NATURAL RADIOACTIVITY AND RADIOLOGICAL RISK PARAMETERS IN LOCAL AND IMPORTED BUILDING MATERIALS USED IN SUDAN

摘要

Natural radioactivity levels in selected types of building materials used in Sudan were measured using gamma spectrometry. Radioactivity concentrations were measured in 52 samples including cements, porcelain ware, and ceramic tiles, cement blocks, and red clay bricks. Representative samples were powdered and stored in polyethylene Marinelli containers for four weeks to attain equilibrium between 226Ra and 232Th and their daughters before measurements. The average radioactivity (Bq.kg-1 ) of 226Ra, 232Th, and 40K, ranged between 12–40, 10–70, and 28–94, respectively in cement; 10–35, 12–28, and 87-143, respectively in cement blocks; 32–132, 26–87, and 285–1070, respectively in red bricks; and 8-527, 18–118, and 129–812, respectively in ceramics and porcelain tiles. The air absorbed dose rates ranged between 12.0±3.0 to 40.5±23.0 nGyh-1 in materials used in a superficial amount; 34.4±8.9 to 173.3±52.0 nGyh-1 in materials used in bulk. The annual effective doses were varied from 0.06 to 0.85 mSv. Excluding porcelain ware samples. The activity concentration indexes describing external and internal radiation hazards were within the acceptable limits. The study provides important baseline data for setting national regulatory control limits for protection against radiation.