Author: Alya Adel Mohamed Badawi
Publisher:
ISBN:
Category :
Languages : en
Pages : 302

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Author: Seungyon Cho
Publisher:
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Category :
Languages : en
Pages : 119

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ISBN:
Category :
Languages : en
Pages : 19

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A random network model has been utilized to analyze the problem of tritium percolation through porous Li ceramic breeders. Local transport in each pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the porous medium is accounted for via Monte Carlo methods. The model was then applied to an analysis of the relative contribution of diffusion and convective flow to tritium transport in porous lithium ceramics. 15 refs., 4 figs.

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Category :
Languages : en
Pages :

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Tritium retention and release data for lithium ceramics (Li2O, LiAlO2, and Li4SiO4) are available from in-reactor and post-irradiation anneal tests on single crystals, powders, and sintered products. With the exception of the single-crystal tests in which bulk diffusion is the rate-limiting release mechanism, it is very difficult to interpret the results of these tests and extrapolate the results to design conditions for a fusion solid-breeder blanket. Mathematical models are presented for various bulk, grain-boundary, and free-surface phenomena to aid in the interpretation and extrapolation of the data. 24 refs., 6 figs., 4 tabs.

Author: Hongjie Zhang
Publisher:
ISBN:
Category :
Languages : en
Pages : 178

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It is critical to be able to predict tritium transport in lead-lithium liquid metal (LM) blankets with great accuracy to provide information for fusion reactor safety and economy analyses. However, tritium transport processes are complex and affected by multiple physics such as magnetohydrodynamic (MHD) flow, yet there is no single computer code capable of simulating these phenomena inclusively. Thus the objectives of this research are: 1) to develop mathematical models and computational codes to quantify both tritium distributions throughout the blanket and the permeation loss rate from LM to helium coolant, and 2) to evaluate the key factors that govern tritium permeation and distribution. To accomplish these objectives, a computational framework for analyzing tritium transport phenomena affected by multi-physics and geometric features has been developed. Models have been proposed to integrate multiple tritium transfer processes, including transport inside the LM MHD flow, transfer across the material interface, and permeation through the structural materials and into the helium coolant. Numerical schemes have been developed and implemented in the code to link the different transport mechanisms. The developed model and code have been validated against the data from the US-JA TITAN experiments on hydrogen transport through an [alpha]-Fe/PbLi system and in-reactor tritium release data from lead-lithium, and the modeling results agree well with the experimental data. Parametric studies are performed to quantify the MHD effects, buoyancy effects, PES effects, and the uncertainties of transport properties. The MHD effects reduce the tritium permeation rate due to the higher velocity near the wall. However, the rate of decrease is reduced at higher Hartmann numbers. The buoyancy effect on tritium transport in the LM MHD flows is revealed. Its tritium inventory drops by 80%, and the permeation rate drops by 20% for an upward flow compared to a downward flow. If a PES is introduced on the wall parallel to the magnetic field, tritium loss rate increases by 15% because the velocity is reduced near the front wall. The range of permeation rate change on the basis of uncertainties of transport properties is also provided, and the effect of the uncertainty of tritium solubility is significant. Furthermore, as the FCI electric conductivity increases from 5 to 500 [omega]−1m−1, the tritium permeation rate decreases by 46% due to the increasing velocity in the gap. Lastly, the difference in tritium permeation rates between dual coolant lead lithium (DCLL) and helium-cooled lead lithium (HCLL) blanket concepts is quantified. The tritium permeation loss percentage from the HCLL concept is about one order of magnitude higher than from the DCLL concept (~ 17%. vs. 1.2%). This is mainly due to a much lower velocity and thus a much higher tritium partial pressure for the HCLL concept. The computational models and results stated in this work provide guidance on the lead-lithium liquid metal blanket designs to comply tritium control requirements with regard to the reduction in tritium permeation and inventory and on planning the experiments for database evaluation.

Author:
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Category : Dissertation abstracts
Languages : en
Pages : 704

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Category : Dissertations, Academic
Languages : en
Pages : 700

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Category :
Languages : en
Pages : 19

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Languages : en
Pages :

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Abstract: Attaining tritium self-sufficiency is an important mission for the Chinese Fusion Engineering Testing Reactor (CFETR) operating on a Deuterium-Tritium (D-T) fuel cycle. It is necessary to study the tritium breeding ratio (TBR) and breeding tritium inventory variation with operation time so as to provide an accurate data for dynamic modeling and analysis of the tritium fuel cycle. A water cooled ceramic breeder (WCCB) blanket is one candidate of blanket concepts for the CFETR. Based on the detailed 3D neutronics model of CFETR with the WCCB blanket, the time-dependent TBR and tritium surplus were evaluated by a coupling calculation of the Monte Carlo N-Particle Transport Code (MCNP) and the fusion activation code FISPACT-2007. The results indicated that the TBR and tritium surplus of the WCCB blanket were a function of operation time and fusion power due to the Li consumption in breeder and material activation. In addition, by comparison with the results calculated by using the 3D neutronics model and employing the transfer factor constant from 1D to 3D, it is noted that 1D analysis leads to an over-estimation for the time-dependent tritium breeding capability when fusion power is larger than 1000 MW.

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Category :
Languages : en
Pages : 21

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Among the major processes leading to tritium transport through Li ceramic breeders the percolation of gaseous tritium species through the connected porosity remains the lest amenable to a satisfactory treatment. The combination of diffusion and reaction through the convoluted transport pathways prescribed by the system of pores poses a formidable challenge. The key issue is to make the fundamental connection between the tortuousity of the medium with the transport processes in terms of only basic parameters that are amenable to fundamental understanding and experimental determinations. This fundamental challenges is met within the following approaches. The technique that we have employed is a random network percolation model. Local transport in each individual pore channel is described by a set of convection-diffusion-reaction equations. Long range transport is described by a matrix technique. The heterogeneous structure of the medium is accounted for via Monte Carlo methods. In this way the approach requires as inputs only physical-chemical parameters that are amenable to clear basic understanding and experimental determination. In the sense it provides predictive capability. The approach has been applied to an analysis of the concept of tritium residence time which is associated with the first passage time, a direct output of our analysis. In the next stage of our work the tool that we have developed would be employed to investigate the issues of vary large networks, realistic microstructural information and the effect of varying pressure gradient along the purge channels. We have demonstrated that the approach that has been adopted can be utilized to analyze in a very illuminating way the underlying issues of the concept of residence time. We believe that the present approach is ideally suited to tackle these very important yet difficult issues.