The back-pressurising technique of leak-testing

Abstract The technique of leak-testing sealed objects is examined in which the object is first pressurised in a tracer gas and afterwards tested for re-emission of the gas. The minimum siz maximum sizes of leaks detectable are evaluated as functions of the sensitivity of the detector, the applied pressure and time of pressurising, the time lapse before the final tests, and the internal volume of the object. Formulae are derived for specifying pressurising conditions for desired sensitivities and for determining sensitivities resulting from a given test. Examples are quoted from practical experience in leak-testing fuel elements for nuclear reactors.