NUREG/CR-6850, Volume 1 - NRC

CONTENTS1 INTRODUCTION ....................................................................................................................1-11.1 Background .....................................................................................................................1-11.2 Programmatic Overview..................................................................................................1-21.2.1 Program Objectives .................................................................................................1-21.2.2 Program Approach ..................................................................................................1-31.2.3 Program Structure and Status .................................................................................1-41.3 Technical Process Overview...........................................................................................1-41.3.1 Technical Issue Resolution......................................................................................1-41.3.2 Peer Review ............................................................................................................1-51.3.3 Role of the Demonstration Studies..........................................................................1-61.4 Intended Audience and Needed Expertise......................................................................1-61.5 Estimate of Resources to Conduct a Fire PRA Using this Methodology.........................1-71.6 Report Structure..............................................................................................................1-91.7 References for Chapter 1................................................................................................1-92 OVERVIEW OF THE FIRE PRA METHODOLOGY ...............................................................2-12.1 General Scope ................................................................................................................2-12.2 Overview of the Fire PRA................................................................................................2-12.3 General Assumptions and Technical Positions...............................................................2-62.3.1 Component Selection and Fire-Induced Risk Model ...............................................2-62.3.1.1 General Component Selection Process...........................................................2-62.3.1.2 Post-Fire SSD Procedures...............................................................................2-72.3.1.3 Inclusion of Instrument Circuits........................................................................2-72.3.2 Circuit Selection and Analysis .................................................................................2-72.3.2.1 Proper Polarity Three-Phase Hot Shorts on AC Power Conductors................2-82.3.2.2 Circuit Selection and Analysis – System-Wide Safety Signals. .......................2-82.3.2.3 Multiple High-Impedance Faults ......................................................................2-82.3.3 Fire Frequency and Fire Modeling Assumptions .....................................................2-92.3.4 Low Likelihood Fires................................................................................................2-9vii