004O2-x Mixed Oxides.

    Science.gov (United States)

    Vauchy, Romain; Belin, Renaud C; Robisson, Anne-Charlotte; Lebreton, Florent; Aufore, Laurence; Scheinost, Andreas C; Martin, Philippe M

    2016-03-01

    Innovative americium-bearing uranium-plutonium mixed oxides U1-yPuyO2-x are envisioned as nuclear fuel for sodium-cooled fast neutron reactors (SFRs). The oxygen-to-metal (O/M) ratio, directly related to the oxidation state of cations, affects many of the fuel properties. Thus, a thorough knowledge of its variation with the sintering conditions is essential. The aim of this work is to follow the oxidation state of uranium, plutonium, and americium, and so the O/M ratio, in U0.750Pu0.246Am0.004O2-x samples sintered for 4 h at 2023 K in various Ar + 5% H2 + z vpm H2O (z = ∼15, ∼90, and ∼200) gas mixtures. The O/M ratios were determined by gravimetry, XAS, and XRD and evidenced a partial oxidation of the samples at room temperature. Finally, by comparing XANES and EXAFS results to that of a previous study, we demonstrate that the presence of uranium does not influence the interactions between americium and plutonium and that the differences in the O/M ratio between the investigated conditions is controlled by the reduction of plutonium. We also discuss the role of the homogeneity of cation distribution, as determined by EPMA, on the mechanisms involved in the reduction process. PMID:26907589

  4. Progress of p-channel bottom-gate poly-Si thin-film transistor by nickel silicide seed-induced lateral crystallization

    Science.gov (United States)

    Lee, Sol Kyu; Seok, Ki Hwan; Park, Jae Hyo; Kim, Hyung Yoon; Chae, Hee Jae; Jang, Gil Su; Lee, Yong Hee; Han, Ji Su; Joo, Seung Ki

    2016-06-01

    Excimer laser annealing (ELA) is known to be the most common crystallization technology for the fabrication of low-temperature polycrystalline-silicon (poly-Si) thin-film transistors (TFTs) in the mass production industry. This technology, however, cannot be applied to bottom-gate (BG) TFTs, which are well developed for the liquid-crystal display (LCD) back-planes, because strong laser energy of ELA can seriously damage the other layers. Here, we propose a novel high-performance BG poly-Si TFT using Ni silicide seed-induced lateral crystallization (SILC). The SILC technology renders it possible to ensure low damage in the layers, smooth surface, and longitudinal large grains in the channel. It was observed that the electrical properties exhibited a steep subthreshold slope of 110 mV/dec, high field-effect mobility of 304 cm2/Vsec, high I on/ I off ratio of 5.9 × 107, and a low threshold voltage of -3.9 V.

  5. Synthesis, Characterization, and Mechanism of Formation of Janus-Like Nanoparticles of Tantalum Silicide-Silicon (TaSi2/Si

    Directory of Open Access Journals (Sweden)

    Andrey V. Nomoev

    2014-12-01

    Full Text Available Metal-semiconductor Janus-like nanoparticles with the composition tantalum silicide-silicon (TaSi2/Si were synthesized for the first time by means of an evaporation method utilizing a high-power electron beam. The composition of the synthesized particles were characterized using high-resolution transmission electron microscopy (HRTEM, X-ray diffraction (XRD, selective area electron diffraction (SAED, and energy dispersive X-ray fluorescence (EDX analysis. The system is compared to previously synthesized core-shell type particles in order to show possible differences responsible for the Janus-like structure forming instead of a core-shell architecture. It is proposed that the production of Janus-like as opposed to core-shell or monophase particles occurs due to the ability of Ta and Si to form compounds and the relative content of Ta and Si atoms in the produced vapour. Based on the results, a potential mechanism of formation for the TaSi2/Si nanoparticles is discussed.

  6. Human bones obtained from routine joint replacement surgery as a tool for studies of plutonium, americium and {sup 90}Sr body-burden in general public

    Energy Technology Data Exchange (ETDEWEB)

    Mietelski, Jerzy W., E-mail: jerzy.mietelski@ifj.edu.pl [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Cracow (Poland); Golec, Edward B. [Traumatology and Orthopaedic Clinic, 5th Military Clinical Hospital and Polyclinic, Independent Public Healthcare Facility, Wroclawska 1-3, 30-901 Cracow (Poland); Orthopaedic Rehabilitation Department, Chair of Clinical Rehabilitation, Faculty of Motor of the Bronislaw Czech' s Academy of Physical Education, Cracow (Poland); Department of Physical Therapy Basics, Faculty of Physical Therapy, Administration College, Bielsko-Biala (Poland); Tomankiewicz, Ewa [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Cracow (Poland); Golec, Joanna [Orthopaedic Rehabilitation Department, Chair of Clinical Rehabilitation, Faculty of Motor of the Bronislaw Czech' s Academy of Physical Education, Cracow (Poland); Physical Therapy Department, Institute of Physical Therapy, Faculty of Heath Science, Jagiellonian University, Medical College, Cracow (Poland); Nowak, Sebastian [Traumatology and Orthopaedic Clinic, 5th Military Clinical Hospital and Polyclinic, Independent Public Healthcare Facility, Wroclawska 1-3, 30-901 Cracow (Poland); Orthopaedic Rehabilitation Department, Chair of Clinical Rehabilitation, Faculty of Motor of the Bronislaw Czech' s Academy of Physical Education, Cracow (Poland); Szczygiel, Elzbieta [Physical Therapy Department, Institute of Physical Therapy, Faculty of Heath Science, Jagiellonian University, Medical College, Cracow (Poland); Brudecki, Kamil [Henryk Niewodniczanski Institute of Nuclear Physics, Polish Academy of Sciences, Radzikowskiego 152, 31-342 Cracow (Poland)

    2011-06-15

    The paper presents a new sampling method for studying in-body radioactive contamination by bone-seeking radionuclides such as {sup 90}Sr, {sup 239+240}Pu, {sup 238}Pu, {sup 241}Am and selected gamma-emitters, in human bones. The presented results were obtained for samples retrieved from routine surgeries, namely knee or hip joints replacements with implants, performed on individuals from Southern Poland. This allowed to collect representative sets of general public samples. The applied analytical radiochemical procedure for bone matrix is described in details. Due to low concentrations of {sup 238}Pu the ratio of Pu isotopes which might be used for Pu source identification is obtained only as upper limits other then global fallout (for example Chernobyl) origin of Pu. Calculated concentrations of radioisotopes are comparable to the existing data from post-mortem studies on human bones retrieved from autopsy or exhumations. Human bones removed during knee or hip joint surgery provide a simple and ethical way for obtaining samples for plutonium, americium and {sup 90}Sr in-body contamination studies in general public. - Highlights: > Surgery for joint replacement as novel sampling method for studying in-body radioactive contamination. > Proposed way of sampling is not causing ethic doubts. > It is a convenient way of collecting human bone samples from global population. > The applied analytical radiochemical procedure for bone matrix is described in details. > The opposite patient age correlations trends were found for 90Sr (negative) and Pu, Am (positive).

  7. The recycling of the actinides neptunium, americium and curium in a fast power reactor to reduce the long term activity in a final store

    International Nuclear Information System (INIS)

    The starting point for the considerations and calculations given in this dissertation is the inevitable production of radioactive materials in the use of nuclear energy, which creates a considerable potential danger in a final store for a very long period. As one possibility of alleviating this problem, a concept for recycling the waste actinides neptunium, americium and curium was proposed. The waste actinides are separated in the reprocessing of burnt-up fuel elements and reach a further irradiation circuit. There they pass through the stages 'manufacture of irradiation elements', 'use in a fast power reactor' and reprocessing of irradiation elements' several times. In each irradiation and subsequent storage, about 17% of the waste actinides are removed by fission or by conversion into nuclides which can be reused as fuel, so that during the life of 40 years of the fast recycling reacor, the waste actinides can be reduced in mass by one half. In order to determine this mass reduction effect, a model calculation was developed, which includes the representation of the neutron physics and thermal properties of the reactor core and the storage and reprocessing of the irradiation elements. (orig./RB)

  8. Human bones obtained from routine joint replacement surgery as a tool for studies of plutonium, americium and 90Sr body-burden in general public

    International Nuclear Information System (INIS)

    The paper presents a new sampling method for studying in-body radioactive contamination by bone-seeking radionuclides such as 90Sr, 239+240Pu, 238Pu, 241Am and selected gamma-emitters, in human bones. The presented results were obtained for samples retrieved from routine surgeries, namely knee or hip joints replacements with implants, performed on individuals from Southern Poland. This allowed to collect representative sets of general public samples. The applied analytical radiochemical procedure for bone matrix is described in details. Due to low concentrations of 238Pu the ratio of Pu isotopes which might be used for Pu source identification is obtained only as upper limits other then global fallout (for example Chernobyl) origin of Pu. Calculated concentrations of radioisotopes are comparable to the existing data from post-mortem studies on human bones retrieved from autopsy or exhumations. Human bones removed during knee or hip joint surgery provide a simple and ethical way for obtaining samples for plutonium, americium and 90Sr in-body contamination studies in general public. - Highlights: → Surgery for joint replacement as novel sampling method for studying in-body radioactive contamination. → Proposed way of sampling is not causing ethic doubts. → It is a convenient way of collecting human bone samples from global population. → The applied analytical radiochemical procedure for bone matrix is described in details. → The opposite patient age correlations trends were found for 90Sr (negative) and Pu, Am (positive).

  9. The estimation of reactions of hematopoietic systems of organisms to the effect, caused by americium and plutonium, of nuclear industry workers

    Energy Technology Data Exchange (ETDEWEB)

    Gasteva, G. N.; Ivanova, T. A.; Gordeeva, A. A.; Suvorova, L. A.; Molokanov, A. A.; Badine, I.

    2004-07-01

    Object of research are the workers having in an organism radioactive substance (Am-241 and Pu-239). The purpose of work was the estimation of reaction hemopoietic systems of an organism on influence of americium and plutonium at workers of the nuclear industry. At the surveyed contingent of persons the determined effects caused by total influence Am-241 and Pu-239 are ascertained; chronic radiation disease with development, besides diffusive a pneumoscleoris and a chronic toxic-chemical radiating bronchitis, reactions of system of blood, jet hepatopathy which frequency accrued with increase doses loadings and essentially did not depend on age. In peripheral blood on the foreground jet changes act: hyperglobulia, the tendency to neutrophilus leukocytosis, monocytosis, increase ESR, decrease (reduction ?/G of factor reflecting weight and processing of defeat bronchus and pulmonary of system. Stable downstroke in number thrombocytes and reticulocytes in peripheral blood, their direct dependence on a doze of an irradiation, reflect hypoplastic a background hemogenesis, caused by long influence incorporatedin a bone and a bone brain of radioactive substances. At cytologic research punctate a bone brain jet changes which are expressed in increase of functional activity erythro-and myelopoiesiscome to light and provide compensatory reaction of peripheral blood. At histologic research of a bone brain and a bone fabric attributes of development atrophic process which is expressed in reduction of volume parenchyma a bone brain (a fatty atrophy) and dysplasia to a bone fabric are observed.

  10. Development of new ORIGEN2 data library sets for research reactors with light water cooled oxide and silicide LEU (20 w/o) fuels based on JENDL-3.3 nuclear data

    Energy Technology Data Exchange (ETDEWEB)

    Liem, Peng Hong, E-mail: liemph@nais.ne.jp [Nippon Advanced Information Service (NAIS Co., Inc.), 416 Muramatsu, Tokai-mura, Naka-gun, Ibaraki 319-1112 (Japan); Sembiring, Tagor Malem [Center for Reactor Technology and Nuclear Safety Indonesian National Nuclear Energy Agency (BATAN), Puspiptek Complex, Building No. 80, Serpong, Tangerang 15310 (Indonesia)

    2013-09-15

    Highlights: • We developed new ORIGEN2 data library sets for research reactors based on JENDL-3.3. • The sets cover oxide and silicide LEU fuels with meat density up to 4.74 g U/cm{sup 3}. • Two kinds of data library sets are available: fuel region and non-fuel regions. • We verified the new data library sets with other codes. • We validated the new data library against a non-destructive test. -- Abstract: New sets of ORIGEN2 data library dedicated to research/testing reactors with light water cooled oxide and silicide LEU fuel plates based on JENDL-3.3 nuclear data were developed, verified and validated. The new sets are considered to be an extension of the most recent release of ORIGEN2.2UPJ code, i.e. the ORLIBJ33 library sets. The newly generated ORIGEN2 data library sets cover both oxide and silicide LEU fuels with fuel meat density range from 2.96 to 4.74 g U/cm{sup 3} used in the present and future operation of the Indonesian 30 MWth RSG GAS research reactor. The new sets are expected applicable also for other research/testing reactors which utilize similar fuels or have similar neutron spectral indices. In addition to the traditional ORIGEN2 library sets for fuel depletion analyses in fuel regions, in the new data library sets, new ORIGEN2 library sets for irradiation/activation analyses were also prepared which cover all representative non-fuel regions of RSG GAS such as reflector elements, irradiation facilities, etc. whose neutron spectra are significantly softer than fuel regions. Verification with other codes as well as validation with a non-destructive test result showed promising results where a good agreement was confirmed.

  11. Phase-field study on the segregation mechanism of Cr to lamellar interface in C40-NbSi2/C11b-MoSi2 duplex silicide

    OpenAIRE

    Yamazaki, Toshihiro; Koizumi, Yuichiro; Chiba, Akihiko; Hagihara, Koji; Nakano, Takayoshi; Yuge, Koretaka; Kishida, Kyosuke; Inui, Haruyuki

    2013-01-01

    Cr-segregation to a lamellar interface in NbSi2/MoSi2 duplex silicide has been examined by a newly developed phase-field model. The model can take into account the segregation energy evaluated by a first principles calculation to reflect the chemical interaction between solute atoms and the interface in addition to the elastic interaction. Cr segregation occurs at the interface in the case with segregation energy whereas no segregation occurs in the case with only elastic interaction. However...

  12. M5Si3(M=Ti, Nb, Mo) Based Transition-Metal Silicides for High Temperature Applications

    Energy Technology Data Exchange (ETDEWEB)

    Tang, Zhihong [Iowa State Univ., Ames, IA (United States)

    2007-01-01

    Transition metal silicides are being considered for future engine turbine components at temperatures up to 1600 C. Although significant improvement in high temperature strength, room temperature fracture toughness has been realized in the past decade, further improvement in oxidation resistance is needed. Oxidation mechanism of Ti5Si3-based alloys was investigated. Oxidation behavior of Ti5Si3-based alloy strongly depends on the atmosphere. Presence of Nitrogen alters the oxidation behavior of Ti5Si3 by nucleation and growth of nitride subscale. Ti5Si3.2and Ti5Si3C0.5 alloys exhibited an excellent oxidation resistance in nitrogen bearing atmosphere due to limited dissolution of nitrogen and increased Si/Ti activity ratio. MoSi2 coating developed by pack cementation to protect Mo-based Mo-Si-B composites was found to be effective up to 1500 C. Shifting coating composition to T1+T2+Mo3Si region showed the possibility to extend the coating lifetime above 1500 C by more than ten times via formation of slow growing Mo3Si or T2 interlayer without sacrificing the oxidation resistance of the coating. The phase equilibria in the Nb-rich portion of Nb-B system has been evaluated experimentally using metallographic analysis and differential thermal analyzer (DTA). It was shown that Nbss (solid solution) and NbB are the only two primary phases in the 0-40 at.% B composition range, and the eutectic reaction L {leftrightarrow} NbSS + NbB was determined to occur at 2104 ± 5 C by DTA.

  13. The Dy–Ni–Si system as a representative of the rare earth–Ni–Si family: Its isothermal section and new rare-earth nickel silicides

    Energy Technology Data Exchange (ETDEWEB)

    Yuan, Fang; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada); Morozkin, A.V., E-mail: morozkin@general.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow GSP-2, 119992 (Russian Federation); Knotko, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, Moscow GSP-2, 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Pani, M.; Provino, A.; Manfrinetti, P. [Institute SPIN-CNR and Dipartimento di Chimica e Chimica Industriale, Università di Genova, Via Dodecaneso 31, 16146 Genova (Italy)

    2014-11-15

    }Si{sub 24}, ∼Dy{sub 16}Ni{sub 62}Si{sub 22}, DyNi{sub 7}Si{sub 6}, Dy{sub 3}Ni{sub 8}Si, DyNi{sub 2}Si, ∼Dy{sub 40}Ni{sub 47}Si{sub 13} and ∼Dy{sub 5}Ni{sub 2}Si{sub 3}. Quasi–binary solid solutions were detected for Dy{sub 2}Ni{sub 17}, DyNi{sub 5}, DyNi{sub 7}, DyNi{sub 3}, DyNi{sub 2}, DyNi, DySi{sub 2} and DySi{sub 1.67}. The crystal structures and magnetic properties of new phases RNi{sub 7}Si{sub 6} (GdNi{sub 7}Si{sub 6}-type), R{sub 3}Ni{sub 8}Si (Ce{sub 3}Co{sub 8}Si-type), RNi{sub 2}Si (YPd{sub 2}Si-type) and R{sub 3}Ni{sub 12}Si{sub 4} (Gd{sub 3}Ru{sub 4}Al{sub 12}-type), with R=Y, Gd–Tm, are also reported. - Highlights: • Dy–Ni–Si isothermal section was obtained at 870 K/1070 K. • Twelve known ternary dysprosium nickel silicides were confirmed in Dy–Ni–Si. • Nine new dysprosium nickel silicides were detected in Dy–Ni–Si. • Seventeen new rare earth nickel silicides were detected in (Y, Gd–Tm)–Ni–Si. • Tb{sub 3}Ni{sub 8}Si, Dy{sub 3}Ni{sub 8}Si, Ho{sub 3}Ni{sub 12}Si{sub 4} and DyNi{sub 2}Si show ferromagnetic-like ordering.

  14. The Dy–Ni–Si system as a representative of the rare earth–Ni–Si family: Its isothermal section and new rare-earth nickel silicides

    International Nuclear Information System (INIS)

    The Dy–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analysis. The system contains the 12 known compounds DyNi10Si2, DyNi5Si3, DyNi6Si6, DyNi4Si, DyNi2Si2, Dy2Ni3Si5, DyNiSi3, Dy3Ni6Si2, DyNiSi2, DyNiSi, Dy3NiSi3, Dy3NiSi2, and the new compounds Dy34Ni16−27Si50−39 (AlB2-type), Dy2Ni15.2−14.1Si1.8−2.9 (Th2Zn17-type), ∼Dy11Ni65Si24, ∼Dy16Ni62Si22 (unknown structures), DyNi7Si6 (GdNi7Si6-type), Dy3Ni8Si (Ce3Co8Si-type), DyNi2Si (YPd2Si-type), ∼Dy40Ni47Si13 and ∼Dy5Ni2Si3 (unknown structures). Quasi–binary solid solutions were detected at 1070 (870 K) for Dy2Ni17, DyNi5, DyNi7, DyNi3, DyNi2, DyNi, DySi2 and DySi1.67. No detectable solubility is observed for the other binary compounds of the Dy–Ni–Si system. The crystal structures of new phases RNi7Si6 (GdNi7Si6-type), R3Ni8Si (Ce3Co8Si-type), RNi2Si (YPd2Si-type) and R3Ni12Si4 (Gd3Ru4Al12-type), with R=Y, Gd–Tm, has been studied. Magnetic properties of few representative compounds are also reported. - Graphical abstract: The Dy–Ni–Si system has been investigated at 1070 K by X-ray and microprobe analysis. The system contains the 12 known compounds DyNi10Si2, DyNi5Si3, DyNi6Si6, DyNi4Si, DyNi2Si2, Dy2Ni3Si5, DyNiSi3, Dy3Ni6Si2, DyNiSi2, DyNiSi, Dy3NiSi3, Dy3NiSi2, and the new compounds Dy34Ni16−27Si50−39, Dy2Ni15.2−14.1Si1.8−2.9, ∼Dy11Ni65Si24, ∼Dy16Ni62Si22, DyNi7Si6, Dy3Ni8Si, DyNi2Si, ∼Dy40Ni47Si13 and ∼Dy5Ni2Si3. Quasi–binary solid solutions were detected for Dy2Ni17, DyNi5, DyNi7, DyNi3, DyNi2, DyNi, DySi2 and DySi1.67. The crystal structures and magnetic properties of new phases RNi7Si6 (GdNi7Si6-type), R3Ni8Si (Ce3Co8Si-type), RNi2Si (YPd2Si-type) and R3Ni12Si4 (Gd3Ru4Al12-type), with R=Y, Gd–Tm, are also reported. - Highlights: • Dy–Ni–Si isothermal section was obtained at 870 K/1070 K. • Twelve known ternary dysprosium nickel silicides were confirmed in Dy–Ni–Si. • Nine new dysprosium nickel silicides were detected in Dy

  15. The construction of TRIGA-TRAP and direct high-precision Penning trap mass measurements on rare-earth elements and americium

    Energy Technology Data Exchange (ETDEWEB)

    Ketelaer, Jens

    2010-06-14

    The construction of TRIGA-TRAP and direct high-precision Penning trap mass measurements on rare-earth elements and americium: Nuclear masses are an important quantity to study nuclear structure since they reflect the sum of all nucleonic interactions. Many experimental possibilities exist to precisely measure masses, out of which the Penning trap is the tool to reach the highest precision. Moreover, absolute mass measurements can be performed using carbon, the atomic-mass standard, as a reference. The new double-Penning trap mass spectrometer TRIGA-TRAP has been installed and commissioned within this thesis work, which is the very first experimental setup of this kind located at a nuclear reactor. New technical developments have been carried out such as a reliable non-resonant laser ablation ion source for the production of carbon cluster ions and are still continued, like a non-destructive ion detection technique for single-ion measurements. Neutron-rich fission products will be available by the reactor that are important for nuclear astrophysics, especially the r-process. Prior to the on-line coupling to the reactor, TRIGA-TRAP already performed off-line mass measurements on stable and long-lived isotopes and will continue this program. The main focus within this thesis was on certain rare-earth nuclides in the well-established region of deformation around N {proportional_to} 90. Another field of interest are mass measurements on actinoids to test mass models and to provide direct links to the mass standard. Within this thesis, the mass of {sup 241}Am could be measured directly for the first time. (orig.)

  16. 6,6 '-bis (5,5,8,8-tetramethyl-5,6,7,8-tetra-hydro-benzo 1,2,4 triazine-3-yl) 2,2 ' bipyridine, an effective extracting agent for the separation of americium(III) and curium(III) from the lanthanides

    International Nuclear Information System (INIS)

    The extraction of americium(III), curium(III), and the lanthanides(III) from nitric acid by 6,6'- bis (5,5,8,8-tetramethyl-5,6,7,8-tetra-hydro-benzo[1,2,4]triazine-3-yl)-[2,2'] bipyridine (CyMe4-BTBP) has been studied. Since the extraction kinetics were slow, N,N'-dimethyl-N,N'-di-octyl-2-(2-hexyl-oxy-ethyl)malonamide (DMDOHEMA) was added as a phase transfer reagent. With a mixture of 0.01 M CyMe4-BTBP + 0.25 M DMDOHEMA in n -octanol, extraction equilibrium was reached within 5 min of mixing. At a nitric acid concentration of 1 M, an americium(III) distribution ratio of approx. 10 was achieved. Americium(III)/lanthanide(III) separation factors between 50 (dysprosium) and 1500 (lanthanum) were obtained. Whereas americium(III) and curium(III) were extracted as di-solvates, the stoichiometries of the lanthanide(III) complexes were not identified unambiguously, owing to the presence of DMDOHEMA. In the absence of DMDOHEMA, both americium(III) and europium(III) were extracted as di-solvates. Back-extraction with 0.1 M nitric acid was thermodynamically possible but rather slow. Using a buffered glycolate solution of pH=4, an americium(III) distribution ratio of 0.01 was obtained within 5 min of mixing. There was no evidence of degradation of the extractant, for example, the extraction performance of CyMe4-BTBP during hydrolysis with 1 M nitric acid did not change over a two month contact. (authors)

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

    Science.gov (United States)

    Vauchy, Romain; Robisson, Anne-Charlotte; Martin, Philippe M.; Belin, Renaud C.; Aufore, Laurence; Scheinost, Andreas C.; Hodaj, Fiqiri

    2015-01-01

    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.

  18. Fabrication of targets for transmutation of americium : synthesis of inertial matrix by sol-gel method. Procedure study on the infiltration of a radioactive solutions

    International Nuclear Information System (INIS)

    addition a new and unexpected phase formed by the reaction of americium with spinel during the high temperature synthesis process has been identified. This new phase could provide a unique menas to stabilise Am in one particular oxidation state. (Author)

  19. Sorption and diffusion of cobalt, nickel, strontium, iodine, cesium and americium in natural fissure surfaces and drill core cups studied by autoradiography, 3

    International Nuclear Information System (INIS)

    This report summarizes the studies on sorption and diffusion of Cs, Sr, Co, Ni, Am and I in common rocks in Finnish bedrock carried out in laboratory experiments. Samples used in these studies were sections of drill cores containing filled and unfilled natural fracture surfaces and drill cores with a diamond drilled longitudinal cavity in the middle of the sample (drill core cups). Samples originated from the two nuclear power plant sites in Finland: tonalite and mica gneiss from Olkiluoto in Eurajoki and rapakivi granite from Haestholmen in Loviisa. The water used in the experiments was synthetic groundwater spiked at a time with one of the radionuclides: Cs-134, Sr-90, Co-60, Ni-63, Am-241 and I-125. Contact times from one week to one year were used to evaluate time dependence of diffusion. An autoradiographic method was used for determination of the penetration depths and diffusion pathways of elements. For determination of diffusion coefficients a quantitative computerized autoradiographic method was used to get the concentration profiles of the radionuclides in the drill cores. Sorption on natural fracture surfaces was more effective than on freshly drilled core samples. Filling materials on natural fracture surfaces, except calcite, increased sorption. The distribution coefficients for drill core cups were about the same as those for unfilled natural fracture surfaces after a contact time of one week and the sorption tendency of radionuclides was: Ka(Cs) > Ka(Co) > Ka(Am) > Ka(Ni) > Ka(Sr) > Ka(I). Radionuclides were observed to penetrate into fissures of the rock matrix and high-capacity minerals. Strontium was found as far as 35 mm in a filled natural fracture surface sample of rapakivi granite after a contact time of one year. The corresponding values were 3.0 mm for cesium, 2.1 mm for cobalt and 2.6 mm for nickel. For americium no diffusion could be observed (a-values for strontium was 6.6 x 10-16-1.1 x 10-13 m2/s, for cesium 4.7 x 10-16-7.2 x 10-15 m2/s

  20. Separation by sequential chromatography of americium, plutonium and neptunium elements: application to the study of trans-uranian elements migration in a European lacustrine system

    International Nuclear Information System (INIS)

    The nuclear tests carried out in the atmosphere in the Sixties, the accidents and in particular that to the power station of Chernobyl in 1986, were at the origin of the dispersion of a significant quantity of transuranic elements and fission products. The study of a lake system, such that of the Blelham Tarn in Great Britain, presented in this memory, can bring interesting answers to the problems of management of the environment. The determination of the radionuclides in sediment cores made it possible not only to establish the history of the depositions and consequently the origin of the radionuclides, but also to evaluate the various transfers which took place according to the parameters of the site and the properties of the elements. The studied transuranic elements are plutonium 238, 239-240, americium 241 and neptunium 237. Alpha emitting radionuclides, their determination requires complex radiochemical separations. A method was worked out to successively separate the three radioelements by using a same chromatographic column. Cesium 137 is the studied fission product, its determination is done by direct Gamma spectrometry. Lead 210, natural radionuclide, whose atmospheric flow can be supposed constant. makes it possible to obtain a chronology of the various events. The detailed vertical study of sediment cores showed that the accumulation mode of the studied elements is the same one and that the methods of dating converge. The cesium, more mobile than transuranic elements in the atmosphere, was detected in the 1963 and 1986 fallout whereas an activity out of transuranic elements appears only for the 1963 fallout. The activity of the 1963 cesium fallout is of the same order of magnitude as that of 1986. The calculation of the diffusion coefficients of the elements in the sediments shows an increased migration of cesium compared to transuranic elements. An inventory on the whole of the lake made it possible to note that the atmospheric fallout constitute the

  1. Construction of a four tip scanning tunneling microscope/scanning electron microscope combination and conductivity measurements of silicide nanowires; Aufbau einer Vierspitzen-Rastertunnelmikroskop/Rasterelektronenmikroskop-Kombination und Leitfaehigkeitsmessungen an Silizid Nanodraehten

    Energy Technology Data Exchange (ETDEWEB)

    Zubkov, Evgeniy

    2013-09-01

    In this work the combination of a four-tip scanning tunneling microscope with a scanning electron microscope is presented. By means of this apparatus it is possible to perform the conductivity measurements on the in-situ prepared nanostructures in ultra-high vacuum. With the aid of a scanning electron microscope (SEM), it becomes possible to position the tunneling tips of the four-tip scanning tunneling microscope (STM), so that an arrangement for a four-point probe measurement on nanostructures can be obtained. The STM head was built according to the novel coaxial Beetle concept. This concept allows on the one hand, a very compact arrangement of the components of the STM and on the other hand, the new-built STM head has a good mechanical stability, in order to achieve atomic resolution with all four STM units. The atomic resolution of the STM units was confirmed by scanning a Si(111)-7 x 7 surface. The thermal drift during the STM operation, as well as the resonant frequencies of the mechanical structure of the STM head, were determined. The scanning electron microscope allows the precise and safe navigation of the tunneling tips on the sample surface. Multi tip spectroscopy with up to four STM units can be performed synchronously. To demonstrate the capabilities of the new-built apparatus the conductivity measurements were carried out on metallic yttrium silicide nanowires. The nanowires were prepared by the in-situ deposition of yttrium on a heated Si(110) sample surface. Current-voltage curves were recorded on the nanowires and on the wetting layer in-between. The curves indicate an existence of the Schottky barrier between the yttrium silicide nanowires and the silicon bulk. By means of the two-tip measurements with a gate, the insulating property of the Schottky barrier has been confirmed. Using this Schottky barrier, it is possible to limit the current to the nanowire and to prevent it from flowing through the silicon bulk. A four-tip resistance measurement

  2. Americium behaviour in plastic vessels

    Energy Technology Data Exchange (ETDEWEB)

    Legarda, F.; Herranz, M. [Departamento de Ingenieria Nuclear y Mecanica de Fluidos, Escuela Tecnica Superior de Ingenieria de Bilbao, Universidad del Pais Vasco (UPV/EHU), Alameda de Urquijo s/n, 48013 Bilbao (Spain); Idoeta, R., E-mail: raquel.idoeta@ehu.e [Departamento de Ingenieria Nuclear y Mecanica de Fluidos, Escuela Tecnica Superior de Ingenieria de Bilbao, Universidad del Pais Vasco (UPV/EHU), Alameda de Urquijo s/n, 48013 Bilbao (Spain); Abelairas, A. [Departamento de Ingenieria Nuclear y Mecanica de Fluidos, Escuela Tecnica Superior de Ingenieria de Bilbao, Universidad del Pais Vasco (UPV/EHU), Alameda de Urquijo s/n, 48013 Bilbao (Spain)

    2010-07-15

    The adsorption of {sup 241}Am dissolved in water in different plastic storage vessels was determined. Three different plastics were investigated with natural and distilled waters and the retention of {sup 241}Am by these plastics was studied. The same was done by varying vessel agitation time, vessel agitation speed, surface/volume ratio of water in the vessels and water pH. Adsorptions were measured to be between 0% and 70%. The adsorption of {sup 241}Am is minimized with no water agitation, with PET or PVC plastics, and by water acidification.

  3. EURADOS action for determination of americium in skull measures in vivo and Monte Carlo simulation; Accion EURADOS para la determinacion de americio en craneo mediante medidas in-vivo y simulacion Monte Carlo

    Energy Technology Data Exchange (ETDEWEB)

    Lopez Ponte, M. A.; Navarro Amaro, J. F.; Perez Lopez, B.; Navarro Bravo, T.; Nogueira, P.; Vrba, T.

    2013-07-01

    From the Group of WG7 internal dosimetry of the EURADOS Organization (European Radiation Dosimetry group, e.V.) which It coordinates CIEMAT, international action for the vivo measurement of americium has been conducted in three mannequins type skull with detectors of Germanium by gamma spectrometry and simulation by Monte Carlo methods. Such action has been raised as two separate exercises, with the participation of institutions in Europe, America and Asia. Other actions similar precede this vivo intercomparison of measurement and modeling Monte Carlo1. The preliminary results and associated findings are presented in this work. The laboratory of the body radioactivity (CRC) of service counter of dosimetry staff internal (DPI) of the CIEMAT, it has been one of the participants in vivo measures exercise. On the other hand part, the Group of numerical dosimetry of CIEMAT is participant of the Monte Carlo2 simulation exercise. (Author)

  4. Critical and shielding parametric studies with the Monte Carlo code TRIPOLI to identify the key points to take into account during the transportation of blanket assemblies with high ratio of americium

    International Nuclear Information System (INIS)

    In the framework of French research program on Generation IV sodium cooled fast reactor, one possible option consists in burning minor actinides in this kind of Advanced Sodium Technological Reactor. Two types of transmutation mode are studied in the world : the homogeneous mode of transmutation where actinides are scattered with very low enrichment ratio in fissile assemblies and the heterogeneous mode where fissile core is surrounded by blanket assemblies filled with minor actinides with ratio of incorporated actinides up to 20%. Depending on which element is considered to be burnt and on its content, these minor actinides contents imply constraints on assemblies' transportation between Nuclear Power Plants and fuel cycle facilities. In this study, we present some academic studies in order to identify some key constraints linked to the residual power and neutron/gamma load of such kind of blanket assemblies. To simplify the approach, we considered a modeling of a 'model cask' dedicated to the transportation of a unique irradiated blanket assembly loaded with 20% of Americium and basically inspired from an existent cask designed initially for the damaged fissile Superphenix assembly transport. Thermal calculations performed with EDF-SYRTHES code have shown that due to thermal limitations on cladding temperature, the decay time to be considered before transportation is 20 years. This study is based on explicit 3D representations of the cask and the contained blanket assembly with the Monte Carlo code TRIPOLI/JEFF3.1.1 library and concludes that after such a decay time, the transportation of a unique Americium radial blanket is feasible only if the design of our model cask is modified in order to comply with the dose limitation criterion. (author)

  5. Corrosion behaviors of a γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy in NaCl solution

    International Nuclear Information System (INIS)

    Corrosion behaviors of a novel corrosion-resistant γ-toughened Cr13Ni5Si2/Cr3Ni5Si2 multi-phase ternary metal silicide alloy and properties of the passive film formed in NaCl solution were examined by anodic polarization, cyclic polarization and electrochemical impedance spectroscopy (EIS) experiments as well as X-ray photoelectron spectroscopy (XPS) and potentiostatic polarization measurements. Effects of immersion time and chloride ion concentration on corrosion behaviors of the alloy were also evaluated. Results indicated that the alloy exhibited excellent corrosion resistance in NaCl solution due to the spontaneous formation of a compact and protective passive film composed mainly of chromium (III) oxide as well as the high chemical stability and strong inter-atomic bonds inherent to Cr13Ni5Si2 and Cr3Ni5Si2 intermetallic phases. Moreover, corrosion resistance of the alloy was quite insensitive to the increase of chloride ion concentration and was improved noticeably with the increasing immersion time

  6. Use of radioactive methods for determination of uranium, neptunium, plutonium, americium and curium isotopes in waste radioactive; Utilizacao de metodos radioanaliticos para determinacao de isotopos de uranio, netunio, plutonio, americio e curio em rejeitos radioativos

    Energy Technology Data Exchange (ETDEWEB)

    Geraldo, Bianca

    2012-07-01

    Activated charcoal is a common type of radioactive waste that contains high concentrations of fission and activation products. The management of this waste includes its characterization aiming the determination and quantification of the specific radionuclides including those known as Difficult-to-Measure Radionuclides (RDM). The analysis of the RDM's generally involves complex radiochemical analysis for purification and separation of the radionuclides, which are expensive and time-consuming. The objective of this work was to define a methodology for sequential analysis of the isotopes of uranium, neptunium, plutonium, americium and curium present in a type of radioactive waste, evaluating chemical yield, analysis of time spent, amount of secondary waste generated and cost. Three methodologies were compared and validated that employ ion exchange (TI+EC), extraction chromatography (EC) and extraction with polymers (ECP). The waste chosen was the activated charcoal from the purification system of primary circuit water cooling the reactor IEA-R1. The charcoal samples were dissolved by acid digestion followed by purification and separation of isotopes with ion exchange resins, extraction and chromatographic extraction polymers. Isotopes were analyzed on an alpha spectrometer, equipped with surface barrier detectors. The chemical yields were satisfactory for the methods TI+EC and EC. ECP method was comparable with those methods only for uranium. Statistical analysis as well the analysis of time spent, amount of secondary waste generated and cost revealed that EC method is the most effective for identifying and quantifying U, Np, Pu, Am and Cm present in charcoal. (author)

  7. Preparation of Silicide Layer Deposited on AISI 304 Surface and Its Cyclic Oxidation Behavior at 900 ℃%AISI304表面硅化物渗层的制备及其900℃循环氧化性能研究

    Institute of Scientific and Technical Information of China (English)

    安亮; 马勤; 贾建刚; 李鹏

    2011-01-01

    AISI304 stainless steel was formed in molten salts at 800 ℃ for 5 h using molten mixture of Na2SiF6: Si=8:2 as silionizing agent and the molten halogenide of alkali metals of NaCl: KC1: NaF=2:2:1 as siliconizing agent carrier by adding SiO2 as another source. The cyclic oxidation behavior of the layer at 900 °C was studied as well. The phase of the silicide layer and the oxide film was analyzed by X-ray diffraction. Meanwhile, the micrographs and the composition of the cross section of the silicide layer and the oxide film were studied by SEM and EDS. The results show that the phases of the silicide layer mainly consist of Fe3Si. The amount of Cr containing in silicide layer is lower than in AISI 304 matrix, while the amount of Fe and Ni containing in the layer is about equal to those in the matrix. The oxidation kinetic curve of the Fe3Si type silicide layer obeys a parabolic rule. The oxide film close to the interface of the oxide film/silicide layer contains with SiO2 and Cr2O3 resulting from the uphill diffusion of Cr and Si and the outer oxide film contains with Fe2O3. The composite oxide film accounts for the excellent high temperature oxidation properties.%采用NaCl:KCl:NaF=2:2∶1(摩尔比)的中性熔融盐作为载体,Na2SiF6∶ Si=8:2粉末做为渗硅剂,以SiO2为助渗剂,800℃下渗硅5h可实现在AISI 304不锈钢表面形成厚约600 μm的富含Cr、Ni合金元素的Fe3Si型硅化物渗层,研究了渗层在900℃下的循环氧化行为.采用X射线衍射仪分析了渗层和氧化膜的物相组成,用附带能量色散谱仪附件的扫描电子显微镜研究了渗层和氧化膜截面的形貌和成分.结果表明,渗层为以Fe3Si相为主,Cr在渗层中含量低于其在304不锈钢基体中含量,而Fe和Ni在基体和渗层中的含量大致相当.氧化动力学遵从二次抛物线规律;Cr和Si元素发生上坡扩散形成以SiO2和Cr2O3为主的内层氧化膜,外层氧化膜以Fe2O3为主,这种复合氧化膜是渗层

  8. Solubility and speciation studies of waste radionuclides pertinent to geologic disposal at Yucca Mountain: Results on neptunium, plutonium and americium in J-13 groundwater; Letter report (R707): Reporting period, October 1, 1985--September 30, 1987

    Energy Technology Data Exchange (ETDEWEB)

    Nitsche, H.; Standifer, E.M.; Lee, S.C.; Gatti, R.C.; Tucker, D.B.

    1988-01-01

    We have studied the solubilities of neptunium, plutonium, and americium in J-13 groundwater from Yucca Mountain (Nevada) at three temperatures and hydrogen ion concentrations. They are 25{degree}, 60{degree}C, and 90{degree}C and pH 5.9, 7.0, and 8.5. The results for 25{degree}C are from a study which we did during FY 1984. We included these previous results in the tables to give more information on the solubility temperature dependence; they were, however, done at only one pH (7.0). The solubilities were studied from oversaturation. The nuclides were added at the beginning of each experiment as NpO{sub 2}{sup +}, Pu{sup 4+}, and Am{sup 3+}. The neptunium solubility decreased with increasing temperature and with increasing pH. The soluble neptunium did not change oxidation state at steady state. The pentavalent neptunium was increasingly complexed by carbonate with increasing pH. All solids were crystalline and contained carbonate, except the solid formed at 90{degree}C and pH 5.9. We identified this solid as crystalline Np{sub 2}P{sub 5}. The 25{degree}C, pH 7 solid was Na{sub 3}NpO{sub 2}(CO{sub 3}){sub 2} {center_dot} nH{sub 2}O. Plutonium concentrations decreased with increasing temperature and showed no trend with pH. Pu(V) and Pu(VI) were the dominant oxidation states in the supernatant solution; as the amount of Pu(V) increased with pH, Pu(VI) decreed. The steady-state solids were mostly amorphous, although some contained a crystalline component. They contained Pu(IV) polymer and unknown carbonates.

  9. AISI304不锈钢表面Fe3Si型硅化物渗层的制备及渗硅机理%Preparation and siliconizing mechanism of Fe3Si type silicide layer deposited on AISI 304 stainless steel

    Institute of Scientific and Technical Information of China (English)

    安亮; 贾建刚; 马勤; 李鹏

    2011-01-01

    The silicide layers deposited on the AISI 304 stainless steel were formed in the molten salts at 800 "C using the molten mixture of different mole ratios of Na2SiF6 to Si using the siliconizing agent and the molten halogenide of alkali metals of NaCl+KCl+NaF at mole ratio of 2:2:1 as the siliconizing agent carrier. In order to reveal the siliconizing mechanism in the molten salts, the phase of the silicide layer was analyzed by X-ray diffractometry. Meanwhile, the micrographs and the composition of the cross section of the silicide layer were studied by scanning electron microscopy (SEM) attached with energy dispersive X-ray spectrometer (EDS). The results show that the silicon content in the layer depends on the ion concentration of SiF62~ in the molten salts. The dissolving of SiO2 in the molten salts supplies the SiF62~ continuously and as a result, the silicon content in the layer is enhanced.%以n(NaCl)∶n(KCl)∶n(NaF)=2∶2∶1碱金属卤化物混合体系做载体,采用不同摩尔比的Na2SiF6和Si粉作渗硅剂,在800℃下利用熔融盐法分别对AISI 304不锈钢进行渗硅处理.采用X射线衍射仪(XRD)分析渗硅层的物相组成,用附带能量色散谱仪(EDS)附件的扫描电子显微镜(SEM)研究渗层截面的形貌和成分,分析熔盐法渗硅层的形成机理.结果表明:融盐中SiF62-的浓度决定渗层中Si元素的含量,由于SiO2在融盐体系中的溶解,融盐中SiF62-得到补充,渗层中Si元素的含最进一步提高.

  10. The proliferation potential of neptunium and americium

    Energy Technology Data Exchange (ETDEWEB)

    An, J. S.; Shin, J. S.; Kim, J. S.; Kwack, E. H.; Kim, B. K

    2000-05-01

    It is recognized that some trans-uranic elements other than plutonium, in particular Np and Am, if will be available in sufficient quantities, could be used for nuclear explosive devices. The spent fuel has been accumulating in number of nuclear power plant and operation of large scale commercial reprocessing plants. However, these materials are not covered by the definition of special fissionable material in the Agency Statute. At the time when the Statute was adopted, the availability of meaningful quantities of separated Np and Am was remote and they were not included in the definition of special fissionable material. Then, IAEA Board decided a measure for control of Np and Am on September 1999. This report contains the control method and the characteristic of Np and Am for using domestic nuclear industries, and it can be useful for understanding how to report and account of Np and Am. (author)

  11. Delocalization and new phase in Americium: theory

    Energy Technology Data Exchange (ETDEWEB)

    Soderlind, P

    1999-04-23

    Density-functional electronic structure calculations have been used to investigate the high pressure behavior of Am. At about 80 kbar (8 GPa) calculations reveal a monoclinic phase similar to the ground state structure of plutonium ({alpha}-Pu). The experimentally suggested {alpha}-U structure is found to be substantially higher in energy. The phase transition from fcc to the low symmetry structure is shown to originate from a drastic change in the nature of the electronic structure induced by the elevated pressure. A calculated volume collapse of about 25% is associated with the transition. For the low density phase, an orbital polarization correction to the local spin density (LSD) theory was applied. Gradient terms of the electron density were included in the calculation of the exchange/correlation energy and potential, according to the generalized gradient approximation (GGA). The results are consistent with a Mott transition; the 5f electrons are delocalized and bonding on the high density side of the transition and chemically inert and non-bonding (localized) on the other. Theory compares rather well with recent experimental data which implies that electron correlation effects are reasonably modeled in our orbital polarization scheme.

  12. Evaluation of neutron data for americium-241

    Energy Technology Data Exchange (ETDEWEB)

    Maslov, V.M.; Sukhovitskij, E.Sh.; Porodzinskij, Yu.V.; Klepatskij, A.B.; Morogovskij, G.B. [Radiation Physics and Chemistry Problems Inst., Minsk-Sosny (Belarus)

    1997-03-01

    The evaluation of neutron data for {sup 241}Am is made in the energy region from 10{sup -5} eV up to 20 MeV. The results of the evaluation are compiled in the ENDF/B-VI format. This work is performed under the Project Agreement CIS-03-95 with the International Science and Technology Center (Moscow). The Financing Party for the Project is Japan. The evaluation was requested by Y. Kikuchi (JAERI). (author). 60 refs.

  13. Dual fuel gradients in uranium silicide plates

    Energy Technology Data Exchange (ETDEWEB)

    Pace, B.W. [Babock and Wilcox, Lynchburg, VA (United States)

    1997-08-01

    Babcock & Wilcox has been able to achieve dual gradient plates with good repeatability in small lots of U{sub 3}Si{sub 2} plates. Improvements in homogeneity and other processing parameters and techniques have allowed the development of contoured fuel within the cladding. The most difficult obstacles to overcome have been the ability to evaluate the bidirectional fuel loadings in comparison to the perfect loading model and the different methods of instilling the gradients in the early compact stage. The overriding conclusion is that to control the contour of the fuel, a known relationship between the compact, the frames and final core gradient must exist. Therefore, further development in the creation and control of dual gradients in fuel plates will involve arriving at a plausible gradient requirement and building the correct model between the compact configuration and the final contoured loading requirements.

  14. Silicide characterization at alumina-niobium interfaces

    OpenAIRE

    McKeown, JT; Radmilovic, Velimir R; Gronsky, R.; Glaeser, AM

    2011-01-01

    Alumina–niobium interfaces formed by liquidfilm-assisted joining with copper/niobium/copper interlayers exhibited microstructures that depend on the nature of the alumina components. Characterization of these interfaces in the transmission electron microscope provided insight on the relationship between interfacial microstructure and fracture performance. Interfaces between sapphire and niobium and those between high-purity (99.9%) polycrystalline alumina and niobium were free of secondary ph...

  15. AISI304不锈钢表面Fe3Si型硅化物渗层制备及其力学性能%Preparation of Fe3Si Type Transition-metal Silicide Layer Deposited on AISI 304 Stainless and Its Mechanical Property

    Institute of Scientific and Technical Information of China (English)

    安亮; 马勤; 贾建刚; 李鹏

    2011-01-01

    采用NaCl∶ KCl∶NaF=2∶2∶1(摩尔比)的中性熔融盐作为载体,Na2SiF6∶ Si=8∶2粉末作为渗硅剂,以SiO2为助渗剂,800℃下渗硅5h可实现在AISI 304不锈钢表面形成厚约600 μm的富含Cr,Ni合金元素的Fe3Si型硅化物渗层.采用万能材料试验机进行了轴向拉伸试验,并对应力-应变曲线进行了分析.结果表明,硅化物渗层为脆性断裂,基体部分为塑性断裂;AISI 304不锈钢渗硅后的名义屈服应力有明显提高.%Fe3Si type silicide layer containing Cr and Ni alloying elements with a thickness of about 600 u,m deposited on AISI 304 stainless steel was formed in molten salts at 800 'C for 5 h using molten mixture of Na2SiF,j: Si=8 :2 as siliconizing agent and the molten halogenide of alkali metals of NaCl: KC1: NaF=2:2 :1 as siliconizing agent carrier by adding SiO2 as another source. The tension behavior of the samples was tested on an universal tension apparatus, the stress-strain curves were analysed as well. The results show that the brittle fracture occurs in the layer and the ductile fracture occurs in the matrix; nominal yield stress of the siliconized sample is significantly improved.

  16. Study of the electrochemical oxidation of Am with lacunary heteropolyanions and silver nitrate; Etude de l'oxydation electrochimique de l'americium en presence d'heteropolyanions lacunaires et de nitrate d'argent en milieu aqueux acide

    Energy Technology Data Exchange (ETDEWEB)

    Chartier, D

    1999-07-01

    Electrochemical oxidation of Am(III) with certain lacunary heteropolyanions (LHPA {alpha}{sub 2}-P{sub 2}W{sub 17}O{sub 61}{sup 10-} or {alpha}SiW{sub 11}O{sub 39}{sup 8-}) and silver nitrate is an efficient way to prepare Am(VI). This document presents bibliographic data and an experimental study of the process. Thus, it has been established that Am(IV) is an intermediate species in the reaction and occurs in 1:1 (Amt{sup IV}LHPA) or 1:2 (Am {sup IV}(LHAP){sub 2}) complexes with the relevant LHPA. These 1:1 complexes of Am(IV) have been identified and isolated in this work whereas 1:2 complexes were known from previous studies. The reactivity of these complexes in oxidation shows that 1:1 complexes of Am(IV) are oxidised much more quickly than 1:2 complexes. Apparent stability constants of Am(III) and Am(IV) complexes with the relevant LHPA have been measured for a 1 M nitric acid medium. Thermodynamic data of the reaction are then assessed: redox potentials of Am pairs are computed for a 1 M nitric acid medium containing various amount of LHPA ligands. Those results show that the role of LHPA is to stabilize the intermediate species Am(IV) by lowering the Am(IV)/Am(III) pair potential of about 1 Volt. Nevertheless, if this stabilisation is too strong (i.e. of tungsto-silicate), the oxidation of Am(IV) requires high anodic potential (more than 2 V/ENH). Then, the faradic yield of the oxidation of americium is poor because of water oxidation. This study has also shown that the main role of silver is to catalyze the electrochemical oxidation of Am{sup IV}(LHPA){sub X} complexes. Indeed, these oxidations without silver are extremely slow. An oxygen tracer experiment has been performed during the oxidation of Am(III) in Am(VI). It has been shown that the oxygen atoms of Am(VI) (AMO{sub 2}{sup 2+}) come from water molecules of the solvent and not from the complexing oxygen atoms of the ligands. (author)

  17. Fabrication of targets for transmutation of americium : synthesis of inertial matrix by sol-gel method. Procedure study on the infiltration of a radioactive solutions; Fabricacion de blancos para la transmutacion de americio: sintesis de matrices inertes por el metodo sol-gel. Estudio del procedimiento de infiltracion de disoluciones radiactivas

    Energy Technology Data Exchange (ETDEWEB)

    Fernandez Carretero, A. [Universidad Complutense de Madrid (Spain)

    2002-07-01

    made. In addition a new and unexpected phase formed by the reaction of americium with spinel during the high temperature synthesis process has been identified. This new phase could provide a unique menas to stabilise Am in one particular oxidation state. (Author)

  18. Preparation of americium targets for nuclear chemistry experiments at DANCE

    International Nuclear Information System (INIS)

    Using 1 gram of 241Am from LANL stocks, the purification steps required to obtain a solution of 241Am from the original material are described. Part of the purified solution was submitted for purity analysis by mass spectrometry, radiochemistry and trace metals analysis. The impurities were expected to be 239Pu and 237Np. A second fraction of this material was used for electroplating three samples onto titanium disks that were suitable for insertion into an instrument package to be placed into the DANCE detector. The purification methods used, the electroplating setup and the solutions to various problems that were encountered in making these targets are discussed. The analytical results are discussed as well as the yields from the electrodeposition process. Comparison of these yields with those from similar experiments utilizing 235U and 243Am are also discussed. (author)

  19. Americium separation from nuclear fuel dissolution using higher oxidation states.

    Energy Technology Data Exchange (ETDEWEB)

    Bruce J. Mincher

    2009-09-01

    Much of the complexity in current AFCI proposals is driven by the need to separate the minor actinides from the lanthanides. Partitioning and recycling Am, but not Cm, would allow for significant simplification because Am has redox chemistry that may be exploited while Cm does not. Here, we have explored methods based on higher oxidation states of Am (AmV and AmVI) to partition Am from the lanthanides. In a separate but related approach we have also initiated an investigation of the utility of TRUEX Am extraction from thiocyanate solution. The stripping of loaded TRUEX by Am oxidation or SCN- has not yet proved successful; however, the partitioning of inextractable AmV by TRUEX shows promise.

  20. Recovery of neptunium, plutonium, and americium from highly active waste

    International Nuclear Information System (INIS)

    Trialkylphosphine oxides (TRPO) (alkyl is 6c-C8) were chosen as the extractant for the recovery of Np, Pu, and Am from highly active waste (HAW) because of its extraction ability, excellent solvent behavior, high radiolytic stability, and low cost. Process chemistry based on 30 vol % TRPO-kerosene as solvent is presented. Extraction of Am in the presence of macro amounts of neodymium, adjustment of Np valence by electrolytic reduction, selective stripping of actinides from loaded organic phase, and loading capacity of the solvent are included. Process parameters of multistage countercurrent extraction and stripping and the results of experimental verification are given. From HAW with ∼1 M nitric acid concentration, recovery of actinides is higher than 99.9%. The actinides extracted can be stripped out separately into Am, Np-Pu, and U fractions. The behavior of nonactinide HAW constituents, including Tc, is discussed

  1. Property Data for Simulated Americium/Curium Glasses

    International Nuclear Information System (INIS)

    The authors studied the properties of mixed lanthanide-alumino-borosilicate glasses. Fifty-five glasses were designed to augment a previous, Phase I, study by systematically varying the composition of Ln2O3 and the concentrations of Ln2O3, SiO2, B2O3, Al2O3, and SrO in glass. These glasses were designed and fabricated at the Savannah River Technology Center and tested at the Pacific Northwest National Laboratory. The properties measured include the high-temperature viscosity (η) as a function of temperature (T) and the liquidus temperature (TL) of Phase II test glasses

  2. The vapour pressure of americium(III) chloride

    International Nuclear Information System (INIS)

    Based on the method described by Fischer, an ultramicro-size appratus was developed for static determination of the saturation vapour pressure of highly radioactive materials. The apparatus was tested with MgCl2, MnCl2, HoCl3 and ScF3. The vapour pressure curves of MgCl2 and MnCl2 were in good agreement with other publications and thus proved the efficiency of the apparatus in spite of its difficulties of handling. The values measured for HoCl3 and ScF3 differed from those of earlier publications. However, these deviations have been observed before and may be the result of the different measuring principles of static and dynamic methods. For AmCl3, the following vapour pressure equation was established: log psub(Torr)=-(11826/T)+10.7. The thermodynamic parameters of the evaporation process were calculated on this basis, and the values for AmBr3 and PnCl3 were determined by extrapolation. (orig.)

  3. 1976 Hanford americium-exposure incident: accident description

    International Nuclear Information System (INIS)

    An accident is described, involving the explosion of an ion-exchange column containing about 100 g of 241Am. A chemical operator was injured in this accident, receiving acid burns and superficial cuts on the upper part of his body. From 1 to 5 curies of 241Am is estimated to have been deposited on the injured worker and on his clothing

  4. Further Studies of Plutonium and Americium at Thule, Greenland

    DEFF Research Database (Denmark)

    Aarkrog, Asker; Dahlgaard, Henning; Nilsson, Karen Kristina;

    1984-01-01

    Eleven years after the accidental loss of nuclear weapons in 1968, the fourth scientific expedition to Thule occurred. The estimated inventory of 1 TBq 239,240Pu in the marine sediments was unchanged when compared with the estimate based on the 1974 data. Plutonium from the accident had moved...

  5. Milestone report on MD potential development for uranium silicide

    Energy Technology Data Exchange (ETDEWEB)

    Yu, Jianguo [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Zhang, Yongfeng [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.; Hales, Jason Dean [Idaho National Lab. (INL), Idaho Falls, ID (United States). Fuel Modeling and Simulation Dept.

    2016-03-01

    This report summarizes the progress on the interatomic potential development of triuranium-disilicide (U3Si2) for molecular dynamics (MD) simulations. The development is based on the Tersoff type potentials for single element U and Si. The Si potential is taken from the literature and a Tersoff type U potential is developed in this project. With the primary focus on the U3Si2 phase, some other U-Si systems such as U3Si are also included as a test of the transferability of the potentials for binary U-Si phases. Based on the potentials for unary U and Si, two sets of parameters for the binary U-Si system are developed using the Tersoff mixing rules and the cross-term fitting, respectively. The cross-term potential is found to give better results on the enthalpy of formation, lattice constants and elastic constants than those produced by the Tersoff mixing potential, with the reference data taken from either experiments or density functional theory (DFT) calculations. In particular, the results on the formation enthalpy and lattice constants for the U3Si2 phase and lattice constants for the high temperature U3Si (h-U3Si) phase generated by the cross-term potential agree well with experimental data. Reasonable agreements are also reached on the elastic constants of U3Si2, on the formation enthalpy for the low temperature U3Si (m-U3Si) and h-U3Si phases, and on the lattice constants of m-U3Si phase. All these phases are predicted to be mechanically stable. The unary U potential is tested for three metallic U phases (α, β, γ). The potential is found capable to predict the cohesive energies well against experimental data for all three phases. It matches reasonably with previous experiments on the lattice constants and elastic constants of αU.

  6. Scanning MOKE investigation of ion-beam-synthesized silicide films

    Energy Technology Data Exchange (ETDEWEB)

    Gumarov, G.G., E-mail: ifoggg@gmail.com [Zavoisky Physical-Technical Institute of THE RAS, 10/7 Sibirsky Trakt, Kazan 420029, Tatarstan (Russian Federation); Kazan Federal University, 18 Kremlyovskaya St., Kazan 420008, Tatarstan (Russian Federation); Konovalov, D.A.; Alekseev, A.V. [Zavoisky Physical-Technical Institute of THE RAS, 10/7 Sibirsky Trakt, Kazan 420029, Tatarstan (Russian Federation); Petukhov, V.Yu. [Zavoisky Physical-Technical Institute of THE RAS, 10/7 Sibirsky Trakt, Kazan 420029, Tatarstan (Russian Federation); Kazan Federal University, 18 Kremlyovskaya St., Kazan 420008, Tatarstan (Russian Federation); Zhikharev, V.A. [Kazan State Technology University, 68 Karl Marx St., Kazan 420015, Tatarstan (Russian Federation); Nuzhdin, V.I.; Shustov, V.A. [Zavoisky Physical-Technical Institute of THE RAS, 10/7 Sibirsky Trakt, Kazan 420029, Tatarstan (Russian Federation)

    2012-07-01

    Fe ions with an energy of 40 keV were implanted into Si plates with the fluence varying in the range of (1.6-3.0) Multiplication-Sign 10{sup 17} ion/cm{sup 2} in the external magnetic field. Scanning magnetooptical Kerr effect (MOKE) studies have shown that all samples possess uniaxial anisotropy. Both the coercive field and the anisotropy field increase with fluence. It was suggested that induced anisotropy is caused by inverse magnetostriction.

  7. Repairing Chipped Silicide Coatings on Refractory Metal Substrates

    Science.gov (United States)

    Youngquist, Robert

    2006-01-01

    The space shuttle orbiter s reaction control system (RCS) is a series of small thrusters that use hypergolic fuels to orient the orbiter in space. The RCS thrusters are constructed from a special niobium-based alloy -- the C-103. This alloy retains excellent mechanical properties from cryogenic temperature all the way up to 2,500 F (1,370 C). C-103 is susceptible to rapid oxidation at elevated temperatures. The authors have developed two methods to repair damaged R512a coatings on C-103. For the first repair technique, metal foundries, semiconductor manufacturers, and many other industries have developed and routinely use coatings that can easily be painted on metal to protect it from corrosion, including oxidation, to temperatures in excess of 2,500 F (1,370 C). This first repair technique is considered somewhat temporary. The second repair technique is based on using the native coating material of the RCS nozzles. the chipped area is ground out and a "green" R512a coating is applied to the repair area. Both repair techniques can be applied for moderate protection until the permanent laser-repair technique is available to the repair area.

  8. Electrochemical behaviour of metal silicides in acidic and alkaline media

    Institute of Scientific and Technical Information of China (English)

    Shein; A.; B.; Rakityanskaya; I.; L.; Ivanova; O.; S.

    2005-01-01

    The elaboration of new materials with high corrosion resistance is one of the actual problems of modern corrosion science. One of the most interesting objects is intermetallic compounds and metallides. These materials are widely used as the basis for new resistive alloys.……

  9. Electrochemical behaviour of metal silicides in acidic and alkaline media

    Institute of Scientific and Technical Information of China (English)

    2005-01-01

    @@ The elaboration of new materials with high corrosion resistance is one of the actual problems of modern corrosion science. One of the most interesting objects is intermetallic compounds and metallides. These materials are widely used as the basis for new resistive alloys.

  10. Electron transport and barrier inhomogeneities in palladium silicide Schottky diodes

    Science.gov (United States)

    Chand, S.; Kumar, J.

    The current-voltage (I-V) characteristics of Schottky diodes, prepared by deposition of palladium film on to a n/n+ silicon wafer held at 573 K, are measured over a temperature range 37-307 K and analyzed in terms of thermionic emission-diffusion (TED) theory by incorporating the concept of barrier inhomogeneities through a Gaussian distribution function. The process adopted is shown to yield an ideal Schottky diode with a near constant barrier height of 0.734 V and ideality factor 1.05 in the temperature interval 215-307 K. Below 215 K, both the barrier height (φbo) and the ideality factor (η) exhibit abnormal temperature dependence and are explained by invoking two sets of Gaussian distributions of barrier heights at 84-215 K and 37-84 K. Further, it is demonstrated that the forward bias makes the Gaussian distribution dynamic so that the mean fluctuates (i.e., increases or decreases depending on whether its voltage coefficient is positive or negative) and the standard deviation decreases progressively, i.e., the barrier homogenizes temporarily. The changes occur in such a way that the apparent barrier height at any bias is always higher than at zero-bias. Finally, it is pointed out that the presence of single/multiple distributions can be ascertained and the values of respective parameters deduced from the φap vs. 1/T plot itself. Also, the inverse ideality factor versus inverse temperature plot provides bias coefficients of the mean barrier height and standard deviation of the distribution function.

  11. Study of Irradiation Effect onto Uranium silicide Fuel

    International Nuclear Information System (INIS)

    The irradiation effect onto the U3Si-Al and U3Si2-Al dispersion type of fuel element has been studied. The fuel material performs swelling during irradiation due to boehmite (Al2O3(H2O)) formation in which might occurs inside the meat and on the cladding surface, the interaction between the fuel and aluminium matrix that produce U(Al,Si)3 phase, and the formation of fission gas bubble inside the fuel. At a constant fission density, the U3Si-Al fuel swelling is higher than that of U3Si2-Al fuel. The swellings of both fuels increase with the increasing of fission density. The difference of swelling behavior was caused by formation of large bubble gases generated from fission product of U3Si fuel and distributed non-uniformly over all of fuel zone. On the other hand, the U3Si2 fission produced small bubble gases, and those were uniformly distributed. The growth rate of fission gas bubble in the U3Si fuel has shown high diffusivity, transformation into amorph material and thus decrease its mechanical strength

  12. Investigation of the retention and distribution of americium-241 in the baboon and the enhanced removal of americium-241 from the body by diethylenetriaminepentaacetic acid (DTPA)

    International Nuclear Information System (INIS)

    Experiments were performed to study the metabolism and distribution of intravenously administered 241Am in the adult and juvenile baboon; in addition, decorporation therapy using Na3-CaDTPA was performed on selected baboons to assess the efficacy of this drug in removing systemic burdens of 241Am from this primate species. Determination of the kinetics of 241Am was accomplished principally by in vivo methodologies and by radiochemical analysis of 241Am activity of biological material. The use of Na3-CaDTPA as a therapeutic agent for the removal of 241Am from the body proved to be an effective form of treatment in the case of early administration. (U.S.)

  13. Americium-Curium Stabilization - 5'' Cylindrical Induction Melter System Design Basis

    Energy Technology Data Exchange (ETDEWEB)

    Witt, D.C.

    1999-11-08

    Approximately 11,000 liters (3,600) gallons of solution containing isotopes of Am and Cm are currently stored in F-Canyon Tank 17.1. These isotopes were recovered during plutonium-242 production campaigns in the mid- and late-1970s. Experimental work for the project began in 1995 by the Savannah River Technology Center (SRTC). Details of the process are given in the various sections of this document.

  14. Biosorption of radionuclide Americium-241 by A. niger spore and hyphae

    International Nuclear Information System (INIS)

    The biosorption of radionuclide 241Am from solution was studied by a. niger spore and hyphae, and the effects of the operational conditions on the treatment were investigated. The results showed the treatment by A. niger spore and hyphae were very efficient. An average of 96% of the total 241Am was removed from 241Am solutions of 5.6-111 MBq/L (C0), with adsorption capacities (W) of 7.2-142.4 MBq/g biomass, 5.2-106.5 MBq/g, respectively. The biosorption equilibrium was achieved within 1 h and the optimum pH value ranged 3-0.1 mol/L HNO3 and 3-2 for spore and hyphae of A. niger, respectively. No significant effects on 241Am biosorption were observed at 15 degree C-45 degree C, or challenged with containing Au3+ or Ag+, even 2000 times above 241Am amount. the index relationship between concentrations and adsorption capacities of 241Am indicated that the 241Am biosorption by A. niger spore and hyphae obey to Freundlich adsorption equation. The adsorption behavior of A. niger spore and hyphae were basically coincident

  15. Americium and plutonium release behavior from irradiated mixed oxide fuel during heating

    Science.gov (United States)

    Sato, I.; Suto, M.; Miwa, S.; Hirosawa, T.; Koyama, S.

    2013-06-01

    The release behavior of Pu and Am was investigated under the reducing atmosphere expected in sodium cooled fast reactor severe accidents. Irradiated Pu and U mixed oxide fuels were heated at maximum temperatures of 2773 K and 3273 K. EPMA, γ-ray spectrometry and α-ray spectrometry for released and residual materials revealed that Pu and Am can be released more easily than U under the reducing atmosphere. The respective release rate coefficients for Pu and Am were obtained as 3.11 × 10-4 min-1 and 1.60 × 10-4 min-1 at 2773 K under the reducing atmosphere with oxygen partial pressure less than 0.02 Pa. Results of thermochemical calculations indicated that the main released chemical forms would likely be PuO for Pu and Am for Am under quite low oxygen partial pressure.

  16. Fabrication of uranium-americium mixed oxide fuels: thermodynamical modeling and materials properties

    International Nuclear Information System (INIS)

    Fuel irradiation in pressurized water reactors lead to the formation of fission products and minor actinides (Np, Am, Cm) which can be transmuted in fast neutrons reactors. In this context, the aim of this work was to study the fabrication conditions of the U1-yAmyO2+x fuels which exhibit particular thermodynamical properties requiring an accurate monitoring of the oxygen potential during the sintering step. For this reason, a thermodynamical model was developed to assess the optimum sintering conditions for these materials. From these calculations, U1-yAmyO2+x (y=0.10; 0.15; 0.20; 0.30) were sintered in two range of atmosphere. In hyper-stoichiometric conditions at low temperature, porous and multiphasic compounds are obtained whereas in reducing conditions at high temperature materials are dense and monophasic. XAFS analyses were performed in order to obtain additional experimental data for the thermodynamical modeling refinement. These characterizations also showed the reduction of Am(+IV) to Am(+III) and the partial oxidation of U(+IV) to U(+V) due to a charge compensation mechanism occurring during the sintering. Finally, taking into account the high - activity of Am, self-irradiation effects were studied for two types of microstructures and two Am contents (10 and 15%). For each composition, a lattice parameter increase was observed without structural change coupled with a macroscopic swelling of the pellet diameter up to 1.2% for the dense compounds and 0.6% for the tailored porosity materials. (author)

  17. Chemical behaviour of americium in natural aquatic solutions: Hydrolysis, radiolysis and redox reactions

    International Nuclear Information System (INIS)

    Hydrolysis and redox reactions of the Am(III) and Am(V) ions have been investigated in NaClO4 and NaCl solutions as well as in natural saline groundwaters. The hydrolysis constants of Am(OH)n3-n species and the solubility product of Am(OH)3(s) have been determined in 0.1 M NaClO4, 0.1 M NaCl and 0.6 M NaCl solutions. As observed in concentrated NaCl solutions (> 3 M), the α-radiation induces the radiolytic oxidation of the Cl--ion to produce Cl2, HClO, ClO- and other oxidized species, which result in a strongly oxidizing medium. Consequently Am(III) is oxidized to Am(V). Under these conditions the hydrolysis constants of AmO2(OH)n1-n species and the solubility product are also determined. The α-radiation induced radiolysis reactions in NaCl solution and the subsequent oxidation reaction of Am(III) have been systematically investigated by varying pH, NaCl concentration and specific α-activity. Also included in the investigation are a few selected groundwaters of relatively high salinity from the Gorleben aquifer systems. (orig.)

  18. Effect of solvent on in vitro dissolution: Summary of results for uranium, americium, and cobalt aerosols

    International Nuclear Information System (INIS)

    The revised 10 CFR Part 20 has adopted the ICRP Publication 30 method for calculating the committed effective dose equivalent from intakes of radionuclides. This dosimetry scheme requires knowledge or assumptions about the chemical form of the radionuclide, its particle size, and its known or assumed solubility. The solubility is classified as being either D (relatively soluble), W, or Y (relatively insoluble), depending on whether the material dissolves over periods of days, weeks, or years. Although Nuclear Regulatory Commission licensees may wish to take advantage of material-specific knowledge in order to adjust annual limits on intake and derived air concentrations, relatively few radioactive materials to which workers and the general population may be exposed have been adequately characterized either in terms of physicochemical form or solubility. Experimental measurement of solubility using some type of in vitro dissolution measurement system is therefore needed. However, there is currently no clear consensus regarding the appropriate design of in vitro dissolution systems, particularly when considering the range of different radionuclides to be studied, and the complexity of the biological mechanisms involved in the retention and clearance of inhaled deposited radioactive particles. The purpose of this study was to evaluate the effect of the several solvents on the dissolution of four test aerosols (57Co3O4, 241AmO2, ammonium diuranate [ADU], and U3O8) selected to encompass a variety of chemical and biochemical properties in vivo. The results of this study provide some guidance on the usefulness of in vitro dissolution tests for estimating the solubility of unknown radionuclide particles within the context of a simple model such as the class D, W, and Y formulation of ICRP 30

  19. Americium and plutonium separation by extraction chromatography for determination by accelerator mass spectrometry

    Energy Technology Data Exchange (ETDEWEB)

    Kazi, Zakir H. [Department of Earth Science, University of Ottawa, 140 Louis Pasteur Avenue, Ottawa K1N 6N5 (Canada); Cornett, Jack R., E-mail: jack.cornett@uottawa.ca [Department of Earth Science, University of Ottawa, 140 Louis Pasteur Avenue, Ottawa K1N 6N5 (Canada); Zhao, Xaiolei; Kieser, Liam [Department of Physics, University of Ottawa, 140 Louis Pasteur Avenue, Ottawa K1N 6N5 (Canada)

    2014-06-01

    Highlights: • Am and Pu were adsorbed and separated using a single extraction chromatography DGA column. • Pu was eluted from the column completely using on-column reduction of Pu(IV) to Pu(III). • ²⁴¹Am and 239,240Pu measurements by accelerator mass spectrometry (AMS) agree with the certified values in two SRMs. Abstract: A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N',N'-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8 M HNO₃ with 0.05 M NaNO₂ before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO₃, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl₃ facilitated the complete desorption of Pu. Interferences (e.g. Ca²⁺, Fe³⁺) were washed off from the resin bed with excess HNO₃. Using NdF₃, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7 ± 5.3% and 95.5 ± 4.6% for ²⁴¹Am and ²⁴²Pu respectively in reagents without a matrix. The recoveries of the same isotopes were 99.1 ± 6.0 and 96.8 ± 5.3% respectively in garden soil. The robustness of the method was validated using certified reference materials (IAEA 384 and IAEA 385). The measurements agree with the certified values over a range of about 1–100 Bq kg⁻¹. The single column separation of Pu and Am saves reagents, separation time, and cost.

  20. New Synthetic Methods and Structure-Property Relationships in Neptunium, Plutonium, and Americium Borates. Final report

    Energy Technology Data Exchange (ETDEWEB)

    Albrecht-Schmitt, Thomas Edward

    2013-09-14

    The past three years of support by the Heavy Elements Chemistry Program have been highly productive in terms of advanced degrees awarded, currently supported graduate students, peer-reviewed publications, and presentations made at universities, national laboratories, and at international conferences. Ph.D. degrees were granted to Shuao Wang and Juan Diwu, who both went on to post-doctoral appointments at the Glenn T. Seaborg Center at Lawrence Berkeley National Laboratory with Jeff Long and Ken Raymond, respectively. Pius Adelani completed his Ph.D. with me and is now a post-doc with Peter C. Burns. Andrea Alsobrook finished her Ph.D. and is now a post-doc at Savannah River with Dave Hobbs. Anna Nelson completed her Ph.D. and is now a post-doc with Rod Ewing at the University of Michigan. As can be gleaned from this list, students supported by the Heavy Elements Chemistry grant have remained interested in actinide science after leaving my program. This follows in line with previous graduates in this program such as Richard E. Sykora, who did his post-doctoral work at Oak Ridge National Laboratory with R. G. Haire, and Amanda C. Bean, who is a staff scientist at Los Alamos National Laboratory, and Philip M. Almond and Thomas C. Shehee, who are both staff scientists at Savannah River National Laboratory, Gengbang Jin who is a staff scientist at Argonne National Lab, and Travis Bray who has been a post-doc at both LBNL and ANL. Clearly this program is serving as a pipe-line for students to enter into careers in the national laboratories. About half of my students depart the DOE complex for academia or industry. My undergraduate researchers also remain active in actinide chemistry after leaving my group. Dan Wells was a productive undergraduate of mine, and went on to pursue a Ph.D. on uranium and neptunium chalcogenides with Jim Ibers at Northwestern. After earning his Ph.D., he went directly into the nuclear industry.

  1. Separation of Americium from Fission Product Lanthanides Using Cyanex 301 Extraction

    Institute of Scientific and Technical Information of China (English)

    ZHU Yongjun; CHEN Jing

    2001-01-01

    The extraction behavior of bis (2,4,4-trimethylpentyl)dithiophosphinic acid (HBTMPDTP),purified from Cyanex 301,was studied for extracting Am3+ and trivalent lanthanides (Lns).HBTMPDTP shows very high selectivity for Am.Separation factor(SF)of Am and Eu,SF Am/Eu,(trace amount)reaches a high value of 5.9×103 and SF Am/(Pr+Nd) (macro amount)is about 2×103.The mathematical model for the distribution ratios and process parameters calculated for HBTMPDTP extraction was established and the calculated results were verified experimentally.In a five-stage countercurrent process,the extraction rates of Am and Lns were >99.999% and 0.14%,respectively,to fulfill the separation requirements.The efficiency of this process was also verified in a cross-flow extraction experiment using a genuine Am-FPLns fraction.In the presence of TBP,the extraction of Am and Eu is enhanced,but their separation is reduced to some extent.A fairly good separation was achieved in a fractional extraction process using a mixture of HBTMPDTP and TBP in kerosene at low pH.

  2. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

    Science.gov (United States)

    Jandel, M.; Bredeweg, T. A.; Stoyer, M. A.; Wu, C. Y.; Fowler, M. M.; Becker, J. A.; Bond, E. M.; Couture, A.; Haight, R. C.; Haslett, R. J.; Henderson, R. A.; Keksis, A. L.; O'Donnell, J. M.; Rundberg, R. S.; Ullmann, J. L.; Vieira, D. J.; Wilhelmy, J. B.; Wouters, J. M.

    2009-01-01

    Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for 241Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for 243Am for neutron energies between 10 eV and 250 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on 242mAm will be presented where the fission events were actively triggered during the experiments. In these experiments, a Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,γ) events from (n,f) events. The first direct observation of neutron capture on 242mAm in the resonance region in between 2 and 9 eV of the neutron energy was obtained.

  3. Plutonium and americium in air on the coasts of the Irish Sea

    International Nuclear Information System (INIS)

    Measurements of artificial radionuclides in air, deposition and seawater were carried out at coastal and inland locations in Cumbria, south-west Scotland, Northern Ireland and North Wales. The measurements were undertaken to determine the distribution of artificial radionuclides in the coastal environment attributable to discharges from Sellafield and to investigate the mechanisms responsible for the increased radionuclide concentration in the marine aerosol and their subsequent transfer to land. A number of different sampling methods were used and the contribution each method could make to the understanding of the marine aerosol was assessed. Measurements of the size distribution of the marine aerosol was also undertaken. The measurements demonstrated that the actinide concentrations measured in the air and deposition at coastal locations could be related to near shore sea water concentrations, but that no direct proportionality existed. It was also determined that a significant proportion of the material transferred from sea to land was associated with larger particulate present in the marine aerosol during conditions of above average onshore winds. (author)

  4. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

    Energy Technology Data Exchange (ETDEWEB)

    Jandel, Marian [Los Alamos National Laboratory

    2008-01-01

    Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for {sup 241}Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for {sup 243}Am for neutron energies between 35 eV and 200 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on {sup 242m}Am will be presented, where the fission events were actively triggered during the experiments. In these experiments, the Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,{gamma}) from (n,f) events. The first evidence of neutron capture on {sup 242m}Am in the resonance region in between 2 and 9 eV of the neutron energy was obtained.

  5. Concordant plutonium-241-americium-241 dating of environmental samples: results from forest fire ash

    Energy Technology Data Exchange (ETDEWEB)

    Goldstein, Steven J [Los Alamos National Laboratory; Oldham, Warren J [Los Alamos National Laboratory; Murrell, Michael T [Los Alamos National Laboratory; Katzman, Danny [Los Alamos National Laboratory

    2010-12-07

    We have measured the Pu, {sup 237}Np, {sup 241}Am, and {sup 151}Sm isotopic systematics for a set of forest fire ash samples from various locations in the western U.S. including Montana, Wyoming, Idaho, and New Mexico. The goal of this study is to develop a concordant {sup 241}Pu (t{sub 1/2} = 14.4 y)-{sup 241}Am dating method for environmental collections. Environmental samples often contain mixtures of components including global fallout. There are a number of approaches for subtracting the global fallout component for such samples. One approach is to use {sup 242}/{sup 239}Pu as a normalizing isotope ratio in a three-isotope plot, where this ratio for the nonglobal fallout component can be estimated or assumed to be small. This study investigates a new, complementary method of normalization using the long-lived fission product, {sup 151}Sm (t{sub 1/2} = 90 y). We find that forest fire ash concentrates actinides and fission products with {approx}1E10 atoms {sup 239}Pu/g and {approx}1E8 atoms {sup 151}Sm/g, allowing us to measure these nuclides by mass spectrometric (MIC-TIMS) and radiometric (liquid scintillation counting) methods. The forest fire ash samples are characterized by a western U.S. regional isotopic signature representing varying mixtures of global fallout with a local component from atmospheric testing of nuclear weapons at the Nevada Test Site (NTS). Our results also show that {sup 151}Sm is well correlated with the Pu nuclides in the forest fire ash, suggesting that these nuclides have similar geochemical behavior in the environment. Results of this correlation indicate that the {sup 151}Sm/{sup 239}Pu atom ratio for global fallout is {approx}0.164, in agreement with an independent estimate of 0.165 based on {sup 137}Cs fission yields for atmospheric weapons tests at the NTS. {sup 241}Pu-{sup 241}Am dating of the non-global fallout component in the forest fire ash samples yield ages in the late 1950's-early 1960's, consistent with a peak in NTS weapons testing at that time. The age results for this component are in agreement using both {sup 242}Pu and {sup 151}Sm normalizations, although the errors for the {sup 151}Sm correction are currently larger due to the greater uncertainty of their measurements. Additional efforts to develop a concordant {sup 241}Pu-{sup 241}Am dating method for environmental collections are underway with emphasis on soil cores.

  6. Neutron capture and neutron-induced fission experiments on americium isotopes with DANCE

    International Nuclear Information System (INIS)

    Neutron capture cross section data on Am isotopes were measured using the Detector for Advanced Neutron Capture Experiments (DANCE) at Los Alamos National Laboratory. The neutron capture cross section was determined for 241Am for neutron energies between thermal and 320 keV. Preliminary results were also obtained for 243Am for neutron energies between 35 eV and 200 keV. The results on concurrent neutron-induced fission and neutron-capture measurements on 242mAm will be presented, where the fission events were actively triggered during the experiments. In these experiments, the Parallel-Plate Avalanche Counter (PPAC) detector that surrounds the target located in the center of the DANCE array was used as a fission-tagging detector to separate (n,γ) from (n,f) events. The first evidence of neutron capture on 242mAm in the resonance region in between 2 and 9 eV of the neutron energy was obtained.

  7. Mean squared slowing-down distance and age of americium-beryllium neutrons in perspex

    International Nuclear Information System (INIS)

    THe mean squared slowing-down distance 2>, and the age to thermal capture (Migration Area), M2, are direct measures of the slowing.down, and the spreading out, processes of neutrons in a medium. They also enter directly into reactor calculations. These parameters have been determined experimentally for Am-Be neutrons (mean energy 4.46 MeV), in a block of perspex, using the activities induced in thin indium foils from the 115In(n,γ)116In reactions. (author) 13 refs.; 5 figs.; 2 tabs

  8. Americium-Curium Stabilization - 5'' Cylindrical Induction Melter System Design Basis

    International Nuclear Information System (INIS)

    Approximately 11,000 liters (3,600) gallons of solution containing isotopes of Am and Cm are currently stored in F-Canyon Tank 17.1. These isotopes were recovered during plutonium-242 production campaigns in the mid- and late-1970s. Experimental work for the project began in 1995 by the Savannah River Technology Center (SRTC). Details of the process are given in the various sections of this document

  9. Effect of solvent on in vitro dissolution: Summary of results for uranium, americium, and cobalt aerosols

    Energy Technology Data Exchange (ETDEWEB)

    Guilmette, R.A.; Hoover, M.D.

    1995-12-01

    The revised 10 CFR Part 20 has adopted the ICRP Publication 30 method for calculating the committed effective dose equivalent from intakes of radionuclides. This dosimetry scheme requires knowledge or assumptions about the chemical form of the radionuclide, its particle size, and its known or assumed solubility. The solubility is classified as being either D (relatively soluble), W, or Y (relatively insoluble), depending on whether the material dissolves over periods of days, weeks, or years. Although Nuclear Regulatory Commission licensees may wish to take advantage of material-specific knowledge in order to adjust annual limits on intake and derived air concentrations, relatively few radioactive materials to which workers and the general population may be exposed have been adequately characterized either in terms of physicochemical form or solubility. Experimental measurement of solubility using some type of in vitro dissolution measurement system is therefore needed. However, there is currently no clear consensus regarding the appropriate design of in vitro dissolution systems, particularly when considering the range of different radionuclides to be studied, and the complexity of the biological mechanisms involved in the retention and clearance of inhaled deposited radioactive particles. The purpose of this study was to evaluate the effect of the several solvents on the dissolution of four test aerosols ({sup 57}Co{sub 3}O{sub 4}, {sup 241}AmO{sub 2}, ammonium diuranate [ADU], and U{sub 3}O{sub 8}) selected to encompass a variety of chemical and biochemical properties in vivo. The results of this study provide some guidance on the usefulness of in vitro dissolution tests for estimating the solubility of unknown radionuclide particles within the context of a simple model such as the class D, W, and Y formulation of ICRP 30.

  10. Distribution of plutonium and americium in human and animal tissues after chronic exposures

    International Nuclear Information System (INIS)

    The distribution of plutonium in the tissues of a group of southern Finns was determined. Their Pu intake had been solely from fallout via inhalation. A group of northern Finns was also studied. They obtain most of the Pu from inhalation, but also some from their diet which is rich in reindeer liver. Reindeer obtain large amounts of transuranium elements in their natural winter diet, which mainly consists of lichen. Pu-239, 240 and Am-241 were also analyzed in elk because it is closely related to reindeer but does not feed on lichen. It was found that much of the Am-241 in reindeer tissues is due to ingrowth from Pu-241 in the animal. The aim of this study to establish whether this situation is also true for the human bone. (H.K.)

  11. Separation of americium(III) from lanthanides(III) by nanofiltration-complexation in aqueous medium

    International Nuclear Information System (INIS)

    The separation of Am(III) from a mixture of lanthanides(III) was performed in aqueous medium by nanofiltration combined with a complexation step using a DTPA derivative as selective complexing agent. (author)

  12. Optimization of TRPO Process Parameters for Americium Extraction from High Level Waste

    Institute of Scientific and Technical Information of China (English)

    CHEN Jing; WANG Jianchen; SONG Chongli

    2001-01-01

    The numerical calculations for Am multistage fractional extraction by trialkyl phosphine oxide (TRPO) were verified by a hot test.1750 L/t-U high level waste (HLW) was used as the feed to the TRPO process.The analysis used the simple objective function to minimize the total waste content in the TRPO process streams.Some process parameters were optimized after other parameters were selected.The optimal process parameters for Am extraction by TRPO are:10 stages for extraction and 2 stages for scrubbing;a flow rate ratio of 0.931 for extraction and 4.42 for scrubbing;nitric acid concentration of 1.35 mol/L for the feed and 0.5 mol/L for the scrubbing solution.Finally,the nitric acid and Am concentration profiles in the optimal TRPO extraction process are given.

  13. Functional sorbents for selective capture of plutonium, americium, uranium, and thorium in blood.

    Science.gov (United States)

    Yantasee, Wassana; Sangvanich, Thanapon; Creim, Jeffery A; Pattamakomsan, Kanda; Wiacek, Robert J; Fryxell, Glen E; Addleman, R Shane; Timchalk, Charles

    2010-09-01

    Self-assembled monolayer on mesoporous supports (SAMMS) are hybrid materials created from attachment of organic moieties onto very high surface area mesoporous silica. SAMMS with surface chemistries including three isomers of hydroxypyridinone, diphosphonic acid, acetamide phosphonic acid, glycinyl urea, and diethylenetriamine pentaacetate (DTPA) analog were evaluated for chelation of actinides ((239)Pu, (241)Am, uranium, thorium) from blood. Direct blood decorporation using sorbents does not have the toxicity or renal challenges associated with traditional chelation therapy and may have potential applications for critical exposure cases, reduction of nonspecific dose during actinide radiotherapy, and for sorbent hemoperfusion in renal insufficient patients, whose kidneys clear radionuclides at a very slow rate. Sorption affinity (K(d)), sorption rate, selectivity, and stability of SAMMS were measured in batch contact experiments. An isomer of hydroxypyridinone (3,4-HOPO) on SAMMS demonstrated the highest affinity for all four actinides from blood and plasma and greatly outperformed the DTPA analog on SAMMS and commercial resins. In batch contact, a fifty percent reduction of actinides in blood was achieved within minutes, and there was no evidence of protein fouling or material leaching in blood after 24 h. The engineered form of SAMMS (bead format) was further evaluated in a 100-fold scaled-down hemoperfusion device and showed no blood clotting after 2 h. A 0.2 g quantity of SAMMS could reduce 50 wt.% of 100 ppb uranium in 50 mL of plasma in 18 min and that of 500 dpm mL(-1) in 24 min. 3,4-HOPO-SAMMS has a long shelf-life in air and at room temperature for at least 8 y, indicating its feasibility for stockpiling in preparedness for an emergency. The excellent efficacy and stability of SAMMS materials in complex biological matrices suggest that SAMMS can also be used as orally administered drugs and for wound decontamination. By changing the organic groups of SAMMS, they can be used not only for actinides but also for other radionuclides. By using the mixture of these SAMMS materials, broad spectrum decorporation of radionuclides is very feasible.

  14. Sorption of americium in tuff and pure minerals using synthetic and natural groundwaters

    International Nuclear Information System (INIS)

    The distribution of Am between selected solid and liquid phases has been studied using initial 241Am solutions with a molarity smaller than 1 x 10-11. The synthetic and natural groundwaters used have pH values in the 7--8 range and a total alkalinity of approximately 1 mN which is mainly due to bicarbonate. Mass spectrometric isotope dilution was utilized to determine the amount of Am in the solution phase initially and after equilibrium was attained. Using this sensitive technique, 7 x 108 atoms of 241Am were accurately measured. Our results indicate that the percent of Am lost to the walls of the container in the absence of geologic material varies from 35 to 84. The Am sorption coefficient determined is on the order of 103 ml/g for clinoptilolite, 104 ml/g for tuff consisting mainly of alkali feldspar and cristobalite, and 105 ml/g for romanechite. 12 refs

  15. Americium-241 and plutonium-237 turnover in mussels ( Mytilus galloprovincialis) living in field enclosures

    Science.gov (United States)

    Guary, J. C.; Fowler, S. W.

    1981-02-01

    Loss of 241Am and 237Pu from contaminated mussels ( Mytilus galloprovincialis) living in situ in the Mediterranean Sea is described as the sum of three exponential functions. In the case of 241Am, two short-lived compartments representing a total of 80% of the incorporated radionuclide turned over rapidly with biological half-lives of 2 and 3 weeks. The remaining fraction of 241Am, associated with a long-lived compartment, was lost at an extremely slow rate ( Tb1/2=1·3 years). Plutonium-237 turnover in the two short-lived compartments (containing 70% of the Pu) was more rapid ( Tb1/2=1-2 days and 2 weeks) than that of 241Am; however, there was some indication that subsequent loss rates of the two radionuclides in long-lived compartments may be similar if determined over comparable periods of time. Loss rates of 241Am differed for the various tissues, with the most rapid rates occurring in gill, viscera and shell. Abrupt changes in loss observed in muscle and mantle suggested a translocation of 241Am to muscle and mantle during depuration. Whole shell contained by far the largest fraction (˜90%) of both 241Am and 237Pu taken up; in addition, these radionuclides are not irreversibly bound to mussel shell but readily leach into the water. These observations suggest that mollusc shell may influence the biogeochemistry of transuranic elements in littoral zones.

  16. New Synthetic Methods and Structure-Property Relationships in Neptunium, Plutonium, and Americium Borates. Final report

    International Nuclear Information System (INIS)

    The past three years of support by the Heavy Elements Chemistry Program have been highly productive in terms of advanced degrees awarded, currently supported graduate students, peer-reviewed publications, and presentations made at universities, national laboratories, and at international conferences. Ph.D. degrees were granted to Shuao Wang and Juan Diwu, who both went on to post-doctoral appointments at the Glenn T. Seaborg Center at Lawrence Berkeley National Laboratory with Jeff Long and Ken Raymond, respectively. Pius Adelani completed his Ph.D. with me and is now a post-doc with Peter C. Burns. Andrea Alsobrook finished her Ph.D. and is now a post-doc at Savannah River with Dave Hobbs. Anna Nelson completed her Ph.D. and is now a post-doc with Rod Ewing at the University of Michigan. As can be gleaned from this list, students supported by the Heavy Elements Chemistry grant have remained interested in actinide science after leaving my program. This follows in line with previous graduates in this program such as Richard E. Sykora, who did his post-doctoral work at Oak Ridge National Laboratory with R. G. Haire, and Amanda C. Bean, who is a staff scientist at Los Alamos National Laboratory, and Philip M. Almond and Thomas C. Shehee, who are both staff scientists at Savannah River National Laboratory, Gengbang Jin who is a staff scientist at Argonne National Lab, and Travis Bray who has been a post-doc at both LBNL and ANL. Clearly this program is serving as a pipe-line for students to enter into careers in the national laboratories. About half of my students depart the DOE complex for academia or industry. My undergraduate researchers also remain active in actinide chemistry after leaving my group. Dan Wells was a productive undergraduate of mine, and went on to pursue a Ph.D. on uranium and neptunium chalcogenides with Jim Ibers at Northwestern. After earning his Ph.D., he went directly into the nuclear industry

  17. Combined procedure using radiochemical separation of plutonium, americium and uranium radionuclides for alpha-spectrometry

    International Nuclear Information System (INIS)

    Radiochemical separation of Pu, Am and U was tested from synthetic solutions and evaporator concentrate samples from nuclear power plants for isolation of each of them for alpha-spectrometry analysis. The separation was performed by anion-exchange chromatography, extraction chromatography, using TRU resin, and precipitation techniques. The aim of the study was to develop a sensitive analytical procedure for the sequential determination of 242Pu, 238Pu, 239+240Pu, 241Am and 235,238U in radioactive wastes. 238Pu, 242Pu, 243Am and 232U were used as tracers. The measurements of α emitting radionuclides were performed by semiconductor detector that is used especially when spectrometric information is needed. For synthetic solutions the chemical recovery was based on associated iron concentration and was about 93%. (author)

  18. Study on the uptake of Americium using PC88A - impregnated macroporous polymeric beads

    International Nuclear Information System (INIS)

    The prime objective of radioactive waste treatment in nuclear industry is to minimize the waste volume by efficient process without generating secondary radioactive waste for its final disposal. Among the currently available technologies, for separation and recovery of metal ions, solvent extraction, ion-exchange, membrane based technologies and solid sorbent materials are more popular means. Though, all these technologies play major role in all the bulk separation processes, their marked limitations force the separation scientists to think of advance, more efficient and technically feasible alternatives. The extractant impregnated polymeric beads (EIMPBs), impregnated with metal-specific extractants, exhibit reliable separation performances under column operation, and hence bridge the gap between solvent extraction and ion exchange techniques. In the present work, PC88A impregnated PES beads are prepared and the sorption of Am (III) from aqueous waste solutions is investigated. The synthesized EIMPBs were characterized by FTIR, TGA and SEM techniques. The physiochemical strength of the beads was found to be excellent. The sorption study of Am (III), using these beads, was carried out by batch equilibration method and the effect of various parameters, like pH, equilibration time, Am (III) concentration, etc., on the sorption process, was investigated. The synthesized polymeric beads presented fairly higher sorption capacity for Am (III) at pH 3. The kinetics of extraction is very fast. The saturation of sorption is achieved in about 60 minutes of equilibration. The sorption kinetics data fits well in the pseudo second-order model, indicating that the sorption is dominated by chemisorptions. The sorption of Am (III) is observed to follow Langmuir isotherm and the monolayer capacity was calculated as 2.498 mg/g. The quantitative stripping of the extracted Am (III) can be achieved by using 0.1M oxalic acid. The blank polymeric beads, without PC88A,have shown negligible sorption of Am (III) under the similar experimental conditions

  19. Americium and plutonium release behavior from irradiated mixed oxide fuel during heating

    International Nuclear Information System (INIS)

    The release behavior of Pu and Am was investigated under the reducing atmosphere expected in sodium cooled fast reactor severe accidents. Irradiated Pu and U mixed oxide fuels were heated at maximum temperatures of 2773 K and 3273 K. EPMA, γ-ray spectrometry and α-ray spectrometry for released and residual materials revealed that Pu and Am can be released more easily than U under the reducing atmosphere. The respective release rate coefficients for Pu and Am were obtained as 3.11 × 10−4 min−1 and 1.60 × 10−4 min−1 at 2773 K under the reducing atmosphere with oxygen partial pressure less than 0.02 Pa. Results of thermochemical calculations indicated that the main released chemical forms would likely be PuO for Pu and Am for Am under quite low oxygen partial pressure

  20. Kinetics of the oxidation-reduction reactions of uranium, neptunium, plutonium, and americium in aqueous solutions

    International Nuclear Information System (INIS)

    This is a review with about 250 references. Data for 240 reactions are cataloged and quantitative activation parameters are tabulated for 79 of these. Some empirical correlations are given. Twelve typical reactions are discussed in detail, along with the effects of self-irradiation and ionic strength. (U.S.)

  1. Americium and plutonium separation by extraction chromatography for determination by accelerator mass spectrometry.

    Science.gov (United States)

    Kazi, Zakir H; Cornett, Jack R; Zhao, Xaiolei; Kieser, Liam

    2014-06-01

    A simple method was developed to separate Pu and Am using single column extraction chromatography employing N,N,N',N'-tetra-n-octyldiglycolamide (DGA) resin. Isotope dilution measurements of Am and Pu were performed using accelerator mass spectrometry (AMS) and alpha spectrometry. For maximum adsorption Pu was stabilized in the tetra valent oxidation state in 8M HNO3 with 0.05 M NaNO2 before loading the sample onto the resin. Am(III) was adsorbed also onto the resin from concentrated HNO3, and desorbed with 0.1 M HCl while keeping the Pu adsorbed. The on-column reduction of Pu(IV) to Pu(III) with 0.02 M TiCl3 facilitated the complete desorption of Pu. Interferences (e.g. Ca(2+), Fe(3+)) were washed off from the resin bed with excess HNO3. Using NdF3, micro-precipitates of the separated isotopes were prepared for analysis by both AMS and alpha spectrometry. The recovery was 97.7±5.3% and 95.5±4.6% for (241)Am and (242)Pu respectively in reagents without a matrix. The recoveries of the same isotopes were 99.1±6.0 and 96.8±5.3% respectively in garden soil. The robustness of the method was validated using certified reference materials (IAEA 384 and IAEA 385). The measurements agree with the certified values over a range of about 1-100 Bq kg(-1). The single column separation of Pu and Am saves reagents, separation time, and cost. PMID:24856406

  2. Rapid selective separation of americium/curium from simulated nuclear forensic matrices using triazine ligands

    International Nuclear Information System (INIS)

    In analysis of complex nuclear forensic samples containing lanthanides, actinides and matrix elements, rapid selective extraction of Am/Cm for quantification is challenging, in particular due the difficult separation of Am/Cm from lanthanides. Here we present a separation process for Am/Cm(III) which is achieved using a combination of AG1-X8 chromatography followed by Am/Cm extraction with a triazine ligand. The ligands tested in our process were CyMe4-BTPhen, CyMe4-BTBP, CA-BTP and CA-BTPhen. Our process allows for purification and quantification of Am and Cm (recoveries 80% - 100%) and other major actinides in < 2 d without the use of multiple columns or thiocyanate. The process is unaffected by high level Ca(II)/Fe(III)/Al(III) (10 mg mL-1) and thus requires little pre-treatment of samples.

  3. Rapid selective separation of americium/curium from simulated nuclear forensic matrices using triazine ligands

    Energy Technology Data Exchange (ETDEWEB)

    Higginson, Matthew A.; Livens, Francis R.; Heath, Sarah L. [Manchester Univ. (United Kingdom). Centre for Radiochemistry Research; Thompson, Paul; Marsden, Olivia J. [AWE, Aldermaston, Reading (United Kingdom); Harwood, Laurence M.; Hudson, Michael J. [Reading Univ. (United Kingdom). Dept. of Chemistry; Lewis, Frank W. [Reading Univ. (United Kingdom). Dept. of Chemistry; Northumbria Univ., Newcastle upon Tyne (United Kingdom). Dept. of Chemical and Forensic Sciences

    2015-07-01

    In analysis of complex nuclear forensic samples containing lanthanides, actinides and matrix elements, rapid selective extraction of Am/Cm for quantification is challenging, in particular due the difficult separation of Am/Cm from lanthanides. Here we present a separation process for Am/Cm(III) which is achieved using a combination of AG1-X8 chromatography followed by Am/Cm extraction with a triazine ligand. The ligands tested in our process were CyMe{sub 4}-BTPhen, CyMe{sub 4}-BTBP, CA-BTP and CA-BTPhen. Our process allows for purification and quantification of Am and Cm (recoveries 80% - 100%) and other major actinides in < 2 d without the use of multiple columns or thiocyanate. The process is unaffected by high level Ca(II)/Fe(III)/Al(III) (10 mg mL{sup -1}) and thus requires little pre-treatment of samples.

  4. Subsurface Behavior of Plutonium and Americium at Non-Hanford Sites and Relevance to Hanford

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J.; Riley, Robert G.

    2008-02-01

    Seven sites where Pu release to the environment has raised significant environmental concerns have been reviewed. A summary of the most significant hydrologic and geochemical features, contaminant release events and transport processes relevant to Pu migration at the seven sites is presented.

  5. Epitaxial gamma-iron silicide grown on single-crystal Si. A summary of Moessbauer results

    Energy Technology Data Exchange (ETDEWEB)

    Desimoni, J.; Sanchez, F.H

    1998-08-15

    Metastable {gamma}-FeSi{sub 2} grown on or into single-crystals of silicon can be produced by different techniques as molecular beam epitaxy, and ion implantation followed by ion beam induced epitaxial crystallisation. In these investigations, Moessbauer effect has been used to provide short range order information about the system. We present here a summary of these results, which will be compared and discussed.

  6. Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

    Energy Technology Data Exchange (ETDEWEB)

    Afshar-Mohajer, M. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Yaghoubi, A., E-mail: yaghoubi@siswa.um.edu.my [Center for High Impact Research, University of Malaya, Kuala Lumpur 50603 (Malaysia); Ramesh, S., E-mail: ramesh79@um.edu.my [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Bushroa, A.R.; Chin, K.M.C.; Tin, C.C. [Center for Advanced Manufacturing and Material Processing, Department of Mechanical Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603 (Malaysia); Chiu, W.S. [Low Dimensional Materials Research Center, Department of Physics, University of Malaya, Kuala Lumpur 50603 (Malaysia)

    2014-07-01

    Magnesium silicates (Mg{sub x}SiO{sub y}) and in particular forsterite (Mg{sub 2}SiO{sub 4}) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti{sub 5}Si{sub 3} layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

  7. Economical analysis to utilize MTR fuel elements using silicides in research reactors

    International Nuclear Information System (INIS)

    According to international programs on reducing enrichment in research reactors and the necessity to maintain their operation, new fuel elements have been developed in order to meet both objectives. Thus, U-Si alloy fuel elements for research reactors are becoming of greater interest for the international markets. It became necessary to make an economic study about the convenience of introducing this type of fuel elements in the RA-3 reactor and to know the potentiality of this fuel. The economical behavior of the reactor operation has been evaluated comparing the actual U3O8 nuclear fuel cycle with U3Si2 nuclear fuels. Results obtained show that the main economical factor to determine the change of fuels is the cost of fabrication, and the change is advisable up to an 80% difference. The other factors related to the cost of nuclear fuel cycle are not relevant or have real minor impacts. (author)

  8. Electrophoretic deposition of magnesium silicates on titanium implants: Ion migration and silicide interfaces

    International Nuclear Information System (INIS)

    Magnesium silicates (MgxSiOy) and in particular forsterite (Mg2SiO4) owing to their low thermal expansion mismatch with metals are promising materials for bioactive coating of implants. Here, we report the electrophoretic deposition (EPD) of forsterite onto titanium substrates using different precursors. Unlike bulk samples which achieve full stoichiometry only beyond 1400 °C, non-stoichiometric magnesium silicate rapidly decomposes into magnesium oxide nanowires during sintering. Elemental mapping and X-ray diffraction suggest that oxygen diffusion followed by ion exchange near the substrate leads to formation of an interfacial Ti5Si3 layer. Pre-annealed forsterite powder on the other hand shows a comparatively lower diffusion rate. Overall, magnesium silicate coatings do not exhibit thermally induced microcracks upon sintering as opposed to calcium phosphate bioceramics which are currently in use.

  9. New semiconducting silicides assembled from transition-metal-encapsulating Si clusters

    Energy Technology Data Exchange (ETDEWEB)

    Uchida, Noriyuki, E-mail: nori-uchida@aist.go.jp [Nanodevice Innovation Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Miyazaki, Takehide [Nanosystem Research Institute, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Umezono, Tsukuba 305-8568 (Japan); Matsushita, Yusuke; Sameshima, Kenichiro; Kanayama, Toshihiko [Nanodevice Innovation Research Center, National Institute of Advanced Industrial Science and Technology (AIST), 1-1-1 Higashi, Tsukuba 305-8562 (Japan); Institute of Applied Physics, University of Tsukuba, Tennoudai, Tsukuba 305-8573 (Japan)

    2011-10-03

    We synthesized amorphous films composed of transition-metal-encapsulating Si clusters (MSi{sub n}: M = Zr, Nb, Mo and W) by deposition of hydrogenated MSi{sub n}H{sub x} clusters onto solid substrates followed by annealing at 400-500 deg. C for dehydrogenation. The MSi{sub n} (n = 7-20) cluster films are amorphous semiconductors with an optical gap > 0.4 eV and have larger electron and hole mobility than that of the hydrogenated amorphous Si (a-Si:H) film. In these films, while Si atoms form amorphous networks similar to those in a-Si:H films, the thermal stability is enhanced and the electronic disorder is reduced by the use of MSi{sub n} clusters as the unit structures. Structure modeling by ab initio calculations for MSi{sub n} films suggests that the encapsulated M atom works as a terminator of dangling bonds of the Si network.

  10. Polaronic transport and current blockades in epitaxial silicide nanowires and nanowire arrays.

    Science.gov (United States)

    Iancu, Violeta; Zhang, X-G; Kim, Tae-Hwan; Menard, Laurent D; Kent, P R C; Woodson, Michael E; Ramsey, J Michael; Li, An-Ping; Weitering, Hanno H

    2013-08-14

    Crystalline micrometer-long YSi2 nanowires with cross sections as small as 1 × 0.5 nm(2) can be grown on the Si(001) surface. Their extreme aspect ratios make electron conduction within these nanowires almost ideally one-dimensional, while their compatibility with the silicon platform suggests application as metallic interconnect in Si-based nanoelectronic devices. Here we combine bottom-up epitaxial wire synthesis in ultrahigh vacuum with top-down miniaturization of the electrical measurement probes to elucidate the electronic conduction mechanism of both individual wires and arrays of nanowires. Temperature-dependent transport through individual nanowires is indicative of thermally assisted tunneling of small polarons between atomic-scale defect centers. In-depth analysis of complex wire networks emphasize significant electronic crosstalk between the nanowires due to the long-range Coulomb fields associated with polaronic charge fluctuations. This work establishes a semiquantitative correlation between the density and distributions of atomic-scale defects and resulting current-voltage characteristics of nanoscale network devices. PMID:23902411

  11. On the ground electronic states of copper silicide and its ions

    OpenAIRE

    Boldyrev, Alexander I.; Simons, Jack; Scherer, J. J.; J. B. Paul; Collier, C. P.; Saykally, R. J.

    1998-01-01

    The low-lying electronic states of SiCu, SiCu^+, and SiCu^− have been studied using a variety of high-level ab initio techniques. As expected on the basis of simple orbital occupancy and bond forming for Si(s^2p^2)+Cu(s^1) species, ^2Π_r, ^1Σ^+, and ^3Σ^− states were found to be the ground electronic states for SiCu, SiCu^+, and SiCu^−, respectively; the ^2Π_r state is not that suggested in most recent experimental studies. All of these molecules were found to be quite strongly bound although...

  12. On the ground electronic states of copper silicide and its ions

    Science.gov (United States)

    Boldyrev, Alexander I.; Simons, Jack; Scherer, J. J.; Paul, J. B.; Collier, C. P.; Saykally, R. J.

    1998-04-01

    The low-lying electronic states of SiCu, SiCu+, and SiCu- have been studied using a variety of high-level ab initio techniques. As expected on the basis of simple orbital occupancy and bond forming for Si(s2p2)+Cu(s1) species, 2Πr, 1Σ+, and 3Σ- states were found to be the ground electronic states for SiCu, SiCu+, and SiCu-, respectively; the 2Πr state is not that suggested in most recent experimental studies. All of these molecules were found to be quite strongly bound although the bond lengths, bond energies, and harmonic frequencies vary slightly among them, as a result of the nonbonding character of the 2π-MO (molecular orbital) [composed almost entirely of the Si 3p-AO (atomic orbital)], the occupation of which varies from 0 to 2 within the 1Σ+, 2Πr, and 3Σ- series. The neutral SiCu is found to have bound excited electronic states of 4Σ-, 2Δ, 2Σ+, and 2Πi symmetry lying 0.5, 1.2, 1.8, and 3.2 eV above the 2Πr ground state. It is possible but not yet certain that the 2Πi state is, in fact, the "B state" observed in the recent experimental studies by Scherer, Paul, Collier, and Saykally.

  13. Soft-x-ray fluorescence study of buried silicides in antiferromagnetically coupled Fe/Si multilayers

    Energy Technology Data Exchange (ETDEWEB)

    Carlisle, J.A.; Chaiken, A.; Michel, R.P. [Lawrence Berkeley National Lab., CA (United States)] [and others

    1997-04-01

    Multilayer films made by alternate deposition of two materials play an important role in electronic and optical devices such as quantum-well lasers and x-ray mirrors. In addition, novel phenomena like giant magnetoresistance and dimensional crossover in superconductors have emerged from studies of multilayers. While sophisticated x-ray techniques are widely used to study the morphology of multilayer films, progress in studying the electronic structure has been slower. The short mean-free path of low-energy electrons severely limits the usefulness of photoemission and related electron free path of low-energy electrons severely limit spectroscopies for multilayer studies. Soft x-ray fluorescence (SXF) is a bulk-sensitive photon-in, photon-out method to study valence band electronic states. Near-edge x-ray absorption fine-structure spectroscopy (NEXAFS) measured with partial photon yield can give complementary bulk-sensitive information about unoccupied states. Both these methods are element-specific since the incident x-ray photons excite electrons from core levels. By combining NEXAFS and SXF measurements on buried layers in multilayers and comparing these spectra to data on appropriate reference compounds, it is possible to obtain a detailed picture of the electronic structure. Results are presented for a study of a Fe/Si multilayer system.

  14. Fabrication and Microstructure Evolution of Niobium-Niobium Silicide Composites by Spark Plasma Sintering

    Institute of Scientific and Technical Information of China (English)

    CHEN Zhe; YAN Youwei

    2007-01-01

    By using Nb and Si elemental powders as raw materials, dense Nb/Nb5Si3 composites were successfully fabricated by a spark plasma sintering (SPS) technology. The microstructure of the fabricated composites was analyzed by OM, SEM, XRD and EPMA; the microstructure evolution of the composites was also investigated by a quenching test. The experimental results show that the prepared composites consist of Nb and Nb5Si3 phases; Nb particle uniformly distributes in the in-situ synthesized Nb5Si3 matrix. During the SPS process, an interfacial reaction occurs between Nb and Si particles to synthesize Nb5Si3 until reactant silicon has been completely depleted.

  15. Some recent observations on the radiation behavior of uranium silicide dispersion fuel

    Energy Technology Data Exchange (ETDEWEB)

    Hofman, G.L.

    1988-01-01

    Addition of B{sub 4}C burnable poison results in higher plate swelling in both U{sub 3}Si{sub 2} and U{sub 3}Si-Al dispersion fuel plates and also decreases the blister threshold temperature of these plates. Prolonged annealing of U{sub 3}Si{sub 2}-Al fuel plates produced no blister after 696 hours at 400{degrees}C. Blister formation started between 257 hours and 327 hours at 425{degrees}C and between 115 hours and 210 hours at 450{degrees}C. Operation with breached cladding resulted in pillowing of an U{sub 3}Si-Al fuel plate due to reaction of the fuel core with coolant water. 4 refs., 10 figs., 2 tabs.

  16. Burn-Up Dependence of Bubble Morphology of Uranium Silicide Dispersion Fuels Used in Research Reactor

    International Nuclear Information System (INIS)

    Burn-up dependence of fission gas bubble morphology of U3Si2-Al and U3Si-Al dispersion fuels are reviewed with the data of ANL(Argonne Nation Laboratory) and KAERI(Korea Atomic Energy Research Institute

  17. Progress in the development of uranium silicide (U3Si2) fuel at BATAN

    International Nuclear Information System (INIS)

    After successful fabrication of two full-size prototype fuel elements containing ∼3.0 gU/cm3 in the form of U3Si2-Al dispersion now undergoing irradiation in the Reaktor Serba Guna G.A. Siwabessy (RSG-GAS) core since 1990, further development in U3Si2-A2 dispersion fuel element manufacturing has been pursued, whose progress in discussed in this paper, with a special attention on the use of much higher-loading aimed at obtaining a better understanding on the influence of higher-loading on fuel core and plate manufacturing and quality. At present, high-loading U3Si2-AI dispersion miniplates are being manufactured for preparing some mini-fuel elements to be test-irradiated in the new MTR in-pile loop of the RSG-GAS. (author)

  18. Radiocaesium, plutonium and americium partitioning and solid speciation in sized, inter-tidal sediments from Strangford Lough

    International Nuclear Information System (INIS)

    Fine-grained surface (0-2 cm) sediment was collected at an inter-tidal site (Mahee Island) in Strangford Lough, on the NE coast of Ireland in September 1997. The sediment was wet-sieved into standard sized fractions using Endecott test sieves and the fractions assayed for 137Cs, 239,240Pu and 241Am content. Sub-samples of each fraction were measured with a Malvern 2600 laser diffraction analyser, which confirmed that >90% of the particles in each fraction was in the defined size range

  19. Speciation of plutonium and americium in the soils affected by Kraton-3 accidental underground nuclear explosion in Yakutia (Russia)

    International Nuclear Information System (INIS)

    In calcareous soils from Yakutia only 0.1 % or less 239Pu and 241Am exist in water-soluble form, i.e., the mobility of these radionuclides is relatively low. In the top humus-containing layer (0-4 cm) 239Pu and 241Am are distributed uniformly between organic and inorganic soil components. In the bottom soil layer (20-30 cm) the radionuclides are present mainly in inorganic soil components. The estimation of the radionuclide mobility demonstrates that 241Am is potentially a more mobile element than 239Pu. In the considered calcareous soils collected from the top layer 239Pu and 241Am exist both in humic and fulvic acids (FA). 241Am is much stronger bound to the group of mobile FA than 239Pu. In the bottom soil layer 239Pu and 241Am have been found mainly in FA. (author)

  20. LITERATURE REVIEW ON THE SORPTION OF PLUTONIUM, URANIUM, NEPTUNIUM, AMERICIUM AND TECHNETIUM TO CORROSION PRODUCTS ON WASTE TANK LINERS

    Energy Technology Data Exchange (ETDEWEB)

    Li, D.; Kaplan, D.

    2012-02-29

    The Savannah River Site (SRS) has conducted performance assessment (PA) calculations to determine the risk associated with closing liquid waste tanks. The PA estimates the risk associated with a number of scenarios, making various assumptions. Throughout all of these scenarios, it is assumed that the carbon-steel tank liners holding the liquid waste do not sorb the radionuclides. Tank liners have been shown to form corrosion products, such as Fe-oxyhydroxides (Wiersma and Subramanian 2002). Many corrosion products, including Fe-oxyhydroxides, at the high pH values of tank effluent, take on a very strong negative charge. Given that many radionuclides may have net positive charges, either as free ions or complexed species, it is expected that many radionuclides will sorb to corrosion products associated with tank liners. The objective of this report was to conduct a literature review to investigate whether Pu, U, Np, Am and Tc would sorb to corrosion products on tank liners after they were filled with reducing grout (cementitious material containing slag to promote reducing conditions). The approach was to evaluate radionuclides sorption literature with iron oxyhydroxide phases, such as hematite ({alpha}-Fe{sub 2}O{sub 3}), magnetite (Fe{sub 3}O{sub 4}), goethite ({alpha}-FeOOH) and ferrihydrite (Fe{sub 2}O{sub 3} {center_dot} 0.5H{sub 2}O). The primary interest was the sorption behavior under tank closure conditions where the tanks will be filled with reducing cementitious materials. Because there were no laboratory studies conducted using site specific experimental conditions, (e.g., high pH and HLW tank aqueous and solid phase chemical conditions), it was necessary to extend the literature review to lower pH studies and noncementitious conditions. Consequently, this report relied on existing lower pH trends, existing geochemical modeling, and experimental spectroscopic evidence conducted at lower pH levels. The scope did not include evaluating the appropriateness of K{sub d} values for the Fe-oxyhydroxides, but instead to evaluate whether it is a conservative assumption to exclude this sorption process of radionuclides onto tank liner corrosion products in the PA model. This may identify another source for PA conservatism since the modeling did not consider any sorption by the tank liner.

  1. A Review of Subsurface Behavior of Plutonium and Americium at the 200-PW-1/3/6 Operable Units

    Energy Technology Data Exchange (ETDEWEB)

    Cantrell, Kirk J.; Riley, Robert G.

    2008-01-31

    This report begins with a brief summary of the history and current status of 200-PW-1/3/6 OUs in section 2.0. This is followed by a description of our concentual model of Pu/Am migration at the 200-PW-1/3/6 OUs, during both past artificial recharge conditions and current natural recharge condictions (section 3.0). Section 4.0 discusses data gaps and information needs. The final section (section 5.0) provides recommendations for futher work to address the data gaps and information needs identified in section 4.0.

  2. Study of plutonium and americium contamination in agricultural area, radiological impact caused by consumption of vegetables of this area

    International Nuclear Information System (INIS)

    The transuranide concentration has been studied for 30 years in vegetable production, crops in wide extensions and in private-owned farms, all of them situated within the Pu-contaminated area of Palomares due to an air accident in 1966. Based on these studies, a preliminary estimation of the radiological risk caused by the consumption of these products by the inhabitants was possible. The results show that most of the fruits present a surface contamination, which disappears or is significantly reduced when they are washed. The contamination present in edible parts of the vegetables, as well as the contamination of other products included in the diet, has facilitated the estimation of the effective dose for ingestion and the committed effective dose for 50 years for the inhabitants. The main conclusions are: those plants, whose cultivation period is less than a year, present a low level of contamination; the green parts of the plants have a higher contamination than the fruits; the Pu soil to plant transfer factor is very low. In general, those plants that have remained in the contaminated land for several years present a high contamination level; the ingestion of products from Palomares does not represent an important risk for the population, even in the case that the products were totally consumed by a critical group.( author)

  3. The determination of alpha-emitting nuclides of plutonium, americium and curium in environmental materials: Pt. 1

    International Nuclear Information System (INIS)

    Within the Aquatic Environment Protection Division of the Directorate of Fisheries Research (DFR), the Radioanalytical Group routinely analyses a wide range of environmental materials for a substantial number of radionuclides. A wide variety of radiochemical procedures have been developed at different laboratories but there are no 'standard' methods because the methods are continually developing. Nevertheless, it is useful, as in this present series, periodically to draw together the methods which are in routine use at a laboratory and to discuss their development and application. (author)

  4. Studies on the binding and transport processes of americium-241 hydroxide polymers in rat lung and bovine alveolar macrophages

    International Nuclear Information System (INIS)

    The binding of Am-241 hydroxide polymers to the cell components of rat lung was investigated using differential centrifugation, density gradient centrifugation with different media, gel chromatography, free flow electrophoresis and electron microscopic autoradiography with Pu-241. The bovine alveolar macrophage cultures were introduced as an in vitro test system for Am-241 uptake. Form the biochemical and electron microscopic studies it can be concluded that Am-241 is taken up by pulmonary macrophages, where its first storage site is probably the lysosome. Then the Am-241 seems to be solubilized in the lysosomes and to be bound to the cytosolic ferritin of macrophages. Am-241 might be released from the cells and crosses the alveolar membranes as bound to transferrin or as low molecular weight form. (orig.)

  5. Oxidation-reduction properties of americium, curium, berkelium, californium, einsteinium and fermium, and thermodynamic consequences for the 5f series

    International Nuclear Information System (INIS)

    The amalgamation of 5f elements from Am to Fm has been studied by using 241Am, 244Cm, 249Bk, 249Cf, 252Cf, 253Es, 254Es, 252Fm and 255Fm with two electrochemical methods, radiocoulometry and radiopolarography, perfectly adapted to investigate extremely diluted solutions when the concentration of electroactive species is as low as 10-16M. The theory of radiocoulometry has been developed in the general cases of reversible and irreversible electrode process. It has been used to interpret the experimental data on the kinetic curves of amalgamation, and to estimate the standard rate constant of the electrode process in complexing medium (citric). On the other hand the radiopolarographic method has been applied to study the mechanism of reduction at the dropping mercury electrode of cations M3+ in aqueous medium to the metal M with formation of amalgam. The results are exploited into two directions: 1- Acquisition of some data concerning the oxidation-reduction properties of elements from Am to Fm. Therefore the standard electrode E0 [M(III-0)] potentials for Bk, Cf and Es, and the standard electrode E0 [M(II-0)] potential for Fm are estimated and the relative stability of each oxidation state (from II to VII) of 5f elements is discussed; 2- Acquisition of unknown thermodynamic data on transcalifornium elements. Correlations between 4f and 5f elements are precised and some divergences appear for the second half of 4f and 5f series (i.e. for 65<=Z<=71 and 97<=Z<=103)

  6. Effects of americium-241 and humic substances on Photobacterium phosphoreum: Bioluminescence and diffuse reflectance FTIR spectroscopic studies

    Science.gov (United States)

    Kamnev, Alexander A.; Tugarova, Anna V.; Selivanova, Maria A.; Tarantilis, Petros A.; Polissiou, Moschos G.; Kudryasheva, Nadezhda S.

    The integral bioluminescence (BL) intensity of live Photobacterium phosphoreum cells (strain 1883 IBSO), sampled at the stationary growth stage (20 h), was monitored for further 300 h in the absence (control) and presence of 241Am (an α-emitting radionuclide of a high specific activity) in the growth medium. The activity concentration of 241Am was 2 kBq l-1; [241Am] = 6.5 × 10-11 M. Parallel experiments were also performed with water-soluble humic substances (HS, 2.5 mg l-1; containing over 70% potassium humate) added to the culture medium as a possible detoxifying agent. The BL spectra of all the bacterial samples were very similar (λmax = 481 ± 3 nm; FWHM = 83 ± 3 nm) showing that 241Am (also with HS) influenced the bacterial BL system at stages prior to the formation of electronically excited states. The HS added per se virtually did not influence the integral BL intensity. In the presence of 241Am, BL was initially activated but inhibited after 180 h, while the system 241Am + HS showed an effective activation of BL up to 300 h which slowly decreased with time. Diffuse reflectance infrared Fourier transform (DRIFT) spectroscopy, applied to dry cell biomass sampled at the stationary growth phase, was used to control possible metabolic responses of the bacteria to the α-radioactivity stress (observed earlier for other bacteria under other stresses). The DRIFT spectra were all very similar showing a low content of intracellular poly-3-hydroxybutyrate (at the level of a few percent of dry biomass) and no or negligible spectroscopic changes in the presence of 241Am and/or HS. This assumes the α-radioactivity effect to be transmitted by live cells mainly to the bacterial BL enzyme system, with negligible structural or compositional changes in cellular macrocomponents at the stationary growth phase.

  7. Assessment of americium and curium transmutation in magnesia based targets in different spectral zones of an experimental accelerator driven system

    Science.gov (United States)

    Haeck, W.; Malambu, E.; Sobolev, V. P.; Aït Abderrahim, H.

    2006-06-01

    The potential to incinerate minor actinides (MA) in a sub-critical accelerator-driven system (ADS) is a subject of study in several countries where nuclear power plants are present. The performance of the MYRRHA experimental ADS, as to the transmutation of Am and Cm in the inert matrix fuel (IMF) samples consisting of 40 vol.% (Cm0.1Am0.5Pu0.4)O1.88 fuel and 60 vol.% MgO matrix with a density of 6.077 g cm-3 in three various spectrum regions, were analysed at the belgian nuclear research centre SCK · CEN. The irradiation period of 810 effective full power days (EFPD) followed by a storage period of 2 years was considered. The ALEPH code system currently under development at SCK · CEN was used to carry out this study. The total amount of MA is shown to decrease in all three considered cases. For Am, the decrease is the largest in the reflector (89% decrease) but at the cost of a net Cm production (92% increase). In the two other positions (inside the core region), 20-30% of Am has disappeared but with a lower production of Cm (between 7% and 11%). In the reflector, a significant build-up of long-lived 245Cm, 246Cm, 247Cm and 248Cm was also observed while the production of these isotopes is 10-1000 times smaller in the core. The reduction of the Pu content is also the highest in the reflector position (41%). In the other positions the incinerated amount of Pu is much smaller: 1-5%.

  8. UNDERSTANDING VARIATION IN PARTITION COEFFICIENT KD, VALUES, VOLUME III: AMERICIUM, ARSENIC, CURIUM, IODINE, NEPTUNIUM, RADIUM, AND TECHNETIUM

    Science.gov (United States)

    This report describes the conceptualization, measurement, and use of the partition (or distribution) coefficient, Kd, parameter, and the geochemical aqueous solution and sorbent properties that are most important in controlling adsorption/retardation behavior of selected contamin...

  9. Evaluation of synthetic water-soluble metal-binding polymers with ultrafiltration for selective concentration of americium and plutonium

    International Nuclear Information System (INIS)

    Water-soluble metal-binding polymers in combination with ultrafiltration are shown to be an effective method for selectively removing dilute actinide ions from acidic solutions of high ionic strength. The actinide-binding properties of commercially available water-soluble polymers and several polymers which have been reported in the literature were evaluated. The functional groups incorporated in the polymers were pyrrolidone, amine, oxime, and carboxylic, phosphonic, or sulfonic acid. The polymer containing phosphonic acid groups gave the best results with high distribution coefficients and concentration factors for 241Am(III) and 238Pu(III)/(IV) at pH 4 to 6 and ionic strengths of 0.1 to 4. (author)

  10. Salicylic acid failed to increase the efficacy of Ca-DTPA in the decorporation of plutonium and americium

    International Nuclear Information System (INIS)

    Male and female C57BL/Do mice were each given a single i.p. injection of 237+239Pu + 241Am as the citrate complex at 45 days of age. Twice weekly i.p. injecctions of either 500 μmol/kg Ca-DTPA or 500 μmol/kg Ca-DTPA, mixed just before injection with 2000 μmol/kg salicylic acid (SA), were begun 3 days after nuclide administration and continued for 5 weeks. Control mice were injected each time with isotonic saline. Nuclide retention was determined by in vivo counting using NaI(T1) spectrometry. At the end of treatment, total-body retention of Pu or Am in the mice given Ca-DTPA was significantly lower (P < 0.001) than in the control animals. Mice treated with Ca-DTPA + SA were statistically indistinguishable from mice treated with Ca-DTPA

  11. Salicylic acid failed to increase the efficacy of Ca-DTPA in the decorporation of plutonium and americium

    International Nuclear Information System (INIS)

    Male and female C57BL/Do mice were each given a single ip injection of /sup 237 + 239/Pu + 241Am as the citrate complex at 45 days of age. Twice-weekly ip injections of either 500 μmole/kg Ca-DTPA or 500 μmole/kg Ca-DTPA mixed just before injection with 2000 μmole/kg salicylic acid (SA) were begun 3 days after nuclide administration and continued for 5 weeks. Control mice were injected each time with isotonic saline. Nuclide retention was determined by in vivo γ-ray counting using a NaI(Tl) crystal spectrometer. At the end of treatment, total-body retention of Pu or Am in the mice given Ca-DTPA was significantly lower (P < 0.001) than that in the control animals. Mice treated with Ca-DTPA plus SA were statistically indistinguishable from mice treated with Ca-DTPA alone

  12. Handling of a glove box accident. Surgical treatment of a wound contaminated by a mixture of plutonium-239 and americium

    International Nuclear Information System (INIS)

    An employee of the Valduc Centre (France) suffered an injury to his right thumb when working in a glove-box on a pipeline which had contained a solution of 239Pu and Am. The lesion was slight but attempts at decontamination were fruitless. The contamination was deep-seated (activity of not less than 18nCi). DTPA was injected intravenously, and it was decided to excise the lesion surgically. Thanks to the quality of its physical facilities and the professional quality of its radiation medicine and surgery team, the Valduc Centre was able to carry out the operation successfully. The result was excellent, and the contamination was eliminated to the satisfaction of both the patient and the physician. (author)

  13. Effects of Hanford high-level waste components on the solubility and sorption of cobalt, strontium, neptunium, plutonium, and americium

    International Nuclear Information System (INIS)

    High-level radioactive defense waste solutions, originating from plutonium recovery and waste processing operations at the U.S. Department of Energy's Hanford Site, currently are stored in mild steel-lined concrete tanks located in thick sedimentary beds of sand and gravel. Statistically designed experiments were used to identify the effects of 12 major chemical components of Hanford waste solution on radionuclide solubility and sorption. The chemical components with the most effect on radioelement solubility and sorption were NaOH, NaAl0/sub 2/, EDTA, and HEDTA. The EDTA and HEDTA increased Co, Sr, and Am solubility and decreased sorption for almost all radioelements studied. Sodium hydroxide and NaAlO/sub 2/ increased Pu solubility and decreased Np and Pu sorption. Sodium nitride decreased Np solubility, while Na/sub 2/CO/sub 3/ and HEDTA increased it. These observations give evidence for the formation of radioelement complexes which are soluble and are not strongly sorbed by the sediments near the waste tanks

  14. Nano-optical single-photon response mapping of waveguide integrated molybdenum silicide (MoSi) superconducting nanowires.

    Science.gov (United States)

    Li, Jian; Kirkwood, Robert A; Baker, Luke J; Bosworth, David; Erotokritou, Kleanthis; Banerjee, Archan; Heath, Robert M; Natarajan, Chandra M; Barber, Zoe H; Sorel, Marc; Hadfield, Robert H

    2016-06-27

    We present low temperature nano-optical characterization of a silicon-on-insulator (SOI) waveguide integrated SNSPD. The SNSPD is fabricated from an amorphous Mo83Si17 thin film chosen to give excellent substrate conformity. At 350 mK, the SNSPD exhibits a uniform photoresponse under perpendicular illumination, corresponding to a maximum system detection efficiency of approximately 5% at 1550 nm wavelength. Under these conditions 10 Hz dark count rate and 51 ps full width at half maximum (FWHM) timing jitter is observed. PMID:27410555

  15. Exploration of alloy surface and slurry modification to improve oxidation life of fused silicide coated niobium alloys

    Science.gov (United States)

    Levine, S. R.; Grisaffe, S. J.

    1972-01-01

    Edge and surface modifications of niobium alloys were investigated prior to coating with Si-20Cr-20Fe and slurry composition modification for performance in a 1370 C ambient pressure slow cycle test. The best coating obtained was Si-20Cr-20Mn with an average life of 63 cycles, compared to 40 for Si-20Cr-20Fe on FS-85 (100 percent improvement in weight parity life). Edge beading extended the lives of Si-20Cr-20Fe-coated Cb-752 and FS-85 to 57 and 41 cycles respectively (50 and 20 percent improvements in weight parity life respectively). W, Al2O3 and ZrO2(CaO) surface modifications altered coating crack frequency and microstructure and increased life somewhat.

  16. Study of process of silicide coatings formation and their corrosion resistance on niobium-titanium alloy NT50

    International Nuclear Information System (INIS)

    Kinetics of NT50 niobium alloy vacuum siliconizing in the 1100-1250 deg C temperature range, structure and composition of coating are investigated. Corrosion resistance in the 1000-1400 deg C temperature range, phase composition and structure of oxidation products are studied. Durability of coatings in the 1200-1500 deg C temperature range is determined

  17. Preparation of cobalt silicide on graphene as Pt electrocatalyst supports for highly efficient and stable methanol oxidation in acidic media

    International Nuclear Information System (INIS)

    Nanostructured CoSi with the diameter of 1-3 nm on graphene have been successfully synthesized by metal organic chemical vapor deposition (MOCVD) of Co(SiCl3)(CO)4 as a precursor supported on graphene. Pt electrocatalysts are then loaded on the CoSi/graphene composites (Pt/CoSi-graphene) using an intermittent microwave heating method. The above materials are characterized by XRD, Raman, TEM, EDS and cyclic voltammograms measurements. The results show that Pt/CoSi-graphene gives 3.2 times higher peak current density than that of commercial Pt/C(TKK) electrocatalyst at the same Pt loadings. In addition, Pt/CoSi-graphene shows superior activity and stability to commercial Pt/graphene for methanol oxidationin in acidic media. The improved catalytic activity and stability is due to the synergistic effect (electron-donating) of CoSi to Pt. Since Pt/CoSi-graphene carries higher catalytic activity and stability comparing with Pt/graphene, less Pt will be required for the same performance and it will in turn reduce the cost of fuel cell electrocatalyst

  18. Silicide Induced Surface Defects in FePt nanoParticle fcc-to-fct Thermally Activated Phase Transition

    OpenAIRE

    Chen, S.; Lee, S. L.; André, P.

    2016-01-01

    Magnetic nanoparticles (MnPs) are relevant to a wide range of applications including high density information storage and magnetic resonance imaging to name but a few. Among the materials available to prepare MnPs, FePt is attracting growing attention. However, to harvest the strongest magnetic properties of FePt MnPs, a thermal annealing is often required to convert face-centered cubic as synthesized nPs into its tetragonal phase. Rarely addressed are the potential side effects of such treat...

  19. Program for in-pile qualification of high density silicide dispersion fuel at IPEN/CNEN-SP

    International Nuclear Information System (INIS)

    The development of high density nuclear fuel (U3Si2-Al) with 4,8 gU/cm3 is on going at IPEN, at this time. This fuel has been considered to be utilized at the new Brazilian Multipurpose Reactor (RMB), planned to be constructed up to 2014. As Brazil does not have hot-cell facilities available for post-irradiation analysis, an alternative qualifying program for this fuel is proposed based on the same procedures used at IPEN since 1988 for qualifying its own U3O8-Al (1,9 and 2,3 gU/cm3) and U3Si2-Al (3,0 gU/cm3) dispersion fuels. The fuel miniplates and full-size fuel elements irradiations should be tested at IEA-R1 core. The fuel characterization along the irradiation time should be made by means of non-destructive methods, including periodical visual inspections with an underwater video camera system, sipping tests for fuel elements suspected of leakage, and underwater dimensional measurements for swelling evaluation, performed inside the reactor pool. This work presents the program description for the qualification of the high density nuclear fuel (U3Si2-Al) with 4,8 gU/cm3, and describes the IPEN fuel fabrication infrastructure and some basic features of the available systems for non-destructive tests at IEA-R1 research reactor. (author)

  20. Luminescence study on solvation of americium(III), curium(III) and several lanthanide(III) ions in nonaqueous and binary mixed solvents

    International Nuclear Information System (INIS)

    The luminescence lifetimes of An(III) and Ln(III) ions [An=Am and Cm; Ln=Nd, Sm, Eu, Tb and Dy] were measured in dimethyl sulfoxide(DMSO), N,N-dimethylformamide(DMF), methanol(MeOH), water and their perdeuterated solvents. Nonradiative decay rates of the ions were in the order of H2O > MeOH > DMF > DMSO, indicating that O-H vibration is more effective quencher than C-H, C=O, and S=O vibrations in the solvent molecules. Maximal lifetime ratios τD/τH were observed for Eu(III) in H2O, for Sm(III) in MeOH and DMF, and for Sm(III) and Dy(III) in DMSO. The solvent composition in the first coordination sphere of Cm(III) and Ln(III) in binary mixed solvents was also studied by measuring the luminescence lifetime. Cm(III) and Ln(III) were preferentially solvated by DMSO in DMSO-H2O, by DMF in DMF-H2O, and by H2O in MeOH-H2O over the whole range of the solvent composition. The order of the preferential solvation, i.e., DMSO > DMF > H2O > MeOH, correlates with the relative basicity of these solvents. The Gibbs free energy of transfer of ions from water to nonaqueous solvents was further estimated from the degree of the preferential solvation. (orig.)

  1. Studies on the feasibility of using completely incinerable reagents for the single-cycle separation of americium(III) from simulated high-level liquid waste

    Energy Technology Data Exchange (ETDEWEB)

    Nayak, P.K.; Kumaresan, R.; Venkatesan, K.A.; Subramanian, G.G.S.; Prathibha, T.; Syamala, K.V.; Selvan, B. Robert; Rajeswari, S.; Antony, M.P.; Rao, P.R. Vasudeva [Indira Gandhi Centre for Atomic Research, Kalpakkam (India). Fuel Chemistry Div.; Chaurasia, Shivkumar; Bhanage, B.M. [Institute of Chemical Technology, Mumbai (India)

    2015-06-01

    The extraction and stripping behavior of various metal ions present in the fast reactor simulated high-level liquid waste (FR-SHLLW) was studied using a solvent phase composed of a neutral extractant, N,N,-didodecyl-N',N'-dioctyl-3-oxapentane-1,5-diamide (D{sup 3}DODGA) and an acidic extractant, di-2-ethylhexyl diglycolamic acid (HDEHDGA) in n-dodecane (n-DD). The third phase formation behavior of the solvent formulation D{sup 3}DODGA + HDEHDGA/n-DD, was studied when it was contacted with FR-SHLLW, and the concentration of neutral and acidic extractant needed to avoid the third phase formation was optimized. The distribution ratio of various metal ions present in FR-SHLLW was measured in a solution of 0.1 M D{sup 3}DODGA + 0.2 M HDEHDGA/n-DD. The extraction of Am(III) was accompanied by the co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Y(III), and Pd(II). A procedure was developed to minimize the extraction of unwanted metal ions by using aqueous soluble complexing agents in FR-SHLLW. Based on those results, the counter-current mixer-settler run was performed in a 20-stage mixer-settler. Quantitative extraction of Am(III), Ln(III), Y(III), and Sr(II) in 0.1 M D{sup 3}DODGA + 0.2 M HDEHDGA/n-DD was observed. The recovery of Am(III) from the loaded organic phase was carried out by the optimized aqueous formulation composed of 0.01 M diethylenetriaminepentaacetic acid (DTPA) + 0.5 M citric acid (CA) at pH 1.5. The stripping of Am(III) was accompanied by co-stripping of some early lanthanides. However the later lanthanides (Eu(III) and beyond) were not back extracted to Am(III) product. Therefore, the studies foresee the possibility of intra-lanthanides as well as lanthanide-actinide separation in a single-processing cycle.

  2. Chemical speciation of strontium, americium, and curium in high level waste: Predictive modeling of phase partitioning during tank processing. Annual progress report, October 1996--September 1997

    Energy Technology Data Exchange (ETDEWEB)

    Felmy, A.R. [Pacific Northwest National Lab., Richland, WA (US); Choppin, G. [Florida State Univ., Tallahassee, FL (US)

    1997-12-31

    'The program at Florida State University was funded to collaborate with Dr. A. Felmy (PNNL) on speciation in high level wastes and with Dr. D. Rai (PNNL) on redox of Pu under high level waste conditions. The funding provided support for 3 research associates (postdoctoral researchers) under Professor G. R. Choppin as P.I. Dr. Kath Morris from U. Manchester (Great Britain), Dr. Dean Peterman and Dr. Amy Irwin (both from U. Cincinnati) joined the laboratory in the latter part of 1996. After an initial training period to become familiar with basic actinide chemistry and radiochemical techniques, they began their research. Dr. Peterman was assigned the task of measuring Th-EDTA complexation prior to measuring Pu(IV)-EDTA complexation. These studies are associated with the speciation program with Dr. Felmy. Drs. Morris and Irwin initiated research on redox of plutonium with agents present in the Hanford Tanks as a result of radiolysis or from use in separations. The preliminary results obtained thus far are described in this report. It is expected that the rate of progress will continue to increase significantly as the researchers gain more experience with plutonium chemistry.'

  3. Experimental studies and thermodynamic modelling of volatilities of uranium, plutonium, and americium from their oxides and from their oxides interacted with ash

    Energy Technology Data Exchange (ETDEWEB)

    Krikorian, O.H.; Ebbinghaus, B.B.; Adamson, M.G.; Fontes, A.S. Jr.; Fleming, D.L.

    1993-09-15

    The purpose of this study is to identify the types and amounts of volatile gaseous species of U, Pu, and Am that are produced in the combustion chamber offgases of mixed waste oxidation processors. Primary emphasis is on the Rocky Flats Plant Fluidized Bed Incinerator. Transpiration experiments have been carried out on U{sub 3}O{sub 8}(s), U{sub 3}O{sub 8} interacted with various ash materials, PuO{sub 2}(s), PuO{sub 2} interacted with ash materials, and a 3%PuO{sub 2}/0.06%AmO{sub 2}/ash material, all in the presence of steam and oxygen, and at temperatures in the vicinity of 1,300 K. UO{sub 3}(g) and UO{sub 2}(OH){sub 2}(g) have been identified as the uranium volatile species and thermodynamic data established for them. Pu and Am are found to have very low volatilities, and carryover of Pu and Am as fine dust particulates is found to dominate over vapor transport. The authors are able to set upper limits on Pu and Am volatilities. Very little lowering of U volatility is found for U{sub 3}O{sub 8} interacted with typical ashes. However, ashes high in Na{sub 2}O (6.4 wt %) or in CaO (25 wt %) showed about an order of magnitude reduction in U volatility. Thermodynamic modeling studies were carried out that show that for aluminosilicate ash materials, it is the presence of group I and group II oxides that reduces the activity of the actinide oxides. K{sub 2}O is the most effective followed by Na{sub 2}O and CaO for common ash constituents. A more major effect in actinide activity lowering could be achieved by adding excess group I or group II oxides to exceed their interaction with the ash and lead to direct formation of alkali or alkaline earth uranates, plutonates, and americates.

  4. Sorption and diffusion of cobalt, strontium, cesium and americium in natural fissure surfaces and drill core cups studied by autoradiography, 1

    International Nuclear Information System (INIS)

    A method based on autoradiography was developed to determine the diffusion of radionuclides into the rock matrix. To investigate the diffusion the samples, which has been in contact with radioactive tracer solution up to 6 months, were splitted by sawing. From the autoradiograms of the cross sections the penetration depths of radionuclides were determined and the apparent diffusion coefficient Dsup(a) calculated. The filled and unfilled natural fissure surfaces chosen to this study were bars of drilling cores and drill core cups of tonalite, mica gneiss and rapakivi granite. After contact time of 3 months the highest penetration depths of cesium were observed for natural fissure surface sample of rapakivi granite up to 2.5 mm and of mica gneiss up to 3.7 mm. For strontium the penetration depths of 6 mm and 11 mm for unfilled and filled natural fissure samples of rapakivi granite were found. Dsup(a)-values for cesium varied between 1.5 x 10-15 and 3.2 x 10-14, for strontium between 3.5 x 10-14 and 2.1 x 10-13 m2/s. D-value obtained for cobalt (drill core cup sample, tonalite) was 5.4 x 10-17 m2/s. 241Am was only sorbed on the surface of the sample and thus no apparent diffusion coefficient could be calculated. Filling materials, chlorite and secondary minerals in tonalite and rapakivi granite increased diffusion into the mother rock. Radionuclides were sorbed both into the filling material and through fillers into the rock matrix. Cs and Sr penetrated though calcite filling material in mica gneiss into the mother rock. Calcite didn't influence on diffusion of radionuclides. Penetration depths of Cs and Sr were about the same for filled and unfilled samples

  5. Sorption and diffusion of cobalt, nickel, strontium, iodine, cesium and americium in natural fissure surfaces and drill core cups studied by autoradiography, 2

    International Nuclear Information System (INIS)

    Theoretical studies on geological disposal of radioactive waste in fractured crystalline rock and migration of radionuclides in groundwater circulating through the fractured zones have indicated the importance of diffusion into the rock matrix. Samples chosen for this study were filled and unfilled natural fracture surfaces and drill cores having a central drilled cavity ('drill core cups'). Samples originated from the two nuclear power plant sites in Finland: mica gneiss and tonalite from Olkiluoto and rapakivi granite from Haestholmen in Loviisa. An autoradiographic method was used for determination of the penetration depths and calculation of diffusion coefficients of Cs-134, Sr-90, Co-60, Ni-63, I-125 and Am-241. Emphasis was also directed to testing the quantitative autoradiographic method for diffusion coefficient measurements. After one year's contact time the penetration depths of strontium in tonalite were 15 mm and 10 mm for the filled and unfilled natural fracture surface samples and 5 mm for drill core cups. In the filled natural fracture surface sample of rapakivi granite the penetration depth of strontium was 35 mm. For cesium penetration depths in tonalite from 2.0 mm (unfilled natural surface) to 3.0 mm (drill core cup) were observed. For cobalt a penetration depth of 0.9 mm was found in the drill core cup sample of tonalite after contact time of one year and 1.5 mm in the filled natural fracture surface of rapakivi granite after contact time of six months. The range of Da-values of strontium was 1.4 x 10-14 - 1.1 x 10-13 m2/s. The Da-values for cesium and cobalt in tonalite (drill core cup samples) were 7 x 10-15 m2/s and 5 x 10-16 m2/s, respectively

  6. Sequential isotopic determination of plutonium, thorium, americium and uranium in the air filter and drinking water samples around the WIPP site

    International Nuclear Information System (INIS)

    The simultaneous determination of actinides in air filter and water samples around the WIPP site have been demonstrated. The analytical method is based on the selective separation and purification by anion exchange and Eichrome-TEVA, TRU and DGA-resin followed by determination of actinides by alpha spectrometry. Counting sources for alpha spectrometric measurements were prepared by microcoprecipitation on neodymium fluoride (NdF3). Radiochemical yields were determined using 242Pu, 229Th, 243Am and 232U as tracers. The validation of the method is performed through the analysis of reference materials or participating in laboratory intercomparison programs. The plutonium concentrations in aerosols varied seasonally, being highest in spring and summer due to the spring-time enhanced wind-storm transportation of radioactive aerosols from the stratosphere to the troposphere. The 238Pu/239+240Pu activity ratio in the aerosol samples is typically close to that of global fallout from historic above-ground nuclear weapons testing. The results presented here indicate that the source of plutonium in the WIPP environment results mainly from global nuclear fallout and there is no evidence of increases in radiological contaminants in the region that could be attributed to releases from the WIPP. (author)

  7. Americium(III) oxidation by copper(III) periodate in nitric acid solution as compared with the action of Bi(V) compounds of sodium, lithium, and potassium

    Energy Technology Data Exchange (ETDEWEB)

    Sinkov, Sergey I.; Lumetta, Gregg J. [Pacific Northwest National Laboratory, Radiochemical Processing Lab., Richland, WA (United States)

    2015-07-01

    The oxidative action of a Cu(III) periodate compound toward Am(III) in nitric acid was studied. The extent of oxidation of Am(III) to Am(VI) was investigated using a constant initial Cu(III)-to-Am(III) molar ratio of 10:1 and varying nitric acid concentrations from 0.25 to 3.5 mol/L. From 0.25 to 3 mol/L HNO3, more than 98% of the Am(III) was oxidized to Am(VI); however, at 3.5 mol/L HNO{sub 3}, the conversion to Am(VI) was only 80%. Increasing the Cu(III)-to-Am(III) molar ratio to 20:1 in 3.5 mol/L HNO{sub 3} resulted in 98% conversion to Am(VI). For comparison, oxidation of Am(III) with NaBiO{sub 3} was studied at 3.5 mol/L HNO{sub 3} and the same stoichiometric excess of Bi(V) oxidant over Am(III) (stoichiometric ratio of 3.33:1). With NaBiO{sub 3}, the extent of Am(III) conversion to Am(VI) was only 19%, while with the Cu(III) compound this value was found to be about 4 times higher under otherwise identical conditions. Similar results were obtained with other Bi(V) salts. These results show that the Cu(III) periodate compound is a superior oxidant to NaBiO{sub 3}, yielding rapid conversion to Am(VI) in a homogeneous acidic solution, and is, therefore, an excellent candidate for further development of Am separation systems.

  8. I. Nuclear Production Reaction and Chemical Isolation Procedure for Americium-240 II. New Superheavy Element Isotopes: Plutonium-242(Calcium-48,5n)(285)114

    Science.gov (United States)

    Ellison, Paul Andrew

    2011-12-01

    Part I discusses the study of a new nuclear reaction and chemical separation procedure for the production of 240Am. Thin 242Pu, natTi, and natNi targets were coincidently activated with protons from the 88-Inch Cyclotron, producing 240Am, 48V, and 57Ni, respectively. The radioactive decay of these isotopes was monitored using high-purity Ge gamma ray detectors in the weeks following irradiation. The excitation function for the 242 Pu(p, 3n)240Am nuclear reaction was measured to be lower than theoretical predictions, but high enough to be the most viable nuclear reaction for the large-scale production of 240 Am. Details of the development of a chemical separation procedure for isolating 240Am from proton-irradiated 242Pu are discussed. The separation procedure, which includes two anion exchange columns and two extraction chromatography columns, was experimentally investi- gated using tracer-level 241Am, 239Pu, and model proton-induced fission products 95Zr, 95Nb, 125Sb, and 152Eu. The separation procedure was shown to have an Am/Pu separation factor of >2x10 7 and an Am yield of ˜70%. The separation procedure was found to purify the Am sample from >99.9% of Eu, Zr, Nb, and Sb. The procedure is well suited for the processing of ˜1 gram of proton-irradiated 242Pu to produce a neutron-induced fission target consisting of tens of nanograms of 240Am. Part II describes the use of the Berkeley Gas-filled Separator at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron for the study of the 242Pu(48Ca,5n)285114 nuclear re- action. The new, neutron-deficient, superheavy element isotope 285114 was produced in 48Ca irradiations of 242Pu targets at a center-of-target beam energy of 256 MeV ( E* = 50 MeV). The alpha decay of 285114 was followed by the sequential alpha decay of four daughter nuclides, 281Cn, 277Ds, 273Hs, and 269 Sg. 265Rf was observed to decay by spontaneous fission. The measured alpha-decay Q-values were compared with those from a macroscopic-microscopic nuclear mass model to give insight into superheavy element shell effects. The 242Pu(48Ca, 5n)285114 cross section was 0.6-0.2 +1.3 pb.

  9. Methodology for the Inventory and Assessment of Americium Contamination Level in 1987 in an Area of Palomares Contaminated with Plutonium Weapon Grade

    International Nuclear Information System (INIS)

    This paper presents a methodology applied for the assessment of the ''241 Am coming from the decay of ''241 Pu isotope content in a contaminated area of Palomares, where the clean-up work done in 1966, given the negligible agricultural importance of such area at the time and its geographical characteristics, was not of the same magnitude as for the rest of the region. (Author) 4 refs

  10. DEVELOPMENT OF FUNDAMENTAL DATA ON CHEMICAL SPECIATION AND SOLUBILITY FOR STRONTIUM AND AMERICIUM IN HIGH LEVEL WASTE: PREDICTIVE MODELING OF PHASE PARTITIONING DURING TANK PROCESSING

    Science.gov (United States)

    Current strategies for reducing the total volume of radioactive tank waste requiring disposal at Hanford and other DOE sites call for the development of methods to selectively dissolve and remove non-radioactive elements such as Al, P, and Cr while retaining or precipitating the ...

  11. Studies on the feasibility of using completely incinerable reagents for the single-cycle separation of americium(III) from simulated high-level liquid waste

    International Nuclear Information System (INIS)

    The extraction and stripping behavior of various metal ions present in the fast reactor simulated high-level liquid waste (FR-SHLLW) was studied using a solvent phase composed of a neutral extractant, N,N,-didodecyl-N',N'-dioctyl-3-oxapentane-1,5-diamide (D3DODGA) and an acidic extractant, di-2-ethylhexyl diglycolamic acid (HDEHDGA) in n-dodecane (n-DD). The third phase formation behavior of the solvent formulation D3DODGA + HDEHDGA/n-DD, was studied when it was contacted with FR-SHLLW, and the concentration of neutral and acidic extractant needed to avoid the third phase formation was optimized. The distribution ratio of various metal ions present in FR-SHLLW was measured in a solution of 0.1 M D3DODGA + 0.2 M HDEHDGA/n-DD. The extraction of Am(III) was accompanied by the co-extraction of lanthanides and unwanted metal ions such as Zr(IV), Y(III), and Pd(II). A procedure was developed to minimize the extraction of unwanted metal ions by using aqueous soluble complexing agents in FR-SHLLW. Based on those results, the counter-current mixer-settler run was performed in a 20-stage mixer-settler. Quantitative extraction of Am(III), Ln(III), Y(III), and Sr(II) in 0.1 M D3DODGA + 0.2 M HDEHDGA/n-DD was observed. The recovery of Am(III) from the loaded organic phase was carried out by the optimized aqueous formulation composed of 0.01 M diethylenetriaminepentaacetic acid (DTPA) + 0.5 M citric acid (CA) at pH 1.5. The stripping of Am(III) was accompanied by co-stripping of some early lanthanides. However the later lanthanides (Eu(III) and beyond) were not back extracted to Am(III) product. Therefore, the studies foresee the possibility of intra-lanthanides as well as lanthanide-actinide separation in a single-processing cycle.

  12. Solubility limits of radionuclides in interstitial water. Americium in cement. Task 3. Characterization of radioactive waste forms. A series of final reports (1985-89). No 34

    International Nuclear Information System (INIS)

    The migration of actinides inside cement (or concrete) is very slow, even when the material is saturated with water: precipitation of actinide hydroxide explains this retention phenomenon. The aim of this work is to measure Am solubility in aqueous solutions equilibrated with CPA55 cement to: (i) compare it with thermodynamic predictions; and (ii) correlate it to (future) migration measurements of Am through cement discs. 12 figs.; 8 tabs.; 3 refs

  13. Investigation of the chemical explosion of an ion exchange resin column and resulting americium contamination of personnel in the 242-Z building, August 30, 1976

    Energy Technology Data Exchange (ETDEWEB)

    1976-10-19

    As a result of an explosion in the Waste Treatment Facility, 242-Z Building, 200 West Area of the Hanford Reservation on August 30, 1976, the Manager of the Richland Operations Office (RL), Energy Research and Development Administration (ERDA), appointed an ERDA Committee to conduct a formal investigation and to prepare a report on their findings of this occurrence. The Committee was instructed to conduct the investigation in accordance with ERDAMC 0502, insofar as circumstances would permit, to cover and explain technical elements of the casual sequence(s) of the occurrence, and to describe management systems which should have or could have prevented the occurrence. This report is the result of the investigation and presents the conclusions of the review.

  14. Separation of americium(III) and europium(III) from nitrate medium using a binary mixture of Cyanex-301 with neutral donor ligands

    International Nuclear Information System (INIS)

    Separation behaviour of Am3+ and Eu3+ was investigated from aqueous nitrate medium using a binary mixture of Cyanex-301 (bis(2,4,4- trimethylpentyl) dithiophosphinic acid) and several N, O or S donor ligands such as 1,10-phenanthroline (phen), TPTZ (2,4,6- tri(2-pyridyl)- 1,3,5- triazine), 2,2'-bipyridyl(bipy), hexa thia 18 crown 6 (S618C6), TBP (tri-n-butyl phosphate), TBTP (tri-n-butyl thiophosphate) in toluene. The S.F. values of >40,000 obtained with bipy and phen are the highest reported to date. (author)

  15. Bis(2-ethylhexyl)diglycolamic acid for the mutual separation of Europium (III) and Americium (III) from citric acid - nitric acid medium

    International Nuclear Information System (INIS)

    High-level liquid waste arises from fast reactor fuel reprocessing contains significant quantities of lanthanides and trivalent minor actinides. Recently, the partitioning of minor actinides from fast reactor-high active waste (FR-HAW) using a TRUEX solvent, composed of a solution of 0.2 M octyl(phenyl)-N,N-diisobutylcarbamoylmethylphosphine oxide (CMPO)-1.2 M tri-n-butylphosphate (TBP) in n-dodecane is demonstrated. A new stripping formulation composed of a solution of 0.1 M citric acid in 0.1 M nitric acid was employed for back extraction of trivalents from the loaded TRUEX solvent. Thus the mutual separation lanthanides and actinides requires a suitable extractant for separating them from citric acid medium

  16. The role of natural organic matter in the migration behaviour of americium in the Boom clay - Part II: analysis of migration experiments

    International Nuclear Information System (INIS)

    Full text of publication follows: In demonstrating the suitability of Boom Clay as a potential site for the disposal of radioactive waste in Belgium, the role of the relatively high amount of Natural Organic Matter (NOM) present in the Boom Clay on the mobility of critical radionuclides needs investigation. Trivalent actinides and lanthanides form strong complexes with humic substances. Complexation of these trivalent radionuclides with NOM present in the Boom Clay may have opposing effects. If complexed by the aqueous phase (mobile) NOM, radionuclide transport will be governed by the mobility of these dissolved radionuclide-NOM species. If complexed by the solid phase (immobile) NOM, migration will be retarded. One of the aims of the EC projects TRANCOM-Clay and TRANCOM-II was to investigate the role of mobile NOM as radionuclide carrier with the objective of deriving conceptual models that can be implemented in repository performance assessment (PA) models. A separate paper describes the results of column migration experiments involving the transport of 241Am-14C-NOM complexes through Boom Clay cores. This paper describes the transport model, POPCORN, that was developed to describe and evaluate the influence of NOM on radionuclide transport in clay, taking into account attachment/detachment rates of NOM to clay surfaces and the kinetics of RN complexation to, and destabilization from, NOM. The POPCORN model was used to evaluate diffusion experiments involving injection of 14C-labelled NOM in Boom Clay cores. Model fits were obtained by varying the rates of filtration of NOM by attachment to the surface of the clay matrix. POPCORN was then used to analyse the 241Am-14C-NOM migration experiments. The stability properties of the 241Am-NOM were characterised by kinetic constants, and good matches to the migration data were achieved for the experiments. The findings suggest that a small sub-population of the original 241Am-OM is the most stable, and that this sub-population has specific transport characteristics, including low dispersivity and a potential for filtering. Such characteristics may be representative of larger, more stable, but less mobile 241Am-OM complexes. In summary, the key processes governing 241Am migration are the rate of 241Am-OM destabilization and the rates of attachment and detachment of OM on the clay surfaces. Correlations between different transport parameters have been identified, and these findings offer means of extrapolating parameter values for application of the model to larger-scale problems. (authors)

  17. Aqueous complexation of citrate with neodymium(III) and americium(III): a study by potentiometry, absorption spectrophotometry, microcalorimetry, and XAFS.

    Science.gov (United States)

    Brown, M Alex; Kropf, A Jeremy; Paulenova, Alena; Gelis, Artem V

    2014-05-01

    The aqueous complexation of Nd(III) and Am(III) with anions of citrate was studied by potentiometry, absorption spectrophotometry, microcalorimetry, and X-ray absorption fine structure (XAFS). Using potentiometric titration data fitting the metal-ligand (L) complexes that were identified for Nd(III) were NdHL, NdL, NdHL2, and NdL2; a review of trivalent metal-citrate complexes is also included. Stability constants for these complexes were calculated from potentiometric and spectrophotometric titrations. Microcalorimetric results concluded that the entropy term of complex formation is much more dominant than the enthalpy. XAFS results showed a dependence in the Debye-Waller factor that indicated Nd(iii)-citrate complexation over the pH range of 1.56-6.12.

  18. Chemical speciation of strontium, americium, and curium in high level waste: Predictive modeling of phase partitioning during tank processing. Annual progress report, October 1996--September 1997

    International Nuclear Information System (INIS)

    'The program at Florida State University was funded to collaborate with Dr. A. Felmy (PNNL) on speciation in high level wastes and with Dr. D. Rai (PNNL) on redox of Pu under high level waste conditions. The funding provided support for 3 research associates (postdoctoral researchers) under Professor G. R. Choppin as P.I. Dr. Kath Morris from U. Manchester (Great Britain), Dr. Dean Peterman and Dr. Amy Irwin (both from U. Cincinnati) joined the laboratory in the latter part of 1996. After an initial training period to become familiar with basic actinide chemistry and radiochemical techniques, they began their research. Dr. Peterman was assigned the task of measuring Th-EDTA complexation prior to measuring Pu(IV)-EDTA complexation. These studies are associated with the speciation program with Dr. Felmy. Drs. Morris and Irwin initiated research on redox of plutonium with agents present in the Hanford Tanks as a result of radiolysis or from use in separations. The preliminary results obtained thus far are described in this report. It is expected that the rate of progress will continue to increase significantly as the researchers gain more experience with plutonium chemistry.'

  19. Americium, Cesium, and Plutonium Colloid-Facilitated Transport in a Groundwater/Bentonite/Fracture Fill Material System: Column Experiments and Model Results

    Science.gov (United States)

    Dittrich, T. M.; Boukhalfa, H.; Reimus, P. W.

    2014-12-01

    The objective of this study was to investigate and quantify the effects of desorption kinetics and colloid transport on radionuclides with different sorption affinities. We focused on quantifying transport mechanisms important for upscaling in time and distance. This will help determine the long-term fate and transport of radionuclides to aid in risk assessments. We selected a fractured/weathered granodiorite at the Grimsel Test Site (GTS) in Switzerland as a model crystalline rock repository system because the system has been thoroughly studied and field experiments involving radionuclides have already been conducted. Working on this system provides a unique opportunity to compare lab experiments with field-scale observations. Weathered fracture fill material (FFM) and bentonite used as backfill at the GTS were characterized (e.g., BET, SEM/EDS, QXRD), and batch and breakthrough column experiments were conducted. Solutions were prepared in synthetic groundwaters that matched the natural water chemistry. FFM samples were crushed, rinsed, sieved (150-355 μm), and equilibrated with synthetic groundwater. Bentonite was crushed, sodium-saturated, equilibrated with synthetic groundwater, and settled to yield a stable suspension. Suspensions were equilibrated with Am, Cs, or Pu. All experiments were conducted with Teflon®materials to limit sorption to system components. After radionuclide/colloid injections reached stability, radionuclide-free solutions were injected to observe the desorption and release behavior. Aliquots of effluent were measured for pH, colloid concentration, and total and dissolved radionuclides. Unanalyzed effluent from the first column was then injected through a second column of fresh material. The process was repeated for a third column and the results of all three breakthrough curves were modeled with a multi-site/multi-rate MATLAB code to elucidate the sorption rate coefficients and binding site densities of the bentonite colloids and fracture fill material. Nearly 50% of the sorbed Am was exchanged from the colloids to the fracture filling material in each of the three columns; whereas, less Cs and Pu was desorbed with each pass through a new column. Using a two-site kinetic model allowed for interrogation of desorption rates and dominant transport parameters.

  20. Uncertainty induced by chest wall thickness assessment methods on lung activity estimation for plutonium and americium: a large population-based study

    International Nuclear Information System (INIS)

    In vivo lung counting aims at assessing the retained activity in the lungs. The calibration factor relating the measured counts to the worker’s specific retained lung activity can be obtained by several means and strongly depends on the chest wall thickness. Here we compare, for 374 male nuclear workers, the activity assessed with a reference protocol, where the material equivalent chest wall thickness is known from ultrasound measurements, with two other protocols. The counting system is an array of four germanium detectors. It is found that non site-specific equations for the assessment of the chest wall thickness induce large biases in the assessment of activity. For plutonium isotopes or 241Am the proportion of workers for whom the retained activity is within ± 10% of the reference one is smaller than 10%. The use of site-specific equations raises this proportion to 20% and 58% for plutonium and 241Am, respectively. Finally, for the studied population, when site-specific equations are used for the chest wall thickness, the standard uncertainties for the lung activity are 42% and 12.5%, for plutonium and 241Am, respectively. Due to the relatively large size of the studied population, these values are a relatively robust estimate of the uncertainties due to the assessment of the chest wall thickness for the current practice at this site. (paper)

  1. The construction of TRIGA-TRAP and direct high-precision Penning trap mass measurements on rare-earth elements and americium

    OpenAIRE

    Ketelaer, J.

    2010-01-01

    Kernmassen sind eine wichtige Größe zur Untersuchung der Kernstruktur, da sie die Summe aller Wechselwirkungen im Atomkern widerspiegeln. Es gibt viele Möglichkeiten zur präzisen Massenmessung unter denen die Penningfalle die höchste Präzision erreicht. Darüber hinaus können damit absolute Massenmessungen unter Verwendung des atomaren Massenstandards Kohlenstoff als Referenz durchgeführt werden. Im Rahmen dieser Arbeit wurde das neue Doppel-Penningfallen-Massenspektrometer TRIGA-TRAP aufgebau...

  2. 用于FEA场发射微尖表面的硅化物薄膜%The Silicide Film on the Surface of FEA‘s Emission Tips

    Institute of Scientific and Technical Information of China (English)

    季旭东

    2000-01-01

    一些硅的化合物具有良好的场发射特性,如果用作FEA发射微尖表面的薄膜,将能较好地提高FEA的发射特性.本文对这一类硅化物的制作、测量与性能作了说明.

  3. Iron silicide formation at different layers of (Fe/Si){sub 3} multilayered structures determined by conversion electron Mössbauer spectroscopy

    Energy Technology Data Exchange (ETDEWEB)

    Badía-Romano, L., E-mail: lbadia@unizar.es; Bartolomé, J. [Departamento de Física de la Materia Condensada, Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, E-50009 Zaragoza (Spain); Rubín, J. [Departamento de Ciencia y Tecnología de Materiales y Fluidos, Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, E-50018 Zaragoza (Spain); Magén, C. [Laboratorio de Microscopías Avanzadas (LMA), Instituto de Nanociencia de Aragón (INA), Universidad de Zaragoza, E-50018 Zaragoza (Spain); Bürgler, D. E. [Peter Grünberg Institut (PGI-6), Forschungszentrum Jülich GmbH, D-52425 Jülich (Germany)

    2014-07-14

    The morphology and the quantitative composition of the Fe-Si interface layer forming at each Fe layer of a (Fe/Si){sub 3} multilayer have been determined by means of conversion electron Mössbauer spectroscopy (CEMS) and high-resolution transmission electron microscopy (HRTEM). For the CEMS measurements, each layer was selected by depositing the Mössbauer active {sup 57}Fe isotope with 95% enrichment. Samples with Fe layers of nominal thickness d{sub Fe} = 2.6 nm and Si spacers of d{sub Si} = 1.5 nm were prepared by thermal evaporation onto a GaAs(001) substrate with an intermediate Ag(001) buffer layer. HRTEM images showed that Si layers grow amorphous and the epitaxial growth of the Fe is good only for the first deposited layer. The CEMS spectra show that at all Fe/Si and Si/Fe interfaces a paramagnetic c-Fe{sub 1−x}Si phase is formed, which contains 16% of the nominal Fe deposited in the Fe layer. The bottom Fe layer, which is in contact with the Ag buffer, also contains α-Fe and an Fe{sub 1−x}Si{sub x} alloy that cannot be attributed to a single phase. In contrast, the other two layers only comprise an Fe{sub 1−x}Si{sub x} alloy with a Si concentration of ≃0.15, but no α-Fe.

  4. Preparation of High-Density Uranium-Silicide U3Sl2-Uss: Effects of Preirradiation Heat Treatment on As-Cast Ingot Fuel Plates

    International Nuclear Information System (INIS)

    Heat treatment experiments upon U3Si2-Uss ingot have been camed out to obtain free uranium particle size improvement which is required to enhance the U-Al inter-diffusion reaction in the fuel plate meat. . Heat treatment experiments upon fuel plates containing dispersion of U3Si2-Uss in Al matrix have also been carried out to study the effect of temperature and treatment duration on the extent of inter-diffusion reaction between free uranium particle and aluminium matrix in the fuel plate meat. Both the experiments indicate that a drastic size improvement has occurred with the U3Si2 as well as free uranium particles upon heat treatment at controlled temperature between the U3Si2 peritectic and peritectoid temperatures and that the inter-diffusion reaction between free uranium and Al matrix occurs quite significantly at temperatures higher than that ordinarily used in the fabrication procedure

  5. Interaction mechanism between niobium-silicide-based alloy melt and Y2O3 refractory crucible in vacuum induction melting process

    Directory of Open Access Journals (Sweden)

    Gao Ming

    2011-05-01

    Full Text Available The Y2O3 crucibles were introduced in the study as an alternative to the traditional ceramic ones in vacuum induction melting of multi-component Nb-16Si-22Ti-2Al-2Hf-17Cr (at.% alloys, to reveal the possible interactions between the alloy melt and the refractory crucible. Multiple melting time lengths and two cooling schemes were designed and used for the experiments. The chemical composition and microstructure of the tested alloy and the melt-crucible interaction were investigated and evaluated. In the experiments, Y2O3 crucible displays good physical-chemical compatibility. The results indicate that the increment of O element in the as-cast ingot is 0.03at.%-0.04at.% (72-97 ppm and the increment of Y element is very insignificant. The key features of the alloy melt interacting with Y2O3 ceramics are analyzed and concluded in the paper. As a result of the dissolution reaction xY2O3 (in molten alloy + (1-xHfO2 (impurity →Hf1-xY2xO2-x, a continuous double-layer solid film consisted of HfO2 solid solution (~2 μm and pure HfO2 (~5 μm is formed on the surface of the test ingot after cooled down in the crucible. The experimental results show that the Y2O3 crucible is applicable to the vacuum induction melting of Nb-Si based alloys.

  6. Doping-Spike PtSi Schottky Infrared Detectors with Extended Cutoff Wavelengths

    Science.gov (United States)

    Lin, T. L.; Park, J. S.; Gunapala, S. D.; Jones, E. W.; Castillo, H. M. Del

    1994-01-01

    A technique incorporating a p+ doping spike at the silicide/Si interface to reduce the effective Schottky barrier of the silicide infrared detectors and thus extend the cutoff wavelength has been developed.

  7. Sorption of americium(III) and europium(III) from nitric acid solutions by a novel diglycolamide-grafted silica-based resins. Pt. 2. Sorption isotherms, column and radiolytic stability studies

    Energy Technology Data Exchange (ETDEWEB)

    Ansari, Seraj A.; Mohapatra, Prasanta K. [Bahabha Atomic Research Centre, Trombay, Mumbai (India). Radiochemistry Div.; Iqbal, Mudassir; Huskens, Jurriaan; Verboom, Willem [Twente Univ. (Netherlands). Lab. of Molecular Nanofabrication

    2014-07-01

    Two novel diglycolamide-grafted silica-based resins (DGSRs) were used for the sorption of trivalent actinides and lanthanides from 3 M nitric acid solutions. The sorption of Am(III) onto the resin containing one diglycolamide (DGA) moiety (DGSR-I) was less efficient than the resin containing two DGA moieties (DGSR-II) with Lagergren first order rate constants of (1.20 ± 0.03) x 10{sup -3}s{sup -1} and (2.01 ± 0.05) x 10{sup -3}s{sup -1}, respectively. The maximum sorption of Eu(III) (used as a representative of the trivalent lanthanide/actinide ions in radioactive wastes) was 10.4 ± 1.1 mg g{sup -1} and 13.9 ± 1.3 mg g{sup -1} by the DGSR-I and DGSR-II, respectively. The sorption of Eu(III) on the grafted silica resins followed the Langmuir monolayer sorption phenomenon with sorption energies of 16.5 ± 2.05 and 17.8 ± 1.6 kJ mol{sup -1} for DGSR-I and DGSR-II, respectively. Column experiments revealed that the breakthrough capacity of Eu(III) on the DGSR-II column was higher than that on the DGSR-I column. Efficient elution could be achieved with a 0.01 M EDTA solution. The radiolytic stability of the resins was ascertained by exposing the resins to a gamma ray dose up to 1030 kGy resulting in a decrease of the K{sub d} values with about 50%; at doses <500 kGy the K{sub d} values remained unaffected.

  8. Study of plutonium and americium contamination in agricultural area, radiological impact caused by consumption of vegetables of this area; Estudio de la contaminacion de plutonio y americio en un area agricola, impacto radiologico ocasionado por consumo de vegetales contaminados

    Energy Technology Data Exchange (ETDEWEB)

    Espinosa, Assuncion; Aragon, Antonio; Cruz, Berta de la; Gutierrez, Jose [Centro de Investigaciones Energeticas Medioambientales y Tecnologicas, Madrid (Spain). Dept. de Impacto Ambiental de la Energia

    2001-07-01

    The transuranide concentration has been studied for 30 years in vegetable production, crops in wide extensions and in private-owned farms, all of them situated within the Pu-contaminated area of Palomares due to an air accident in 1966. Based on these studies, a preliminary estimation of the radiological risk caused by the consumption of these products by the inhabitants was possible. The results show that most of the fruits present a surface contamination, which disappears or is significantly reduced when they are washed. The contamination present in edible parts of the vegetables, as well as the contamination of other products included in the diet, has facilitated the estimation of the effective dose for ingestion and the committed effective dose for 50 years for the inhabitants. The main conclusions are: those plants, whose cultivation period is less than a year, present a low level of contamination; the green parts of the plants have a higher contamination than the fruits; the Pu soil to plant transfer factor is very low. In general, those plants that have remained in the contaminated land for several years present a high contamination level; the ingestion of products from Palomares does not represent an important risk for the population, even in the case that the products were totally consumed by a critical group.( author)

  9. Interaction and transport of actinides in natural clay rock with consideration of humic substances and clay organics. Characterization and quantification of the influence of clay organics on the interaction and diffusion of uranium and americium in the clay. Joint project

    Energy Technology Data Exchange (ETDEWEB)

    Bernhard, Gert [Helmholtz-Zentrum Dresden-Rossendorf e.V. (Germany). Inst. of Radiochemistry; Schmeide, Katja; Joseph, Claudia; Sachs, Susanne; Steudtner, Robin; Raditzky, Bianca; Guenther, Alix

    2011-07-01

    The objective of this project was the study of basic interaction processes in the systems actinide - clay organics - aquifer and actinide - natural clay - clay organics - aquifer. Thus, complexation, redox, sorption and diffusion studies were performed. To evaluate the influence of nitrogen, phosphorus and sulfur containing functional groups of humic acid (HA) on the complexation of actinides in comparison to carboxylic groups, the Am(III) and U(VI) complexation by model ligands was studied by UV-Vis spectroscopy and TRLFS. The results show that Am(III) is mainly coordinated via carboxylic groups, however, probably stabilized by nitrogen groups. The U(VI) complexation is dominated by carboxylic groups, whereas nitrogen and sulfur containing groups play a minor role. Phosphorus containing groups may contribute to the U(VI) complexation by HA, however, due to their low concentration in HA they play only a subordinate role compared to carboxylic groups. Applying synthetic HA with varying sulfur contents (0 to 6.9 wt.%), the role of sulfur functionalities of HA for the U(VI) complexation and Np(V) reduction was studied. The results have shown that sulfur functionalities can be involved in U(VI) humate complexation and act as redox-active sites in HA for the Np(V) reduction. However, due to the low content of sulfur in natural HA, its influence is less pronounced. In the presence of carbonate, the U(VI) complexation by HA was studied in the alkaline pH range by means of cryo-TRLFS (-120 C) and ATR FT-IR spectroscopy. The formation of the ternary UO{sub 2}(CO{sub 3}){sub 2}HA(II){sup 4-} complex was detected. The complex formation constant was determined with log {beta}{sub 0.1} M = 24.57 {+-} 0.17. For aqueous U(VI) citrate and oxalate species, luminescence emission properties were determined by cryo-TRLFS and used to determine stability constants. The existing data base could be validated. The U(VI) complexation by lactate, studied in the temperature range 7 to 65 C, was found to be endothermic and entropy-driven. In contrast, the complex stability constants determined for U(VI) humate complexation at 20 and 40 C are comparable, however, decrease at 60 C. For aqueous U(IV) citrate, succinate, mandelate and glycolate species stability constants were determined. These ligands, especially citrate, increase solubility and mobility of U(IV) in solution due to complexation. The U(VI) sorption onto crushed Opalinus Clay (OPA, Mont Terri, Switzerland) was studied in the absence and presence of HA or low molecular weight organic acids, in dependence on temperature and CO2 presence using OPA pore water as background electrolyte. Distribution coefficients (K{sub d}) were determined for the sorption of U(VI) and HA onto OPA with (0.0222 {+-} 0.0004) m{sup 3}/kg and (0.129 {+-} 0.006) m{sup 3}/kg, respectively. The U(VI) sorption is not influenced by HA ({<=}50 mg/L), however, decreased by low molecular weight organic acids ({>=} 1 x 10{sup -5} M), especially by citrate and tartrate. With increasing temperature, the U(VI) sorption increases both in the absence and in the presence of clay organics. The U(VI) diffusion in compacted OPA is not influenced by HA at 25 and 60 C. Predictions of the U(VI) diffusion show that an increase of the temperature to 60 C does not accelerate the migration of U(VI). With regard to uranium-containing waste, it is concluded that OPA is suitable as host rock for a future nuclear waste repository since OPA has a good retardation potential for U(VI). (orig.)

  10. Monitored Natural Attenuation of Inorganic Contaminants in Ground Water Volume 3 Assessment for Radionuclides IncludingTritium, Radon, Strontium, Technetium, Uranium, Iodine, Radium, Thorium, Cesium, and Plutonium-Americium

    Science.gov (United States)

    The current document represents the third volume of a set of three volumes that address the technical basis and requirements for assessing the potential applicability of MNA as part of a ground-water remedy for plumes with nonradionuclide and/or radionuclide inorganic contamina...

  11. Dy–Mn–Si as a representative of family of ‘Dy–Transition Metal–Si’ systems: Its isothermal sections, empirical rProd. Type: FTPules and new rare-earth manganese silicides

    Energy Technology Data Exchange (ETDEWEB)

    Morozkin, A.V., E-mail: morozkin@general.chem.msu.ru [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Knotko, A.V. [Department of Chemistry, Moscow State University, Leninskie Gory, House 1, Building 3, GSP-2, Moscow 119992 (Russian Federation); Yapaskurt, V.O. [Department of Petrology, Geological Faculty, Moscow State University, Leninskie Gory, Moscow 119992 (Russian Federation); Provino, A.; Manfrinetti, P. [INFM and Dipartimento di Chimica e Chimica Industriale, Universita di Genova, Via Dodecaneso 31, 16146 Genova (Italy); Yao, Jinlei; Yuan, Fang; Mozharivskyj, Y. [Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario, Canada L8S 4M1 (Canada)

    2013-10-15

    X-ray and microprobe analyses were employed for the investigation of Dy–Mn–Si system at 870/1070/1170 K. The Dy–Mn–Si system, contains the known DyMn{sub 2}Si{sub 2}, DyMnSi and Dy{sub 2}Mn{sub 3}Si{sub 5} compounds and DyMn{sub 4}Si{sub 2}, Dy{sub 2}MnSi{sub 2} and Dy{sub 3}Mn{sub 2}Si{sub 3} were new compounds identified first time and their structure are of the type TmCu{sub 4}Sb{sub 2}, Sc{sub 2}CoSi{sub 2} and Hf{sub 3}Ni{sub 2}Si{sub 3} respectively. The quasi-binary solid solutions were detected at 870/1070/1170 K: the ThMn{sub 12}-type Dy{sub 8}Mn{sub 87}Si{sub 5}, Th{sub 6}Mn{sub 23}-type Dy{sub 23}Mn{sub 72}Si{sub 5}, MgCu{sub 2}-type Dy{sub 33}Mn{sub 58}Si{sub 9} and AlB{sub 2}-type Dy{sub 38}Mn{sub 2}Si{sub 58}. The other binary compounds of the Dy–Mn–Si system do not show any visible solubility. New phases R{sub 2}MnSi{sub 2} and R{sub 3}Mn{sub 2}Si{sub 3} (R=Gd, Tb, Ho–Tm) were found out and their structure of the type Sc{sub 2}CoSi{sub 2} and Hf{sub 3}Ni{sub 2}Si{sub 3} respectively. The specific features of ‘Dy–Transition Metal–Si’ systems were discussed. - Graphical abstract: The isothermal section of Dy–Mn–Si contains the known DyMn{sub 2}Si{sub 2}, DyMnSi, Dy{sub 2}Mn{sub 3}Si{sub 5} and new TmCu{sub 4}Sb{sub 2}-type DyMn{sub 4}Si{sub 2}, Sc{sub 2}CoSi{sub 2}-type Dy{sub 2}MnSi{sub 2} and Hf{sub 3}Ni{sub 2}Si{sub 3}-type Dy{sub 3}Mn{sub 2}Si{sub 3} ternary compounds. The ternary solid solution based on the binary compounds of the Dy–Mn and Dy–Si systems: the ThMn{sub 12}-type Dy{sub 8}Mn{sub 87}Si{sub 5}, Th{sub 6}Mn{sub 23}-type Dy{sub 23}Mn{sub 72}Si{sub 5}, MgCu{sub 2}-type Dy{sub 33}Mn{sub 58}Si{sub 9} and AlB{sub 2}-type Dy{sub 38}Mn{sub 2}Si{sub 58}. The other binary compounds of the Dy–Mn–Si system do not show any visible solubility. New Sc{sub 2}CoSi{sub 2}-type R{sub 2}MnSi{sub 2} and Hf{sub 3}Ni{sub 2}Si{sub 3}-type R{sub 3}Mn{sub 2}Si{sub 3} phases were discovered for R=Gd, Tb, Ho–Tm. Display Omitted - Highlights: • The Dy–Mn–Si section contains three known and three new ternary compounds (phases). • New phase the TmCu{sub 4}Sb{sub 2}-type DyMn{sub 4}Si{sub 2} compound. • New Sc{sub 2}CoSi{sub 2}-type R{sub 2}MnSi{sub 2} and Hf{sub 3}Ni{sub 2}Si{sub 3}-type R{sub 3}Mn{sub 2}Si{sub 3} were detected for R=Gd–Tm. • Dy–Mn–Si supplements the ‘Dy–3d metal–Si’ series and leads to the ‘RT{sub m}X{sub n}’ row's rule.

  12. Phase formation and thermal stability of periodic Ni-silicide nanocontact arrays on epitaxial Si{sub 1-x}C{sub x} layers on Si(1 0 0)

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, S.L., E-mail: slcheng@ncu.edu.tw [Department of Chemical and Materials Engineering, National Central University, Chung-Li City, Taoyuan, Taiwan, ROC (China); Tseng, Y.C. [Department of Chemical and Materials Engineering, National Central University, Chung-Li City, Taoyuan, Taiwan, ROC (China); Lee, S.W. [Institute of Materials Science and Engineering, National Central University, Chung-Li City, Taoyuan, Taiwan, ROC (China); Chen, H. [Department of Chemical and Materials Engineering, National Central University, Chung-Li City, Taoyuan, Taiwan, ROC (China)

    2012-09-01

    Highlights: Black-Right-Pointing-Pointer The interfacial reactions of nanoscale Ni metal dots on single-crystal Si{sub 1-x}C{sub x}/Si(1 0 0) substrates were investigated. Black-Right-Pointing-Pointer The incorporation of C to Si substrates exhibited significant beneficial effects on improving the thermal stability of low-resistivity NiSi nanocontacts. Black-Right-Pointing-Pointer The process window of low-resistivity NiSi in the Ni nanodots/Si{sub 1-x}C{sub x}(1 0 0) sample was greatly extended by 200-250 Degree-Sign C as compared to that in the Ni nanodots/Si(1 0 0) sample. Black-Right-Pointing-Pointer Highly curled and tangled amorphous SiO{sub x} nanowires with diameters of 8-20 nm were found to form on the 900 Degree-Sign C annealed Ni nanodots/Si{sub 1-x}C{sub x}(1 0 0) samples. - Abstract: We report here on the first study of the interfacial reactions of nanoscale Ni metal dots on single-crystal Si{sub 1-x}C{sub x}(1 0 0) substrates at various heat treatments. The formation of high-resistivity NiSi{sub 2} phase was found to be more favorable for the miniature size Ni nanodots. The incorporation of C to Si substrates exhibited significant beneficial effects on improving the thermal stability of low-resistivity NiSi nanocontacts. The process window of low-resistivity NiSi in the Ni nanodots/Si{sub 1-x}C{sub x}(1 0 0) sample was greatly extended by 200-250 Degree-Sign C as compared to that in the Ni nanodots/Si(1 0 0) sample. The presence of C atoms is thought to lower the NiSi nanocontact/Si{sub 1-x}C{sub x} interface energy and/or to block the Ni diffusion paths during high temperature annealing. For the Ni nanodots/Si{sub 1-x}C{sub x}(1 0 0) sample annealed at 900 Degree-Sign C, highly curled and tangled amorphous SiO{sub x} nanowires with diameters of 8-20 nm were found to form. The growth process of these amorphous SiO{sub x} nanowires could be explained by the solid-liquid-solid (SLS) mechanism.

  13. Interface Stability and Silicide Formation in High Temperature Stable MoxSi1-x/Si Multilayer Soft X-Ray Mirrors Studied by Means of X-Ray Diffraction and HRTEM

    OpenAIRE

    Kleineberg, U.; Stock, H. J.; Kloidt, A.; Schmiedeskamp, B.; Heinzmann, Ulrich; Hopfe, S.; Scholz, R.

    1994-01-01

    Multilayer thin films consisting of alternating pure molybdenum and silicon layers with layer thicknesses of a few nanometers are of increasing interest for soft X-ray optical applications in the wavelength region above the Si-L edge [Lambda] = 12.4 nm. In order to enhance the thermal and long term stability, which is of great importance for applications with high power soft X-ray sources, interdiffusion of molybdenum and silicon as a mechanism of thermal destruction of the multilayer system ...

  14. Supported liquid inorganic membranes for nuclear waste separation

    Energy Technology Data Exchange (ETDEWEB)

    Bhave, Ramesh R; DeBusk, Melanie M; DelCul, Guillermo D; Delmau, Laetitia H; Narula, Chaitanya K

    2015-04-07

    A system and method for the extraction of americium from radioactive waste solutions. The method includes the transfer of highly oxidized americium from an acidic aqueous feed solution through an immobilized liquid membrane to an organic receiving solvent, for example tributyl phosphate. The immobilized liquid membrane includes porous support and separating layers loaded with tributyl phosphate. The extracted solution is subsequently stripped of americium and recycled at the immobilized liquid membrane as neat tributyl phosphate for the continuous extraction of americium. The sequestered americium can be used as a nuclear fuel, a nuclear fuel component or a radiation source, and the remaining constituent elements in the aqueous feed solution can be stored in glassified waste forms substantially free of americium.

  15. Calculated Atomic Volumes of the Actinide Metals

    DEFF Research Database (Denmark)

    Skriver, H.; Andersen, O. K.; Johansson, B.

    1979-01-01

    The equilibrium atomic volume is calculated for the actinide metals. It is possible to account for the localization of the 5f electrons taking place in americium.......The equilibrium atomic volume is calculated for the actinide metals. It is possible to account for the localization of the 5f electrons taking place in americium....

  16. Process for cleaning a nitric acid U/Pu-solution

    International Nuclear Information System (INIS)

    The impure starting solution is passed through a cation exchange column following oxidation of the U/Pu ions present to the hexavalent state. Here the impurities, in particular Americium, are retained and after subsequent elution are handled by known waste treatments or waste utilization (Americium). (orig.)

  17. Chemistry research and development progress report, May-October, 1978

    International Nuclear Information System (INIS)

    Work in progress includes: calorimetry and thermodynamics of nuclear materials; americium recovery and purification; optimization of the cation exchange process for recovering americium and plutonium from molten salt extraction residues, photochemical separations of actinides; advanced ion exchange materials and techniques; secondary actinide recovery; removal of plutonium from lathe coolant oil; evaluation of tributyl phosphate-impregnated sorbent for plutonium-uranium separations; plutonium recovery in advance size reduction facility; plutonium peroxide precipitation; decontamination of Rocky Flats soil; soil decontamination at other Department of Energy sites; recovery of actinides from combustible wastes; induction-heated, tilt-pour furnace; vacuum melting; determination of plutonium and americium in salts and alloys by calorimetry; plutonium peroxide precipitation process; silica removal study; a comparative study of annular and Raschig ring-filled tanks; recovery of plutonium and americium from a salt cleanup alloy; and process development for recovery of americium from vacuum melt furnace crucibles

  18. Industrial research for transmutation scenarios

    Science.gov (United States)

    Camarcat, Noel; Garzenne, Claude; Le Mer, Joël; Leroyer, Hadrien; Desroches, Estelle; Delbecq, Jean-Michel

    2011-04-01

    This article presents the results of research scenarios for americium transmutation in a 22nd century French nuclear fleet, using sodium fast breeder reactors. We benchmark the americium transmutation benefits and drawbacks with a reference case consisting of a hypothetical 60 GWe fleet of pure plutonium breeders. The fluxes in the various parts of the cycle (reactors, fabrication plants, reprocessing plants and underground disposals) are calculated using EDF's suite of codes, comparable in capabilities to those of other research facilities. We study underground thermal heat load reduction due to americium partitioning and repository area minimization. We endeavor to estimate the increased technical complexity of surface facilities to handle the americium fluxes in special fuel fabrication plants, americium fast burners, special reprocessing shops, handling equipments and transport casks between those facilities.

  19. Chemistry research and development progress report, May-October, 1978

    Energy Technology Data Exchange (ETDEWEB)

    Miner, F. J.

    1979-08-30

    Work in progress includes: calorimetry and thermodynamics of nuclear materials; americium recovery and purification; optimization of the cation exchange process for recovering americium and plutonium from molten salt extraction residues, photochemical separations of actinides; advanced ion exchange materials and techniques; secondary actinide recovery; removal of plutonium from lathe coolant oil; evaluation of tributyl phosphate-impregnated sorbent for plutonium-uranium separations; plutonium recovery in advance size reduction facility; plutonium peroxide precipitation; decontamination of Rocky Flats soil; soil decontamination at other Department of Energy sites; recovery of actinides from combustible wastes; induction-heated, tilt-pour furnace; vacuum melting; determination of plutonium and americium in salts and alloys by calorimetry; plutonium peroxide precipitation process; silica removal study; a comparative study of annular and Raschig ring-filled tanks; recovery of plutonium and americium from a salt cleanup alloy; and process development for recovery of americium from vacuum melt furnace crucibles.

  20. Processing of LEU targets for 99Mo production - Dissolution of U3Si2 targets by alkaline hydrogen peroxide

    International Nuclear Information System (INIS)

    Low-enriched uranium silicide targets designed to recover fission product 99Mo were dissolved in alkaline hydrogen peroxide (H2O2 plus NaOH) at about 90 deg. C. Sintering of matrix aluminium powder during irradiation and heat treatment retarded aluminum dissolution and prevented silicide particle dispersion. Gas evolved during dissolution is suspected to adhere to particles and block hydroxide ion contact with aluminum. Reduction of base concentrations from 5M to 0.1M NaOH yielded similar silicide dissolution and peroxide destruction rates, simplifying later processing. Future work in particle dispersion enhancement, 99Mo separation, and waste disposal is also discussed. (author)