VIBRATION MONITORING BY NEUTRON NOISE ANALYSIS AND ACCELERATION MEASUREMENTS INSIDE OPERATING NUCLEAR POWER REACTORS

摘要

A miniature biaxial in-core accelerometer has been inserted temporarily inside the Travelling In- corernProbe (TIP) systems of operating 1300 MWel Boiling Water Reactors (BWR) during full powerrnoperation. In-core acceleration measurements can be performed in any position of the TIP-system. Thisrnprovides new features of control technologies to preserve the integrity of reactor internals.rnThe radial and axial position where fretting or impacting of instrumentation string tubes or otherrnstructures might occur can be localised inside the reactor pressure vessel. The efficiency and long-termrnperformance of subsequent improvements of the mechanical or operating conditions can be controlledrnwith high local resolution and sensitivity. Low frequency vibrations of the instrumentation tubes werernmeasured inside the core. Neutron-mechanical scale factors were determined from neutron noise,rnmeasured by the standard in core neutron instrumentation and from displacements of the TIP-tubes,rncalculated by integration of the measured in core acceleration signals. The scale factors contribute tornqualitative and quantitative monitoring of BWR internal’s vibrations by the only use of neutron signals.