MODAL ANALYSIS OF A NUCLEAR REACTOR WITH FLUID- STRUCTURE INTERACTION: ADDED MASS AND ADDED STIFFNESS EFFECTS

摘要

The present paper is related to the modal analysis of a naval propulsion ground prototype nuclear reactor with fluid-structure interaction modeling. Many numerical methods have been proposed over the past years to take fluid-structure phenomenon into account in various engineering domains, among which nuclear engineering in seismic analysis.The purpose of the present study is to apply general methods on a global approach of the nuclear reactor. A simplified design of the pressure vessel and the internal structure is presented; fluid-structure interaction is characterized by the following effects:? added mass effects are highlighted with the calculation of an added mass operator, obtained from a finite element discretisation of the coupled problem. The numerical model is developed within the Castem code using an axi-symmetric model of the industrial structure;? coupling effects between the external and internal structure via the confined inner fluid are also illustrated and numerically described with the added mass operator;? added stiffness effects are taken into account with an added stiffness matrix describing pre-stress effects due to a static pressure loading simulating the actual operating conditions of the reactor.The expected fluid-structure interaction effects on the nuclear pressure vessel and their numerical modeling leads to the definition of a global coupled model which can be used to perform a seismic analysis.