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 Bqkg(-1) has been observed to range from 1858 to 4062 for 238U, between 29 and 151 for 232Th, from 60 to 136 for 235U and between 46 and 409 Bqkg(-1) for 40K. 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 4307Bqkg(-1), which exceeds the permitted value (370Bqkg(-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.