Long-Term Redistribution of Residual Gas Due to Non-convective Transport in the Aqueous Phase

2021 ◽  
Author(s):  
Yaxin Li ◽  
Franklin M. Orr ◽  
Sally M. Benson
Keyword(s):  
Aqueous Phase ◽  
Convective Transport ◽  
Residual Gas

Single Idealized Cracks: A Tool for Understanding Fractured Glass Block Leaching

2008 ◽  
Vol 1107 ◽  
Author(s):  
Laure Chomat ◽  
Frédéric Bouyer ◽  
Stéphane Gin ◽  
Stéphane Roux
Keyword(s):  
Molecular Diffusion ◽  
Convective Transport ◽  
Glass Block ◽  
Transport Mechanisms ◽  
Realistic Condition ◽  
Glass Model ◽  
Gravity Driven ◽  
Original Device ◽  
Glass Leaching

AbstractWithin the scope of the long term behaviour of the R7T7 glass, which is the French nuclear glass, leaching and its coupling with transport mechanisms is studied. Experiments carried out on a SON 68 glass (inactive R7T7 type glass) model cracks in static basic conditions show a strong coupling between solution transport and glass leaching, depending on crack aperture. Moreover, gravity driven convective transport was evidenced for vertical model cracks, whereas only molecular diffusion was detected for horizontal model cracks under the same alteration conditions. In addition, an original device was developed to study the influence of temperature gradients on alteration kinetics as a convective driving force. These experiments show conclusively that thermally- or gravity-induced convective flow must be taken into account, even if such convective effects have not been established experimentally in neutral condition, which is more realistic condition for geological storage. A modeling, based on a porous geochemical software (HYTEC) accounting for both chemistry and transport, has been successfully applied to describe alteration within simple silicate glass cracks. It will be extended to study SON 68 glass model cracks, and more complex fracture networks.

The Potential Impact of Oil and Other Non-Aqueous Phase Liquids (NAPLs) on the Long-Term Management of Radioactive Wastes

2003 ◽  
Author(s):  
M. M. Askarieh ◽  
A. W. Harris ◽  
S. J. Wisbey
Keyword(s):  
Waste Management ◽  
Aqueous Phase ◽  
Organic Materials ◽  
Near Field ◽  
Radioactive Wastes ◽  
Assessment Tools ◽  
The United Kingdom ◽  
The Impact ◽  
Term Management

The presence of non-aqueous phase liquids (NAPLs) in radioactive wastes has the potential to adversely affect their long-term management. The buoyancy of light NAPLs can represent a separate pathway for their migration from a waste management facility, such as a deep repository, to the accessible environment. Their inherent toxicity and potential burden of radionuclides need to be addressed. Nirex is currently developing an understanding of the behaviour of NAPLs and exploring the means of mitigating any adverse impact. NAPLs such as oils and solvents are present in existing wastes, but NAPLs can also be generated by degradation of some solid organic materials, such as plastics. Wastes arising in the United Kingdom that may contain NAPLs include liquids and sludges contaminated with oils, and waste items containing trapped oil, for example gearboxes and pumps. The reference inventory being assessed by Nirex also contains significant quantities of organic materials which can be considered to be potential precursors to the generation of NAPLs. A programme of work has been instigated by Nirex to develop a better understanding of the behaviour of NAPLs. The programme includes the following aspects: understanding the mechanisms by which NAPLs might be produced and existing NAPLs degraded and destroyed: • consideration of the containment that could be offered by packaging of wastes containing NAPLs; • investigating the extent to which radionuclides may be entrained in NAPLs; • understanding the migration of NAPLs in the near-field and in geological systems; • the impact of NAPLs on the surface properties of repository backfill and the geosphere; • development of assessment tools to quantify the potential risk due to NAPLs. This paper will describe the scope of this programme of work, and will provide examples from the ongoing programme to demonstrate that suitable long-term waste management solutions can be developed for NAPL containing wastes.

scholarly journals Neptunium(V) and Uranium(VI) Reactions at the Magnetite (111) Surface

Geosciences ◽  
2019 ◽  
Vol 9 (2) ◽  
pp. 81 ◽  
Author(s):  
Pieter Bots ◽  
Arjen van Veelen ◽  
J. Frederick W. Mosselmans ◽  
Christopher Muryn ◽  
Roy A. Wogelius ◽  
...  
Keyword(s):  
Aqueous Phase ◽  
Fuel Cycle ◽  
Grazing Incidence ◽  
Surface Complexes ◽  
Environmental Behaviour ◽  
Remediation Strategies ◽  
Icp Ms ◽  
Vis Spectroscopy ◽  
Before And After

Neptunium and uranium are important radionuclides in many aspects of the nuclear fuel cycle and are often present in radioactive wastes which require long term management. Understanding the environmental behaviour and mobility of these actinides is essential in underpinning remediation strategies and safety assessments for wastes containing these radionuclides. By combining state-of-the-art X-ray techniques (synchrotron-based Grazing Incidence XAS, and XPS) with wet chemistry techniques (ICP-MS, liquid scintillation counting and UV-Vis spectroscopy), we determined that contrary to uranium(VI), neptunium(V) interaction with magnetite is not significantly affected by the presence of bicarbonate. Uranium interactions with a magnetite surface resulted in XAS and XPS signals dominated by surface complexes of U(VI), while neptunium on the surface of magnetite was dominated by Np(IV) species. UV-Vis spectroscopy on the aqueous Np(V) species before and after interaction with magnetite showed different speciation due to the presence of carbonate. Interestingly, in the presence of bicarbonate after equilibration with magnetite, an unknown aqueous NpO2+ species was detected using UV-Vis spectroscopy, which we postulate is a ternary complex of Np(V) with carbonate and (likely) an iron species. Regardless, the Np speciation in the aqueous phase (Np(V)) and on the magnetite (111) surfaces (Np(IV)) indicate that with and without bicarbonate the interaction of Np(V) with magnetite proceeds via a surface mediated reduction mechanism. Overall, the results presented highlight the differences between uranium and neptunium interaction with magnetite, and reaffirm the potential importance of bicarbonate present in the aqueous phase.

Transmembranous Transport and Adsorption of Beta-2-microglobulin during Hemodialysis using Polysulfone, polyacrylonitrile, polymethylmethacrylate and Cuprammonium Rayon Membranes

1989 ◽  
Vol 12 (11) ◽  
pp. 697-702 ◽  
Author(s):  
B. Klinke ◽  
A. Röckel ◽  
S. Abdelhamid ◽  
P. Fiegel ◽  
D. Walb
Keyword(s):  
Causative Agent ◽  
Membrane Surface ◽  
Convective Transport ◽  
High Flux ◽  
Total Removal ◽  
Hemodialysis Session ◽  
Beta 2 ◽  
Beta 2 Microglobulin ◽  
Total Elimination

Beta-2-microglobulin (b2M) was identified as a causative agent of amyloidosis associated with long-term hemodialysis (HD). Therefore, we examined handling of b2M during a 4-hour hemodialysis session. We compared b2M adsoprtion and diffusive/convective elimination between high-flux membranes such as polysulfone (PS; F 60®, Fresenius), polyacrylonitrile (AN 69; FiltralR, Hospal) and polyacrylonitrile (PAN, PAN 12CX2R, Asahi) and less permeable membranes such as cuprammonium rayon (CR; AM 160 HR, Asahi) and polymethylmethacrylate (PMMA; BK-1.6 UR, Toray). To calculate total elimination, arterio-venous differences of b2M were measured at 0, 5, 20, 60 and 240 minutes; dialysate concentration was analyzed to evaluate diffusive/convective transport. Differences between recovery in dialysate and total removal were regarded as amount removed by adsorption. Total elimination per 4-hour hemodialysis session and per m2 membrane surface was 154.7 ± 12.3 mg for the PS, 137.8 ± 28.4 mg for the AN 69, 179.8 ± 47.5 mg for the PAN, 130.8 ± 11.8 mg for the PMMA and 14.4 ± 16.0 mg for the CR membrane. Diffusive/convective transport was 128.0 ± 18.1 mg for PS, 54.7 ± 8.1 mg for AN 69 and 106.5 ± 20.8 mg for PAN and insignificant for PMMA and CR. Adsorption was 26.7 ± 4.3 mg for PS, 83.1 ± 29.0 mg for AN 69 and 59.8 ± 17.2 mg for PAN. Besides transmembranous transport sorption is an important mode of elimination. Weekly endogenous generation rate is about twice as high as b2M elimination

Migration of viscous non-aqueous phase liquids (NAPLs) in alluvium, Fraser River lowlands, British Columbia

2006 ◽  
Vol 43 (7) ◽  
pp. 694-703 ◽  
Author(s):  
Richard E Jackson ◽  
Varadarajan Dwarakanath ◽  
John E Ewing ◽  
John Avis
Keyword(s):  
British Columbia ◽  
Aqueous Phase ◽  
Coal Tar ◽  
Chlorinated Solvents ◽  
Creeping Flow ◽  
Fraser River ◽  
Manufactured Gas Plants ◽  
A Site ◽  
Gas Plants

Coal tar, creosote, and similar viscous non-aqueous phase liquids (NAPLs) behave in alluvial soils in a manner significantly different from that of less viscous NAPLs, such as gasoline and chlorinated solvents. Their unique behavior is due to the interaction of their physical–chemical parameters: a density often greater than water, a viscosity significantly greater than water, and an interfacial tension that yields a positive initial spreading coefficient at air–water–NAPL interfaces. This results in slow, creeping flow that causes long-term contamination at former manufactured gas plants and wood-preserving sites and of their adjacent surface waters. Multiphase simulations of this creeping flow are shown for a site along the lower Fraser River near Vancouver, British Columbia, and the long-term consequences of the migration of viscous NAPLs in alluvium are discussed from the perspective of site characterization and brownfields redevelopment.Key words: creosote, coal tar, multiphase simulation, brownfields, NAPL.

Cost-effective aqueous-phase synthesis of long copper nanowires

RSC Advances ◽  
2015 ◽  
Vol 5 (102) ◽  
pp. 83880-83884 ◽  
Author(s):  
Zengmin Tang ◽  
Aasim Shahzad ◽  
Woo-Sik Kim ◽  
Taekyung Yu
Keyword(s):  
Aqueous Phase ◽  
Cost Effective ◽  
Chloride Ions ◽  
Copper Nanowires ◽  
Phase Synthesis ◽  
Cu Nanowires ◽  
Term Stability ◽  
Long Term Stability

This work describes a simple and cost-effective aqueous-phase synthesis of Cu nanowires with long-term stability. Chloride ions and branched polyethyleneimine (BPEI) were found to be of great importance to the formation and stabilization of Cu nanowires.

Synthesis, stabilization, growth behavior, and catalytic activity of highly concentrated silver nanoparticles using a multifunctional polymer in an aqueous-phase

RSC Advances ◽  
2015 ◽  
Vol 5 (36) ◽  
pp. 28652-28661 ◽  
Author(s):  
Aasim Shahzad ◽  
Woo-Sik Kim ◽  
Taekyung Yu
Keyword(s):  
Silver Nanoparticles ◽  
Catalytic Activity ◽  
Aqueous Phase ◽  
Ag Nanoparticles ◽  
Growth Behavior ◽  
Term Stability ◽  
Long Term Stability

Highly concentrated Ag nanoparticles (above 20 g L−1) synthesized by the reaction AgNO3 with BPEI exhibited long-term stability over more than 40 days.

scholarly journals Долговременная воспроизводимость эмиссионных характеристик алмазографитовых полевых источников электронов в нестационарных вакуумных условиях эксплуатации

2021 ◽  
Vol 47 (24) ◽  
pp. 17
Author(s):  
Р.К. Яфаров ◽  
А.В. Сторублев
Keyword(s):  
Cathode Material ◽  
Field Emission ◽  
Emission Characteristics ◽  
High Current ◽  
Current Field ◽  
Unsteady Temperature ◽  
Electron Sources ◽  
Residual Gas ◽  
Emission Density

The results of a study of the long-term reproducibility of the emission characteristics of electron sources with field emission density of up to 1000 A/cm2 of based on composite nanocarbon films are presented. It was found that high-current field emission is accompanied by the sputtering of residual gas ions from atoms of the cathode material and its sedimentation on the anode. The results can be used to predict the durability of high-current diamond-graphite cathodes with field emission when operating in unsteady temperature-vacuum conditions.

scholarly journals A therapeutic convection–enhanced macroencapsulation device for enhancing β cell viability and insulin secretion

2021 ◽  
Vol 118 (37) ◽  
pp. e2101258118
Author(s):  
Kisuk Yang ◽  
Eoin D. O’Cearbhaill ◽  
Sophie S. Liu ◽  
Angela Zhou ◽  
Girish D. Chitnis ◽  
...  
Keyword(s):  
Insulin Secretion ◽  
Cell Viability ◽  
Three Dimensional ◽  
Insulin Response ◽  
Convective Transport ◽  
Passive Diffusion ◽  
Loading Capacity ◽  
Nutrient Delivery

Islet transplantation for type 1 diabetes treatment has been limited by the need for lifelong immunosuppression regimens. This challenge has prompted the development of macroencapsulation devices (MEDs) to immunoprotect the transplanted islets. While promising, conventional MEDs are faced with insufficient transport of oxygen, glucose, and insulin because of the reliance on passive diffusion. Hence, these devices are constrained to two-dimensional, wafer-like geometries with limited loading capacity to maintain cells within a distance of passive diffusion. We hypothesized that convective nutrient transport could extend the loading capacity while also promoting cell viability, rapid glucose equilibration, and the physiological levels of insulin secretion. Here, we showed that convective transport improves nutrient delivery throughout the device and affords a three-dimensional capsule geometry that encapsulates 9.7-fold-more cells than conventional MEDs. Transplantation of a convection-enhanced MED (ceMED) containing insulin-secreting β cells into immunocompetent, hyperglycemic rats demonstrated a rapid, vascular-independent, and glucose-stimulated insulin response, resulting in early amelioration of hyperglycemia, improved glucose tolerance, and reduced fibrosis. Finally, to address potential translational barriers, we outlined future steps necessary to optimize the ceMED design for long-term efficacy and clinical utility.

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