Static and dynamic hydroelastic instabilities in MTR-type fuel elements Part I. introduction and experimental investigation

Abstract Hydroelastic instabilities that occur in MTR-type flat-plate fuel elements have been studied both experimentally and theoretically. The present Part I of the paper reports on the experimental part of the investigation, in which three mock-up plate assemblies were tested from the hydroelastic stability viewpoint. A flow loop was built in which the three assemblies could be subjected to water flow rates, the maximum of which corresponded to 3.5 times the Miller's velocity of the assembly. The plates were instrumented with strain gauges, by means of which both static and dynamic deflection measurements could be made. In addition, it was possible to measure the static pressure profiles in three adjacent coolant channels. The experiments indicated that MTR-type fuel elements are subject to several hydroelastic instabilities. These instabilities were identified as: static divergence at the leading edge, static deformation in the plate array, a low-amplitude vibration in the form of traveling waves, and a high-amplitude vibration or flutter. A support comb across the leading edge of the plate assembly was found to remove the leading-edge static divergence and the flutter instabilities. A time-dependent theoretical analysis of the observed phenomena is to be reported in part II.