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The aim of the present study is to determine the elemental concentration in (ppm) and specific activity in (Bqkg-1) of Uranium (238U) and Thorium (232Th) contained in the granite rock of a special geological area in Sudan (Kadugli).

The elemental concentrations and specific activity of 238U and 232Th in granite rock were determined by using the gross gamma counting technique (γ-ray spectroscopy). The analyses were performed for daughter decaying of 238U and 232Th; which are Pb-214, Bi-214 for 238U and Tl-208, Ac-228 for 232Th.

The experiments were carried out at the Nuclear Laboratory, Physics Department, Universiti Teknologi Malaysia using the facilities of gamma ray spectroscopy system with high purity germanium detector (HPGe) of efficiency 20%.

Granite samples were collected from Hagar El-Mlik area, 2 km from the central of Kadugli city in southern Kordofan state, Sudan. The rock was crushed and ground to fine powder and sieved with a particle size less than 120 μm. To calculate the concentrations of 238U and 232Th in the granite rock, standard reference materials provided by International Atomic Energy Agency (IAEA) was used.

The average of elemental concentrations and specific activity of uranium were obtained in the range (1.8 ± 0.11) to (0.80 ± 0.08) ppm, and (22.11 ± 1.30) to (9.79 ± 0.98) Bqkg-1 respectively, while (16.22±1.84) to (7.45±1.34) ppm and (65.42±7.40) to (29.50 ± 5.39) Bqkg-1 are the average concentration and specific activity of thorium. Moreover, average activity concentrations (Bqkg-1) for granite samples have been compared with the typical values of different countries.

232Th shows high activity concentration (65.42±7.4) Bqkg-1 whereas, 238U activity value is distinctly lower than the corresponding ones obtained from other countries and, in general, all results are acceptable and fall within the range given in UNSCEAR report 1993.