A void fraction evaluation scheme with nonstandard reflective conditions

Abstract In this article, we describe a discrete ordinates model and a two-step numerical scheme for the inverse problem of evaluating the void fraction of a reflected slab from the responses of a collimated detector in a typical source–detector configuration for backscattered neutrons. For this purpose, we develop a two-layer model for the transport of neutrons through a slab–reflector medium, and we derive nonstandard discrete ordinates reflective conditions for neutrons at the slab–reflector interface. These reflective conditions are the key to the second step of our void fraction evaluation scheme. In order to illustrate the numerical consistency and the low sensitivity of our two-step scheme to experimental inaccuracies in the detector responses, we perform a number of computational void fraction evaluation experiments with a sample slab–reflector medium. Keywords: Void fraction evaluationSourcedetector techniqueReflected slabNeutron transportDiscrete ordinatesSpectral nodal method Acknowledgements The author is gratefully acknowledged to three anonymous referees for their valuable suggestions, constructive criticism, and scientific encouragement.