Osei, B.2018-07-092018-07-092017-07http://ugspace.ug.edu.gh/handle/123456789/23631Thesis (MPhil.)The GHARR-1 is in the final stages of converting its HEU (90.2 %) fuel to LEU (13 %) fuel. Due to the differences if the LEU core design as compared to that of the HEU; fuel density, dummy arrnagement, number of fuel elements, this study was carried out characterize the neutron spectrum at the irradiation sites of GHARR-1 to ascertain the impact of the conversion on the neutron spectrum. This was done theoretically using the MCNP5 code. The neutron spectrum parameters (a and f ), neutron fluxes and their axial variation were determined. Average results of a for the LEU (inner sites, -0.096; outer sites, -0.031) as compared to the HEU (inner sites, -0.103; outer sites, -0.034) indicate a further deviation from the ideal 1/E epithermal spectrum distribution for the HEU as compared to the LEU. Results of f for the HEU (inner sites, 18.76; outer sites, 48.75) and LEU (inner sites, 17.77; outer sites, 45.08) indicate some levels of neutron flux trade off in the LEU as compared to the HEU. This is attributed to the increased inventory of 238U in the LEU as compared to the HEU. The neutron flux distribution showed high levels of uniformity at the irradiation sites (2 % to 10 % variation), with the thermal neutron flux showing the highest level of uniformity. The flux distribution for GHARR-1 with HEU and LEU both followed similar patterns.enUraniumCore IrradiationGhanaThesis