Absorbed alpha dose of allanite from Ombo, Palawan

Abstract

Mineral allanite from Ombo, Palawan contains appreciable amount of uranium and thorium, which are radioactive and may have significantly damaged their crystal structure. The amount of alpha dose absorbed by the mineral suggests to a certain extent, the level of damage within the crystal structure. This paper attempted to estimate the value of accumulated alpha dose absorbed by the mineral from individual measurements of uranium, thorium and lead using Gamma and Atomic Absorption Spectroscopy. Likewise, and using the obtained U-Th-Pb ratio, it was possible to correlate the geologic age of the samples. Experimental results revealed that the sample contains 0.015 ± 0.0008 %wt. uranium, 1.247 ± 0.027 %wt. thorium, and 0.00661 ± 0.000147 %wt. lead. The geological age and the accumulated alpha dose has been estimated to be around 115.5 ± 4.5 million years and 1.13 - 1.27 x 10¹⁵ α decay/mg respectively. In comparison with allanites from other sites, it seemed our sample was younger, have not accumulated significant radiation damage and more crystalline. Our results will prove to be useful in studies involving immobilizing nuclear waste forms, particularly the effects in the crystal structure of materials with relatively smaller radiation damage.