- 學位論文
進步型沸水式反應器預期暫態未急停緩抑設施之性能分析
Anticipated Transient Without Scram Performance Analysis for Advanced Boiling Water Reactor
摘要
核四廠屬進步型沸水式核能電廠，其採用數位式儀控系統設計，考慮設計上可能存在軟體共因失效問題，導致反應器無法順利急停，產生預期暫態未急停（Anticipated Transient Without Scram, ATWS）事件，為確保反應器安全，並符合10CFR 50.62法規要求，電廠設計上裝設有緩抑ATWS事故之軟體與硬體設施，包括微調控制棒驅動機構插入、替代性控制棒插入、備用硼液控制系統自動啟動、爐內泵跳脫、爐內泵回退、飼水回退與禁止自動釋壓系統開啟等型態。本研究主要為對該等緩抑設施，利用熱水流暫態分析程式RETRAN-02進行相關極限ATWS事故之性能分析，確保反應器可達安全熱停機。 本研究對核四廠ATWS緩抑設施之性能分析，是以較受限之兩暫態作為分析個案，其一為主蒸汽隔離閥關斷ATWS暫態，其二為所有汽機旁通閥誤開啟ATWS暫態，分析是假設（i）反應器保護系統急停信號失效或急停信號產生但控制棒驅動機構本身無法動作及（ii）ATWS緩抑設施之微調控制棒驅動機構插入及替代性控制棒插入失效無法動作，亦即僅爐內泵跳脫備用硼液控制系統可用。本文同時進行爐心及系統參數之靈敏度分析，包括備用硼液控制系統啟動延遲、不同之爐心空泡負反應度係數、不同硼本領等對ATWS之短程與長程暫態反應效應。
並列摘要
Lungmen Plant is the Fourth Nuclear Power Plant owned by Taiwan Power Company, which belongs to ABWR（Advanced Boiling Water Reactor）type and employs the digital design in the instrumentation & control system. With the digital design, it is known that a kind of common cause failure due to the software error may exist. When this common cause failure occurs, the scram function may not be initiated due to failure of scram signal. As a consequence, the event of Anticipated Transient without Scram（ATWS）will occur. In order to assure that the plant can be safely shutdown and to comply with the requirement of 10CFR 50.62, various ATWS prevention mitigation features have been implemented in the design of Lungmen Plant, including Fine Motion Control Rod Drive（FMCRD）Run In, Alternate Rod Insertion（ARI）, Automatic Initiation of Standby Liquid Control System（SLCS）, Reactor Internal Pump Trip/ Runback, Feedwater Flow Runback, and Inhibition of Automatic Depressurization System. And the purpose of this study is to conduct the ATWS performance analysis considering those ATWS mitigation features, using the thermal-hydraulic analysis code RETRAN-02. Two limiting ATWS cases were studied :（i）Main Steam Isolation Valve Full Isolation and （ii）Inadvertent Opening of All Turbine Bypass Valves. The major assumptions for the analysis of these two cases are（i）reactor scram signals failure occurs or reactor scram signal is generated, but the control rod drive system fails, and（ii）the FMCRD Run In and ARI fail. With these assumptions, the only ATWS mitigation features available during the transient are reactor internal pump trip and initiation of Standby Liquid Control System. A sensitivity study was also performed in the study in order to investigate the various effects due to the variation of parameters to which the ATWS event are sensitive, including delay time of Standby Liquid Control System initiation, void reactivity coefficient, and boron worth, etc.