Investigation of the space-dependent noise induced by propagating density fluctuations - 109

The space-dependent behavior of neutron noise induced by a propagating perturbation, represented by the fluctuations of the absorption cross section propagating with the coolant of a PWR, is investigated in a one-dimensional one-group approach. The general space-frequency problem is solved for this specific noise source with the help of Greens function technique. All calculations are made in the frame of first-order perturbation theory. The solution is investigated for a 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 combinations of the frequency and system size. The results bear a significance for the dynamics of Molten Salt Reactors (MSR), which will be reported on in a companion paper. (authors)