Analysis of the HDR blowdown experiment using a weakly coupled fluid-structural dynamic method

The methodology and results of B and W's prediction of the German HDR blowdown experiment number V31/V31.1 are presented. The test is designed as a full-scale PWR LOCA simulation. The analysis is based on a weakly coupled structural priority approach to the coupled fluid-structure problem. The hydraulic forcing function is computed first using a one-dimensional non-steady finite difference representation of the conservation equations. Structural boundaries are assumed rigid. Thus, computation of the actual pressure transient is precluded. Structural analysis is performed with a finite element lumped mass computer program. Only beam modes are considered. Fluid-structure coupling is accounted for by a separately generated hydrodynamic mass matrix. The hydraulic forcing function and the hydrodynamic mass matrix form the input basis to the structural dynamic analysis. Analytical results are described and compared favorably with measurements. The rigid boundary assumptions are shown to be conservative. (orig.)