A New Experimental Correction Method for the First-Order Perturbation Approximation in the Steady Subcritical Reactor

Abstract

In the subcritical nuclear reactor, the subcriticality is closely related with the neutron flux distribution. Since the relationship between them is complex, the subcriticality measurement by conventional methods involves some difficulties, particularly when the subcriticality is large. A new subcriticality measurement method is proposed for the steady subcritical state. By this method, the relative distribution of the change in neutron flux between before and after the perturbation is numerically calculated. On the other hand, the amplitude of the perturbation is estimated from the count rates of neutron detectors. By this combination of the calculation and experiment, the subcriticality can be accurately estimated, to the extent that the perturbation is qualitatively known beforehand. One of the advantages of this method over the conventional modified neutron source multiplication method is that numerical calculations are only executed on unperturbed states. In addition, the completeness of the eigenfunctions is not assumed. The validity of this method is confirmed through the numerical calculation.