A finite element model method was developed to evaluate fluid structure interaction between core support structures and reactor coolant during rapid Loss Of Coolant Accident (LOCA) conditions in Pressurized Water Reactors (PWR’s). The hydraulic behavior of the reactor coolant was modeled using a series of contained fluid elements linked to the structural elements using linear constraint equations. An advantage of this method is the significant reduction in the number of contained fluid elements required to accurately represent the fluid structure interaction. A large volume of fluid may be modeled by a single contained fluid element without compromising detail in the finite element representation of the structure. This three-dimensional finite element method represents an expansion of the two-dimensional methods presented by Riddell and Schwirian (1983).
To provide verification of the method, finite element analysis results produced for a benchmark analysis were compared directly to a series of hydraulic pressure pulse tests performed previously. The typical hydraulic pulse evaluated had a pressure ranging from 0 to 1200 psig with a duration of less than 40 msec. Good agreement was observed between test and analysis results.