Abstract A case study is presented describing an analysis initiated by a real core event at Paks NPP Hungary. The analysis utilised the static data provided by the VERONA core monitoring system as well as the results from a specially organised series of measurements using the neutron noise signals from in-core Rh SPN detectors. It was demonstrated that the observed temperature rise imbalance was not caused by a power anomaly but by some partial flow blockage affecting a substantial part of the core. In addition to the static measurement results the actual coolant velocity within the affected and non-affected assemblies could be evaluated by using noise technique. By virtue of continuous analysis and monitoring the unit could be operated for a substantial part of the planned cycle length.