ESTIMATION OF COLLECTIVE EFFECTIVE DOSE DUE TO NATURAL BACKGROUND-RADIATION IN EGYPT

During the last few years, worldwide attention has been directed towar ds the estimation of natural background radiation levels. Several envi ronmental monitoring networks have been established for systematic dat a collection and exchange of information. In the Present study, measur ements of annual effective dose from terrestrial gamma-rays are carrie d out at pre-selected sites within several Egyptian governorates by us ing a calibrated gas-filled GM-detector connected to a microcomputer s ystem. Contribution of the secondary cosmic-rays, which is of prime im portance at sea level, is achieved by carrying out computation based o n theoretical considerations. Terrestrial effective dose in Egypt is f ound to be between 106 and 371 mugSv/yr, meanwhile the computed cosmic rays contribution is 260-296 muSv/yr. Accordingly, the annual collect ive effective dose due to natural background radiation is about 27,253 Man Sv for the last Egyptian population count (1989) considering 0.8 and 0.2 indoor and outdoor occupancy factors.