Comparison of oxidation model predictions with gasification data of IG-110, IG-430 and NBG-25 nuclear graphite |
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| Authors: | Mohamed S El-Genk Jean-Michel P Tournier |
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| Affiliation: | 1. Institute for Space & Nuclear Power Studies, University of New Mexico, Albuquerque, NM 87131, USA;2. Chemical & Nuclear Engineering Dept., University of New Mexico, Albuquerque, NM 87131, USA;3. Mechanical Engineering Dept., University of New Mexico, Albuquerque, NM 87131, USA;1. Department of Materials Science and Engineering, Boise State University, 1910 University Drive, Boise, ID 83725, United States;2. Center for Advanced Energy Studies, 995 University Blvd, Idaho Falls, ID 83415, United States;3. Idaho National Laboratory, 2351 N. Boulevard, Idaho Falls, ID 83415, United States;1. Materials Performance Centre, Corrosion and Protection Centre, School of Materials, The University of Manchester, Manchester M13 9PL, UK;2. Nuclear Graphite Research Group., School of Mechanical, Aerospace and Civil Engineering, The University of Manchester, Manchester M13 9PL, UK;3. Department of Materials, University of Oxford, Parks Road, Oxford OX1 3PH, UK;1. National Nuclear Laboratory, 102 B Stonehouse Business Park, Sperry Way, Stonehouse, Gloucestershire, GL10 3UT, UK;2. National Nuclear Laboratory, Central Laboratory, Sellafield, Seascale, Cumbria, CA20 1PG, UK;3. Nuclear Research and Consultancy Group, Westerduinweg 3, 1755 LE Petten, The Netherlands;4. EDF Energy Nuclear Generation Ltd., Barnett Way, Barnwood, Gloucester, GL4 3RS, UK;1. Beijing Key Lab of Fine Ceramics, Institute of Nuclear and New Energy Technology, Tsinghua University, Beijing 100084, China;2. State Key Lab of New Ceramic and Fine Processing, Tsinghua University, Beijing 100084, China;3. Advanced Material Laboratory, School of Materials Science & Engineering, Tsinghua University, Beijing 100084, China |
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| Abstract: | A phenomenological oxidation kinetics model of graphite is presented and its results are compared with the reported experimental gasification data for nuclear graphite of IG-110, IG-430 and NBG-25. The model uses four elementary chemical kinetics reactions, employs Gaussian-like distributions of the specific activation energies for adsorption of oxygen and desorption of CO gas, and accounts for the changes in the effective surface areas of free active sites and stable oxide complexes with weight loss. The distributions of the specific activation energies for adsorption and desorption, the values of the pre-exponential rate coefficients for the four elementary chemical reactions and the surface area of free active sites are obtained from the reported measurements using a multi-parameter optimization algorithm. At high temperatures, when gasification is diffusion limited, the model calculates the diffusion velocity of oxygen in the boundary layer using a semi-empirical correlation developed for air flows at Reynolds numbers ranging from 0.001 to 100. The model also accounts for the changes in the external surface area, the oxygen pressure in the bulk gas mixture and the effective diffusion coefficient in the boundary layer with weight loss. The model results of the total gasification rate and weight loss with time in the experiments agree well with the reported measurements for the three types of nuclear graphite investigated, at temperatures from 723 to 1226 K and weight loss fractions up to ～0.86. |
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