Behaviors of Th-323, U-238, Ra-228 and Ra-226 on combustion of crude oil terminal sludge

Crude oil terminal sludge contains technologically enhanced naturally occurring radionuclides such as Th-232, U-238, Ra-228 and Ra-226, thus cannot be disposed of freely without proper control. The current method of disposal, such as land farming and storing in plastic drums is not recommended because it will have a long-term impact on the environment. Due to its organic nature, there is a move to treat this sludge by thermal methods such as incineration. This study has been carried out to determine the behaviors of Th-232, U-238, Ra-228 and Ra-226 present in the sludge during combustion at a certain temperature and time. The percentage of volatilization was found to vary between 2% and 70%, U-238 was the most volatile in comparison with Th-232 Ra-228 and Ra-226. U-238 is found to be significantly volatilized above 500 C, and might reach maximum volatilization at above 700 C. A mathematical model was developed to predict the percentage of volatilization of Th-232 U-238, Ra-228 and Ra-226 contained in the sludge. With this known percentage of volatilization, the concentration of Th-232, U-238, Ra-228 and Ra-226 present in the bottom and filter ashes can be calculated. (C) 2003 Elsevier Ltd. All rights reserved.