RE-CHARACTERIZATION OF NIGERIA RESEARCH REACTOR-1 IRRADIATION CHANNELS BEFORE CONVERSION FROM HEU TO LEU
RE-CHARACTERIZATION OF NIGERIA RESEARCH REACTOR-1 IRRADIATION CHANNELS BEFORE CONVERSION FROM HEU TO LEU
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Date
2018-10
Authors
YUSUF, Jamilu Abdullahi
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Abstract
In 2004, the first Nigerian Research Reactor (NIRR-1) was commissioned at the Centre for Energy Research and Training (CERT) Ahmadu Bello University, Zaria. NIRR-1 is a Miniature Neutron Source Reactor (MNSR) designed mainly for neutron activation analysis and personnel training. The MNSR is a compact low power reactor fueled with highly enriched uranium, cooled by natural convection and noted to possess long–term stable and reproducible neutron fluxes. Despite the stable nature of the MNSR, the neutron flux parameters in the core vary over time due to loss of reactivity from fuel burn up, accumulation of fission products and various poisons buildup in the core. Since commissioning of the reactor in 2004, a number of modifications have been effected on NIRR-1 which might have affected the neutron flux parameters in the reactor core. The spectral properties of the irradiation sites are best described by the ratio of thermal flux to epithermal flux (f), and the non-ideality of the epithermal neutron flux shape factor (α). Consequently, with these modifications and imminent conversion from Highly Enriched Uranium (HEU) to Low Enriched Uranium (LEU), this work was performed to determine the neutron flux parameters in an inner and an outer channels of the current HEU. The epithermal shape factor, α, and the thermal to epithermal flux ratio, f, were experimentally determined for two irradiation channels of NIRR-1 using Cd-ratio method with standard monitors, Al-0.1%AU, 99.5%Zn, 99.99%Zr.an high purity Zr and Zn foils of 0.125 mm thickness. The result obtained from 197AU, 94Zr and 64Zn are: α = - 0.0469 and f = 17.82 for the inner irradiation channel B2 and for the outer irradiation channel B4 α = + 0.0244 and f = 49.5.The result obtained compares very well with the data measured in 2005, at the beginning of operation of the reactor, and will be used as a baseline data to develop the protocol for NAA post conversion to LEU.
Description
A THESIS SUBMITTED TO THE SCHOOL
OF POSTGRADUATE STUDIES,
AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
IN PARTIAL FULFILMENT FOR THE REQUIREMENTS OF THE AWARD
OF
MASTERS (MSc) DEGREE IN NUCLEAR PHYSICS
DEPARTMENT OF PHYSICS
FACULTY OF PHYSICAL SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA NIGERIA
Keywords
RE-CHARACTERIZATION,, NIGERIA RESEARCH REACTOR-1,, IRRADIATION CHANNELS,, CONVERSION,, HEU,, LEU