School of Nuclear and Allied Sciences
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Item Investigation of Wall Thickness, Corrosion, and Deposits in Industrial Pipelines Using Radiographic Technique(International Journal of Corrosion, 2023) Amoah, P.; Owusu-Poku, S.; Ajubala, G.A.In this study, radiographic techniques were used to inspect large-diameter pipes that are used for transporting fluids in some industries in Ghana. Radiographic approaches such as the double wall technique (DWT) and tangential radiographic technique (TRT) were used to evaluate the remaining wall thickness, deposits, and corrosion in the pipes. Two steel pipes with known varying wall thicknesses ranging from 4.00 mm to 13.00 mm with a diameter of 150.00 mm were examined to authenticate the accuracy and reliability of the tangential method that was used to measure the remaining wall thickness. The tangential configuration resulted in a higher material thickness, which therefore required more time of exposure compared to the DWT method. The exposure angle of the source to the tangential part of the specimen was approximately 87° . The film generated was compared with a normal pipe piece that was not machined to serve as a control. From the radiograph obtained, an average of 6 and 7 rounded indications depicting pitting corrosion were revealed on the radiograph of the internally and externally fabricated pipe, respectively. Radiographs after the TRT revealed that the recorded wall thickness obtained from the film is about twice the value of the calculated true wall thickness.Item Radon mapping, correlation study of radium, seasonal indoor radon and radon exhalation levels in communities around Ghana atomic energy commission(Heliyon, 2023) Otoo, F.; Kpordzro, R.; Amable, A.S.K.Radon mapping and seasonal radon studies have been carried out within the communities around the Ghana Atomic Energy Commission (GAEC), using ArcMap geostatistical interpolation tool. The correlation analysis was done using Pearson’s correlation tools. Average seasonal indoor radon variations for CR (rainy) and CD (dry) with mean values ranging from 28.9 to 177.2 Bq/m3 (78.1 ± 38.7 Bq/m3 ) and 24.4–125.5 Bq/m3 (69.9 ± 24.2 Bq/m3 ). Average seasonal soil radon exhalation for ER (rainy) and ED (dry) with mean values ranging from 39.6 to 100.3 (68.9 ± 24.2 μBq/m2 h) and 55.2 to 111.9 (77.1 ± 18.7 μBq/m2 h). Radium concentrations ranged from 8.1 to 42.2 Bq/kg (21.3 ± 9.9 Bq/kg). Annual effective dose and resultant effective dose to lungs were found to be 0.9 to 2.9 (1.9 ± 0.8 mSv/yr), 2.1 to 9.2 (4.6 mSv/yr). The study recorded the highest and lowest positive correlation coefficient was found in the study with higher and lower coefficient values of 0.81 and 0.47 recorded in radium concentration with radon exhalation and indoor radon concentration within the dry season respectively. Pearson correlation result recorded values 0.81 and 0.47 as the highest and lowest positive coefficient values for the radium concentration correlation between radon exhalation and indoor radon concentration. One directional principal component was observed in radium concentration, seasonal radon exhalation, and indoor radon concentration. Two clusters originated from radium and seasonal radon concentrations present in dwellings as well as soils. Pearson’s correlation results were in agreed with the principal component and cluster factor analysis. The study obtained the highest and lowest indoor radon concentrations with radon exhalation in rainy and dry seasons. Radium concentration was found to have a considerable effect on indoor radon and radon exhalation in dwellings and soils.Item Rare-earth element comparative analysis in chosen geological samples using nuclear-related analytical techniques(Nuclear Inst. and Methods in Physics Research, B, 2023) Adeti, P.J.; Amoako, G.; Kansaana, C.; et al.In this study, four analytical techniques for the detection of Sc, La, Ce, Nd, Sm, Eu, Tb and Lu in volcanic rock specimens from Ghana have been compared. These rock samples were examined using inductively coupled plasma mass spectrometry, X-ray fluorescence spectrometry, and instrumental neutron activation analysis. The Am-241 excitation-based X-ray fluorescence accuracies were good for Y, La, Ce, Nd, Eu, and the results were comparable to inductively coupled plasma mass spectrometry and instrumental neutron activation analysis except Silver-anode X-ray tube X-ray fluorescence. This demonstrates the limitations of the tube-based X-ray fluorescence excitation system for rare earth elements analysis, primarily caused by interference between the K series X-ray emission from the transition metals and the relatively low intensities of L-series lines of the rare earth elements. Data on the precision and accuracy of these methods were based on IAEA SOIL-7 reference material.Item Numerical simulation for the control rod assembly drop time evaluation in a LFR(Heliyon, 2022) Arthur, E.M.; Zhang, C.; Debrah, S.K.; Yamoah, S.; Wang, L.During scram, the Control Rod Assembly (CRA) is quickly dropped into the core and as well, if any of the operating limits are exceeded, the CRA is dropped into the core within a stipulated time to shut down the reactor power as soon as possible. In this study, the Computational Fluid Dynamics (CFD) approach was used to investigate the CRA drop dynamics of a lead-based research reactor. To simulate the flow field around the CRA in the guide tube, a 3-dimensional model of the CRA in the LBE-filled guide tube was developed and discretized; and the averaged Navier-Stokes equations coupled with the dynamic mesh method were adopted. Considering the large mesh deformation in the LBE coolant domain while the CRA drops, the recently developed FSI method in the CFX code, namely the rigid body approach, was adopted, which falls under the monolithic method. In this method, the translational CRA wall, which is partially immersed in the LBE, was set as a rigid body. It has the advantage of updating and improving the mesh quality through the mesh and re-meshing technique during the process of computation. Compared with the results of the work done in the available literature, the CFD model proved to be applicable and reliable. From the results, the inherent high density among the LBE flow characteristics had the most influence on the drop time. The mass of the CRA impacts its driving force so that the drop time reduces when the CRA mass is increased. In conclusion, the method used in this study can be applied to compute and predict significant parameters which can serve as a reference for a suitable design of the CRA and its drive mechanism in the case of modification for safetyItem Zinc Oxide Nanoparticles Synthesis Methods and its Effect on Morphology: A Review(Biointerface Research in Applied Chemistry, 2021) Droepenu, E.K.; Wee, B.S.; Chin, S.F.; Kok, K.Y.; Maligan, M.F.Zinc oxide is an important material with numerous applications due to its unique properties. Due to their thermal and chemical stability are used in wide applications such as LEDs, sensors, catalysts, and photodetectors. Different chemical, physical, and biological methods have been adopted to achieve the intended result, as enumerated in many pieces of literature. Therefore, selecting an efficient synthesis process is essential, which is a key factor that significantly influences the efficacy of the synthesized nanocrystalline materials. The chemical synthesis of nanoparticles (NPs) via hydrothermal, solvothermal, and sol-gel routes is considered effective as high-quality crystalline structures are produced. Control of parameters of processes yields excellent morphological features of the synthesized samples. This review explored the different parameters of processes and their effect on the morphology of ZnO nanostructures via hydrothermal, solvothermal, and sol-gel techniques. Finally, some ZnO nanocomposites molecules are reviewed as per the dopant used and its effect on the sample compound synthesized.Item nNumerical investigation of bubble interaction mechanisms in gas-liquid bubbly flows: Harmonisation of bubble breakup and coalescence effects(International Journal of Multiphase Flow, 2021) Yamoah, S.; Owusu-Manu, C.K.; Akaho, E.H.K.Numerical investigation of the dynamics of gas-liquid bubbly flow has been performed by using the population balance approach. Using the homogeneous MUSIG model coupled with the two-fluid model, the evolution of bubble size distribution in vertical pipes has been simulated with appropriate consideration of bubble interaction mechanisms. In particular, the study focuses on harmonising the imbalance often associated with breakup and coalescence rates by performing extensive numerical investigations for the examination and comparison of different model formulations to harmonise the coalescence calibration factor of Prince and Blanch (1990) model. To avoid the fine-tuning procedure of selecting calibration factors to harmonise the breakup and coalescence effects, a breakup calibration factor of 1.0 (default setting in ANSYS CFX) was used and three different expressions area-averaged and included as the coalescence calibration factor for the model of Prince and Blanch (1990) modelled using CFX Expression Language (CEL). The performance of the three different “cases” (modifications) has been investigated, compared with each other and validated against the experimental data reported by Monr´os et al. (2013). In general, the comparison has shown that all the “cases” yielded satisfactory results when the numerical results were compared with five primitive experimental parameters, namely: gas volume fraction, interfacial area concentration, Sauter mean bubble diameter, gas velocity and liquid velocity. The encouraging results obtained clearly show the capability of the “cases” modelled in capturing the evolution of the bubble sizes. The agreement with the gas volume fraction profiles indicates a level of confidence in the interfacial force models used. Similarly, the agreement seen with the interfacial area concentration indicates that the “cases” modelled for the birth and death processes are reasonably adequate to describe the bubble dynamics. Overall, the comparison shows that the model labelled as “case 2” presented the best results in most of the experimental conditions simulated.Item Measurement of thermal neutron and resonance integral cross sections of the reaction 51V(n,γ)52V using a 20 Ci Am-Be isotopic neutron source(Annals of Nuclear Energy, 2011-07) Agbemava, S.E.; Nyarko, B.J.B.; Fletcher, J.J.; Sogbadji, R.B.M.; Mensimah, E.; Asamoah, M.The thermal neutron capture cross section (σo) and the resonance integral (Io) of the 51V(n,γ) 52V reaction were measured with an activation method to provide fundamental data for reactor calculation, activation analysis, and other theoretical and experimental uses concerning the interaction of neutron with matter. The vanadium and manganese samples were irradiated within and without a Cd shield case using a 20 Ci Am-Be neutron source. The activities of the samples were measured using gamma-ray spectroscopy. The thermal neutron capture cross section and the resonance integral were determined relative to the reference reaction 55Mn(n,γ)56Mn and the values obtained are 5.16 ± 0.19 barns and 2.53 ± 0.1 barns respectively. The previous measurements of the σo and Io of the reaction 51V(n,γ)52V were reviewed and the difference between the present values and the previous results were discussed. © 2011 Elsevier Ltd. All rights reserved.Item Neutron flux distribution in the irradiation channels of Am-Be neutron source irradiation facility(Annals of Nuclear Energy, 2011-06) Asamoah, M.; Nyarko, B.J.B.; Fletcher, J.J.; Sogbadji, R.B.M.; Yamoah, S.; Agbemava, S.E.; Mensimah, E.Monte Carlo (MCNP-5) simulations of the neutron fluxes were performed to determine the radial and axial neutron fluxes of the two irradiation sites of the 20 Ci 241Am-Be neutron irradiation facility at NNRI. The geometry of the 241Am-Be source as well as the irradiator design, constituted one cylindrical neutron source at the center of a cylindrical barrel with water as moderator. In the far and the near irradiation sites that were 13.1 cm and 4.2 cm, respectively, from the source, the average thermal, epithermal and fast neutron fluxes axially increase exponentially from the bottom and peak at the center of the source 3.0 cm from the bottom of the source and decrease to a very low value at the end of the tube. The percentage of the average thermal flux increases as the distance from the source increases, while the percentages of the epithermal and fast fluxes decrease as the distance from source increases. In the far and near irradiation sites the average radial thermal neutron flux decreases at the rates of 307.02 n cm-2 s-1 and 961.54 n cm-2 s-1 per cm along the diameter, respectively. The average radial, epithermal and fast neutron fluxes were fairly uniform along the diameter in the two irradiation sites. © 2011 Elsevier Ltd. All rights reserved.Item Efficiency curves of the Ghana Research reactor-1(GHARR-1) spectrometry system at near and far geometries(Research Journal of Applied Sciences, Engineering and Technology, 2011-04) Agbemava, S.E.; Alhassan, E.; Della, R.; Baidoo, I.K.; Adoo, N.A.; Agbodemegbe, V.Y.; Bansah, C.Y.; Appiah, G.I.The efficiency curves of the HPGe detector at different geometries were measured in a wide energy range of 53.16 to 1408keV. In this study emphasis was laid on the effects of the source energy and the source-to-detector distance. Due to the variation of the activity levels of various samples in gamma-ray spectroscopy, the source-to-detector distance is not fixed at a constant value. This means that the measurements of the absolute detector efficiency must be carried out for each geometrical arrangement used in gamma-ray measurements. The full energy peak efficiency in terms of the gamma-ray energy and the vertical distance from the detector surface has been obtained for an N-type high purity germanium (HPGe) detector using point-like calibrated sources at four different distances from the detector. Comparison of the calculated and the experimentally measured efficiency values for the energy range of 26.345-1408 keV and a source to detector distances of 36, 49, 62, and 75 mm showed that the calculated values agree with that of the experiment within the limits of uncertainty. The standard deviations of the calculated efficiency values from the experimental at the respective source-to-detector height were as follows: 0.05% for 36 mm, 0.08% for 49 mm, 0.03% for 62 mm and 0.01% for 75 mm. © Maxwell Scientific Organization, 2011.Item Predicting the mean liquid film thickness and profile along the annular length of a uniformly heated channel at dryout(Research Journal of Applied Sciences, Engineering and Technology, 2011-09) Agbodemegbe, V.Y.; Bansah, C.Y.; Adoo, N.A.; Alhassan, E.; Akaho, E.H.K.The objective of this study was to predict the mean liquid film thickness and profile at high shear stress using a mechanistic approach. Knowledge of the liquid film thickness and its variation with two-phase flow parameters is critical for the estimation of safety parameters in the annular flow regime. The mean liquid film thickness and profile were predicted by the PLIFT code designed in Fortran 95 programming language using the PLATO FTN95 compiler. The film thickness was predicted within the annular flow regime for a flow boiling quality ranging from 40 to 80 % at high interfacial shear stress. Results obtained for a laminar liquid film flow were dumped into an excel file when the ratio of the actual predicted film thickness to the critical liquid film thickness lied within the range of 0.9 to unity. The film thickness was observed to decrease towards the exit of the annular regime at high flow boiling qualities and void fractions. The observation confirmed the effect of evaporation in decreasing the film thickness as quality is increased towards the exit of the annular regime. © Maxwell Scientific Organization, 2011.