ML18213A077

Joint EPRI/NRC-RES Fire PRA Workshop - Module Iii - Fire Analysis -Fire Fundamentals Compartment Fires

ML18213A077
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Issue date:	07/31/2018
From:	Tammie Rivera NRC/RES/DRA/FRB, Electric Power Research Institute
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Joint EPRI/NRC

-RES Fire PRA WorkshopAugust 6-10, 2018Module III

-Fire AnalysisFire Fundamentals Compartment FiresA Collaboration of the Electric Power Research Institute (EPRI) & U.S. NRC Office of Nuclear Regulatory Research (RES) 2OutlineCompartment fire dynamics

-qualitative descriptionPressure profiles and vent flowsThe hot gas layerHeat transfer Combustion products 3Qualitative DescriptionCeiling JetPlumeSmoke LayerFigure 2.1: Overview of enclosure fire processesExtraction System(e.g., smoke purge system)Injection System(e.g., HVAC) 4Phases in a Compartment FireIgnition: Process that initiates an exothermic combustion reaction-Piloted or auto (spontaneous) ignition

-Accompanying process can be flaming or smoldering combustionGrowth-Can occur at different rates depending on type of fuel, interactions with surroundings, and access to oxygenHot gas layer buildup and room heat

-upFlashover: Rapid transition to a state of total surface involvement of combustible materials within an enclosure

-Temperatures between 500

°C (930°F) to 600°C (1,110°F), or-Heat fluxes between 15 kW/m 2to 20 kW/m 2

5Phases in a Compartment FireFully developed fire: The energy released in the enclosure is at its greatest level and is very often limited by the available oxygen-Gas temperatures between 700

°C (1,300°F) and 1200

°C (2,200°F)Decay: Fuel becomes consumed, fire intensity decreases

-Hazard indicators (temperature and heat fluxes) start to decrease Other terminology may include

-Pre-flashover fireFocus on life safety and sensitive targets In NPP, cables damage at 218°C (424°F) for thermoplastic cables and 330°C (626°F) for thermoset cables Main focus of NPP analysis

-Post-flashover fire: Focus in structural stability and safety of firefightersNot generally an issue for NPP applications 6Compartment Fires 7Compartment Fires 8Sense of Scale 9Pressure Profiles & Vent FlowsPressurePressurePressure Z Z+++-ambambamb H o H o H o H H H Z 10Pressure Profiles & Vent Flowsgh P h P o o o0Zu h ggZu P h P u o i i 0h Zu g Zu h g P h P u o i o i 0Outside ProfileInside ProfileP Profile Z+-amb H o H Z u 11Pressure Profiles & Vent FlowsUnderPressurized InOutp i-o(0)NormalOut Inp i-o(0)OverPressurizedOut Inp i-o(0) 12Hot Gas Layer or Smoke LayerAccumulation of hot gases in the upper part of the roomMass: entrainment (~90%) and combustion products (~10%)Volume: entrainment, combustion products, and expansion due to energy addedTemperature rise: expansion generates a larger volume than corresponding mass resulting in lower gas densities.Conservation of mass and energy 13Hot Gas or Smoke LayerSimulation ResultsUpper Layer Height 00.5 11.5 22.5 33.5 44.5 0 200 400 600 800 1000 1200Time [Sec]

[m]MAGICCFASTDataRoom size:

-22 x 7 x 3.7 mFire: ~1 MWDoor: 2 x 2 m 14Hot Gas or Smoke LayerConservation of Mass

-Rate of change of mass in the control volumeAccumulation

-Mass flow through the control surfacePlume flowSupply and exhaust systemsFlow through doors and windows 15Heat Transfer-To walls-Convection and radiation

-Conduction losses-To targets

-Convection and radiationHeat losses from the compartment include:

-Conduction through walls

-Convection (gas flow) and radiation escaping through openings and vents 16Heat TransferConductionConvectionRadiation