反應器壓力槽(Reactor Pressure Vessel, RPV)為核能電廠中重要的壓力邊界組件，在運轉時承受高劑量中子照射，將導致其腹帶區(Beltline region)內的殼壁材料產生輻射脆化，進而影降低其破裂韌性。故經過多年的運轉後，RPV的結構完整性評估變得十分重要，應謹慎評估以確保核能安全。本研究針對壓水式反應器（Pressurized Water Reactor, PWR）RPV在承受壓力熱震（Pressurized Thermal Shock, PTS）下其殼壁材料的化學組成不確定性以及考慮注入水的不均勻性對於RPV破壞機率的影響。
在研究中所使用的分析軟體為美國橡樹嶺國家實驗室所開發的機率破裂力學（Probabilistic Fracture Mechanics, PFM）軟體FAVOR(Fracture Analysis of Vessels – Oak Ridge) 。壓力熱震暫態則使用美國核能管制委員會(United States Nuclear Regulatory Commission, U.S. NRC)對於Beaver Valley電廠所分析的暫態來做為輸入參數。針對不同的化學成分與不同的輻射脆化條件下進行分析，發現銅和鎳的改變對於PWR壓力容器腹帶區材料的輻射脆化和破壞機率有很大的影響，可作為安全法規訂定與電廠操作風險上的參考。
另外，暫態發生時冷水注入的不均勻性所形成的煙雲效應（Plume effect）對於FAVOR在計算三迴路壓水式反應器RPV破裂機率時的影響在本研究中也有納入考慮。從其結果可知三迴路同時注水下是否考慮煙雲效應對於RPV破壞機率結果影響並不明顯。呼應IAEA-TECDOC-1627報告中所提及當壓水式反應器RPV遭受壓力熱震暫態時所發生的煙雲效應是可以忽略的；但如果是只有一迴路失效則會有一定程度的影響。

The reactor pressure vessel (RPV) is one of the most important components in a nuclear power plant which is exposed to various transients associated with high neutron fluence during operation. The neutron irradiation may cause the vessel material to become more brittle especially for the weld and plate materials in the beltline region corresponding to the reactor core. After years of operation, the structural integrity of the degraded RPV becomes crucial and needs to be evaluated to ensure the nuclear safety. This paper is to study the effects of copper and nickel content variations and non-uniform temperature distribution causing by inlet water on the fracture probability of the pressurized water reactor (PWR) pressure vessel subjected to pressurized-thermal-shock (PTS) transients.
The probabilistic fracture mechanics (PFM) code, FAVOR, which was developed by the Oak Ridge National Laboratory in the United States, is employed to perform the analyses. Some PTS transients analyzed from Beaver Valley Unit 1 for establishing the USNRC’s new PTS rule are applied as the loading conditions. It is found that the content variation of copper and nickel will significantly affect the radiation embrittlement and the fracture probability of PWR pressure vessels. The results can be regarded as the risk incremental factors for comparison with the safety regulation requirements on vessel degradation as well as a reference for the operation of PWR plants in Taiwan.
We also consider about the effect of non-uniform temperature distribution, plume effect, caused by cold cooling water inlet on the fracture probability of the three loop PWR pressure vessel subjected to PTS events. It is found that the plume effect will not have a significant impact on the fracture probability of the PWR under the injection of three loops cooling water at the same time consist with the IAEA-TECDOC-1627 report., However, it would increase the fracture probability even if there is only one loop failure.

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