Measurement of Attenuation Coefficients of Gamma Rays in Selected Local Shielding Materials

Gamma radiation shielding is an important consideration in the design of nuclear medicine facilities, industrial radiography sites, and research reactor installations across Nigeria. The linear and mass attenuation coefficients of local materials determine their effectiveness in reducing gamma radiation dose. This study measures the linear attenuation coefficients of five locally available shielding materials, including ordinary concrete, laterite-cement composite, lead glass, lead sheet, and water, for cobalt-60 gamma rays at 1.17 and 1.33 MeV using a collimated NaI(Tl) scintillation detector and narrow beam geometry. Measurements are performed at the Centre for Energy Research and Training at Ahmadu Bello University, Zaria, using a Co-60 calibration source. Half-value layer and tenth-value layer thicknesses are computed from the measured attenuation data. Results indicate that lead sheet provides the highest attenuation with a half-value layer of 12.4 mm, followed by lead glass at 23.1 mm. Laterite-cement composite, composed of 70 percent laterite and 30 percent Portland cement, achieves a half-value layer of 78 mm, comparable to published values for ordinary concrete. The laterite composite offers a cost-effective locally sourced alternative for lower-activity shielding applications in North West Nigeria. Keywords: gamma attenuation, shielding materials, attenuation coefficient, cobalt-60, radiation protection