Modified One-Group Model of Reactor Kinetics with Extended Field of Application

The modified one-group model of reactor kinetics is proposed in which the effective decay constant ofprecursor nuclei ofdelayed neutrons is a function ofperturbation in reactivity. It is shown that a cause of its variation is the transformation of spectra of delayed-neutron precursor nuclei. The algorithms for finding the mentioned function are described and approved. The variants of the obtained function approximation with different-degree polynomials are considered; the errors of finding the reverse period with these approximations are estimated. It is shown that even using the simple linear approximation allows the modified one-group model to be applied up to the prompt criticality with the reasonable error value in contrast to the one-group models with unchangeable decay constants of precursor nuclei. It is shown that using the modified one-group model of kinetics makes it possible to calculate the reactor period with the substantially higher accuracy than using the conventional formula, which extends significantly the area of its application.

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