TITLE:
Effect of Radioactive Minerals Potentiality and Primordial Nuclei Distribution on Radiation Exposure Levels within Muscovite Granite, Wadi Nugrus, Southeastern Desert, Egypt
AUTHORS:
S. F. Hassan, M. A. M. Mahmoud, M. A. E. Abd El-Rahman
KEYWORDS:
Muscovite, Peraluminous, Uranium, Radiation Exposure Levels, Radon Concentration
JOURNAL NAME:
Journal of Geoscience and Environment Protection,
Vol.4 No.3,
March
23,
2016
ABSTRACT: The studied
area at Wadi Nugrus, Southeastern Desert, Egypt, is located between lat. 24°41'00''
and 24°41'35''N and long. 34°36'47'' and 34°37'09''E. The rock types
are represented by layered metagabbros, biotite schists, gneisses, granodiorites,
and Muscovite granites. The muscovite granite of Wadi Nugrus, is small exposure
in size (~5.0 km2), emplaced along NW-SE trend, with about 0.5 - 4.5
Km in length and 100 - 250 m in width and intruding the biotite schists. The studied
muscovite granite is composed mainly of plagioclases, potash feldspars, quartz,
biotite and muscovite. The recorded minerals assemblage can be classified into secondary
U-minerals (uranophane and meta-autunite), U-bearing minerals (uranothorite and
columbite) and accessory minerals (zircon, flourite, allanite, zinnwaldite and hematite).
The U/eU is more unity where, the measured chemical uranium is higher than the measured
equivalent uranium in the most analyzed samples especially in trenches, which reflect
disequilibrium state. The activity concentrations range from 251.72 to 1096.2 Bq·kg-1 for 232Th, from 494 to
2593.5 Bq·kg-1 for 226Ra, and from 1314.6 to 1846.7 Bq·kg-1 for 40K. The obtained radiological data show that the average internal
and external hazard indices are 9.11 and 5.78, respectively which are more than
unity and highly exceeding the permissible limits (International Commission on Radiation
Protection, ICRP). The internal and external hazards are mainly due to 226Ra
nuclei while the absorbed dose rate (nGy/h) is related to 232Th nuclei.
The contributions of the three nuclei in the total absorbed dose rates and internal
and external hazardous, for 226Ra, it contributes by 72% in Hin,
57% in Hex and 55% of DR, for 232Th it contributes
by 24% in Hin, 37% in Hex and 36.9% of DR, while
for 40K it contributes by 4.1% in Hin, 6.4% in Hex and 8.1% of DR.