Neutron noise measurements on pressurized water reactors

Abstract

Noise analysis contributes to increase significantly understanding of safety and monitoring of PWR. The difficulties of a correct interpretation of noise signal in a power reactor encourage a deeper insight into the theoretical model. Following, this paper is dealing with 4 topics: • - theoretical model • - measurements made in PWR's, and evolution of power spectral densities, • - experimental test of models, • - future study in this range : methodology for early detection of failure and to indicate incipient failure. Using the expressions for linear system and for feedback loop, we obtain a simplified diagram for PWR with reactivity, temperature, velocity of fluid inputs and movement of internal structures. Neutron noise measurements are performed periodically on the “Centrale Nucléaire des Ardennes”. An investigation is also performed, in order to detect core barrel movements. The change of neutron noise at several power levels is shown, and used to check the model. The development of signal analysis and models for PWR is investigated in the last chapter.