THE CONCENTRATION OF NATURAL RADIATION SOURCES (NRS), MAINLY 238U, 232Th, and 40K, IN BUILDING MATERIALS (SAND, CLAY BRICKS, AND CONCRETE BLOCKS) USED ALONG KANGUNDO ROAD, NAIROBI KENYA

This research aimed at assessing the concentration of Natural Radiation Sources (NRS), mainly 238U, 232Th, and 40K, in building materials (sand, clay bricks, and concrete blocks) used along Kangundo Road in Nairobi City County. Human exposure to ionising radiation is largely due to Natural Radiation Sources (NRS). These radioactive elements with long half-lives are found in the Earths lithosphere and in construction materials with radiation levels varying due to their geology. A purposive random sampling method was deployed in this work to collect samples of building materials for analysis. The radioactivity concentration levels in the sampled building materials were determined using a NaI (TI) spectrometer at Kenyatta University laboratory. The activity concentration of 40K varied from 151 ± 8 to 2392 ± 120 Bq/kg, 238U varied from 27 ± 2 to 412 ± 21 Bq/kg and 232Th ranged from 54 ± 3 to 612 ± 31Bq/kg. More than 70 per cent of the samples analysed had activity concentration surpassing the world permissible limits of 420 Bq/kg, 33 Bq/kg, 45 Bq/kg for 40K, 238U and 232Th respectively. The study therefore recommended that assessment of radioactivity concentration for samples with high radioactivity values.