F.O. Ogundare

TL response of a natural fluorite

Abstract A batch of a naturally occurring fluorite (CaF 2 ) from the Middle Benue Valley region of Nigeria has been studied in some detail for its thermoluminescence (TL) properties. TL glow peaks are observed at 119, 144 and 224°C at a heating rate of 10°C s −1 . The TL response is observed to increase with increasing dose, as expected, over the dose range examined. Variations are observed in the decay curves of the various glow peaks with storage at room temperature. While the lower temperature peaks are observed to decay, enhancement of the TL signal is observed for the 224°C glow peak when stored for four weeks. A low-level radioactivity measurement showed no evidence of self-irradiation from naturally occurring radionuclides. UV exposure was suppressed by storage in a black sealed container to exclude sunlight contribution to the observed TL response. A scheme involving the formation of large defect complexes, from smaller ones, during storage, as possible route leading to loss of signal in low temperature glow peaks and a corresponding enhancement at higher temperature, is suggested.

TL response of sodalime glass at high doses

Abstract The possibility of using sodalime glass as a TL material for high-dose measurements and in accident dosimetry has been investigated. The structure of the glow curves, including the number of peaks was found to be dose and annealing temperature dependent. However, a linear relationship was obtained between the glass response and dose in the dose range studied. Variation in the responses of the glass after repeated use was obtained to be 4%. Variation in batch sensitivity was also found to be not more than 5%. The fading rate of the glass response at room temperature is small.

Determination of the elemental constituents of a natural dolerite using NIRR-1

Elemental characterization of natural dolerite obtained from South Western Nigeria has been carried out using Nigeria Research Reactor-1 (NIRR-1) located at the Centre for Energy Research and Training (CERT), Ahmadu Bello University, Zaria. The measurements showed the presence of aluminum, calcium, magnesium, titanium and iron with concentrations 69,990+/-3499, 61,140+/-8.0, 38,330+/-3929, 13,880+/-1804 and 8319+/-150 ppm, respectively, as the major elements. In addition, 16 other elements, in minor and trace quantities, including Th, a radioactive rare earth element and five other rare earth elements La, Ce, Sm, Dy and Lu were identified. The presence of the rare earth elements may be a confirmation of the previous argument that the observed single but broad glow peak in the glow curve of this rock is rather an overlap of more than one glow peak. The presence of Th suggests the possibility of internal radioactivity in the rock, a necessary criterion for using a material for luminescence dating. Thus, this work indicates that dolerite can be used for luminescence dating if properly developed for the purpose.