Structural dynamic analysis of BWR MARK II plant under SRV blowdown oscillation

This paper describes investigations conducted for the determination of SRV blowdown effects on structures, equipment and piping systems. The plant selected for this investigation has a combination structural arrangement which combines the Reactor, Auxiliary, Control, Fuel Handling, radwaste and dissel building into one nearly square shaped building with the primary steel containment and its concrete shield structure located at center of the common foundation mat. This combination building is reasonably symmetrical about both the N-S and the E-W axes and therefore could be treated as such to reduce analysis effort in the mathematical modeling and response calculations. Finite element techniques are used for the structural response investigations. The mathematical model consists of membrane and bending elements representing one half of the combination building resting on series of springs simulating the elastic half space of soil medium underneath the structure. The damping behavior of the structural system has been carefully determined with the assitance of two other studies involving the soil-structure interaction analyses. The mathematical model is then subjected to the SRV blowdown loads in the digitized form to determine structural responses at critical locations. In-structure response spectrum at selected locations are also generated. The results of these investigations are then used to examine the capabilities of other important items such as the reactor pressure vessel, the reactor internals and the steel containment under the influence of the SRV blowdown load simultaneously with other loads which can be reasonably postulated to occur at the sa