Bubbles in the sensing line of nuclear power plant pressure transmitters: the shift of spectrum resonances

Noise analysis is a valuable tool when applied to predictive maintenance problems in nuclear power plants. When focused to the capacitive pressure sensors it can detect the presence of undesirable bubbles in the sensing line. From the noise signal power spectrum density a resonant peak shifting towards the lower frequency region, due to bubbles appearance, is observed. In this work an explanation for the peak displacement is given; besides, a method to estimate the void fraction from the shift is developed. Both results benefit the on-line maintenance of pressure sensors without disturbing plant operation.