A scaling law of pressurisation time in the case of Loss Of Vacuum Accidents (LOVAs): Theoretical and experimental analysis

Highlights: • An adimensional model to scale LOVA events has been developed. • The model has been validated with experimental measurements in a scaled facility. • The model has been applied to the ITER vessel: long time to take countermeasures. -- Abstract: The Loss Of Vacuum Accident is one of the hazardous events that may occur in nuclear fusion power plants which work with the magnetic confinement technology. During these accidents, the intake of air may re-suspend toxic, explosive and radioactive dust, involving a hazardous release in the external environment. Several studies have been conducted in scaled facilities, in order to investigate and understand how the phenomenon works. In the previous studies, the authors replicated these events in several different conditions by means of the scaled facility called "STARDUST-Upgrade", providing a good description of the phenomenon. A Computational Fluid Dynamic (CFD) code able to replicate these events has been developed and validated. Once a scaled experiment is realized, a specific analysis must be performed to understand if the phenomenon can be scaled and in what conditions. A result obtained in STARDUST-Upgrade, that is much different in terms of size and shape from a real TOKAMAK, must be modified by an adequate scaling law. The aim of this work is to analyse how to deduce a scaling law (for large scale flow) by a theoretical analysis based on the Buckingham π theorem. The authors will present also the experimental analysis provided to validate some features of this model. The conclusion of the work will be the use of the scaling law to obtain technical information (pressurisation time) about a LOVA inside an ITER-like reactor and further fusion power plants.