The measurement of the resonance absorption of neutrons in an atomic power station reactor

Abstract

One of the most important quantities determining the possibility of the development of a nuclear chain reaction in the system uranium-moderator is 1-ϕ — the probability of the resonance absorption of neutrons by U238 in the process of their slowing down from the fission to thermal energies. Up to the present time the calculation of 1-ϕ for heterogeneous reactors is not sufficiently accurate; there arises, in this connection, the necessity for an experimental determination of 1-ϕ directly in the reactor lattice. In this paper the experimental methods for the determination of the resonance absorption are discussed. Various corrections are considered, taking into account the neutron loss, the fission of the uranium and the neutron capture in the resonance region. For an atomic power station reactor employing enriched uranium (5% U235) these corrections are found to be significant. Three methods are used to calculate ϕ — the resonance escape probability — for an atomic power station reactor. ϕ was found to be equal to 0.900±0.015.