A coupled fluid-solid model to investigate leak rates for leak-before-break assessments

A multiscale model is discussed here which incorporates fluid mechanics into a structural model. This is so that leak rates can be output from a crack in a finite element model without any complex meshing or post processing. The model can be implemented into any standard finite element solver, meaning leak rates can be investigated for cracks in realistic components. Crack opening area is obtained directly from the special elements that surround the crack, and leak rate is output with the solution. By adopting this holistic approach, it makes the calculation of leak rate more efficient, with the added benefit of higher accuracy. Furthermore, this provides a tool to investigate thermal interactions between the fluid and solid. Presented in this paper is a description of the physical model, and an outline of the numerical solution procedure. Leak rates are also discussed for the case of crack in a plate. The numerical tool provides an effective way of coupling a fluid model with microscale effects, to a macroscale solid model. Investigations using this new method have the potential to reduce uncertainty in leak rate evaluation. Also, by reducing the uncertainty, it is suggested that there would be an increase in the number of situations where Leak-before-Break could be applied in Nuclear Power Plants.