NUREG-1824 EPRI 1011999

Final Report

Verification and Validation

of Selected Fire Models for

Nuclear Power Plant

Applications

Volume 1:

Main Report

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research

Washington, DC 20555-0001

~U.S.NICv* qu' ATp.-u 1 dh ýcomlK

Electric Power Research Institute

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Palo Alto, CA 94303

~ ~ ELECTRIC POWER

RESEARCH INSTITUTE
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Verification & Validation of Selected

Fire Models for Nuclear Power Plant

Applications

Volume 1: Main Report

NUREG-1 824 EPRI 1011999

Final Report

.May 2007

U.S. Nuclear Regulatory Commission

Office of Nuclear Regulatory Research (RES)

Two White Flint North, 11545 Rockville Pike

Rockville, MID 20852-2738

U.S. NRC-RES Project Manager

M. H. Salley

Electric Power Research Institute (EPRI)

3420 Hillview Avenue

Palo Alto, CA 94303

EPRI Project Manager

R.P. Kassawara
DISCLAIMER OF WARRANTIES AND LIMITATION OF LIABILITIES

THIS DOCUMENT WAS PREPARED BY THE ORGANIZATION(S) NAMED BELOW AS AN

ACCOUNT OF WORK SPONSORED OR COSPONSORED BY THE ELECTRIC POWER

RESEARCH INSTITUTE, INC. (EPRI). NEITHER EPRI NOR ANY MEMBER OF EPRI, ANY

COSPONSOR, THE ORGANIZATION(S) BELOW, OR ANY PERSON ACTING ON BEHALF

OF ANY OF THEM:

(A) MAKES ANY WARRANTY OR REPRESENTATION WHATSOEVER, EXPRESS OR

IMPLIED, (1) WITH RESPECT TO THE USE OF ANY INFORMATION, APPARATUS,

METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED IN THIS DOCUMENT, INCLUDING

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(B) ASSUMES RESPONSIBILITY FOR ANY DAMAGES OR OTHER LIABILITY

WHATSOEVER (INCLUDING ANY CONSEQUENTIAL DAMAGES, EVEN IF EPRI OR ANY

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DAMAGES) RESULTING FROM YOUR SELECTION OR USE OF THIS DOCUMENT OR

ANY INFORMATION, APPARATUS, METHOD, PROCESS, OR SIMILAR ITEM DISCLOSED

IN THIS DOCUMENT.

ORGANIZATION(S) THAT PREPARED THIS DOCUMENT:

U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research

Science Applications International Corporation

National Institute of Standards and Technology

NOTE

For further information about EPRI, call the EPRI Customer Assistance Center at

800.313.3774 or

e-mail askepn@epn.com.

Electric Power Research Institute, EPRI, and TOGETHER... .SHAPING THE FUTURE OF

ELECTRICITY are registered service marks of the Electric Power Research Institute, Inc.
CITATIONS

This report was prepared by:

U.S. Nuclear Regulatory Commission,

Office of Nuclear Regulatory Research (RES)

Two White Flint North, 11545 Rockville Pike

Rockville, MD 20852-273 8

Principal Investigators:

K. Hill

J. Dreisbach

National Institute of Standards and Technology

Building Fire Research Laboratory (BFRL)

100 Bureau Drive, Stop 8 600

Gaithersburg, MD 20899-8600

Electric Power Research Institute (EPRI)

3420 Hillview Avenue

Palo Alto, CA 94303

Science Applications International Corp (SAIC)

4920 El Camino Real

Los Altos, CA 94022

Principal Investigators:

F. Joglar

B. Najafi

Principal Investigators:

K McGrattan

R. Peacock

A. Hamins

Volume 1, Main Report: B. Najafi, F. Joglar, J. Dreisbach

Volume 2, Experimental Uncertainty: A. Hamins, K. McGrattan

Volume 3, FDT5 : J. Dreisbach, K. Hill

Volume 4, FIVE-Rev 1: F. Joglar

Volume 5, CFAST: R. Peacock, P. Reneke (NIST)

Volume 6, MAGIC: F. Joglar, B. Guatier (EdF), L. Gay (EdF), J. Texeraud (EdF)

Volume 7, FDS: K. McGrattan

This report describes research sponsored jointly by U.S. Nuclear Regulatory Commission, Office

of Nuclear Regulatory Research (RES) and Electric Power Research Institute (EPRI).

The report is a corporate document that should be cited in the literature in the following manner:

Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications,

Volume 1: Main Report, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory

Research (RES), Rockville, MD, 2007, and Electric Power Research Institute (EPRI), Palo Alto,

CA, NUREG- 1824 and EPRI 10 11999.

iii

ABSTRACT

There is a movement to introduce risk-informed and performance-based analyses into fire protection

engineering practice, both domestically and worldwide. This movement exists in the general

fire protection community, as well as the nuclear power plant (NPP) fire protection community.

The U.S. Nuclear Regulatory Commission (NRC) has used risk-informed insights as part of its

regulatory decision making since the 1990's.

In 2002, the National Fire Protection Association (NFPA) developed NFPA 805, PerformanceBased Standard for Fire Protection for Light- Water Reactor Electric Generating Plants,

2001 Edition. In July 2004, the NRC amended its fire protection requirements in Title 10,

Section 50.48, of the Code of Federal Regulations (10 CFR 50.48) to permit existing reactor

licensees to voluntarily adopt fire protection requirements contained in NFPA 805 as an alternative

to the existing deterministic fire protection requirements. In addition, the NPP fire protection

community has been using risk-informed, performance-based (RI/PB) approaches and insights to

support fire protection decision-making in general.

One key tool needed to fturther the use of RI/PB3 fire protection is the availability of verified and

validated fire models that can reliably predict the consequences of fires. Section 2.4.1.2 of

NFPA 805 requires that only fire models acceptable to the Authority Having Jurisdiction (AHJ)

shall be used in fire modeling calculations. Furthermore, Sections 2.4.1.2.2 and 2.4.1.2.3 of

NEPA 805 state that fire models shall only be applied within the limitations of the given model,

and shall be verified and validated.

This report is the first effort to document the verification and validation (V&V) of five fire models

that are commonly used in NPP applications. The project was performed in accordance with the

guidelines that the American Society for Testing and Materials (ASTM) set forth in ASTM E 1355,

Standard Guide for Evaluating the Predictive Capability of Deterministic Fire Models.

The results of this V&V are reported in the form of ranges of accuracies for the fire model

predictions.

v

FOREWORD

Fire modeling and fire dynamics calculations are used in a number of fire hazards analysis (FHA) studies and

documents, including fire risk analysis (FRA) calculations; compliance with and exemptions to the regulatory

requirements for fire protection in 10 CFR Part 50; the Significance Determination Process (SDP) used in the

inspection program conducted by the U.S. Nuclear Regulatory Commission (NRC); and, most recently, the

risk-informed performance-based (RI/PB) voluntary fire protection licensing basis established under

10 CFR 50.48(c). The RI/PB method is based on the National Fire Protection Association (NFPA)

Standard 805, Perforinance-B ased Standard for Fire Protection for Light- Water Reactor Generating Plants.

The seven volumes of this NUREG-series report provide technical documentation concerning the predictive

capabilities of a specific set of fire dynamics calculation tools and fire models for the analysis of fire hazards in

postulated nuclear power plant (NPP) scenarios. Under a joint memorandum of understanding (MOU), the NRC

Office of Nuclear Regulatory Research (RES) and the Electric Power Research Institute (EPRI) agreed to develop

this technical document for NPP application of these fire modeling tools. The objectives of this agreement

include creating a library of typical NPP fire scenarios and providing information on the ability of specific fire models

to predict the consequences of those typical NPP fire scenarios. To meet these objectives, RES and EPRI initiated

this collaborative project to provide an evaluation, in the form of verification and validation (V&V), for a set of five

commonly available fire modeling tools.

The road map for this project was derived from NEPA 805 and the American Society for Testing and Materials

(ASTM) Standard E 1355, Standard Guide for Evaluating the Predictive Capability of Deterministic Fire

Models. These industry standards form the methodology and process used to perform this study. Technical

review of fire models is also necessary to ensure that those using the models can accurately assess the adequacy of

the scientific and technical bases for the models, select models that are appropriate for a desired use, and understand

the levels of confidence that can be attributed to the results predicted by the models. This work was performed

using state-of-the-art fire dynamics calculation methods/models and the most applicable fire test data. Future

improvements in the fire dynamics calculation methods/models and additional fire test data may impact the results

presented in the seven volumes of this report.

This document does not constitute regulatory requirements, and NRC participation in this study neither

constitutes nor implies regulatory approval of applications based on the analysis contained in this text

The analyses documented in this report represent the combined efforts of individuals from RES and EPRI.

Both organizations provided specialists in the use of fire models and other FHA tools to support this work.

The results from this combined effort do not constitute either a regulatory position or regulatory guidance.

Rather, these results are intended to provide technical analysis of the predictive capabilities of five fire

dynamic calculation tools, and they may also help to identify areas where fuirther research and analysis are needed.

Brian W. Sheron, Director

Office of Nuclear Regulatory Research

U.S. Nuclear Regulatory Commission

Vii

CONTENTS

1 INTRODUCTION .................................................................................... 1-1

1.1 Background ..................................................................................... 1-1

1.2 Programmatic Overview ....................................................................... 1-1

1.2.1 Objectives.............................................................................. 1-2

1.2.2 Approach............................................................................... 1-3

1.3 Report Structure................................................................................ 1-3

2 TECHNICAL APPROACH .......................................................................... 2-1

2.1 Library of Nuclear Power Plant Fire Scenarios.............................................. 2-4

2.1.1 Switchgear Room ..................................................................... 2-4

2.1.2 Cable Spreading Room............................................................... 2-5

2.1.3 Main Control Room................................................................... 2-6

2.1.4 Pump Room........................................................................... 2-7

2.1.5 Turbine Building....................................................................... 2-8

2.1.6 Multi-Compartment Corridor ......................................................... 2-9

2.1.7 Multi-Level Building ................................................................. 2-10

2.1.8 Containment Building (PWR) ....................................................... 2-11

2.1.9 Battery Room ........................................................................ 2-12

2.1.10 Diesel Generator Room ............................................................. 2-12

2.1.11 Computer or Relay Room........................................................... 2-13

2.1.12 Outdoors .............................................................................. 2-13

2.2 Fire Models .................................................................................... 2-13

2.2.1 Libraries of Engineering Calculations: FOTS and FIVE-Rev! ................... 2-13

2.2.2 Two-Zone Fire Models: CFAST and MAGIC ..................................... 2-14

2.2.3 Field Fire Model: FOS.............................................................. 2-15

2.3 Experimental Data ............................................................................ 2-15

2.3.1 Factory Mutual & Sandia National Laboratories (FM/SNL) Test Series ........ 2-15

2.3.2 The National Bureau of Standards (NBS) Test Series ........................... 2-16

ix
2.3.3 The International Collaborative Fire Model Project (ICFMP) Benchmark

Exercise Test Series ...................... .............. 21

2.4 Selection of Fire Modeling Parameters ..................................................... 2-18

2.5 Quantitative Validation ....................................................................... 2-22

2.6 Reporting and Applicability of the Validation Results...................................... 2-25

2.6.1 Applicability of the V&V Results.................................................... 2-25

2.6.2 Characterization of Fire Model Predictions Based on Validation Results......2-32

2.6.3 Uncertainty Analysis................................................................. 2-34

3 RESULTS AND CONCLUSIONS................................................................... 3-11

3.1 Results .......................................................................................... 3-1

3.1.1 Validation .............................................................................. 3-1

3.1.2 Verification............................................................................. 3-4

3.2 Summary........................................................................................ 3-4

3.3 Conclusions..................................................................................... 3-5

4 REFERENCES ...................................................................................... 4-1

X
FIGURES

Figure 2-1: Overview of the Approach for V&V Study of Selected Fire Models

for Nuclear Power Plant Applications ............................................................... 2-3

Figure 2-2: Switchgear Room Fire Scenario ....................................................... 2-5

Figure 2-3: Cable Spreading Room Fire Scenario................................................. 2-6

Figure 2-4: Main Control Room Fire Scenario ..................................................... 2-7

Figure 2-5: Pump Room Fire Scenario ............................................................. 2-8

Figure 2-6: Turbine Building Fire Scenario......................................................... 2-9

Figure 2-7: Multi-Compartment Corridor Fire Scenario .......................................... 2-10

Figure 2-8: Multi-Level Building Fire Scenario.................................................... 2-11

Figure 2-9: PWR Containment Building Scenario................................................ 2-12

Figure 2-10: Scatter Plots Depicting Validation Results in and Out of the Range of

Combined Uncertainty............................................................................... 2-34

xi

TABLES

Table 2-1: FDTS and Five-Revi Models for the Fire Scenario Attributes

Selected for this V&V Study......................................................................... 2-14

Table 2-2: Fire Modeling Attributes as Outputs................................................... 2-21

Table 2-3: Summary of the Fire Tests Used for Validation Against Typical NPP Fire

Scenario Attributes................................................................................... 2-23

Table 2-4: List of Selected Normalized Parameters for Application

of the Validation Results to NPP Fire Scenarios................................................... 2-26

Table 2-5: Summary of the Fire Experiments in Terms of Commonly Used Metrics .......... 2-31

Table 3-1: Results of the Validation & Verification of the Selected Fire Models for

Nuclear Power Plant Fire Modeling Applications .................. ................................ 3-2

xiii

REPORT SUMMARY

This report documents the verification and validation (V&V) of five selected fire models

commonly used in support of risk-informed and performance-based (RI/PB3) fire protection

at nuclear power plants (NPPs).

Background

Since the 1990s, when it became the policy of the NRC to use risk-informed methods to make

regulatory decisions where possible, the nuclear power industry has been moving from prescriptive

rules and practices toward the use of risk information to supplement decision-making. Several

initiatives have furthered this transition in the area of fire protection. In 2001, the National Fire

Protection Association (NFPA) completed the development of NFPA Standard 805,

Performance-Based Standard for Fire Protection for Light- Water Reactor Electric Generating

Plants, 2001 Edition. Effective July 16, 2004, the NRC amended its fire protection requirements

in Title 10, Section 50.48(c), of the Code of Federal Regulations [10 CFR 50.48(c)] to permit

existing reactor licensees to voluntarily adopt fire protection requirements contained in NFPA

805 as an alternative to the existing deterministic fire protection requirements. RI/PB3 fire

protection often relies on fire modeling for determining the consequence of fires. NFPA 805

requires that the "fire models shall be verified and validated," and "only fire models that are

acceptable to the Authority Having Jurisdiction (AHJ) shall be used in fire modeling

calculations."

Objectives

" To perform V&V studies of selected fire models using a consistent methodology (ASTM I

1335)

" To investigate the specific fire modeling issue of interest to NPP fire protection applications

" To quantify fire model predictive capabilities to the extent that can be supported by

comparison with selected and available experimental data.

Approach

This project team performed V&V studies on five selected models: (1) NRC's NUREG- 1805

Fire Dynamics Tools (FDTS), (2) EPRI's Fire-Induced Vulnerability Evaluation Revision 1

(Fl VE-Revl), (3) National Institute of Standards and Technology's (NIST) Consolidated Model

of Fire Growth and Smoke Transport (CFAST), (4) Electricit6 de France's (EdF) MAGIC, and

(5) NIST's Fire Dynamics Simulator (FDS). The team based these studies on the guidelines of

the ASTM E 1355, Standard Guide for Evaluating the Predictive Capability of Deterministic

Fire Models. The scope of these V&V studies was limited to the capabilities of the selected fire

models and did not cover certain potential fire scenarios that fall outside the capabilities of these

fire models.

xv
Results

The results of this study are presented in the form of relative differences between fire model

predictions and experimental data for fire modeling attributes such as plume temperature that are

important to NPP fire modeling applications. While the relative differences sometimes show

agreement, they also show both under-prediction and over-prediction in some circumstances.

These relative differences are affected by the capabilities of the models, the availability of

accurate applicable experimental data, and the experimental uncertainty of these data. The

project team used the relative differences, in combination with some engineering judgment as to

the appropriateness of the model and the agreement between model and experiment, to produce a

graded characterization of each fire model's capability to predict attributes important to NPP fire

modeling applications.

This report does not provide relative differences for all known fire scenarios in NPP applications.

This incompleteness is attributable to a combination of model capability and lack of relevant

experimental data. The first problem can be addressed by improving the fire models, while the

second problem calls for more applicable fire experiments.

EPRI Perspective

The use of fire models to support fire protection decision-making requires a good understanding

of their limitations and predictive capabilities. While this report makes considerable progress

toward this goal, it also points to ranges of accuracies in the predictive capability of these fire

models that could limit their use in fire modeling applications. Use of these fire models presents

challenges that should be addressed if the fire protection community is to realize the full benefit

of fire modeling and performance-based fire protection. Persisting problems require both shortterm and long-term solutions. In the short-term, users need to be educated on how the results of

this work may affect known applications of fire modeling, perhaps through pilot application of

the findings of this report and documentation of the resulting lessons learned. In the long-term,

additional work on improving the models and performing additional experiments should be

considered.

Keywords

Fire Fire Modeling

Verification and Validation (V&V) Performance-Based

Risk-Informed Regulation Fire Hazard Analysis (FHA)

Fire Safety Fire Protection

Nuclear Power Plant Fire Probabilistic Risk Assessment (PRA)

Fire Probabilistic Safety Assessment (PSA)

xvi
PREFACE

This report is presented in seven volumes. Volume 1, the Main Report, provides general

background information, programmatic and technical overviews, and project insights and

conclusions. Volume 2 quantifies the uncertainty of the experiments used in the V&V study of

the five fire models considered in this study. Volumes 3 through 7 provide detailed discussions

of the verification and validation (V&V) of the following fire models:

Volume 3 Fire Dynamics Tools (FDTS)

Volume 4 Fire-Induced Vulnerability Evaluation, Revision 1 (FIVE-Revl)

Volume 5 Consolidated Model of Fire Growth and Smoke Transport (CFAST)

Volume 6 MAGIC

Volume 7 Fire Dynamics Simulator (FDS)

xvii

ACKNOWLEDGMENTS

The work documented in this report benefited from contributions and considerable technical

support from several organizations.

The verification and validation (V&V) studies for FDTS (Volume 3), CFAST (Volume 5), and

FDS (Volume 7) were conducted in collaboration with the U.S. Department of Commerce,

National Institute of Standards and Technology (NIST), Building and Fire Research Laboratory

(BFRL). Since the inception of this project in 1999, the NRC has collaborated with NIST

through an interagency memorandum of understanding (MOU) and conducted research to provide

the necessary technical data and tools to support the use of fire models in nuclear power plant

fire hazard analysis (FHA).

We appreciate the efforts of Doug Carpenter and Rob Schmidt of Combustion Science

Engineers, Inc. for their comments and contributions to Volume 3.

In addition, we acknowledge and appreciate the extensive contributions of Electricit6 de France

(EdF) in preparing Volume 6 for MAGIC.

We thank Drs. Charles Hagwood and Matthew Bundy of NIST for the many helpful discussions

regarding Volume 2.

We also appreciate the efforts of organizations participating in the International Collaborative

Fire Model Project (ICFMP) to Evaluate Fire Models for Nuclear Power Plant Applications,

which provided experimental data, problem specifications, and insights and peer comment for

the international fire model benchmarking and validation exercises, and jointly prepared the

panel reports used and referred to in this study. We specifically appreciate the efforts of the

Building Research Establishment (BRE) and the Nuclear Installations Inspectorate in the United

Kingdom, which provided leadership for ICFMP Benchmark Exercise (BE) #2, as well as

Gesellschaft Mur Anlagen-und Reaktorsicherheit (GRS) and Institut ffur Baustoffe, Massivbau und

Brandschutz (iBMB) in Germany, which provided leadership and valuable experimental data for

ICEMP BE #4 and BE #5. In particular, ICFMP BE #2 was led by Stewart Miles at BRE; ICFMP

BE #4 was led by Walter Klein-Hessling and Marina Rowekamp at GRS, and R. Dobbernack and Olaf

Riese at iBMB; and ICFMP BE #5 was led by Olaf Riese and D. Hosser at iBMB, and Marina

Rowekamp at GRS. Simo Hostikka of Vii', Finland also assisted with ICFMP BE#2 by

providing pictures, tests reports, and answered various technical questions of those experiments.

We acknowledge and sincerely appreciate all of their efforts.

We greatly appreciate Paula Garrity, Technical Editor for the Office of Nuclear Regulatory

Research, and Linda Stevenson, agency Publications Specialist, for providing editorial and

publishing support for this report. Lionel Watkins and Felix Gonzalez developed the graphics

xix
for Volume 1. We also'greatly appreciate Dariusz Szwar'c and Alan Kouchinsky for their

assistance finalizing this report.

We wish to acknowledge the team of peer reviewers who reviewed the initial draft of this report

and provided valuable comments. The peer reviewers were Dr. Craig Beyler and Mr. Phil

DiNenno of Hughes Associates, Inc., and Dr. James Quintiere of the University of Maryland.

Finally, we would like to thank the internal and external stakeholders who took the time to

provide comments and suggestions on the initial draft of this report when it was published in the

Federal Register (71 FR 5088) on January 31, 2006. Those stakeholders who commented are

listed and acknowledged below.

Janice Bardi, ASTM International

Moonhak Jee, Korea Electric Power Research Institute

U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation Fire Protection

Branch

J. Greg Sanchez, New York City Transit

David Showalter, Fluent, Inc.

Douglas Carpenter, Combustion Science & Engineering, Inc.

Nathan Siu, U.S. Nuclear Regulatory Commission, Office of Nuclear Regulatory Research

Clarence Worrell, Pacific Gas & Electric

xx
LIST OF ACRONYMS

AGA

AHJ

ASME

ASTM

BE

BFRL

BRE

BWR

CDF

CFAST

CFD

CFR

CSR

EdF

EPRI

FDS

FDTs

FHA

FIVE-RevI

FM/SNL

FPA

FRA

GRS

HGL

HRR

American Gas Association

Authority Having Jurisdiction

American Society of Mechanical Engineers

American Society for Testing and Materials

Benchmark Exercise

Building and Fire Research Laboratory

Building Research Establishment

Boiling-Water Reactor

Core Damage Frequency

Consolidated Fire Growth and Smoke Transport Model

Computational Fluid Dynamics

Code of Federal Regulations

Cable Spreading Room

Electricit6 de France

Electric Power Research Institute

Fire Dynamics Simulator

Fire Dynamics Tools (NUREG- 1805)

Fire Hazard Analysis

Fire-Induced Vulnerability Evaluation, Revision 1

Factory Mutual & Sandia National Laboratories

Foote, Pagni, and Alvares

Fire Risk Analysis

Gesellschaft flier Anlagen-und Reaktorsicherheit (Germany)

Hot Gas Layer

Heat Release Rate

xxi
IAFSS International Association of Fire Safety Science

iBMB Institut fiir Baustoffe, Massivbau und Brandschutz;

ICFMP International Collaborative Fire Model Project

IEEE Institute of Electrical and Electronics Engineers

IPEEE Individual Plant Examination of External Events

MCC Motor Control Center

MCR Main Control Room

MQH McCaffrey, Quintiere, and Harkleroad

MOU Memorandum of Understanding

NBS National Bureau of Standards (now NIST)

NFPA National Fire Protection Association

NIST National Institute of Standards and Technology

NPP Nuclear Power Plant

NRC U.S. Nuclear Regulatory Commission

NRR Office of Nuclear Reactor Regulation (NRC)

PMMA Polymethyl-methacrylate

PRA Probabilistic Risk Assessment

PW~R Pressurized-Water Reactor

RCP Reactor Coolant Pump

RES Office of Nuclear Regulatory Research (NRC)

RI/PB Risk-Informed, Performance-Based

SBDG Stand-By Diesel Generator

SDP Significance Determination Process

SFPE Society of Fire Protection Engineers

SNL Sandia National Laboratory

SWGR Switchgear Room

V&V Verification & Validation

xxii
INTRODUCTION

1.1 Background

Over the past decade, there has been a considerable movement in the nuclear power industry

to transition from prescriptive rules and practices toward the use of risk information to supplement

decision-making. In the area of fire protection, this movement is evidenced by numerous initiatives

by the U.S. Nuclear Regulatory Commission (NRC) and the nuclear power generation

community worldwide.

In 2001, the National Fire Protection Association (NFPA) completed its development of

NFPA 805, Performance-Based Standard for Fire Protection for Light- Water Reactor

Electric Generating Plants, 2001 Edition [1]. Effective July 16, 2004, the NRC amended

its fire protection requirements in Title 10, Section 50.48(c), of the Code of Federal Regulations

[10 CFR 5 0.48(c)] to permit existing reactor licensees to voluntarily adopt fire protection

requirements contained in NFPA 805 as an alternative to the existing deterministic fire protection

requirements [2].

Risk-informed, performance-based (RI/PB) fire protection often relies on fire modeling to

determine the consequences of fires. NFPA 805 states that "fire models shall be verified and

validated," and "only fire models that are acceptable to the authority having jurisdiction (AHJ)

shall be used in fire modeling calculations."

1.2 Programmatic Overview

Under a Memorandum of Understanding [3], the NRC's Office of Nuclear Regulatory Research

(RES) and the Electric Power Research Institute (EPRI) initiated a collaborative project for

verification and validation (V&V) of five selected fire models to support RI/PB fire protection and

implementation of the voluntary fire protection rule that adopts NFPA 805 as an RI/PB alternative.

This V&V effort may also serve to increase the confidence of reviewers who evaluate fire models

that are used in other programs, such as the Fire Protection Significance Determination Process (SDP).

This collaboration brings together the combined information and knowledge generated in this

area by the NRC and EPRI fire research programs. The National Institute of Standards and

Technology (NIST) was also an important partner in this project. NIST provided extensive modeling

and experimentation expertise. This effort also recognizes the considerable knowledge that resides in

the fire science community in general, and attempts to use that knowledge, particularly within the

context of the fire models being evaluated. This report is the direct result of this collaboration

between RES, EPRI, and NIST.

1-1
Introduction

1.2.1 Objectives

The purpose of this report is to describe an evaluation of the predictive capabilities of certain

fire models for applications specific to nuclear power plants (NPPs). These models may be used

to demonstrate compliance with the requirements of 10 CFR 50.48(c) [2] and the referenced

NFPA standard, NFPA 805 [1].

Engineering analyses and methods that are applied to demonstrate compliance with the

performance criteria in NFPA 805 need the requisite degree of defensible technical justification,

as dictated by the scope and complexity of the specific application. These analyses should be

performed by qualified analysts and should include any necessary V&V of analytical methods

relevant to the specific application.

Section 2.4.1.2 of NFPA 805 states that only fire models acceptable to the AHJ shall be used in

fire modeling calculations. Further, Sections 2.4.1.2.2 and 2.4.1.2.3 of NFPA 805 state that fire

models shall only be applied within the limitations of the given fire model, and shall be verified

and validated. Thus, V&V is necessary to establish acceptable uses and limitations of fire models.

In addition, analysts need to justify the appropriateness of fire model for specific applications.

Verification and validation of a calculation method are intended to ensure the correctness and

suitability of the method. Verification is the process to determine that a model correctly

represents the developer's conceptual description. It is used to decide whether the model was

"built" correctly. Validation is the process to determine that a model is a suitable representation

of the real world and is capable of reproducing phenomena of interest. It is used to decide

whether the right model was "built."

This project was driven by the following objectives:

" Conduct a V&V study of the selected fire models using a consistent methodology (ASTM

E 1355, Evaluating the Predictive Capability of Deternninistic Fire Models [4]) for NPP fire

protection applications.

* Quantify predictive capabilities of fire models to the extent that can be supported by

comparison with applicable and available fire experiment data.

This study evaluated the following five fire modeling tools:

(1) NRC's Fire Dynamics Tools (FDTs) (documented in Volume 3 of this report)

(2) EPRIL's Fire-Induced Vulnerability Evaluation, Revision 1 (FIVE-Rev 1) (documented in

Volume 4 of this report)

(3) National Institute of Standards and Technology's (NIST) Consolidated Model of Fire Growth

and Smoke Transport (CFAST) (documented in Volume 5 of this report)

(4) Electricitd de France's (EdF) MAGIC code (documented in Volume 6 of this report)

(5) NIST's Fire Dynamics Simulator (FDS) (documented in Volume 7 of this report).

1-2
Introduction

1.2.2 Approach

This program follows the guidelines of ASTM. E 1355, Evaluating the Predictive Capability of

Deterministic Fire Models [4], which ASTM International distributes as a guide to evaluate fire

models. That standard identifies four steps in the evaluation of predictive fire models:

(1) Define the model and scenarios or phenomena for which the evaluation is to be conducted.

(2) Assess the appropriateness of the theoretical basis and assumptions used in the model.

(3) Assess the mathematical and numerical robustness of the model.

(4) Validate the model by quantifying the uncertainty and relative difference' of the model

results in predicting the course of events for specific NPP fire scenarios.

Traditionally, a V&V study reports on the comparison of model results with experimental data

from a test series and, as such, the V&V of the fire model is for the specific tested fire scenarios.

V&V studies for the selected fire models do already exist, but it is necessary to investigate the

technical issues specific to the use of these models in NPP fire modeling applications.

In order to accomplish the ASTM E 1355 objectives, the following approach was developed and

implemented in this study:

(1) Define a list of typical NPP fire scenarios.

(2) Select test series from which experimental data will be used to perform the quantitative

validation.

(3) Select and describe the fire models for which an evaluation can be conducted.

(4) Define fire modeling parameters.

(5) Conduct the quantitative validation study for each fire modeling tool.

(6) Report validation results.

These steps are described in more detail in Chapter 2. This approach provides a roadmap, to

model users and developers for conducting a V&V based on ASTM E 1355.

The scope of this V&V study is limited to the capabilities of the selected fire models. As such,

certain potential fire scenarios in NPP fire modeling applications do not fall within the

capabilities of these fire models and, therefore, are not covered by this study. Examples of such

fire scenarios include high-energy arcing faults and fire propagation between control panels [5,

Section 7.2.2]. It is the user's responsibility to determine whether a model can be applied to each

specific fire scenario.

1.3 Report Structure

This report is presented in seven volumes:

*Volume 1, "Main Report," provides general background information, programmatic and

technical overviews, project results, insights, and conclusions. The description of the typical

commercial NPP fire scenarios is contained in Section 2 of Volume 1.

I See Section 2.5 for the specific definition of relative difference

1-3
Introduction

" Volume 2 presents a summary description of the fire tests and estimates of experimental

uncertainty used in this V&V study.

* Volumes 3 through 7 provide detailed discussions of the V&V of the FDVs, FIVE-Rev 1,

CFAST, MAGIC, and FDS fire models. Each report follows the guidelines provided by

ASTM E 1355 and contains the following chapters:

* Chapter 1, Introduction

* Chapter 2, Model Definition, briefly describes the fire model.

* Chapter 3, Theoretical Bases for the Model, includes theoretical descriptions of the fire

model. In addition, this chapter provides a literature review and discusses

the capabilities, limitations, and range of applications of the model.

* Chapter 4, Mathematical and Numerical Robustness, discusses the mathematical and

numerical robustness of the fire model.

* Chapter 5, Model Sensitivity, presents the results of sensitivity analyses conducted for

the fire model. In general, the sensitivity analysis evaluates model variations from a

base case scenario, as they are affected by changes in the input parameters.

" Chapter 6, Model Validation, documents the methodology and results of the V&V study.

* Chapter 7, References

" Appendix A, Technical Details for Validation Study

* Appendix B, Input Files

1-4
2

TECHNICAL APPROACH

ASTM E 1355 establishes a process for conducting a V&V study of a fire model. In general, the

process can be summarized in the following tasks:

* Model and scenario definition documents the model and the scenarios or phenomena of

interest for the V&V study.

* Description of the theoretical basis for the model documents a detailed technical

description of the thermo-physical processes addressed by the fire model.

" Mathematical and numerical robustness documents an evaluation of the numerical

implementation of the model.

" Model sensitivity documents a sensitivity analysis of the model.

" Model evaluation documents the results of the validation study.

There is, however, a technical challenge in implementing these tasks. Specifically, the universe

of fire scenarios in commercial NPPs is large and diverse. Also, scenarios may have

characteristics or attributes that either cannot be modeled using state-of-the-art computational

fire models, and/or no experimental data is available to support a V&V study of that particular

characteristic or attribute. Improvements in these two specific limitations - limited fire

modeling capabilities and/or insufficient experimental data - are needed.

In order to address these challenges, and still perform a V&V study consistent with ASTM

E 1355, the following approach has been selected:

(1) Define a list of typical NPP fire scenarios. This list of fire scenarios is intended to be a

reflection of the wide range of fire scenarios found in NPPs (i.e., the scope of scenarios for

which models would need validation). In the context of this V&V study, the list of scenarios

attempts to capture all the potential fire scenarios and the resulting conditions that could be

postulated in practical applications. However, some conditions in these scenarios cannot be

predicted with available models or do not have any available experimental data to support a

quantitative model evaluation. Scenarios are listed and described in Section 2. 1.

.(2) Select test series from which experimental data will be used to perform the quantitative

validation. The* selected test series reflects some of the characteristics of the fire scenarios

included in the list described in item 1 above. The selected tests are listed in Table 2.2.

(3) Select and describe the fire models for which an evaluation can be conducted.

Consistent with ASTM E 1355, the description of the selected fire models includes a review

of the theoretical basis and fundamental assumptions, an assessment of the mathematical and

numerical robustness, and a sensitivity analysis, as well as validation with experimental data.

As suggested earlier, (1) not all the predictive capabilities of each model have been subjected

to the V&V process, and (2) not all the fire-generated conditions in the library of fire

2-1
Technical Approach

scenarios can be predicted with the capabilities of state-of-the-art models. Selected models

are listed in Section 2.3.

(4) Define fire modeling parameters. It is necessary to identify fire-generated conditions for

which a generic validation study can be conducted given the available models and

experimental data. Based on the NPP fire scenarios, capabilities of the selected fire models,

and the available experimental data, the project team identified 13 fire modeling parameters

for which a quantitative validation study can be conducted. The fire modeling parameters are

described in Section 2.4.

(5) Conduct the quantitative validation study for each fire modeling tool. The quantitative

validation studies are conducted by comparing experimental data with fire modeling tool

predictions.

(6) Report validation results. Results from the quantitative validation study are reported as

relative differences for peak experimental measurements and model predictions, as well as

graphical comparisons between experimental measurements and model predictions.

Figure 2-1 graphically represents this approach. The following'sections describe the steps of this

approach in greater detail. This approach is documented and implemented in the individual

volumes using the data from Volume 2. It can be used as a roadmap, to model users and

developers for conducting a V&V for models other than those included in this study.

2-2
Technical Approach

NPP Fire Scenarios -Vol. 1, Section 2.1

(ASTM El1355, Section 7.2)

Define representative nuclear power plant

fire scenarios

'I

Fire Modeling Codes - Vol. 1, Section 2.3

(ASTM El1355, Chapters 7, 8, 9 & 10)

Select and describe the fire modeling codes

and the capabilities of the code for which the

V&V is conducted.

Fire Experiments - Vol. 1, Section 2.2

(ASTM E1355, Sections 11.3.3, &

11.3.3)

Define the set of fire experiments that will

support the quantitative validation.

Notice that the available experiments

do not cover all the identified NPP fire

scnpriarim

Fire Modeling Parameters -Vol. 1, Section 2.4

Define the attributes of fire scenarios for which

a quantitative V&V can be conducted.

LI

Quantitative V&V - Vol 1, Section 2.5

(ASTM E1355, Sections 11.3.7, & 11.3.9)

Perform quantitative V&V by comparing model

predictions to experimental data.

I

Report V&V Results - Vol. 1, Section 2.6

(ASTM E1355, Chapter 12)

Report V&V results in the form of graphical

comparisons and relative differences.

Figure 2-1: Overview of the Approach for V&V Study of Selected Fire Models

for Nuclear Power Plant Applications

2-3
Technical Approach

2.1 Library of Nuclear Power Plant Fire Scenarios

To conduct the V&V study in accordance with ASTM E 1355, it is necessary to define

the scenarios or phenomena of interest to evaluate each model. For the purpose of the V&V

study, a fire scenario definition should include a complete description of the phenomena of

interest in the evaluation to facilitate appropri ate application of the model. As mentioned in the

introduction to this chapter, this list of phenomena from the fire scenarios is intended to reflect the

collection of phenomena from fire scenarios found in NPPs. In the context of this V&V study, the

list of scenarios captures all the phenomena of interest that would be predicted by some fire

models, but may or may not have experimental data to support a quantitative model evaluation.

Consequently, this V&V study provides a quantitative evaluation for the phenomena defined by

the scenarios to the extent allowed by the available experimental data and the capabilities of the

selected models.

The list of fire scenarios presented in this section expands and/or modifies the list originally

compiled and documented by EPRI as part of the development of its "Fire Modeling Guide for

Nuclear Power Plant Applications" [5]. The basis for the selection of these fire scenarios is

as follows:

" Review the range of possible configurations that contribute to fire scenarios in the U.S.

commercial nuclear industry. The review focused on parameters considered important

in the definition of fire scenarios.

* Identify potentially risk-significant fire scenarios through review of the Individual Plant

Examination for External Events (IPEEE) submittals.

* Examine past industry experience with fire modeling in support of regulatory applications

(other than IPEEE) to help define these fire scenarios. A questionnaire was prepared and

distributed to all operating NPPs in the United States concerning their experience with fire

modeling. Also, with support from the NRC, industry submittals were searched to identify

the use of fire modeling.

Additional details are available in reference 5.

Further information on NPP fire scenarios is found in NUREG/CR-6850 [6]. This reference

discusses risk methods. that may be used to evaluate scenarios that can be outside the applicability

of the fire modeling tools evaluated in this report. Such scenarios include high-energy arcing

faults, main control board fires, and hydrogen fires.

The generic list of scenarios includes fires in the switchgear room (SWGR), cable spreading room (CSR),

main control room (MCR), pumnp room, turbine building, multiple compartment (corridor) scenarios,

multi-level building, containment (PWR), battery room, diesel generator room, computer room,

and outdoors. The descriptions below of the fire scenario are examples of how and where a fire

could start. The sources of fires described are representative of the typical configurations in

most NPPs.

2. 1.1 Switch gear Room

The SWGR is often an important area in a commercial NPP. A fire in a SWGR can have

significant fire risk repercussions and, hence, the SWGR is one of the two plant locations that are

2-4
Technical Approach

most often identified as the top fire risk contributors in fire risk assessments performed under the

IPEBE program 2. The reason the SWGR can be essential to plant operation is that it typically

contains equipment and circuits that provide the electrical power needed to operate and control

the plant. This area also contains potential sources of high-energy arcing faults that may be

located close to other safety-related equipment and/or circuits. Figure 2-2 graphically represents

the SWGR fire room scenario. The most common fire source in this scenario may be an

electrical cabinet. The size of the fire will depend on the type and amount of cables present in

the cabinet and the ventilation conditions within the cabinet itself. Typically, these rooms have

closed doors and are mechanically ventilated. Important targets may be cables in a cable tray

located above the switchgear cabinet that are exposed to flame, plume or ceiling jet conditions or

radiant heat flux from the fire. Targets may also be exposed to the hot gas layer thermal

conditions.

/ /7

Electrical Cabinet

(is a possible source of fire)

Figure 2-2: Switchgear Room Fire Scenario

2.1.2 Cable Spreading Room

The CSR is another critical location in a commercial NPP because it often contains redundant

instrumentation and control circuits needed for plant operation. The CSR generally contains a

high cable concentration (in cable trays and/or conduits), and fire propagation in open cable trays

can be an important aspect of fire modeling. Some NPPs have areas called cable tunnels or cable

lofts, which present similar challenges. These areas may also contain significant amounts of

cables in trays or conduits and may contain redundant circuits. Figure 2-3 graphically represents

the scenario. The source of a fire in this scenario may be transient combustibles, or electrical

cable or cabinets. The ventilation conditions in the room may be mechanical ventilation, or

possibly some level of natural ventilation via leakage around closed doors. Important targets

2 Individual NPP licensees conducted IPEEEs to assess the risks to the plant design from external events such as

earthquakes, high winds, and internal fires.

2-5
Technical Approach

may be cables in a cable tray located above the cabinet on fire that are exposed to plume or

ceiling jets conditions, or an electrical cabinet or tray exposed to radiant heat flux from the fire.

Targets may be also located in the hot gas layer and subjected to hot gas layer thermal

conditions.

Cable Trays Cables

Figure 2-3: Cable Spreading Room Fire Scenario

2.1.3 Main Control Room

Like the SWGR, the MCR is typically one of the two plant locations that are most often

identified as the top fire risk contributors in fire risk assessments performed under the IPEEE

program. The MCR contains redundant instrumentation and control circuits that are critical to

plant control and safe-shutdown. Analyses of fires in the MCR pose unique challenges, including

timing of fire detection, smoke generation, migration, and habitability (including visibility and

concentration of species); fire propagation within very large panels; and fire propagation

between panels. It should also be noted that some NPPs have areas (i.e., a relay room, auxiliary

equipment room, or remote shutdown panel) that are similar to MCRs, in that they contain

redundant instrumentation and control circuits that are critical to plant control and safe-shutdown.

However, such areas are not constantly manned like MCRs and may instead be equipped with

automatic suppression systems. A fire in the MCR may lead to, a situation where the reactor cannot

be controlled due to damage to the inistrumffentation and control circuits there. figure 2-4 graphically

represents a MCR scenario. This scenario can apply to one or more unit NPP control rooms. The

source of a fire in this scenario may be a control cabinet. The size of the fire will depend on the

type and amount of cables within the cabinet, as well as cabinet ventilation and detection and

suppression activities in the constantly-manned control room. The ventilation conditions in the

room will be mechanical ventilation. Important targets are adjacent control cabinets exposed to

radiant heat flux or flame impingement. Another important aspect of main control room fire

scenarios is the habitability conditions in the room as the fire progresses. Habitability conditions

2-6
Technical Approach

refer to smoke concentration (which affects visibility, toxicity), heat flux from the hot gas layer,

and room temperature. These conditions are important for determining when operators may need

to leave the control room as a result of relatively high temperatures or low visibility.

main Control Board

\ Control Cabinets/

Figure 2-4: Main Control Room Fire Scenario

2.1.4 Pump Room

This location represents areas in a plant where a relatively large fire is possible in a small

enclosure. However, not all pump rooms are small, since relatively large pumps can be found in

large open areas such as turbine building elevations. Figure 2-5 graphically represents the

scenario. The source of a fire in this scenario may be ignition of an oil pooi spilled from a pump.

The size of the fire will depend on the type and amount of oil spilled, as well as the area and

depth of the pool itself. The growth of this fire typically will be fast, and depending on the size

of the room, the fire could possibly generate flashover conditions that may challenge the walls

and ceiling. The ventilation conditions in the room will be mechanical ventilation with leakage

around closed doors. Targets of interest in these scenarios may be the walls and ceiling of the

enclosure, which are fire barriers, as well as any other safety-related equipment and cables

located in the room or area. These targets may be exposed to direct flame impingement or flame

radiation or plume, ceiling jet, or hot gas layer conditions.

2-7
Technical Approach

Figure 2-5: Pump Room Fire Scenario

2.1.5 Turbine Building

A turbine building is usually a multi-level enclosure3 , in which the top level is commonly referred

to as the turbine operating deck. A fire scenario on the turbine deck was selected to examine large

(e.g., turbine lube oil) or small (e.g., transient or panel) fires in large enclosures with high

ceilings. A multi-level turbine building fire is described in Section 2.1.7. The scenario can apply

to buildings with one or more turbines. Figure 2-6 graphically represents the scenario. The

source of a fire in this scenario may be ignition of an oil pool spilled from one of the turbines.

The size of the fire will depend on the type and amount of oil spilled, as well as the area and

depth of the pool itself. The growth of this fire will be fast. Other sources of fire in the turbine

building could be electrical fires (e.g. high energy arching faults), transformer or switchgear

fires, and hydrogen fires. The ventilation conditions will be natural ventilation, with many open

shafts (e.g. open equipment hatches), doors and windows. There may also be mechanical

ventilation using roof-mounted exhaust fans and/or mechanical supply. Targets of interest in

these scenarios may be structural steel members and fire barriers, as well as any other safetyrelated equipment and cables located in the area and exposed to the fire. Fire conditions

affecting the targets may include direct flame impingement, fire plume conditions, or flame

radiation.

3 Some NPPs (typically in warmer climates) do not have a turbine building, and the main turbine is open

to the elements.

2-8
Technical Approach

Equipment

H-atch

Figure 2-6: Turbine Building Fire Scenario

2.1.6 Multi-Compartment Corridor

Many commercial NPPs have enclosures with multiple compartments that open into a common

space or corridor. The significance of these enclosures in terms of fire safety varies from plant-toplant because they house various mechanical, electrical, waste treatment, or other equipment and/or

circuits. Figure 2-7 graphically represents this scenario, which consists of a fire in one

compartment affecting targets in an adjacent compartment. The multi-compartment corridor

considered in this scenario consists of interconnected rooms and corridors in the same level.

These geometries may have soffits between the connecting rooms. The source of a fire in this

scenario may be ignition of an oil pool spilled from a pump in one of the adjacent rooms. The

size of the fire will depend on the type and amount of oil spilled, as well as the area and depth of

the pool itself. The growth of this fire typically will be fast and, depending on the size of the

room, the fire could potentially generate flashover conditions in the room of origin, and fire

effluent may spill out and effect targets in adjacent rooms. The ventilation conditions will be

natural ventilation, with leakage paths between compartments around normally closed doors.

There may also be mechanical ventilation using both injection and extraction systems. Targets

of interest in these scenarios are often safety-related equipment and cables located in the corridor

outside the room of fire origin, or an adjacent room. These targets will be subjected to smoke

flows migrating out of the room of fire origin.

2-9
Technical Approach

Pump Oil Spill (is a possible source of fire) Battery Room Switch Gear

(is a possible source of fire) (is a possible source of fire)

Figure 2-7: Multi-Compartment Corridor Fire Scenario

2.1.7 Multi-Level Building

A typical NPP has locations where multiple elevations in the same building are separated by

partial floors/ceilings, open hatches, or staircases. Typical examples include turbine buildings,

pressurized-water reactor (PWR) auxiliary buildings, and boiling-water reactor (BWR)

buildings. The multi-level turbine building in this scenario is a three-level space that includes

the turbine deck. (Section 2.1.5 describes a turbine deck fire scenario.) This scenario consists of

an oil spill fire affecting targets located on a different level. Figure 2-8 graphically represents

the scenario, which can apply to turbine buildings with one or more units. The source of a fire in

this scenario may be ignition of an oil pool spilled from an oil tank located under one of the

turbine generators. The size of the fire will depend on the type and amount of oil spilled, as well

as the area and depth of the pool itself. The energy and smoke created will flow through

mezzanine opening between levels. The growth of this fire will be fast. The ventilation

conditions will be natural ventilation via openings on the upper level. There may also be

mechanical ventilation using roof-mounted exhaust fans and/or mechanical supply. Targets of

interest in these scenarios may be cables in cable trays located on the upper levels.

2-10
Technical Approach

Turbines

whichueclnrCal) bonafs a hig dome celig anlrevoue Figure 2-

graphically~~~~~~~~~~ýIar repesnt teseaiwchnvlsanOil spllý fiefoml th rato coan pm

(RCP).~~~~~~~~~~~~~~~~~ of the fiewl eedo Th sizee h yp n muto ipleda elasteae

and~~~Fgr oftepolisl.lh depth otainmeent in air WhScinernalriroeiclto ldn ytm

with8 Colnunt.Teeinofeharaddittecontainment atmspereduing normal

operaton.thinentrgt ofldn intrs in this scentari iseanelevted bcable oitra leomercatedoutsidertheifir

plume. Thesue targetsimay beunarexpsed to direc flamed cimpingement or flamge raitonoolumeiurclueiling o ejet argho tg s l ay con ber itons.dt i e tfa ei p n e e to l m ai t o rp u e

2-1 1
Technical Approach

Containment Building (concrete)

Figure 2-9: PWR Containment Building Scenario

2.1.9 Battery Room

Battery rooms are usually relatively small concrete rooms with two or more large banks of batteries.

These rooms are kept closed and are typically free of transient combustibles and fixed ignition

sources other than the batteries. EPRI's Fire Events Database suggests two types of scenarios:

(1) explosion of the battery cells during the charging phase of the battery, and (2) fires in battery

terminals as a result of defective or unsecured terminals. Rooms are usually mechanically

ventilated. The targets of interest in this scenario are nearby cables and batteries. These targets

may be exposed to direct flame impingement or flame radiation or plume, ceiling jet or hot gas

layer conditions.

2.1. 10 Diesel Generator Room

Diesel generator rooms house the standby diesel generator (SBDG) and associated electrical

cabinets. This scenario consists of a fuel oil fire near the diesel generator. The size of the fire

will depend on the type and amount of fuel oil spilled, as well as the area and depth of the pool

itself. The growth of this fire will be fast. The ventilation conditions in the room will be

mechanical ventilation with leakage around closed doors. Targets of interest in these scenarios

2-12
Technical Approach

may be cables located in the room exposed to HGL temperatures. These targets may be exposed

to direct flame impingement or flame radiation or plume, ceiling jet, or hot gas layer conditions.

2. 1.11 Computer or Relay Room

Computer rooms are typically located in close proximity to the main control rooms in NPPs.

In addition to computers and other office equipment, some computer rooms may house control

cabinets or banks of relay panels.. The ignition source for this scenario is a transient combustible

fire, namely a computer workstation. The size of the fire will depend on the amount and type of

materials involved. The ventilation conditions will be mechanical ventilation. The targets of

interest may be control cabinets or banks of relay panels or cables above the fire. These targets

may be exposed to direct flame impingement or flame radiation or plume, ceiling jet, or hot gas

layer conditions.

2.1.12 Outdoors

Outdoor fire scenarios can involve large oil-filled transformers or hydrogen tanks and can affect

or propagate to nearby equipment. Nearby equipment can include other transformers, other

electrical equipment, turbine building walls, etc. Considering that fires will be outdoors, fire

conditions that could affect targets include flame radiation and exposure to fire plumes. In the

case of transformers, fires can be attributable to oil leaks or spills or electrical faults.

Consequences will depend on the type of fire analyzed (i.e., a "regular" fire vs. an explosion).

2.2 Fire Models

There are numerous fire models that have been developed and maintained by various

organizations to predict fire-generated conditions. This study selects the following five of these

fire models, which represent a wide range of capabilities and mathematical and computational

sophistication:

" Two libraries of engineering calculations: FDTS and FIVE-Rev 1

* Two two-zone models: CFAST and MAGIC

" One field model: FDS

These particular models were chosen based on the fact that most of them have been used to

calculate fire conditions in NPP fire protection applications, or were developed by stakeholders

within the nuclear industry for NPP fire protection applications. FDS was chosen to represent

the most complex types of models available for fire protection applications.

2.2.1 Libraries of Engineering Calculations: FDr and FIVE-Revi

FDTS is a library of engineering calculations (also referred to as hand calculations) in the form of

Microsofto Excelo spreadsheets. For the most part, the models in the FDTS library are closed-form

algebraic expressions programmed in spreadsheets to provide a user-friendly interface

that reduces input and computational errors. Technical details concerning the engineering

calculations and use of the spreadsheets are available in NUREG- 1805 [71.

FIVE-Rev 1 is another library of engineering calculations in the form of Microsoft® Excel®

spreadsheets. Specifically, FIVE-Rev 1 library consists of fuinctions programmed in Visual Basic

2-13
Technical Approach

for Applications, which is the programming language within Excelo. Having the models

programmed as Microsofte Excelo fuinctions allows the use of Excelo spreadsheets as the*

interface. Technical details concerning the engineering calculations and their use in the Excel'rý

environment are available in EPRI TR- 1002981 [5].

The FDTS and FIVE-Rev 1 libraries include different models, and some of those models were not

evaluated for this V&V study, because of applicability and a lack of experimental data. Table 2-1

shows the equations that were used from each library to evaluate fire scenario attributes.

The fire scenario attributes that were selected for this study (see Section 2.4 for the description

of these attributes) are those that are used in NPP fire modeling applications. For the most part,

these selected models are included in both libraries.

Table 2-1: FDTS and FIVE-Revi Models for the Fire Scenario Attributes

Selected for this V&V Study

Attribute (See Section 2.4) FOTs FIVE-Revi

1. Hot gas layer temperature MQH, EPA, Beyler, Beyler & MQH, FPA Deal

2. Hot gas layer height Yamana & Tanaka No model

3. Ceiling jet temperature No model Alpert's ceiling jet temperature correlation

4.Plm tmprtueHeskestad's plume Heskestad's plume 4. Pumetemerauretemperature correlation temperature correlation

5. eihtHeskestad's lae flame height Heskestad's flame height 5. heghtcorrelation lam correlation

6. Rdiaed eatflu totarets Point source flame radiation Point source flame radiation

6. adite he fuxto argts model, Solid flame model model

2.2.2 Two-Zone Fire Models: CFAST and MAGIC

Fire modeling programs that were developed under the assumption that a fire will generate two

distinct zones with uniform thermal properties are referred to as two-zone models. This V&V

study evaluated two two-zone models, CFAST and MAGIC.

CFAST [8] is a two-zone fire model that predicts the environment that arises within

compartments as a result of a fire prescribed by the user. CFAST was developed and is

maintained primarily by the Fire Research Division of the National Institute of Standards and

Technology (NIST). In terms of modeling capabilities, CFAST provides the average

temperatures of the upper and lower ga's layers within each compartment; flame height; ceiling,

wall, and floor temperatures within each compartment; flow through vents and openings; visible

smoke and gas species concentrations within each layer; target temperatures; heat transfer to

targets; sprinkler activation time; and the impact of sprinklers on the fire heat release rate (HRR).

MAGIC [9] is a two-zone fire model developed and maintained by Electricitd de France (EdF).

It is available through EPRI to its members. In terms of modeling capabilities, MAGIC predicts

(1) environmental conditions in the room (such as hot gas layer temperature, and oxygen/smoke

2-14
Technical Approach

concentrations), (2) heat transfer-related outputs to walls and targets (such as incident

convective, radiated, and total heat fluxes), (3) fire intensity and flame height, and (4) flow

velocities through vents and openings.

2.2.3 Field Fire Model: FDS

FDS [10] is a computational fluid dynamics (CFD) model of fire-driven fluid flow. The model

numerically solves a form of the Navier-Stokes equations appropriate for low-speed, thermally

driven flow, with an emphasis on smoke and heat transport from fires. The partial derivatives of

the equations for conservation of mass, momentum, and energy are approximated as finite

differences, and the solution is updated in time on a three-dimensional, rectilinear grid. Thermal

radiation is computed using a finite volume technique on the same grid as the flow solver.

Lagrangian particles are used to simulate smoke movement and sprinkler discharge.

FDS computes the temperature, density, pressure, velocity, and chemical composition within

each numerical grid cell at each discrete time step. There are typically hundreds of thousands

to several million-grid cells, and thousands to hundreds of thousands of time steps. In addition,

FDS computes the temperature, heat flux, mass loss rate, and various other quantities at solid

surfaces.

.2.3 Experimental Data

This section provides a general overview of the test series and experiments selected for this study.

Volume 2 augments this overview by providing detailed descriptions of these experiments.

Some test series included many experiments, from which only a few were chosen for this V&V

study. One overriding reason for this is that the sheer amount of data that is generated and must

be processed can be overwhelming, so limiting the number of experiments to consider was

necessary. The experiments within the test series that were chosen are representative of the

overall series of tests, as well as representative of the fire scenarios in NPPs listed above.

Volume 2, Section 1. 1, has a more complete explanation for the selection of the experiments.

2.3.1 Factory Mutual & Sandia National Laboratories (FMISNL) Test Series

A series of fire tests was conducted at Sandia National Laboratories (SNL) under the sponsorship

of the NRC in the mid- 1980s. Specifically, tests were conducted using simple gas-fired burner,

heptane pool, methanol pool, and solid polymethyl-methacrylate (PMMA) fires. Four of these

tests were conducted with a full-scale control room mockup in place. Parameters varied during

*testing were fire intensity, enclosure ventilation rate, and fire location. The primary purpose at

the time of these tests was to provide data for use in validating computer fire environment

simulation models that would subsequently be used in analyzing NPP enclosure fire scenarios,

.specifically MCR scenarios.

These tests were conducted in an enclosure measuring 18.3 in x 12.2 mnx 6.1 mn (60 fi x 40 ftix

20 ft), which was constructed at the Factory Mutual Research Corporation fire test facility in

Rhode Island. All of the tests utilized forced ventilation conditions. The ventilation system was

designed to simulate typical NPP installation practices and ventilation rates.

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Technical Approach

NUREG/CR-468 1 [11] provides a detailed description of the FMISNL test series, including the

types and location of measurement devices as well as some results. Additional results

are reported in NUREG/CR-5384 [121.

This study used data from only the three tests with data reported in NUREG/CR-468 1 (namely

FM/SNL Tests 4, 5, and 21). For all three tests, the fire source was a propylene gas-fired burner

with a diameter of approximately 0.9 m (2.95 ft), with its rim located approximately 0.1 mn (0.33

ft) above the floor. For FM/SNL Tests 4 and 5, the burner was centered along the longitudinal

axis centerline, 6.1 mn (20 ft) laterally from the nearest wall. For FMISNL Test 2 1, the burner

was placed within simulated benchboard electrical cabinets.

2.3.2 The National Bureau of Standards (NBS) Test Series

A total of 45 tests representing 9 different sets of experiments, with multiple replicates of each set,

were conducted in a three-room suite at NBS that is described in detail in NBSIR 88-3752 [13].

These tests were conducted in the mid-1980s as well. NBS is now known as NIST. The suite

consisted of two relatively small rooms, designated here as Rooms 1 and 3, which were

connected via doorways and short connecting passageways to a relatively long corridor,

designated as Room 2. Rooms I and 3 opened only onto the corridor (Room 2) via doorways;

they did not open to the external enviromnment other than through normal construction leakage paths.

The corridor had a doorway to the external environment, as well as doorways to Rooms 1 and 3..

The fire source, a gas-fired burner, was located against the rear wall of Room 1. The following

parameters were varied in the 9 different sets of experiments:

*fire size, including nominal 100, 300, and 500 kW fires

*door positions, including open and closed doors between the corridor and Room 3, as well as

between the corridor and the external environment

In this study, the tests designated as Sets 1, 2, and 4 in NBSIR 88-3752 are used for comparison.

All three of these sets had a fire source intensity of 100 kW, but the sets differed based on door

position. Specifically, the door between Rooms I and 2 was open for all three sets. However,

for Set 1, the door between Room 2 and the external environment was open (providing a source

of fresh air to the suite), while the door between Rooms 2 and 3 was closed (effectively isolating

Room 3 from this test). By contrast, for Set 2, the door between Room 2 and the external

environment was closed, as was the door between Rooms 2 and 3 (again isolating Room 3).

For Set 4, the door between Room 2 and the external environment was open (again providing

a source of fresh air to the suite), as was the door between Rooms 2 and 3.

Experimental data used for these comparisons was obtained in electronic format from NIST.

These data were converted to spreadsheet format for tests designated as MV 1 OOA through

MV1I00AB. Average values for the nine data sets were also converted to spreadsheet format,

but were not used for these comparisons. Rather, an exemplar test was selected from each data set

for comparison purposes. Specifically, Test MV1I00A was used for Set 1, Test MV 1000

was used for Set 2, and Test MV IOOZ was used for Set 4. The selected data are also available

in EPRI's Fire Modeling Code Comparison TR-108875 [14].

2-16
Technical Approach

2.3.3 The International Collaborative Fire Model Project (ICFMP) Benchmark

Exercise Test Series

To date, four full-scale fire test series have been completed as part of the ICFMP. The ICFMP is

a separate, but related, project designed to conduct validation studies of fire models from around

the world. ICFMP participants conduct a series -of experiments and provide the data to other

participants in order to compare fire model outputs to experimental data. These test series are

referred to as benchmark exercises (BEs). This V&V study includes experimental data from BEs

#2, 3, 4, and 5. A brief description of each follows:

*0 BE #2 [15]: These tests were conducted in the late-1990s. The ICFMP objective of BE #2

was to examine scenarios that are more challenging for zone models. In particular, these

scenarios included fires in larger room volumes that are representative of turbine halls in

NPPs. The tests were conducted inside the VTT Fire Test Hall, which has dimensions of

19 m high x 27 m long x 14 mn wide (62.3 ft x 88.6 ft x 45.9 ft). Each case involved a single

heptane pool fire, ranging from 2 MW to 4 MW.

* BE #3 [16]: This ICFMP exercise comprised a series of 15. large-scale fire tests, sponsored

in part by the NRC, that were performed at NIST between June 5 and 20, 2003. These tests

consisted of 350 kW 1.0 MW, and 2 MW fires in a marinite room with dimensions of

21.7 m x 7.15 mnx 3.7 m (71.2 ft x 23.5 ft x 12.1 ft). The room had one door with dimensions

of 2 m x 2 m (6.6 ft x 6.6 ft), and a mechanical air injection and extraction system.

Ventilation conditions and fire size were varied among the 15 tests. The numerous

experimental measurements included temperatures in gas layers and surfaces, heat fluxes,

and gas velocities, among others.

* BE #4 [17]: This test series was conducted at the Institut fiir Baustoffe, Massivbau Und

Brandschutz (iBMB), in Germany in 2003 and 2004. Each of these tests simulated a

relatively large fire in a relatively small concrete room. Only one test from this series was

selected for this study.

* BE #5 [18]: This exercise, which was conducted at the iBMB in Germany in 2003 and 2004,

consisted of four large-scale tests inside the same concrete enclosure as BE #4 with

realistically routed cable trays. Only one test was selected for this study.

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Technical Approach

2.4 Selection of Fire Modeling Parameters

A complete V&V of a particular model for a given NPP fire scenario may not be possible

because (1) the availability of experimental data is limited, and/or (2) a selected tool has limited

modeling capabilities. Therefore, this implementation of ASTM E 1355 is intended to benefit

as much as possible from the available data to establish the modeling capabilities and limitations

of the selected fire models in typical NPP fire scenarios.

An important consideration in evaluating the capabilities of fire models in NPPs is the range of

fire scenarios for which the models may be used. From a fire modeling perspective, most NPPs

have similar configurations and fire hazards. That is, fire scenarios are characterized by similar

attributes. Consequently, the V&V project team developed the following list of typical NPP fire

modeling parameters, which provided the basic framework for conducting the V&V study and

classifying the quantitative results:

(1) Hot gas layer temperature: The hot gas layer temperature is particularly important in

NPP fire scenarios because it can provide an indication of target damage awa y from

the ignition source. Models predict the increase in environmental temperature attributable

to the energy released by a fire in a volume. However, different models define this volume

in different ways. In the FDTS and FIVE-Rev 1 models available for predicting hot gas

layer temperature, the assumed volume is the volume of the upper layer of the room and the

output is a uniform upper layer temperature. In the CFAST and MAGIC two-zone models,

the room is divided into upper and lower control volumes. Thus, the hot gas layer

temperature output from these two-zone models is a uniform temperature in the upper

control volume (which is referred to as the hot gas layer because it accumulates hot gases

that are transported to the upper part of the room by the fire plume). Finally, in the FDS

field model, the room is divided into numerous control volumes. Thus, FDS can provide

outputs for the average temperature of the control volumes in the upper layer of the

computational domain, as determined by a reduction of temperature profile data.

(2) Hot gas layer height: The height of the hot gas layer is also important in NPP fire scenarios

because it indicates whether a given target is immersed in and affected by hot gas layer

temperatures. The concept of hot gas layer height is most relevant in two-zone models

(CFAST and MAGIC), in which this attribute defines the interface between the upper and

lower control volumes. The FDS field model also provides the hot gas layer height output,

which is calculated from the temperature profile within the height of the room. In addition,

the FDTS library includes one model that predicts hot gas layer height before the layer

reaches a vent, assuming steady-state fire conditions in the room. However, because of the

assumptions of this model and the algorithm used to process the experimental data, it does

not apply to or could not be compared to the tests series included in this study. The FIVERev I library does not have a model for predicting hot -gas layer height in the scenarios

evaluated in this V&V study.

(3) Ceiling jet temperature: The ceiling jet is the shallow layer of hot gases that spreads

radially below the ceiling as the fire plume flow impinges on it. This layer of hot gases has

a distinct temperature that is higher than the temperature associated with the hot gas layer.

This attribute is important in NPP fire scenarios that subject targets to unobstructed ceiling jet

gases. The FIVE-RevI and MAGIC models calculate ceiling jet temperature using a semiempirical correlation, and the ceiling jet temperature can be obtained from the FDS model

2-18
Technical Approach

by inspecting the temperature profile in the pre-defined grid. The FDTS library does not

include a model for calculating ceiling jet temperature, and the CFAST model does not

provide ceiling jet temperature as a direct output.

(4) Plume temperature: The fire plume is the buoyant flow rising above the ignition source,

which carries the hot gases that ultimately accumulate in the upper part of a room to form

the hot gas layer. The plume is characterized by a distinct temperature profile, which is

expected to be higher than the ceiling jet and hot gas layer. This attribute is particularly

important in NPP fires because of the numerous postulated scenarios that involve targets

directly above a potential fire source. Models in the FDTS and FIVE-Rev I libraries predict

fire plume temperatures using closed-form semi-empirical correlations, and the MAGIC

model predicts plume temperatures in a similar manner. The plume temperature can also

be obtained from the FDS model by inspecting the temperature profile in the pre-defined

grid. The CFAST model does not provide plume temperatures as an output.

(5) Flame height: The height of the flame is important in those NPP fire scenarios where

targets are located close to the ignition source. Some of these scenarios subject the target

to flame temperatures because the distance between the target and the ignition source is

less than the predicted flame height. A typical example would be cable trays above an

electrical cabinet. Models in the FDTs and FIVE-Rev 1 libraries predict flame height using

a close form semi-empirical correlation. MAGIC and CFAST models also predict flame

height in a similar manner. The FDS combustion model has the capability to calculate

flame height.

(6) Radiated heat flux to targets: Radiation is an important mode of heat transfer in fire

events. The modeling tools within the scope of this study address fire-induced thermal

radiation (or radiated heat flux) with various levels of sophistication, from simply estimating

flame radiation, to calculating radiation from different surfaces and gas layers in the

computational domain. The FDTS and FIVE-Rev 1 libraries include models for calculating

flame radiation at a specified distance from the flames. By contrast, CEAST, MAGIC,

and FDS have sophisticated heat transfer models that account for radiation exchanges

between room surfaces and the upper and lower gas layers. Therefore, the incident thermal

radiation to which a given target is exposed is a result of the heat balance at the surface of

the target (which includes all of the exchanges), as well as the thermal radiation received

from the flames.

(7) Total heat flux to targets: In contrast to thermal radiation (or radiated heat flux), the total

heat flux a target is subjected includes convective heat transfer. Convective heat transfer is a

significant contributor to target heat-up in scenarios that involve targets in the hot gas layer,

ceiling jet, or fire plume. The CFAST and MAGIC two-zone models and the FDS field

model account for convection, although CFAST (in particular) does-not model target

heating in the plume and ceiling jet sub-layers. The heat transfer models in the FDTS and

FIVE-Rev I libraries do not account for convective heat transfer.

(8) Total heat flux to walls: This attribute was included as a separate attribute in this V&V

study in order to evaluate model capabilities to determine the incident heat flux to walls,

floors, and ceilings, which includes the contributions of radiation and convection. Because

the heat conducted through the walls, floors, and ceilings does not contribute to room heatup, it can be an important factor in the heat balance in control volume(s) in contact with the

2-19
Technical Approach

surfaces. Of the models within the scope of this study, only the CFAST and MAGIC twozone models and the FDS field model calculate total heat flux to walls, floors, and ceilings.

(9) Wall temperature: This attribute was included as a separate attribute in this V&V study

to evaluate model capabilities to determine the temperature of walls, floors, and ceilings.

Of the models within the scope of this study, only the CFAST and MAGIC two-zone models

and the FDS field model provide the temperatures of these surfaces as outputs, since such

outputs are part of the calculations required to determine the heat losses through

boundaries.

(10) Target temperature: The calculation of target temperature is perhaps the most common

objective of fire modeling analyses. The calculation of target temperature involves an

analysis of localized heat transfer at the surface of the target after determining the fireinduced conditions in the room. The CFAST and MAGIC two-zone models and the FDS

field model calculate the surface temperature of the target as a function of time, and

consider the heat conducted into the target material. By contrast, the available model in the

FIVE-Rev 1 library assumes a constant incident heat flux and a semi-infinite solid. The

FDTS library does not include a model for estimating target temperature.

(11) Smoke concentration: The smoke concentration can be an important attribute in NPP fire

scenarios that involve rooms where operators may need to perform actions during a fire.

This attribute specifically refers to soot concentration, which affects how far a person can

see through the smoke (visibility). The CFAST and MAGIC two-zone models and the FDS

field model calculate smoke concentration as a fuinction of time. These models determine smoke

concentration as the fire plume carries combustion products into the hot gas layer.

The FDTS and FIVE-Rev 1 libraries do not contain direct outputs of smoke concentration.

(12) Oxygen concentration: Oxygen concentration is an important attribute potentially

influencing the outcome of fires in NPPs because of the compartmentalized nature of

NPPs. Oxygen concentration has a direct influence on the burning behavior of a fire,

especially if the concentration is relatively low. The CFAST and MAGIC two-zone

models calculate the oxygen concentration in the upper and lower layers, and the FDS

model calculates the oxygen concentration in each control volume defined in the

computational domain. The FDTS and FIVE-Rev 1 libraries do not include models for

calculating oxygen concentration.

(13) Room pressure: Room pressure is a rarely used attribute in NPP fire modeling. It may be

important when it contributes to smoke migration to adjacent compartments. CEAST,

MAGIC and FDS calculate room pressure as they solve energy and mass balance equations

in the control volume. FDTS library has a model for a sealed compartment that is not

validated in this study. FIVE-Rev I library does not have correlation to calculate room

pressure.

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Technical Approach

Table 2-2: Fire Modeling Attributes as Outputs

Fire Models

Fire Modeling Attributes

FDTs FIVE CFAST MAGIC FDS

Hot Gas Layer Temperature Yes Yes Yes Yes Yes

Hot Gas Layer Height Yes' No Yes Yes Yes

Ceiling Jet Temperature Nj4~o Yes Yes Yes Yes

Plume Temperature Yes Yes ~VNo~ Yes Yes

Flame Height Yes Yes Yes Yes Yes

Radiated Heat Flux to Targets Yes Yes Yes Yes Yes

Total Heat Flux to Targets ~ No2 No Yes Yes Yes

Total Heat Flux to Walls NoN Yes Yes Yes

Wall Temperature No No Yes Yes Yes

Target Temperature N~o ~No Yes Yes Yes

Smoke Concentration NoN Yes Yes Yes

Oxygen Concentration NoN Yes Yes Yes

Room Pressure No> No Yes Yes Yes

1This output was not evaluated because it was not applicable for experiments used in this study.

2-21
Technical Approach

2.5 Quantitative Validation

In keeping with the guidance in the ASTM E 1355 and the objectives of this study, the following

approach was used for quantification of the results of the validation of the selected fire models.

The numerical comparison between an experimental observation and a corresponding model

prediction is referred to as "relative difference" throughout this report. Relative differences have

been calculated for each of the attributes listed in Section 2.4 using point estimate peak values

from fire experiments and model predictions. The following equation, which is described in

reference 4, has been selected for relative difference calculations:

AM -AE -(MP -M.)-(Ep -E.)

AE (E - E,

where AM is the difference between the peak value (Mp) of the model prediction and the ambient

value (M,,), and AE is the difference between the experimental observation (Ep) and the ambient

value (E.). In the context of this study, for the parameters Oxygen Concentration and HGL

Height, the "peak" value is actually the minimum value.

Table 2-3 summarizes the fire experiments and instruments used for quantitative validation of

the different fire modeling parameters. The limited amount of data in the table is a reflection of

the experimental data sets used in this study and, in general, the availability of reliable data in the

literature. Data for some of the parameters (i.e., smoke, compartment pressure, radiant and total

heat flux, etc.) was not collected in all of the test series. Because the data used to evaluate each

parameter is different, the generality of each of the results is correspondingly limited. If more

data becomes available in the future, it should be used to update the results in this report series.

The graphical comparisons of measured and predicted fire-generated condition profiles and

calculated relative differences for each of the five fire models are detailed in Appendix A to

Volumes 2 through 6. This information is the basis for the conclusions summarized in this

volume.

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Technical Approach

Table 2-3: Summary of the Fire Tests Used for Validation against Typical NPP Fire Scenario Attributes

NIST Multi- Fire Modeling Parameters ICFMP BE #3 ICFMP BE #5 FM/SNL ICEMP BE #4 ICFMP BE #2 Ro et

Tests, 1-5, 7-10,_ 13-18, Test 4 Tests 4,5, & 21 Test 1 atLCss 0A 00

1,2,31010Z

Vriathroope Vertical Vertical Vertical Vertical Vertical

1. HGL temperature Vertialy hrocul thermocouple thermocouple thermocouple thermocouple thermocouple

arasarrays aray arrays arrays arrays

Vriathroope Vertical Vertical Vertical Vertical Vertical

2. HGL height Vertialy hrocul thermocouple thermocouple thermocouple thermocouple thermocouple

arasarrays aray arrays arrays arrays

3. Ceiling jet temperature Thermocouple NA Thermocouple NA NA NA

4. Plume temperature NA NA Thermocouple NA Thermocouple NA

5. Flame height Pictures No Data No Data No Data Pictures No Data

6. Radiant heat flux to target Radiometers No Data No Data No Data No Data No Data

(cables)

7. Total heat flux to targets Heat flux gauges Heat flux gauges No Data Heat Flux No Data No Data Gauges

8. Total heat flux to walls Heat flux gauges No Data No Data No Data No Data No Data

9. Wall surface temperature Thermocouples Thermocouples No Data Thermocouples No Data No Data

10. Target (cable) surface Thermocouples Thermocouples No Data Thermocouples No Data No Data

temperature

2-23
Technical Approach

12.Oxyen onelnt Pramtion Oxygen metr#, Oxygen mete No DataN -Flawe Dat Noat No Da lta -

113 RSokomnpessrnrsuetranin Soeosducerc No Data No Data No Data No Data No Data

2-24
Technical Approach

2.6 Reporting and Applicability of the Validation Results

Section 2.1 of this volume listed typical NPP fire scenarios. The validation results of this study

are limited by the general characteristics of the fire experiments selected. Consequently, the

validation results need to be identified as corresponding to specific NPP fire scenarios to

determnine its applicability.

In general, the use of the quantitative results of this validation in support of fire modeling

requires the following two steps:

1. Applicability of V& V Results: First, the user needs to assess the applicability of the

validation results for the scenario under consideration.

2. Characterization offire mode/ predictions based on the V& V results: Once the user

determines the applicability of the validation, the user must determine the level of confidence

in the model prediction based on the quantitative results of this validation.

2.6.1 Applicability of the V&V Results

The following is one method that may be used to determine applicability of these validation

results to other specific NPP fire scenarios. The description of this method is reported here to

demonstrate the rigor users should use in determining applicability of these validation results.

Other methods may be appropriate.

The applicability of the validation results can be determined using normalized Parameters

traditionally used in fire modeling applications. Normalized parameters allow users to compare

results from scenarios of different scales by normalizing physical characteristics of the scenario.

Table 2-4 lists selected normalized parameters that may be used to compare encountered

scenarios with the experiments used in this validation study. It is intended to provide guidance

on which groups to consider when evaluating a certain attribute based on the validation results.

Table 2-5 lists the ranges of values for different physical characteristics and normalized

parameters based on the experiments considered in this validation study.

The user could calculate the normalized parameters that are relevant to the fire scenario being

evaluated. If the parameters fall within the ranges evaluated in this validation, then the results of

this study offer appropriate validation for the scenario. If they fall outside the range, then a

validation determination cannot be made based on the results in this study. For any given fire

scenario, more than one normalized parameter may be necessary for determining applicability of

the validation results.

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Technical Approach

Table 2-4: List of Selected Normalized Parameters for Application

of the Validation Results to NPP Fire Scenarios

Normalized Parameter General Guidance'

This parameter may be used for determining if

Heat release Qthe heat release rate and flame height in the

rate & flame Qd analyzed scenario is within the range of heat

height [19] P.Cpc . Iý D release rates and flame heights within the

scope of this study.

Room/Target H_ Q______ involving a target immuersed in the fire plume.

height [20] * where D* =his parameter suggests if the target elevation

D.CP .ý above the base of the fire is within the range

included in this study.

This parameter may be used in scenarios

involving a target in the ceiling jet. This

Ceiling jet rjparameter suggests if the horizontal radial

radial distance H distance from the target to the centerline of the

plume is within the range included in this

study.

Natural 1 - This parameter may be used for determining if

Ventilation lFr O IQAH~ 0.23 x 2 A, Fh, the natural ventilation conditions in the room

[19] 0 during the fire event is within the range of

r T conditions included in this V&V report.

*~ ~, . This parameter may be used for determining if

Mechanical mrhm _?O Q/A.H /0.23 x P air. V the mechanical ventilation conditions in the

Vniain 0 r r room during the fire event is within the range of conditions included in this V&V report.

This parameter may be used for scenarios in

W-I or L-, W and L are room width and which the room size is an input to the fire

Room Size H H model. These parameters suggest if the room

length, respectively. H is room height. size in .the scenario under analysis is Within the

room sizes included in this V&V study.

2 This parameter may be used for scenarios

(D)' weeDi h imee ftefrn involving radiated heat flux from flames.

Rad heat flux whrr stedaee ftefr n This parameter suggests if the horizontal radial

r isthehoriontl raialdistncedistance from the fire to the target is within the

r istehrznaIaildsac range of distances included in this V&V study.

1. See detailed description of normalized parameters and examples for additional information

A detailed description of the normalized parameters follows.

Heat Release Rate (HRR or 0): The most important parameter of any fire experiment is the

HRR. In some cases, the fire model is used to predict the HRR. Here, however, the HRR is

given, and the model is used to predict how the fire's energy is transported throughout the space

2-26
Technical Approach

of interest. A normalized quantity relating the HRR to the diameter of the fire, D, is commonly

known as*

Q

Where: Qis the heat release rate (kW),

p-~is the ambient density (kg/rn3 ),

T. is the ambient temperature (K),

CPis the specific heat of ambient air(kJ/kg-K),

g is the acceleration of gravity (mis 2), and

D is the diameter of the fire (in).

A large value of Qd describes a fire whose energy output is relatively large compared to its

physical diameter, like an oil well blowout fire. A low value describes a fire whose energy

output is relatively small compared to its diameter, like a brush fire. Most conventional

accidental fire scenarios have Qd values on the order of 1. Its relevance to the current validation

study is mainly in the assessment of flame height.

Example 1: An oil spill fire at floor level is postulated in a pump room. The scenario consists

of 3.8 L (1 gal) of oil spilled in an area of 5.3 mn2 (57.0 ft2). The target in this scenario is a cable

crossing the room near the ceiling. The height of the pump room is 7 mn (23.0 ft). Is the heat

release rate calculated for this scenario within the ranges of heat release rates included in the

V&V study? Assume that the heat of combustion for oil is 46,400 kJ/kg, and the mass loss rate is

0.036 kg/m2

-s (NUREG 1805, pp. 3-4).

The following steps are recommended to address this example:

1. Calculated the heat release rate of an 5.3 mn2 oil spill on fire:

MIT AHcff AdikeI -e-kflD) (0.036kg/rn 2 -s)(46,400KJ /kg)(5.3m 2)(1 e&(0.7*2.6))

Q7416kW

2. Calculate Qd

Q 7416kW

ý ~gD - (1.2kg Im3 )(lk.I kg .K)(293K) (.ims 2 )2m)(2.6m) ,

2

.Q=0.62

3. Compare Qdwith the corresponding values listed in Table 2-5.

The value of 0.62 is within the range of 0.4 - 2.4 listed in Table 2-5 for Q.

Room/Target Height: The quantities Qd and D* relate the fire's HRR to its physical

dimensions. The height of the compartment relative to D* indicates the relative importance of

the fire plume to the overall transport of the hot gases. Much of the mixing of fresh air and

2-27
Technical Approach

combustion products takes place within the plume, and this dilution of the smoke and the

decrease in the gas temperature ultimately determines the hot gas layer temperature. Thus, the

parameter HID * can be used to assess the importance of the plume relative to other features of

the fire-driven flow, like the ceiling jet or doorway flow. In this normalized parameter, H is the

target or ceiling elevation above the fire source and D* is defined as:

D Q _2/5

All variables are as defined above. The physical diameter of the fire is not always a well-defined

property. A typical compartment fire may not have a well-defined diameter, whereas a circular

pan filled with a burning liquid fuel has an obvious diameter. Fortunately, it is not the physical

diameter of the fire that matters when assessing the "size"~ of the fire, but rather a characteristic

diameter, D*.

In many instances, D* is comparable to the physical diameter of the fire (in which case Q,, is on

the order of 1). This group should be used when the fire scenario consists of a fire with a given

diameter. A good example application is the evaluation of validation results for unconfined oil

spill fire scenarios.

In summary, the HID * group is appropriate for evaluating applicability of validation results for

scenarios involving targets inside the fire plume.

Example 2: Using the information from Example 1, and assuming the cable is inside the fire

plume, is the target location in the fire plume within the range of locations considered in this

V&V report?

The following steps are recommended to address this example:

1. Calculate D* using the heat release rate from Example 1.

= ~ rg (1.2kg / M3 lkj /kg -K X293K ý9.81Im Is 2 25=24m

2. Calculate HID *

H = 7m =3.

D* 2.144m

3. Compare H/D* with the corresponding values listed in Table 2-5.

The value of 3.3 is not within the range of 3.6 - 16 listed in Table 2-5 for H/D*.

Ceiling Jet Radial Distance: For scenarios involving a target in the ceiling jet, it is important to

evaluate if the location of the target is within the range evaluated in this V&V study. The

parameter r,,j/H can be used for such evaluation. In this normalized parameter, rc is the

horizontal radial distance between the target and the centerline of the plume, and H is the vertical

distance from the base of the fire to the target.

Example 3: Using the information in Example 1, let's assume that the cable target is in the

ceiling jet, 2 mn (6.6 ft) away from the centerline of the fire plume. Determine if the target

location in the ceiling jet is within the locations included in this V&V report.

2-28
Technical Approach

1. Determine the r,, and H values from the information in Examples 1 & 3

rq,=2m H=7m

2. Calculate rj3/H

7ý m = 0.29

3. Compare rj3lH with the corresponding values listed in Table 2-5.

The value of 0.29 is not within the range of 1.2 - 1.7 listed in Table 2-5 for rq /H.

Radiative Heat Flux: The normalized parameter (Dlr) is recommended for determining if the

distance from a target to the flames is within the range of distances included in this V&V study.

This parameter results from the dimensionless point source model (XrQ*d)/(4(rID) 2 ). The Q*

term is removed since this is evaluated individually. This is important in scenarios involving

targets affected by flame radiation. In the normalized parameter (DIr)2 , D is the fire diameter,

and r is the horizontal distance from the targets to the flames.

Example 4: Using the information in Example 1, let's assume now that the cable target is in a

vertical cable tray along a wall 2 mn (6.6 ft) from the fire. The analyst is interested in

investigating if flame radiation in the lower layer can affect the cable tray. Determine if the

target location is within the locations included in this V&V report.

1. Determine the fire diameter from the information provided in Example 1

D = F 4 Adike (5-3m 2 ) = 2.5977 =2.6m Frad = 2m

7 3 .1 415

2. Calculate (DfradY

3. Compare (Dirrady) with the corresponding values listed in Table 2-5.

The value of 1.7 not within the range of 0.03 - 0.2 listed in Table 2-5 for D 2

Room Size: Many fire scenarios require the specification of room size as an input for estimating

fire-generated conditions inside an enclosure. The normalized parameters W/H and L/H can be

used for determnining if the room size in the scenario under evaluation is within the range of room

sizes considered in this study. W and L are room width and length respectively. H is the height

of the room.

Example 5: Continuing with Example 1, let's consider in this case that the cable tray is located

in the hot gas layer. The hot gas layer temperature needs to be calculated for determining if the

target may be damaged. The room is 8 mn long and 6 mn wide. Determine if the room size is

within the room sizes included in this study.

2-29
Technical Approach

1. Calculate W/H and L/H

W =6m =I L -_8m=1.

H 6m H 6m

2. Compare W/H and L/H with the corresponding values listed in Table 2-5.

Values are within range listed in Table 2-5 for W/ll and L/H.

Natural and Mechanical Ventilation: It is important to know whether a given compartment

fire is limited by its fuel supply or by its oxygen supply. In all six test series, the fuel supply was

specified as a test parameter. The oxygen supply was controlled either by the size of the

compartment opening or by the flow rate of the ventilation system. Although less precise, it is

possible to estimate the mass flow of oxygen for each test configuration. Where there is a door

to the compartment, an estimate of the maximum achievable oxygen supply is given as follows:

rho0 =O0.23 x 2 A.7

Where: mh0 2 is the mass flow of oxygen (kg/s),

A,, is the area of the opening (in),

h. is its height (in), and

0.23 is the mass fraction of oxygen in air.

Note that in many of the test series under consideration, this theoretical mass flow of oxygen was

not achieved because the fires were of short duration. However, the estimate is useful for this

exercise.

For an active ventilation system, the mass flow rate of oxygen is approximated by the following

equation:

0ho = 0.23 X PaiVJ

Where: Pair is the density of the air (kg/in 3), and

V is the ventilation rate (M3 /sec)

Of course, not all of the air supplied by the ventilation system would reach the fire, especially for

ceiling-mounted supply ducts.

The global equivalence ratio, 0, is the ratio of the mass flow of fuel to the mass flow of oxygen,

normalized by the stochiometric ratio. The estimated values of 0 in the table below are based on

the maximum fuel and oxygen flow rates for the given test series. The values are all less than

one, meaning that these fires would be characterized as well- or over-ventilated. The test with

the highest value of 0 is ICFMP BE #4, Test 1, which has an equivalence ratio of about 0.6.

It is also notable in that its HRR to volume ratio is about an order of magnitude larger than all the

other test series. Although still over-ventilated, the fire is relatively large with respect to its

compartment volume. All of the other fires could be characterized as relatively small with

respect to the compartment.

2-30
Technical Approach

Example 6: Using the information in Examples I and 5, let's assume now that the cable target is

in the hot gas layer, and the room is filled with smoke. The analyst is interested in investigating

if the ventilation conditions and amount of oxygen available for combustion in the room are

consistent with the conditions included in the V&V report. First, assume the room is naturally

ventilated with a normally opened door. Then, assume the room is mechanically ventilated with

8 air changes per hour.

1. Determine q0, Natural Ventilation parameter, assuming an opening of 2m x 2m

0 = 0 m,,in, =O0.23 x IAý ý§=O0.23 x I(4M2).I2--= 0.650

M, 0 (3100) 2 o2

7416kW_

O=(0.650)(1 3100)=0.7

2. Determine q0, Mechanical Ventilation parameter

(room parameters; H=7m, W=6m, L=8m)

M"0 = 0.23 x PairV 0.23(1.18kg/rn 3 )[(7m x.6m x 8m)(8ach) / 36001 = 0.2026kg /s

0 7416kW=2.

m,, -(13100) =(0.2026kg /s)(1 3 100)

3. Compare q5, Natural Ventilation and 0, Mechanical Ventilation with the

corresponding values listed in Table 2-5.

For the mechanical ventilation, the value of 2.8 is outside the range listed in Table 2-5.

In the natural ventilation case, the value is within the range listed Table 2.5.

2-31
Technical Approach

2.6.2 Characterization of Fire Model Predictions Based on Validation Results

Once the user determines the validation results reported here are applicable (see Section 2.6. 1),

the user must determine the predictive capability of the fire models. ASTM E 1355 does not

provide specific criteria by which to judge the predictive capability of the models based on the

results of the V&V. As such, the V&V project team developed a grading criteria and

methodology to judge the models' capabilities. The criteria the team used are described below.

The process of deducing the predictive capability of the model from the quantitative results is

documented in Volumes 3 through 7 of this report. Appendix A to each volume contains

detailed comparisons of model prediction and experimental measurements. Chapter 6 of these

volumes describes how these quantitative results were used to arrive at the characterization of

predictive capability of the model using the approach described below.

The following two criteria are used to characterize the predictive capability of the model:

Criterion 1: Are the physics of the model appropriate for the calculation being made? This

criterion reflects an evaluation of the underlying physics described by the model and the physics

of the fire scenario. Generally the scope of this study is limited to the fire scenarios that are

within the stated capability of the selected fire models (e.g., this study does not address the fire

scenarios that involve flame spread within single and multiple cable trays).

Criterion 2: Are there calculated relative differences outside the experimental and model input

uncertainty? This criterion is used as an indication of the accuracy of the model prediction.

Since fire experiments are used as a way of establishing confidence in model prediction,

the confidence can only be as good as our experiments and the model inputs derived from

experiments. Therefore, if model predictions fall within the ranges of these combined

uncertainties, the predictions are determined to be as accurate as the experiments and data.

2-32
Technical Approach

Section 2.6.3 and Volume 2 of this report series provide an introduction and technical details for

the uncertainty analysis.

The predictive capability of the model is characterized as follows based on the above criteria:

~ If both criteria are satisfied (i.e., the model physics are appropriate for the calculation

being made and the calculated relative differences are within or very near experimental

uncertainty), then the V&V team concluded that the fire model prediction is accurate for the

ranges of experiments in this study, and as described in Tables 2-4 and 2-5. A grade of GREEN

indicates the model can be used with confidence to calculate the specific attribute. The user

should recognize, however, that the accuracy of the model prediction is still somewhat uncertain

and for some attributes, such as smoke concentration and room pressure, these uncertainties may

be rather large. It is important to note that a grade of GREEN indicates validation only in the

parameter space defined by the test series used in this study; that is, when the model is used

within the ranges of the parameters defined by the experiments, it is validated.

EL L OW7 , If the first criterion is satisfied and the calculated relative differences are outside

the experimental uncertainty but indicate a consistent pattern of model over-prediction or underprediction, then the model predictive capability -is characterized as YELLOW+ for overprediction, and YELLOW- for under-prediction. The model prediction for the specific attribute

may be useful within the ranges of experiments in this study, and as described in Tables 2-4 and

2-5, but the users should use caution when interpreting the results of the model. A complete

understanding of model assumptions and scenario applicability to these V&V results is

necessary. The model may be used if the grade is YELLOW+ when the user ensures that model

over-prediction reflects conservatism. The user must exercise caution when using models with

capabilities described as YELLOW±.

EY, LLO : If the first criterion is satisfied and the calculated relative differences are outside

experimental uncertainty with no consistent pattern of over- or under-prediction, then the model

predictive capability is characterized as YELLOW. A YELLOW classification is also used

despite a consistent pattern of under- or over-prediction if the experimental data set is limited.

Caution should be exercised when using a fire model for predicting these attributes. In this case,

the user is referred to the details related to the experimental conditions and validation results

documented in Volumes 2 through 6. The user is advised to review and understand the model

assumptions and inputs, as well as the conditions and results to determine and justify the

appropriateness of the model prediction to the fire scenario for which it is being used.

7H :If th e first criterion is not met, then the particular fire model capability should not be

used.

No color: This V&V study did not investigate this capability. This may be attributable to one

or more reasons that include unavailability of appropriate data or lack of model, sub-model,

or output.

As suggested in the criteria above, there is a level of engineering judgment in the classification

of fire model predictive capabilities. Specifically, the V&V project team exercised engineering

judgment in the following two areas:

1. Evaluation of the modeling capabilities of the particular tool if the model physics are

appropriate.

2-33
Technical Approach

2. Evaluation of the magnitude of relative differences when compared to the experimental

.uncertainty. Judgment in this area impacts the determination of Green versus Yellow color.

The team included fire model developers, NPP fire modeling experts, and code 'users. In general,

a Green or Yellow classification suggests that the V&V team determined that the model physics

are appropriate for the calculation been made, within the assumptions of the specific model.

The difference between the colors is attributable to the magnitude of the calculated relative

differences. Judgment considerations include general experimental conditions, experimental

data quality, and the characterization of the experimental uncertainty.

2Z6.3 Uncertainty Analysis

The relati ve differences between experimental observations and model predictions are compared

in terms of a pre-determined combined uncertainty on which the validation results for each fire

modeling attribute are determined. This combined uncertainty includes the contribution of two

sources of uncertainty:

" Experimental uncertainty, which is the uncertainty associated with the measurement devices

in the'different experiments.

" Model input uncertainty, which refers to the uncertainty in the inputs to the model. Notice

that the inputs to the fire models, such as the heat release rate, are (for the most part)

measured parameters in the different experiments.

Consider a's an example, comparisons between measured and predicted values in terms of the

range of the combined uncertainty (scatter plot in Figure 2- 1Oa). If the models and experiments

were in perfect agreement, the data points would fall along the 450 line indicated in the figure.

The data in Figure 2- 1Oa are such that the models are in agreement with the experiments within

the bounds of the combined uncertainties. In contrast,. Figure 2-1lOb shows data in which the

models and experiments are not in agreement within the bounds of the combined uncertainties.

In this case, the comparison suggests that some aspect of the uncertainty was not captured by the

combined uncertainty value.

ALCombined Combined

uncertainty 0 'uncertainty

/ 0Line of Line of -,x perfect . ,'0 .- perfect

0 -- agreement V 0agreement

-(a) X,(b)

Experimental measurement Experimental measurement

Figure 2-10: Scatter plots depicting validation results in and out of the range of combined

uncertainty.

Volume 2 describes in detail the quantification of the combined uncertainty for each fire

modeling attribute.

2-34
3

RESULTS AND CONCLUSIONS

This chapter summarizes the results and findings of this V&V study. Section 3.1 presents the

results using the approach discussed in Section 2.6.2 of this volume. Readers should also review

Chapter 6 of Volumes 3 through 7 for more detailed discussions of the quantitative results.

In addition, Appendix A to each volume presents a graphical representation of the experimental

observations and outputs from the models.

Section 3.2 discusses observations concerning the results. These observations highlight patterns

and relationships between the results presented and experiments. Section 3.3 contains our

conclusion regarding our findings.

3.1 Results

3.1.1 Validation

Table 3-1 summarizes the results of this validation study. As discussed in Section 2.6.2, the

predictive capabilities of the models are graded based on the quantitative values of relative

difference between model prediction and experimental measurements.

The validation results show that none of the models have attributes that are RED. This is

because all the models appropriately represent the physics of the scenarios, within the

simplifying assumptions of the calculation method. Most of the correlations employed within

the models were empirically confirmed theoretical derivations of general physical phenomena,

as summarized in Chapter 3 of each volume. All of the relative differences that fell significantly

outside of the combined uncertainty could be explained in terms of the simplifying assumptions

within the models and the comparison of these assumptions with the experimental

configurations.

3-1
Results and Conclusions

Table 3-1: Results of the Validation & Verification of the Selected Fire Models for Nuclear Power Plant Fire Modeling

Applications

Celn e ePeramtere (target/gas

Smoke cocetato N/Agi YEELLOW N/Aow G ~LW

temeargtutemprtr"/)/ E..Q~ ;.~ LW

Radacant flux heat N/YELO YELLOW~~ YELW

Celigje tmertre("age/gsN/ ELLOW+ ELO W+j YELLWEN ' YLO

Totlum heaterfluxe N/AOW N/AOW YELWN/A~ ~O

t3A 7

Walle temperature N/A N/A ~YELLOW .1 YELLOW' ' YELLOWfl

3-2
Results and Conclusions

Notes:

1 . FDS does not use an empirical correlation to predict the flame height. Rather, it solves a set of equations appropriate for reacting flows

and predicts the flame height as the uppermost extent of the combustion zone. This is a challenging calculation and the Yellow

emphasizes that caution should be exercised by users.

2. FIVE approximates the experimental plume as the sum of hot gas layer temperature and the calculated plume temperature and

experimental ceiling jet temperature as the sum of hot gas layer temperature and the calculated ceiling jet temperature. The calculated

plume and ceiling jet temperatures were obtained from the correlations.

3. Flame height models compared with visual observations only.

4. Large experimental uncertainties for room pressure.

5. Refer to Table 2-3 for information about which experiments captured data for each parameter.

3-3
Results and Conclusions

3.1.2 Verification

All five models have been verified by this study as appropriate for fire protection applications,

within the assumptions for each individual model or sub-model. The project team used guidance

in ASTM E 1355 about the theoretical basis and mathematical and numerical robustness to make

this determination. The verification for each model is documented in Volumes 3 through 7.

During the process of this study, a n umber of modifications and corrections to the five selected

fire models were identified and implemented. These modification and corrections were

identified during the validation as a result of trying to interpret the results. The nature of these

modifications and corrections cover a wide range from inconsequential to those that could lead to

incorrect result. Descriptions of these modifications can be found in Volume 3 through 7.

3.2 Summary

This section presents a summary of observations from the results of this study. These

observations are based on review of these results and generally apply to the five fire models

considered in this study:

* The experiments considered in this study represent configurations that may be seen in NPP

applications. Not all possible NPP scenarios are evaluated in this study. We have evaluated

only those scenarios in which suitable experimental data is available. For a variety of

reasons, however, the experimental data is limited. Users should evaluate independently

whether the results of this study are applicable to their specific scenario. Table 2-5 provides

guidance in this matter.

* For the fire scenarios considered in the current validation study, and for the output quantities

of interest, the libraries of engineering calculations (FDTS, FIVE-Rev 1) have limited

capabilities. These libraries do not have appropriate methods for estimating many of the fire

scenario attributes evaluated in this study. The correlations that the libraries do contain are

typically empirically deduced from a broad database of experiments. The correlations are

based on funidamental conservation laws and have gained a considerable degree of

acceptance in the fire protection engineering community. However, because of their

empirical nature, they are subject to many limiting assumptions. The user must be cautious

when using these tools.

* The two-zone models performed well when compared with the experiments considered.

Evaluation of the two-zone models showed that the models simulated the experimental

results within experimental uncertainty (see Chapter 6 in Volume 2) for most of the

parameters of interest The reason for this may be that the relatively simple experimental

configurations selected for this study conform well to the simple two-layer assumption that is

the basis of these models. However, users must remain cautious when applying these models

to more complex scenarios, or when predicting certain phenomena, like heat fluxes.

* Evaluation of the FDS model showed that the model simulated the experimental results

within experimental uncertainty (see Chapter 6 in Volume 2) for most of the parameters of

interest. The results of the field model, FDS, are comparable to the results of the two-zone

models (CFAST, Volume 5, and MAGIC, Volume 6), probably because the experimental

3-4
Results and Conclusions

configurations utilized in this study contained, in most cases, two distinct layers within the

room of origin.

* The decision to use any of these models can depend on many considerations. Real fire

scenarios rarely conform neatly to some of the simplifying assumptions inherent in the

models. Although engineering calculations and two-zone models can be applied in instances

where the physical configuration is complex, their accuracy cannot be ensured. Field model

predictions can be more accurate in more these complex scenarios. However, the time it

takes to get and understand a prediction may also be an important consideration in the

decision to use a particular model for a specific scenario. FDS is computationally expensive

and, while the two-zone models produce answers in seconds to minutes, FDS provides

comparable answers in hours to days. FDS is better suited to predict fire environments

within more complex configurations because it predicts the local effects of a fire.

* Like all predictive models, the best predictions come with a clear understanding of the

limitations of the model and of the inputs provided to do the calculations. For calculation of

many attributes (see those attributes categorized as yellow in Table 3-2), caution should be

exercised when applying these models. For the attributes categorized as GREEN, the models

are accurate to within the experimental uncertainty associated with each particular attribute

(see Chapter 6 in Volume 2) for the range of conditions (see Table 2-5) represented by the

experiments used in this study.

3.3 Conclusions

This study provides justification for verification and provides validation via comparisons

between experimental data and predictions from five fire modeling tools. The validation results

of this study are presented in the form of color-coded grades of the predictive capability of fire

models for important parameters for NPP fire modeling applications. These grades are based on

the quantitative relative differences between model predictions and applicable experimental

measurements. The predictive capability considers the uncertainty in the experimental

measurements.

The use of fire models to support fire protection decision-making requires understanding of their

limitations and confidence in their predictive capabilities. This report improves the understanding

and evaluates the predictive capabilities of the models selected. Fully understanding the

predictive capabilities of fire models is a challenge that should be addressed if the fire protection

community is to realize the full benefit of fire modeling. The approach used in this study and

documented and implemented in the individual volumes can be used as a roadmap to model

users and developers for conducting a V&V for models other than those included in this study.

The results of this project clearly suggest that any fire modeling analysis should consider the

predictive capabilities associated with the analytical tool when interpreting its results.

3-5

4

REFERENCES

1. Performance-Based Standard for Fire Protection for Light- Water Reactor Electric

Generating Plants, NFPA 805, 2001 Edition, National Fire Protection Association,

Brainerd, MA, 200 1.

2. "Voluntary Fire Protection Requirements for Light-Water Reactors," 10 CFR Part 50,

Section 50.48(c), RIN 31 50-AG48, Federal Register, Volume 69, Number 115,

U.S. Nuclear Regulatory Commission, Washington, DC, June 16, 2004.

3. Memorandum of Understanding (MOU) on Cooperative Nuclear Safety Research

Between EPRI and NRC, Amendment on Fire Risk, U.S. Nuclear Regulatory

Commission, Washington, DC, Revision 1, 2001.

4. Standard Guide for Evaluating Predictive Capability of Deterministic Fire. Models,

ASTM E 13 55-05a, American Society for Testing and Materials, West Conshohocken,

PA, 2004.

5. Fire Modeling Guide for Nuclear Power Plant Applications, EPRI 100298 1,

Electric Power Research Institute, Palo Alto, CA, August 2002.

6. EPRI 1011989 and NUREG/CR-6850, "EPRI/NRC-RES Fire PRA Methodology for

Nuclear Power Facilities," U.S. Nuclear Regulatory Commission, Washington, DC,

August 2005.

7. NUREG-1805, "Fire Dynamics Tools (FDTS): Quantitative Fire Hazard Analysis Methods

for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program," U.S.

Nuclear Regulatory Commission, Washington, DC, December 2004.

8. Jones, W., R. Peacock, G. Forney, and P. Reneke, "CFAST: An Engineering Tool for

Estimating Fire and Smoke Transport, Version 5 - Technical Reference Guide," SP 1030,

National Institute of Standards and Technology, Gaithersburg, MD, 2004.

9. Gay, L., and C. Epiard, "MAGIC Software Version 4. 1. 1: Mathematical Model"

EDF H182/04/024/P, December 2004.

10. "Fire Dynamics Simulator (Version 4) Technical Reference Guide," K. McGrattan, ed.,

National Institute of Standards and Technology, Special Publication 10 18, 2004.

11. NUREG/CR-468 1, "Enclosure Environment Characterization Testing for the Base Line

Validation of Computer Fire Simulation Codes," U.S. Nuclear Regulatory Commission,

Washington, DC, March 1987.

12. NUREG/CR-53 84, "A Summary of Nuclear Power Plant Fire Safety Research at Sandia

National Laboratories, 1975-1987," U.S. Nuclear Regulatory Commission, Washington,

DC, December 1989.

4-1
References

13. NBSIR 88-3752, " An Experimental Data Set for the Accuracy Assessment of Room Fire

Models," National Bureau of Standards, April 1988

14. EPRI 108875, "Fire Modeling Code Comparison," Electric Power Research Institute,

Palo Alto, CA, September 1998.

15. Hostikka, S., M. Kokkala, and J. Vaani, "Experimental Study of the Localized Room

Fires," NFDC2 Test Series, VTT Research Notes 2104, 2001.

16. Hamins, A., A. Maranghides, E. Johnsson, M. Donnelly, J. Yang, G. Mulholland, and

R. Anleitner, Report of Experimental Results for the International Fire Model

Benchmarking and Validation Exercise #3, NIST Special Publication 10 13- 1,

National Institute of Standards and Technology, Gaithersburg, MD, 2005.

17. Klein-Healling, W., and M. R6wenkamp, Evaluation of Fire Models for Nuclear Power

Plant Applications: Fuel Pool Fire inside a Compartment, Gesellschaft fiir Anlagen-und

Reaktorsicherheit (GRS), K6ln, Germany, May 2005.

18. Hosser, D., 0. Riese, and M. Klingenberg, Performing of Recent Real Scale Cable Fire

Experiments and Presentation of the Results in the Frame of the International

Collaborative Fire Modeling Project ICFMP, Institut ffir Baustoffe, Massivbau und.

Brandschutz (iBMB), Braunschweig, Germany, June 2004.

19. Karlsson, B., and J.G. Quintiere, "Enclosure Fire Dynamics," CRC Press, Boca Raton,

FL, 2000.

20. Zukoski E.E., "Properties of Fire Plumes," Combustion Fundamentals of Fire, G. Cox,

ed., Academic Press, Burlington, MA, 1995.

4-2
NRC FORM 335 U.S. NUCLEAR REGULATORY COMMISSION 1. REPORT NUMBER

(9-2004) (Assigned by NRC, Add Vol., Supp.. Rev.,

NRCMD 3.7 and Addendum Numbers, if any.)

BIBLIOGRAPHIC DATA SHEET

(See instructions on the reverse) NUREG-1 824

2. TITLE AND SUBTITLE 3. DATE REPORT PUBLISHED

Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications MONTH YEAR

Volume 1: Main Report May 2007

4. FIN OR GRANT NUMBER

5. AUTHOR(S) 6. TYPE OF REPORT

B. Najafi (EPRI/SAIC), F. Joglar (EPRI/SAIC), J. Dreisbach (NRC) Te chnical

7. PERIOD COVERED (inclusive Dates)

8. PERFORMING ORGANIZATION - NAME AND ADDRESS (If NRC, provide Dhtiion, Of fice or Region, U.S. Nuclear Regulatory Commission, and mailing address; if contra ctor,

provide name and mailing address.)

U.S. Nuclear Regulatory Commission, Office of Regulatory Research (RES), Washington, DC 20555-0001

Electric Power Research Institute (EPRI), 3412 Hillview Avenue, Palo Alto, CA 94303

Science Applications International Corp. (SAIC), 4920 El Camino Real, Los Altos, CA 94022

National Institute of Standards and Technology (NIST/BFRL), 100 Bureau Drive, Stop 8600, Gaithersburg, MD 20899-8600

9. SPONSORING ORGANIZATION - NAME AND ADDRESS (If NRC. type 'Same as above'; if contractor, provide NRCIDivision, Office or Region, U.S. Nuclear Regulatory Commission,

and mailing address.)

U.S. Nuclear Regulatory Commission, Office of Regulatory Research (RES), Washington, DC 20555-0001

Electric Power Research Institute (EPRI), 3412 Hillview Avenue, Palo Alto, CA 94303

10. SUPPLEMENTARY NOTES

11. ABSTRACT (200 words or less)

There is a movement to introduce risk-informed and performance-base analyses into fire protection engineering practice, both

domestically and worldwide. The move towards risk-informed decision-making in nuclear power regulation was directed by the

U.S. Nuclear Regulatory Commission.

One key tool needed to support risk-informed, performance-based fire protection is the availability of verified and validated fire

models that can accurately predict the consequences of fires. Section 2.4.1.2. of NFPA 805, Performance- Base Standard for

Fire Protection for Light-Water Reactor Electric Generating Plants, 2001 Edition requires that only fire models acceptable to the

Authority Having Jurisdiction (AHJ) shall be used in fire modeling calculations. Futhermore, Sections 2.4.1.2.2. and 2.4.1.2.3.

of NFPA 805 state that fire models shall be applied within the limitations of the given model, and shall be verified and validated.

This report is the first effort to document the verification and validation (V&V) of five models that are commomnly used in nuclear

power plant applications. The project was performed in accordance with the guidelines that the American Society for Testing

and Materials (ASTM) set forth in ASTM E 1355, Standard Guide for Evaluating the Predictive capability of Deterministic Fire

Models. The results of this V&V are reported in the form of color codes describing the accuracies for the model predictions.

12. KEY wORDS/DESCRI PTORS (List words or phrases that will assist researchers in locating the report.) 13. AVAILABILITY STATEMENT

fire, fire modeling, verification, validation, performance-based, risk-informed, firehazards analyses, unlimited

V&V, FHA, CFAST, FDS, MAGIC, FIVE, FDTs 14. SECURITY CLASSIFICATION

(This Page)

unclassified

(This Report)

unclassified

15. NUMBER OF PAGES

16. PRICE

NFIC FORM 335 (9-2004) PRINTED ON RECYCLED PAPER
Federal Recycling Program
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EPRI 1011999

VERIFICATION AND VALIDATION OF SELECTED FIRE MODELS FOR

NUCLEAR POWER PLANT APPLICATIONS

.Volume 1: Main Report

MAY 2007

UNITED STATES

NUCLEAR REGULATORY COMMISSION

WASHINGTON, DC 20555-0001

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