FIRE MODELING FOR NUCLEAR ENGINEERING PROFESSIONALS

An Educational Program to Improve the Level of Teaching Risk-Informed,

Performance-based Fire Protection Engineering Assessment Methods

DJ Icove & AE RugglesDepartment of Nuclear Engineering 1

BACKGROUND• This three-day course is based on selected topics from

the U.S. Nuclear Regulatory Commission (NRC) Nuclear Power Plant Fire Modeling Application Guide (NPP FIRE MAG), implemented by NUREG-1934, 2nd Draft, issued July 2011.

• Your instructors are Dr. David J. Icove and Dr. Arthur E. Ruggles from the University of Tennessee, College of Engineering

• Partial funding for this initiative was through an NRC Nuclear Educational Curriculum Grant awarded in 2010 to the Nuclear Engineering Department, University of Tennessee

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COURSE SCHEDULE• Monday, August 8, 2011

– Introduction – Fire Dynamics Review

• Tuesday, August 9, 2011– Fire Modeling in Support of PRA– The Fire Modeling Process

• Wednesday, August 10, 2011– Fire Modeling Selection and Implementation– Handling Model Uncertainty

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1. INTRODUCTION

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1.1 Background

• In 2001, the National Fire Protection Association (NFPA) issued the first edition of NFPA 805, Performance-Based Standard for Fire Protection for Light-Water Reactor Electric Generating Plants

• 2010 is the latest Edition

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1.1 Background (Con’t)

• Effective July 16, 2004, the Nuclear Regulatory Commission (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 following a performance-based approach as an alternative to the existing deterministic fire protection requirements.

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1.1 Background (Con’t)• One important element in a performance-based

approach is the estimation of fire hazard using mathematical fire models.

• Fire modeling is one possible approach per NFPA 805, to demonstrate compliance with the regulatory requirements of 10 CFR 50.48(c).

• NFPA 805 also allows the use of a fire probabilistic risk assessment (Fire PRA) in regulatory applications. Fire modeling is used in Fire PRAs to determine the effects of fire hazard so that the associated risk can be quantified.

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1.1 Background (Con’t)• 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”

• Verification and Validation (V&V) of fire models ensures the correctness, suitability, and overall quality of the method. – Verification determines whether a model correctly represents

the developer’s conceptual description (whether it was “built” correctly)

– Validation determines whether a model is a suitable representation of the real world and is capable of reproducing phenomena of interest (whether the correct model was “built”).

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1.1 Background (Con’t)

• The NRC Advisory Commission on Reactor Safeguards recommended publication of NUREG-1824 (EPRI 1011999) user’s guide should include:– Estimates of the ranges of normalized parameters

to be expected in nuclear plant applications– Quantitative estimates of the uncertainties

associated with each model’s predictions, preferably in the form of probability distributions

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1.2 Objectives

• The objective of this guide (NUREG-1934) is to describe the process of properly conducting a fire modeling analysis principally for commercial Nuclear Power Plant (NPP) applications.

• This process addresses the selection and definition of fire scenarios, determination and implementation of input values, sensitivity analysis, uncertainty quantification, and documentation.

• This guide addresses guidance, recommended best practices, and example applications the requirements associated with fire modeling analyses per NFPA 805.

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1.3 Scope

• This guide should be used as a complement to, not a substitute for, “user’s manuals” for specific fire modeling tools, fire dynamics textbooks, technical references, education and training.

• Users are encouraged to review the references made throughout the guide for in-depth coverage of the advantages and the range of applicability of specific models or assumptions.

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1.3 Scope (Con’t)

• Once selecting a fire scenario, this guide will help the fire model user to define the necessary modeling parameters, select an appropriate model, and properly interpret the fire modeling results.

• Due to the technical nature of this guide, users with the following areas of expertise will benefit the most from it:– General knowledge of the behavior of compartment fires– General knowledge of basic engineering principles, specifically

thermodynamics, heat transfer, and fluid mechanics– Ability to understanding the basis of mathematical models

involving algebraic and differential equations• Users are cautioned that since all models are merely

approximations of reality, this guide also provides useful insights for translating real configurations into modeling scenarios.

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Common NPP Hazardous Fuels

• Combustible Solid Fuels– Cable insulation and pipe insulation– Building materials, combustible roof deck– Filtering, packing, and sealing materials– Low level radioactive wastes

• Combustible and Flammable Liquid Fuels– Lubricants, hydraulic oil, and control fuels

• Explosive and Flammable Gaseous Fuels– Hydrogen– Propane

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• Electrical cable insulation• Ordinary combustibles• Oil fire hazards in reactor

coolant pump motors, emergency turbine-driven feedwater pumps

• Diesel fuel fire hazards at diesel-driven generators

• Charcoal in filter units• Flammable off gases• Protective coatings

• Turbine lube oil and hydrogen seal oil

• Hydrogen cooling gas fire hazard in turbine generator buildings

• Fire hazards associated with electrical switchgear, motor control centers (MCCs), electrical cabinets, load centers, inverter, circuit boards, and transformers

Typical NPP Hazards

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NPP FIRE SCENARIOS

(NUREG 1824)

NPP Fire Scenarios (NUREG 1824)

• Switchgear Room• Cable Spreading

Room• Main Control Room• Pump Room• Turbine Building• Multi-Compartment

Corridor

• Multi-Level Building

• Containment Building

• Battery Room• Computer or Relay

Room• Outdoors

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Switchgear Room Fire

Cable Spreading Room Fire

Main Control Room Fire

Pump Room Fire

Turbine Building Fire

Multi-Compartment Corridor Fire

Multi-Level Building Fire

Containment Building Fire

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