ML19162A416

01_01 Introduction-Overview

ML19162A416
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Issue date:	06/13/2019
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NUREG/CR-6850 FIRE PRA METHODOLOGY Module 1 Internal Event, At-Power Probabilistic Risk Assessment Model for SNPP Introduction and Overview:

Scope and Structure of PRA/

Systems Analysis Module Nicholas Melly - Nuclear Regulatory Commission Fire PRA Workshop June 24, 2019 - June 28, 2019 Rockville, MD U.S. NRC HQ

What Well Cover in the Next Four Days An Overview The purpose of this presentation is to provide an Overview of the Module 1 - PRA/Systems Analysis Scope of this module relative to the overall methodology Which tasks fall under the scope of this module General structure of the each technical task in the documentation Quick introduction to each task covered by this module:

Objectives of each task Task input/output Task interfaces Fire PRA Workshop 2019, Rockville, MD Slide 2 Module 1: Internal Event, At-Power PRA Model for SNPP

Training Objectives Our intent:

To deliver practical implementation training To illustrate and demonstrate key aspects of the procedures We expect and want significant participant interaction Class size should allow for questions and discussion We will take questions about the methodology We cannot answer questions about a specific application We will moderate discussions and we will judge when the course must move on Fire PRA Workshop 2019, Rockville, MD Slide 3 Module 1: Internal Event, At-Power PRA Model for SNPP

Recall the Overall Fire PRA Structure Module 2 Covers the Blue Tasks TASK 1: Plant Boundary & TASK 2: Fire PRA Component Partitioning Selection TASK 3: Fire PRA Cable Selection SUPPORT TASK A: Plant Walk Downs TASK 4: Qualitative Screening TASK 5: Fire-Induced Risk Model TASK 6: Fire Ignition Frequencies SUPPORT TASK B: Fire PRA Database TASK 7A: Quantitative TASK 12A: Post-Fire HRA:

Screening - I Screening TASK 8: Scoping Fire Modeling Fire Analysis Module PRA/System Module TASK 7B: Quantitative Screening - II Circuits Module HRA Module B Fire Analysis and Fire Modeling Modules Fire PRA Workshop 2019, Rockville, MD Slide 4 Module 1: Internal Event, At-Power PRA Model for SNPP

Recall the Overall Fire PRA Structure (2)

Module 2 Covers the Blue Tasks B

Detailed Fire Scenario Analysis TASK 9: Detailed Circuit Failure Analysis TASK 11: Detailed Fire Modeling A. Single Compartment B. Multi-Compartment C. Main Control Room TASK 10: Circuit Failure Mode &

Likelihood Analysis TASK 12B: Post fire HRA:

TASK 13: Seismic-Fire TASK 14: Fire Risk Quantification Detailed & recovery Interactions Fire Analysis Module TASK 15: Uncertainty & PRA/System Module Sensitivity Analyses Circuits Module TASK 16: Fire PRA HRA Module Documentation Fire Analysis and Fire Modeling Modules Fire PRA Workshop 2019, Rockville, MD Slide 5 Module 1: Internal Event, At-Power PRA Model for SNPP

Each Technical Task Has a Common Structure as Presented in the Guidance Document

1. Purpose

2. Scope

3. Background information: General approach and assumptions

4. Interfaces: Input/output to other tasks, plant and other information needed, walk-downs

5. Procedure: Step-by-step instructions for conduct of the technical task

6. References Appendices: Technical bases, data, examples, special models or instructions, tools or databases Fire PRA Workshop 2019, Rockville, MD Slide 6 Module 1: Internal Event, At-Power PRA Model for SNPP

Scope of Module 1: PRA/Systems Analysis This module will cover all aspects of the plant systems accident response modeling, integration of human actions into the plant model, and quantification tasks Specific tasks covered are:

Task 2: Equipment Selection Task 4: Qualitative Screening Task 5: Fire-Induced Risk Model Task 7: Quantitative Screening Task 14: Fire Risk Quantification Task 15: Uncertainty and Sensitivity Analyses Task 16: Documentation Fire PRA Workshop 2019, Rockville, MD Slide 7 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Equipment Selection (1 of 2)

Module 1 Objective: To decide what subset of the plant equipment will be modeled in the FPRA FPRA equipment will be drawn from:

Equipment from the internal events PRA We do assume that an internal events PRA is available!

Equipment from the Post-Fire Safe Shutdown analysis e.g., The Appendix R analysis or the Nuclear Safety Analysis under NFPA-805 Other new equipment not in either of these analyses Fire PRA Workshop 2019, Rockville, MD Slide 8 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Equipment Selection (2 of 2)

Module 1 Many choices to be made in this task; many factors will influence these decisions Fire-induced failures that might cause an initiating event Mitigating equipment and operator actions Fire-induced failures that adversely impact credited equipment Fire-induced failures that could lead to inappropriate or unsafe operator actions Choices are important in part because selecting equipment implies a burden to Identify and Trace cables Cable selection is Task 3 (Module 2)

Fire PRA Workshop 2019, Rockville, MD Slide 9 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 4: Qualitative Screening (1 of 2)

Module 1 Objective: To identify fire compartments that can be screened out as insignificant risk contributors without quantitative analysis This is an Optional task You may choose to bypass this task, which means that all fire compartments will be treated quantitatively to some level of analysis (level may vary)

Fire PRA Workshop 2019, Rockville, MD Slide 10 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 4: Qualitative Screening (2 of 2)

Module 1 Qualitative screening criteria consider:

Trip initiators Presence of selected equipment Presence of selected cables Note that any compartment that is screened out in this step is reconsidered in the multi-compartment fire analysis as a potential source of multi-compartment fires See Module 3, Task 11c Fire PRA Workshop 2019, Rockville, MD Slide 11 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 5: Fire-Induced Risk Model Module 1 Objective: Construct the FPRA plant response model reflecting:

Functional relationships among selected equipment and operator actions Covers both CDF and LERF Begins with internal events model but more than just a tweak Adds fire unique equipment - Various reasons/sources May delete equipment not to be credited for fire Adds fire-specific equipment failure modes e.g., Spurious actuations (Task 9)

Adds fire-specific human failure events (Task 12)

Fire PRA Workshop 2019, Rockville, MD Slide 12 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 7: Quantitative Screening (1 of 2)

Module 1 Objective: To identify compartments that can be shown to be insignificant contributors to fire risk based on limited quantitative considerations This task is Optional Analyst may choose to retain all compartments for more detailed analysis Fire PRA Workshop 2019, Rockville, MD Slide 13 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 7: Quantitative Screening (2 of 2)

Module 1 Screening may be performed in stages of increasing complexity Consideration is given to:

Fire ignition frequency Screening of specific fire sources as non-threatening (no spread, no damage)

Impact of fire-induced equipment and cable failures Conditional core damage probability (CCDP)

A word of caution: Quantitative screening criteria should consider the PRA standard and Reg. Guide 1.200 6850/1011989 criteria are obsolete, but approach is unchanged Fire PRA Workshop 2019, Rockville, MD Slide 14 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 14: Fire Risk Quantification Module 1 Objective: To quantify fire-induced CDF and LERF Covered in limited detail Relatively straight-forward roll-up for fire scenarios considering:

Ignition frequency Scenario-specific equipment and cable damage Equipment failure modes and likelihoods Credit for fire mitigation (detection and suppression)

Fire-specific HEPs Quantification of the FPRA plant response model Fire PRA Workshop 2019, Rockville, MD Slide 15 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 15: Uncertainty and Sensitivity Module 1 Objective: Provide a process for identifying and quantifying uncertainties in the FPRA and for identifying sensitivity analysis cases Covered in limited detail Guidance is based on potential strategies that might be taken, but choices are largely left to the analyst e.g., What uncertainties will be characterized as distributions and propagated through the model?

Fire PRA Workshop 2019, Rockville, MD Slide 16 Module 1: Internal Event, At-Power PRA Model for SNPP

Any questions before we move on?

Fire PRA Workshop 2019, Rockville, MD Slide 17 Module 1: Internal Event, At-Power PRA Model for SNPP