Study of the behavior of thermal shield support system for the French plants Original Research Article

Degradation/failure of thermal shield support system in PWRs has been observed in the US as well as in foreign plants. In almost all cases, remedial actions were put in place at very high economic cost to the utilities only after the failures had occurred. This paper presents the results of a comprehensive study to predict the long-term behavior of a thermal shield support system due to flow-induced vibratory loads and thermal transients. Excellent agreement from the system finite model between the measured plant test data on the barrel/thermal shield beam and shell mode frequencies and the flexure strains confirms the basic structural behavior and physics of the flow induced vibrations. Loads and stresses on the support bolts and the flexures were determined to predict the fatigue life of the components.