Multiple Reaction Correction to Neutron Reaction Cross Sections

The importance of the multiple reaction correction to cross sections above ∼0.1 MeV is demonstrated by deriving a simple formula for a thin-slab sample utilizing a limited multigroup, spatially averaged, transport theory, and applying the formalism to a few examples. To illustrate the immediate relevance of the correction, we also apply it to revise an important cross section in current use, (²³⁸U σ _nγ, ENDF/B-III). The correction can be large with thicker samples and at higher energies, especially for radiative capture (exceeding a factor of 10). Our examples indicate that multiple reaction effects must be checked in measuring or evaluating radiative capture, fission, reaction, and gamma production cross sections and their consequent spectra.