Characterization and Leaching Behavior of Plutonium-Bearing Synroc-C

1996 ◽  
Vol 465 ◽  
Author(s):  
Katherine L. Smith ◽  
Gregory R. Lumpkin ◽  
Mark G. Blackford ◽  
Michelle Hambley ◽  
R. Arthur Day ◽  
...  
Keyword(s):  
Vessel Wall ◽  
Starting Material ◽  
Secondary Phases ◽  
Leaching Behavior ◽  
Leach Rate

ABSTRACTSynroc-C containing 10wt% simulated PW-4b-D HLW including 0.62 wt% 239Pu was subjected to MCC-1 type leach tests at 70°C in deionised water, silicate and carbonate leachates for 53 d and deionised water for 2472 d. The normalised total (i.e. unfiltered leachate + vessel wall) Pu leach rates in deionised water, silicate and carbonate leachates for periods up to 53 d were found to be of the order of 10-5, 10-4 and 10-4 g m-2 d-1 respectively. After 2472 d, the differential, normalised, Pu leach rate in deionised water dropped to ∼5 × 10-6 (total) and ∼5 × 10-8 (solution - after filtration through a 1000NMW filter) g m-2 d-1. SEM and AEM were used to characterise our starting material and investigate the secondary phases on the surfaces of leached Synroc-C discs. Calculated and measured normalised Pu leach rates are compared and the partitioning of Pu between zirconolite and perovskite is discussed.

scholarly journals Reaction Layer Analysis of In Situ Reinforced Titanium Composites: Influence of the Starting Material Composition on the Mechanical Properties

Metals ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 265
Author(s):  
Isabel Montealegre-Meléndez ◽  
Cristina Arévalo ◽  
Ana M. Beltrán ◽  
Michael Kitzmantel ◽  
Erich Neubauer ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Reaction Layer ◽  
Processing Parameters ◽  
Starting Material ◽  
Secondary Phases ◽  
Layer Analysis ◽  
The Matrix ◽  
B4c Particles ◽  
Al Powder

This study aims at the analysis of the reaction layer between titanium matrices and reinforcements: B4C particles and/or intermetallic TixAly. Likewise, the importance of these reactions was observed; this was particularly noteworthy as regard coherence with the obtained results and the parameters tested. Accordingly, five starting material compositions were studied under identical processing parameters via inductive hot pressing at 1100 °C for 5 min in vacuum conditions. The results revealed how the intermetallics limited the formation of secondary phases (TiC and TiB) created from the B and C source. In this respect, the percentages of TiB and TiC slightly varied when the intermetallic was included in the matrix as prealloyed particles. On the contrary, if the intermetallics appeared in situ by the addition of Ti-Al powder in the starting blend, their content was lesser. The mechanical properties values and the tribology behaviour might deviate, depending on the percentage of the secondary phases formed and its distribution in the matrix.

Fabrication of Low Temperature Carbonated Hydroxyapatite Porous Scaffolds for Bone Tissue Engineering Applications

2019 ◽  
Vol 829 ◽  
pp. 167-172
Author(s):  
Muhammad Syazwan Mohd Noor ◽  
Ahmad Fauzi Mohd Noor ◽  
Yanny Marliana Baba Ismail
Keyword(s):  
Single Phase ◽  
Three Dimensional ◽  
Starting Material ◽  
Porous Scaffolds ◽  
Secondary Phases ◽  
Phase Purity ◽  
Carbonated Hydroxyapatite ◽  
Structure Phase ◽  
Replication Technique ◽  
Main Component

Three-dimensional (3D) porous carbonated hydroxyapatite (CHA) scaffolds were successfully prepared using polyurethane (PU) replication technique. Two sets of porous scaffolds were prepared using as-synthesized and as-calcined CHA powder as the main component of the slurry. The effect of the condition of starting material was investigated in terms of structure, phase purity, crystallinity and morphology of the fabricated porous scaffolds. Regardless of the condition of starting material used, the porous scaffolds fabricated was single phase B-type CHA and free of secondary phases. Interestingly, scaffolds made of as-calcined CHA powder (SC scaffolds) showed a smoother surface and more solidified struts when compared to as-synthesized CHA powder (SA scaffolds). This is attributed to the state of semi-crystalline phase of the as-calcined powder being amorphous phase. SC scaffold was found to be better scaffold with respect to handling, compaction strength and microstructure with better strut properties.

Enhancement of thermal conductivity in ceramics obtained from a combustion synthesized AlN powder by microwave sintering and reheating

2008 ◽  
Vol 23 (3) ◽  
pp. 819-827 ◽  
Author(s):  
Shyan-Lung Chung ◽  
Cheng-Yu Hsieh ◽  
Chih-Wei Chang
Keyword(s):  
Thermal Conductivity ◽  
Oxygen Content ◽  
Microwave Sintering ◽  
Starting Material ◽  
High Thermal Conductivity ◽  
Secondary Phases ◽  
Soaking Time ◽  
Low Thermal Conductivity ◽  
Carbon Particles ◽  
Reducing Atmosphere

A combustion-synthesized AlN powder was investigated for use as a starting material in obtaining a high thermal conductivity AlN by microwave sintering followed by microwave reheating under a reducing atmosphere. Microwave sintering was found to proceed very quickly so that a density of 99.5% of theoretical with a thermal conductivity of 165 W/mK was achieved after sintering at 1900 °C for 5 min. The thermal conductivity could be improved by prolonging the soaking time, which is attributed to decreases in both oxygen content and secondary phases by evaporation and sublimation of the secondary phases. The reducing atmosphere was created by adding carbon particles to the AlN packing powder surrounding the specimen. The thermal conductivity could be significantly improved by microwave reheating of the sintered specimen under the reducing atmosphere. This is considered to be due to enhanced removal of the secondary phases by the reducing atmosphere. Sintering under the reducing atmosphere was found to retard densification because of the earlier removal of the secondary phases, thus resulting in a poor densification and a low thermal conductivity.

Role of Surface Layers in the Leaching Behavior of Glass

1988 ◽  
Vol 125 ◽  
Author(s):  
B.K. Zoitos ◽  
D.E. Clark
Keyword(s):  
Surface Layer ◽  
Nuclear Waste ◽  
Surface Composition ◽  
Analytical Techniques ◽  
Surface Layers ◽  
Leaching Behavior ◽  
Leach Rate ◽  
Layer Analysis ◽  
Nuclear Waste Glass

ABSTRACTResults are presented from a two-year dynamic leach test of nuclear waste glass under conditions designed to simulate those of the Stripa granite repository. Solution and surface analytical techniques were used to assess the glass leach rate as well as surface composition and morphology. Glass leach rates were observed to decrease by a factor of two during the first six months. This effect is attributed to the formation of a protective surface layer. Analysis of this layer shows it to be rich in silicon and iron and depleted in lithium, sodium and boron. It was also found that the layer is subject to dissolution.

The Leaching Behavior of Bituminized Radioactive Waste in the Geologic Disposal Conditions of the Boom Clay Formation

1997 ◽  
Vol 506 ◽  
Author(s):  
A. Sneyers ◽  
P. Van Iseghem
Keyword(s):  
Radioactive Waste ◽  
Crack Formation ◽  
Soluble Salts ◽  
Leaching Behavior ◽  
Boom Clay ◽  
Leach Rate ◽  
Diffusion Controlled ◽  
Geologic Disposal ◽  
Leaching Behaviour ◽  
Clay Formation

ABSTRACTAs part of the evaluation of the safety of geologic disposal, the leaching behaviour of two types of bituminized radioactive waste (Eurobitum and CEA bitumen) has been studied as a function of temperature, pressure, leachant composition and bitumen matrix type. Inactive and active bitumen samples were brought into contact with two test media, simulating the geologic disposal environment of the Boom clay formation. At contact with these media, the samples swelled and soluble salts and radionucides were leached. It was found that the leach rate is influenced by temperature, the leachant composition, and the physical characteristics of the bitumen matrix. The release of nitrate is interpreted as a diffusion controlled process, which can however be disturbed by crack formation. The leaching of 60Co, 90Sr, and total β is diffusion controlled. Low leach rates were measured for Pu and Am: the release of Pu and Am is limited by their solubility in the leachant. Pu and Am are preferentially sorbed to the Boom clay, the test container or the bitumen. The leached mobile Pu and Am concentrations are of the order of 10−10 to 1013 M at 23°C. The results of this study suggest that the integrity of bituminized waste packages is seriously affected due to the leaching of soluble salts: a full-size 220 litre Eurobitum drum is predicted to be depleted in NaNO3 in less than 20,000 years.

scholarly journals Preparation and Study of Corrosion Behavior of Some Simulated Radioactive Waste Glasses

2019 ◽  
Vol 16 (3) ◽  
pp. 271-279
Author(s):  
Patit Paban Malik
Keyword(s):  
Radioactive Waste ◽  
Ground Water ◽  
Corrosion Behavior ◽  
Iron Phosphate ◽  
Leaching Behavior ◽  
Time Intervals ◽  
Safe Environment ◽  
Leach Rate ◽  
Weight Losses ◽  
Leachate Solution

To safe environment from radioactive waste it is important to fix them as radioactive waste glasses. The corrosion behavior of radioactive waste glasses in water is significantly important. Radionuclides return to the biosphere by means of leaching from waste form into ground water. Finally the ground water containing the radionuclide are transported to the surface. In this study, the preparation, characterization and leaching behavior of some borosilicate (BS) and lead iron phosphate (LIP) of different chemical composition doped with simulated nuclear waste oxide were investigated. We measured the pH found to be in the range from 6.78 up to 7.79 of the leachate solution at normal temperature and at varying time intervals. Leaching study of these glasses were conducted with the help of Soxhlet distillation apparatus with distilled water upto 24 hours and for BS9 - BS12 upto 100 hours duration. Weight losses were are measured with respect to time of leaching. Leach rate of some borosilicate glass samples loaded with uranium are calculated from surface area measurements. The results are reported in the range 1.34x10-4 g.m-2.hr-1 and 6.26 x 10-4 g.m-2.hr-1 respectively at 90°C.

Electron Energy Analysis of Germanium and Silica Layers on Silicon Substrates

1975 ◽  
Vol 33 ◽  
pp. 96-97
Author(s):  
R. W. Ditchfield ◽  
A. G. Cullis
Keyword(s):  
Epitaxial Growth ◽  
Electron Energy ◽  
Silicon Substrates ◽  
Secondary Phases ◽  
Si Substrates ◽  
Transmission Electron ◽  
Layer Structures ◽  
Si Films ◽  
Electron Energy Loss ◽  
Growth Centres

An energy analyzing transmission electron microscope of the Möllenstedt type was used to measure the electron energy loss spectra given by various layer structures to a spatial resolution of 100Å. The technique is an important, method of microanalysis and has been used to identify secondary phases in alloys and impurity particles incorporated into epitaxial Si films.Layers Formed by the Epitaxial Growth of Ge on Si Substrates Following studies of the epitaxial growth of Ge on (111) Si substrates by vacuum evaporation, it was important to investigate the possible mixing of these two elements in the grown layers. These layers consisted of separate growth centres which were often triangular and oriented in the same sense, as shown in Fig. 1.

Characterization of lead-bearing phases in municipal waste combustor fly ash

1996 ◽  
Vol 54 ◽  
pp. 516-517
Author(s):  
L. L. Sutter ◽  
G. R. Dewey ◽  
J. F. Sandell
Keyword(s):  
Fly Ash ◽  
Bottom Ash ◽  
Municipal Waste ◽  
Primary Concern ◽  
Leaching Behavior ◽  
Waste Combustion ◽  
Lead And Cadmium ◽  
Lead Speciation ◽  
Accepted Practice

Municipal waste combustion typically involves both energy recovery as well as volume reduction of municipal solid waste prior to landfilling. However, due to environmental concerns, municipal waste combustion (MWC) has not been a widely accepted practice. A primary concern is the leaching behavior of MWC ash when it is stored in a landfill. The ash consists of a finely divided fly ash fraction (10% by volume) and a coarser bottom ash (90% by volume). Typically, MWC fly ash fails tests used to evaluate leaching behavior due to high amounts of soluble lead and cadmium species. The focus of this study was to identify specific lead bearing phases in MWC fly ash. Detailed information regarding lead speciation is necessary to completely understand the leaching behavior of MWC ash.

The molecular mechanism of mechanotransduction in vascular homeostasis and disease

2020 ◽  
Vol 134 (17) ◽  
pp. 2399-2418
Author(s):  
Yoshito Yamashiro ◽  
Hiromi Yanagisawa
Keyword(s):  
Shear Stress ◽  
Blood Vessels ◽  
Vessel Wall ◽  
Vascular Diseases ◽  
Cell Interactions ◽  
Aortic Aneurysms ◽  
Cyclic Stretch ◽  
Mechanical Stimuli ◽  
Vascular Homeostasis ◽  
Matrix Cell

Abstract Blood vessels are constantly exposed to mechanical stimuli such as shear stress due to flow and pulsatile stretch. The extracellular matrix maintains the structural integrity of the vessel wall and coordinates with a dynamic mechanical environment to provide cues to initiate intracellular signaling pathway(s), thereby changing cellular behaviors and functions. However, the precise role of matrix–cell interactions involved in mechanotransduction during vascular homeostasis and disease development remains to be fully determined. In this review, we introduce hemodynamics forces in blood vessels and the initial sensors of mechanical stimuli, including cell–cell junctional molecules, G-protein-coupled receptors (GPCRs), multiple ion channels, and a variety of small GTPases. We then highlight the molecular mechanotransduction events in the vessel wall triggered by laminar shear stress (LSS) and disturbed shear stress (DSS) on vascular endothelial cells (ECs), and cyclic stretch in ECs and vascular smooth muscle cells (SMCs)—both of which activate several key transcription factors. Finally, we provide a recent overview of matrix–cell interactions and mechanotransduction centered on fibronectin in ECs and thrombospondin-1 in SMCs. The results of this review suggest that abnormal mechanical cues or altered responses to mechanical stimuli in EC and SMCs serve as the molecular basis of vascular diseases such as atherosclerosis, hypertension and aortic aneurysms. Collecting evidence and advancing knowledge on the mechanotransduction in the vessel wall can lead to a new direction of therapeutic interventions for vascular diseases.

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