Detailed measurements and analyses of the neutron flux oscillation phenomenology at Kernkraftwerk Goesgen

Recent investigations on measured neutron flux noise at the Kernkraftwerk Goesgen-Daeniken are summarised. The NPP in operation since 1979 is a German KWU pre-KONVOI, 3-Loop PWR with a thermal power of 3,002 MWth (1,060 MWe). In a period of approx. 7 cycles from 2010 to 2016, an increase of the measured neutron noise amplitudes in the in- and out-core neutron detectors has been observed, although no significant variations have being detected in global core, thermohydraulic circuits or instrumentation parameters. Verifications of the instrumentation were performed and it was confirmed that the neutron flux instabilities increased from cycle to cycle in this period. In the last two years, the level of neutron flux noise remains high but seems to have achieved a saturation state.