26,018 research outputs found

    A Study of Vitrified Nuclear Wasteforms by Molecular Dynamics, Electron Microscopy and Raman Spectroscopy

    Get PDF
    In this study an attempt is made to create molecular dynamics (MD) models of borate glass, alkali borosilicate glasses, and UK vitreous High Level Radioactive Wasteforms. The study also includes experimental studies of vitrified wasteforms by helium pycnometry, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), X-ray florescence spectroscopy (XRF) and Raman spectroscopy. Molecular dynamics models of alkali borosilicate glasses were created using Buckingham and BHM potentials in the constant pressure and temperature ensemble. The models using BHM potentials showed more realistic boron coordination numbers than those using Buckingham potentials. However structural features such as Si-O, Li-O and Na-O nearest neighbour distances and O Si O and O B O bond angles were considered satisfactory using Buckingham potentials. SEM images showing phase separation in four different vitrified wasteforms are presented. The chemical composition of the phases were determined using SEM EDX. XRF spectroscopy was obtained from the wasteforms in powder form and show qualitative agreement with nominal compositions. Raman spectroscopy also revealed the presence of MoO4 tetrahedra in a glass environment and in phases such as CaMoO4 and Na(Gd,Nd)(MoO4)2. The presence of ruthenium, cerium and zirconium phases were also found in the Raman spectra of wasteforms. MD models of three simplified vitrified wasteforms were created using Buckingham potentials. Two models of each wasteform were created. The first models used only two-body potentials and showed MoO6 octahedra connected to borosilicate network formers. In the second model of each wasteform, an additional O Mo O three-body potential was applied. The results of the second models showed MoO4 tetrahedra detached from the borosilicate network which is a realistic feature in comparison to the experimental observations

    Investigation of flow and heat transfer in a large-scale spent nuclear fuel cooling pond

    Get PDF
    The recent focus on nuclear power has led to the need for more efficient and economical methods of operating the Spent Nuclear Fuel (SNF) cooling ponds as well as complying with the strict safety and environmental legislations imposed by the IAEA and the UK Government. Like many other industrial applications, the design and operation of the SNF cooling ponds have evolved from experience; trial and error. Since the stored materials in such ponds are radioactive, it is very difficult to perform experimental studies. As a result, a rigorous scientific study based on fundamental principles has to be performed. The present research explores analytically and numerically the main processes that take place across the pond installation. The body of the present study includes four main parts: the first part is involved in modelling the heat loss from the free water surface, mainly due to evaporation, using analytical and single-phase numerical approaches, which represents a critical factor in the modelling of the large-scale cooling ponds. The predicted results were in good agreement with experimental data available in open literature. In the second part, a thermal model using Microsoft Excel spreadsheet was developed for the cooling pond based on an analytical approach. The well-mixed hypothesis was adopted to describe the water zone as well as the humid air zone. Also, the ventilation system was considered within this model. The developed spreadsheet tool was validated against reliable data available for Maine Yankee pool as well as temperature measurements collected from the Sellafield site. This spreadsheet tool is able to describe the transient behaviour with low computational cost, allowing many "what-if" scenarios to be rapidly investigated. In the third part, Computational Fluid Dynamics (CFD) was used to model the cooling pond at both macro and micro levels. The macro level modelling involved in developing a CFD model for Sellafield’s cooling pond where the fuel regions were approximated to porous medium. The computational domain was produced for the water zone only, where the humid air zone was introduced to the model by coupling of the spreadsheet model with the CFD model. This model was validated and used to examine the distribution of water temperature to confirm the reliability of the adopted well-mixed approach in the analytical model. The outcomes from the CFD and spreadsheet models were used to provide some boundary conditions to the micro-level model of the fuel assemblies. The modelling methodology of the fuel assemblies was partially validated with experimental data for heat transfer around vertical cylinder. The maximum temperature of the water within the rack arrangement was determined under various conditions and a correlation was proposed. Finally, a sensitivity study was performed using Taguchi method and the statistical method of ANOVA to assess the influence of the cooling systems as well as the environmental conditions on the thermal performance of the cooling pond. The spreadsheet model was implemented to carry out the calculations. The outcomes from this study were presented in the form of recommendations that may be able to aid the organisation to manage their cooling pond more efficiently and safely during the normal operating conditions as well as recovery from an accident scenario

    Comparative Analysis of Mobile 3D Scanning Technologies for Design, Manufacture of Interior and Exterior Tensile Material Structures and Canvasman Ltd. Case Study

    Get PDF
    This report aimed to investigate mobile 3D Scanning technologies to improve the 3D data capture and efficiency into Canvasman’s CAD design and manufacturing processes with focus on accurate resolution. The Santander funded Collaborative Venture Fund (CVF) project has provided research, survey data, evaluation and analysis for Canvasman Ltd. on 3D portable scanning hardware and software. The project solutions recommended in this report offers impartial product information on the current appropriate 3D scanning technology that potentially could improve efficiency of data capturing, design and manufacture of interior and exterior spaces, boats, vehicles and other similar constructions for creating and installing flexible coverings and indoor and outdoor structures

    Mardeck Ltd. Munchies

    Get PDF
    Bar & grill. Creative menu design. 3-D design. Small cereal box. First Place Winner for National Restaurant Association menu design contest. Geographical location: Rockville, Maryland
    • …
    corecore