Determination of Activity Concentration of Natural Radionuclides and Radiation Hazards' Assessment of Building Materials in High Background Radiation Areas of Homa and Ruri, Kenya.

Willis Otieno Gor Odongo,Charles Rotich,Shinji Tokonami,Kranrod Chutima,Nadir Hashim,Margaret Chege,Karoly Nemeth

doi:10.1155/2021/9978619

Abstract

The areas around Homa and Ruri hills in Homa Bay County in Kenya are associated with high background radiation levels. The activity concentration of the natural radionuclides (226Ra, 232Th, and 40K) in earthen building materials used in the areas of Homa and Ruri hills has been measured using a NaI (Tl) detector in this work. The measured values of radioactivity concentrations are used to estimate the associated radiological risk. The earthen building material samples from Ruri registered relatively high 232Th concentration values averaging 1094 ± 55 Bq/kg, nearly three times those of the samples from Homa. 226Ra level was not significantly different in both regions with Homa reporting 129 ± 10 Bq/kg and Ruri 111 ± 6 Bq/kg. 40K was however higher in the samples from Homa by an approximate factor of 2 relative to those from Ruri where the activity concentration was 489 ± 24 Bq/kg. The radium equivalents for 226Ra, 232Th, and 40K in the samples from Ruri were 111 ± 9, 1564 ± 125, and 38 ± 3 Bq/kg, while in Homa, the values were 129 ± 10, 570 ± 46, and 69 ± 5 Bq/kg, respectively. The calculated value of total radium equivalent in Ruri was 1713 ± 137 Bq/kg which was two times higher than that of Homa. 232Th contributed about 74% and 91% to the total radium equivalent in Homa and Ruri, respectively; thus, it was the one with the largest contribution to radiation exposure in both regions. The average indoor annual effective dose rates were 1.74 ± 0.14 and 3.78 ± 0.30 mSv/y in Homa and Ruri, respectively, both of which were above the recommended safety limit of 1 mSv/y.

Highlights

There are no data on radiation exposure as a result of the terrestrial radionuclides inside the local earthen dwellings in Homa and Ruri which this research seeks to determine. is paper reports the activity concentration of the primordial radionuclides in the earthen building materials used in the two regions as well as the risk indices associated with them
Indoor annual effective absorbed dose rate is the measure of biological effect of radiation on humans inside a dwelling made of the soil
The activity concentration of 226Ra had no significant difference between them with average values of 129 ± 10 Bq/kg and 111 ± 6 Bq/kg. respectively. e average value of 232 was approximately 60% higher in Ruri compared to Homa which had an average of 399 ± 20 Bq/kg; this was attributed to the ring intrusion of monazite and pyrochlore minerals in Ruri associated with higher thorium concentration [13]

Summary

Introduction

Natural radiation in the environment contributes approximately eighty percent of the total radiation exposure to the general public. e major categories of natural exposure include inhalation of radon and thoron, external exposure from (226Ra, 232 , and 40K), cosmic radiation, and ingestion of food and water [1]. e major natural contributors to external exposure are the primordial radionuclides 226Ra, 232 , and 40K which are not uniformly distributed in the environment but occur in varying quantities in rock and soil as characterized by the geology of a region [2]. e average worldwide dose rate as a result of these terrestrial radionuclides is about 60 nGy−1 for areas with normal background. erefore, it is important to determine their levels in soil and rocks, as well as their individual contributions to the total radiation dose for purposes of radiation protection and management [3]. For instance, in high background radiation areas of Ramsar, Iran [11], and Mrima hill, Kenya, have shown e Scientific World Journal that building materials contribute significantly to indoor radiation exposure. Erefore, there exist a potential radiation risk indoors from the soil used as the building material in these regions and the fact that people generally spend more time indoors. Despite this apparent risk, there are no data on radiation exposure as a result of the terrestrial radionuclides inside the local earthen dwellings in Homa and Ruri which this research seeks to determine. E radionuclides responsible for the highest radiation exposure are determined

Methodology

Experimental Techniques

Kilometers