WELCOME LETTER Welcome

Seismic analysis model is required to evaluate themechanical structural integrity of reactor internals when earthquakeis occurred. Finite element method is used to prepare a seismicanalysis model for reactor internals. The reactor internals arecomplex mechanical structures, so much analysis time is requiredto obtain the seismic responses with the detail finite element model.A beam element model combined with fluid elements is introducedin order to reduce analysis time and provide convenience to handle,which is simplified from the detail solid model. The beam fluidelement model consists of BEAM4 elements, rotational springelements, MASS21 elements, and FLUID38 elements. BEAM4elements represent structures such as the reactor vessel, upperguide structure, and core support barrel. Rotational springelements were adopted to simulate a connection conditionbetween one cylinder and another cylinder. MASS21 elementsrepresent the fluid contained in cylinder and FLUID38 elements forthe fluid between cylinders. We obtained dynamic characteristics,natural frequencies and vibration modes, from both the beam fluid element model and structural vibration test. Thoughthe beam fluid element model for the scaled-down reactor internalshas a few hundred elements, the estimated natural frequencies arealmost the same as those obtained by vibration test. The beamfluid element model may be a useful analysis model to obtain thespectrum response of reactor internals for a seismic event. VERIFICATION AND VALIDATION FOR SIMULATION OFNUCLEAR APPLICATIONS 6-2 VERIFICATION AND VALIDATION FOR SIMULATIONOF NUCLEAR APPLICATIONS: PART 2 Wilshire B10:30am–12:30pm Session Chair: Hyung Lee, Bettis Laboratory, West Mifflin, PA,United StatesSession Co-Chair: Richard R. Schultz, Idaho NationalLaboratory, Idaho Falls, ID, United States Verification and Validation of Thermal-hydraulic SystemCodes for VVER Type Nuclear Power Plants