bluuebunny/crossref_metadata_2025_split huggingface dataset:
Processes Controlling Radionuclide Release from Spent Fuel
Authors: Loida A. , Grambow B. , Geckeis H. , Dressler P. 
Published: April 2011

AbstractDissolution of spent fuel has been studied in saline, anaerobe, carbonate free solutions. Processes controlling spent fuel dissolution and associated radionuclide release are radiolytically controlled oxidative dissolution, sorption on container, solubility and coprecipitation. Upper limits for oxidative dissolution rates are given by the production rates of oxidative radiolysis products. This limitation leads to a strong decrease in surface area normalized reaction rates with increasing surface to volume ratio (S/V) and imposes geometric constraints on prediction of spent fuel behavior in a repository. Solution concentrations of Am during spent fuel corrosion were about 5 orders of magnitude lower than the solubility of Am(OH)3(s) and are likely controlled by coprecipitation. Pu concentrations may be controlled by Pu(VI) or Pu(IV) (hydr)oxides.
Uranium (iv) Dioxide and Simfuel as Chemical Analogues of Nuclear Spent Fuel Matrix Dissolution. A Comparison of Dissolution Results in a Standard Naci/NaHCO3 Solution
Authors: Bruno Jordi , Casas I. , Cera E. , de Pablo J. , GimÉnez J. , Torrero M. E. 
Published: April 2011

AbstractWe have carried out an experimental comparison study of the dissolution rates of unirradiated UO2 and SIMFUEL pellets and particles (100–300 μm) in a standard NaCI/NaHC03 solution, under oxidizing conditions. We have performed the experiments using batch and flow methodologies. Both methodologies gave similar results, indicating that the overall oxidation/dissolution process is the same in both cases. The results from the experiments indicate that under these conditions the dissolution process is both oxygen and bicarbonate promoted. The dissolution rates we obtained are: R=2.4 ± 0.8 mg U/m2 d for U02 and R= 0.17 ± 0.05 mg U/m2 d for SIMFUEL. The results of the experiments indicate that the dissolution rate under oxic conditions is clearly dependent on the number of U(VI) surface sites which for spent nuclear fuel is a function of the extent of radiolytic oxidation.
Study of Media Effect on Glass Surface
Authors: Shanggeng Luo , Zhaoguang Wu , Delu Liu 
Published: April 2011

AbstractThe present work described the effects of media, such as tuff, zeolite, bentonite and Fe2O3, on the glass surface leached in deionized water or in underground water. Element depletion or enrichment differ in different media system. No crystals were found in the leached glass surfaces layer. But there are pitting corrosion and precipitates on the leached glass surfaces. The amounts, both of them, increase along with the leaching time.
An Evaluation of Hydrogen Evolution from Corrosion of Carbon Steel in Low/Intermediate Level Waste Repositories
Authors: Matsuda Fumio , Wada Ryutaro , Fujiwara Kazuo , Fujiwara Ai 
Published: April 2011

AbstractAs a sequence of studies to evaluate the quantity of gas evolution from low/intermediate level waste repositories,hydrogen gas evoluted from corrosion of carbon steel in simulated repository environment was evaluated by laboratory experiments. The experimental results on the hydrogen gas evolution both in air purging condition simulated oxidizing environment and nitrogen purging condition simulated reducing environment, are summarized as follows.(1)Hydrogen gas evolution enough to analyze quantitavely by gas chromatography (>5ppm) has been recognized under almost all test conditions except reducing equilibrium cement water.(2)Effects of purging gas (air,nitrogen) on the hydrogen gas evolution and the corrosion rate calculated from weight loss were air purge > nitrogen purge. On the other hand, the contribution ratio of hydrogen evolution reaction in corrosion rate was nitrogen purge > air purge.(3)Effects of test solution on the hydrogen evolution rate were as fo11ows.
• Air Purge :Equilibrium Bentonite Water ≈ Equilibrium Cement Water > Synthetic Sea Watert• N2 Purge:Synthetic Sea Water > Equilibrium Bentonite Water >> Equilibrium Cement Water(4)No distinct effect of crevice geometry of test specimen on hydrogen evolution rate was recognized. Only under the reducing equilibrium cement water, however, the increase of hydrogen evolution was confirmed after the immersion of several hundred hours.(5)Hydrogen evolution rates tended to decrease with testing time except in the reducing equilibrium cement water.(6)No distinct difference of hydrogen evolution rate between steels (SPHC, SPCC) was observed.
Exafs Study of (La1-XCex)2Zr207
Authors: Yokoi Hiroto , Matsui Tsuneo , Ohno Hideo , Kobayashi Katsumi 
Published: April 2011

AbstractThe local structures around Zr atoms such as coordination number of oxygen and cations, and the Zr-0 and Zr-Ln (Ln; La, Ce) interatomic distances in the (La1-xCex).2Zr2O7 Pyrochlore compounds (X = 0–0.25), where Ce is a simulation of actinides,were studied by means of extended X-ray absorption fine structure (EXAFS) spectrometry. The local structure determined by EXAFS in this study is discussed in relation to the dissolution behavior of (La1-xCex)2Zr207 (leaching rates of Zr, La and Ce) in an acid solution (pH=1) at 363K reported previously. The difference in the local structure before and after leaching test was also investigated.
Fundamental Study on the Solidification of Radionuclides with Hydrous TiIV Oxide Modified with Either Si or Zr
Authors: Yamazaki Hiromichi , Inoue Yasushi 
Published: April 2011

AbstractThe potentiality of hydrous TiIV-Si oxide (TS) and hydrous TiIV-Zr oxide (TZ) for the selective sorption and immobilization of radioactive Co2+, Eu3+, Th4+ and UO22+ ions has been studied experimentally: The distribution coefficients and sorption capacity for these ions at various conditions in solutions, the structure and the composition of the exchangers in relevant ionic forms at high temperatures, and the leaching rates from the calcined exchangers into water and 0.01M HNO3 solution at room temperature. These results were discussed together with the results previously obtained for Cs+ and St2+, in order to evaluate the performance of TS and TZ as solidification media for radioactive liquid waste. TS takes up these cations more than TZ does in acidic solutions due to the higher acidity of the exchange site. In TZ, transition metal ions show high affinity despite the small distribution coefficients for representative metal ions. The dissolution of Co2+, Eu3+, and Th4+ is very slow from both calcined exchangers due to the crystallization of titanates of these cations. The leaching rates of Cs+, St2+ and UO22+ from calcined TS are much slower than those from TZ, indicating the formation of titanium silicate containing these cations. Based on these results, TS is considered to be superior to TZ in the sorption capacity and fixation capability of various kinds of radionuclides and is considered as a promising material for the solidification of radwaste.
Rietveld Analysis of Phase Separation in Annealed and Leach Tested Cm-Doped Perovskite
Authors: White T. J. , Mitamura H. , Tsuboi T. 
Published: April 2011

AbstractA quantitative powder X-ray diffraction study was made of actinide doped perovskite of bulk composition Ca0.98919An0.01081Ti0.98919Al0.01081O3 where An corresponded to approximately equimolar proportions of Cm-244 and Pu-240. Sections of this sample accumulated irradiation doses up to 7.51 × 1017 alpha decay events per gram (± g−1). The damaged samples were treated in two ways. First, to establish the critical temperature for structural recovery under the reducing conditions of geological repositories, isochronal annealing was carried out at 600, 800, 1000 and 1100˚C for 12 hours in graphite crucibles. Two groups of perovskites that had previously sustained doses of 4.5 × 1017 and 7.4 × 1017 ± g−1 were tested in this way. For the former group, these conditions resulted in up to 9 weight percent (wt%) of available actinide separating as a fluorite-type dioxide near the perovskite surface. In the latter group, calcium was reduced to the metal which vaporised, leaving an excess of refractory titanium that crystalised as rutile. Second, material which had sustained doses of 1.6–4.0 × 1017 alpha decays per gram was subjected to an MCC-1 leach test for two months at 90˚C using a pH ∼ 2 solution. Under these conditions surficial perovskite dissolved congruently to release calcium into solution while the titanium reprecipitated as anatase. The implications of these results for the ultimate disposal of perovskite-bearing polyphase nuclear waste ceramics are considered.
Improvement of Characteristics of Solidified Radioactive Waste Forms with Polymer-Concrete Layer
Authors: Grebenkov Alexandre J. , Trubnikov Vitaly P. , Verzhynskaja Antonina B. , Nikolajev Victor A. , Kapustina Inna B. 
Published: April 2011

AbstractWithin the framework of the Belarus National Programme, IPEP is performing research on the immobilization of low level radioactive waste after decontamination and remediation of Chernobyl Zone. The goal of the R&D programme is to develop a composite matrix for embedding these wastes using special encapsulation technology and reinforced and hydro-resisting polymer-concrete layer on solidified waste blocks to minimise the amount of cement for conditioning of waste.
Suppression of Ion-Induced Charge Collection by High-Energy B+-Implanted Layer
Authors: Kishimoto T. , Sayama H. , Takai M. , Ohno Y. , Sonoda K. , Nishimura T. , Kinomura A. , Horino Y. , Fujii K. 
Published: April 2011

AbstractControl of charge carrier collection by high-energy boron-implanted layers has been investigated to clarify the validity of buried well structures against soft errors in dynamic random-access memories (DRAMs) by ion-induced-current measurements using high-energy proton microprobes. A finely focused 1.3 MeV proton beam has been used to irradiate normal to n+p diodes with buried layers fabricated by B+ implantation at 160 — 1000 keV and to doses of 1 × 1012 — 1 × 101 ions/cm2, and reverse-biased at 1 to 5 V. The measured current was induced by carriers generated by ion microprobes. The collection of charge carriers induced by microprobe irradiation could be reduced by a buried layer formed by boron implantation. It was found that the rate of charge collection depended not on the depth but on the implantation dose of the buried layer. The carrier collection efficiency of the n+p diode with twin wells (i.e., a retrograde well) was two thirds of that with a conventional well.
Linear and Nonlinear Optical Properties of Metal Nanocluster-Silica Composites Formed by Sequential Implantation of Ag And Cu
Authors: Zuhr R.A. , Magruder.III R.H. , Anderson T.A. , Osborne D.O. 
Published: April 2011

AbstractMetal nanocluster-glass composites demonstrate unique optical properties and significant nonlinear response. In this work nanometer dimension metal colloids were formed in silica by sequential implantation of Ag and Cu ions. The Ag and Cu were implanted with relative ratios of Ag to Cu of 9:3,6:6, and 3:9 at a total nominal dose of 12xl016 ions/cm2. TEM techniques were used to examine colloid size and size distributions. The linear optical response was measured from 200 to 900 nm, while the nonlinear optical properties were measured using the z-scan technique at a wavelength of 570 nm. The linear and nonlinear optical properties were found to be dependent upon the ratio of sequentially implanted Ag to Cu and are consistent with effective medium theory.
Diffusion of Implanted Dopants and Isolation Species in III-V Nitrides
Authors: Pearton S.J. , Abernathy C.R. , Vartuli C.B. , Wilson R.G. , Zavada J.M. 
Published: April 2011

AbstractTwelve different elements used for doping or isolation were implanted into GaN, (and selected species into A1N and InN), and the resulting range parameters were measured by Secondary Ion Mass Spectrometry. For lighter elements such as Be, F and H the agreement between experimental range and range straggle dtermined using a Pearson IV computer fitting routine and those predicted by TRIM 92 calculations was good, but for heavier elements such as Ge and Se the discrepancy can be as much as a factor of two in range. There was little redistribution of any of the investigated species up to 700 °C, except for 2H in A1N and S in GaN. Elements such as F and Be which are generally rapid difiusers in III-V compounds do not display any redistribution in GaN for temperatures up to 800 °C.
Atomic Transport by Ion Beam Mixing in the Radiation Enhanced Diffusion Region
Authors: Jung S. M. , Chang G. S. , Joo J. H. , Woo J. J. , Jang K. S. , Whang C. N. 
Published: April 2011

AbstractIn order to study atomic transport in the radiation enhanced diffusion (RED) region, Pd/Co bilayers were intermixed by 80keV Ar+ in the temperature range from 90 K to 700 K. The critical temperature for the onset of RED was found to be ∼ 400 K, and the transported amount of Pd atoms was found to be always larger than that of Co in the RED region. This result cannot be explained by pre-existing models. Thus we have developed a comprehensive model for atomic transport in the RED region including size effect, damage controlled effect, and cohesive energy effect.
SiCx Layers on Diamond by Si Implantation for Protection Against High Temperature Oxidation
Authors: Kirkpatrick A.R. , Dallek S. , Kosik W.E. 
Published: April 2011

AbstractDiamond is subject to oxidation if exposed to oxygen while at temperatures above approximately 600°C. A method has been demonstrated for protection of diamond against oxidation by employing Si+ ion implantation to transform a thin surface layer into silicon carbide which exhibits excellent oxidation resistance. Integral SiCx oxidation barrier layers have been formed on diamond using high Si+ dose levels and high temperatures during implantation. SiCx layers have been characterized using Rutherford backscattering, IR spectrophotometry and scanning electron microscopy. The effects of high temperature exposure to oxygen have been examined using various oxidation test procedures including thermogravimetric analysis. SiCx layers capable of providing protection of underlying diamond for periods of several minutes at temperatures beyond 1000°C have been accomplished.
Effect of Titanium Implantation on the Mechanical Properties of Silicon Nitride
Authors: Fujihana T. , Nishimura O. , Yabe K. , Hayashi H. , Iwaki M. 
Published: April 2011

AbstractA study has been made of the chemical composition and mechanical properties of Ti+-implanted Si3N4 surface layers. Implantation of 48Ti+ was performed with doses ranging from 10 to 1017 ions cm”2 at an energy of 150 keV, and at nearly room temperature. XPS was used to analyze the depth dependence of atomic fraction and chemical bonding states of Ti+-implanted layers. The near-surface hardness was measured by a Vickers hardness tester. The friction and wear properties were measured under unlubricated conditions at room temperature using a pin on disk-plane and a block on wheel-periphery configurations, in which the pin and wheel used were AISI1045 and ASTM Wl-9, respectively. Implanted Ti-atoms formed a gaussian distribution predicted by the range theory. At the average projected range, most of Ti-atoms existed as a metallic state and TiN bonding was also formed. Oxygen and carbon were found near the surface layers. In addition to the surface peak, O-atoms accumulated in front of the average projected range of Ti. Such O-atoms formed bonds of Si-oxides and Ti-oxides. Carbon existed as a graphitic state. With increasing a Ti dose, the near-surface hardness decreased, and the wear rate increased at the running-in stage having the high friction coefficient. The steady wear attributed to the stable friction coefficient appeared after the running-in stage, although such a stable stage was not observed for unimplanted Si3N4. The mechanism for the change in mechanical properties of Si3N4 induced by Ti+-implantation will be discussed in relation to XPS characteristics.
Understanding and Controlling Transient Enhanced Dopant Diffusion in Silicon
Authors: Stolk P.A. , Gossmann H.-J. , Eaglesham D.J. , Jacobson D.C. , Luftman H.S. , Poate J.M. 
Published: April 2011

AbstractImplanted B and P dopants in Si exhibit transient enhanced diffusion (TED) during initial annealing which arises from the excess interstitials generated by the implant. In order to study the mechanisms of TED, we have used B doping marker layers in Si to probe the injection of interstitials from near-surface, non-amorphizing Si implants during annealing. The in-diffusion of interstitials is limited by trapping at impurities and has an activation energy of -3.5 eV. Substitutional C is the dominant trapping center with a binding energy of 2-2.5 eV. The high interstitial supersaturation adjacent to the implant damage drives substitutional B into metastable clusters at concentrations below the B solid solubility limit. Transmission electron microscopy shows that the interstitials driving TED are emitted from {311} defect clusters in the damage region at a rate which also exhibits an activation energy of 3.6 eV. The population of excess interstitials is strongly reduced by incorporating substitutional C in Si to levels of ∼1019/cm3 prior to ion implantation. This provides a promising method for suppressing TED, thus enabling shallow junction formation in future Si devices through dopant implantation.
Boron Enhanced Diffusion Due to High Energy Ion-Implantation and Its Suppression by Using RTA Process
Authors: ONO Atsuki , ABIKO Hitoshi , SAKAI Isarai 
Published: April 2011

AbstractSIMS measurements revealed that high energy boron-implantation causes transient enhanced diffusion (TED) of a shallow dopant profile due to Si interstitials even for a relatively low dose of ∼2E13cm-2. By systematic analysis, it is found that this anomalous diffusion is most significant in 700∼800°C annealing, and it takes place in the initial stage (less than 30sec for 800°C) of annealing. Moreover, this anomalous diffusion is more considerable than the enhanced diffusion during oxidation (OED) in practical device fabrication processes. It is found that rapid thermal annealing (RTA) at 1000-1100°C is effective for suppressing the transient enhanced diffusion and realizing a shallow channel profile for deep sub-micron devices.
Improving Wettability of PoIyMethylMetiiAcrylate by Ar+ ion Irradiation in Oxygen Environment
Authors: Koh Seok-Keun , Choi Won-Kook , Cho Jun-Sik , Song Seok-Kyun , Jung Hyung-Jin 
Published: April 2011

AbstractIon irradiation has been carried out to improve wettability of PMMA to water. The polymer was irradiated by argon and oxygen ions, and amount of ions was changed from 1014 ArVcm2 to 5xl016Ar+/cm2. Ions energies were varied from 0.5 keV to 1.5 keV, and oxygen gas was flowed from 0 seem to 6 scan near the polymer surface during ion irradiation. Wetting angle was reduced from 68 degree to 49 degree with increasing Ar+ ion irradiation, to 43 degree with Ch+ ion irradiation, and dropped to 8 degree with Ar+ ion irradiation with flowing 4 seem oxygen gas near the polymer surface. Recovery of wettability in dry air condition, and maintenance of it in dilute HC1 solution were explained in a view of formation of hydrophilic groups due to a reaction between irradiated polymer chain by energetic ion irradiation and flowing oxygen near the surface. Reactions among polymer matrix, energetic ions and oxygen gas to form hydrophilic group by energetic ions were discussed in terms of a two-step reaction, in which the first step is the creation of an unstable polymer chain by the ion irradiation and the second step is a reaction between the radicals and the oxygen gas.
Trace Contamination Measurements Using Heavy Ion Backscattering Spectrometry
Authors: Knapp J.A. , Banks J.C. , Brice D.K. 
Published: April 2011

AbstractHeavy Ion Backscattering Spectrometry (HIBS) is a tool for measuring surface contamination at levels much lower than previously achievable with ion beam analyses. Many areas of materials research and development require very low levels of impurities, with advanced microelectronics as the best example. HIBS uses low-energy, heavy ions for analysis, taking advantage of the increased backscattering yield which can be obtained from high Z ion beams at low energy. Background due to increased yield from the substrate is eliminated by a thin carbon foil as part of the detector, with a thickness chosen to range out ions scattered from the substrate and allow only ions scattered from impurities heavier than the substrate to reach the detector. Our research system, using 150-200 keV N+ beams and a single time-of-flight detector optimized for large solid angle, has achieved a sensitivity ranging from ∼5×1010 atoms/cm2 for Fe to ∼1×109 atoms/cm for Au on Si, without preconcentration. A stand-alone HIBS prototype which we have developed for SEMATECH is expected to reach detection limits of -5×10 atoms/cm for Fe and -1×10 atoms/cm for Au on Si. In this paper we discuss in detail the factors which affect sensitivity for HIBS.
High Resolution Tem Study of Diamond Formation on Silicon and Molybdenum Field Emitter Surfaces
Authors: Myers A. F. , Liu J. , Choi W. B. , Wojak G. J. , Hren J. J. 
Published: April 2011

AbstractDiamond is an attractive material for coating microfabricated metal and semiconductor field emitters, since it enhances the stability and emission characteristics of the emitter. In the present study, polycrystalline diamond thin films were grown on silicon and molybdenum field emitters by microwave plasma chemical vapor deposition, using the bias-enhanced nucleation technique. High resolution transmission electron microscopy (TEM) was used to analyze the morphology of the diamond film and the structure of the diamond/emitter interface. Electron diffraction patterns and high resolution images indicate the presence of a polycrystalline diamond film, as well as a polycrystalline SiC layer between the diamond film and the Si emitter. A carbide interlayer was also found to exist between the diamond and the Mo emitter surface. Parallel electron energy loss spectroscopy confirms the TEM identification of a polycrystalline diamond film.
Microstructural evolution during ion beam assisted Deposition
Authors: Hubler Graham K. 
Published: April 2011

AbstractThe advantages of energetic deposition are low temperature processing, oriented or single crystal films, high phase purity, high density and good adhesion to substrates. The time and spatial scales over which the atoms arrange themselves on a surface are not easy accessed experimentally. Therefore, these advantages are customarily verified by ex-situ examination of films after deposition is complete, which gives little information on atomic scale processes that lead to the listed advantages. The addition of energy to the deposition flux effects surface processes that are otherwise only controllable by changing the substrate temperature. Thus, understanding the mechanisms by which energetic atoms alter surface processes in analogy with thermal effects is of paramount interest for optimization of the deposition parameters. This review summarizes the state of knowledge on the effects of energetic ions on film formation. For high quality, defect free films, the energy must be controlled in the energy region of 5 eV to 30 eV. Below about 5 eV, the energy is ineffective for changing the physical processes, and above about 30 eV, defects are added to the film by displacement damage that cannot anneal out due to low temperature of the deposition. Models for the composition and chemistry of films energetically deposited are progressing well, while models for prediction of the phases that form are almost nonexistent. Molecular dynamics provide the best information, but only a handful of cases have been simulated.