Analysis of incore and excore neutron noise signals for a KWU PWR by correlation techniques

The results are reported of noise analysis of neutron flux values measured using standard instrumentation inside and outside of the pressurized water reactor in the Goesgen nuclear power plant in Switzerland. The results of measurement were compared for two operating conditions, viz., at the beginning of the fuel cycle at full reactor power and at the end of the fuel cycle at reduced reactor power involving the operation of only two out of three circulation pumps. Changes were observed in the relative motion of the core barrel and the reactor pressure vessel, such as the rotation of the plane of motion or vibration mode changes, which can be attributed to the asymmetry of coolant flow through the reactor pressure vessel. In-core measurements showed that a slight asymmetry in the coolant flow occurred in the core itself. (Z.M.) 8 figs., 10 refs