Chapter 2 - Neutron Interactions

Abstract

This chapter details the fundamentals of neutron interactions in nuclear reactions. At the core of neutron interactions is the concept of the cross section or the cross-sectional area of a nucleus as it appears to an incoming neutron. Such cross sections, their dependence on the neutron's kinetic energy, and the relative probabilities that a collision will result in scattering, capture, or fission form the basic physical data upon which the properties of chain reactions rest. The chapter starts with a discussion on the neutrons' behavior as they travel through space and defines microscopic and macroscopic cross sections. It then details the differences between cross sections for scattering, absorption, and other reaction types. The chapter explores the range of kinetic energies over which neutrons may exist in a reactor, and then details the dependence of cross section on neutron energy. Concepts of microscopic and macroscopic cross sections, neutron energy range, and cross section energy dependence are explained in detail. The chapter concludes with describing the distributions of energies of scattered neutrons.