Experimental and numerical analysis of rarefaction wave propagation across an orifice plate with varying thickness and diameter

Abstract

Loss Of Coolant Accident causes the propagation of a transient rarefaction wave within the primary circuit that generates a transient pressure load on the baffle surrounding the reactor core. This is the result of nonidentical travel times of the rarefaction wave between the two sides of the baffle: the reactor core on one side and the by-pass between the baffle and core barrel on the other. The two zones have different geometrical characteristics, in particular the perforated reinforcement plates in the by-pass significantly influence wave propagation. Representing these obstacles in numerical simulations of the primary circuit requires the use of simplified models. A study on the accuracy of these models is hereby proposed, through a detailed comparison between numerical simulations realized with the EUROPLEXUS software and experimental results obtained on the MADMAX facility. The numerical models investigated are both quite reliable for the simulation of the case study under consideration. Both models imply a simplified representation of the real geometry of the experimental device, but despite this they can be considered quite valid. Lastly, the Fluid-Structure Interaction calculations enable us to comprehensively assess the phenomenon of cavitation and provide an initial evaluation of the deformations and mechanical stresses experienced by the structure.

Keywords

• loss of coolant accident (loca)
• simulation
• experiment
• perforated plates
• rarefaction wave
• finite elements
• finite volumes
• 2d axisymmetric
• 1d
• impedances
• fluid-structure interaction (fsi)