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Papers by Christopher Y Bansah

The objective of this study was to predict the mean liquid film thickness and profile at high she... more 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.

Analysis of the Reactivity Temperature Coefficient (RTC) of the Ghana Research Reactor-1 using th... more Analysis of the Reactivity Temperature Coefficient (RTC) of the Ghana Research Reactor-1 using the reference HEU-UAl 4 and then the LEU-UO 2 fuel currently being developed under the RETR programme was carried out to determine the Fuel Temperature Coefficient (FTC) and Moderator Temperature Coefficient (MTC) using SCUBA, a locally developed FORTRAN 95 code. The contribution of each isotope present in the fuel cell to RTC was determined by analyzing the temperature effect on the thermal fission factor (η) and the thermal utilization factor (f). The average values of the core RTC for the temperature range of 15 o C to 140 o C at the beginning of life of the core were observed to be-0.70×10-4 and-2.061×10-4 for the HEU-UAl 4 and the LEU-UO 2 respectively.

The aim of the study is to determine the concentrations of trace elements in Ghanaian shea nut an... more The aim of the study is to determine the concentrations of trace elements in Ghanaian shea nut and shea butter. As part of the study, measurements of the elemental composition of shea butter and shea nut samples were carried out by Neutron Activation Analysis (NAA) using the Ghana Research Reactor-1 (GHARR-1). Samples collected from local markets in the Northern region of Ghana and the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1547 Peach leaves were irradiated at the GHARR-1 facility. Validation of the method was done using NIST SRM Orchard Leaves (1571) under the same experimental conditions. Six trace elements (Na, Mn, Al, Cl, Ca and K) were detected with maximum concentration of Na found to be 15±1 mg/kg in SN5, Mn; 7.4±0.8 mg/kg in SN6, Al; 259±3 mg/kg in SN1, Cl; 666±27 mg/kg in SN1, Ca; 0.21±0.04 wt.% in SN4, K; 2.0±0.04 wt.% in SN1, Ce; 3.2±0.06 mg/kg in SN2, Se; 0.12±0.004 mg/kg in SN4, and Sc; 0.40±0.02 mg/kg in SN2. The concentrations of the trace elements were within the limit laid down for safe human consumption.

Journal of Applied Science and Technology, 2011

ABSTRACT Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (... more ABSTRACT Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (CHF) of forced convective flow of water in a vertical heated channel. The code was based on the liquid sub-layer model, with the assumption that CHF occurred when the liquid film thickness between the heated surface and vapour in the slug flow regime attained critical film thickness of infinitesimally small value at positive liquid velocities for which the value of critical heat flux ratio (CHFR) ~ 1. The numerical simulations predicted trends that CHF decreased with increasing flow quality, increased with increasing coolant mass flux, and increased with channel diameter. The predicted CHF were validated with data obtained by Tong’s correlation, and the computational errors indicated deviations of 5 -10 % uncertainty levels.

Nuclear Engineering and Design, 2011

The PARET/ANL code has been adapted by the IAEA for testing transient behaviour in research react... more The PARET/ANL code has been adapted by the IAEA for testing transient behaviour in research reactors since it provides a coupled thermal hydrodynamic and point kinetics capability for estimating thermal hydraulic margins. A two-channel power peaking profile of the Ghana Research Reactor-1 (GHARR-1) has been developed for the PARET/ANL (Version 7.3; 2007) using the Monte Carlo N-Particle code (MCNP) to determine the thermal hydraulic data for reactivity insertion transients in the range of 2.0 × 10 −3 k/k to 5.5 × 10 −3 k/k. Peak clad and coolant temperatures ranged from 59.18 • C to 112.36 • C and 42.95 • C to 79.42 • C respectively. Calculated safety margins (DNBR) satisfied the MNSR thermal hydraulic design criteria for which no boiling occurs in the reactor core. The generated thermal hydraulic data demonstrated a high inherent safety feature of GHARR-1 for which the high negative reactivity feedback of the moderator limits power excursion and consequently the escalation of the clad temperature.

International Journal of Food Safety, Nutrition and Public Health, 2011

ABSTRACT Dawadawa, obtained by alkaline fermentation of the matured dawadawa pod, is a culinary p... more ABSTRACT Dawadawa, obtained by alkaline fermentation of the matured dawadawa pod, is a culinary product used to enhance taste, flavour and intensify meatiness in soups, sauces and other dishes in West and Central Africa. It is believed to cure cholera, stomachache, diarrhea, bronchitis, pneumonia, leprosy, hypertension, and pain in the bones. The trace element contents of the fermented dawadawa pods were determined by neutron activation analysis to better appreciate their medicinal and nutritional applications. Results obtained showed the presence of Na, Mn, Al, Cl, Ca, K, Cu and Mg with maximum concentration of Na found to be 37.9 ± 0.6 mg/kg in dp3, Mn; 19.5 ± 2.9 mg/kg in dp2, Al; 493 ± 3.9 mg/kg in ds1, Cl; 1074 ± 36.3 mg/kg in ds2, Cu; 6.2 ± 0.5 mg/kg in dp4, Ca; 0.90 ± 0.04 wt.% in dp2, K; 2 ± 0.02 wt.% in ds2, Mg; 0.44 ± 0.03 wt. % in ds1.

Energy Conversion and Management, 2013

A theoretical model has been developed to study the stability of the Ghana Research Reactor one (... more A theoretical model has been developed to study the stability of the Ghana Research Reactor one (GHARR-1). The closed-loop transfer function of GHARR-1 was established based on the model, which involved the neutronics and the thermal hydraulics transfer functions. The reactor kinetics was described by the point kinetics model for a single group of delayed neutrons, whilst the thermal hydraulics transfer function was based on the modified lumped parameter concept. The inherent internal feedback effect due to the fuel and the coolant was represented by the fuel temperature coefficient and the moderator temperature coefficient respectively. A computer code, RESA (REactor Stability Analysis), entirely in Java was developed based on the model for systems analysis. Stability analysis of the open-loop transfer function of GHARR-1 based on the Nyquist criterion and Bode diagrams using RESA, has shown that the closed-loop transfer function was marginally stable for variable operating power levels. The relative stability margins of GHARR-1 were also identified.

Annals of Nuclear Energy, 2013

During certain severe reactor accidents such as station-blackout accidents, countercurrent natura... more During certain severe reactor accidents such as station-blackout accidents, countercurrent natural circulation flow could develop within the reactor coolant system. Natural circulation flow is very important because of transfer of decay energy from the core to other parts of the reactor coolant system. The associated heat-ups of the reactor coolant system structures can lead to pressure boundary failures with notable vulnerabilities in the pressurizer surge line, the hot leg nozzles and the steam generator tubes. The potential for a steam generator tube failure has been of particular concern because fission products could be released to the environment through such a failure. To solve the problem of steam generator tube failure, a computer code-Steam Generator Mitigation Program (SGMP), written in FORTRAN 95 computes the recirculation ratio (RR) and the mixing fraction (MF) which are the main parameters used in characterizing natura l circulation. In the flow analysis, the RR and MF were respectively found to be 2.4 ± 0.3 and 0.8 ± 0.17. The results obtained showed that the natural circulation would delay the failure time of the steam generator tubes and is in good qualitative agreement with results from literature.

The objective of this study was to predict the mean liquid film thickness and profile at high she... more 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.

Analysis of the Reactivity Temperature Coefficient (RTC) of the Ghana Research Reactor-1 using th... more Analysis of the Reactivity Temperature Coefficient (RTC) of the Ghana Research Reactor-1 using the reference HEU-UAl 4 and then the LEU-UO 2 fuel currently being developed under the RETR programme was carried out to determine the Fuel Temperature Coefficient (FTC) and Moderator Temperature Coefficient (MTC) using SCUBA, a locally developed FORTRAN 95 code. The contribution of each isotope present in the fuel cell to RTC was determined by analyzing the temperature effect on the thermal fission factor (η) and the thermal utilization factor (f). The average values of the core RTC for the temperature range of 15 o C to 140 o C at the beginning of life of the core were observed to be-0.70×10-4 and-2.061×10-4 for the HEU-UAl 4 and the LEU-UO 2 respectively.

The aim of the study is to determine the concentrations of trace elements in Ghanaian shea nut an... more The aim of the study is to determine the concentrations of trace elements in Ghanaian shea nut and shea butter. As part of the study, measurements of the elemental composition of shea butter and shea nut samples were carried out by Neutron Activation Analysis (NAA) using the Ghana Research Reactor-1 (GHARR-1). Samples collected from local markets in the Northern region of Ghana and the National Institute of Standards and Technology (NIST) Standard Reference Material (SRM) 1547 Peach leaves were irradiated at the GHARR-1 facility. Validation of the method was done using NIST SRM Orchard Leaves (1571) under the same experimental conditions. Six trace elements (Na, Mn, Al, Cl, Ca and K) were detected with maximum concentration of Na found to be 15±1 mg/kg in SN5, Mn; 7.4±0.8 mg/kg in SN6, Al; 259±3 mg/kg in SN1, Cl; 666±27 mg/kg in SN1, Ca; 0.21±0.04 wt.% in SN4, K; 2.0±0.04 wt.% in SN1, Ce; 3.2±0.06 mg/kg in SN2, Se; 0.12±0.004 mg/kg in SN4, and Sc; 0.40±0.02 mg/kg in SN2. The concentrations of the trace elements were within the limit laid down for safe human consumption.

Journal of Applied Science and Technology, 2011

ABSTRACT Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (... more ABSTRACT Numerical computation code (PWR-DNBP) has been developed to predict Critical Heat Flux (CHF) of forced convective flow of water in a vertical heated channel. The code was based on the liquid sub-layer model, with the assumption that CHF occurred when the liquid film thickness between the heated surface and vapour in the slug flow regime attained critical film thickness of infinitesimally small value at positive liquid velocities for which the value of critical heat flux ratio (CHFR) ~ 1. The numerical simulations predicted trends that CHF decreased with increasing flow quality, increased with increasing coolant mass flux, and increased with channel diameter. The predicted CHF were validated with data obtained by Tong’s correlation, and the computational errors indicated deviations of 5 -10 % uncertainty levels.

Nuclear Engineering and Design, 2011

The PARET/ANL code has been adapted by the IAEA for testing transient behaviour in research react... more The PARET/ANL code has been adapted by the IAEA for testing transient behaviour in research reactors since it provides a coupled thermal hydrodynamic and point kinetics capability for estimating thermal hydraulic margins. A two-channel power peaking profile of the Ghana Research Reactor-1 (GHARR-1) has been developed for the PARET/ANL (Version 7.3; 2007) using the Monte Carlo N-Particle code (MCNP) to determine the thermal hydraulic data for reactivity insertion transients in the range of 2.0 × 10 −3 k/k to 5.5 × 10 −3 k/k. Peak clad and coolant temperatures ranged from 59.18 • C to 112.36 • C and 42.95 • C to 79.42 • C respectively. Calculated safety margins (DNBR) satisfied the MNSR thermal hydraulic design criteria for which no boiling occurs in the reactor core. The generated thermal hydraulic data demonstrated a high inherent safety feature of GHARR-1 for which the high negative reactivity feedback of the moderator limits power excursion and consequently the escalation of the clad temperature.

International Journal of Food Safety, Nutrition and Public Health, 2011

ABSTRACT Dawadawa, obtained by alkaline fermentation of the matured dawadawa pod, is a culinary p... more ABSTRACT Dawadawa, obtained by alkaline fermentation of the matured dawadawa pod, is a culinary product used to enhance taste, flavour and intensify meatiness in soups, sauces and other dishes in West and Central Africa. It is believed to cure cholera, stomachache, diarrhea, bronchitis, pneumonia, leprosy, hypertension, and pain in the bones. The trace element contents of the fermented dawadawa pods were determined by neutron activation analysis to better appreciate their medicinal and nutritional applications. Results obtained showed the presence of Na, Mn, Al, Cl, Ca, K, Cu and Mg with maximum concentration of Na found to be 37.9 ± 0.6 mg/kg in dp3, Mn; 19.5 ± 2.9 mg/kg in dp2, Al; 493 ± 3.9 mg/kg in ds1, Cl; 1074 ± 36.3 mg/kg in ds2, Cu; 6.2 ± 0.5 mg/kg in dp4, Ca; 0.90 ± 0.04 wt.% in dp2, K; 2 ± 0.02 wt.% in ds2, Mg; 0.44 ± 0.03 wt. % in ds1.

Energy Conversion and Management, 2013

A theoretical model has been developed to study the stability of the Ghana Research Reactor one (... more A theoretical model has been developed to study the stability of the Ghana Research Reactor one (GHARR-1). The closed-loop transfer function of GHARR-1 was established based on the model, which involved the neutronics and the thermal hydraulics transfer functions. The reactor kinetics was described by the point kinetics model for a single group of delayed neutrons, whilst the thermal hydraulics transfer function was based on the modified lumped parameter concept. The inherent internal feedback effect due to the fuel and the coolant was represented by the fuel temperature coefficient and the moderator temperature coefficient respectively. A computer code, RESA (REactor Stability Analysis), entirely in Java was developed based on the model for systems analysis. Stability analysis of the open-loop transfer function of GHARR-1 based on the Nyquist criterion and Bode diagrams using RESA, has shown that the closed-loop transfer function was marginally stable for variable operating power levels. The relative stability margins of GHARR-1 were also identified.

Annals of Nuclear Energy, 2013

During certain severe reactor accidents such as station-blackout accidents, countercurrent natura... more During certain severe reactor accidents such as station-blackout accidents, countercurrent natural circulation flow could develop within the reactor coolant system. Natural circulation flow is very important because of transfer of decay energy from the core to other parts of the reactor coolant system. The associated heat-ups of the reactor coolant system structures can lead to pressure boundary failures with notable vulnerabilities in the pressurizer surge line, the hot leg nozzles and the steam generator tubes. The potential for a steam generator tube failure has been of particular concern because fission products could be released to the environment through such a failure. To solve the problem of steam generator tube failure, a computer code-Steam Generator Mitigation Program (SGMP), written in FORTRAN 95 computes the recirculation ratio (RR) and the mixing fraction (MF) which are the main parameters used in characterizing natura l circulation. In the flow analysis, the RR and MF were respectively found to be 2.4 ± 0.3 and 0.8 ± 0.17. The results obtained showed that the natural circulation would delay the failure time of the steam generator tubes and is in good qualitative agreement with results from literature.