The Derivation and Proper Use of Stewart’s Formula for Thermal Neutron Self-Shielding in Scattering Media

The derivation and proper use of a formula originally published in 1959 for thermal neutron self-shielding computations in scattering bodies are presented. It is shown that the f₀ entity in this formula must be computed using the total macroscopic cross section _∑t instead of the macroscopic absorption cross section _∑a, as was stated in previous publications. The validity of the formula is verified by Monte Carlo computations.