Abstract:
In this study, epithermal neutron activation analysis (ENAA) technique was implemented for
the first time at 3 MW TRIGA research reactor of Bangladesh Atomic Energy Commission
(BAEC) to determine elemental concentrations in soil/sand samples and characteristically
compared it with instrumental neutron activation analysis (INAA) technique to find out
advantageous features of ENAA over INAA. The assessment of three parameters (detection
limit, analytical sensitivity and Q0 values) using standard reference materials (IAEA-SL-1 and
IAEA-Soil-7) indicate that ENAA is more preferable to INAA for the determination of low
levels of Arsenic (As), Antimony (Sb), Samarium (Sm) and Uranium (U) in soil/sand samples.
In this study, total concentrations of 20 major, minor and trace elements including Th and U
in surface and depth-wise inland and beach sands of potential regions of Bangladesh (Cox’s
Bazar, Potenga, Kuakata, Moulvibazar, Sylhet, Rajshahi and Sherpur) were determined by
INAA and ENAA to deduce origin and extraction possibility of Th and U. The concentration
ranges in the beach sands were from 4.63 to 382 mg/kg for Th and from 0.73 to 132 mg/kg
for U whereas for inland sand, from 0.55 to 20.8 mg/kg and 0.97 to 4.57 mg/kg, respectively.
From the concentration data of Th and U in inland and beach sands, the enrichment factor of
Th and U, as well as their extraction possibilities, have been discussed. The depth-wise
concentration variations for Th and U in beach and inland sands reveal that the overall U
concentration variation decreases top to the deeper layer, but this variation in beach sands is
higher than that of the inland sands of Bangladesh. The statistical analysis namely the Pearson
correlation study reveals that high levels of Th and U in beach sands are due to the presence
of Th and U rich heavy minerals in Cox’s Bazar beach sands. The natural radioactivity
concentrations (232Th, 238U and 40K) and radiological hazard indices indicate that average
radioactivity concentrations of 232Th and 238U in Cox’s Bazar beach sands are relatively higher
than those at other studied areas of Bangladesh as well as the world average values. However,
external hazard indices at most of the sampling points are below the safe limit.
