Pyrolysis of nuclear reactor circulator oil in carbon dioxide

Abstract

The ingress of circulator oil into the carbon dioxide coolant of a nuclear reactor can cause problems such as the deposition of carbon on the fuel elements. This paper describes the first stage of degradation when oil is pyrolysed, in carbon dioxide at temperatures between 600 and 900°C, and in helium at 900°C, for 20s. The degradation products were determined using gas chromatography with either a selective carbon monoxide monitor or a flame ionization detector. The chromatograph was combined with a mass spectrometer for the identification of the degradation produces. Hydrogen, carbon monoxide and a wide range of hydrocarbons are the initial degradation products. The amounts of individual reaction product, and the total amount formed ( P) increased with pyrolysis temperature, T, according and the total amount = 1/ T. The sensitivity to temperature of product formation varied from one product to another. Formation of carbon monoxide was least sensitive to temperature. It is clear that a chemical reaction takes place between the oil and carbon dioxide since the total amounl of product produced is much greater in carbon dioxide than in helium and the relative amounts of product produced in carbon dioxide differ considerably from those produced by pyrolysis in helium: for example, no carbon monoxide is detected when the oil is pyrolysed in helium.