熔鹽式反應系統的特色為使用熔鹽作為工作流體，而可裂變核種溶解於熔鹽中，此一特性有別於傳統固態燃料反應系統，需要另外考量燃料的膨脹與流動。此系統中，中子物理性質會與熱流性質互相影響，因此中子物理與熱流耦合計算為一了解其特性的步驟。本研究建立一個耦合計算方法，以模擬Feynberg提出自然循環熔鹽迴路的起爐暫態，也更進一步的考量反應器動力學以模擬Molten Salt Reactor Experiment （MSRE）的暫態。
本研究使用SCALE-CSAS6作為爐心物理的計算程式，FLUENT作為熱流的計算程式。兩個自行建立的程式，分別為中子物理與熱流耦合程式（Neutronics and Thermal-hydraulic Coupling Code, NTC）與耦合使用者自訂函式（Coupling User Defined Functions, Coupling UDF）被用於自動化計算流程以進行SCALE-CSAS6與FLUENT之間的資料交換。為確認本研究SCALE-CSAS6與FLUENT使用的經驗與技術無誤，本研究分別使用這兩個工具模擬文獻上的案例，並確認結果與文獻符合，也將自行建立的程式用於莊鈞皓論文中的案例，其使用手動的方式進行中子物理以及熱流的資料交換。本研究結果與莊鈞皓論文中的結果具有一致性，說明了自行建立的程式可正確完成其功能。
第一個案例使用此方法進行自然循環熔鹽迴路的耦合計算，為使模擬在物理上較為合理，本研究建立了新模型、考量熱膨脹對於反應度的負回饋以及移動控制棒以補償負反應度回饋。經由起爐暫態分析，本研究得到了此系統起爐以及穩定運轉狀態時的功率、溫度以及速度分佈。第二個案例模擬具有實驗值的MSRE暫態，當系統爐心功率會隨時間變化時就必須考慮反應器動力學，為此本研究另外開發反應器動力學以及延遲中子孕母流動造成反應度損失的計算工具。本案例耦合計算結果與實驗值對照大致符合，證明本研究的方法可行。

Molten salt system is characterized by using molten salt as its working fluid and fissile dissolved in the molten salt. Unlike traditional solid fuel systems, molten salt expansion and circulation should be additionally considered. Since neutronics and thermal-hydraulic influence each other in the system, neutronics and thermal-hydraulic coupling analysis is a step to understand its characteristics. This study developed a coupling methodology to analysis a molten salt natural circulation loop and the Molten Salt Reactor Experiment (MSRE).
This study used SCALE-CSAS6 as neutronics calculation code and FLUENT as thermal-hydraulic calculation code. Two self-developed codes, Neutronics and Thermal-hydraulic Coupling Code (NTC) and Coupling User Defined Functions (Coupling UDF), were used to automatically control the calculation and exchange data between SCALE-CSAS6 and FLUENT. This study has showing that it operated SCALE-CSAS6 and FLUENT correctly by reproducing the results in the references respectively. The self-developed codes were also applied to the case of Chuang's calculation which exchanged neutronics and thermal-hydraulic data manually. The corresponding results imply that NTC and Coupling UDF can operate correctly.
The first case is startup analyses for the simple natural circulation loop. To make the calculation more physically realistic, this study built new models, considered negative reactivity feedback from thermal expansion, and moved the control rods to compensate the negative reactivity feedback. Via the analyses, my research obtained the temperature, velocity, and power distribution at the startup and stable operational state. The second case is MSRE transient simulation. It is necessary to take account of reactor dynamics when reactor power varies with time. Reactor dynamics and delayed neutron precursors movement reactivity loss codes were additionally developed. This study obtained similar results with the experimental data and thus proved that the coupling methodology is feasible.

摘要 i
Abstract ii
致謝 iii
目錄 iv
表目錄 vii
圖目錄 ix
符號說明 xii
第一章 緒論 1
1.1 研究背景 1
1.2 動機與研究目標 1
第二章 文獻回顧 3
2.1 熔鹽式反應器 3
2.1.1 MSRE介紹 4
2.1.2 熔鹽式反應器之特性 7
2.2 自然循環熔鹽迴路模型 8
2.2 中子物理及熱流耦合計算方法 11
第三章 計算工具介紹 15
3.1 中子物理模擬程式SCALE-CSAS6 15
3.2 計算流體力學模擬程式 17
3.2.1 Gambit模型建立 19
3.2.2 FLUENT平行運算 19
3.2.3 使用者自訂函式介紹 20
3.2.4 熱流統御方程式 21
3.3 自動化耦合計算 23
3.3.1 中子物理與熱流耦合程式建立 25
3.3.1.1 中子物理與熱流耦合程式必要功能建立 26
3.3.1.2 中子物理與熱流耦合程式自定功能建立 29
3.3.2 中子物理與熱流耦合程式操作所需檔案 31
3.3.3 耦合使用者自訂函式建立 35
3.3.4 掛載耦合使用者自訂函式操作 37
3.4 計算工具的驗證 40
3.4.1 SCALE-CSAS6驗證 40
3.4.1.1 模擬模型 40
3.4.1.2 模擬結果 41
3.4.2 FLUENT驗證 43
3.4.2.1 模擬模型 43
3.4.2.2 模擬結果 45
3.4.3 自動化程式功能的驗證 49
3.4.3.1 模擬模型 49
3.4.3.2 疊代模擬結果 54
3.4.3.3 穩態模擬結果 60
3.4.3.4 自動化疊代測試結果討論 63
第四章 案例一：自然循環熔鹽迴路分析 65
4.1 模型建立 65
4.1.1 SCALE-CSAS6模型 65
4.1.2 FLUENT模型 67
4.2 計算流程與模擬設定 70
4.3 自然循環熔鹽迴路分析結果72
4.3.1 起爐暫態結果 72
4.3.2 系統有效增值因數異常下降探討 74
4.3.3 穩定運轉狀態結果 80
4.5 計算靈敏度分析 83
4.5.1 疊代數目敏感度測試結果 83
4.5.2 時間步伐敏感度測試結果 85
第五章 案例二：MSRE暫態分析 87
5.1 模型建立 88
5.2 計算流程與模擬設定 93
5.3 計算工具建立 98
5.3.1 反應器點動力學方程式求解 98
5.3.1.1 求解方法 98
5.3.1.2 驗證計算 101
5.3.2 熔鹽循環造成反應度流失計算 107
5.3.2.1 MSRE反應度流失驗證計算 108
5.3.2.2 自然循環熔鹽迴路反應度流失計算 110
5.4 MSRE暫態分析結果 112
第六章 結論與未來工作 113
6.1 結論 113
6.2 未來工作 115
參考文獻 116
附錄A 相關程式碼列表 121
A.1 Coupling UDF程式碼 121
A.2 NTC程式碼 130
A.3 NTC Dynamics程式碼 148

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