The theory and analytical procedures in Instrumental Neutron Activation Analysis (INAA) are discussed. Application of the method to the determination of sixteen trace elements: Na, K, Mn, Sm, La, Fe, Th, Sc, Co, Ba, Rb, Br, Sb, Cs and Ta in some rock samples from Ugep in the Lower Benue Region of Nigeria, is described. The high radioactivity observed in some of the samples analyzed has been associated with the higher-than-normal concentrations of Th and K in the samples. Also, Ba and Fe concentrations in some of the samples were found to be anomalous when compared with average expected values in normal sedimentary rocks.
Ash contents of some coal samples from Enugu mines in Nigeria were measured using gamma-ray irradiation technique. The method employed gamma-ray energies of 0.060, 0.662 and 1.33 MeV of241Am,137Cs and60Co, respectively, and a counting system with a scintillation detector, to obtain empirical relationships between the conventionally determined ash content and the measured gamma-attenuation coefficient in the sample. The sensitivity of the method was observed to decrease drastically with increase in ash content above 35% ash, and with increase in energy of the gamma-ray. Further analyses showed that the error in the ash content determination was due to iron content which was not constant, but increased with ash content, with vidth variation above a mean value of ±0.64% Fe2O3.
Radioelement contents of rock samples collected from some locations in the Sokoto Basin of Nigeria, where radiometric anomalies had earlier been delineated by gamma-ray spectrometric surveys, were determined by X-ray fluorescence technique using238Pu and109Cd excitation sources. The uranium contents determined were compared with delayed neutron counting results, while flame emission spectrometry was used to cross-check potassium contents. The analyses revealed uranium and thorium enrichments, with U/Th ratio of about 1.8, and negligible potassium concentrations in most samples.