Development of a neutron noise simulator for hexagonal geometries

The study of neutron flux fluctuations permits to detect anomalies during the operation of nuclear reactors. To effectively use this technique for nuclear reactor diagnostics, it is essential to accurately model the effects of the different types of anomalies on the neutron flux field. This paper deals with the development and validation of a neutron noise simulator for reactors with any kind of geometry, that is, rectangular and hexagonal geometries. The neutron noise can be obtained by a frequency-domain or a time-domain methodology. In this work we compare both methodologies in hexagonal reactors. The time-domain analysis solves the time-dependent neutron diffusion equation and then performs a Fourier analysis of the obtained time-dependent neutron fluxes and it is usually used as reference. On the other hand, the frequency-domain methodology solves the frequency-domain first-order neutron noise equation with complex values. To show the possibilities of the neutron noise simulator developed a generic absorbers of variable strength perturbation inside a three-dimensional hexagonal reactor is investigated. Both methodologies show similar numerical results.