Dissertations

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A study of electrical insulation materials developed using selected clay minerals in Uganda
(Kyambogo University [unpublished work], 2012-06) Nasejje, Stella
This study was to investigate appropriate mixtures of different ceramic mineral ingredients needed to make electrical porcelain insulators and to determine the best method of developing the electrical insulator of slip casting, dry pressing, and wet pressing. The mixing of the clay minerals was done using percentage ratios of ball clay. kaolin, feldspar and flint of which the quantity of flint was kept constant at 20% in all compositions and that of ball clay to kaolin changed through a range of 1:1.75 , 1:2 and 1: 2.5, well as that of feldspar took up any remaining percentage. These samples were formed by slip casting. Wet, and dry pressing and then tired at a constant heating rate to a temperature of l 250°C. Then the dielectric strength was tested using the oil test set, Avo Megger foster OTS100A F/2. The mixtures of the clay minerals with a ratio of ball clay to kaolin of 1:2 showed good formability in all forming methods, but those with a ratio of 1:1.75 and 1:2.5 could not easily form good casted and wet pressed samples. The best formulation was that with 55% clay, where the ratio of ball clay to kaolin was 1:2. The sample compositions of the various, minerals were found to affect both voltage breakdown and dielectric strength. The voltage break clown. V was found to be proportional to the thickness. t of the samples according to the expression V= at + b: where a and b are constants of testing conditions like room temperature and frequency. Conversely, the values of dielectric strength; U was found to be inversely proportional to the thickness, d of the samples according to the expression; D = VB over d where VB is the breakdown voltage and d is the thickness of the sample. Values of both the voltage breakdown and dielectric strength of samples tested in air were much lower than those of samples tested in transformer oil due to generated carbon around them when in air as a result of corona discharge. The samples tested in transformer oil had values above 10kV/mm. Thus, the electrical insulation properties of the formulation of the samples developed in this study were found to match that required for international standards.
Mechanical properties of ceramic floor tiles made from selected minerals in Uganda
(Kyambogo University [unpublished work], 2012-06) Ochen, William
This study was designed to produce porcelain floor tiles using raw materials found in Uganda and to determine mechanical properties of the tiles produced. The properties were then compared with South African National Standards. Porcelains are made of clays, kaolin, feldspar and sand. In this study, the raw materials were mixed in proportions of 40-60% clays, 30-40% feldspar and 10-30% sand. The tests carried out include shrinkage, strength, water absorption and chemical analysis. Samples were pressed at 30MPa with 12% moisture content by weight. Firing was at peak temperatures of 1050, 1100, 1150, 1200 and 12500C. Firing process involved heating dry samples from room temperature to 1050C at 1000C/hr, after 2 hrs of holding the rate was then raised to 3600 C/hr and soaked for 1 hr at peak temperatures. Samples were left to cool naturally in the kiln for 16 hrs. Chemical analysis of the minerals by XRF method revealed that kaolin had an alumina content of 24.9 (wt %) whereas sand had silica at 95.0 (wt %). Iron oxide which influences the color of samples was high in ball clay at 3.2 (wt %). Maximum strength of 34MPa was exhibited by composition 2 at 12500C with linear shrinkage of 9.1 % and water absorption of 0.0 (wt %). South African National Standards classifies tiles whose strength is above 30MPa as B1. All samples fired in the temperature range of 1100 to 12500C exhibited properties in the range recommended by SANS both in strength and water absorption for flooring as B1 to B4 tiles. Minerals from the studied deposits yielded high grade ceramic floor tiles recommended by SANS for flooring. No cracks were exhibited by samples fired at 1100 to 12500C
Intensity of secondary scattered x-rays during x-ray diagnostic procedures in selected diagnostic centres in Uganda
(Kyambogo University[unpublished work], 2014-01) Byaruhanga, Bonaventure
The purpose of the study was to investigate the intensity of secondary scattered X-rays when different body regions; the chest, the abdomen and the lower limbs were exposed to X-rays during radiography. The study used experimental design where the secondary scattered X-ray dose from three diagnostic centres in South Western Uganda were measured us.ing TLDs that were worn at the back of the radiographer. The cards were then read monthly and the process repeated for a period of six months. The number of patients exposed to X-rays for each procedure for the same period was also noted. From the study, it was found that the limb exposures constituted the highest proportion of the patients X-rayed (42%), followed by the chest· (35%) and finally the abdomen (23%). In addition, it was found that the chest exposures generally lead to the highest intensity of secondary scattered X-rays to the radiographers which was 2,670 mSv, 2,756 mSv and 2,505 mSv for Mutolere Hospital, Goodwill Imaging Centre and Mbarara Diagnostic Centre respectively. The limbs contributed the second highest intensity of secondary scattered X-rays (2,442 mSv) at Mutolere Hospital, though generally the abdomen contributed the second highest secondary scattered X-rays (1,712 and 1,294 mSv for Goodwill and Mbarara Diagnostic Centre respectively). The limbs contributed the lowest intensity of secondary scattered X-rays in Goodwill and Mbarara Diagnostic Centre i.e 1,578 and 1,236 mSv respectively. In relation to the safety standards set by the International Atomic Energy Agency ( IAEA, 2002), the predicted cumulative annual dose to radiographers from Mutolere Hospital, Goodwill Imaging Centre and Mbarara Diagnostic Centre are 13,704, 11,964 and 10,692 mSv respectively. These values are below the annual dose limit of 20 mSv for radiation worker as recommended by IAEA (IAEA, 2002). This means that the radiographers from the three diagnostic centres are at a low risk of developing stochastic health effects. However, the annual dose from the diagnostic centres could be dangerous if radiographers are exposed over many years in a lifetime.
Specific activity levels of radionuclides in spring water, selected plants and soils along Nakivubo channel
(Kyambogo University[unpublished work], 2014-01) Kukiriza, Grace
There is an increase in the number of industries that discharge their effluents into Nakivubo channel. It is possible that some of the industrial effluents may contain radioactive nuclides since they are widely used in hospitals, research laboratories, industries and construction for diagnosing and treating illnesses, sterilizing equipment. All these processes deposit radio-nuclides into the environment if not well handled contaminating the soil and plants grown on the soil. This in turn affects people when they ingest these crops leading to cancerous risks. This study determined the Specific activity levels of the radio-nuclides present in spring water, selected plants and soils along Nakivubo Channel and its tributaries. The study was experimentally carried out using a Gamma Ray Spectrometer consisting of a 7.5 em Nai(T1) GDM 20 detector used for analyzing radio-nuclides in the samples for a period of about 5000s. The spectral peaks of the radio-nuclides present in the samples were noted and their specific activity calculated. The radio-nuclides observed in the samples are: Uranium (U-238), Thorium (Th-232) and Potassium (K-40). The highest specific activity was mainly due to K-40 with a mean value of 201162 ± 448 Bq/kg, followed by Th-232 with a mean activity of 72,7 ± 8,5 Bq/kg and the lowest was due to U-238 with a mean activity of 34,4 ± 5,9 Bq/kg. This is in agreement with a study by Anguma ( 1999) in water, fish and water hyacinth in Lake Victoria and Kyoga where K- 40 was more abundant with a mean activity of 610 Bq/kg and the lowest mean activity levels due to U-232 of 17 Bq/kg. From the results obtained, the concentrations of the radio-nucleoside identified in the samples were within the tolerance limits and therefore the people who consumed these food crops are hardly at a high risk of developing stochastic health effects unless if they are consumed over a lifetime. However, a study investigating the concentration of radio-nuclides in sugarcane fibre be carried out. A study to ascertain the annual consumption of the radio-nuclides in foods like yam and sugarcane, spring water along Nakivubo channel and its tributaries be carried out to identify any risks if any. A high purity Germanium Spectrometer can be used in this study to improve on the
Gamma ray activity levels and radiological hazard indices of Radionuclides in mine tailings from selected mines in Southwestern Uganda.
(Kyambogo University [unpublished work], 2016-01) Turyahabwa, Evarist Rutahweire Silver
This study was designed to determine and compare the specific activity levels and the radiological hazard indices of gamma ray emitting radionuclides in mine tailings from three selected mines in Southwestern Uganda. This was achieved by analyzing 72 soil and rock mine tailing samples using the GDM 20 Nal(TI) detector. The specific activities of the principal primordial radionucides of 238U, 232Th and 4°K in the samples were measured. The values obtained were used to determine the absorbed dose rates, the annual effective dose rates, the radium equivalent activity, external and internal hazard index and the excess lifetime cancer risk. The mean specific activities of 238U, 232Th and 4°K in mine tailings at 90% confidence level ranged from 23±14 Bqkg-1 to 59±16 Bqkg-1 for 238U, 49±39 Bqkg-1 to 244±19 Bqkg-1 for 232Th, and 226±232 Bqkg-1 to 893±167 Bqkg-1 for 4°K. The mean outdoor and indoor absorbed dose rates in air for Mashonga, Kikagati and B utare were (181±36 nGyh-1 and 338±67 nGyh-1 ), (167±23 nGyh-1 and 310±47 nGyh-1 ) and (192±16 nGyh-1 and 355±32 nGyh-1 ) respectively for waste soil samples and (67±50 nGyh-1and 127±102 nGyh-1 ), (85±37 nGyh-1 and 159±80 nGyh-1 ) and (115±33 nGyh-1 and 215±66 nGyh-1 ) respectively for waste rock samples. The ratio of the mean indoor to outdoor absorbed dose rates in all the samples was 1.9 but this was 36% higher than the world average. The total annual effective dose rates, radium equivalent activities, external and internal hazard indices for waste soil samples were above the maximum permissible limits recommended for members of the public. Potential radiological hazards on miners and the people living in the neighborhood of the sites due to external irradiation are significant. There is need to improve waste management practices in the mining sites in order to prevent health hazards associated with the radionuclides in the mine tailings.
A study of upland clay from ant-hills as a refractory material.
(Kyambogo University [unpublished work], 2016-01) Wamaholo, Elizabeth
This study was purposed to investigate the suitability of upland ant-hill clays for fabricating refractory bricks. The chemical composition of the anthill clay was determined using the Atomic Absorption Spectrophotometer (GBC SavantAA) and X-Ray Spectrometry. The chemical analysis revealed the presence of the elements which included; alumina, silica, iron oxide, titanium oxide, potassium, sodium, calcium, organic carbon, phosphate, zirconium, strontium, cranium, rubidium, magnesium, manganese, copper, zinc, yttrium and nitrogen. Wet and dry pressed samples were obtained by using the hydraulic press with a die mould (Hydraulina Laboratory Manual press- PW40) and slip casted samples were formed using a metallic brick mould. All dry pressed samples were found to be structurally inadequate due to development of strata, formation of cracks after firing. The wet pressed and slip casted samples were fired at a heating rate of 2°C/minute to a temperature of 534°C and held at this temperature for lhour then heated to 1150°C at a rate of 6°C/minute and held for 1 hour and then allowed to cool in the furnace at a rate of s°C/minute. All Samples fired at 11 S0°C were successfully retrieved and had no cracks or any other deformities. The Modulus of rupture was determined using the three point loading method (LLOYD INSTRUMENTS). Thin wet pressed fired samples had high MOR average values of 13826.08KPa for Nkombe, 1963.43KPa for Namagunga and 1510.23KPa for Kyambogo. The slip casted fired samples had an average MOR of 31.60Pa for Namagunga and 1l7.74Pa for Kyambogo. These suggested that sample forming methods have an effect on the modulus of rupture. The average MOR of the wet pressed fired samples of upland ant-hill clay was found to match that recommended by ASTM (American Society for Testing and Materials) standards for refractory materials and the percentage of the alumina in upland ant-hill clay showed quite close compliance with ASTM standards. This therefore means that based on the findings above, upland ant-hill clay is suitable for refractory materials.
Performance of ceramic candle water filter made from selected local clays in Uganda
(Kyambogo University [unpublished work], 2016-01) Onyait, Justine
The focus of this study was to developa ceramic candle filter using local clay and mahogany saw dust and determine its filtration rate and E-coli removal efficiency. The candle filters were developed using ball clay from Ntawo mixed with mahogany saw dust of particle size less than 1mm. Five different clay- saw dust ratios were used in the production of the filters by weight of 1: 1, 5:4, 5:3, 5:2, and 5:1. The highest porosity of 48.05% was obtained in a filter sample with the highest saw dust proportion (1: 1) while the lowest porosity of 35.12% was obtained in a filter sample with the lowest saw dust proportion (5: l). Higher removal efficiencies of contaminants (99.9%) were observed in filter samples with low saw dust proportion (5:1). Ceramic candle filter (CCF) with clay to saw dust proportion of (5:1) was more effective in reducing turbidity, reduced turbidity to< 1 NTU. The candle filter with the lowest saw dust proportion (5:1) produced the lowest filtrationrate of water (196.43 ml hr-1) and the filter with highest saw dust proportion had the highest filtration rate of water (917.67ml hr-1). From this research, it can be concluded that filters with higher initial filtration rates are more porous than those with low filtration rates. It can also be concluded that the filters were capable of filtering the turbidity of the water and filter samples also decreased the concentrations of microbial contaminants, therefore making the water safe for consumption. Its recommended that further studies be carried on; the effect of grog on cohesive nature of the filter, flow rate of the water, turbidity of water, and total coliform removal of the filter. The effect of the application of colloidal silver on the adsorptive properties of the filter material and consequently on the quality of water should equally be explored.
Thermal conductivity of fired clay of varied mineral composition made from selected Uganda clay types
(Kyambogo University [unpublished work], 2016-01) Kella, Allan
The use of thermal insulators is one of the most important applications in thermal energy conservation systems. This study determined the effect of varying mineral compositions on thermal conductivity. Dry powders of kaolin, ball clay, quartz and feldspar were prepared by ball milling, sieved to particle size of 45μm and then mixed in different proportions to make 100g. For each formulation, three of the four minerals were kept in fixed proportions by mass while varying one. Eighty clay rectangular shapes of dimensions 100mm x 50mm x 20mm were compressed at a pressure of 75MPa and then fired to a maximum temperature of 1200°C. The first formulation had the proportion of Quartz varied while that of other minerals fixed. The second formulation had the proportion of Ball clay varied while that other three fixed. The third formulation had the proportion of feldspar varied while that other three fixed. The forth formulation had the proportion of kaolin varied while that other three fixed. And the fifth formulation had the proportion of all the minerals varied. The Quick thermal conductivity meter was used in the measurement of thermal conductivity at room temperature of approximately 25°C. The study showed that thermal conductivity value increased with increasing proportion of Quartz from 3.305x10-1 to 3.32x10-1 Wm-1K-1. Thermal conductivity values also increased with decreasing proportion of ball clay from 3.225x10-1 to 3.267x10-1Wm-1K- 1. The thermal conductivity value increased with increasing proportion of Feldspar from 3.313x10-1 to 3.274x10-1 Wm-lK-1. The thermal conductivity value increased with decreasing proportion of kaolin from 3.179x10-1 to 3.28x10-1 Wm-lK-1. And when all the mineral proportions was varied, The thermal conductivity value increased with decrease in proportion of kaolin and ball clay in each mixture, and ranged from 3.239x10-1 to 3.288x10-1 Wm-lK-1. From the samples studied, formulation consisting of (Quartz-15%, Ball clay-15%, Feldspar- 15%, and Kaolin-55%) was the best insulating material with thermal conductivity value of 0.3179 Wm-lK-1. The highest thermal conductivity values was due to high proportions of quarts, while the lowest thermal conductivity values was due to high proportions of kaolin. The study recommended further work to be done on thermal conductivity of clays by varying pressure, particle size, firing temperature and the impact of combustible organic wastes on the thermal conductivity.
Gamma radiation exposure levels due to radionuclides in soils from selected gold mines in Karamoja
(Kyambogo University(unpublished work), 2016-01) Chelangat, Kadafi
The aim of this study was to determine radiation exposure levels due to gamma ray emitting radionuclides in soils from selected gold mines in Karamoja and the associated hazard indices. The people of Karamoja use poor methods of mining gold, therefore they are exposed to ionizing radiation of unknown concentrations. In this study, 60 samples from Rupa, Nakabaat, Morulem, Acerer, Nabulatuk and Morita were analysed using a Nal (TI) gamma-ray detector. The activity concentrations of natural radionuclides 226 Ra, 232 Th, 238 U and 4° K in soils were measured by gamma spectroscopy using sodium iodide detector. In addition, radiological assessment due to these radionuclides was also carried out. To ensure quality control, the samples collected from the sites were transferred to polythene bags, labeled and double-bagged. They were transported in boxes whose background radiation emissions were measured with an identifier. The average activity concentrations of 226 Ra, 232 Th, 238 U and 4° K were 49.26 ± 1.58, 44.29 ± 0.74, 16.57 ± 0.40 and 599.64 ± 7.33 Bqkg-1 respectively. The mean absorbed dose rate was 50.44 ± 1.48 nGhr-1 which is below the world average dose rate of 60 nGhr-1 • Radium equivalent values for the area studied ranged from 83 .83 ± 2.33 to 186.12 ± 3.52 Bqkg-1 with mean of 117.22 ± 2.30 Bqkg-1 which is below the world average of 370 Bqkg-1 • The mean external and internal hazard indices were both below unity. Therefore, though the results in the study indicated higher levels of natural radionuclides in soils of Karamoja region than the world average values, the mining activities pose no significant radiological hazard to the population and the soils from these areas can be safely used for construction purposes. The observed unprofessional practices such as lack of use of gas masks while working in the dust-filled mine caves could expose workers to possible risks from inhalation of respirable crystalline silica and radon gas; therefore miners must be educated and sensitized on the effects of exposure to radiation by the Atomic Energy Council of Uganda. These can be done by introducing Safety and Health awareness days. People of Nabulatuk and Acerer in Nakapiripirit district where concentrations of radionuclides are twice the world average levels must be advised to reduce on the time they spend in mines.
Natural radioactivity levels and radiological hazard indices of soil and water collected from Kaserem limestone quarry, Kapchorwa district, Uganda
(Kyambogo University (un published work), 2017-10) Chukondo, Geofrey
This study was to determine the gamma ray concentration/activity due to naturally occurring radionuclides present in soil and water from Kaserem limestone quarry area in Kapchorwa District and the associated hazard indices. Reports from other studies associate limestone deposits with high concentration of radionuclides and therefore data regarding these radionuclides is useful in protecting the public from radiation exposure and minimizing risks. In this study, fifty (50) soil samples and ten (I 0) water samples collected from the quarry area were analyzed, with the aid of gamma spectroscopy method, using Sodium Iodide Thallium, NaT (TI) detector. The radiation parameters included radiation equivalent activity, gamma absorbed dose rate, annual effective dose and external and internal hazard indices in soil and water samples from Kaserem limestone quarry. To ensure quality control, the soil samples collected from the sites were transferred to polythene bags, labeled and double-bagged. They were then transported in boxes whose background radiation emissions were measured with an identifier while water samples were put in plastic water bottles and sealed before transportation to the laboratory. Naturally occurring radionuclides (NORM) present in soil and water samples were identified. The specific activity concentrations of 226Ra, 232Th, 238U and 4°K in soil samples are: 75.71 Bq kg·\ 77.01 Bq kg·', 41.07 Bq kg· ' and 536.9 Bq kg·', respectively. These natural activity values were higher than the maximum permissible world average values; hence this area should be considered high background radiation area (HBRA) and the activity concentration of 226Ra, 232Th, 238U and 4°K in water samples was 104.18 Bq kg· ', 16.58 Bq kg· ', 19.27 Bq kg·' and 22.73 Bq kg·', respectively. The average absorbed dose rates were found to be 106.39 nGy h· ' for soil samples, which is about 2 times the world average of 60 nGy h· ' ; While for water samples it was 56.44 nGy h· ' which is similar to the world average absorbed dose rate of 55 nGy h- 1 • Assuming 33% occupancy factor, the annual average effective dose rates (AED) were calculated for human exposure to gamma radiations from the radionuclides in soil and it was found to be 0.31 mSv y"1 which is below International Commission on Radiation Protection (ICRP) limit of 1 mSv y·' for exposure to members of the general public, while the value for water samples was 0.18 mSv y"1 which was above the reference value of0.12 mSv y" 1 . While the mean radium equivalent values for soil and water samples were: 227.17 Bq kg· ' and
Radiological hazard levels by the gamma ray emitting naturally occurring radioisotopes in selected fish species of Lake Albert in Uganda
(Kyambogo University (un published work), 2017-10) Kayanja, Jimmy
A study was conducted for natural radioactivity in some fish samples from Lake Albert, shared by five riparian districts namely Ntoroko, Kibaale, Hoima, Buliisa and Nebbi, located in the western part of the great rift-valley. Radioactivity is a phenomenon that leads to production of ionizing radiations and these are known to trigger or induce cancer. The fish were analyzed to estimate the radioactivity (activity) concentrations due to natural radionuclides Thorium (232Th), Radium (226Ra) and Potassium (4°K). The Gamma ray spectrometry technique was used in the spectral collection and analysis of the prepared fish samples using the Thallium activated Sodium iodide scintillator (Nal (TI)), GDM 20. The detector produced readings of Standard Deviation (S .D), Full Width at Half maximum (FWHM) in keV, Rate(R), number of radionuclides (n) in each peak interacting with the crystal and live time (t) in seconds from which the raw data was obtained for the computation of the Activity concentrations, Dose Rates, Annual Effective Dose and Radiological Hazard Indices due to 232Th, 226Ra and 4°K in fish samples using mat lap program and Microsoft excel 20 I 0 (spread sheet) The result of this study showed that the act1v1ty concentrations of 232Th ranged from 3.27±0.29Bqkg· 1 to 7.64±0.46Bqkg"1 with an average concentration of 5. I 6±0.37Bq/kg, 226Ra ranged from 27.22±2.13Bqkg"1 to 41.75±2.69Bqkg·1 with a mean of 33.10±2.41 Bqkg-1 and 4°K ranged from 392.52±11.07Bqkg-1 to 465.64±13.0IBqkg-1 with a mean value of 435.16± 12.0 !Bqkg-1.According to the results obtained in this study, mean activity concentrations of the radionuclides increased according to the order 232Th < 226Ra < 4°K and these were lower than the worldwide maximum permissible values of 50, 50 and 48 1 Bqkg·' respectively for 232Th, 226Ra and 4°K in fish. The absorbed dose rate for 232Th in all the species analyzed ranged from I .593nGyh·1 to 3.495nGyh· ' with the average value of 2.485nGyh-1 . For the dose rate due to 226Ra radioisotope in the fish species ranged from 15 . l 85nGyh·1 to 2 I .73?nGyh with the average value of I 8.454nGyh-1. Also the dose rate due to 4°K radioisotope in the species ranged from 16.368nGyh·' to I 9.335nGyh·1 with the average value of I 8.149nGyh-1 All of these values
Investigation of the compressive strength of ntawo ball clay fired to different temperatures at different rates of temperature rise
(Kyambogo University (un published work), 2017-12) Byekwaso, Ronald
This study was to investigate the compressive strength of fired Ntawo Ball Clay found in Mukono District in Central Uganda. The clay sample was first analyzed using X-ray Diffraction Spectrometer Model RIX3000 to determine the relative abundance of the chemical components and then compressive strengths were determined. Ball clay of particle size 45.0 μm was used to produce 150 rectangular clay slabs fired in an electric furnace, model P59 l 0. They were then subjected to compressive strength test by first determining the breaking force for each sample using a compressive test machine, compact 500Sn-12994917 on samples fired at different rates of temperature rise, ranging between 2°C min- 1 and 6°C min-1 in intervals of 1°C min-1 for set firing temperatures. The compressive strength tests were then carried out on another set of samples fired at set rates of temperature rise to different firing temperatures ranging between 500°C and I 000°C in intervals of I 00°C. The compressive strength of fired tawo ball clay was found to decrease with increase in rates of temperature rise between 2°Cmin-1 and 6°Cmin-1 for the six firing temperatures. For temperatures of 500°C to I 000°C in intervals of I 00°C, the percentage decrease in compressive strength ' ere 11 %, 3%. 3%. 8%, 2.9%, and 11 % respectively. At a level of significance a = 0.05 and a = 0.0 I, it was established that compressive strength was related to the rate of temperature rise. The study further revealed that compressive strength increased with increase in firing temperature. The percentage increase was 279%, 273%, 247%, 257% and 279% for the rates of temperature rise between 2°Cmin-1 and 6°Cmin-1 respectively, overall average percentage increase being 267%. At a level of significance a= 0.05 and a = 0.0 I, compressive strength depended on firing temperature ntawo clay was found to be composed of mainly silica (67.20%), alumina ( 18.20%), ferrous oxides (2 .83%) and other fluxing oxides such as CaO (0.31 %). K20 (0.98%), and a20 (0. 19%), among other compounds. The compressive strength of fired samples decreased with increase in rates of temperature rise during firing between 500°C and I 000°C. Other investigations should be made to find out the effect of firing beyond I 000°C and firing at a rate above 6°C min1 on the compressive strength, and the effect of changing the mineralogical composition of clay on the compressive strength.
Investigation of the compressive strength of ntawo ball clay fired to different temperatures for different holding times
(Kyambogo University (un published work), 2017-12) Isabirye, Jeromy Moses
This study focused on ball clay from ntawo deposit from Mukono District, in central Uganda with respect to its compressive strength. The chemical compounds by percentage weight were determined using RIX 3000 Spectrometer machine. The compressive force was determined by SOOS -1299417 machine. One hundred and fifty samples of Ntawo ball clay fired from 500°C to I 000°C at intervals of I 00°C were used to find out how holding time affected compressive strength for each set firing temperature. The same number of samples were used to investigate how the compressive strength of fired tawo ball clay to find out how they were affected by firing temperature for each set holding time between 20 minutes and 60 minutes at intervals of I 0 minutes. The tawo ball clay was found to contain 67.2% of silica, 18.2% of alumina, 2.83 % of Fe203 and 1.84% of fluxes. The compressive strength decreased from 4.2% to 0.4% withholding time for firing between 500°C and 800°C. The compressive strength variation was negligible, less than I% for temperatures beyond 900°C to I 000°C. The highest compressive strength was 25.45 MPa, obtained by firing to a temperature of I 000°C. In all cases compressive strength increased by 298±7 % for all firing temperatures at each of holding times of 20, 30, 40, 50 and 60 minutes respectively. The compressive strength of ball clay beyond 800°C does not need longer holding time. It was further established that the compressive strength of fired clay depended on holding time when fired to various firing temperatures and the compressive strength of fired clay depended on firing temperature when the firing is held for holding time were tested at ex:= 0.01 and ex:= 0.05 levels of significance. The compressive strength for ball clay fired above 1000°C and holding time exceeding 60 minutes is worth investigation in order to find out whether any change in the mineral compounds of ball clay affect the above results.
Activity levels of gamma ray emitting radionuclides in food crop samples in selected tobacco farming areas in Aura and Maracha districts
(Kyambogo University (unpublished work), 2017-12) Anguani, Epiphany Mike
The farming activities, especially Tobacco production in Terego East and Terego West in Arua district and Maracha East County in Maracha district employ fertilizers such as NPK, DAP, CAN, TSP and UREA to enhance soil fertility property and to increase Tobacco production. Fertilizers are known to contain radionuclides such as uranium, radium, potassium etc., that originate from phosphate rocks; that could accumulate in the soil over the years and these may be absorbed by food crops grown on such soils. Humans who feed on these food crops may then absorb such radionuclides. As Human cells absorb radiation energy, molecules in them get damaged resulting into malfunction of cells through genetic mutation and this can then be a health risk. in this study the specific activity levels of gamma ray emitting radionuclides in selected food crop samples (maize, rice, sorghum, cassava, ground nuts, beans and simsim), grown in soils contaminated by fertilizers was determined using Gamma ray spectroscopy technique, that uses Nal(Tl) detector. The samples were obtained from the six Sub Counties of Omugo, Aii-vu, Odupi, Oriama, Katrini and Bileafe in Arua District and three Sub Counties of Tara, Yivu and Nyadri in Maracha District. The sampling technique used was purposive and simple random. In summary, the mean specific activity levels of radium, thorium, uranium and potassium were 64.0 Bqkg·1 , 6.0Bqkg·1, 3.5 Bqkg·1 and 185.1 Bqkg·1 respectively, in the crop samples considered. The mean specific activity levels for potassium was the highest, followed by radium, thorium ·and the least level shown by uranium. The mean absorbed dose rate was 40.9 nGy/h and the mean annual effective dose rate was 0.1 mSv/yr., for all the crop samples considered. The mean annual effective dose rate for all crop samples determined in this study were within the range recommended by the International Atomic Energy Agency as having no observable effects in the human body. Therefore it is recommended that consumption of the food crops investigated should continue as it poses no potential radiation hazard. It is further recommended that investigation should be performed on other crops which are not investigated in this study.
Infra-red reflectance and transmittance by thin film coatings of some selected metals on glass substrate
(Kyambogo University(unpublished), 2018-11-14) Kamwasir Hellene
Reflection and transmission of light serve as key parameters in thin films coatings meant for temperature regulation in warm climates. In this study, the infrared reflectance and transmittance for three different thicknesses of thin films of palladium and platinum were determined. The thin films were made by thermally evaporating various masses of the platinum and palladium on glass substrates. A Shimadzu UV-VIS-NIR Spectrophotometer was used to determine the reflectance and transmittance of the samples from which the spectra were determined. Ex situ measurements, using Point wise Unconstrained Minimization Approach (PUMA) were made to determine the exact thicknesses of the films. Reflectance was found to vary with film thickness. The results showed that the 60 nm film of palladium had a maximum reflectance of 33%, 140 nm film, a maximum reflectance of 39% and 230 nm film, a maximum reflectance of 72%. For platinum, the 140 nm film had a maximum reflectance of 28%, 146 nm film a maximum of 35% and 395 nm film a maximum reflectance of 42%. In all the cases, the reflectance in the infrared part of the spectra (800-2500 nm) was higher than in the visible region which suggests that palladium and platinum thin films may be used as heat mirrors. The transmittances of palladium and platinum thin films were high (over 80%) an indication that the thin films probably had voids. The study also showed that for the same thickness of palladium and platinum films (Palladium film of 140 nm and platinum film of 140 nm), palladium has greater reflectance than platinum showing dependence of reflectance of thin film on material used for its fabrication.
Determination of radiological hazard levels in soil, mine tailings and rock samples from selected gold mines in Busia district, Uganda
(Kyambogo University(unpublished), 2018-11-15) Eling, Jimmy
This study was designed to determine radiological hazard levels in soil, mine tailings and rock samples from Agata, Okame, Busia 90 and Greenstone Resource Limited Gold mines in Busia District. The specific activity of the radionuclides were determined using Nal (Ti) scintillation detector and the values were then used to determine the radiological hazard parameters due to radionuclides in the samples from the mines under study. The specific activity of 238U in soil, mine tailings and the rock samples from the four gold mines ranged from 18.7 Bqkg-1 to 27.9 Bqkg-1 , 7.4 Bqkg-1 to 13.2 Bqkg-1 and 1.7 Bqkg-1 to 27.8 Bqkg-1 respectively. The specific activity of 232Th in soil, mine tailings and rock samples from the mines ranged from 60.8 Bqkg-1 to 98.8 Bqkg-1 , 25.1 Bqkg-1 to 32.7 Bqkg-1 and 2.3 Bqkg-1 to 66.6 Bqkg-1 respectively while that of4°K in soil, mine tailings and rock samples ranged from 53.6 Bqkg-1 to 211.8 Bqkg-1 , 5.7 Bqkg-1 to 217.3 Bqkg-1 and 2.1 Bqkg-1 to 120.1 Bqkg-1 respectively. The Specific activity values of 232Th in soil sample from each of the four gold mines were above the worldwide average value of 30 Bqkg-1 . It is only Greenstone mine tailings and Okame rocks that had higher activity for 232Th than the world wide average value. The Absorbed Dose rates in soil, rock and mine tailings samples ranged from 41.7 nGyh-1 to 76.3 nGyh-1 , 13.3 nGyh-1 to 32.7 nGyh-1 and 2.3 nGyh-1 to 58.0 nGyh-1 respectively. Only Okame had a higher value for soil than the world wide average value of 60 nGyh-1 • The Annual Effective Dose rates in soil, mine tailings and rock samples ranged from 0.051 mSvy-1 to 0.093 mSvy-1 , 0.024 mSvf1 to 0.050 mSvf1 and 0.011 mSvy-1 to 0.047 mSvf1 respectively which were lower than the ICRP recommended value of 20 mSvf1 • The internal hazard indices in soil, mine tailings and rock samples ranged from 0.30 to 0.56, 0.15 to 0.27 and 0.02 to 0.43 respectively. External hazard indices of the radionuclides in the soil, mine tailings and rock samples ranged from 0.27 to 0.47, 0.10 to 0.23 and 0.01 to 0.36 respectively. They were found to be below unity as per ICRP, 2007 maximum permissible limit. The Excess Lifetime Cancer Risk (ELCR) ranged from 6.90x10-5 to 1.93x104 was lower than the ICRP maximum permissible excess lifetime cancer risk limit of 5.60x10-2 . Despite the low radiological health risk, miners need protective gears particularly at Okame and Greenstone mines and further research need to be done to validate these findings.
Determination of radiological hazard levels of gammma rays from radionuclides in water from selected boreholes in Moroto district, Uganda
(Kyambogo University, 2021-03) Okello, Sam
This study was designed to identify gamma ray emitting radionuclides using the GDM 20 NaI(Tl) detector and to determine and compare the activity concentrations, absorbed dose rates, annual effective dose equivalent and the internal and external radiological hazard levels of gamma rays from radionuclides in water from boreholes in four sub counties of Rupa, Katikekile, Nadunget and Northern Division of Moroto District. The radionuclides of 226Ra and 232Th were found in water samples from all the boreholes of the four sub counties. The radionuclide of 40K was only found in two boreholes, three boreholes and five boreholes of Rupa, Katikekile and Nadunget respectively. None was found in the boreholes from Northern Division. The activity concentration of 226Ra exceeded the world average value of 35 Bql-1 in three boreholes of Rupa and Northern Division; in four boreholes of Katikekile and in all the seven boreholes of Nadunget. The activity concentration of 232Th was found to be less than the world average of 30 Bql-1 in all the water samples from all the regions. The activity concentration of 40K was found to exceed the world average of 400 Bql-1 in all the water samples from all the regions. The absorbed dose rates was found to be greater than the world average of 84 nGyh-1 for water samples from two boreholes of Rupa and Northern Division; in five boreholes of Katikekile and in six boreholes of Nadunget. The annual effective dose equivalent was found to be lower than the world internal exposure limit of 0.41 mSvy-1 in all the water samples analyzed. The internal radiological hazard level was found to exceed the permissible value of 1.00 (unity) only in one borehole and three boreholes in Katikekile and Nadunget respectively. The external radiological hazard level was found to exceeded the permissible limit in one borehole from Nadunget; and equal to 1.00 the permissible limit in one borehole from Katikekile. However activity concentration of 226Ra and 40K exceeded the world average value in seventeen boreholes and ten boreholes respectively. While 232Th activity concentrations in all boreholes were below the world average value. It is recommended that a similar study should be carried out to check the results of this study and to find the excess life time cancer risk on the populace that use the water especially those that show high activity and hazard levels. The scope of the study for later studies should be extended to more boreholes.
Determination of the characteristics of solid fuel developed from a mixture of thermoplastic wastes and clay materials
(Kyambogo University(Unpublished work), 2021-03) Oballim, Terence
This study was driven by the fact that plenty of plastics which have potentials to be used as source of fuel are left as wastes in the environment without proper utilization. The study was directed toward the use of a particular type of plastics for making a plastic based solid fuel and to find its viability for use as source of energy. Polyethylene – terephthalate (PET) material obtained from waste mineral water bottles and ball clay were mixed to form PET – Clay Solid Fuel (PETCSF) product. Clay was mixed with plastics to avoid melt flowing or dropping of the fuel in the stove during combustion. The parameters of the developed PETCSF those were determined to find its viability as source of energy were Mass of melt drops, mass combustion rate, mass of ash and the calorific value. The following Clay Plastic Ratio (CPR) 1:2.43, 1:2.33 and 1:1.20 were found to be sufficient in stopping melt dropping behavior of the developed solid fuel in the stove during combustion. The calorific values of the PETCSF were found to be 14,335 J g-1, 14,170 J g-1 and 11,182 J g-1 for CPR = 1:2.43, 1:2.33 & 1:1.20 respectively. Calorific values of an equal mass of charcoal, paper and Benzoic acid tablet (used as reference solid fuel materials) were 7,316 J g-1, 12,475 J g-1 and 24,239 J g-1 respectively. The mass combustion rates for CPR = 1:2.43, 1:2.33 & 1:1.20 were found to be 2.45 g minute-1, 2.43 g minute-1 and 1.98 g minute-1 respectively. The mass of ash left after combustion for the above respective CPR values were 36.64 g, 37.37 g and 50.73 g respectively. When compared, the calorific value of the developed PETCSF was found to be about two times higher than for charcoal of an equal mass. Benzoic acid tablet had the highest calorific value. Thus, PETCSF is a viable source of fuel compared to charcoal in terms of the calorific value and moreover its combustion rate can be controlled by using a specific CPR of 1:2.43 as shown by the result of the study. The population should be encouraged by the findings in this study and to begin thinking of using plastic based solid fuel as an alternative to charcoal and firewood which currently are the only predominant sources of fuel for majority of the population. The used plastic based solid fuel in an oxygen rich environment (or sufficient air circulation) is strongly recommended as complete combustion is guaranteed. Insufficient air supply may lead to incomplete combustion of the fuel and possibly release of particles (soot/smoke) which if inhaled may be harmful to the user.
Performance evaluation of amorphous silicon photovoltaic module using solar light of different wavelengths
(Kyambogo University[unpublished work], 2022-07) Seba Ackim, Sichone
The performance of amorphous silicon photovoltaic module was evaluated using solar light of different wavelengths in this study. The different wavelengths of solar light were filtered by use of colour filters. During data collection, the plane of the module was oriented perpendicular to the sun, in order to ensure that module gets the maximum irradiation. The I-V tracer was employed to obtain the module I-V curves, P-V curves and subsequently the I-V outputs of the module. The short circuit current and power output of the module varied at different wavelengths of solar light, but the module’s open circuit voltage was almost constant at different wavelengths. The highest short circuit current of 0.76 A, maximal power of 9.60 W and efficiency of 3.60 % were obtained when the module was not covered with any colour filter. Among all the used colour filters, the yellow colour of solar light gave the highest short circuit current of 0.68 A, maximal power of 8.89 W and efficiency of 3.29 %. This suggests that the yellow light is highly efficient in the amorphous silicon photovoltaic module power generation compared to the other colours of the visible light. The impact of module temperature on the module’s open circuit voltage and short circuit current for different wavelengths of solar light were also investigated. The results showed that the rise in module temperature led to the fall in the open circuit voltage and small increment in short circuit current of the module regardless the wavelength of solar light. Due to the outcomes of this research, it was recommended that more research is needed to be done by filtering solar light into single wavelengths rather than the band of wavelengths. The colors of visible light which were not considered in this study, have to be considered for future work. Manufacturers may use the findings of this study to modify the technological design of the module so as efficiently capture the wavelengths of solar light within the yellow portion of the visible spectrum.
Comparison of roki and sunflower oils as sensible heat storage materials for cooking applications
(Kyambogo University [unpublished work], 2022-07) Frank, Mndeme Sayuni
Sensible heat storage materials are cheaper than latent heat storage materials for small storage volumes. Static experiments to evaluate the thermal performances of two Ugandan locally available edible vegetable cooking oils for medium temperature thermal energy storage are presented. The two vegetable oils evaluated and compared are Sunflower oil and Roki oil (a blend of Palm oil and Sunflower oil). Temperature profiles are used to assess the thermal performances during heating cycles, cool-down cycles, energy, exergy, and heat utilization. The results show that Roki oil attains a higher maximum temperature (~ 170 ℃) compared to the Sunflower oil (~ 160 ℃) during low-temperature heating cycles. Roki oil shows higher temperatures during cooling compared to Sunflower oil, achieving a final temperature (~ 78 ℃) slightly higher than that of Sunflower oil (~ 76 ℃). Roki oil shows a maximum energy rate of 413 W compared to Sunflower oil showing a maximum energy rate of 387 W, this is possibly due to the low thermal mass (mc) of Roki oil compared to Sunflower oil. Roki oil also shows higher maximum exergy rate of ~ 129 W compared to that of Sunflower oil ~ 120 W. This occurs because of the lower thermal mass (mc) of the Roki oil which leads to a quick rise of temperature. The exergy factor of Roki oil (0.31 – 0.62) is slightly higher than Sunflower oil (0.27 – 0.59) within 1 hour and 40 minutes. This is possibly due to the higher difference in temperature of Roki oil compared to Sunflower oil. The heat utilization characteristics of the two heat storage materials are experimentally determined in water heating experiments using 1.0 kg to 3.0 kg water loads. Roki oil shows higher average heat utilization (151 – 350) kJ, and higher average heat utilization efficiency values (0.25 – 0.66) as compared to Sunflower oil (148 – 300) kJ and (0.25 – 0.60), respectively. The average heat utilization and average heat utilization efficiency values increase with the increase in the water load for both Sunflower oil and Roki oil. The best overall performance is shown by Roki oil compared to Sunflower oil. Preliminary results with parabolic dish solar cookers are also presented in this work. The results show that Roki oil performs better than Sunflower oil during heating, cooling/heat retention, and heat utilization.

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