Department of Nuclear Engineering
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Item Investigative Study of Radiotoxicity of Spent Nuclear Fuel Assembly of Some Commercial Nuclear Power Plants Case Study: European Pressurized Water Reactor and Hualong One Pressurized Water Reactor(University of Ghana, 2018-07) Ojo, O.P.The European Pressurized Water Reactor (EPR) and Hualong One Pressurized Water Reactor (HPR) are two of the reactors under consideration by the Ghana Nuclear Power Programme. Radiotoxicity analysis of Spent Nuclear Fuel (SNF) assembly was carried out with these commercial Pressurized Water Reactor (PWR) nuclear power technology as case study. Burnup depletion calculation for the Uranium Oxide (UOX) fuel of these reactor technologies was simulated. Monte Carlo Neutron Particle Extended (MCNPX), a code used in nuclear fuel management analysis, was chosen in this study for the Burnup depletion calculation, being a well validated code and due to its versatile nuclei reactions cross section library. Determination of radiotoxicity for EPR and HPR SNF is the main objective of this study. The radiotoxicity was achieved taking into consideration the radioactive decay rate of the radionuclides and the Dose Factor of each radionuclide present in the SNF using the International Commission on Radiological Protection (ICRP) compendium of Dose Factors due to ingestion. The radiotoxicity for the two reactor’s SNF were compared. The initial radiotoxicity for HPR SNF was higher in the duration below one hundred years but at about a hundred years and above, the radiotoxicity was higher for EPR SNF. The radiotoxicity was tremendously reduced for the reprocessed spent UOX fuel (with the Pu and U extracted) to be used as mixed oxide (MOX) fuel. The main finding is that Pu isotopes are the major contributors to the radiotoxicity of the SNF for the two reactors systems due to their very high radioactivity, long half-lifes and high dose factors as compared to other actinides and fission products present in the SNF.Item Neutronics Analysis of Ghana Research Reactor-1 Low Enriched Uranium Core Using MCNP5 Code(University of Ghana, 2017-07) Manowogbor, V.C.The neutronic and kinetic analysis of Ghana Research Reactor-1 (GHARR-1) low enriched uranium (LEU) core was carried out using MCNP5 transport code. The changes in the fuel enrichment from 12.5 % to 13.0 % and some components such as the type of fuel, cladding material which have direct influence on the neutronic parameters, require re-evaluation of the neutronic safety analysis of the reactor. The analysis include reactivity, delayed neutron fraction, control rod worth, moderator coefficient of reactivity and the neutron flux distribution in the inner and outer experimental channels at half power (17 kW) and full power (34 kW). The configuration with 335 fuel pins gave the excess reactivity of 4.03 mk which is comparable to the high enriched uranium (HEU) core. The results also revealed that, the neutron flux distribution in the inner irradiation channels are also comparable to the flux distribution of the high enriched uranium (HEU) core. Based on the results presented in this study, it can be concluded that the safety analysis of Ghana Research Reactor-1 LEU core is good and reliable replacement for the HEU core.Item A Thesis Presented To the: Department of Nuclear Engineering University Of Ghana, Legon(University Of Ghana, 2018-07) Agyemang, W.M.Sodium hydroxide is one of the most important chemicals in the global chemical trade. It is the main feedstock used in the manufacture of many products used in everyday life. The production of sodium hydroxide in a country is a measure of the development of its chemical industry. In this study, some factors that influence production of NaOH from NaCl using electrolytic cell were optimized. The optimum conditions for the production of NaOH were found to be 500 SAL brine strength, 6.0cm electrode gap, 5 electrodes in both anode and cathode compartments and 80V. The pH of the catholyte obtained at the optimum conditions was 13.88 at 360.3K, 2 hours and 5.40A.Item Comparison of Neutronic Safety Parameters of Some Commercial Pwrs under Consideration for Ghana’s First Nuclear Power Plant(University of Ghana, 2017-07) Mensah, A.K.P.Ghana is presently exploring the option of including nuclear power plant technologies into the country’s electricity generation mix. As part of technology assessment, investigative studies of some neutronic safety parameters of the proposed nuclear reactor technologies are carried out and compared in this study. This study focuses on neutronic safety analysis of reactor technologies under consideration, these are; the European Pressurized Reactor (EPR), High Temperature Pressurized Reactor (HPR) and the Vodo-Vodyanoi Energetichesky Reactor (VVER). The input model of all three reactors were successfully developed and simulated. Analysis of the Reactivity Temperature Coefficients, Moderator Void Coefficient, Criticality and Neutron Behaviour at various operating conditions was carried out using the Monte Carlo N-Particle (MCNP5) code and the results referenced with values in literature. The nuclear power reactor technologies under study showed good safety inherent features. All three reactors gave negative coefficients for both increasing moderator temperature and moderator void fraction which was consistent with safety inherent features. The VVER assembly had the largest absolute value for the coefficients of reactivity from 0% to 80% void fraction as compared to the other technologies under study. Even though all technologies showed Doppler broadening with increasing temperature, the EPR had the highest absorption cross section, showing a higher safety margin.Item Analysis of Fluid-Solid Interaction Contributing to Thermal Fatigue in T-Junction Pipes of Nuclear Power Reactors using STAR-CCM+(University of Ghana, 2017-07) Bello, S.The focus of this project is on the investigation of phenomena causing degradation of specific zones of piping considering high temperature single-phase mixing in the location of T-Junction in Nuclear power plants. At these locations, thermal stratification and/or turbulent mixing are capable of generating damage-inducing thermal fluctuations of appropriate frequency and amplitude. Fluctuating stresses imposed on this section of the piping system are possible grounds of thermal fatigue failures in piping systems of nuclear power plants resulting into leakages of coolant. These stresses are produced mainly because of the temperature fluctuations that exist in regions where cold and hot streams are vigorously mixed together. A classic scenario for such mixing appears in turbulent flow via a T-junction. In this study, the purpose will be to perform a 3-D Simulation of fluid-Solid Interaction at a mixing Joint. Two different simulations of thermal mixing in T-junction of a nuclear power plant will be considered and perform thermal analyses of parameters leading to structure degradation. Pipe dimensions and flow parameters such as wall thickness and high operating temperatures difference are modeled and corresponding fluid-solid interaction‘s effect on wall thickness is investigated by using STAR-CCM+ Code for the simulations, where which fluid-flow calculations will be carried out. Thereafter, the flows inlet temperature will be interchange and another simulation conducted with same parameters so as to determine the effect in a different possible scenario. The flow characteristics and the temperatures in the pipe wall downstream are obtained using this Computational Fluid Dynamics. Simulations result and validation outputs with T-Junction experiment carried out at the FSI Test Facility, University of Stuttgart and contributions of the various investigated parameters contributing to thermal fatigue were presented.Item Computer Simulation Of Thermal-Hydraulics Of MNSR Fuel-Channel Assembly Using Labview(University of Ghana, 2013-07) Gadri, L.A.A LabVIEW simulator of thermal hydraulics has been developed to demonstrate the temperature profile of coolant flow in the reactor core during normal operation. The simulator could equally be used for any transient behavior of the reactor. Heat generation, transfer and the associated temperature profile in the fuel-channel elements viz: the coolant, cladding and fuel were studied and the corresponding analytical temperature equations in the axial and radial directions for the coolant, outer surface of the cladding, fuel surface and fuel center were obtained for the simulation using LabVIEW.. Tables of values for the equations were constructed by MATLAB and Excel software programs. Plots of the equations with LabVIEW were verified and validated with the graphs drawn by the MATLAB. In this thesis, an analysis of the effects of the coolant inlet temperature of 24.5 ℃ and exit temperature of 70.0 ℃ on the temperature distribution in fuel- channel elements of the reactor core of cylindrical geometry was carried out. Other parameters, including the total fuel channel power, mass flow rate and convective heat transfer coefficient were varied to study the effects on the temperature profile. The analytical temperature equations in the fuel channel elements of the reactor core were obtained. MATLAB and Excel software were used to construct data for the equations. The plots by MATLAB were used to benchmark the LabVIEW simulation. Excellent agreement was obtained between the MATLAB plots and the LabVIEW simulation results with an error margin of 0.001. The analysis of the results by comparing gradients of inlet temperature, total reactor channel power and mass flow indicated that inlet temperature gradient is one of the key parameters in determining the temperature profile in the MNSR core.Item Effects of Wall Roughness on Flow Stability Analysis of Supercritical Heated Channel(University Of Ghana, 2015-07) Nkansah, F. S.The world‟s population growth is increasing rapidly and requires a corresponding growth in electric energy production. The current worldwide electricity sources, consists of approximately coal 41%, gas 20%, oil 6%, nuclear 15%, and hydro and renewable together 18% [1]. For the world to support its population there must be an increase in the use of energy supplies that are clean, safe and cost-effective. Prominent among these supplies is nuclear energy. The need to produce energy that is clean, safe and cost-effective led to the formation of a framework for international cooperation known as Generation -IV International Forum (GIF) [1]. This gave rise to future generation of nuclear energy systems, known as Generation IV (Gen IV) which further enabled six nuclear systems to be selected for consideration to assist in meeting the energy needs of the world. The Supercritical Water Reactor (SCWR) [2-4] is one of the six reactors under consideration in the GIF network. The supercritical reactor which is yet to be constructed has been proven from design to be clean, safe and reliable.Item Entrepreneurial Disposition and Culture: a Case of Graduates of Accra Polytechnic(University Of Ghana, 2016-06) Chiri, N.It is true that globally unemployment in general and graduate unemployment in particular is scaling, most especially in developing economies such as Ghana. Entrepreneurship has been seen as one of the means to solving this unemployment menace. However, culture has been identified as one of the major factors that influence the entrepreneurial intent of people. This study therefore, sets out to gauge the impact of Ghanaian culture on the entrepreneurial disposition of Higher National Diploma (HND) graduates of Accra Polytechnic who graduated between 2007 and 2012. The study adopts qualitative research approach. Face – to – face and telephone interviews were used to gather data on 46 graduates of the polytechnic. Sampling was by means of snowball and convenience techniques. Thematic and narrative analysis techniques were adopted for data analysis. The study found that, collectivism/collectivistic ethic culture has negative effect on capital accumulation, human resource management, and the urgency unemployed graduates attached to the efforts leading to entrepreneurship. Lack of start – up capital largely due to inability to accumulate funds, and the failure of the financial institutions to support new ventures is also affecting the entrepreneurial intents of the graduates. Based on the above listed and other findings, the study made the following recommendations; students should endeavour to cultivate the habit of pooling resources together, institutions established by the state to engender entrepreneurship among graduates must foster close collaboration with the training institutions, also the training institution (Accra Polytechnic) must closely collaborate with industry, most especially the financial institutions.Item Investigating the Thermal Hydraulic Performance of Combined Split and Swirl Vanes Using Star-CCM+(University Of Ghana, 2017-07) Dedzie, S.For effective evacuation of heat from nuclear fuels and increasing the Critical Heat Flux (CHF) of nuclear fuel bundles, mixing vanes are attached to spacer grids in fuel assemblies. However, the presence of spacer grids increases the pressure drop across the fuel bundle which has economic implications on the operations of Nuclear Power Plants (NPPs) in general. Nuclear fuel vendors are therefore continually improving upon the designs of mixing vanes in order to improve the thermal hydraulic efficiency of fuel assemblies. Numerical simulation was conducted in this study to analyse the thermal hydraulic performance of a 1200 mm long 5 5 fuel assembly supported by split and swirl vanes at varying spacer gaps of 350 mm and 530 mm. This numerical simulation was performed using STAR-CCM+ CFD code. The Shear Stress Turbulence (SST) was adopted for a single phase (liquid) isothermal coolant in this study. The objective of this study was to validate the simulation results with experimental data obtained from the Korean Atomic Energy Institute. The present study also investigated the effects of spacer gaps and mixing vanes on the velocity and turbulence of the flow through the fuel bundle. Validation of split vane data of all velocity components showed good correlation with experimental results; however simulation data of the swirl vane showed poor correlation with experimental results. The split vane produced a higher effect on the turbulence of the flow than the swirl vane. Also the 350 mm split-swirl fuel bundle produced a higher turbulence than the 530 mm split-swirl arrangement. Also the 530 mm swirl-split fuel bundle had a higher effect on turbulence than the 350 mm swirl-split vane arrangement. In effect the split-swirl 530 mm produced the highest turbulence than the swirl-split 350mm, swirl-split 350 mm and swirl-split 530 mm fuel bundles.Item Remediation of Surface Water Polluted by Effluent Discharges from Mining Activities in the Eastern Region of Ghana(University of Ghana, 2017-07) Kusi, S.Heavy metals are very toxic to the environment and humans at large. Exposures to heavy metals have significant health disorders. In this research, the mandate to find novel adsorbent to reduce lead and mercury concentrations from water samples from Birim River in the Eastern Region of Ghana was studied. The turbidity of the water samples from Kibi, Anyinam and Kade indicated that, the river is very turbid (an average of 355 NTU) and therefore not recommended for domestic use without treatment. The modification of rice husk and orange peels with tartaric acid showed that modified rice husk had better binding efficiency for Pb and Hg. A series of batch experiments using tartaric acid modified rice husk (RH-TAM), tartaric acid orange peel modified (OP-TAM), unmodified rice husk (UM-RH) and unmodified orange peel (UM-OP) for the removal of Pb and Hg showed that the sorption processes depended on pH, contact time and adsorbent dosage. A pH of 5 with 0.5 g/20 ml of adsorbent solution maintained at a temperature of 35 o C ± 2 for a period of four (4) hours yielded the highest adsorption efficiency for both modified and unmodified adsorbents. The adsorption efficiencies recorded for RH –TAM and UM-RH were 75. 56 % and 69.93 % respectively for Pb. Similarly, Hg adsorption efficiencies for both RH-TAM and UM-RH were 53. 26 % and 45.11 % respectively. The adsorption efficiencies of OP –TAM was 62.03 % for Pb and 44.57% for Hg. The unmodified orange peel (UM-OP) had the least adsorption efficiencies of 51.88 % for Pb and 42.39% for Hg. The Langmuir isotherm fitted the experimental data for Pb and Hg better than the Freundlich isotherm.
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