The maturity of Fire PRA
George Apostolakis
Head, Nuclear Risk Research Center
apostola@mit.edu
http://criepi.denken.or.jp/en/nrrc/index.html
Presented at theRegulatory Information Conference
Session W21: Reducing Risk Through Fire
Probabilistic Risk Assessment Research
March 13, 2019111

Evolution•

Late 70s, UCLA team develops the rudimentary
methodology




•
•

2004, 10 CFR 50.48(c) adopts NFPA Std 805
2005, NUREG/CR-6850
••It is applied to the Zion/Indian Point PRAs
Fire is found to be among the dominant riskcontributors
As a result, a plant modification is implemented atIndian Point

Many utilities switch to 10 CFR 50.48(c)Tremendous progress since the 70s
Currently: NRRC develops a fire PRA Guide

NUREG/CR-6850 is the starting point
Subsequent developments are included22

Maturity and Realism•

FPRAs for power operations are used by the NRCand industry to make risk-informed decisions
This use indicates that FPRA is credible and realistic
enough for decision making
FPRA is mature enough to provide useful input• I agree with Siu, Coyne, and Melly (2011) The concept of maturity addresses the relative state ofdevelopment of a technical discipline.
 Fire PRA is in an intermediate-to-late stage of maturity(albeit less mature than internal events PRA)

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NRRC Guide: Overview of Fire PRA Methodology
Phase A
Project Initiation
Internal Event PRM

PHASE-A

Task1: Modified PRM for Fire PRAInternal Event / Modifications / Refinement

Interconnected, Simultaneous Tasks with Iterations
Task2: Plant Boundary and Partitioning
Task3: Human Reliability Analysis
Task8: Fire Ignition
Frequencies

Task4: Fire PRA Equipment List
Task5: Circuit Analysis and Cable Identification

Task7: HEPs for
Initial Analysis

Task6: Qualitative Screening

Task9: Testing of the Model, Supporting Data and Full Compartment Burn Analysis

Phase-B

PRM: Plant Response Model44

NRRC Guide: Overview of Fire PRA Methodology
Phase B
Phase-A

PHASE-B
Task10: Main Control
Room Analysis

Task11: Structural
Steel Failure Analysis

Task12: MultiCompartment Analysis

Task13: Risk Significant Scenario Identifications

Detailed Analysis
Task15: Detailed
HRA

Task14: Fire
Modeling

Task16: Circuit Failure
Likelihood Analysis

Updates to Phase A Tasks
Task17: Need for
Detailed Analysis

Task18: Final Fire Risk
Quantification

Task19: Uncertainty &Sensitivity Analysis

Task20: Fire PRA
Documentation

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Technical Updates of NUREG/CR-6850
 Circuit Failure Mode Likelihood Analysis (Task-16)
 Includes the insights from NUREG/CR-7150 (JACQUE-FIRE)• Circuit Failure Modes• Duration Time of Hot Short• Probability of Hot Short USNRC endorsed NUREG/CR-7150 in 2017. The methods in NUREG/CR7150 supersede those in NUREG/CR-6850.

 Human Reliability Analysis
 Include insights from NUREG-1921 (Fire HRA Guidelines)• Identification of HFE（Task-3） and Initial HEPs（Task-7）• Detailed HEPs（Task-15） - Narrative approach of NRRC HRA Guide isreferenced

 Detailed Fire Modeling Use NUREG-2178 for the HRR of electric cabinets (RACHELL-FIRE)
 Modeling of Incipient fire detection

 Structural steel failure is newly added based on the concerns raisedin ASME/ANS Fire PRA standard
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Questions•

Is the current state of the art in FPRA too detailed
and resource intensive?

•Are there commensurate benefits?

•Could the guidance be simplified without losing thebenefits?

77With thanks to•••••

Mardy Kazarians, Kazarians and Associates
Koji Shirai, NRRC
Nathan Siu, NRC
John Stetkar, Technical Advisory Committee
Chairman, NRRC
Tsuyoshi Uchida, NRRC

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