A Development of Air Controlled Oxidizer for Treatment of Depleted Uranium Chip Waste

1997 ◽  
Vol 506 ◽  
Author(s):  
Kweon Ho Kang ◽  
Kil Jeong Kim ◽  
Hyun Kyoo Shin ◽  
Chul Kim ◽  
Young Moo Park
Keyword(s):  
Fly Ash ◽  
Heat Generation ◽  
Flow Rate ◽  
Uranium Oxide ◽  
Oxidation Temperature ◽  
Maximum Temperature ◽  
Complete Oxidation ◽  
Heating Rates ◽  
Maximum Heat ◽  
Image Position

ABSTRACTIn Korea Depleted Uranium(DU) is used in manufacturing a metallic nuclear fuel for the Korean Multi-Purpose Research Reactor(KMRR). In the manufacturing processes it produces DU chips and scraps as a waste material which composed of U-Ti, U-Zr, U-Mo and U-Si intermetallic compound. In this study Air Controlled Oxidizer(ACO) has been developed which facilitates DU to be converted into U308, the most stable form of uranium. Since DU chips oxidize rapidly and their heat of oxidation is very high(4.199kJ/g, U3O8), the inside temperature of the oxidizer is likely going up rapidly. Therefore the oxidizer must be able to be cooled properly or temperature increasement of the oxidizer must be under control. Kang et al.[1] reported for the oxidation of U-0.75wt%/o Ti chips in air that U308 was detected at the temperature above 350°C. And they[2] also reported that the maximum heat generation per unit time during oxidation was as follows:where Q was the maximum heat generation per unit timeWDU was the weight of DU loaded in ACOdw/dt was the reaction rateVair was the flow rate of input airR was the universal gas constantand T was the absolute temperature.From eq.(1) the maximum heat generation per unit time during oxidation is only function of the weight of DU loaded in ACO and the oxidation rate which is dependent on the oxidation temperature or the flow rate of input air.The ACO consists of an air flow meter, an air heater, an oxidation chamber with inner heater(capacity 7.5kW), an ash collection tank, a fly ash collector, a pressure gauge, a safety valve, and a soaking tank. The air flow meter is used to control the flow rate of input air below theoretical air requirement limit for the complete oxidation of DU. The inner heater is used to heat the inside of the oxidizer to an optimum oxidation temperature. The ash collection tank is used to collect uranium oxide powder after completion of oxidation. The fly ash collector is used both to collect flying ashes and to condense vaporized uranium oxide. Also, in ACO, DU chips are not ignited directly in order to prevent rapid temperature increasement. The oxidation environment only is achieved by heating the inside of oxidizer.To find effect of the oxidation temperature on the temperature of the oxidation chamber during treatment of DU, we conduct the experiment by changing heating rates of inner heater, 3, 4, 5 and 6kW, respectively. We conduct experiments for 120 minute with 2/min input air. However, it turned out that the complete oxidation is reached within 60 minute. After complete oxidation the weight gains of the DU chips is from 4.5 to 5.0 wt0/o and the DU chips are pulverized and they are converted to U 08 and 979 Mat. Res. Soc. Symp. Proc. Vol. 506 1998 Materials Research Society During the oxidation, maximum temperature increases to 470, 497.5, 572.5 and 6771C for heating rates 3, 4, 5 and 6kW, respectively. As the temperatures of the oxidation chamber outside surface are not exceed 1501C, however, DU chips are treated safely. In each experiment, weight before and after oxidation, the oxide forms of the product and the maximum temperature in the oxidation chamber during oxidation are shown in table 1. The maximum temperature profiles of the chamber inside and surface for time and heating rates are shown in Fig. I and 2, respectively.

In vitro comparison of cortical bone temperature generation between traditional sequential drilling and a newly designed step drill in the equine third metacarpal bone

2009 ◽  
Vol 22 (06) ◽  
pp. 442-447 ◽  
Author(s):  
J. García-López ◽  
L. S. Maranda ◽  
K. A. Bubeck
Keyword(s):  
Heat Generation ◽  
Metacarpal Bone ◽  
Maximum Temperature ◽  
Drilling Force ◽  
Maximum Heat ◽  
Pilot Hole ◽  
Excessive Heat ◽  
Metacarpal Bones ◽  
Step Drill

Summary Objectives: To compare heat generation and time to finish between a new step drill and sequential drilling in order to create a 6.2 mm pilot hole for insertion of a positive profile transfixation pin into the equine third metacarpal bone. Methods: Nine pairs of equine third metacarpal bones from cadavers of adult horses were used. Maximum temperature rise of the bone was measured continuously at the cis- and trans-cortices 1, 2 and 3 mm from the final pilot hole during creation of a 6.2 mm hole using a step drill and sequential drilling with 4.5, 5.5 and 6.2 mm drill bits. Five holes were drilled into the mid diaphysis of each bone in lateral to medial direction, and drilling forces of 60, 80 and 120 N were used (15 holes in each group). Time from start to finish was measured and cortical thickness was recorded for each hole. Results: The maximum heat generation (mean [95% CI]) with step drilling and sequential drilling was not significantly different at 60 N and 120 N of drilling force. However, at 80 N of drilling force, the 2.13 ºC difference between the two drilling techniques was significant. The time to finish (seconds) was significantly shorter for the holes created by step drilling (35.1 [32.06 – 37.59]) than by sequential drilling (145.8 [138.52 – 151.67]) (P < 0.001). Clinical Relevance: Based on our results, we concluded that the step drill is a viable alternative to traditional sequential drilling of equine third metacarpal bone because it did not result in excessive heat generation that can result in bone necrosis.

Nanoscale Analysis on Spark Plasma Sintered Fly-Ash Bricks and their Comparative Study with SiN-Zr Refractory Bricks

2020 ◽  
Vol 12 (2) ◽  
pp. 122-128
Author(s):  
D.K. Sahoo ◽  
M.S.V.R. Kishor ◽  
D.P. Sahoo ◽  
S. Sarkar ◽  
A. Behera
Keyword(s):  
Fly Ash ◽  
Intermetallic Compounds ◽  
Spark Plasma Sintering ◽  
Maximum Temperature ◽  
Maximum Hardness ◽  
Refractory Brick ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Refractory Bricks ◽  
Sintered Product

Background: Industries such as thermal power plants use coal as a source of energy and release the combustion products into the environment. The generation of these wastes is inevitable and thus needed to be reused. In India, coals with high ash content usually between 25 to 45% are used. The refractory bricks that were used earlier in steel industries were mainly based on silica, magnesia, chrome, graphite. In modern days, several other materials were introduced for the manufacturing of refractory bricks such as mullite, chrome-magnesite, zircon, fused cast, and corundum. The materials selection for refractory brick manufacturing depends on various factors such as the type of furnace and working conditions. Objectives: The current work aims to focus on the fly-ash subjected to spark plasma sintering process with a maximum temperature of 1500 °C and pressure 60 MPa for 15 minutes and to characterize to observe the properties with respect to their microstructure. Methods: Fly-ash collected from Rourkela Steel Plant was sintered using spark plasma sintering machine at the Indian Institute of Technology, Kharagpur. The powder placed in a die was subjected to a heating rate of 600-630 K/min, up to a maximum temperature of 1500˚C. The process took 15 minutes to complete. During the process, the pressure applied was ranging between 50 to 60 Mpa. 5-10 Volts DC supply was given to the machine with a pulse frequency of 30-40 KHz. The sintered product was then hammered out of the die and the small pieces of the sintered product were polished for better characterization. The bricks collected from Hindalco Industries were also hammered into pieces and polished for characterization and comparison. Results: The particles of fly-ash as observed in SEM analysis were spherical in shape with few irregularly shaped particles. The sintered fly-ash sample revealed grey and white coloured patches distributed around a black background. These were identified to be the intermetallic compounds that were formed due to the dissociation of compounds present in fly-ash. High- temperature microscopy analysis of the sintered sample revealed the initial deformation temperature (IDT) of the fly-ash brick and the refractory brick which were found to be 1298 °C and 1543 °C, respectively. The maximum hardness value observed for the sintered fly-ash sample was 450 Hv (4.413 GPa) which is due to the formation of nano-grains as given in the microstructure. The reason behind such poor hardness value might be the absence of any binder. For the refractory brick, the maximum hardness observed was 3400 Hv (33.34 GPa). Wear depth for the sintered fly-ash was found to be 451 μm whereas for the refractory brick sample it was 18 μm. Conclusion: The fly-ash powder subjected to spark plasma sintering resulted in the breaking up of cenospheres present in the fly ash due to the formation of intermetallic compounds, such as Cristobalite, syn (SiO2), Aluminium Titanium (Al2Ti), Magnesium Silicon (Mg2Si), Maghemite (Fe2O3), Chromium Titanium (Cr2Ti) and Magnesium Titanium (Mg2Ti), which were responsible for the hardness achieved in the sample. A large difference in the maximum hardness values of sintered fly-ash and refractory brick was observed due to the hard nitride phases present in the refractory brick.

scholarly journals Production of ceramics from coal fly ash

2012 ◽  
Vol 18 (2) ◽  
pp. 245-254 ◽  
Author(s):  
Biljana Angjusheva ◽  
Emilija Fidancevska ◽  
Vojo Jovanov
Keyword(s):  
Compressive Strength ◽  
Fly Ash ◽  
Solid State ◽  
Liquid Phase ◽  
Bending Strength ◽  
Coal Fly Ash ◽  
Liquid Phase Sintering ◽  
Heating Rates ◽  
Republic Of Macedonia ◽  
The Subject

Dense ceramics are produced from fly ash from REK Bitola, Republic of Macedonia. Four types of fly ash from electro filters and one from the collected zone with particles < 0.063 mm were the subject of this research. Consolidation was achieved by pressing (P= 133 MPa) and sintering (950, 1000, 1050 and 11000C and heating rates of 3 and 100/min). Densification was realized by liquid phase sintering and solid state reaction where diopside [Ca(Mg,Al)(Si,Al)2O6] was formed. Ceramics with optimal properties (porosity 2.96?0.5%, bending strength - 47.01?2 MPa, compressive strength - 170 ?5 MPa) was produced at 1100?C using the heating rate of 10?C/min.

scholarly journals Production of Fuel Oil from Municipal Plastic Wastes Using Thermal and Catalytic Pyrolysis

2020 ◽  
pp. 1-8
Author(s):  
Dan Kica Omol ◽  
Ongwech Acaye ◽  
David Fred Okot ◽  
Ocident Bongomin
Keyword(s):  
Activated Carbon ◽  
Reaction Time ◽  
Clay Mineral ◽  
Catalytic Pyrolysis ◽  
Fuel Oil ◽  
Maximum Temperature ◽  
Heating Rates ◽  
Thermal Pyrolysis ◽  
Plastic Wastes ◽  
Acid Activated Clay

Plastics have become an essential part of modern life today. The global production of plastics has gone up to 299 million tonnes in 2013, which has increased enormously in the present years. The utilization of plastics and its final disposal pose tremendous negative significant impacts on the environment. The present study aimed to investigate the thermal and catalytic pyrolysis for the production of fuel oil from the polyethene plastic wastes. The samples collection for both plastic wastes and clay catalyst, sample preparation and pyrolysis experiment for oil production was done in Laroo Division, Gulu Municipality, Northern Uganda Region, Uganda. Catalysts used in the experiment were acid-activated clay mineral and aluminium chlorides on activated carbon. The clay mineral was activated by refluxing it with 6M Sulphuric acid for 3 hours. The experiment was conducted in three different phases: The first phase of the experiment was done without a catalyst (purely thermal pyrolysis). The second phase involves the use of acid-activated clay mineral. The third phase was done using aluminium chlorides on activated carbon. Both phases were done at different heating rates. In purely thermal pyrolysis, 88 mL of oil was obtained at a maximum temperature of 39ºC and heating rates of 12.55ºC /minute and reaction time of 4 hours. Acid activated clay mineral yielded 100 mL of oil with the heating rates of 12.55ºC/minute and reaction time of 3 hours 30 minutes. While aluminium chlorides on activated carbon produced 105 mL of oil at a maximum temperature of 400ºC and heating rates of 15.5ºC /minute and reaction time of 3 hours 10 minutes. From the experimental results, catalytic pyrolysis is more efficient than purely thermal pyrolysis and homogenous catalysis (aluminium chlorides) shows a better result than solid acid catalyst (activated clay minerals) hence saving the energy needed for pyrolysis and making the process more economically feasible.

scholarly journals The Assessment of the Maximum Heat Production and Cooling Effectiveness of Three Different Drill Types (Conical vs. Cylindrical vs. Horizontal) during Implant Bed Preparation—An In Vitro Study

2021 ◽  
Vol 11 (21) ◽  
pp. 9961
Author(s):  
Stefan Ihde ◽  
Bartosz Dalewski ◽  
Łukasz Pałka
Keyword(s):  
In Vitro Study ◽  
Maximum Temperature ◽  
Internal Cooling ◽  
Type I ◽  
Ir Camera ◽  
Maximum Heat ◽  
Disc Cutters ◽  
Cooling Hole ◽  
Implant Bed

The aim of this experimental study was to verify thermal diffusion differences, by measuring the maximum temperature achieved with different drill shapes. Synthetic bone blocks of type I density made from solid rigid polyurethane (PUR) foam were used to perform the drilling procedures. The experiment was conducted at three different rotation speeds: 800, 3000 and 5000 rpm. Conical drills (with and without an internal cooling hole) were compared with horizontal drills and disc drills. The temperature during drilling for implant bed preparation was estimated with the use of thermocouples and an infrared (IR) camera. The temperature during drilling with disc cutters for lateral basal implants did not exceed 33 ∘C and the temperature decreased in proportion to higher drill speed. The results indicate that the tested design is safe and will not cause bone overheating.

Study on the residual performance of RC beams exposed to processed temperatures and fire

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Sachin Vijaya Kumar ◽  
N. Suresh
Keyword(s):  
Failure Modes ◽  
Elevated Temperatures ◽  
Slow Heating ◽  
Maximum Temperature ◽  
Rc Beams ◽  
Heating Rates ◽  
Fast Heating ◽  
Content Type ◽  
Temperature Increment ◽  
Residual Performance

PurposeThe Reinforced Concrete(RC) elements are known to perform well during exposure to elevated temperatures. Hence, RC elements are widely used to resist the extreme heat developing from accidental fires and other industrial processes. In both of the scenarios, the RC element is exposed to elevated temperatures. However, the primary differences between the fire and processed temperatures are the rate of temperature increase, mode of exposure and exposure durations. In order to determine the effect of two heating modalities, RC beams were exposed to processed temperatures with slow heating rates and fire with fast heating rates.Design/methodology/approachIn the present study, RC beam specimens were exposed to 200 °C, to 800 °C temperature at 200 °C intervals for 2 h' duration by adopting two heating modes; Fire and processed temperatures. An electrical furnace with low-temperature increment and a fire furnace with standard time-temperature increment is adapted to expose the RC elements to elevated temperatures.FindingsIt is observed from test results that, the reduction in load-carrying capacity, first crack load, and thermal crack widths of RC beams exposed to 200 °C, and 600 °C temperature at fire is significantly high from the RC beams exposed to the processed temperature having the same maximum temperature. As the exposure temperature increases to 800 °C, the performance of RC beams at all heating modes becomes approximately equal.Originality/valueIn this work, residual performance, and failure modes of RC beams exposed to elevated temperatures were achieved through two different heating modes are presented.

scholarly journals A Modified Analytical Heat Source Model for Numerical Simulation of Temperature Field in Friction Stir Welding

2020 ◽  
Vol 2020 ◽  
pp. 1-16
Author(s):  
Xiangqian Liu ◽  
Yan Yu ◽  
Shengli Yang ◽  
Huijie Liu
Keyword(s):  
Heat Flux ◽  
Friction Stir Welding ◽  
Analytical Model ◽  
Heat Generation ◽  
Tilt Angle ◽  
Temperature Fields ◽  
Analytical Models ◽  
Maximum Temperature ◽  
Thermal Cycles ◽  
Friction Stir

In the conventional analytical model used for heat generation in friction stir welding (FSW), the heat generated at the pin/workpiece interface is assumed to distribute uniformly in the pin volume, and the heat flux is applied as volume heat. Besides, the tilt angle of the tool is assumed to be zero for simplicity. These assumptions bring about simulating deviation to some extent. To better understand the physical nature of heat generation, a modified analytical model, in which the nonuniform volumetric heat flux and the tilt angle of the tool were considered, was developed. Two analytical models are then implemented in the FEM software to analyze the temperature fields in the plunge and traverse stage during FSW of AA6005A-T6 aluminum hollow extrusions. The temperature distributions including the maximum temperature and heating rate between the two models are different. The thermal cycles in different zones further revealed that the peak temperature and temperature gradient are very different in the high-temperature region. Comparison shows that the modified analytical model is accurate enough for predicting the thermal cycles and peak temperatures, and the corresponding simulating precision is higher than that of the conventional analytical model.

Analytical Study of Natural Convection in a Cavity With Volumetric Heat Generation

Volume 1 ◽  
2004 ◽  
Author(s):  
Mandar V. Joshi ◽  
U. N. Gaitonde ◽  
Sushanta K. Mitra
Keyword(s):  
Natural Convection ◽  
Aspect Ratio ◽  
Heat Generation ◽  
Central Region ◽  
Analytical Study ◽  
Vertical Direction ◽  
Maximum Temperature ◽  
Small Aspect Ratio ◽  
Governing Equations ◽  
Volumetric Heat Generation

A semi-analytical method for natural convection in a two dimensional rectangular enclosure, with uniform volumetric heat generation, having insulated horizontal boundaries, and isothermal vertical boundaries, has been studied here. In this method, the governing equations for natural convection, have been solved under the assumption that for a cavity with small aspect ratio, the flow in the central region of the cavity is only in the vertical direction. It is found that for the cavities with small aspect ratio, the temperature in central region of the cavity is nearly constant along the horizontal direction. However, there is a uniform temperature gradient in the vertical direction, which can be related to the maximum temperature in conduction. The velocity profiles and temperature profiles obtained in the present work, are compared with the numerical simulations by Fluent and a fair agreement is found between these results.

scholarly journals Comparison of heat transfer performance of ZnO-PG, α-Al2O3-PG, and γ-Al2O3-PG nanofluids in car radiator

2019 ◽  
Vol 9 ◽  
pp. 184798041987646 ◽  
Author(s):  
XiaoRong Zhou ◽  
Yi Wang ◽  
Kai Zheng ◽  
Haozhong Huang
Keyword(s):  
Heat Transfer ◽  
Heat Transfer Coefficient ◽  
Transfer Coefficient ◽  
Propylene Glycol ◽  
Flow Rate ◽  
Volume Concentration ◽  
Maximum Heat ◽  
Cooling Performance ◽  
Maximum Heat Transfer ◽  
The Heat Transfer Coefficient

In this study, the cooling performance of nanofluids in car radiators was investigated. A car radiator, temperature measuring instrument, and other components were used to set up the experimental device, and the temperature of nanofluids passing through the radiator was measured by this device. Three kinds of nanoparticles, γ-Al2O3, α-Al2O3, and ZnO, were added to propylene glycol to prepared nanofluids, and the effects of nanoparticle size and type, volume concentration, initial temperature, and flow rate were tested. The results indicated that the heat transfer coefficients of all nanofluids first increased and then decreased with an increase in volume concentration. The ZnO-propylene glycol nanofluid reached a maximum heat transfer coefficient at 0.3 vol%, and the coefficient decreased by 25.6% with an increase in volume concentration from 0.3 vol% to 0.5 vol%. Smaller particles provided a better cooling performance, and the 0.1 vol% γ-Al2O3-propylene glycol nanofluid had a 19.9% increase in heat transfer coefficient compared with that of α-Al2O3-propylene glycol. An increase in flow rate resulted in a 10.5% increase in the heat transfer coefficient of the 0.5 vol% α-Al2O3-propylene glycol nanofluid. In addition, the experimental temperature range of 40–60°C improved the heat transfer coefficient of the 0.2 vol% ZnO-propylene glycol nanofluid by 46.4%.

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