MCNPX Monte Carlo simulations of particle transport in SiC semiconductor detectors of fast neutrons

Concrete has been used as a shield against high-energy photons (gamma) and neutrons since the beginning of use of nuclear reaction in energy, medicine and research. State of knowledge in shielding concrete technology is that while in case of protection against gamma radiation an increase in density caused by change of aggregate type for heavy-weight one is usually an efficient solution, the protection against neutrons is more complex. It is due to the differences in interactions of neutrons with the matter, depending on their kinetic energy and cross-sections for different reactions of the component atoms of the cement paste and the aggregate. The paper presents the results of the project NGS-Concrete - New-Generation Shielding Concrete. The aim is to design the composition of concrete against ionizing radiation, achieved by the use of experiment based on multi-criteria optimization of materials supported by the Monte Carlo simulations. Better concrete is the one that absorbs more thermal neutrons and slows down more fast neutrons at the same time. In the paper both results of Monte Carlo simulations and experimental studies on ordinary and heavyweight concrete containing epoxy polymer additive are presented. Close values of thermal neutron attenuation coefficients proved good accordance between simulation and experiment. The final conclusion is that epoxy resin is an efficient additive for neutron shielding concretes improving its ability to protect mainly against low energy neutrons. In experimental measurement there has not been observed an improvement of fast neutron attenuation due to increase of hydrogen atom content introduced with epoxy.

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Low-voltage EDS of magnesium ferrite Dendrites in a FEG-SEM

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100164854 ◽

1996 ◽

Vol 54 ◽

pp. 478-479

Author(s):

Matthew T. Johnson ◽

Ian M. Anderson ◽

Jim Bentley ◽

C. Barry Carter

Keyword(s):

Monte Carlo ◽

Quantitative Analysis ◽

Monte Carlo Simulations ◽

Cross Section ◽

Spatial Resolution ◽

Low Voltage ◽

Magnesium Ferrite ◽

X Ray ◽

Interaction Volume ◽

Ferrite Spinel

Energy-dispersive X-ray spectrometry (EDS) performed at low (≤ 5 kV) accelerating voltages in the SEM has the potential for providing quantitative microanalytical information with a spatial resolution of ∼100 nm. In the present work, EDS analyses were performed on magnesium ferrite spinel [(MgxFe1−x)Fe2O4] dendrites embedded in a MgO matrix, as shown in Fig. 1. spatial resolution of X-ray microanalysis at conventional accelerating voltages is insufficient for the quantitative analysis of these dendrites, which have widths of the order of a few hundred nanometers, without deconvolution of contributions from the MgO matrix. However, Monte Carlo simulations indicate that the interaction volume for MgFe2O4 is ∼150 nm at 3 kV accelerating voltage and therefore sufficient to analyze the dendrites without matrix contributions.Single-crystal {001}-oriented MgO was reacted with hematite (Fe2O3) powder for 6 h at 1450°C in air and furnace cooled. The specimen was then cleaved to expose a clean cross-section suitable for microanalysis.

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