| Popis: |
In 1986 and 1987, neutron noise measurements were made in two Swedish BWRs on a number of detector strings, in order to detect and quantify detector guide tube vibrations, and possibly impacting. Vibrations of various amplitude were detected in several strings, but quantification of the strength of vibrations, including impacting, was not trivial. For quantification of the vibrations, there appeared a need for spectral descriptors other than just the amplitude of the vibration peak in the detector auto power spectral densities (APSDs). To find such descriptors, and investigate their sensitivity, numerical simulation of the signal of a vibrating detector both with and without impacting was performed. Two possible descriptors of impacting, namely the widening of the vibration peak and the distortion of the amplitude probability distribution (APD) function were investigated. The first of these two was found to be a relatively reliable indicator of impacting, in accordance with the experimental findings. The use of the APD is much less effective, and reasons for this are discussed in the paper. |
