Fluid-structure interaction analysis of a deck structure during a HCDA

Presented here is an assessment of the structural integrity of the deck structure of a pool-type LMFBR during a Hypothetical Core Discruptive Accident (HCDA). During this accident the sodium above the core is propelled upward until it impacts against the deck structure. This hydrodynamic loading could procedure (1) significant structural damage and (2) sodium leak paths. The deck is a three-dimensional composite structure of beams, plates and concrete fill. It is supported at its outer periphery by steel columns embedded in the surrounding concrete, radial biological-shield. The deck provides top closure for the main tank and support for the intermediate heat exchangers, primary pumps, rotating plugs, and primary and secondary tanks. A finite-element model is used to study the deck dynamics during slug impact. By using the symmetry of the system, a sector model which accounts for the salient features of the system is developed. The main radial I-beam, component support I-beam and bottom annular plate are modeled using triangular plate elements. The concrete fill is modeled using hexahedral continuum elemente. Using the above finite-element model the dynamics of the deck during a HCDA are investigated. The structural stiffening effect of the concrete fill on displacement response is studied by comparing results obtained from two cases. The first case accounts for both the mass and structural effects of concrete and the second only accounts for the mass effect. Results are presented for deck displacement and velocity histories and deck support column reaction forces. (orig.)