Nigeria Research Reactor-1 Research Articles

Investigation of the Specific Activity of Al-0.1%Au Wire for Epithermal Neutron Activation Analysis for Nirr-1 After Conversion from Heu to Leu

The significance that Epithermal Neutron Activation Analysis (ENAA) play in the field of science research, technology and innovations and how humans interact with elemental components in food chain and environment, has led to the development of ENAA protocol in research reactors. Epithermal neutrons, which have energy between 0.5 eV and 0.5 MeV, are increasingly needed by reactor clients. In this study, we have examined the activity of the flux monitor in the irradiation site of the inner channel (A1) of Nigeria Research Reactor-1 (NIRR-1) after its conversion to low enriched uranium fuel. The flux monitor (Al-0.1%Au thin wires) was washed with acetone, dried for 2 minutes, weighed to be 0.0122 g, and was thereafter placed in a 15.0 mm internal diameter polyethylene vials that has 1 mm wall thickness for irradiation. The activity of flux monitor Al-0.1%Au wire of 0.0122 g was calculated to be 5 x 108 count/s.g using A1 inner channels of the Cd line. This value obtained in this our studies found to be consistent with previous result and has shown that the epithermal channel A1 of the NIRR-1 remain suitable for ENAA after the reactor’s fuel conversion from HEU to LEU.

Quantification of Pollution Index of Selected Heavy Metals in Agricultural Soils in Kafin Hausa Area, Northwest Nigeria

In this study, the level of heavy metals contamination in agricultural soils in Kafin Hausa, Nigeria, was investigated and characterised using the Instrumental Neutron Activation Analysis technique via the Nigeria Research Reactor-1. Fifteen soil samples were collected from five different sampling sites and analysed for eight heavy metals: aluminium (Al), arsenic (As), barium (Ba), iron (Fe), holmium (Ho), potassium (K), magnesium (Mg), and rubidium (Rb). Heavy metal pollution indices were estimated using the geo-accumulation index (Igeo), enrichment factor (EF), contamination factor (CF), and pollution load index (PLI). The results showed that the mean Igeo indexes of Al (-3.09), As (-4.88), Ba (-0.89), Fe (-3.53), K (-2.20), and Mg (-4.95) were lower than zero, indicating that the soil of the studied region was uncontaminated by these metals. The mean EF of Ho was significantly higher than other metals, indicating that the soil is enriched with this metal. As (0.40) and Mg (0.36) had the lowest EF values. Similarly, the mean CF of all metals was lower than 1, suggesting minimal or low contamination. In contrast, Ho (1.60) exhibits the highest CF value, signifying moderate contamination. The PLI values for all metals were between 0.16 and 0.51, indicating that the studied area is unpolluted. There are strong correlations between all the elements, with p-values at 0.01 level, particularly for K – Rb, Ba – K, and Ba – Rb, with values ranging from 0.94 to 0.94. Hence, the results of this study suggest that the agricultural soils in Kafin Hausa are uncontaminated by heavy metals.

Comparative analysis of core life-time for the NIRR-1 HEU and LEU cores

In this study, the end of lifetime for the Nigeria Research Reactor-1 high enriched uranium and the low enriched uranium fuelled core were analysed. The SCALE 6.2.3 computational sequences, CSAS6 and TRITON coupled with KENO-VI code were employed for Eigen value and depletion calculations respectively. The study was carried out to demonstrate the advantage of conversion of miniature neutron source reactor from high enriched uranium to the low enriched uranium fuel. The results obtained showed that the clean cold core excess reactivity values of the high enriched uranium and the low enriched uranium fuelled cores were comparable with the experimental data and indicate the suitability of the computational approach used in this study. Similarly, the integral worth of top beryllium shims was greater in the high enriched uranium core in comparison with the low enriched uranium fuelled core and could be attributed to the increased neutron leakage caused by hardening of the neutron spectrum due to higher inventory of U-238 in the low enriched uranium core. Furthermore, the lifetime of the low enriched uranium fuelled core was found to be higher when compared to the high enriched uranium core and could also be attributed to the higher loading of U-235 and U-238 in the low enriched uranium core. The longevity of the low enriched uranium fuelled core in comparison to the high enriched uranium indicate an advantage for its longer time of utilization in neutron activation analysis and underscore the importance of conversion from high enriched uranium to low enriched uranium fuel.

Effect of neutron irradiation on the impedance of Epoxy-TiO2 nanocomposite for electric power insulation

The effect of neutron irradiation on the impedance of the nano-filled polymeric based insulation materials became an important issue because of its presence in the nuclear power plant. The exposure of polymeric materials to ionizing radiation can influence the dielectric and insulating properties of the material. This work presents the influence of neutron irradiation and the presence of nanoparticle on the insulating property of Epoxy-TiO2 nanocomposite. The prepared plane nanocomposite samples were exposed to neutron radiation in the Nigeria Research Reactor I (NIRR-I) and dielectric analysis was performed over a frequency range of 20 Hz–200 kHz. The polarization relaxation process of the irradiated neat and nanocomposite is dominated by dipolar, interfacial polarization, and free radicals. The presence of TiO2 nanoparticles in epoxy composite resulted in improved impedance after irradiation when compared with the non-irradiated and irradiated neat polymer. The 1 wt% nano-filled polymer has higher impedance after irradiation and followed by the 2 wt% nano filled polymer. The impedance of the irradiated 1 wt% TiO2 nano-filled epoxy polymer increased by 8.3% and 160% when compared with the non-irradiated and irradiated neat epoxy polymer respectively. The variation of temperature of the sample revealed a consistent thermally activated process in the irradiated samples. The research suggests that filling the epoxy polymer with 1 wt% TiO2 nanoparticle can modify the dielectric and the polarization relaxation behaviour of the polymer composites. This could enhance the resistance of the polymer composite to radiation-induced degradation in the polymeric insulation.

Elemental Analysis of Medicinal Plants Used for the Treatment of Some Gastrointestinal Diseases in Ethiopia Using INAA Technique.

The aim of the study is to carry out elemental analysis of traditional herbs used as medicinal plants for the treatment of diseases in southern Ethiopia. The medicinal plants are those frequently used by the local/traditional healers for the treatment of gastrointestinal diseases in the southern part of the country. The instrumental neutron activation analysis (INAA) technique was deployed using irradiation and counting facilities of the Nigeria Research Reactor-1. Results were obtained for some essential elements at various concentrations for six herbal medicines. The major elements found in samples analyzed include Ca, Mg, Cl, and K, whereas Al, Na, and Fe were found to be in minor concentrations. The estimated daily intake of the analyzed elements was determined and found to be below the upper tolerable limits set by FAO/WHO. Therefore, the results obtained from the analysis of these herbal medicinal plants can be useful for the treatment of diseases and pharmaceutical purposes.

Estimation of Fuel Burnup Rate for Core Conversion for the Nigeria Research Reactor-1 (NIRR-1) Fueled With 19.75% Enriched UO2 USING VENTURE PC Code

A standardized burnup analysis using VENTURE-PC computer codes system has been performed for the core conversion study of Nigeria Research Reactor-1. The result obtained from this analysis showed that the mass of Uranium decreases with increase in the number of days of reactor operation while the quantity of Plutonium continues to build up linearly. The buildup of the fissile isotope in the Low Enriched Uranium (LEU) core is very much greater than in the Highly Enriched Uranium (HEU) core. The quantity of Uranium-235 consumed and the amount of Plutonium-239 produce in the core of the reactor were 13.95 g and 0.766745 g respectively for the period of 11 years of reactor operation which is in good agreement with other literatures. This results obtained showed that uranium dioxide (UO2) fuel is a potential material for future Low Enriched Uranium (LEU) core conversion of Nigeria Research Reactor.

Nigeria research reactor-1 : Vertical detector efficiency calibration using conventional and semi-empirical approach for large samples NAA implementation

Detector efficiency calibration is mandatory for accurate measurement of induced activity in irradiated samples and for safe operation of the reactor with minimal uncertainty. This paper reported the efficiency calibration of vertically dIpstick High Purity Germanium detector, installed at the Centre for Energy Research and Training, Ahmadu Bello University Zaria for the purpose of large sample Neutron Activation Analysis (NAA) using Nigeria research reactor-1 (NIRR-1). The performance of the detector was evaluated for the radioisotope activity measurements during the reactor operation for large samples neutron activation analysis. The detector performance in terms of radioisotopes detection ability was inspected using the standard conventional and semi-empirical approaches. The full energy peak efficiencies were determined at the corresponding energies for three different geometries (source to detector distance of 1, 5 and 10 cm). The semi-empirical approach produced better and precise results that logically rhymed with theory than the traditional approach. Besides that, a consistency in the nature of the graphs and values were evidenced. The determined efficiencies and their corresponding energies revealed encouraging outcome and ensured the successful NAA for large samples of different material compositions.

MCNP Simulation of Physics Parameters of Dispersion Fuels for Conversion of NIRR-1 to LEU

The Nigeria Research Reactor-1 (NIRR-1) is one of the Commercial Miniature Neutron Source Reactors (MNSRs) sited outside China and scheduled for conversion under the auspices of Reduced Enrichment for Research and Test Reactors (RERTR) program. Since 2006, the reduction in the fuel enrichment of MSNR facilities from greater than 90% HEU cores to less than 20% LEU cores has been embarked upon. Consequently in this work, the physics parameters of three dispersion LEU fuels, which include U3Si, U3Si2, and U9Mo enriched to 19.75% were determined by the MCNP code to investigate their suitability for the conversion of NIRR-1 to LEU. The following reactor core physics parameters were computed for the LEU fuel options: clean cold core excess reactivity (ρex), control rod (CR) worth, shut down margin (SDM), neutron flux distributions in the irradiation channels and kinetics data (i.e. effective delayed neutron fraction, βeff and prompt neutron lifetime, lf). Results are compared with experimental and calculated data of the current HEU core and indicate that it would be feasible to use any of the LEU options for the conversion of commercial MNSR in general and NIRR-1 in particular from HEU to LEU.

Effect of Temperature Difference and Control Rod Movement on Neutron Flux Distribution in Nigeria Research Reactor-1 Core

Effect of Temperature Difference and Control Rod Movement on Neutron Flux Distribution in Nigeria Research Reactor-1 Core

Prediction of Peak Temperatures of Nigeria Research Reactor Core Components under Several Reactivity Accident Tests

The Nigeria Research Reactor-1 (NIRR-1) consists of small water cooled square cylindrical core of 23cm in diameter and 23cm high. The small dimension of the core of this reactor facilitated our choice of PARET to perform reactivity accident analysis for NIRR-1 system. Our goal in this work is to predict the peak temperature of some important Nigeria Research Reactor (NIRR-1) core components under several reactivity accident tests. At power levels below 80kW, there were no significant differences between the peak fuel centerline temperatures, the peak fuel surface temperature and the peak clad surface temperature in the hot channel as well as in the average channel. The result from the reactivity accident test shows that power can never rise to an uncontrollable level in the core of NIRR-1 under ramp or step insertion of up to 4mk of reactivity. The calculated temperature of the important core components (e.g. fuel and clad) in the two channels (during this reactivity accident test) were far below their melting point temperatures. Boiling of any kind was not observed during this reactivity accident test. Therefore, NIRR-1 can be operated safely even if there is an inadvertent addition of up to 4mk of positive reactivity

An investigation of reactivity effect due to inadvertent filling of the irradiation channels with water in NIRR-1 Nigeria Research Reactor-1

Investigation of reactivity variation due to flooding of the irradiation channels of Nigeria Research Reactor (NIRR-1) a low power miniature neutron source reactor (MNSR) located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria Nigeria using the MCNP code for High Enrich Uranium (HEU) and Low Enrich Uranium (LEU) core has been simulated in this present study. In this work, the excess reactivity worth of flooding HEU core for 1 inner, 2 inner, 3 inner, 4 inner and all inner are 0.318mk, 0.577mk, 0.318mk, 1.204mk and 1.503mk respectively, and outer irradiation channels are 0.119mk, 0.169mk, 0.348mk, 0.438mk and 0.418mk respectively, the highest excess reactivity result from flooding both inner and outer irradiation channels is 2.04mk (±1.72×10−7), the excess reactivity for LEU core was 0.299mk, 0.568mk, 0.896mk, 1.195mk and 1.524mk in the inner irradiation channels, and the outer irradiation channels are 0.129mk, 0.189mk, 0.219mk, 0.269mk and 0.548mk where the highest excess reactivity was 1.942mk (±1.64×10−7) resulting from flooding inner and outer irradiation channels. The reactivity induced by flooding of the irradiation channels of NIRR-1 with water is within design safety limit enshrined in Safety Analysis Report of NIRR-1. The results also compare well with literature.

Estimating NIRR-1 burn-up and core life time expectancy using the codes WIMS and CITATION

The Nigeria Research Reactor-1 (NIRR-1) is a low power miniature neutron source reactor (MNSR) located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria Nigeria. The reactor went critical with initial core excess reactivity of 3.77mk. The NIRR-1 cold excess reactivity measured at the time of commissioning was determined to be 4.97mk, which is more than the licensed range of 3.5–4mk. Hence some cadmium poison worth −1.2mk was inserted into one of the inner irradiation sites which act as reactivity regulating device in order to reduce the core excess reactivity to 3.77mk, which is within recommended licensed range of 3.5mk and 4.0mk. In this present study, the burn-up calculations of the NIRR-1 fuel and the estimation of the core life time expectancy after 10years (the reactor core expected cycle) have been conducted using the codes WIMS and CITATION. The burn-up analyses carried out indicated that the excess reactivity of NIRR-1 follows a linear decreasing trend having 216 Effective Full Power Days (EFPD) operations. The reactivity worth of top beryllium shim data plates was calculated to be 19.072mk. The result of depletion analysis for NIRR-1 core shows that (7.9947±0.0008) g of U-235 was consumed for the period of 12years of operating time. The production of the build-up of Pu-239 was found to be (0.0347±0.0043)g. The core life time estimated in this research was found to be 30.33years. This is in good agreement with the literature

Spatial Distribution of Some Heavy Metals in Sediments from the River Hadejia Catchment, Nigeria

Heavy metals concentration levels was determined using Instrumental Nitrogen Activation Analysis (INAA) is possible using Nigeria Research Reactor-1 (NIRR) which is a Miniature Neutron Source Reactor (MNSR). It is specifically used for the Neutron Activation Analysis (NAA) technique. The selection of sediment sample is because, overtime, the chemical elements precipitate on the sediment bed; therefore the sediment sample will indicate the true nature of the chemical elements present in the river system. River Hadejia is a perennial river, though the dry season flow is from the upstream regulated flow from the Tiga and Bagauda dams. The sediment samples were collected using stratified random sampling technique based on change in land use activity. Samples were collected during dry and wet seasons and analyzed in the laboratory. The results obtained show the presence of chemical contaminants Chromium (Cr), Zinc (Zn), and Europium (Eu) in concentrations above the permissible limits in the Hadejia river system. For example, Chromium (Cr) has mean concentration of 432.86 mg/l as against the permissible limit for both WHO, (2011) and NSDWQ, (2007) of 0.05mg/l. Anthropogenic and natural geology of the area are the key determinants of the presence of these chemical elements in the area. It is recommended among others that there is need for routing the actual sources of these contaminants in our river catchment areas.

Assessment of toxic elements in selected Nigeria broiler feeds using neutron activation analysis (NAA)

In this study, Neutron Activation Analysis (NAA) was used to determine the concentrations of some toxic elements Mn, Cr, Zn, Fe, Co, Sr, La, Sm, Th and Se in some selected Nigeria broiler feed samples. Each sample (A, B, C, and D) represents certain brand of the feeds. The work was carried using the Nigeria Research Reactor – 1(NIRR -1) at the Center for Energy Research and Training Ahmadu Bello University, Zaria by short and long irradiation protocols, using thermal flux of 5.0×10 12 n cm -2 s -1 . Quality Control and Quality Assurance of the method was tested by analyzing Standard Reference Materials (NIST 1515 apple leaves,). However, the results shows the Fe concentration in sample B and Zn concentration in sample C and D were found to exceed the maximum acceptable limit with the exception of sample A. This makes the feeds contaminated with Fe and Zn not safe for broilers consumption since toxic elements are bio-accumulative and have the tendency to be transferred to human after consumption. Key words : Broiler feed, NAA, MNSR, NIRR-1

Core power prediction for Nigeria research reactor-1 (NIRR-1) using measurements of dose-rate and temperature

This study presents the results of the core power prediction for Nigeria Research Reactor-1 (NIRR-1), a low power Miniature Neutron Source Reactor (MNSR) using measurements of dose-rate, temperature and neutron flux. The measurements of the dose rate, neutron flux, inlet and outlet temperatures were made for three different power levels (6.2 kW, 15.5 kW and 31 kW) at three stages: The first one was immediately after the reactor start-up (0 min). The second one was at 105 min elapsed time of the reactor operation. The final one was made at every one hour for five hours of reactor operation at 15.5 kW. The values of the dose-rate obtained at 0 min (at 6.2 kW, 15.5 kW and 31 kW power levels) were 6.1 μSv/h, 15.0 μSv/h and 34.2 μSv/h respectively and the corresponding predicted power are 6.8 kW, 15.4 kW and 33.8 kW respectively. The values of the dose-rate obtained at 105 min (at 6.2 kW, 15.5 kW and 31 kW power level) were 7.8 μSv/h, 21.5 μSv/h and 37.4 μSv/h respectively and the corresponding predicted power were 6.3 kW, 17.8 kW and 31.1 kW respectively. For temperature measurement (7.8 °C, 12.7 °C and 18.7 °C) and (7.2 °C, 12.4 °C and 18.3 °C) at 0 min and 105 min, the results obtained were (6.5 kW, 14.8 kW and 28.0 kW) and (7.2 kW, 15.0 kW and 29.0 kW) respectively. For the measured thermal neutron flux (2.07 × 1011n/cm2s, 5.53 × 1011 n/cm2s and 1.13 × 1012 n/cm2s) and (2.06 × 1011 n/cm2s, 5.70 × 1011 n/cm2s and 1.16 × 1012 n/cm2s) at 0 min and 105 min, the results obtained were: (6.21 kW, 16.60 kW and 33.90 kW) and (6.18 kW, 17.10 kW and 34.80 kW) respectively. Comparing the results obtained with the rated power by the manufacturer, it was observed that the power obtained using dose-rate is on average more accurate with deviations (9.7%, 0.6% and 9.0%) at 0 min and (1.6%, 14.8% and 0.3%) at 105 min, and is therefore recommended for all users of Miniature Neutron Source Reactor as well as for routine estimation of Nigeria Research Reactor-1 (NIRR-1) power. In the final stage, the steady state operation of Nigerian Research Reactor-1was investigated at half power.

Analysis of Nigeria Research Reactor-1 Thermal Power Calibration Methods

This paper analyzes the accuracy of the methods used in calibrating the thermal power of Nigeria Research Reactor-1 (NIRR-1), a low-power miniature neutron source reactor located at the Centre for Energy Research and Training, Ahmadu Bello University, Zaria, Nigeria. The calibration was performed at three different power levels: low power (3.6 kW), half power (15 kW), and full power (30 kW). Two methods were used in the calibration, namely, slope and heat balance methods. The thermal power obtained by the heat balance method at low power, half power, and full power was 3.7 ± 0.2 kW, 15.2 ± 1.2 kW, and 30.7 ± 2.5 kW, respectively. The thermal power obtained by the slope method at half power and full power was 15.8 ± 0.7 kW and 30.2 ± 1.5 kW, respectively. It was observed that the slope method is more accurate with deviations of 4% and 5% for calibrations at half and full power, respectively, although the linear fit (slope method) on average temperature-rising rates during the thermal power calibration procedure at low power (3.6 kW) is not fitting. As such, the slope method of power calibration is not suitable at lower power for NIRR-1.

Computational Study of 19.75% UO2 Fuel for the Core Conversion of Nigeria Research Reactor-1 (NIRR-1) from HEU to LEU

Computational Study of 19.75% UO2 Fuel for the Core Conversion of Nigeria Research Reactor-1 (NIRR-1) from HEU to LEU

Implication of Removal of Cadmium Poison on Neutron Flux and Related Parameters in Nigeria Research Reactor - 1

Nigeria’s Miniature Neutron Source Reactor (MNSR) has been in function since 2004. Over the ten years of operation, several installation and calculation were made on Nigeria research reactor-1 for the safety under project supply agreements and IAEA member state. In this work, we show the implication of removal of cadmium poison on neutron flux and related parameter by using lattice code WIMS and core analysis code CITATION, to automatically carry out each of the following calculations on MNSRs: core excess reactivity, verification of some safety criteria, and calculating various temperature coefficients of reactivity. Results obtained before, after and after removal of cadmium poison are: excess core reactivity (3.72, 2.96 and 2.92) mk, fuel temperature coefficient reactivity (-0.0018, -0.0054 and -0.0060) mk/°C, power coefficient of reactivity (-0.2527, -0.1260 and 0.0575) mk/kW and predicted power of (15.23, 14.65 and 14.99) kW with coolant temperature (12.43, 12.10 and 12.50) °C respectively. The result will not only boost the sample handling capabilities of NIRR-1 but will also provide useful data to the MNSR community for upgrading their reactors and specifically ageing management.

Assessment of Elemental Composition in Selected Nigeria Broiler Feeds Using Neutron Activation Analysis (NAA)

Assessment of Elemental Composition in Selected Nigeria Broiler Feeds Using Neutron Activation Analysis (NAA) Four feeds common to the Nigerian broilers were analyzed for elemental composition. Neutron Activation Analysis (NAA) was used to determine the concentrations of elemental composition of selected Nigeria broiler feed samples. Each sample (A, B, C, and D) represents certain brand of the feeds. The work was carried using the Nigeria Research Reactor–1(NIRR-1) at the Center for Energy Research and Training Ahmadu Bello University, Zaria by short and long irradiation protocols, using thermal flux of 5.0×1011 ncm-2s-1. Quality Control and Quality Assurance of the method was tested by analyzing Standard Reference Materials (NIST 1515 apple leaves,). The result shows that all the macronutrient elements in the samples are significantly presence and the micronutrient are virtually below detection limit (BDL). However, the results shows that the Fe concentration in sample B and Zn concentration in sample C and D were found to exceed the maximum acceptable limit with the exception of sample A. This makes the feeds contaminated with Fe and Zn not safe for broilers consumption since toxic elements are bio-accumulative and have the tendency to be transferred to human after consumption. The obtained result can be used as primary tools to further ensure broiler feed quality control and also can work as a dataset for the close monitoring of feed contamination by governments and environmentalist.

Effect of Coolant Temperature on Core Power Behavior of a Miniature Neutron Source Reactor

Published date: Investigation shows that reactor core performance largely depends on the power. It was in recognition of the role of this importance parameter that measurements were performed to verify the effect of temperature on core power of the Nigeria Research Reactor–1 (NIRR-1), which is Miniature Neutron Source Reactor (MNSR). Our results show that the core power for a preset neutron flux of 5.0×1011 cm-2s-1 shows a fluctuating behaviors and the values ranges from 14.85 kW to 15.09 kW with average excess reactivity of 3.07 mK and 2.99 mK respectively. The power coefficient off reactivity was also found to be (0.113 mK/kW and 0.114 mK/kW) with an average coolant temperature difference of 12.2 °C. The results also indicate the need to obtain a correction factor for samples that will stay in the reactor for cyclic or longer period of irradiation provided there will be shutdown and start-up in-between the irradiations and also addition of beryllium shim to the reactor is necessary in order to compensate for the loss of core excess reactivity. Our results also revealed that there is a strong dependence of the reactor power on coolant temperature difference, which is in perfect agreement with the design of the MNSR and findings of many workers in the area. The computer program developed in this work for the determination of core power using moderator parameters will not only serve as a new source code for microcomputer control of the reactor peak power and flux distribution but will also make it possible for the microcomputer console to display real time core power level, thermal limitation of the reactor core, a tool that is lacking in MNSR design.