Investigation of the space-dependent noise induced by propagating perturbations

The space-dependent behaviour of the neutron noise, induced by perturbations represented by the fluctuations of the absorption cross sections, propagating with the coolant of a PWR, is investigated in a one-dimensional one-group approach. The general space-frequency dependent problem is solved for this specific noise source with the help of the Green's function technique. All calculations are made in the frame of first-order perturbation theory. The solution is investigated for different frequencies and system sizes. The limits of point kinetic and space-dependent behaviour were investigated. An interesting interference phenomenon was found between the point kinetic and the pure space dependent components of the noise for certain domains of the frequency and system size. The results bear some significance for the dynamics of Molten Salt Reactors (MSR), which is reported on in a companion paper.