[en] The use of noise diagnostics is described in the early detection of failures in the operation of a nuclear power plant. Reactor noise is classified by noise source and noise carrier. Noise analysis is used for early diagnosis of failures of the integrity of components of the primary circuit, the failure of detectors, the incorrect function of cable routes and anomalies in the thermohydraulic process. The method is based on processing the stochastic signal which is usable for the interpretation of various phenomena. Most frequently aplied is neutron noise diagnostics (frequency range 0 - 50 Hz) using standard instrumentation without disturbing the operation of the reactor core by installing additional instruments. In-pile detectors of neutron flux density serve the detection of anomalies in coolant flow, of dangerous vibrations of fuel and regulating assemblies, and of local boiling. The results of the measurement of neutron noise carried out in pressurized water reactors are generalized. (J.C.)