A Space-Dependent Reactor-Noise Formulation Utilizing Modal Expansions

A space-dependent noise formulation is developed on the basis of the modal-analysis technique. Application of the method is illustrated by numerical calculations carried out for a one-dimensional model of a coupled-core Argonaut type reactor. It has been found that the suggested method may be readily used to calculate the auto- or cross-spectral-density functions of the neutron-level fluctuations for any of the group fluxes of a multienergy group calculation when the system is subjected to arbitrary stochastic input functions. Results obtained from the numerical calculations serve to illustrate the importance of the space dependence of the spectral functions and in particular the sensitivity of the cross-spectral-density function to the two points of observation.