本研究係針對採多程在線裝卸 (multi-pass online refueling) 之燃料營運模式的球床式反應器 HTR-10，進行爐心的模擬與特性分析。HTR-10屬於高溫氣冷式反應爐，具有球型之燃料元件，採用多程在線裝卸之燃料管理模式。在先前的文獻中，已成功建立了混和式燃料裝卸模型，並採用一次通過 (once through then out) 的燃料營運模式進行模擬，然而為了更加符合 HTR-10 實際的運轉狀態，本論文建立了多程在線裝卸燃料的模擬方法，並對爐心模型進行改良。本文採用蒙地卡羅計算程式 MCNP6 進行計算，並使用 ENDF/B-VII 之截面資料庫，假設爐心溫度為 900 K，且均勻分布。
本研究將爐心分成數個燃料區，並透過移動燃料區內的燃料組成來近似燃料球的滾動，而回填時的燃料組成則透過事先建立的燃耗值對應核種組成資料庫來進行對照。而為符合爐心內不同位置的燃料球流速，本論文將爐心設計為具三個同心圓之軸向流道的三流道爐心模型，各流道內依據其徑向位置對應之燃料球停滯時間再區分成數個具有相同燃料球數量的燃料區，為了確保模型的合理性，本論文亦採用蒙地卡羅法對燃料球體積進行計算與確認。由研究結果顯示，適用於 HTR-10 最高的回填燃料之比例為 0.8，而在三流道模型的模擬上，爐心約在 700 天時會達到平衡態，其中位於最外圍之燃料球將會具有最高之燃耗值。雖然在最外圍的燃料區具有最低的中子通量，但因為其較高的熱中子比例，使得爐心外圍仍具有偏高的功率分佈，同時也顯示，採用多程通過之 HTR-10 爐心功率分佈會較採一次通過時更加均勻。本研究亦針對添加新鮮燃料球後產生之中子毒物對爐心之影響進行探討，發現在更換燃料初期會有些微的誤差產生，但對長期的 keff 變動趨勢並不會有太大的影響，也驗證了本論文模擬方法的正確性。

This study aims to investigate the core characteristics of on-line refueling fuel loading scenario in HTR-10. HTR-10 is an experimental high-temperature-gas-cooled pebble-bed reactor constructed in China. By utilizing multi-pass fuel management scheme, the pebbles in HTR-10 pass through the core several times via on-line refueling. In our previous study, a layer-mixed-shell fuel movement model was proposed to simulate the dynamic operation of HTR-10. However, this model was established based on the OTTO (Once Through Then Out) fuel loading scenario, rather than the multi-pass one that was actually utilized in HTR-10. In order to simulate the on-line refueling in a more realistic way, a comprehensive model based on multi-pass fuel loading scenario is thus developed. In this study, all the computations were performed using the MCNP6 computer code together with the ENDF/B-VII continuous energy neutron data library. The model was constructed by dividing the core into three radial zones with different amount of horizontally layers according to the pebbles’ residence time, and a volume calculation by using Monte-Carlo method has confirmed the feasibility of the model. In the refueling process, a certain ratio of fuel pebbles in the bottom layers are refueled into the top layers together with fresh fuel pebbles, and those in other layers move downward to their next layer. Besides, an average burnup for the top layer is resulted by considering the supplement of fresh fuel pebbles. A pre-generated fuel composition library, containing the content of both actinides and fission products of fuel pebbles as a function of burnup, is built by carrying out full core depletion calculations. The fuel composition in the top layer of the core is then obtained by interpolating its average burnup from the library. The results revealed that the core reaches an equilibrium fuel cycle approximately after 700 EFPD, with a best refueling ratio of fuel pebbles 80%. The core characteristics such as power distributions, amounts of major and minor actinides, average burnup of the discharged fuel pebbles were also investigated. Besides, another model considering the actual distribution of fresh fuel is constructed to analyze the influence of burnable poison produced after refueling in the last part of this study, verifying the accuracy of the refueling method.

摘要 i
Abstract ii
致謝 iv
表目錄 vii
圖目錄 viii
第一章 前言 1
第二章 文獻回顧 4
2.1 反應器設計參數 5
2.2 反應器燃料設計 7
2.3 模型建立 8
2.4 燃料營運方式 13
2.5 軸向動態運轉模型 17
2.6 徑向動態運轉模型 19
2.7 混合式燃料裝卸模型 21
2.8 爐心核種隨燃耗值變化之分析 23
2.9 研究動機 23
第三章 計算方法與程式介紹 25
3.1 MCNP發展史 25
3.2 截面資料庫介紹 26
3.3 臨界計算 26
3.4 燃耗計算 27
第四章 反應器模型建立與燃耗特性分析 29
4.1 HTR-10模型建立 29
4.1.1 TRISO顆粒模型 29
4.1.2 燃料球單位晶格建立 31
4.1.3 爐心模型建立 32
4.2 多層燃料裝卸之模擬程序 34
4.2.1 軸向分層爐心模型 34
4.2.2 燃料球裝卸程序 35
4.2.3 燃耗資料庫之建立 36
4.2.4 燃耗值修正係數 36
4.3 燃耗特性分析 38
4.3.1 軸向分層之燃料多程在線裝卸模擬結果 38
4.3.2 燃耗值修正係數分析 41
第五章 多流道爐心模型建立與燃耗分析 44
5.1 燃料球體積計算方法 44
5.1.1 蒙地卡羅法體積計算 44
5.1.2 靈敏度測試 46
5.1.3 HTR-10之球型燃料體積計算 48
5.2 多流道爐心模型建立 52
5.2.1 燃料球流道設計 52
5.2.2 三流道之多程在線裝卸爐心運轉模擬 61
5.3 三流道模型之燃耗特性分析 62
第六章 改良型三流道爐心模型與燃耗分析 69
6.1 改良型三流道爐心模型建立 69
6.1.1 三流道爐心模型修改 69
6.1.2 改良型三流道模型之多程在線裝卸燃料模擬方法 75
6.2 改良型三流道模型燃耗特性分析 76
6.3 新鮮燃料球產生之中子毒物效應 83
第七章 結論與未來建議 89
7.1 結論 89
7.2 未來建議 90
參考文獻 91

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