Reactor Kinetics, Dynamic Response, and Neutron Noise in Molten Salt Reactors

Artikel i vetenskaplig tidskrift, 2011

The dynamic space- and frequency dependent response of a Molten Salt Reactor (MSR) to stationary perturbations is investigated in a simple analytical model. The Green's function of the system is investigated in the general case of arbitrary fuel recirculation velocity and in the limiting case of infinite fuel velocity which permits closed form solutions both in the static and dynamic case. It is found that the amplitude of the induced noise is generally higher and the domain of the point kinetic behaviour valid up to higher frequencies than in a corresponding traditional system. This is due to the differing behaviour of the delayed neutron precursors as compared to the traditional case. The MSR equations are not self-adjoint and the adjoint equation and adjoint function have to be constructed, which is also done here. Finally the space-dependent neutron noise, induced by propagating perturbations of the absorption cross section is calculated. A number of interesting properties that are relevant to full size MSRs are found and interpreted. The results are consistent with those in traditional systems but the domains of various behaviour regimes (point kinetic, space dependent etc.) are shifted to higher frequencies or system sizes.