Determination of the composition of a gas mixture in a nuclear fuel rod byan acoustic method

Non-destructive evaluation is widely used in nuclear power plants in order to ensure security by studying the evolution of numerous parameters and per forming modelling. We describe a non-destructive method based on acoustics in order to determine the composition of the helium-xenon mixture in the fr ee volumes of fuel ros in pressurised water reactors by measuring the time- of-flight. A thermodynamic model based on a virial type expansion is used t o relate the ultrasound velocity in the gas mixture to its composition and the ultrasound velocity in one gas to its pressure. Thus we present an orig inal application of acoustics to be used as a non-destructive testing metho d in the nuclear industry.