發(fā)布時間：2018-02-05 17:00

  本文關(guān)鍵詞： 熔化實驗 包殼熔化 單根燃料棒 破裂失效 凝固/熔化　出處：《中國科學技術(shù)大學》2017年碩士論文　論文類型：學位論文

【摘要】：核反應(yīng)堆嚴重事故的研究是近幾十年來核安全領(lǐng)域的重要課題。自三哩島事故后,世界多國的多個組織或者機構(gòu)分別進行了不同類型的大型實驗,探究嚴重事故中出現(xiàn)的各種現(xiàn)象和機理,同時也發(fā)展了如SCDAP/RELAP5和MELCOR等多種嚴重事故系統(tǒng)分析程序。單根燃料棒的熔化過程作為嚴重事故中堆芯損壞的重要環(huán)節(jié),決定著事故的發(fā)展走向和嚴重程度。然而,現(xiàn)有的對堆芯熔化中燃料棒的熔化的相關(guān)認知依然缺乏,嚴重事故分析程序?qū)@一過程的處理也多做工程簡化或忽略。以單根燃料棒的熔化過程為研究目的,本文通過實驗模擬和數(shù)值計算的手段對錫包殼的熔化過程進行詳細的研究。模擬實驗采用低熔點金屬錫作為熔化對象,通過重鑄和再加工,形成不銹鋼加熱棒外裹特定厚度的錫包殼。通過改變加熱功率、包殼厚度以及環(huán)境條件等影響條件,分析對包殼的熔化過程的影響。實驗采用可視化,并用DV機記錄熔化過程中的形態(tài)變化。實驗結(jié)果歸納了熔化過程中的三個階段:加熱階段、熔化階段和解體階段,其中的熔化階段根據(jù)出現(xiàn)的現(xiàn)象分為液滴析出、腫脹變形和"熔孔"三個環(huán)節(jié)。針對其中的腫脹變形和"熔孔"現(xiàn)象,引入圓柱壁應(yīng)力模型進行定性分析,得出腫脹變形程度取決于包殼厚度。對包殼出現(xiàn)的"熔孔"現(xiàn)象進行定量分析和預測,得出包殼"熔孔"破裂失效高度隨著加熱功率升高而降低,而且與加熱功率和熔化時間呈函數(shù)關(guān)系。最后,本文對比了不同的環(huán)境條件對熔化過程產(chǎn)生的影響。數(shù)值計算采用成熟CFD軟件ANSYS FLUENT,利用其中的凝固/熔化模型與VOF耦合對實驗進行二維計算。與實驗結(jié)果類似,計算過程分為加熱、熔化、破口和再凝固等4個階段。熔化階段中存在加熱棒加熱和高溫液體向下匯聚的兩種熱量傳遞過程。通過提取原形狀區(qū)域的固相分數(shù)為參考量,定量分析了破口產(chǎn)生、加熱功率和環(huán)境溫度對熔化的影響。結(jié)果表明,破口的產(chǎn)生對熔化的過程具有轉(zhuǎn)折性的意義,破口高度與環(huán)境溫度存在較大的依賴關(guān)系。
[Abstract]:Study on severe accident of nuclear reactors is an important research topic in the field of nuclear safety in recent decades. Since the Three Mile Island accident, many countries in the world a number of organizations or institutions were large different types of experiment, various phenomena and mechanism in case of a serious accident inquiry, has also developed such as SCDAP/RELAP5 and MELCOR and other serious accident system analysis program. The melting process of single fuel rod as a serious accident in the reactor core damage important link, determines the development trend and the severity of the accident. However, the existing of melting of fuel rods and core melt in the cognition is still lacking, analysis procedures of the process is more simplified or ignore the serious accident. In the melting process of a single fuel rod for the purpose of the study, through experimental simulation and numerical calculation method of tin cladding melting process of detailed research . simulation experiment with low melting point metal tin melting as object, and then processing by recasting and forming stainless steel heating rod coated with a specific thickness of the tin cladding. By changing the heating power, cladding thickness and environmental conditions affect the conditions, influence analysis of melting process of cladding. The experimental visualization, and morphological changes the DV record in the melting process. The experimental results are summarized in three stages: the stage of heating in the melting process, melting stage and disintegration stage, the melting stage according to the phenomenon of droplet is divided into precipitation, swelling and "melt hole" three links. The swelling deformation and "melt hole" the phenomenon, introducing cylinder wall stress model and qualitative analysis, the swelling deformation depends on the cladding thickness of cladding. The "melt hole" phenomenon for quantitative analysis and prediction, the shell of "melt hole" with the height of fracture failure The heating power is increased, and the function relation with the heating power and the melting time is. Finally, this paper compares the effects of different environmental conditions on the melting process. The numerical calculation of the mature CFD software ANSYS FLUENT, by which the solidification / melting model coupled with VOF on experimental two-dimensional calculation. Similar to the experimental results, calculation the process is divided into 4 stages of heating, melting, solidification and then break. There are two kinds of heat heating and high temperature liquid downward collection melting stage transfer process. Through the solid fraction extract the original shape as a reference, quantitative analysis of the breach, effect of heating power and environmental temperature on the melting results. That breach of melting process of turning the meaning of existence depends greatly on the gap height and ambient temperature.

【學位授予單位】：中國科學技術(shù)大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TL364

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本文編號：1492370