A Segmented Gamma Scanner for the Verification of LEU Oxide Powders

The verification of the amount of U oxide powder and the 235U/U abundance in typical fuel fabrication plant containers is described. Only gamma spectroscopy and direct calibration with standards are used. The measurements are performed scanning the container axis with a collimated detector. The spectrum energy considered covers the 1001 keV region to estimate the 238U mass and the 185.7 keV region to determine the 235U/U abundance. The gamma spectra taken at different axial positions of the container verify the homogeneity level of the sample.JRC.G.8-Nuclear safeguard

Characterisation of 3HE Proportional Counters

This paper describes the characterisation of a set of 3He proportional counters differing in gas composition and pressure. Each step of the signal generation in the detector is analysed. Optimal working conditions are defined in order to choose the high voltage to be applied. Dead time with short shaping time is measured in such optimal conditions. In addition the overall neutron efficiency and the gamma sensitivity are reported. Such characterisation is required for a correct choice of the associated counting electronics and the applications of the counters. A complete pulse processing modular system, consisting of a pulse height analysis system and a pulse correlation analysis system equipped with a time of arrival recorder, is used for the characterisation.JRC.G.8-Nuclear safeguard

Modelling of the Programming Window Distribution in Multi Nanocrystals Memories

In this paper, the impact of the Si nanocrystals technological fluctuations on the programming window dispersion of multi nanocrystals memory is thoroughly investigated. Technological dispersions of different nanocrystals populations, directly measured by high-resolution transmission electron microscopy, are used as starting points for the modeling of the device characteristics. Numerical Monte Carlo simulations as well as an original compact modeling, based on the compound distributions (CD) statistics, are here presented. Exact analytical results (CD model), approximated analytical results (CD+Central Limit Theorem model) and numerical results (numerical convolution) are deeply discussed. Finally, the good agreement between our simulations and experimental data of ultrascaled nanocrystal devices, made by conventional UV lithography or by e-beam lithography, definitively confirms the validity of our theoretical approach