Abstract
Qualitative analysis of radionuclides requires the use of reliable gamma-ray detection system. The NaI(Tl) detector has been widely used and still one of the most used detectors today. It is therefore imperative to validate the reliability of the 5x5 cm2 NaI(Tl) gamma spectrometry system used in carrying out gamma-ray analysis of soil samples in the Radiation and Health Laboratory, Federal University of Agriculture Abeokuta, Nigeria. The gamma ray spectrometer is housed in a 5 cm thick cylindrical lead shield. Calibration was executed using standard materials produced under the auspices of the International Atomic Energy Agency (IAEA). Resolution and detection limit (LD) of the detector were determined using full width at half the maximum of the energy peak of 137Cs and background signal level of the reference materials respectively. Counting efficiencies of the detector was calculated using energies of 1460 keV, 1764keV and 2615 keV for 40K, 226Ra and 232Th respectively. Secondary samples, RGMIX1 and RGMIX2 were formulated and counted to calculate activity concentrations using the NaI(Tl) detector. Resolution of the detector was calculated to be 7.8% of 137Cs, which is good for a NaI(Tl) detector. The counting efficiency of the detector is seen to depend on the gamma ray energy. The results from this work shows that the detector system is suitable gamma spectrometry, and will give quality measurements when used for quantitative determination of radionuclides in environmental samples. The efficiency and resolution of the NaI(Tl) detector should also be determined using photon energies obtained from other radioactive sources.
Highlights
Terrestrial radiation has been around since the creation of the earth’s crust
The purpose of this study is to validate the reliability of the 5 × 5 NaI(Tl) gamma spectrometry system used in carrying out Gamma-ray spectrometry analysis of soil samples in the Radiation and Health Laboratory, Department of Physics, Federal University of Agriculture Abeokuta, South Western Nigeria
The gamma ray spectrometer used consists of a 5 × 5 NaI(Tl) detector housed in a 5 thick cylindrical lead shield in the Multipurpose Physics Laboratory in the Federal University of Agriculture Abeokuta
Summary
Terrestrial radiation has been around since the creation of the earth’s crust. It is found in rocks, soil, air, water and vegetation [1]. Human beings are always in contact with the sources of terrestrial radiation. It is important to measure the level of radiation in the environment to ascertain how much they affect our daily lives [2]. Correct, proper and reliable methods and equipment should be used.
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