scholarly journals The Role of Laboratory Analog Experiments in Assessing the Performance of Waste Package Materials

1990 ◽  
Vol 212 ◽  
Author(s):  
James C. Cunnane ◽  
John K. Bates
Keyword(s):  
Volume Ratio ◽  
Reaction Rates ◽  
Waste Glass ◽  
System Level ◽  
Water Volume ◽  
Small Scale ◽  
Analog Testing ◽  
Waste Package ◽  
Laboratory Analog ◽  
Package Materials

ABSTRACTThere is an immediate need to begin to validate models that can be used for assessing the performance of waste package materials in an unsaturated repository environment. This paper examines available testing information and testing approaches that could support validation of models for engineering barrier system (EBS) radionuclide release. The content is presented in the context of the general methodology that has been proposed for validating performance assessment models [1], Available experimental observations are used to test some of the EBS release rate modeling premises. These observations include evidence of fluid film formation on waste glass surfaces in isothermal humid environments, accelerated waste glass reaction rates under repository service conditions of large glass surface area to water volume ratio, and mobilization of radionuclides as solutes and colloids. It is concluded that some important modeling premises may not be consistent with available experimental Information. However, it is also concluded that future laboratory testing, which simulates the Integrated waste package system (i.e., laboratory analog testing), is needed to evaluate the significance of these Inconsistencies and to test the system level models. A small-scale apparatus which was developed and tested to examine the feasibility of laboratory analog testing for the unsaturated Yucca Mountain repository environment is described.

Effects of Flow Parameters on the Leaching of Nuclear Waste Glass

1984 ◽  
Vol 44 ◽  
Author(s):  
R. B. Adiga ◽  
E. P. Akomer ◽  
D. E. Clark
Keyword(s):  
Nuclear Waste ◽  
Flow Rate ◽  
Volume Ratio ◽  
Water Volume ◽  
Leaching Rate ◽  
Leaching Behavior ◽  
Waste Package ◽  
Flow Parameters ◽  
Nuclear Waste Glass ◽  
Independent Effects

Environmental conditions in a repository are expected to be significantly different from those encountered by a glass tested under MCC-1 specifications. In addition to variations in flow rate and glass surface area to water volume ratio (SA/V), the water chemistry and presence of waste package components in the repository will most certainly affect the leaching behavior of the glass. The independent effects of each of these variables have been studied by numerous investigators. For example, it is well known that the leaching rate increases as the flow rate increases (1). Also, the rate of approach to saturation is increased as SA/V is increased under MCC-1 type testing (2). The use of silicate water generally decreases the rate of leaching while waste package components such as iron enhances the leaching rate of glass under MCC-1 type testing (3–4).

Study of The Influence of Different Variables on Clathrate Practical Applications in Phenol Removal

2020 ◽  
Vol 38 (9A) ◽  
pp. 1373-1383
Author(s):  
Riyadh S. AL- Mukhtar ◽  
Shurooq T. Remedhan ◽  
Marwa N. Hussin
Keyword(s):  
Crystal Structures ◽  
High Capacity ◽  
Volume Ratio ◽  
Constant Speed ◽  
Water Volume ◽  
Phenol Removal ◽  
Process Performance ◽  
Economic Costs ◽  
Practical Applications ◽  
Glass Cell

In this work, effluent wastewater treated by using cyclopentane-water Clathrate system to treat water contaminates with phenols at concentrations (300, 250, 200, 150, 100 and 50) ppm in order to investigate the capability of process performance. Clathrate or hydrate are strong crystal structures including water (host particles) and little particles (guest particles). The experiments were conducted at different cyclopentane-water volume ratios (1: 2 and 1: 4). The work was done in a 250 ml glass cell with an electric mixer at a constant speed of 280 cycles per minute. Phenol was highest removal percent at 300ppm at 1: 4volume ratio was (92.3%), while the lowest concentration at 50 ppm and 1: 2volume ratio was (55%). Yield and Enrich factor had the highest values at the lowest concentration 50ppm and 1:2 volume ratio were (85% and 2.42) respectively. The technique of the Clathrate proved that it has a high capacity in the separation and achieve high removal percentage compared to other methods at standard conditions when the pressure of 1 atmosphere and temperature higher than the degree of freezing water and less economic costs compared to other methods.

Effect of Synthesis Parameters on Size of the Biodegradable Poly (L-Lactide) (PLLA) Microspheres

2013 ◽  
Vol 858 ◽  
pp. 60-66 ◽  
Author(s):  
A.A. Hawari ◽  
C.Y. Tham ◽  
Zuratul Ain Abdul Hamid
Keyword(s):  
Electron Microscopy ◽  
Volume Ratio ◽  
Water Volume ◽  
Synthesis Parameters ◽  
Weight Variation ◽  
Infra Red ◽  
Biodegradable Poly ◽  
Evaporation Technique ◽  
Molecular Weight Variation ◽  
Scanning Electron

In this work, PLLA microspheres were prepared via emulsion solvent evaporation technique. Several synthesis parameters were studied to evaluate their effect on the size of PLLA microspheres. PLLA pallets before emulsion and PLLA microspheres surface chemistry after emulsion were determined using Fourier Transform Infra-red (FTIR). Results showed that PLLA pallets and microspheres FTIR obtained an identical spectrum. Microspheres size and surface morphology were determined using Scanning Electron Microscopy (SEM). In conclusion, the parameters that significantly affect the size of PLLA microspheres were PLLA concentration, DCM to water volume ratio, PVA concentration and stirring speed. PVA molecular weight variation showed no significant change in microspheres size.

Modeling an Enclosed, Turbulent Reacting Methane Jet With the Premixed Conditional Moment Closure Method

2013 ◽  
Author(s):  
Scott Martin ◽  
Aleksandar Jemcov ◽  
Björn de Ruijter
Keyword(s):  
Turbulent Combustion ◽  
Large Scale ◽  
Reaction Rates ◽  
Moment Closure ◽  
Scalar Dissipation ◽  
Small Scale ◽  
Conditional Moment ◽  
Progress Variable ◽  
Conditional Moment Closure ◽  
Scale Turbulence

Here the premixed Conditional Moment Closure (CMC) method is used to model the recent PIV and Raman turbulent, enclosed reacting methane jet data from DLR Stuttgart [1]. The experimental data has a rectangular test section at atmospheric pressure and temperature with a single inlet jet. A jet velocity of 90 m/s is used with an adiabatic flame temperature of 2,064 K. Contours of major species, temperature and velocities along with velocity rms values are provided. The conditional moment closure model has been shown to provide the capability to model turbulent, premixed methane flames with detailed chemistry and reasonable runtimes [2]. The simplified CMC model used here falls into the class of table lookup turbulent combustion models where the chemical kinetics are solved offline over a range of conditions and stored in a table that is accessed by the CFD code. Most table lookup models are based on the laminar 1-D flamelet equations, which assume the small scale turbulence does not affect the reaction rates, only the large scale turbulence has an effect on the reaction rates. The CMC model is derived from first principles to account for the effects of small scale turbulence on the reaction rates, as well as the effects of the large scale mixing, making it more versatile than other models. This is accomplished by conditioning the scalars with the reaction progress variable. By conditioning the scalars and accounting for the small scale mixing, the effects of turbulent fluctuations of the temperature on the reaction rates are more accurately modeled. The scalar dissipation is used to account for the effects of the small scale mixing on the reaction rates. The original premixed CMC model used a constant value of scalar dissipation, here the scalar dissipation is conditioned by the reaction progress variable. The steady RANS 3-D version of the open source CFD code OpenFOAM is used. Velocity, temperature and species are compared to the experimental data. Once validated, this CFD turbulent combustion model will have great utility for designing lean premixed gas turbine combustors.

Fluid Flow and Heat Transfer of Liquid Sodium in Small-Scale Heat Sinks With Different Geometries

2021 ◽  
Author(s):  
Mahyar Pourghasemi ◽  
Nima Fathi
Keyword(s):  
Heat Transfer ◽  
Reynolds Number ◽  
Cross Sections ◽  
Heat Sink ◽  
Volume Ratio ◽  
Heat Sinks ◽  
Liquid Sodium ◽  
Small Scale ◽  
Nusselt Numbers ◽  
The Difference

Abstract 3-D numerical simulations are performed to investigate liquid sodium (Na) flow and the heat transfer within miniature heat sinks with different geometries and hydraulic diameters of less than 5 mm. Two different straight small-scale heat sinks with rectangular and triangular cross-sections are studied in the laminar flow with the Reynolds number up to 1900. The local and average Nusselt numbers are obtained and compared against eachother. At the same surface area to volume ratio, rectangular minichannel heat sink leads to almost 280% higher convective heat transfer rate in comparison with triangular heat sink. It is observed that the difference between thermal efficiencies of rectangular and triangular minichannel heat sinks was independent of flow Reynolds number.

Dynamic Model of Rapeseed Oil Hydrolysis Reaction in Sub-Critical Water

2013 ◽  
Vol 860-863 ◽  
pp. 510-513 ◽  
Author(s):  
Yi Zhe Li ◽  
Hua Wang ◽  
Gui Rong Bao
Keyword(s):  
Activation Energy ◽  
Reaction Time ◽  
Dynamic Model ◽  
Rapeseed Oil ◽  
Reaction Order ◽  
Volume Ratio ◽  
Hydrolysis Reaction ◽  
Water Volume ◽  
Oil Water ◽  
Oil Hydrolysis

Experiments of Rapeseed Oil Hydrolysis Reaction in Sub-Critical Water (250-300°C, 5-60min) are Conducted in this Paper. Results Show that the Best Conditions for Rapeseed Oil Hydrolysis are Reaction Temperature 290°C, Oil-Water Volume Ratio 1:3, Reaction Time 40min, and Conversion Rate 98.9%. Meanwhile, Kinetic Analysis of this Hydrolysis Reaction is Presented. we Learn that Hydrolysis Reaction Order is 0.7778, Activation Energy is 55.34kJ/mol and the Dynamic Model is .

scholarly journals Role of the reaction-structure coupling in temperature compensation of the KaiABC circadian rhythm

2021 ◽  
Author(s):  
Masaki Sasai
Keyword(s):  
Temperature Compensation ◽  
Oscillation Amplitude ◽  
Thermal Fluctuations ◽  
Reaction Rates ◽  
System Level ◽  
Single Amino Acid ◽  
Structural Transitions ◽  
Single Amino Acid Residue ◽  
Residue Substitution

When the mixture solution of cyanobacterial proteins, KaiA, KaiB, and KaiC, is incubated with ATP in vitro, the phosphorylation level of KaiC shows stable oscillations with the temperature-compensated circadian period. We analyzed this temperature compensation by developing a theoretical model describing the feedback relations among reactions and structural transitions in the KaiC molecule. The model showed that the reduced structural cooperativity should weaken the negative feedback coupling among reactions and structural transitions, which enlarges the oscillation amplitude and period, explaining the observed significant period extension upon single amino-acid residue substitution. We propose that an increase in thermal fluctuations similarly attenuates the reaction-structure feedback, explaining the temperature compensation in the KaiABC clock. The model suggests that the ATPase reactions in the CI domain of KaiC affect the period depending on how the reaction rates are modulated. The KaiABC clock provides a unique opportunity to analyze how the reaction-structure coupling regulates the system-level synchronized oscillations of molecules.

Chemical Durability of High Burnup Lwr-Spent Fuel in Concentrated Salt Solutions

1993 ◽  
Vol 333 ◽  
Author(s):  
A. Loida ◽  
B. Grambow ◽  
P. Dressier ◽  
K. Friese ◽  
H. Geckeis ◽  
...  
Keyword(s):  
Surface Area ◽  
Volume Ratio ◽  
Sample Surface ◽  
Solution Concentration ◽  
Reaction Rates ◽  
Spent Fuel ◽  
Intrinsic Dissolution ◽  
Fine Grained ◽  
High Burnup ◽  
Saturation Effects

ABSTRACTHigh-burnup (<50 MWd/kgU) spent fuel samples of various sizes were exposed to NaCl solutions under static, anaerobic and reducing conditions. The accumulated corrosion time was about 200 days. Gas phase and leach solutions were analyzed. By dissolving mm sized fragments in large volumes of solution, saturation effects were avoided and upper limits for intrinsic dissolution rates of about 5-20 mg/(m2d) were measured. Surface area normalized reaction rates were significantly lower when using fine grained fuel powder (estimated sample surface area to solution volume ratio S/V ca. 3000 m-1), indicating saturation effects. The maximum concentrations of Pu and Am in the tests are close to reported solubility limited concentrations in pure 5m NaCl solutions in the absence of radiolysis effects. The presence of iron effectively reduces the solution concentration of all measured radionuclides (except Cs).

Can Water Dilution Avoid Flashback on a Hydrogen Enriched Micro Gas Turbine Combustion? A Large Eddy Simulations Study

2020 ◽  
Author(s):  
Alessio Pappa ◽  
Laurent Bricteux ◽  
Pierre Bénard ◽  
Ward De Paepe
Keyword(s):  
Gas Turbines ◽  
Reaction Rates ◽  
Operating Conditions ◽  
Large Eddy Simulations ◽  
Small Scale ◽  
Reference Case ◽  
Large Eddy ◽  
Pure Methane ◽  
Water Dilution ◽  
Air Humidification

Abstract Considering the growing interest in Power-to-Fuel, i.e. production of H2 using electrolysis to store excess renewable electricity, combustion-based technologies still have a role to play in the future of power generation. Especially in a decentralized production with small-scale cogeneration, micro Gas Turbines (mGTs) offer great advantages related to their high adaptability and flexibility, in terms of operation and fuel. Hydrogen (or hydrogen enriched methane) combustion is well-known to lead to flame and combustion instabilities. The high temperatures and reaction rates reached in the combustor can potentially lead to flashback. In the past, combustion air humidification (i.e. water addition) has proven effective to reduce temperatures and reaction rates, leading to significant NOx emission reductions. Therefore, combustion air humidification can open a path to stabilize hydrogen combustion in a classical mGT combustor. However accurate data assessing the impact of humidification on the combustion is still missing for real mGT combustor geometries and operating conditions. In this framework, this paper presents a comparison between pure methane and hydrogen enriched methane/air combustions, with and without combustion air humidification, in a typical mGT combustion chamber (Turbec T100) using Large Eddy Simulations (LES) analysis. In a first step, the necessary minimal water dilution, to reach stable and low emissions combustion with hydrogen, was assessed using a 1D approach. The one-dimensional unstretched laminar flame is computed for both pure methane (reference case) and hydrogen enriched methane/air combustion cases. The results of this comparison show that, for the hydrogen enriched combustion, the same level of flame speed as in the reference case can be reached by adding 10% (in mass fraction) of water. In a second step, the feasibility and flexibility of humidified hydrogen enriched methane/air combustion in an industrial mGT combustor have been demonstrated by performing high fidelity LES on a 3D geometry. Results show that steam dilution helped to lower the reactivity of hydrogen, and thus prevents flashback, enabling the use of hydrogen blends in the mGT at similar CO levels, compared to the reference case. These results will help to design future combustor towards more stability.

Stability of the PEG Fatty Acid Glycerides Based O/W Emulsions

2021 ◽  
Vol 58 (4) ◽  
pp. 271-277
Author(s):  
Zihan Wang ◽  
Liangliang Lin ◽  
Hujun Xu
Keyword(s):  
Droplet Size ◽  
Lauric Acid ◽  
Volume Ratio ◽  
Water Volume ◽  
Optimal Conditions ◽  
Rotational Rheometer ◽  
Emulsion Systems ◽  
Oil Water ◽  
The Stability ◽  
Emulsifier Concentration

Abstract In the present work, oil-in-water (O/W) emulsion systems were prepared by using the PEG-7 lauric acid glycerides as the emulsifiers and the liquid paraffin as the oil phase. The influence of processing parameters such as emulsification temperature, stirring speed, emulsifier concentration, oil-water volume ratio and polymer addition on the stability of the emulsion systems was investigated. In order to determine the optimal conditions for the preparation of the emulsion systems based on PEG-7 lauric acid glycerides, a laser drop size analyser and a rotational rheometer were used. As the stability of the O/W emulsion systems increased, the average droplet size of the O/W emulsions measured by the laser droplet size analyser became smaller and the viscosity, storage modulus and loss modulus of the O/W emulsions measured by the rotational rheometer became larger. The following optimal conditions were determined in this study: emulsification temperature 80°C, stirring speed 500 r/min, emulsifier concentration 5 wt%, oil-water volume ratio 1:1 and added amount of xanthan gum 0.2 wt%. The droplet morphology of the O/W emulsion prepared under the optimal conditions, which was characterised by a super high magnification microscope, is small. Furthermore, the long-term stability of the emulsion system prepared under the optimal conditions was investigated over a period of time (4 weeks). The O/W emulsion proves to be well stable even after 4 weeks, with a water separation rate of 0%.

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