2011年3月11日，日本發生Mw 9.0的東北地方太平洋近海地震，引發大海嘯。東京電力公司所屬的福島第一核能電廠，因強烈地震動及海嘯規模均超過其電廠之設計基準，而導致嚴重核子事故，衝擊全球。許多發展核能應用的國家皆審慎全面體檢核能電廠之安全性，並嚴格檢視、修改相關評估、設計及審查管制規範，提出新的管制要求。美國核能管制委員會(Nuclear Regulatory Commission, NRC)組成近期專案小組(Near-Term Task Force, NTTF)進行調查與檢討，隨後出具研究報告並提出35項改善建議，其中建議事項第2.1、2.3與9.3項有關地震、水患、緊急應變的部分，NRC於2012年3月12日以發送法令信函方式，稱「10 CFR 50.54(f) Letter」，要求全美核能電廠持照者，必須遵照指定事項辦理相關作業。其中，NTTF建議事項2.1之地震重新評估(Seismic Reevaluation)部分，簡稱「NTTF 2.1: Seismic」，係指NRC要求營運中核能電廠反應器廠址需依目前資訊(包括最新的地質調查、地震紀錄與最新的分析理論方法等)重新評估地震對廠址安全之衝擊。若地震危害重新評估的結果高於核能電廠原設計，後續須依再評估結果進行分析決定電廠需強化的結構、系統與組件(Structures, Systems, and Components, SSCs)項目，以確保核電廠對抗地震危害之能力。
本計畫係屬務實性(Pragmatic)任務並非研究性(Research)探討，目的係為協助台灣電力公司(Taiwan Power Company, TPC)因應我國核能管制機關－行政院原子能委員會(Atomic Energy Council)之要求，針對核能電廠執行「NTTF 2.1: Seismic」地震危害重新評估(Seismic Hazard Reevaluation)的部分，執行程序則依循美國「地震危害分析資深委員會(Senior Seismic Hazard Analysis Committee, SSHAC)」所訂定第3層級(以下簡稱SSHAC Level 3)之程序，並參考美國Diablo Canyon核能電廠(Diablo Canyon Power Plant, DCPP)執行地震危害重新評估的程序與考量的技術議題，建立適用於台電公司指定的4處目標工址的地震源特徵(Seismic Source Characterization, SSC)模型、地震動特徵(Ground Motion Characterization, GMC)模型與地震危害度分析輸入文件(Hazard Input Document, HID)，進行機率式地震危害度分析(Probabilistic Seismic Hazard Analysis, PSHA)並建立地震動反應譜(Ground Motion Response Spectrum, GMRS)之用，其中台電公司所指定之目標工址為台灣地區的4座核能電廠，而詳細的SSHAC Leve 3之程序說明可參考美國NRC核能法規NUREG-2117等相關文獻(Budnitz et al, 1997; Hanks et al., 2009; Coppersmith et al., 2010; NRC 2012)。本專案計畫書將說明本計畫如何依循SSHAC Level 3程序建置適用於各目標工址的地震源特徵(SSC)模型與地震動特徵(GMC)模型，後續各廠建立地震動反應譜GMRS的程序，包括進行機率式地震危害度分析與地盤反應分析等，將另案處理不在本計畫書的涵蓋範圍內。
In response to the 50.54(f) letter issued in March, 2012, an updated probabilistic seismic hazard analysis (PSHA) based on a Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 process (Budnitz et al., 1997; NRC 2012, NUREG 2117) is required to be conducted for all operating nuclear power plants in the United States. In Taiwan, the Atomic Energy Council (AEC) requested Taiwan Power Company (TPC) to reevaluate seismic hazard and review the seismic design basis of nuclear facilities in Taiwan based on the suggestions in NTTF 2.1: Seismic. As the result, TPC launched the “Seismic Reevaluation of Nuclear Facilities” Project executed by the National Center for Research on Earthquake Engineering (NCREE). A seismic hazard analysis will be performed for four nuclear power plants assigned by the Taiwan Power Company (TPC) by developing the Seismic Source Characterization (SSC) model and the Ground Motion Characterization (GMC) model as basic inputs to a site-specific probabilistic seismic hazard analysis (PSHA). SSC describes the future earthquake potential (e.g., magnitudes, locations and rates), and GMC describes the distribution of the ground motion as a function of magnitude, style of faulting, source-to-site geometry and site condition. For the seismic hazard analysis, both of these models will be developed following the guidelines of the Senior Seismic Hazard Analysis Committee (SSHAC) Level 3 process (Budnitz et al., 1997; NRC, 2012). The SSC model developed in this study is majorly specific to the region of the study sites with a 320-kilometer radius. The GMC model for the rock ground motions applicable to the study sites will be developed in this study in parallel. The GMC logic tree model will incorporate relevant empirical ground motion models as well as results from numerical simulations. The PSHA calculations and the development of surface response spectra considering site-specific site amplification are not part of this project and will be performed subsequent to the SSC and GMC SSHAC Level 3 studies by another project. The hazard results of four study sites evaluated by using the SSC and GMC models developed in this study will meet the requirements of SSHAC Level 3 methodology.
The objective of this study is to develop SSC and GMC models that capture the center, body and range (CBR) of the technically defensible interpretations (TDI) with SSHAC Level 3 methodology as described in NUREG 2117 (NRC, 2012) for use in PSHA for the study sites. TDI are defined as the development, assessment, and weighting of the scientifically justifiable and defensible interpretations of earth science and geotechnical data by appropriate experts in these fields using a structured process of evaluation and integration with full access to all available data. The purpose of this Project Plan is to describe how the SSHAC Level 3 process will be applied to develop the SSC and GMC models for the study sites.