Incorporation of Corrosion Mechanisms into a State-dependent Probabilistic Risk Assessment

The need for extending lifetimes of nuclear power plants and an increased interest in passive safety systems in Generation III+ and small modular reactors has brought a new focus in probabilistic risk assessment (PRA) to the treatment of passive systems, structures and components (SSCs). Although previously thought to play a lesser role in determining plant risk, research and industry experience have shown that degradation mechanisms of passive SSCs increase in importance with extended operating lifetimes.The case study analyzed in this research involves an accident scenario, in which steam generator tubes degraded by stress corrosion cracking rupture due to depressurization following a steam line break resulting from flow-accelerated corrosion. This study was performed by developing a state-dependent risk model. The model has the capability of using traditional PRA tools such as event trees and fault trees to determine a state-dependent core damage frequency. Unlike traditional PRA, which emphasizes active components, this methodology was used with a mechanistic aging model of a passive component. In addition, the model considers the effectiveness of the surveillance program and may be further developed to account for the possibility of component rejuvenation. Thus, the model allows for a time-dependent assessment of plant aging on risk.The application of the model to the Zion Nuclear Power Station has indicated that the maximum core damage frequency over the plant lifetime for a steam line break-induced tube rupture would occur in the 20th year of plant operation. The model also predicts the time progression of tube plugging and the frequency of spontaneous steam generator tube ruptures. Based on historical data, the rates of degradation calculated in the analysis appear to be reasonable, but somewhat conservative.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

masters

Discipline thesis:degree_discipline

Nuclear Engineering

Grantor dc:publisher

The Ohio State University

Year dc:date

2013

Author dc:creator

• Lewandowski, Radoslaw

Contributors dc:contributor

• Zhang, Jinsuo

• Nuclear Engineering
• Probabilistic Risk Assessment
• Stress Corrosion Cracking
• Flow-accelerated Corrosion
• Passive Components

Statement dc:rights

• unrestricted
• This thesis or dissertation is protected by copyright: all rights reserved. It may not be copied or redistributed beyond the terms of applicable copyright laws.

Language dc:language

English

Repository record dc:identifier

http://rave.ohiolink.edu/etdc/view?acc_num=osu1366171631

OAI identifier oai:identifier

oai:etd.ohiolink.edu:osu1366171631