Browsing by Author "Chege, Margaret Wairimu"

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    Assessment of Levels of Natural Radioactivity in Sand Samples Collected from Ekalakala in Machakos County, Kenya
    (Hindawi, 2020) Munyao, Lucia Nyiva; Ketui, Daniel Kipngetich; Otieno, Calford; Chege, Margaret Wairimu
    Construction sand is naturally polluted with radionuclides of terrestrial origin. In this study, specific activities of 238U, 232+, and 40K in 30 sand samples collected along the Ekalakala River, Machakos County, Kenya, were measured using a high-purity germanium c-ray spectrometer. +e specific activities ranged between 9.7 Bqkg−1 and 24.0 Bqkg−1, 11.5 Bqkg−1 and 26.2 Bqkg−1, and 820 Bqkg−1 and 1850 Bqkg−1 for 238U, 232+, and 40K, respectively. While the mean specific activities for 238U and 232+were less than half of the world average values of 33 Bqkg−1 and 45 Bqkg−1, respectively, the average specific activity of 40K was significant since it was three times the global mean value of 420 Bqkg−1. A calculated absorbed radiation dose rate for the sand varied between 46.8 nGyh−1 and 94.2 nGyh−1 with a mean of 68.5 ± 13.3 nGyh−1. +is is not significantly different from the world average dose rate of 60 nGyh−1 for geological samples. +e AEDR and Hex had maximum values of 0.29 mSvy−1 and 0.52, respectively, both within the recommended limits of radiation exposure for members of the general public. Based on these results, the sand from Ekalakala River does not pose significant health implication to the sand harvesters as well as the inhabitants of the houses constructed using this sand.
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    An assessment of the training needs of career guidance teachers in secondary schools: a case of Maragu District
    (2012-06-25) Chege, Margaret Wairimu
    As Republic of Kenya (1999) and Wambari (1999 and 2002) have observed, profession and practioners are not well matched in relation to demands of their jobs. Consequently, Kenya faces the scaring possibility that developmental goals will not be adequately achieved. The researcher was of the opinion that training career guidance teachers would enable them to function appropriately in their roles as well as enhance the achievement of educational and developmental goals. As an initial step towards the training of career guidance teachers in Kenyan secondary schools, the study attempted an analysis of training needs of career guidance teachers in secondary schools in Maragua District. The first chapter outlines the background of the study. It goes a head to state the problem at hand. The objectives and a assumptions of the study are also examined. The second chapter explores the relevant literature in depth. It also illustrates the conceptual framework that guided the study. The third chapter will outline the research methodology that was employed by the study. Sampling method utilized by the study as also outlined. The data collected during the study is analyzed in the fourth chapter. Here the research records the fin dings of the study. Percentages, frequency tables and charts generated using Ms Excel are used to present this aspect of the study. A summary of the study is made in the fifth chapter. Here, the researcher documents the conclusions arising from the study. A number of recommendations are presented here. The study, guided by the concepts of "systematic" and "planned" training, utilised training needs analysis tools including, job and role analysis, personal interview, observation and questionnaires to collect relevant information. A total of 115 respondents were sampled using statistical techniques.
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    Evaluation of Natural Radioactivity and Radiological Hazards Associated With Earthen Building Materials Commonly Used in Bureti, Kericho County, Kenya
    (The Scientific World Journal, 2026-02) Rotich, Charles Kipngeno; Nadir, Omar Hashim; Chege, Margaret Wairimu
    This study investigates the radioactivity due to naturally occurring radionuclides in earthen building materials commonly used in Bureti, Kenya. Building materials derived from the earth’s crust often contain naturally occurring radionuclides, which may pose radiological health risks. In regions such as Bureti, Kenya, where earthen materials are widely used for construction, assessing their radioactivity is essential for public safety. Thallium-activated sodium iodide detector was used to measure the activity concentrations of 40K, 226Ra, and 232Th in the said materials and average values of 106 ± 61, 104 ± 8, and 82 ± 6Bqkg−¹, respectively, which are about three times higher than global averages were recorded. Radiological hazard parameters including radium equivalent activity, absorbed dose rate, annual effective dose rate (AEDRIN), hazard indices, excess lifetime cancer risk (ELCR), annual gonadal effective dose (AGED), and activity utilization index (AUI) were calculated to evaluate potential exposure risks. Indoor absorbed dose rates (mean 270.76 ± 18.84nGyh−¹) and AEDRIN (mean 1.00 ± 0.07mSv y−¹) exceeded international reference values, with 73.3% of samples surpassing the European Commission limit of 1mSv y−¹. While external hazard indices (mean 0.83) were largely within safe limits, internal hazard (mean 1.10) and gamma indices (mean 1.11) exceeded permissible thresholds. ELCR (mean 3.49 × 10−3 ), AGED (mean 997.27μSv y−1), and AUI (mean 2.04) values were significantly above global standards, indicating elevated long-term health risks. The findings demonstrate that Bureti earthen building materials contain enhanced radionuclide concentrations, rendering them radiologically unsafe under international guidelines. Continuous monitoring and regulatory oversight are crucial to mitigate radiation exposure and safeguard residents’ health.
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    Modelling Radon and Thoron Exhalation and Measurement of Total Natural Radiation Exposure in Mrima Hill, Kenya
    (Kenyatta University, 2015-01-22) Chege, Margaret Wairimu
    Mrima hill in Kwale County is one of the regions in Kenya with the highest levels of background radiation. Rich deposits of mineral ores such as niobium and manganese are also known to exist. Small-scale farming is the mainstay of the economy with cassava as the main cash as well as food crop; raw soil constitutes the primary building material while hand-dug wells serve as the source of water for the residents. The main objective of this research was to determine the exposure associated with radioactivity in indoor air, crops and well water in the region. This involved the determination of 222Rn and 220Rn concentration in dwellings and measurement of 226Ra, 232Th, and 40K concentrations in building materials, soil, cassava and well water. A model on radon and thoron exhalation rates was developed and validated through exhalation measurements. In addition, physico-chemical parameters of water that included heavy metals, pH and conductivity were investigated. CR-39 SSNTD were used for simultaneous measurements of 222Rn and 220Rn; accumulation chamber coupled with RAD7 monitor for exhalation measurements; HPGe detectors for radioactivity measurements in crops and water samples; and the AAS for heavy metal determination in water samples. Conductivity and pH were measured on site using standard digital meters. A total annual effective dose of 24.1 mSv/y was obtained with indoor air, crops and water, and building materials contributing 56 %, 36 % and 8 % of the dose respectively. All radon concentration values were below 200 Bq m-3 while 65 % of thoron measurements were above 300 Bq m-3. A mean thoron concentration of 652.8±397.0 Bq m-3 was obtained against that of radon of 35.2±13.9 Bq m-3. Building materials registered average radon and thoron exhalation rates of 0.0043 Bq m-2 s-1 and 19.6 Bq m-2 s-1 respectively and average concentrations of 226Ra and 232Th of 134 Bq kg-1 and 431 Bq kg-1 respectively. Modelled and measured isotopes exhalation values showed good agreement which meant that exhalation rate was dependent on the content of mother radionuclide in the building material. A correlation coefficient of near unity was observed between 226Ra and 232Th content in building materials and in soil. Over 70 % of cassava tubers and leaves had detectable amounts 226Ra with average concentrations of 60±5 Bq kg-1 and 141±11 Bq kg-1 respectively. 232Th, with an average concentration of 35.3±61.5 Bq kg-1 was detected in 28 % of the tubers; it was not detected in the leaves. 37 % and 7 % of water samples detected for 226Ra and 232Th with average concentrations of 4.3±0.3 Bq kg-1 and 2.0±0.1 Bq kg-1 respectively. 40K was present in all samples in averages of 842±539 Bq kg-1, 1708±552 Bq kg-1 and 91.4 Bq kg-1 in cassava tubers, leaves and water respectively. In terms of heavy metals, over 90% of the water samples were enriched with at least one metal with Mn and Cd as the main contaminants. The average electrical conductivity was 862±949 μSv/cm; 17 % of the samples had pH values lower than 6.5. From the results obtained, the main source of exposure in Mrima hill region is indoor air with thoron as the main source of the radiation dose. Exposure through ingestion is mainly due to 226Ra and 40K. Groundwater in the region is generally of poor quality mainly due to heavy metal enrichment.
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    Screening measurement of indoor radon-222 concentrations by gamma-ray spectromentry in Kenyatta University
    (2011-12-03) Chege, Margaret Wairimu; Rathore, I. V. S.; Chhabra, S. C.; Mustapha, A. O
    Rn-222 and its progeny are the largest contributors to the total effective dose received by the general public. It is therefore of great concern to monitor radon concentration in dwellings. Measurements of indoor 222Rn concentrations in modern and traditional buildings were carried out for comparison purposes. The measurements were carried out in the Kenyatta University campus in Nairobi, Kenya, where modern buildings and a number of model traditional buildings co-exit. Charcoal canisters were employed to sample 222Rn by exposing the activated canisters at the sampling sites for 48 hours. After exposure, gamma emissions from 222Rn daughters trapped in the canister were analysed using Nal(TI) detector, and the 222Rn concentrations at the sampling sites were calculated. The average 222Rn concentration during the sampling period was 188 Bq/m3. 222Rn concentration varied from 30.2 to 315.4 Bq/m3 in the traditional houses and from 115.76 to 257.2 Bq/m3 in modern buildings. The average 222Rn concentration was higher in the modern building than in the traditional ones. The contribution of building materials as sources of indoor 222Rn was also investigated. This involved gamma spectrometric analysis of samples of building materials to determine their 226Ra concentration, using HPGe detector. The activity concentration of 226Ra ranged from 11.66-101.93 Bq/m3 with the highest value found in the mud used in the construction of the model traditional houses. The ranges of 40K and 232Th in the samples are 254.46-1246.79 Bq/m3 and 15.3 to 148.34 Bq/m3, respectively. The bulk exhalation rates of 222Rn from selected building materials were evaluated by enclosing samples in a 222Rn free can and monitoring 222Rn accumulation with time. 222Rn a exhalation rate was highest in the mud samples and lowest in stone and concrete samples.