The depletion analysis of the Nigerian research reactor fuel with 19.75% enriched UO2 have been performed using the VENTURE PC code. The matrix exponential method was selected in this work to perform the depletion analysis. The volume fraction of the materials in this mixture was calculated and multiplied by their respective atom densities to obtain the effective atom density of the nuclide in the water, Aluminium mix region of the fuel cell model. The plot of the variation of k infinity versus hydrogen to Uranium ratio was generated using Matlab programming language for processing of the computer code result. This shows that as the ratio of hydrogen to uranium in the core of the reactor is increased, the reactivity also increases by gradually increasing the fuel cell radii till it gets to the peak of 0.6193. Any further increment in the radius of the fuel cell radii, the reactivity of the reactor decreases as the hydrogen to uranium ratio increases.

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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 current study was undertaken to investigate the radiological and dosimetric parameters of natural product-based composite (SPI/NaOH/IA-PAE/Rhizophora spp.) phantoms. The radiological properties of the phantoms were measured at different gamma energies from Compton scatter of photons through angles of 0, 30, 45, 60, 75, and 90 degrees. Ionization chamber (IC) and Gafchromic EBT3 film dosimeters were employed to evaluate the dosimetric characteristics for photons (6–10 MV) and electrons (6–15 MeV). Radiological property results of the composite phantoms were consistent with good quality compared to those of solid water phantoms and theoretical values of water. Photon beam quality index of the SPI15 phantom with p-values of 0.071 and 0.073 exhibited insignificant changes. In addition, good agreement was found between PDD curves measured with IC and Gafchromic EBT3 film for both photons and electrons. The computed therapeutic and half-value depth ranges matched within the limits and are similar to those of water and solid water phantoms. Therefore, the radiological and dosimetric parameters of the studied composite phantom permit its use in the selection of convenient tissue- and water-equivalent phantom material for medical applications.

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 (UO 2 ) fuel is a potential material for future Low Enriched Uranium (LEU) core conversion of Nigeria Research Reactor. Rabba et al.; PSIJ, 24(2): 42-49, 2020; Article no.PSIJ.55838 43 Original Research Article