Evaluation of natural radionuclides at Um-Greifat area, eastern desert of Egypt

Air borne radiometric maps and remote sensing techniques were used to explore for the occurrence of radioactive materials. The previous techniques recorded radioactive mineralization for the first time along the NW-SE trending fault zones within the Miocene clastic-carbonate sediments. In the present study, gamma-ray spectrometry was used to confirm the presence of this mineralization. Concentrations of radionuclides, associated within the iron ochre at Um-Greifat area, have been measured, using a hyper-pure germanium spectrometer. The variation in concentration of radionuclides for the area under investigation can be classified into A, B and C regions of high, medium and low natural radioactivity. In region A, average concentration in Bq kg(-1) has been observed to range from 1858 to 4062 for U-238, between 29 and 151 for Th-232, from 60 to 136 for U-235 and between 46 and 409 Bq kg(-1) for K-40. Radium equivalent activities (Ra-eq) in addition to external and internal hazard indices (H-ex, H-in) have also been determined. Ra-eq varies between 1901 and 4307 Bq kg(-1), which exceeds the permitted value (370 Bq kg(-1)) and H-ex and H-in are higher than 1. The high activity concentration within region A points to an environmental hazard, while regions B and C have less exposure effect on human beings. (C) 2003 Elsevier Science Ltd. All rights reserved.