Investigation of flow and heat transfer in a large-scale spent nuclear fuel cooling pond

The recent focus on nuclear power has led to the need for more efficient and economical methods of operating the Spent Nuclear Fuel (SNF) cooling ponds as well as complying with the strict safety and environmental legislations imposed by the IAEA and the UK Government. Like many other industrial applications, the design and operation of the SNF cooling ponds have evolved from experience; trial and error. Since the stored materials in such ponds are radioactive, it is very difficult to perform experimental studies. As a result, a rigorous scientific study based on fundamental principles has to be performed. The present research explores analytically and numerically the main processes that take place across the pond installation. The body of the present study includes four main parts: the first part is involved in modelling the heat loss from the free water surface, mainly due to evaporation, using analytical and single-phase numerical approaches, which represents a critical factor in the modelling of the large-scale cooling ponds. The predicted results were in good agreement with experimental data available in open literature. In the second part, a thermal model using Microsoft Excel spreadsheet was developed for the cooling pond based on an analytical approach. The well-mixed hypothesis was adopted to describe the water zone as well as the humid air zone. Also, the ventilation system was considered within this model. The developed spreadsheet tool was validated against reliable data available for Maine Yankee pool as well as temperature measurements collected from the Sellafield site. This spreadsheet tool is able to describe the transient behaviour with low computational cost, allowing many "what-if" scenarios to be rapidly investigated. In the third part, Computational Fluid Dynamics (CFD) was used to model the cooling pond at both macro and micro levels. The macro level modelling involved in developing a CFD model for Sellafield’s cooling pond where the fuel regions were approximated to porous medium. The computational domain was produced for the water zone only, where the humid air zone was introduced to the model by coupling of the spreadsheet model with the CFD model. This model was validated and used to examine the distribution of water temperature to confirm the reliability of the adopted well-mixed approach in the analytical model. The outcomes from the CFD and spreadsheet models were used to provide some boundary conditions to the micro-level model of the fuel assemblies. The modelling methodology of the fuel assemblies was partially validated with experimental data for heat transfer around vertical cylinder. The maximum temperature of the water within the rack arrangement was determined under various conditions and a correlation was proposed. Finally, a sensitivity study was performed using Taguchi method and the statistical method of ANOVA to assess the influence of the cooling systems as well as the environmental conditions on the thermal performance of the cooling pond. The spreadsheet model was implemented to carry out the calculations. The outcomes from this study were presented in the form of recommendations that may be able to aid the organisation to manage their cooling pond more efficiently and safely during the normal operating conditions as well as recovery from an accident scenario

Physical Sulphate Attack on Concrete

Field experience with concrete exposed to sulphates has often shown that concrete can suffer from surface scaling above the ground level caused by physical sulphate attack. This type of attack has been ignored and, in some instances, confused with chemical sulphate attack. In addition, current standards that evaluate the performance of concrete under sulphate attack, only deal with the chemical aspects of sulphate attack. This lack of information has led to confusion and contradictory views regarding the mechanisms of concrete deterioration due to physical sulphate attack. In the current thesis, the performance of concrete exposed to environments prone to physical sulphate attack was investigated. The effects of mineral additives, water-to binder (w/b) ratio, along with various curing conditions on the performance of concrete exposed to physical sulphate attack was studied. In addition, the effectiveness of different surface treatment materials in mitigating physical sulphate attack on concrete was explored. Results show that concrete can experience dual sulphate attack. The lower immersed portion can suffer from chemical sulphate attack, while the upper portion can be vulnerable to physical attack. Lowering the w/b ratio and moist-curing the concrete reduced surface scaling above the solution level since the volume of pores was decreased. Although partial replacement of cement with pozzolans also decreased the pore volume, surface scaling increased due to the increased proportion of small diameter pores and the associated growth of capillary suction and surface area for evaporation. Epoxy- and silane-based surface treatment materials were found to be adequate for protecting both cured and non-cured concrete exposed to physical sulphate attack. However, it was found that adequate curing of the concrete before coating is important to eliminate the separation of the surface treatment based on bitumen and to enhance the resistance of concrete to physical sulphate attack. Using a water-based solid acrylic polymer resin did not provide adequate protection of concrete against physical sulphate attack

A Product-Based Approach to Translation Training

This study seeks to demonstrate that active interaction between learner and teacher rather than passive reception by the teacher - as obtains in traditional teaching models - is essential. A product-based analysis of actual training makes it possible to identify a translation problem and subsequently apply theoretical considerations. Depending on the nature of the text being translated, error analysis can be used effectively not only for monitoring student progress but also for appraising general performance.Cette étude vise à montrer la nécessité de préconiser une interaction active entre l’enseignant et l’enseigné plutôt que la réception passive par l’enseignant d’un texte produit par l’enseigné. En situation de formation, l’analyse du « produit » permet d’identifier les problèmes et de chercher des solutions en s’appuyant sur des considérations théoriques. Selon la nature du texte à traduire, l’analyse des erreurs constitue un moyen efficace non seulement de suivre le progrès de l’étudiant mais d’apprécier son niveau de performance

Impact of the degree of tricuspid valve tethering on the early outcome of tricuspid valve repair with the De-Vega technique

Background: Functional tricuspid regurgitation (TR) is usually caused by leaflet tethering, and annuloplasty is usually recommended to repair annulus dilatation. This work aimed to evaluate the impact of the degree of the tricuspid valve (TV) tethering on the early outcome of tricuspid valve repair with the De-Vega technique. Methods: This prospective study included 50 patients with De-Vega tricuspid valve repair. Patients were divided into two groups; Group A (n= 25) included patients with tricuspid valve tethering of 8 mm or less, and Group B (n= 25) included patients with tricuspid valve tethering distance of more than 8 mm. Results: The mean age of Group A was 46.1 ±3.5 years compared to 49.6 ±7 years in Group B. There were significant differences in postoperative ejection fraction (48.7 ±12.5 vs. 39.1 ±9.4 %, P= 0.003), TV tethering distance (0.6 ±0.2 vs. 1.1 ±0.4 cm, P <0.001), and area (1.1 ±0.5 vs.  2.6 ±0.9 cm2; P<0.001),  and right ventricle fractional area (32.2± 7.9 vs. 25.4 ±9.7 cm2, P= 0.008) in Group A vs. B, respectively. There were no differences in postoperative complications, ICU, and hospital stay between groups. Conclusion: Residual tricuspid regurgitation after De-Vega annuloplasty could be related to TV tethering distance. Increased TV tethering distance could be associated with reduced postoperative ejection fraction

Experimental investigation of non-linearities in thermoacoustic systems: Streaming, transition to turbulence and entrance effects

Thermoacoustic systems (engines or refrigerators) convert any source of heat energy, including solar energy and waste heat, into electricity or cooling effect. These systems are reliable and durable as they operate with few or no moving parts and they employ environmentally-friendly gases without gaseous emissions. However, thermoacoustic systems suffer from many non-linearities that deteriorate the overall performance after a certain level such as streaming, turbulence generation, entrance effects and harmonic generation. This thesis focuses on first three of these non-linearities. Streaming is a second order steady flow that convects a certain amount of heat. The convected heat does not contribute to the thermoacoustic conversion process and hence it represents a loss. In this work, the effects of the natural convection flow on Rayleigh streaming have been investigated. The first objective of this work is to investigate the distribution of the axial mean velocity inside a simple standing-wave thermoacoustic engine using both Particle Image Velocimetry and Laser Doppler Velocimetry. The engine consists of a stack heated from one side whereas the other side is left uncontrolled. The velocity measurements cover the axial distance from the cold side of the stack to the termination of the resonator. Also, dynamic pressure and mean gas temperature measurements are conducted. Three different regions are observed and named the “cold streaming†region, the “hot-streaming region†and the “end-effects†region. In the cold streaming region, the measured mean velocity distribution agrees well with the theoretical expectation of Rayleigh streaming at low acoustic level. At high acoustic level, the measured quantities deviate from the theoretical expectations reported in the literature. Also, the size of the cold streaming region was found to decrease with the increase of the acoustic level. In the hot streaming region, where the measured wall temperature gradient is non-zero, the measured mean velocity distribution does not agree with the theoretical expectation for all acoustic levels. This discrepancy was found to be caused by the natural convection flow originated by the non-uniform temperature distribution of the resonator wall. In this work, the natural convection flow is decoupled from the acoustic streaming flow in order to measure the natural convection flow distribution inside the engine. The results reveal that there is a competition between acoustic streaming flow and the natural convection flow. This competition, at some acoustic levels, results in a zero mean axial velocity distribution. In the end-effects region, the mean flow velocity is disturbed by the vortex generation near to the stack. The size of each of these three regions is determined for different acoustic levels. As the flow inside the thermoacoustic systems has an oscillating nature, the study of the transition to turbulence in the oscillating flow is critical to understand the flow characteristics at high velocity amplitudes, which is the second objective of this work. In this work, the transition to turbulence in an oscillating flow has been studied at two different frequency ranges namely the sub-acoustic (low) frequency range (i.e. frequency ≪ 20 Hz) and the acoustic (high) frequency range (i.e. frequency ≥ 20 Hz). In the sub-acoustic frequency range, the transition to turbulence under the oscillating flow conditions inside a square duct is investigated experimentally. For this purpose, the oscillating flow is generated by a mechanical system known as the Scotch-Yoke mechanism that is able to provide an oscillating flow with wide range of amplitudes at low frequencies. The axial velocity profile is measured using Particle Image Velocimetry and two dimensionless parameters are used to describe the oscillating flow namely the Reynolds number and the Womersley number. At low Reynolds numbers, the measured axial velocity profile in the duct agrees reasonably well with the theoretical laminar velocity profile over the complete cycle; whereas at higher Reynolds numbers, the results show that the agreement is limited to the acceleration phase. The transition to turbulence process is identified by measuring the turbulence intensities. The turbulence intensities based on both velocity components at both the center of the duct and near to the viscous penetration depth increase as the Reynolds number is increased. Also, the cycle-average Reynolds stress is estimated. Beyond a certain Reynolds number, the cycle-average Reynolds stress experiences a sudden increase indicating transition to turbulence and hence the value of the critical Reynolds number can be determined. The estimated value of the critical Reynolds number, which equals to 500, complies with the literature. The work is then extended to the acoustic (high) frequency range. In the acoustic frequency range, the mechanical Skotch-Yoke system is replaced by two powerful loudspeakers operating at 180 deg out-of-phase to produce an oscillating flow with high velocity amplitudes at the resonance frequency of the system. The same methodology is used to investigate the transition to turbulence at high frequency range. The cycle-average Reynolds stress experiences a sudden increase near the wall at Reynolds number of 270. The vorticity fields are calculated from the measured 2-D velocity field. It is found that the vorticity value increases as the Reynolds number is increased. Also, the largest vorticity value is observed near the wall. As the Reynolds number increases the largest vorticity value shifts away from the wall during the deceleration phases in the acoustic cycle. The spatial energy density spectrum is calculated at different phases for different Reynolds numbers. Also, the cycle-average spatial energy density spectrum is calculated. The slope of the decay of the spatial energy at high wavenumbers was found to be nearly equals to the universal value of -5/3. As the thermoacoustic core of any thermoacoustic systems consists of a stack and heat exchangers, the study of the oscillating flow behavior in the vicinity of the stack is important, which constitutes the third objective of this work. The stack is usually modelled as a set of parallel plates. This work focuses on the effects of the plate-end shape on the oscillating flow morphology at high velocity amplitudes. Four different plate-end shapes namely rectangular, circular, 90O triangular and 30O triangular are placed inside an acoustic resonator. The temporal evolution of the vorticity field in the vicinity of the plates is investigated. The vortices originated at the beginning of the ejection stage (flow moves outwards the plates) and moves with the flow till they reach an axial distance nearly equals to one acoustic displacement amplitude. As the Reynolds number increases, the generated rounded-vortices around each plates transformed from two counter-rotating vortices attached to the plate into two elongated counter-rotating vortices. Also, the non-periodicity (cycle-to-cycle variations) of the oscillating flow in the vicinity of the plates is reported. As the Reynolds number increases, the non-periodicity of the flow does not change significantly. The 30O triangular plate-end shape reduces the non-periodicity of the oscillating flow near the plates at different axial locations whereas the other plate-end shapes have nearly similar values of non-periodicity

Clinical Impact of Custodiol Cardioplegic Solution on Patients Undergoing Complex Cardiac Surgery With Mild to Moderate Impairment of Left Ventricular Systolic Function

Background: The Bretschneider HTK solution is used widely for multiorgan preservation for transplantation, as well as a cardioplegic agent that allows single dose administration which is an attractive option for lengthy complex cardiac surgery. It was proved that it is simple to use, safe and practical. Moreover, it is considered to confer sufficient myocardial protection for more than 2 h of cardiac arrest. We undertook this descriptive study to analyze the performance of HTK solution in patients undergoing complex cardiac surgery with mild to moderate impairment of left ventricular systolic function. Patients and methods: A total of 50 patients underwent different complex cardiac surgery at national heart institute from January 2015 to November 2016 using single dose Custodiol cardioplegia as the primary and sole cardioplegic agent, their data was prospectively collected and their hospital outcome was analyzed as regards to ten study endpoints namely Prolonged ventilation, return to theatre for bleeding, renal failure, stroke, 30 days mortality, postoperative MI, need for inotropes, time on inotropes, ICU stay and hospital stay. Pre- and postoperative echocardiography was done to compare and evaluate the change of LV function using the parameters of End Systolic Dimension, End Diastolic Dimension, Fraction Shortening and Ejection Fraction of the left ventricle. Results: Half of the patients were males. Their age ranged between 16 – 65 years with a mean (standard deviation) of 47.46(11.10). preoperative ejection fraction ranged from 30 % to 49% with a mean (standard deviation) of 41.8 (6.32), the majority of them (64%) had NYHA class of 3 and half of them had CCS of 3. all patients were done electively. The most common procedure done was redo DVR 24% (12 patients) followed by Bentall operation 22%(11 patients). This is followed by CABG + MVR 7 patients (14%), then an equal number of 6 patients (12%) who underwent redo MVR post-infective endocarditis and CABG+ MVrep. The repair of tricuspid valve was done for 14 patients (28%) either with MVR or DVR. 4 patients (8%) had CABG +AVR for their combined lesions and another equal number of two patients (4%) underwent redo CABG and AVR + conduit (valve separate tube graft operation). prolonged ventilation occurred in 20% of the cases. An equal percentage of 6% of the patients had to return to the operative room and had postoperative MI. Renal failure occurred in 4% of the patients and as far as 30-day mortality is concerned, a similar 4% of patients died within this period. EF and FS were very similar when compared together (41.8 ± 6.32 %, 20.8 ± 2.35 % preoperatively compared to 41.92 ± 7.49%, 20.85 ± 3.25% postoperatively). P value was insignificant (0.937 and 0.929) respectively. Conclusion: A single dose of an HTK cardioplegic solution provides good myocardial protection in complex cardiac surgery with mild to moderate impairment of LV function and has a good immediate postoperative outcome

Influence of plyometric jump training on the physiological changes of male handball players

Running economy and velocity at maximal oxygen uptake are considered the most substantial physiological performance indicators in team sports. plyometric training are important techniques that enhance the neuromuscular functioning in athletes. The aim of the present study is to investigates the change in maximal oxygen uptake (VO2max) and running economy (RE). 16 male participants aged 21 years old. Participants underwent pre- and post-intervention tests including running economy, VO2max within 48 h before and after the training protocol. Statistically significant differences were seen in running economy and VO2max after training (p < .01). The current study suggested that plyometric training for 12 weeks can improve running economy and VO2max

Spatial Design Stimuli to Promote Wellness through Buildings’ Design

Mental Health problems are remarkably increasing in the UK, where people are facing di˙erent challenges day after day, including stresses from everyday life. Out of a deep belief that architecture can play a significant role in supporting users’ wellbeing, instead of augmenting their stresses, this paper analyzes an extensive multidisciplinary literature review, of 720 sources, from three di˙erent disciplines: psychology, medicine and architecture. The analyzed literature studies the relationship between users’ wellbeing and the surrounding spatial environment. The investigation aims to identify a set of possible architectural design parameters that can a˙ect users’ psychological wellbeing. The analysis identified fifteen spatial psychologically supportive design stimuli (PSDS); each of them was subject of further procedures of in-depth analysis queries that aim to define their main characteristics, impacts on users’ psychology and wellbeing, and their influences within the design of public buildings. The study aims to benefit the development of psychologically considerate built environment design, as well as identifying potential research routes for future spatial qualitative researches

Enhancing Exports through Managing Logistics Performance: Evidence From Middle East and African Countries

Logistics activities and its cost affect daily businesses operations and eventually the country’s economy. If countries are able to manage logistics performance efficiently it will be able to compete better internationally. The key objective of this study is to investigate the relationship between the logistics performance index and its components and exports focusing on Middle East and African countries using a regression model. Results of this study indicated that the logistics performance index positively enhance countries exports. In addition, logistics performance index components namely; customs, infrastructure, international shipments and timeliness have a significant impact individually, except for logistics quality, competence, tracking and tracing. The paper aims at supporting the economic policy maker to improve the economic decision in the field of logistics

Soil types and their relations with radon concentration levels in Middle Governorate of Gaza Strip, Palestine

Determination of natural radioactivity has been carried out in surface and core agricultural soil samples collected from various sites in the Middle Governorate – Gaza Strip, Palestine. Mechanical and chemical analysis has been done to determine soil characteristics. Radon activity concentration measurements were carried out using solid state nuclear tracks detectors, Cr-39. The mechanical analysis results show that they belong to two classes, sandy loam and loamy sand. The sandy loam soil was observed in the eastern side of the study area, whereas the loamy sand was observed in western and middle parts. The radon concentration levels were higher in core samples and were proportionate to the soil depth. Also they were higher in sandy loam than loamy sand soil samples. The radon concentration levels had a positive correlation with fine grains (clay- to silt-size) of soil sample which translocated from upper to lower horizons of soil during its development. Additionally, there was a positive correlation with pH and water content, whereas a negative correlation was observed with organic matter and potassium contents. The positive correlation referred to a large specific surface of fine grains which were located in lower horizons of soil and were able to adsorb more water and consequently led to high radon concentration levels