الفهرس 
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Abstract
The present work dealing with estimation of dose rate from external outdoor exposure by using several techniques and systems. This was perfonned by making calibrations for the instruments which were used and intercomparison between them. Some environmental measurements were done by these instruments. The calibration factor (Ntll), was detennined for estimating the exposure rate at one meter abovee ground in field from natural radionuclides. A portable HPGe
detector was used for this purpose. The calibration factor, for energy lines of 238U, 232Th • series and 4<x are 64.95, 50.57 and 300.124 cps/f.lGyh-1 respectively. The concentrations of 238U, 232Th series and 4<x
in soil around the second research reactor by using this detector are
19.16,17.57 & 176.93 Bqkg-1 respectively. The concentrations of 238U,
232Th series and 4<x•in soil of the same site by using the fixed HPGe detector are 14.67 ,14.25 and 161.13 Bqkg-1 respectively. The calibration factors (Ntll) were detennined by using a portable Nal(Tl)
detector and were found to be 3.41, 0.46 and 1.91 cps/J.lRh- 1 for energy lines of 137Cs, 60Co and 152Eu respectively. The results of comparison between the portable and fixed HPGe detectors are; the difference between readings of the portable and fixed one is -7.51°/o.The sensitivity factor to convert from fixed HPGe to portable HPGe readings is 1.085. The results of calibration of commercial 1LD dosimeters, lithium foluride (cards) and calcium foluride (chips) and environmental measurements
are: For LiF material; The results of calibration of dose range, by using.