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研究生:張明睿
論文名稱:利用CFD進行HTGR空氣侵入事故之研究
論文名稱(外文):Investigation of Air Ingress Accident in a HTGR through CFD Methodology
指導教授:馮玉明馮玉明引用關係
學位類別:碩士
校院名稱:國立清華大學
系所名稱:核子工程與科學研究所
學門:工程學門
學類:核子工程學類
論文種類:學術論文
論文出版年:2012
畢業學年度:100
語文別:中文
論文頁數:90
中文關鍵詞:高溫氣冷式反應器空氣侵入事故計算流體力學石墨腐蝕氣體分子擴散運動
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現今核能安全議題已成為國際間最被關注的焦點,核電如能繼續被選項,擔任未來供電主流,核安之改良及增進勢不可免。第四代核反應器已透過一段時間之研究與開發,其技術已達成熟。第四代核反應器之一-高溫氣冷式反應器(High Temperature Gas cooled Reactor, HTGR),其設計目標朝著更深度之被動安全,更高的熱功效率及發電效率,更高之經濟性與更良好的環境友善度,將為未來核能發展之趨勢電廠之一。HTGR核反應器最嚴重之事故為空氣侵入事故,因此在HTGR核反應器發生空氣侵入事故時,分析並了解事故發生後的物理現象及其嚴重性是必要的。
本研究主要以商用流體力學軟體CFD來模擬計算三維暫態模型,分析高溫氣冷式反應器內部爐心之熱流現象。主要研究對象為空氣侵入反應器爐心內部所造成之事故影響,研究中所分析之事故是使用穩態運轉之狀態當作事故發生時之初始條件。此事故之發生是由於連接蒸氣產生器與反應器壓力槽之間之Hot gas duct發生斷裂,造成外界空氣經由破口處利用氣體分子擴散運動進入爐心內部。空氣進入反應器爐心後,由於空氣中之氧分子與高溫石墨產生一系列之化學反應,此反應將會造成燃料元件腐蝕而使燃料元件表面受損,嚴重可能導致放射性物質外洩。因此燃料組件表面之腐蝕嚴重情況就成了一個輻射物質會否外釋之安全性之重要指標。
本研究中,隨著事故發生時間之演變,石墨腐蝕最為嚴重的地方均在爐心燃料區域之下半部,因此未來第四代HTGR反應器之設計上,可以嘗試在腐蝕最為嚴重之位置設置一些安全保障作為,讓氧氣之濃度可以平均散佈在爐心燃料區內部,而不會集中在特定區域。

Nuclear power plant safety is one of the most important part issues of international energy usage nowadays. Generation IV nuclear reactors have been investigated and developed for a period of time, and will be one of the the major electricity supplies for the future global energy requirements efficiently and safely. High Temperature Gas Cooled Reactor (HTGR) is one type of generation IV reactors, which is developed successfully and waited for being used to solve future the energy shortage problem worldwide. Although, there is already highly safe design for HTGR, but deeper understanding and manipulating the hypothetical severe accident is still necessary. Air-ingress accident analysis of GEN IV HTGR is the main purpose of this study.
In this study, CFD (Computational Fluid Dynamics) is used for investigating the thermal-hydraulic phenomena in HTGR while air-ingress is happening there after. At the beginning, normal operating conditions is obtained by steady-state simulation. Transient simulation is used for understanding the thermal-hydraulic phenomena of the HTGR core since the severe accident incipience. The pipe between reactor vessel and steam generator, which is called hot gas duct, broke during the accident started. This pipe broken will cause the outside air diffused into the reactor vessel. Fuel assembly will be corroded by oxygen, due to a series of chemical interaction between oxygen and high temperature graphite. As a result, radioactive fission products may be released into outside environment space. Obviously, the corrosion problem on fuel assembly is the key issue of HTGR safety.
After a long period of interaction between oxygen and fuel assembly, the fuels in the lower region of the core damaged the most. As a consequence, some safety devices are needed to be design and equipped for making air diffuses uniformly in vessel to avoid the non uniformed corrosion situation.

摘要 i
ABSTRACT ii
致謝 iv
目錄 v
表目錄 vii
圖目錄 viii
第一章 緒論 1
1.1 研究背景 1
1.2 文獻回顧 2
1.3 GT-MHR600簡介 5
1.4 研究目的 9
1.5 分析工具 10
第二章 理論模式與數值方法 12
2.1 統御方程式 12
2.2 數值方法 20
2.2.1 離散方程式 20
2.2.2 離散方法 21
2.2.3 鬆弛因子 22
2.2.4 SIMPLE演算法 22
第三章 研究方法 24
3.1 研究流程 24
3.2 GT-MHR600基本模型描述 25
3.3 GT-MHR600全功率運轉之描述 30
3.4 GT-MHR600 Hot gas duct斷管事故描述 31
第四章 材料性質 38
4.1 流體與固體之材料性質 38
4.2 混合材料性質 41
4.3 多孔性介質參數 43
4.4 化學反應性質參數 44
第五章 結果與討論 45
5.1 全功率運轉分析結果 45
5.2 發生Hot gas duct斷管事故之分析結果 48
5.2.1 氣體進入之情況 48
5.2.2 各氣體之分布情形 51
5.2.3 爐心內燃料區域石墨腐蝕量之分布情形 65
第六章 結論 86
參考文獻 87
附錄1. 爐心衰變熱函數程式碼 90

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