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The first portion of this work is a comprehensive analysis of the chemical environment in a High Temperature Gas-Cooled Reactor TRISO fuel particle. Fission product inventory versus burnup is calculated. Based on those results a thermodynamic analysis is performed to determine fission product vapor pressures, oxygen partial pressure, and carbon monoxide and carbon dioxide gas pressures within the fuel particle. Using the insight gained from the chemical analysis, a chemical failure model is incorporated into the MIT fuel performance code, TIMCOAT. Palladium penetration of the SiC layer is added to the fracture mechanics failure model. Rare-earth fission product and palladium corrosion of the SiC layer are additionally modeled. The amoeba effect is added as a new failure mode. The palladium penetration model has the most significant result on the overall fuel performance model and increases the number of predicted particle failures. The thinning of the SiC layer due to fission product corrosion has a slight effect on the overall fuel performance model. Finally, the amoeba effect model does not lead to any particle failures, but adds to the completeness of the overall model.
(cont.) It is concluded that accurate modeling of TRISO particles depends on having very high accuracy data describing material properties and a very good understanding of the uncertainties in those measurements.
The success of gas reactors depends upon the safety and quality of the coated particle fuel. The understanding and evaluation of this fuel requires development of an integrated mechanistic fuel performance model that fully describes the mechanical and physico-chemical behavior of the fuel particle under irradiation. Such a model, called PARFUME (PARticle Fuel ModEl), is being developed at the Idaho National Engineering and Environmental Laboratory. PARFUME is based on multi-dimensional finite element modeling of TRISO-coated gas reactor fuel. The goal is to represent all potential failure mechanisms and to incorporate the statistical nature of the fuel. The model is currently focused on carbide, oxide nd oxycarbide uranium fuel kernels, while the coating layers are the classical IPyC/SiC/OPyC. This paper reviews the current status of the mechanical aspects of the model and presents results of calculations for irradiations from the New Production Modular High Temperature Gas Reactor program.
This publication reports on the results of a coordinated research project on advances in high temperature gas cooled reactor (HTGR) fuel technology and describes the findings of research activities on coated particle developments. These comprise two specific benchmark exercises with the application of HTGR fuel performance and fission product release codes, which helped compare the quality and validity of the computer models against experimental data. The project participants also examined techniques for fuel characterization and advanced quality assessment/quality control. The key exercise included a round-robin experimental study on the measurements of fuel kernel and particle coating properties of recent Korean, South African and US coated particle productions applying the respective qualification measures of each participating Member State. The summary report documents the results and conclusions achieved by the project and underlines the added value to contemporary knowledge on HTGR fuel.
The performance of coated fuel particles is essential for the development and deployment of High Temperature Gas Reactor (HTGR) systems for future power generation. Fuel performance modeling is indispensable for understanding the physical behavior of fuel particles and achieving their high reliability during operations and accidents through a guided design process. This thesis develops an integrated fuel performance model of coated particle fuel to comprehensively study its mechanical behavior and define an optimum fuel design strategy with the aid of the model. Key contributions of the thesis include a pyrocarbon layer crack induced particle failure model with a fracture mechanics approach, mechanical analysis of particles with better representation of irradiation induced creep, a proposed fuel optimization procedure, the capability to simulate arbitrary irradiation histories, and the incorporation of Monte Carlo sampling to account for the statistical variation of particle properties.
Storage and Hybridization of Nuclear Energy: Techno-economic Integration of Renewable and Nuclear Energy provides a unique analysis of the storage and hybridization of nuclear and renewable energy. Editor Bindra and his team of expert contributors present various global methodologies to obtain the techno-economic feasibility of the integration of storage or hybrid cycles in nuclear power plants. Aimed at those studying, researching and working in the nuclear engineering field, this book offers nuclear reactor technology vendors, nuclear utilities workers and regulatory commissioners a very unique resource on how to access reliable, flexible and clean energy from variable-generation. Presents a unique view on the technologies and systems available to integrate renewables and nuclear energy Provides insights into the different methodologies and technologies currently available for the storage of energy Includes case studies from well-known experts working on specific integration concepts around the world
The research project was related to the Advanced Fuel Cycle Initiative and was in direct alignment with advancing knowledge in the area of Nuclear Fuel Development related to the use of TRISO fuels for high-temperature reactors. The importance of properly coating nuclear fuel pellets received a renewed interest for the safe production of nuclear power to help meet the energy requirements of the United States. High-temperature gas-cooled nuclear reactors use fuel in the form of coated uranium particles, and it is the coating process that was of importance to this project. The coating process requires four coating layers to retain radioactive fission products from escaping into the environment. The first layer consists of porous carbon and serves as a buffer layer to attenuate the fission and accommodate the fuel kernel swelling. The second (inner) layer is of pyrocarbon and provides protection from fission products and supports the third layer, which is silicon carbide. The final (outer) layer is also pyrocarbon and provides a bonding surface and protective barrier for the entire pellet. The coating procedures for the silicon carbide and the outer pyrocarbon layers require knowledge of the detailed kinetics of the reaction processes in the gas phase and at the surfaces where the particles interact with the reactor walls. The intent of this project was to acquire detailed information on the reaction kinetics for the chemical vapor deposition (CVD) of carbon and silicon carbine on uranium fuel pellets, including the location of transition state structures, evaluation of the associated activation energies, and the use of these activation energies in the prediction of reaction rate constants. After the detailed reaction kinetics were determined, the reactions were implemented and tested in a computational fluid dynamics model, MFIX. The intention was to find a reduced mechanism set to reduce the computational time for a simulation, while still providing accurate results. Furthermore, fast chemistry techniques would be coupled to MFIX to effectively treat the complex chemistry thus improve the computational efforts. Based on the reaction kinetics modeling, it was determined that the detailed set of chemical reactions for the thermal decomposition of a methyltrichlorosilane (MTS)/H2 mixture consisted of 45 species and 114 gas-phase reactions. Further work identified a mechanism consisting of approximately 60 surface reactions for the surface chemistry of SiC chemical vapor deposition. A reduced mechanism for the MTS gas-phase pyrolysis was constructed using the scanning method based on optimization concepts, which consisted of only 28 species and 29 reactions. The benefits of this project are that we have determined gas-phase species produced during and after the various decomposition reactions of MTS. The success of the computational approaches can now be used to predict the complex chemistry associated with the CVD process in producing nuclear fuel. It is expected that the knowledge we acquired can be easily transferred and that it will contribute to further experimental investigations. Furthermore, the computational techniques can now be used for reactor design and optimization for the next generation of nuclear reactors.