Thermo-Elasto-Hydro-Dynamic Modeling of Hydrostatic Seals in Reactor Coolant Pumps

Abstract

EDF, the French energy company, has experienced some failures of mechanical seals in reactor coolant pumps in operation in recent years. So, a thermo-elasto-hydro-dynamic model of the first seal has been developed. The present model is a steady two-dimensional approach to characterize the seal behavior in normal operating conditions. The coupling between structure thermo-elastic deformations and the fluid flow is taken into account through influence coefficient matrices. Numerical results are successfully compared to operational results of the leak-flow rate. The effects of heat transfers, of mechanical deformation, and of thermo-mechanical deformation are compared. The influence of pressure drop and the injection temperature is described. The influence of the coning angle of the faceplates is underlined. The elastomeric secondary O-rings are also proven to be influential. The internal friction (between each element of the seal) and the external friction (between the seal ring and the surrounding stationary element) are introduced in the model in order to reproduce the hysteretic behavior of the seal. The development of this model leads to a better knowledge of the behavior of a critical component.