Uncertainty of reactor subcriticality determination obtained from sensors indication

Insensitivity of readings of neutron flux indicators to reactor subcriticality derived from the indefinite local perturbations of breeding is investigated in the context of simplest approximations (one- and two-dimensional reactor, one-group diffusion model of neutron transport). Having conservative character assumption on the possibility of compromise of such perturbations by coordinated adverse way is basic to the consideration. Using one-dimensional model the quantitative dependence derived from this error of registration of subcriticality from the determining system formed by geometric properties and material parameters of the reactor was determined. Using industrial uranium-graphite reactor it can be shown that the particular error may be significant in physically sizable reactors