Noise Lag Effect in Transients of a Subcritical Molten Salt Transplutonium Incinerator

Abstract

In connection with its subcritical operating regime, the molten salt reactor now under development for incinerating transplutonium elements could require additional monitoring of k eff based on reactor noise. The lag in the response of transient processes to reactor noise, which is fundamental for routine monitoring of criticality, is studied. A simple computational model of a reactor with a mutually consistent description of the neutron and thermal physical parameters, which takes account of fuel salt circulation, is used. It is shown for a fast transient process with strong variation of the criticality that in the model chosen the noise dispersion as its probabilistic characteristic is an instantaneous indicator of the running value of the subcriticality. This property of the noise is determined by the fact that it is predominately affected by the high-frequency component of the perturbation of the reactor. It is noted that a certain time will be required to determine a change in the noise, and this will probably determine the time lag in subcriticality monitoring.