ko – NAA EVALUATION OF Al /Si CONCENTRATION RATIOS IN BAUXITES USING 5Ci AM-Be NEUTRON SOURCE IRRADIATION FACILITY
ko – NAA EVALUATION OF Al /Si CONCENTRATION RATIOS IN BAUXITES USING 5Ci AM-Be NEUTRON SOURCE IRRADIATION FACILITY
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Date
2011-04
Authors
SULEIMAN, SHAIBU ASUKU
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Abstract
An irradiation method with thermal and fast neutrons from a 5Ci Am-Be neutron source facility in combination with 3”x3” NaI(Tl) detector system
has been used to determine Al/Si concentration ratios in alumino-silicate ores via K0-NAA. Two different samples were analyzed; raw bauxite
samples from exploration field and other bauxite samples from the NAA Laboratory of CERT - A.B.U Zaria. Samples were co-irradiated bare and
under cadmium-cover with gold foil as a monitor for one hour and counted for ten minutes. One minute delay was observed for the samples and
13minutes for the foils before counting. The peak area analysis of the 1779Kev and 411.8Kev gamma-ray lines of 28Al and 198Au product
radionuclides produced via 27Al(n, )28Al and 197Au(n, )198Au reactions respectively, the flux ratio, f, the flux shapping parameter, α of the
irradiation sites and the K0-values for 27Al(n, )28Al and 197Au(n, )198Au reaction were used to determine the aluminium concentration in the
samples. Due to unavailability of K0- Value for 28Si(n,p)28Al, the peak counts of 28Al product radionuclide produced via 27Al(n, )28Al and
28Si(n,p)28Al reactions, the neutron flux in the irradiation sites, the neutron cross-section for (n, ), (n,p) reactions and the aluminium concentrations
obtained via ko-NAA were used to determine silicon concentration in the samples. Our results (11.13±1.15%, 8.09±0.75%, 0.021±0.007%) compare
well with the results obtained from the Reactor Neutron Activation Analysis (RNAA) for aluminium concentration in the raw samples. The Al/Si
concentration ratios evaluated for other samples are; 0.72±0.05, 0.98±0.14, 0.97±0.12, 0.70±0.11, 0.98±0.14, 0.59±0.03, 0.67±0.08, 0.57±0.08,
0.67±0.07, 0.84±0.05, 0.38±0.07, 0.41±0.01, 0.81±0.05, 1.30±0.25, 0.55±0.27. These ratios compare well with the results of earlier analysis done on
them using a different approach (Jonah et al, 2004). Our results show that k0-NAA evaluation of Al/Si concentration ratio in alumino-silicate ores is
achievable.
Description
A thesis submitted to the postgraduate school, Ahmadu Bello University, Zaria, in
partial fulfillment of the requirement for the award of the degree of Master of Science
(M.Sc) in physics.
DEPARTMENT OF PHYSICS,
AHMADU BELLO UNIVERSITY, ZARIA,
NIGERIA.
MAY, 2011
Keywords
ko – NAA EVALUATION,, Al /Si CONCENTRATION,, BAUXITES,, 5Ci AM-Be NEUTRON,, IRRADIATION FACILITY