Theory of neutron multiplicity counting in an energy-dependent transport model

Paper in proceeding, 2024

To eliminate some of the restrictions of the point model of traditional multiplicity counting, in recent work we developed a general one-speed transport theory model for the calculation of the multiplicity moments, used in nuclear safeguards. At first only fission reactions were accounted for [1], [2], and later elastic scattering was added by neglecting the energy loss of neutrons when scattering on heavy nuclei [3]. To account for the energy loss of neutrons in elastic scattering on light nuclei, as well as inelastic scattering on heavy nuclei, the theory has to be extended to include energy dependence. This paper describes the full theory of the extension of the transport model to account for the energy dependence of the transport process. Explicit analytical expressions are given for both the elastic and inelastic scattering functions. Hence, combined with cross section data, the formulae are complete for concrete calculations. The application of the model for the cases of items containing several isotopes is also touched upon.