Reactivity Determination with One Neutron Detector in a Transport-PWR Core

Abstract

Neutronics measurements are regularly conducted during operation in order to evaluate the physical characteristics of the core. A nonstandard reactimeter connected to a backup neutron detector is used to perform the measurements. A calculation of the reactivity on the basis of the indications of a single detector results in distortion of the true value of the reactivity because of spatial effects. A method of increasing the accuracy of the reactivity calculations by taking account of the changes in the efficiency of the ionization chamber is proposed. Software for performing the required calculations has been developed. The correctness of the proposed solution was checked and confirmed by experiments performed on a critical stand at OKBM Afrikantov using the core of an icebreaker reactor.