Environmental Radiation Monitoring Using Thermoluminescence Dosimetry in Kwavonza Area, Kitui County

Abstract

Exposure to ionizing radiation can cause health hazards. The annual effective dose from both natural and man-made radiation sources globally is about 3 mSv. Of this dose, 80% (2.4 mSv) comes from natural background radiation, although these levels vary greatly from place to place. Mineral rich areas usually experience high levels of environmental radiation because radionuclides that occur alongside these minerals deep underground are exposed to the surface during the process of mining. The objective of this study was to determine environmental gamma radiation levels in Kwa-Vonza area, Kitui County. This is because Kitui County is a mineral rich region that has been mapped for future mining operations which may result in exposure to high levels of ionizing radiation thereby causing radiation related health hazards. Thermoluminescence technique together with a NaI(Ti) based survey meter were used to measure the exposure levels. Thermoluminescence dosimeters made of CaF2: Dy (TLD- 200) were prepared and deployed to the study area for a period of one month. They were then withdrawn and read using a Thermoluminescence card reader to determine the dose and dose rates. The results ranged between 4 - 63 nGy h-1 while the average absorbed dose was 29.33 ± 15.86 nGy h-1. This gave an annual effective dose equivalent of 0.188 ± 0.019 mSv y-1 which is much lower than the 1 mSv y-1 maximum allowed occupational dose set by the ICRP