위험 분석 - 원자력 발전소 사고 시나리오 (Risk Analysis of Nuclear Power Plants during Accident Scenarios)
본 보고서는 원자력 발전소들의 신뢰성 개선, 안정성 유지 및 계속운전을 위한 솔루션부터 위험 평가 전략을 개발하는 것까지의 기술적 근거를 제공합니다.
This report documents the activities performed by Idaho National Laboratory (INL) during fiscal year (FY) 2022 for the U.S. Department of Energy (DOE) Light Water Reactor Sustainability (LWRS) Program, Risk Informed Systems Analysis (RISA) Pathway, digital instrumentation and control (DI&C) risk assessment project [1], [2], [3]. The LWRS program, sponsored by the U.S. DOE and coordinated through a variety of mechanisms and interactions with industry, vendors, suppliers, regulatory agencies, and other industry research and development (R&D) organizations, conducts research to develop technologies and other solutions to improve economics and reliability, sustain safety, and extend the operation of nation's fleet of nuclear power plants (NPPs). The LWRS program has two objectives to maintain the long-term operations of the existing fleet: (1) to provide science- and technology-based solutions to industry to implement technology to exceed the performance of the current business model and (2) to manage the aging of systems, structures, and components (SSCs) so NPP lifetime can be extended, and the plants can continue to operate safely, efficiently, and economically. As one of the LWRS program’s R&D pathways, the RISA Pathway aims to support decision-making related to economics, reliability, and safety providing integrated plant systems analysis solutions through collaborative demonstrations to enhance economic competitiveness of the operating fleet. The goal of the RISA Pathway is to conduct R&D to optimize safety margins and minimize uncertainties to achieve economic efficiencies while maintaining high levels of safety. This is accomplished in two ways: (1) by providing scientific basis to better represent safety margins and factors that contribute to cost and safety; and (2) by developing new technologies that reduce operating costs. One of the research efforts under the RISA Pathway is the DI&C Risk Assessment project, which was initiated in FY 2019 to develop a risk assessment strategy for delivering a strong technical basis to support effective, licensable, and secure DI&C technologies for digital upgrades and designs [1]. An integrated risk assessment framework for the DI&C systems was proposed for this strategy which aims to: • Provide a best-estimate, risk informed capability to quantitatively and accurately estimate the safety margin obtained from plant modernization, especially for the high safety-significant safety-related (HSSSR) DI&C systems • Support and supplement existing advanced risk informed DI&C design guides by providing quantitative risk information and evidence • Offer a capability of design architecture evaluation of various DI&C systems to support system design decisions and diversity and redundancy applications • Assure the long-term safety and reliability of HSSSR DI&C systems • Reduce uncertainty in costs and support integration of DI&C systems at NPPs. The proposed risk assessment framework for DI&C systems is shown in Figure 1. In this framework, a redundancy-guided systems-theoretic method for hazard analysis (RESHA) was developed for HSSSR DI&C systems to support I&C designers and engineers to address both hardware and software CCFs and qualitatively analyze their effects on system availability [4] [5]. It also provides a technical basis for implementing reliability and consequence analyses of unexpected software failures, and supporting the optimization of defense-in-depth applications in a cost-efficient way. The framework integrates STPA [6], FTA, and HAZCADS [7] methodologies to effectively identify software CCFs in complex systems with multiple levels of redundancy. More specifically, STPA is reframed in a redundancy-guided way, such as (1) depicting a redundant and diverse system via a detailed representation; (2) refining different redundancy levels based on the structure of DI&C systems; (3) constructing a redundancy-guided multilayer control structure; and (4) identifying potential CCFs in different redundancy levels. This approach has been demonstrated and applied for the hazard analysis of a four-division digital RTS [4] and a four-division digital ESFAS [5]. These efforts are described in the LWRS-RISA milestone reports for FY-20 [2] and FY-21 [3]. The second part in risk analysis is the reliability analysis which includes tasks of (1) quantifying the probability of basic events of the integrated FT from the hazard analysis; (2) estimating the probability of consequences resulting from digital system failures. In the proposed framework, two methods have been developed: the Bayesian and human-reliability-analysis-aided method for the reliability analysis of software (BAHAMAS) [8] and orthogonal-defect classification for assessing software reliability (ORCAS). BAHAMAS is applicable in situations with limited data conditions (e.g., early stage of system development) and ORCAS is applicable for analyses when significant amount of data is available (e.g., fully-developed system that underwent verification and validation or a system with significant length of operating experience). Finally, the consequence analysis is conducted to quantitatively evaluate the impact of digital failures on plant overall risks by assessing affected behaviors and responses. Some digital-based failures may initiate an event or scenario that was not analyzed before (e.g., a failure mode only applicable to a digital system), which could challenge the plant safety. Figure 1. The flexible and modularized structure of the proposed risk assessment framework for HSSSR DI&C systems. This report outlines R&D focused on methodology improvements of software CCF modeling and estimation and introduces additional innovative approaches to risk assessment of DI&C systems such as prevention analysis and importance analysis to enable a comparative assessment of various DI&C design architectures. The remaining sections of the report are organized as follows: Section 2 describes the event tree (ET) and fault tree (FT) structures for diverse and redundant DI&C systems which are analyzed in this report. Section 3 introduces the software CCF modeling approach developed for diverse and redundant DI&C systems. Section 4 presents the results of sensitivity and importance analyses conducted for different designs of RTS and ESFAS. Section 5 discusses the application of Top Event Prevention Analysis (TEPA) to a simplified RTS-FT model. Section 6 summarizes the work of a FY-22 summer internship completed at INL to develop a preliminary model for quantifying software CCFs using Dual Error Propagation Method (DEPM). Section 5 outlines conclusions and future work of this project.
국내외 전문자료
2023-08-31
국내외 전문자료위험 분석 - 원자력 발전소 사고 시나리오 (Risk Analysis of Nuclear Power Plants during Accident Scenarios)
- 국가미국
- 발행기관Idaho National Laboratory (아이다호 국립연구소)
- 원본링크https://www.osti.gov/biblio/1986002
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