Studies on the shielding properties of some Ghanaian hardwoods against x-rays
The linear and mass attenuation coefficients have been estimated for four selected Ghanaian hardwood species namely, Kruma (Klainedoxa gabonensis), Potrodom (Erythrophleum africanum), Dahoma (Piptadenia africana) and Odum (Milicia excelsa), using eight x-ray qualities from both high and medium filtered spectra generated by a Philips MG324 constant potential x-ray generator. For Kruma, of density 1050 kg m-3, the mass attenuation coefficients range from 0.0160 ± 0.005 to 0.0558 ± 0.005 m2 kg-1. For Potrodom of density, 900 kg m-3, the mass attenuation coefficients range from 0.0 172 ± 0.005 to 0.0457 ± 0.005 m2 kg-1. For Dahoma of density, 700 kg m3, the mass attenuation coefficients range from 0.0152 ± 0.005 to 0.0442 ± 0.005 m2 kg-1. For Odum of density, 650 kg m-3, the mass attenuation coefficients range from 0.0 138 ± 0.005 to 0.0485 ± 0.005 m2 kg-1. Experimental results show that for both high and medium filtered x-ray spectra, Kruma has the highest linear attenuation coefficient and as such, is the most efficient attenuator, followed by Potrodom, Dahoma and then Odum. Linear attenuation coefficients of Kruma and Potrodom have been found to be comparable to that of Gypsum wallboard, a material of density 700 kg m-3 used for shielding against scatter radiation in some diagnostic x-ray facilities. For instance, with 100 kV x-rays at high filtration, the average linear attenuation coefficient of gypsum wallboard reported from literature is 0.1778 x 10-2 m-1, whereas that for Kruma and Potrodom have been found to be 0.1786 ± 0.005 x 10-2 m-1 and 0.1727 ± 0.005 x 10-2 m-1 respectively. For 50 kV x-rays at medium filtration, the average linear attenuation coefficient reported from literature for gypsum wallboard is 0.5069 x 10-2 m-1, whereas that for Kruma and Potrodom have been found to be 0.4261 ± 0.005 x 10-2 m-1 and 0.3477 ± 0.005 x 10-2 m-1 respectively. From the half-value layer standpoint, for high filtered narrow x-ray beams at 100 kV, the corresponding values for Kruma, Potrodom, Dahoma and Odum are 38.81 mm, 40.13 mm, 55.45 mm and 67.16 mm respectively as compared to 39.62 mm for gypsum wallboard. For medium filtered beams the corresponding values at 100 kV are 25.75 mm, 28.06 mm, 44.95 mm and 49 mm for Kruma, Potrodom, Dahoma and Odum respectively. From this analysis, the wood species studied have the potential to be used as shielding materials against scatter radiation from x-rays in general radiography provided that one or two half-value thickness are considered depending on the attenuation factors required to comply with authorized dose rate limits.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of Master of Science Degree in Nuclear Physics, 2000