In-situ non-contact pressure measurement of sealed units using acoustic methods

E Sharp and S Dixon
University of Warwick, UK 

This project concerns the development of a non-contact acoustic method to establish a measurement of internal pressure through analysis and simulation of resonant modes regarding an in-situ stainless steel cylindrical container housing special nuclear material. There are two types of investigating unit, each are composed of three parts. The inner containment, intermediate containment and outer containment, each of which have minor dimensional and material differences. There is concern that the future integrity of the outer containment may be compromised by several arising evolutionary processes, these include container corrosion, deterioration of the weld seals and an increase in the container’s internal pressure of the air gap between the intermediate and outer containment sections. It has been stipulated that the increase in internal pressure may be due to the process of radiolysis, in which hydrogen gas is produced within the sealed unit. This project seeks to identify a detection method that is suitable for generating and detecting vibrational modes of the sealed container within a hazardous environment, which could be used to indicate changes in internal pressure via the use of a non-contact technique.

Through this project, a non-contact and non-destructive method will be developed that is potentially more suited to automated or robotic inspection due to the non-contact requirement of the measurements to be taken when exciting vibrational modes of the sealed container. This may potentially be achieved by the use of electromagnetic acoustic transducers (EMATs), a method in which acoustic waves can be generated within a sample via a non-contact coupling technique. Furthermore, the use of a microphone as another detection method may also be studied. A number of factors will be considered, such as the optimal locations on the container to generate and detect resonant modes, the structural parameters of the sealed unit and the effect of external changes in temperature and atmospheric pressure on the measurements.