含馬歇爾預存裂縫之沸水式反應器壓力槽可靠度評估

反應器壓力槽為核能電廠中最重要的壓力邊界組件，它若發生破壞將會引發嚴重災害。由於反應器壓力槽結構巨大，所以需以焊接方式製造而成，而依據經驗，其垂直焊道最容易產生破壞。反應器壓力槽焊道內的裂縫會隨時間生長而導致破壞的可能，且材料也會受到輻射脆化，增加壓力槽破壞的機率。本研究以蒙地卡羅模擬法配合機率破壞力學理論，評估焊道預存裂縫沸水式反應器壓力槽之破壞機率，其間我們考慮到裂縫成長機制、輻射脆化影響、低溫超壓之偶發事件、材料性質之不確定性、初始裂縫之隨機性、不同程度之非破壞檢測水準與更新等學理與現象。研究結果顯示，針對一商用沸水式反應器壓力槽，若每十年進行一次檢測與修復，則其運轉至40年之設計壽命時，破壞機率為4.32×10-5；若將模擬時間延長至60年，則破壞機率變為5.94×10-5。此外，相較於輻射脆化，初始裂縫成長為影響破壞機率的主要因素，因此若能透過檢測與更新有效控制裂縫長度，即可有效減低反應器壓力槽的破機率。

關鍵字

反應器壓力槽；機率破壞力學；低溫超壓事件；裂縫成長；輻射脆化；可靠度

並列摘要

The reactor pressure vessel (RPV) is the most important pressure boundary component in a nuclear power plant. The failure of RPV will cause serious hazard, and the vertical welds of RPV attribute very high probability of failure. The failure probability of RPV in general increases along with time owing to crack growth in welds of RPV. The increase is even more significant when radiation embrittlement is taken into consideration. In the present study, Monte Carlo Simulation (MCS) and Probabilistic Fracture Mechanics are employed to study the reliability of a Boiling Water Reactor Pressure Vessel (BWRPV). It is assumed that a predominant initial crack exists in the vertical welds of the RPV. When subjected to environmental conditions, the crack grows which, in turn, increases the failure probability of the vessel. In the modeling and analysis, the initial crack distribution, crack growth mechanism, low temperature over pressurization (LTOP) transients, radiation embrittlement, NDT examination, renew process and uncertainty of material properties are all considered. The result indicates that the probability of failure (POF) of the analyszed RPV is 4.32×10-5 after 40 years of operation if non-destructive inspection is employed and renewal action is taken every 10 years. Under the same inspection and repair condition, the POF decreases to 5.94×10-5 after 60 years of operation. It reflects that the POF of BWRRPV can be reduced effectively through periodic inspections and complete repair actions afterwards.

並列關鍵字

Reactor Pressure Vessel ； Probabilistic Fracture Mechanics ； Low Temperature Over Pressure ； Crack Growth ； Radiation Embrittlement ； Reliability

參考文獻

14. 張紘睿，非破壞評估可靠度之模型適合度探討，國立台灣大學機械工程學研究所碩士論文，民國94年

31. 林獻洲，核能電廠反應器壓力槽焊道之可靠度評估，國立台灣大學機械工程學研究所碩士論文，民國98年

2. Murphy, G., “Survey of Operating Experience to Identify Structural Degradation of Nuclear Power Plant Component,” International Journal of Pressure Vessels and Piping, Vol.22, pp.31-40,1986.

3. Electric Power Research Institute, BWR Reactor Pressure Vessel Shell Weld Inspection Recommendations (BWRVIP-05), BWR Vessel and Internals Project, Report TR-105697,1995.

4. Chery, L.B., “Risk-Informed Pressurized Water Reactor Vessel Inspection Interval Extension,” Proceedings of ICONE 12th International Conference on Nuclear Engineering April 25-29,2004.

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含馬歇爾預存裂縫之沸水式反應器壓力槽可靠度評估

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