核能級石墨(Nuclear-grade graphite)因具有良好的物理性質，使之被選做為超高溫氣冷式反應器(Very High Temperature Reactor)中的爐心與結構材料。然而若發生熱氣管道(Hot Gas Duct)破裂，發生空氣進氣事故時，則會使得石墨部件嚴重的被氧化。在本篇論文之前，已有非常多的研究學者致力於研究核能級石墨在700-1100℃的氧化機制。而查閱文獻後發現，幾乎沒有相關的文獻有對大於1100℃以上的石墨氧化實驗機制做解釋，所以本實驗選用石油基焦炭製程的IG-110與瀝青焦炭基製程的NBG-18兩者相互做比較，樣品直徑為1公分、高度為1.5公分，將石墨樣品置入高溫爐中，使樣品處於700-1600℃下的高溫，並通以流量2L/min的乾空氣，以模擬核能級石墨樣品在VHTR發生進氣事故時的高溫氧化效應。藉由紀錄在不同溫度下石墨樣品氧化速率、使用SEM觀察表面及橫截面，最後，也進一步利用Arrhenius plot 之斜率，計算石墨在不同溫度區間發生氧化反應的活化能，來推斷在不同溫度下它的氧化機制等物理現象。
本實驗在氧化速率結果方面，發現石墨在超高溫度氧化的趨勢並不像以往文獻預測的在第三區(~1100℃)後，氧化速率就達到飽和，氧化速率幾乎不再隨著溫度有顯著變化，而是當氧化溫度高於1200℃後，氧化速率再次隨著溫度急遽上升，直到氧化溫度至1600℃時，氧化速率才再度趨緩。而從石墨表面微結構的觀察可以發現到，在1200℃以前，由於黏著劑氧化的較填充物快，氧化後的樣品表面可以清楚的觀察到填充物的顯現，而在1200℃後，表面填充物有明顯的破壞，推測在此溫度範圍下，填充物也開始無法承受高溫，產生劇烈的氧化，填充物的氧化造成進一步粗糙度的增加，增加反應面積，使氧化速率持續上升，而到最後1600℃時，當空氣遇到石墨表面，不管是填充物還是黏著劑皆會快速氧化，氧化速率只與提供空氣的量有關，所以表面差異氧化的現象變的不明顯，粗糙度降低。最後，由 Arrhenius Plot 計算斜率，活化能並不像過往文獻所預測的在第三區趨近於零，而是在1200℃再度上升，活化能的上升可能是由於氧化機制的改變，機制轉變成大部分為填充物氧化的形式，使得活化能再度上升。由以上幾點推估，對IG-110與NBG-18兩種核能級石墨來說，在氧化溫度大於1200℃後，氧化速率再次的上升的現象之氧化機制是與以往第三區的氧化機制不同的，而這些現象在氧化溫度到達最高溫度1600℃時變的不明顯，這代表材料氧化測試溫度到達1600℃時，為材料的極限，填充物和黏著劑幾乎沒有分別了。

In previous studies, the oxidation reaction of nuclear graphite could be divided into three regimes and the increase of oxidation rate subjected to heating was up to Regime III (about 1000-1200°C).However; our study finds that the oxidation rate increases again above 1200°C.This phenomenon has not been reported by other authors up to now. Therefore, we focus on the oxidation behavior of nuclear graphite oxidized at very high temperature range (700-1600°C).
Petroleum-based coke IG-110 and pitch-based coke NBG-18 are the materials selected in this study. The sample size is 10 mm diameter x 15 mm height. The 3-zone furnace and mass flow controller were used to oxidize these samples under 700 to 1600°C and 2L/min dry air. The weight loss of these specimens were measured and they were characterized by Scanning Electron Microscope (SEM). As we know, the nuclear graphite was composed of filler and binder. Due to higher activation energy and greater crystallinity, filler oxidized slower than binder. From SEM cross section images result showed that the surface roughness increased with temperatures. The increasing roughness implied more exposed area that can react with air which led the oxidation rate to increase again above 1200°C. And, this increasing trend terminated when the testing temperature finally reached 1600°C.
In view of this, we finally concluded that the oxidation rate would increase again above 1200°C because of different oxidation behavior of filler and binder on the surface. In other words, the oxidation mechanism above 1200°C was different from the oxidation reaction between 1000°C to 1200°C.

[1] 郭博堯(2002): 全球化石能源危機時代與我國所面臨挑戰。國政研究報告。財團法人國家政策研究基金會。
[2] Oil & Gas Journal, World Oil, 2013.
[3] Working Group I: The Scientific Basis, Climate Change 2001, Intergovernmental Panel on Climate Change (IPCC) Third Assessment Report.
[4] Sarah T. Gille, “Warming of the Southern Ocean Since 1950s”, Science, 295, pp.1275-1277, 2002
[5] Article 2: Objective, Framework Convention on Climate Change, United Nations.
[6] IEA/OECD Key World Energy Statistics, 2013.
[7] 台灣電力公司 102年年報。
[8] http://www.taipower.com.tw/content/new_info/new_info-b26.aspx?LinkID=7
[9] A Technology Roadmap for Generation IV Nuclear Energy System, U.S. DOE Nuclear Energy Research Advisory Committee and the Generation IV International Forum, pp.5-6, 2012.
[10] 蔡富豐(2012):日本311福島核災事件週年省思與感言。台電核能月刊，Volume 351，pp.16-42，民國101年3月。
[11] John R. Lamarsh, Anthony J. Barrata, Introduction to Nuclear Engineering 3rd edition, Patience Hall.
[12] 楊福家，原子物理學，高等教育出版社.
[13]http://www.dongyaboke.com/library2000shtml30276102169616.html
[14] 李敏，科學月刊，第42卷第2期.
[15] http://www.jtis.org/project1/ch41.htm
[16] https://www.gen-4.org/gif/jcms/c_9260/public
[17] R&D Outlook for Generation IV Nuclear Energy System, Gen IV International Forum, Aug, 2009.
[18] A Technology Roadmap for Generation IV Nuclear Energy System, US DOE Nuclear Energy Research Advisory Committee, GIF-002-00, 2002.
[19] Fuel and Graphite Needs for VHTR, David Petti, W. Windes, NGNP.
[20] Reactor Physics Parametric and Depletion Studies in Support of TRISO Particle Fuel Specification for the Next Generation Nuclear Plant, James W. Sterbentz, Bren Phillips, Robert L. Sant, Gray S. Chang, Paul D. Bayless, INEEL/EXT-04-02331, Sep. 2004.
[21] VHTR System Research Plan, Gen IV international forum, Mar. 2006.
[22] Japan Atomic Energy Agency Oarai Research & Development Center http://httr.jaea.go.jp/eng/index.html
[23] Kazuhiko Kunitomi, Xing Yan, Tetsuo Nishihara, Nariaki Sakaba, Tomoaki Mouri, “JAEA’s VHTR for Hydrogen and Electricity Cogeneration: GTHTR300C”, Nuclear Engineering and Technology, Volume 39, Feb. 2007.
[24] Development History of the Gas Turbine Modular High Temperature Reactor, H.L. Brey, IAEA,
[25] http://www.sellafieldsites.com/solution/risk-hazard-reduction/windscale/
[26] Juliana P. Duarte, José de Jesús Rivero Oliva, Paulo Fernando F. Frutuoso e Melo, Generation IV Nuclear Systems: State of the Art and Current Trends with Emphasis on Safety and Security Features, Current Research in Nuclear Reactor Technology in Brazil and Worldwide, 2013.
[27] 盧銀娟,楊宇,石俠民, “球床模塊式高溫氣冷堆的研究及發展現狀” , 核電站, 第11期, p.1-7, 2002.
[28] http://httr.jaea.go.jp/eng/index.html
[29] S.S. Penner, R. Seiser, K.R. Schultz, “Steps toward passive safe, proliferation-resistant nuclear power”, Progress in Energy and Combustion Science, Volume 34, p.275-287, 2008.
[30] http://www.substech.com/dokuwiki/doku.php?id=graphite_manufacturing_process
[31] NGNP Graphite Selectiujvon and Acquisition Strategy, Gen IV international forum, Sep. 2007.
[32] S. Schimmelpfennig, B. Glaser, “One Step Forward Toward Characterization: Some Important Material Properties to Distinguish Biochars”, Journal of Environmental Quality, Volume 41, p.1001-1013, Jul-Aug. 2012.
[33] J.L. Su, D.D. Perlmutter, “Porosity Effect on Catalytic Char Oxidation”, AIChE Journal, Volume 31, Issue 6, p.965-972, Jun. 1985.
[34] Something About Nuclear Graphite, T.X. Liang, Tsing Hua University.
[35] Nuclear Graphite Manufacture Microstructure and Virgin Properties, The University of Manchester, Oct. 2010.
[36] S.H. Chi, G.C. Kim, “Mrozowski Cracks and Oxidation Behavior of IG-110 and IG-430 Nuclear Graphites”, Transactions of the Korean Nuclear Society Spring Meeting, Chuncheon, Korea, May. 2006.
[37] NGNP High Temperature Materials White Paper, Idaho National Laboratory, Jun. 2010.
[38] S. Shiozawa, S. Fujikawa, T. Iyoku, K. Kunitomi∗, Y. Tachibana, “Overview of HTTR design features”, Nuclear Engineering and Design , Volume 233, p.11–21, 2004.
[39] E.S. Kim, C.H. Oh, H.C. No, B.J. Kim, INL/CON-07-12640, Idaho National Lab, 2007.
[40] Kazuhiko KUNITOMI, “Overview of JAEA’s Research Activity on HTGR”, 5th Annual VHTR R&D Technical Review Meeting 2012, May 22-24, 2012.
[41] C.H. Oh, E.S. Kim, H.C. No, N.Z. Chao, “Experimental Validation of Stratified Flow Phenomena, Graphite Oxidation, and Mitigation Strategies of Air Ingress Accident”, Report INL/EXT-08-14840, Idaho National Lab, 2008.
[42] E.S. Kim, Y.W. Kim, “Effect of a Thermal Oxidation on the Compressive Strength of Selected Nuclear Graphite”, Transactions of the Korean Nuclear Society Autumn Meeting, Korea, 2007.
[43] B.J. Kim, D. Kim, C.J, S.H. Chi, “Oxidation and Temperature Effects on the Fracture Toughness of Nuclear Graphite at VHTR”, Transaction of the Korean Nuclear Society Autumn Meeting, Korea, 2008.
[44] T. Takeda, M. Hishida, “Study on the Passive Safe Technology for the Prevention of Air Ingress during the Primary-Pipe Rupture Accident of HTGR”, Nuclear Engineering and Design, Volume 200, Issue 1-2, p.251-259, Aug. 2000.
[45] Experimental Validation of Stratified Flow Phenomena, Graphite Oxidation, and Mitigation Strategies of Air Ingress Accidents, Idaho National Laboratory, Dec. 2008.
[46] C. I. Contescu, R.W. Mee, P. Wang, A.V. Romanova, T.D. Burchell, “Oxidation of PCEA nuclear graphite by low water concentrations in helium”, Journal of Nuclear Materials, Volume 453, p.225-232, 2014.
[47] P. Wang, C.I. Contescu, S. Yu, T.D. Burchell, “Pore Structure Development in Oxidized IG-110 Nuclear Graphite”, Journal of Nuclear Materials, Volume 430, Issue 1-3, p.229-238, Nov. 2012.
[48] J. Kane, C. Karthik, D.P. Butt, W.E. Windes, R. Ubic, “Microstructural Characterization and Pore Structure Analysis of Nuclear Graphite”, Journal of Nuclear Materials, Volume 415, p.189-197, 2011.
[49] W.H. Huang, S.C. Tsai, C.W. Yang, J.J. Kai, “The Relationship between Microstructure and Oxidation Effects of Selected IG- and NBG- grade Nuclear Grphites”, Journal of Nuclear Materials, Volume 454, p.149-158, 2014.
[50] S.H. Chi, G.C. Kim, “Comparison of the Oxidation Rate and Degree of Graphitization of Selected IG and NBG Nuclear Graphite Grades ”, Journal of Nuclear Materials, Volume 381, p.9-14, 2008.
[51] C.I. Contescu, T. Guldan, P. Wang, T.D. Burchell, “The Effect of Microstructure on Air Oxidation Resistance of Nuclear Graphite”, Carbon, Volume 50, p.3354-3366, 2012.
[52] X. Luo, J.C. Robin, S. Yu, “Comparison of the Oxidation Behavior of Different Grades of Nuclear Graphite”, Nuclear Science and Engineering, Volume 151, p.121-127, 2005.
[53] Practical Aspects of Characterization of Air Oxidation of Graphite, Samina Azad, Graftech.
[54] W.H. Huang, S.C. Tsai, I.C. Chiu, C.H. Chen, J.J. Kai, “The Oxidation Effects of Nuclear Graphite during Air-Ingress Accidents in HTGR”, Nuclear Engineering Design, Volume 271, p.270-274.
[55] 黃偉豪，國立清華大學工程與系統工程系研究所碩士論文，2013.
[56] Wei-Hao Huang, Shou-Cheng Tsai, Chia-Wei Yang, Ji-Jung Kai, “The Relationship between microstructure and oxidation effects of selected IG- and NBG- grade nuclear graphites”, Journal of Nuclear Materials, Volume 454, Aug.2014, pp.149-158.
[57] Peng Wang, Cristian I. Contescu, Suyuan Yu, Timothy D. Burchell, “Pore structure development in oxidized IG-110 nuclear graphite”, Volume 430, Issue 1-3, Nov. 2012, pp.229-238
[58] Research Plan for Moisture and Air Ingress Experiments, PLN-4086, Idaho National Lab, 2012.
[59] ASTM, “Standard Test Method for Oxidation Mass Loss of Manufactured Carbon and Graphite”, ASTM C1179-91, 2000. Materials in Air.
[60] C.I. Contescu, S. Azad, D. Miller, M.J. Lance, F.S. Baker, T. D. Burchell, “Practical Aspects for Characterizing Air Oxidation of Graphite”, Journal of Nuclear Materials, Volume 381, p.15-24, Oct. 2008.
[61] J. Eapen, R. Krishna, T.D. Burchell, K.L. Murty, “Early Damage Mechanisms in Nuclear Grade Graphite under Irradiation”, Materials Research Letters, Volume 2, Issue 1, 2014, pp.43-50
[62] 材料電子顯微鏡學，國科會精儀中心，科儀叢書3
[63] 汪建民，材料分析，1998，中國材料科學學會
[64] Physical Principles of Electron Microscopy: An Introduction to TEM, SEM, and AEM, Ray F. Egerton, Springer Science+ Business Media, Inc.
[65] 教育部中北區K-12教育發展中心，遠距遙控電子顯微鏡教學網
[66] R. Moormann, H.K. Hinssen, K. Kuhn, “Oxidation Behavior of an HTR Fuel Element Matrix Graphite in Oxygen Compared to a Standard Nuclear Graphite”, Nuclear Engineering and Design, Volume 227, p.281-284, 2004.
[67] Y.S. Lim, S.H. Chi, K.Y. Cho, “Change of Properties after Oxidation of IG-11 Graphite by Air and CO2 Gas”, Journal of Nuclear Materials, Volume 374, p.123-128, 2008.
[68]http://carbon.atomistry.com/decomposition_carbon_dioxide.html
[69] E.L. Fuller, J.M. Okoh, “Kinetics and Mechanisms of the Reaction of Air with Nuclear Grade Graphites: IG-110”, Journal of Nuclear Materials, Volume 240, p.241-250, 1997.
[70] J.J. Lee, T.K. Ghosh, S.K. Loyalka, “Oxidation Rate of Nuclear-Grade Graphite IG-110 in the Kinetic Regime for VHTR Air Ingress Accident Scenarios”, Journal of Nuclear Materials, Volume 446, p.38-48, 2014.
[71] .J. Lee, T.K. Ghosh, S.K. Loyalka, “Oxidation Rate of Nuclear-Grade Graphite NBG-18 in the Kinetic Regime for VHTR Air Ingress Accident Scenarios”, Journal of Nuclear Materials, Volume 438, p.77-87, 2013.