NATURAL RADIONUCLIDE CONCENTRATIONS IN GRANITE ROCKS IN ASWAN AND CENTRAL-SOUTHERN EASTERN DESERT, EGYPT AND THEIR RADIOLOGICAL IMPLICATIONS

摘要

Different types of granites, used extensively in local construction, were collected from five localities in Egypt, namely: Abu Ziran (Central Eastern Desert), Cabal El Maesala (Aswan) and three areas from Wad! Allaqi, (Gabal Abu Marw, Gabal Haumor and Gabal urn Shalman), in the South Eastern Desert. Granite samples were studied radiologically, petrographically and geoehemically. The contents of natural radionuciides (~(226)Ra, ~(232)Th and ~(40)K) were measured in investigated samples by using gamma spectrometry [Nal (Tl) 3'×3']. The activity concentrations of~(226) Ra, ~(232)Th and ~(40)K in the selected granite samples ranged from 9 ± 0.5 to 111 ±7, 8±1 to 75 ± 4 and 100 ±6 to 790±40 Bq kg~(-1), respectively. The external hazard index (H_(ax)), absorbed dose and annual effective dose rate were evaluated to assess the radiation hazard for people living in dwellings made of the materials studied. The calculated radium equivalents were lower than the values recommended for construction materials (370 Bq kg~(-1)). The excess lifetime cancer risks were also calculated. Petrographieally, the granites studied are varied in the form of potash-feldspar, quartz, pisgioclase, mica and hornblende. The accessory minerals are zircon, apatite and allanite. Geochemically, the chemical composition of the granite is studied especially for major oxides. They are characterized to have SiO_2. K_2O, Na_2O and AI_2O_3 with depletion in CaO, MgO, TiO_2 and P_2O_5.