Full Program »

Seismic response of a nuclear fuel assembly: physical and numerical modeling

Physical modeling and dynamic finite element analysis are used to evaluate the seismic response of a scaled structure that mimics the highly complex ingredients of a full-scale nuclear fuel assembly during moderate to severe ground shaking caused by realistic earthquakes. The scaled nuclear fuel assembly along with its support structure is designed and analyzed under a variety of seismic loading conditions. The experimental design was assisted by a series of three–dimensional dynamic finite element analyses that considered various details of the complex structural system. The designed assembly and its support structure were then constructed and assembled on the six-degree-of-freedom shake table at the George Washington University Earthquake Engineering and Structures Laboratory and a large number of seismic experiments were performed to assess the performance of the experimental model. To validate the suitability of the analysis methods used in the design phase, a series of blind predictions were conducted before the structure was tested on the shake table. The following results of the numerical simulations were compared to the corresponding experimental measurements: natural periods of the structure, maximum lateral displacements, and lateral displacements at different locations along the height of the fuel bundle under the same base excitation. The comparisons revealed that in addition to the top and bottom boundary conditions of the fuel assembly, an accurate estimation of the damping ratios for the first three modes of vibration is crucial to the accuracy of the numerical simulations. The estimated values of damping ratios obtained by minimizing the errors between the simulated and observed response of the structure were used to predict the response of the assembly in a series of new seismic loading scenarios. The follow-on physical experiments based on these new scenarios were conducted to further validate the accuracy of the estimated damping ratios.

Author(s):

Morteza Rahimi Abkenar    
George Washington University
United States

Majid Manzari    
George Washington University
United States

Philippe Bardet    
George Washington University
United States

Noah Weichselbaum    
George Washington University
United States