- 學位論文
用過核子燃料乾式貯存設施受震之動態反應研究
Study on Seismic Response of Spent Fuel Dry Storage Facility
摘要
用過核子燃料之處理，對核能電廠之營運相當重要。目前在台灣，核能一廠內供短期貯存之燃料池空間即將不足，而供長期存放的最終處置場又尚未確定，故實有必要興建供中期貯存之乾式貯存設施。由於乾式貯存設施多屬自立式結構，在地震發生時，可能會產生滑動或傾覆等穩定性問題，因此，本研究針對將設在核能一廠內之用過核燃料乾式貯存設施，分析其受地震作用時之動態反應。 乾式貯存設施包含座落於土層上之基礎版，以及置放於基礎版上之貯存護箱。對於其受震反應，前人所採之分析法大致有兩種：一為耦合模型，亦即建立護箱~基礎版~土壤互制之模型，同時模擬土壤結構互制效應及護箱與基礎版間之非線性接觸行為；另一為非耦合模型，採兩階段分析，先以簡化之土壤~結構互制模型求取基礎版運動，再以該運動輸入考慮界面接觸行為之基礎版~護箱模型，求取護箱之受震反應。前者能有效掌握乾式貯存設施之受震行為，但所耗費分析成本過大；後者能大幅降低分析成本，然可能無法準確反映結構受震行為。 本研究以有限元素軟體ABAQUS，建立上述兩種模型進行比較。由分析結果可知，非耦合模型相較於耦合模型，會產生不合理之高頻加速度反應，且護箱之滑動與搖擺運動皆偏不保守。本研究針對此缺失，對非耦合模型進行修正，於第二階段分析建立考慮土壤阻抗之基礎版~土壤互制模型。由案例分析可知，本研究提出之修正模型可減小非耦合模型之不合理高頻反應，且分析效率又比耦合模型高，故具工程應用性，但由於其無法考慮土壤結構互制效應與界面接觸行為之交互作用，分析所得之結構動態反應與耦合模型仍有差異，使用上需特別注意。
並列摘要
Storage of spent fuel is very important for the operation of nuclear power plant (NPP). In Taiwan, the space of water pools for temporary storage of spent fuel in the 1st NPP is running out, and the site of final storage facility is not decided yet. Therefore, the installation of dry type interim storage facility is imperative. In most dry storage facilities, storage casks are free-standing on the foundation pad, leading to concerns of their stability such as excessive sliding and overturning when subjected excitations. Consequently, this research focuses on the seismic response of the spent fuel dry storage facility. For analyzing the seismic responses, two types of method are often used. One is to establish a cask-pad-soil coupled model by which the effect of soil-structure interaction (SSI) effect and the nonlinear contact behavior between the cask and pad are simulated at once. The other includes two steps. A simplified model for SSI analysis is established first to deduce the pad motions. Then it is used as the input motion for a pad-cask model in which the contact behavior on the interface is considered. The former assesses accurately the seismic response of dry storage facility, but the computational cost is expensive; the latter reduces the cost apparently, yet the results may be unsatisfactory. In this study, the computer program ABAQUS is adopted to establish a coupled model and a decoupled model to analyze the seismic response of dry storage facility. Base on the results obtained, it can be found the decoupled model will have unreasonable high frequency acceleration and unconservative sliding and rocking motion. To overcome this difficulty, a modified decoupled model is proposed, in which the equivalent soil impedance is introduced in the pad-cask model. It can reduce the high frequency responses substantially. However, when using this approach, it should noted that the interaction between the SSI effect and the contact behavior on interface is still not taken into account.