Liquid Scintillation Counter Cocktail Decomposition in Supercritical Water

Using supercritical water oxidation, a liquid scintillation counter cocktail used for the analysis of radionuclides was decomposed quickly and completely to water and carbon dioxide. The decomposition yield of the liquid scintillation counter cocktail increased with the reaction time, temperature, and pressure. More than 99.96% of the liquid scintillation counter cocktail decomposed with hydrogen peroxide at 773 K and 30 MPa for 3.8 min of reaction time. The liquid scintillation counter cocktail decomposed through two main reaction pathways: One had a rate-controlling intermediate whose decomposition rate was very slow and the other did not have stable intermediates. The decomposition of the rate-controlling intermediate was a significant factor in the complete decomposition of the cocktail although it did not dominate the entire decomposition process. A simple kinetic model that estimates the decomposition yield of the liquid scintillation counter cocktail was developed.