Detection of subcooled boiling in a PWR using noise analysis and calculation of the steam void fraction

In a 1300 Mw pressurized water reactor (PWR) the temperature fluctuations of thermocouples situated above the core as well as the neutron noise of self power neutron detectors (SPNDs) located in the upper part of the core were analyzed and subcooled boiling was detected. The changes observed in the noise functions due to the presence of bubbles were compared to the behaviour of the same functions measured by other authors during boiling simulated experiments. The cross-sectional average volumetric void fraction was calculated following a profile-fit model of subcooled boiling and used to interpret the temperature and neutron fluctuations measured in the PWR.