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

Crude oil terminal sludge contains technologically enhanced naturally occurring radionuclides such as 232Th, 238U, 228Ra and 226Ra, 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 232Th, 238U, 228Ra and 226Ra present in the sludge during combustion at a certain temperature and time. The percentage of volatilization was found to vary between 2% and 70%, 238U was the most volatile in comparison with 232Th, 228Ra and 226Ra. 238U 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 232Th, 238U, 228Ra and 226Ra contained in the sludge. With this known percentage of volatilization, the concentration of 232Th, 238U, 228Ra and 226Ra present in the bottom and filter ashes can be calculated.