Particle size inhomogeneity effect on neutron resonance densitometry

Neutron Resonance Densitometry (NRD) represents a possible option to determine the heavy metal content in melted nuclear fuel. This method is based on the well-established methodology of neutron time-of-flight (TOF) transmission and capture measurements. In particular, NRD can measure both the isotopic and the elemental composition. It is a non-destructive method and is applicable for highly radioactive material. The details of this method are explained in another contribution to this bulletin. The accuracy of NRD depends among other factors on sample characteristics. Inhomogeneities such as density variations in powder samples can introduce a significant bias in the determination of the composition. In this contribution, the impact of the particle size distribution of such powder samples on results obtained with NRD is investigated. Various analytical models, describing the neutron transport through powder, are compared. Stochastic numerical simulations are used to select a specific model and to estimate the introduced model uncertainty. The results from these simulations will be verified by dedicated measurements at the TOF-facility GELINA of the EC-JRC-IRMM.JRC.D.4-Standards for Nuclear Safety, Security and Safeguard