Indoor Exposure to Environmental Gamma Radiation in some selected Locations in Ibadan, Southwestern Nigeria

Indoor exposure to Gamma radiation was investigated by using LiF thermoluminescent dosimeters (TLDs), which were placed within some family dwellings built with cement, mud and baked clay in various locations in Ibadan for a period of 60 days. The study area was divided into ten zones. A total number of 75 TLDs made of LiF that gives good luminescence on heating were used to measure the indoor exposures in 75 family dwellings. The dosimeters were first heated to 300oC ( 573K) for about 16 hours in an annealing oven and then cooled at 80oC (353K) for 17 hours. The TLDs were then calibrated to read absorbed dose in microsieverts (?Sv) and then packaged inside polythene sachets. Within each building, a dosimeter was hung near the wall at a height of 3m. Routine checks were made on the dosimeters regularly. After the exposure for 60 days, the TLDs were removed from within the buildings and then read using the SOLARO 654 TLD reader. Results show that highest absorbed dose was observed in houses built with cement while the least was observed in dwellings of mud. Keywords : Absorbed dose, Indoor exposure, Thermoluminescent dosimeter, gamma radiation