Statistical control keff for subcritical fused-salt transplutonium burner reactor

In an at-power subcritical reactor with an external source, a deviation of criticality from a prescribed value monitored by means of the neutron flux may not be detected when the source characteristics change concurrently. In this connection, the fundamental possibility of additional real-time criticality control on the basis of reactor noise is being studied for a subcritical, fused-salt, transplutonium, burner reactor. A simple computational model of a reactor with a self-consistent description of the change in the neutron and thermophysical parameters, taking account of the circulation of the fuel salt through a heat-exchanger, is used. The theory of stationary random processes is used to examine the behavior of the model under a perturbation due to white-noise fluctuations of the reactivity and source intensity. It is shown that when the reactor operates at constant power the effect of the subcriticality on the noise level in the reactor is not a unique function of the ratio of the source and reactivity fluctuations. Ways to improve the representativeness of the reactor noise as a subcriticality indicator are briefly discussed.