RESUMO
The fast neutrons generated by Deuterium-Tritium (DT) fusion reaction have been widely applied in prompt gamma ray neutron activation analysis measurements. In this study, a multi-layer neutron collimator for DT neutron generator was developed. Genetic algorithm combined with Monte Carlo simulation was used to design a collimator made of iron, lead, graphite, and borated polyethene. Copper foil activations were conducted to determine the fast neutron flux ratios between the beam port and its nearby area and agreed well with those predicted by the simulations. The results demonstrated that a narrower beam was obtained. The fast neutron beam flux was 568 ± 14 s-1 cm-2. The neutron flux ratio of the collimator was improved by a factor of 2.36, which could provide a better neutron beam.
Assuntos
Nêutrons Rápidos , Nêutrons , Trítio , Método de Monte Carlo , AlgoritmosRESUMO
An inelastic neutron scattering facility consisting of a DT neutron generator and a HPGe detector was used for metallic material analysis. The facility model was optimized based on Monte Carlo simulations. Performance of modified facility was tested through various metallic elements measurements. The results showed that the mass detection limits (MDL) of different elements were improved after optimization. Quantitative analyses of Fe and Cr in stainless steel sample were then conducted to evaluate the performance of alloy measurement. Calibration curves were obtained through measuring the reference samples. The contents of Fe and Cr in an unknown sample were determined by the calibration curves and the results were in good agreement with those obtained by X-ray fluorescence method.
RESUMO
Phytoremediation using economically valuable, large biomass, non-edible plants is a promising method for metal-contaminated soils. This study investigated cotton's tolerance for Cd and remediation potential through analyzing Cd bioaccumulation and localization in plant organs under different soil Cd levels. Results showed cotton presents good tolerance when soil Cd concentration ≤20.26 mg kg(-1). Cotton had good Cd accumulation ability under low soil Cd levels (<1.26 mg kg(-1)), with a TF value (the ratio of Cd concentration in stem to root) above 1. Energy dispersive X-ray microanalysis indicated cotton leaf transpiration played a key role in extracting soil Cd, while roots and stems were the main compartments of Cd storage. Cd complexation to other organic constituents in root and stem cell sap could be a primary detoxifying strategy. Therefore, cotton is a potential candidate for phytoremediation of Cd-contaminated soils.
