Damping of reactor internals

During normal operation, reactor internals are excited by random and deterministic forcing functions. The complex fluid elastic system formed by the internals structures and reactor coolant responds in numerous modes and depends on the modal damping coefficients. This paper presents and discusses the results of a study of internals damping using data obtained from wave analysis of PWR plant flow tests, and shaker tests. The paper discusses the application of the data to component design. Damping values reported are suitable for normal operation design conditions, i.e. for oscillatory behaviour and relatively small amplitudes. The extrapolation of the data to obtain realistic values for large seismic events and for loss of coolant accidents is also discussed briefly considering that for these faulted conditions, the amplitude of the response is much larger than for normal operation. (Auth.)