核能一廠Mark-I型圍阻體氫氣擴散濃度GOTHIC程式分析模式建立

Development of Hydrogen Diffusion GOTHIC Model for MARK-I Containment of Chinshan Nuclear Power Plant

沈紘毅

指導教授 ： 白寶實

國立清華大學/原子科學院/核子工程與科學研究所/碩士(2012年)

摘要

由於日本發生福島核電廠事故過程中有引起氫氣爆炸，且日本福島電廠與台灣核能一廠皆為奇異公司BWR4型機組與Mark-I型圍阻體，因此核能一廠在假想發生福島核事故後氫氣在圍阻體中之濃度擴散及分布狀況，有否氫爆的威脅是本研究工作欲探討的重點。分析中，當爐心水位下降發生燃料棒裸露時，裸露的燃料棒在無法有效冷卻的情況下，護套表面溫度迅速竄升，鋯合金材質的燃料棒護套隨即與壓力槽內的水蒸汽進行劇烈的氧化反應，產生大量氫氣。氫氣釋出後，擴散並分布，有否在某些局部空間累積到達爆炸的濃度是本研究所關注的。
本研究採用著名的圍阻體安全分析程式GOTHIC建立氫氣擴散濃度分析模式，研究中採用MAAP程式提供之核能一廠SBO情況下的氫氣產生速率數據作為本分析之邊界條件。由於一次圍阻體內有填充氮氣，故不會產生氫氣爆炸的危險，研究中所關注的是二次圍阻體內部的氫氣濃度分布及累積會否造成氫爆。由於分析的結果並無實際數據做比較及評估，因此在進行本研究分析前先證實GOTHIC程式對圍阻體內氫氣擴散及濃度分布能作精準的計算，本研究先進行了一個實際實驗的Benchmark，以驗證GOTHIC程式在模擬氫氣擴散的適用性及準確度。
GOTHIC程式對選定實驗數據之分析結果與實驗數據在趨勢上相當吻合，由於參考文獻所提供的實驗參數不足，因此有部分數據的溫度與壓力是由本研究根據工程判斷給與合理之假設。另外實驗測量上會有量測誤差，故GOTHIC程式模擬能得到與實驗數據相同的趨勢已有相當程度的參考價值。更為驗證GOTHIC程式模擬結果，研究中使用一套著名之CFD軟體Fluent進行分析比對。在邊界條件相同情況下進行CFD軟體Fluent模擬之所得結果不只趨勢一樣，且分析所得的氫氣擴散濃度與GOTHIC分析結果比對也幾乎數值相近，差距很小。故根據分析比對結果可得知，GOTHIC程式用在Mark-I圍阻體進行氫氣擴散濃度之分析結果具有一定的適用度及準確度。

關鍵字

GOTHIC ； 馬克一型圍阻體 ； 福島事故 ； 氫氣爆炸 ； SBO

並列摘要

Because the consequences of the Fukushima Daiichi incident cause the hydrogen explosion and the collapse of the reactor building. This effect gave sharp memorized picture in men’s memory. The Chinshan Nuclear power plant (CSNPP) has the name BWR/4 type reactor and Mark-I Containment as Fukushima Daiichi. Therefore, this study is focused on the investigation of the hydrogen explosion if the Fukushima accident is assumed be occurred in the Chinshan Nuclear Power Plant.
This research has utilized GOTHIC code to establish the hydrogen diffusion analysis model and analyze the hydrogen diffusion and concentration inside containment . In this study, the hydrogen flow rate data offered from Modular Accident Analysis Program (MAAP) was adopted to build up the time varying boundary condition. Because the primary containment of CSNPP is filled with 96% nitrogen, that hydrogen explosion will not be occurred inside the primary containment versus time localization. But it is concerned that hydrogen concentration distribution and accumulation will cause the hydrogen explosion inside the second containment (reactor building). Because the GOTHIC simulation of this case has no actual data to do the comparison, so that a benchmark experiment of GOTHIC code with H2 diffusion and concentration calculation is first performed to assess the ability of GOTHIC code to accurately predict the transport of hydrogen, and this ability of H2 concentration calculations.
The GOTHIC simulation results showed the same trend and good consistency with the experiment. Due to the of lack of the information of experimental parameters, we assume some value of temperature and pressure in the analysis by the engineering judgment. Addition, measurements may possess errors, so the simulation results can be treated as a good reference example. Further measurements more, in order to verify the GOTHIC simulation results, CFD code-Fluent is also adopted by this study to analyze with (the same boundary conditions) the same problem and provide another meaning comparison case. The results showed not only the trend is the same but also the values is almost no difference. Therefore, according to the results of comparisons, the GOTHIC simulation results of hydrogen diffusion and concentration accumulation in the Mark-I Containment is applicable and accuracy enough.

參考文獻

5. Final Safety Analysis Report, Chinshan Nuclear Power Station Units 1 and 2, 2008.

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2. Electric Power Research Institute, “GOTHIC: Containment Analysis Package User Manual”, version 7.2a, NAI 8907-02 Rev. 17, January 2006.

3. Electric Power Research Institute, “GOTHIC: Containment Analysis Package Technical Manual”, version 7.2a, NAI 8907-06 Rev. 16, January 2006.

4. Electric Power Research Institute, “GOTHIC: Containment Analysis Package Qualification Report”, version 7.2a, NAI 8907-09 Rev. 9, January 2006.