臺灣博碩士論文加值系統

摘要
HI-STORM 100外觀為高度6.09 m，直徑3.36 m的混凝土圓柱形結構。系統内部含有一個焊接而成的不鏽鋼密封桶MPC（multi-purpose canister）用於儲存反應堆替換下來的燃料組件。本文選取MPC-32貯存桶（高度4.85 m，外徑1.78 m）和Westinghouse 17x17高燃耗（45GWd/MTU）壓水堆PWR（Pressurized Water Reactor）燃料組件作爲研究對象，主要的研究内容與結果如下：
（1）使用多孔介質模型等效替代燃料組件，合理簡化系統結構以減少網格數量減少計算成本。構建3D模型模擬燃料組件内流速與壓降的關係，並擬合出慣性阻力係數和黏性阻力係數以等效燃料組件内的流動特性。採用有效導熱係數模擬燃料組件的傳熱特性，軸向上使用面積平均法計算有效導熱係數，徑向上構建2D對稱模型，計算不同發熱功率與壁面溫度條件下燃料單元的最高溫度，根據(Bahney and Lotz, 1996)[1]提供的公式，擬合依賴於溫度的有效導熱係數關係式。
（2）在縂衰變熱功率為17kW的條件下模擬HI-STORM 100系統的熱流狀態。針對自然對流的兩種氣體模型①Boussinesq近似②不可壓縮理想氣體進行對比分析，驗證不可壓縮理想氣體模型計算的MPC内部流場與溫度場更符合實際情況。針對兩種常用的紊流模型①k-episilon②k-Ω進行對比分析，驗證了k-epsilon模型在模擬該現象時會導致高溫位置向下偏移的反常結果。
（3）分析了乾式貯存系統在實際運營過程中影響散熱性能的敏感因素。①模擬預測了冷卻年數從10年至55年期間系統的溫度分佈與流場特徵：在此期間，核廢料的衰變熱功率由24.52 kW下降至10.67 kW，系統最高溫度由630 K下降至542 K，MPC外殼最高溫度由410 K下降至355 K，空氣出口溫度由332 K下降至355 K，體積流率有0.088 "m" ^"3" "/s" 下降至0.065 "m" ^"3" "/s" ，初步粗略計算可知，進入環形通道内的空氣將帶走系統内將近80%的熱量。②討論了燃料組件衰變熱功率不均匀時對系統散熱性能的影響：將32個燃料組件分爲内部12個單元和外部20個單元，用内外單元發熱功率的比值X描述整個系統的熱源分佈。模擬結果驗證了當X≥1時，系統的散熱性能更好，當X＜1時，燃料組件的最高溫度會上升，並從自然對流和傳熱學兩個方面解釋該現象產生的原因。
關鍵詞：乾式貯存系統，CFD，多孔介質，自然對流，理想氣體，紊流模型，熱傳導，熱對流

ABSTRACT
HI-STORM 100 has a concrete cylindrical structure with a height of 6.09 m and a diameter of 3.36 m. The system contains a welded stainless steel sealed barrel MPC (multi-purpose canister) for storing the fuel components replaced by the reactor. This paper selects MPC-32 storage barrel (4.85 m in height, 1.78 m in outer diameter) and Westinghouse 17x17 high burnup (45GWd/MTU) PWR (Pressurized Water Reactor) fuel assembly as the research objects. The main research contents and results are as follows :
(1)Use the porous media model to replace the fuel assembly, reasonably simplify the system structure to reduce the number of grids and reduce the computational cost. A 3D model was constructed to simulate the relationship between flow velocity and pressure drop in the fuel assembly, and the inertial resistance coefficient and viscous resistance coefficient were fitted to be equivalent to the flow characteristics in the fuel assembly. The effective thermal conductivity is used to simulate the heat transfer characteristics of the fuel assembly. The area average method is used to calculate the effective thermal conductivity in the axial direction. A 2D symmetrical model is constructed in the radial direction to calculate the maximum temperature of the fuel unit under different heating power and wall temperature conditions. According to (Bahney & Lotz) , 1996), which fits the temperature-dependent effective thermal conductivity relationship.
(2)The heat flow state of the HI-STORM 100 system was simulated under the condition of a total decay heat power of 17 kW. Comparing and analyzing the two gas models of natural convection ① Boussinesq approximation ② incompressible ideal gas, it is verified that the internal flow field and temperature field of the MPC calculated by the incompressible ideal gas model are more in line with the actual situation. Comparing and analyzing two commonly used turbulence models ①k-ε②k-ω "SST" , it verifies that the k-ε model can cause the abnormal result that the high temperature position shifts downward when simulating this phenomenon.
(3)The sensitive factors that affect the heat dissipation performance of the dry storage system in the actual operation process are analyzed. ①The simulation predicts the temperature distribution and flow field characteristics of the system during the cooling years from 10 years to 55 years: During this period, the decay thermal power of nuclear waste decreased from 24.52 kW to 10.67 kW, and the maximum temperature of the system decreased from 630 K to 542 K, The maximum temperature of the MPC shell dropped from 410 K to 355K, the air outlet temperature dropped from 332 K to 355 K, and the volume flow rate dropped from 0.088 "m" ^"3" "/s" to 0.065 "m" ^"3" "/s" . The preliminary rough calculation shows that the air entering the annular channel will be taken away from the system. Nearly 80% of the calories. ②The influence on the heat dissipation performance of the system when the decay thermal power of the fuel assemblies is not uniform is discussed: 32 fuel assemblies are divided into 12 internal units and 20 external units, and the heat source distribution of the whole system is described by the ratio X of the heating power of the internal and external units. The simulation results verify that the heat dissipation performance of the system is better when X≥1, and the maximum temperature of the fuel assembly will rise when X < 1, and the reasons for this phenomenon are explained from the aspects of natural convection and heat transfer.
Keywords: dry storage system, CFD, porous media, natural convection, ideal gas, turbulence model, heat conduction, heat convection

目錄
摘要 i
ABSTRACT iii
目錄 v
圖目錄 vii
表目錄 ix
符號表 x
第一章 緒論 1
1.1 研究背景 1
1.2 核廢料貯存方式 2
1.2.1 深層地質貯存 2
1.2.2 室内水池貯存 2
1.2.3 乾式貯存 3
1.3 研究方向及内容 4
1.4 文獻回顧 5
第二章 燃料組件的流動與傳熱特性 9
2.1 數學原理與控制方程 9
2.2 多孔介質模型 10
2.3 燃料組件流動特性 11
2.3.1 網格獨立性驗證 13
2.3.2 模擬結果與阻力係數的擬合 16
2.4 燃料組件傳熱特性 18
2.4.1 軸向傳熱特性 18
2.4.2 徑向傳熱特性 19
第三章 HI-STORM 100乾式貯存系統熱流分析 23
3.1 幾何模型及重要尺寸參數 23
3.2 邊界條件與初始條件 25
3.3 網格獨立性驗證 26
3.4 氣體模型 27
3.4.1 Boussinesq近似 27
3.4.2 不可壓縮理想氣體 28
3.4.3 計算結果對比與分析 29
3.5 紊流模型 34
3.5.1 模擬結果 35
3.6 本章小結 38
第四章 系統散熱性能敏感性分析 39
4.1 冷卻年數的影響 39
4.1.1 模擬結果與分析 40
4.2 燃料組件衰變熱配比的影響 43
4.2.1 計算結果與對比 44
4.2.2 總結與分析 48
第五章 總結與展望 49
5.1 工作總結 49
5.2 不足與未來研究方向 49
參考文獻 51

參考文獻
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