SPN Neutron Noise Calculations

Abstract

[EN] Nowadays, non-invasive detection of anomalies in nuclear power plants is possible through neutron noise monitoring. The early detection of such anomalies gives the possibility to take proper actions before they lead to safety concerns or impact on the plant availability. In this context, neutron noise is studied to analyse the effects of small perturbations in nuclear reactors that are generally produced by stochastic fluctuations of the coolant properties, such as its density or temperature, and mechanical vibration of fuel elements, controls rods and other structures in the reactor. Normally, these fluctuations are expressed as perturbations in the cross-sections of the materials of the reactor. This makes necessary to develop accurate simulations of the neutron noise against cross sections pertubations. In this work, a full formulation of the neutron noise multigroup SPN equations in the frequencydomain is developed. This formulation differs from the classical diffusive formulations because it keeps all the terms of the time derivatives of the neutron flux.