Analysis of Natural Radioactivity in Coal and Ashes from a Coal Fired Power Plant

Abstract

Coal is widely used mineral due to its accessibility and abundance in nature. Coal contains naturally occurring radionuclides or Natural Occurring Radioactive Materials (NORM) from Uranium and Thorium series including their decayed daughters namely Uranium-238 (²³⁸U), Radium-226 (²²⁶Ra) and Thorium- 232 (²³²Th) along with Potassium-40 (⁴⁰K). These radionuclides which are a natural phenomenon are released to the environment and concentrated in the ashes resulting from the combustion process. Thispaper presents an evaluation of the radioactivity content found in the feed coal (FC), bottom ash (BA) and fly ash (FA) sampled from a typical coal fired power plant (CFPP). The samples were measured for activity concentration of several radionuclides namely ²³⁸U, ²²⁶Ra, ²³²Th and ⁴⁰K by using Instrumental Neutron Activation Analysis (INAA). The radiological hazard based on Radium Equilibrium (Ra_eq) and ExternalHazard Index (H_ex) was assessed. In this study the activity concentration of all radionuclides in FA was enriched much higher compared to BA and FC. This work found that the degree of enrichment determined by the Enrichment Factor (EF) is differed for bottom and fly ash. The results indicated that each sample have different radiological characteristics. For Ra_eq and H_ex the values calculated for the samples were acceptable and within the limit for construction material. Generally the results proved that the values obtained were much lower and complied with the Malaysia regulatory limit and global values.