SCALE 6.1 code system and VENTURE-PC code system has been used for the core conversion of Miniature Neutron Source Reactor (MNSR) from Highly Enriched Uranium (HEU) system (90.2% enriched UAl 4 fuel) to Low Enriched Uranium (LEU) system (19.75% enriched UO 2 -zircaloy-4 fuel). All other structure materials and dimensions of HEU and LEU cores are the same except the increase in the fuel cell diameters for the proposed LEU core. Results obtained show that the peak power density of 4.310033 Watts/cc, maximum neutron density of 6.94535e-6 n/cc, total control rod worth of ሺ723 േ 0.049ሻ pcm, clean cold core excess reactivity of ሺ404 േ 0.009ሻ pcm, k ୣ of ሺ1.0119634 േ 0.0072434ሻ , shutdown margin of ሺ319 േ 0.1003ሻ pcm and neutron flux profile of ሺ1.24 ൈ 10 ଵଶ േ 0.11ሻ ncm ିଶ s ିଵ for the potential LEU core are slightly greater than those of the
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
In the last quarter of 2018, low enriched uranium dioxide fuel with zirconium alloy cladding was used successfully to convert the core of NIRR-1 from HEU to LEU fuel and the removed core returned to the country of origin. The objective of this study was to investigate the possibility of fueling the same system with alternate LEU fuel for future replacement of the current fuel, without any unacceptable compromise in reactor performance. Having more than one fuel options available for the same reactor system will present Nigeria an opportunity of making good economic decisions at the end of the cycle of the current LEU fuel. The performance of low enriched uranium silicide aluminum dispersion fuels in the core of NIRR-1 has been investigated and the results were identical with that of similar studies conducted elsewhere for generic MNSR system. Some of the calculated reactor parameters using this alternate LEU fuel were closely identical with that of the old HEU core. The computer software selected for this studies were the SCALE code system and the VENTURE PC. While the SCALE code system was employed to generate a properly averaged multigroup cross section library for the investigated LEU core models for NIRR-1 system, the VENTURE PC was utilized to give criticality information, few group fluxes and power density distributions within the core of the modeled system.Keywords— Reactor, Reactivity, Fuel, Enriched, Silicide
Nigeria with over 0.181 Billion people currently suffers from acute power shortage which has seriously affected the country’s economy for several years with no viable solution thus far. Salvaging this situation brings up the need for a search for more efficient means of generating ‘24/7’ electricity in Nigeria. Several attempts by Government to introduce nuclear generated electricity were faced with a lot of criticism from the Nigerian populace. This paper focuses on the perceptions of Nigerians vis-a-vis electricity production using nuclear energy. It raised valid questions and sampled opinions of Nigerians. The survey carried out in this work shows that a lot of Nigerians do not understand that we have accepted more risky physical facilities or riskier option of electrical energy generation as compared to nuclear energy. Hence it made comparison between the casualty rates from other energy generation sources, accident from various means of transportation and from nuclear power plant. The analysis of data used in this work (as provided in table 6.0), shows that it would take road traffic accidents just about four days to claim as much lives as nuclear reactors in 50 years and that in about three years, aviation industry in Nigeria claim more lives than accidents from nuclear reactors in 50 years. We also observed that electricity production from nuclear energy has the lowest record of accidents and fatalities rate as compared to other major energy generation sources.
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