ML18213A087

Joint EPRI/NRC-RES Fire PRA Workshop - Module III - Fire Analysis - Task 11a: Detailed Fire Modeling and Single Compartment Scenarios_2015

ML18213A087
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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 AnalysisTask 11a: Detailed Fire Modeling and Single Compartment ScenariosA Collaboration of the Electric Power Research Institute (EPRI) & U.S. NRC Office of Nuclear Regulatory Research (RES) 2ObjectivesDescribe the process of fire modeling for a single fire compartmentThe outcome of this activity is the extent and timing of fire damage within the compartment 3Module III: Fire ModelingRole and ScopeFire modeling:An approach for predicting various aspects of fire generated conditions

-Requires idealization and/or simplifications of the physical processes involved

-Departure of the fire system from this idealization can affect the accuracy and validityFire scenario: A set of elements representing a fire event

-Fire source/initiation

-Fire growth

-Fire propagation (room heating, HEAF, intervening combustibles, etc.)

-Active fire protection features, e.g., detection/suppression

-Passive fire protection features, e.g., fire stops

-Target sets (cables), habitability, etc.

4Module III: ProcessGeneral Task Structure 5Module III: ProcessCharacterize Fire CompartmentInformation on compartment geometry that can impact fire growth

-Size and shape, e.g., ceiling soffit or beam pocket

-Boundary construction and material

-VentilationFire protection systems and features

-Fixed detection systems

-Fixed fire suppression systems, water or gaseous

-Manual detection

-Fire brigade

-Internal fire barriers and stops, e.g., ERFBS 6Module III: ProcessIdentify/Characterize Ignition SourcesLocation within the compartment, type, size, initial intensity, growth behavior, severity/likelihood relationship, etc.Estimate frequency of ignition for the ignition source.Example of fire events involving typical ignition sources

-Oil or liquid spill fires (Characterization described in Appendix G)

-Oil or flammable liquid spray fires (Characterization described in Appendix G)

-General fires involving electrical panels (Characterization described in Appendices G, L & S)-High energy arcing faults events (Characterization described in Appendix M)

-Cable fires (Characterization described in Appendix R)

-Hydrogen fires (Characterization described in Appendix N)

-Transient fuel materials (Characterization described in Appendices G & S)

• Corresponding PRA Standard SR: FSS

-A1, FSS-C1 through C4 7Module III: ProcessIdentify/Characterize Secondary (Intervening) Combustibles May include, -Overhead raceways, -Cable air-drops, -Stored materials,-Electrical panels, -Construction materials, etc. The information provided should describe:

-Relative proximity of the secondary combustibles to the fire ignition source

-Configuration of the secondary combustible 8Module III: ProcessIdentify/Characterize Target SetsEach target set should be a subset of the fire PRA components and circuits (i.e., cables) present in the compartment

-Target sets associated to PRA components can be identified by examining the associated CCDP, once damaged component failure probabilities are set to 1.0

-Those subgroups with very small CCDP may be ignored as insignificant contributors to fire risk-Check for possibility of spurious actuations due to cable fires inside the compartment under analysis. Spurious actuations may generate the need of evaluating important scenariosFire modeling should have information on target location within the compartment available

-If complete routing information is not available, the analyst must justify target selection process and the corresponding impacts in the Fire PRA model

-Routing by exclusion OK (from a compartment, from a set of raceways-)Identify failure modes of equipment due to fire damage to the equipment or associated circuitsCorresponding PRA Standard SR: FSS

-A2 through A4 9Module III: ProcessSelect Fire ScenariosFire scenarios should take the following into consideration:

-Selected scenarios should reflect the objective of fire modeling, in this case impacting the components and circuits of interest to safety (targets)

-Selected scenarios should represent a complete set of fire conditions that are important to the objective

-Selected scenarios should challenge the conditions being estimated, e.g., scenarios that challenge habitability if manual action is of interest

-The list of postulated fire scenarios should include those involving fixed and transient ignition sourcesCorresponding PRA Standard SR: FSS

-A5 10Module III: ProcessSelect Fire Scenarios (cont'd)Approach to selection of fire scenarios is highly dependent on fire compartment hazard profile, i.e., location and amount of fire sources and combustibles and the location and number of potential targets. In general,-In compartments with few fire sources and many target sets (e.g., a switchgear room), start with an ignition source, postulate potential growth and propagation to other combustibles and then postulate damage to the closest target set that may be exposed to the specific fire

-In compartments with many fire sources and few potential targets (e.g., a PWR turbine building), start with potential target sets

-In compartments with many fire sources and many potential targets (e.g., a PWR auxiliary building), Nearby source/target combinations, andAlways include that fire scenario most likely (all factors considered) to cause wide

-spread damage (may be driven by fire source characteristics, fire spread potential, or by fire protection systems and features) 11Module III: ProcessConduct Fire Growth and Propagation Select fire modeling tool depending on the characteristics of each scenario

-Empirical rule sets

-Hand calculations

-Zone models

-Field modelsAnalyze fire growth and spread to secondary combustiblesEstimate resulting environmental conditionsEstimate time to target set damageCorresponding PRA Standard SRs: FSS

-C6, D1 through D6 12Fire ModelingFire modeling: an approach for predicting various aspects of fire generated conditions Compartment fire modeling: modeling fires inside a compartmentRequires an idealization and/or simplification of the physical processes involved in fire eventsAny departure of the fire system from this idealization can seriously affect the accuracy and validity of the approach 13Fire Modeling CapabilitiesAreas of application:Thermal effects of plumes, ceiling jets and flame radiationRoom heat up, and hot gas layerElevated fires and oxygen depletionMultiple firesMulti-compartments: corridors and multi-levelsSmoke generation and migrationPartial barriers and shieldsFire detectionSpecial models or areas for future research:Cable firesFire growth inside the main control boardFire propagation between control panelsHigh energy arcing fault firesFire suppressionHydrogen or liquid spray fires 14The Fire Modeling Process (NUREG

-1934/EPRI 1023259)Fire Modeling Process:

1)Define goals and objectives 2)Characterize the fire scenarios 3)Select fire models 4)Calculate fire

-generated conditions 5)Conduct sensitivity and uncertainty analyses 6)Document the analysis 15Fire ModelsHand calculations: Mathematical expressions that can be solved by hand with a relatively small computational effort

-Quasi steady conditions

-Usually semi

-empirical correlations developed with data from experimentsZone models: Algorithms that solve conservation equations for energy and mass in usually two control volumes with uniform propertiesField models: Algorithms that solve simplified versions of the Navier-Stokes equations. The room is divided into large number of cells and conservation equations are solved in each of them.Special models: There are fire scenarios critical to NPP applications that are beyond capability of existing computational fire models

-Fire experiments,-Operating experience, actual fire events

-Engineering judgment 16Hand CalculationsHeat release rate, flame height and flame radiationFire plume velocity, temperature heat flux, and entrainmentCeiling jet velocity, temperature, and heat fluxOverall room temperatureTarget temperature, and time to target damage 17Example of Hand Calcs: FDT sFDT sare a series of Microsoft Excel spreadsheets issued with NUREG-1805, "Quantitative Fire Hazard Analysis Methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program" The primary goal of FDT swas to be a training tool to teach NRC Fire Protection InspectorsThe secondary goal of FDT swas to be used in plant inspections and support other programs that required Fire Dynamics knowledge such as SDP and NFPA 805 18Module III: ProcessHand Calcs-NUREG-180502.1_Temperature_NV.xls02.2_Temperature_FV.xls02.3_Temperature_CC.xls03_HRR_Flame_Height_Burning_Duration_Calculation.xls04_Flame_Height_Calculations.xls05.1_Heat_Flux_Calculations_Wind_Free.xls05.2_Heat_Flux_Calculations_Wind.xls05.3_Thermal_Radiation_From_Hydrocarbon_Fireballs.xls06_Ignition_Time_Calculations.xls07_Cable_HRR_Calculations.xls08_Burning_Duration_Soild.xls09_Plume_Temperature_Calculations.xls09_Plume_Temperature_Calculations.xls10_Detector_Activation_Time.xls13_Compartment_ Flashover_Calculations.xls14_Compartment_Over_Pressure_Calculations.xls15_Explosion_Claculations.xls16_Battery_Room_Flammable_Gas_Conc.xls17.1_FR_Beams_Columns_Substitution_Correlation.xls17.2_FR_Beams_Columns_Quasi_Steady_State_Spray_Insulated.xls17.3_FR_Beams_Columns_Quasi_Steady_State_Board_Insulated.xls17.4_FR_Beams_Columns_Quasi_Steady_State_Uninsulated.xls18_Visibility_Through_Smoke.xls 19Module III: ProcessHand Calcs-NUREG-1805 20Module III: ProcessHand Calcs-FIVE-Rev2EPRI version of the fire modeling equations

-Very similar to NRC FDT SEPRI 3002000830, published in 2014

-Spreadsheet based

-Programmed in VBAContains most of the hand calculations in the original EPRI publication and some other models available in the fire protection engineering literature

-4 stage heat release rate profile based on t 2growth-Heskestad'sflame height model

-A radiation model from a cylindrical flame to targets

-Models for velocity of plume and ceiling jet flows

-Model for plume diameter as a function of height

-MQH model for room temperature

-Model for visibility through smoke 21Module III: ProcessHand Calcs-FIVE-Rev2 22Zone Models

• Two zones-Upper hot gas layer

-Lower layer with clear and colder air

• Mass and energy balance in the zones-Entrainment

-Natural flows in and out

-Forced flows in and out

• Fire is treated as a point of heat release 23Example of a Zone Model: MAGIC

-Gaseous phase combustion, governed by pyrolysis rate and oxygen availability

-Heat transfer between flame, gases and smoke, walls and surrounding air, thermal conduction in multi

-layer walls, obstacles to radiation-Mass flow transfer: Fire

-plumes, ceiling

-jet, openings and vents

-Thermal behavior of targets and cables

-Secondary source ignition, unburned gas management

-Multi-compartment, multi

-fire, etc.

Upper layer Vent Target Lower layer Horizontal opening Vertical opening Plume Flame Cables Obstacle Fan Duct Sprinkler system

24Specified LeakageHeptanePan FireLiquid spray fireDoorwayCable target locationsand directionsKerosenePan FireCompartmentVentControlledgas fireCeiling exhaust ventMechanical ventilationsupply 1.2 m below ceilingBurn room110 kW gasburner fireTarget roomCFAST 25MAGIC 26Field Models

• Solve a simplified form of the NavierStokes equations for low velocity flows*Calculation time in the order of hours, days or weeks*May help in modeling complex geometries 27Example of Field Model: FDSFire Dynamics SimulatorDeveloped and maintained by NIST 28 Fire Dynamics Simulator (FDS) 29Which Model to Choose?NUREG-1934 (EPRI 1023259)Hand calculations available

-Combustion

-Heat release rates, flame heights

-Fire generated conditions Plume temperatures and velocitiesCeiling jet temperatures and velocitiesFlow through ventsEnclosure temperatureTime and temperature to flashoverTarget temperature and time to target damage

-Heat transfer: irradiation from flames, plume and ceiling jet convective fluxAnalysts may need to go back and find additional parameters required 30Verification and Validation (NUREG

-1824/EPRI 1011999)Verification:the process of determining that the implementation of a calculation method accurately represents the developer's conceptual description of the calculation method and the solution to the calculation method. Is the Math right?Validation:the process of determining the degree to which a calculation method is an accurate representation of the real world from the perspective of the intended uses of the calculation method. Is the Physics right?See NUREG-1824 (EPRI 1011999) and Supplement 1 to NUREG-1824 (EPRI 3002002182) 31Verification and Validation (NUREG

-1824-Supplement 1) 32Verification and Validation (NUREG 1824 Supplement 1)Output Quantity Empirical Correlations CFAST MAGIC FDS Exp Corr. HGL Temp. Rise , Natural Ventilation MQH 1.1 7 0.15 1.21 0.3 8 1.1 3 0.3 3 1.0 2 0.07 0.07 HGL Temp. Rise , Forced Ventilation FPA 1.29 0.32 1.1 3 0.2 3 1.0 4 0.1 5 1.14 0.2 0 0.07 D B 1.18 0.2 5 HGL Temp. Rise , No Ventilation Beyler 1.04 0.37 0.9 9 0.24 1.0 7 0.16 1.16 0.1 1 0.07 HGL Depth ASET/YT - - 1.0 1 0.29 1.08 0.2 7 1.0 4 0.0 6 0.05 Ceiling Jet Temp. Rise Alpert 0.86 0.11 1.0 6 0.4 2 1.0 4 0.4 6 0.99 0.12 0.07 Plume Temp. Rise Heskestad 0.8 0 0.3 3 1.0 9 0.2 9 1.0 3 0.19 1.12 0.2 1 0.07 McCaffrey 0.90 0.3 1 Oxygen Concentration N/A 1.0 8 0.2 8 1.01 0.22 0.99 0.13 0.08 Smoke Concentration N/A 3.42 0.6 8 3.71 0.66 2.63 0.60 0.19 Pressure Rise N/A 1.3 7 0.6 3 1.3 2 0.20 1.00 0.2 3 0.2 3 Target Temp. Rise Steel 1.29 0.4 5 1.2 5 0.4 9 1.0 4 0.38 0.9 9 0.17 0.07 Target Heat Flux Point Source 1.39 0.50 1.04 0.59 0.8 5 0.6 6 0.9 7 0.2 6 0.11 Solid Flame 1.1 7 0.4 4 Surface Temp. Rise N/A 1.0 2 0.2 2 0.9 3 0.2 8 0.98 0.12 0.07 Surface Heat Flux N/A 0.9 4 0.2 6 0.7 6 0.3 3 0.89 0.1 7 0.11 Cable Failure Time THIEF 0.90 0.1 1 - - - - 1.1 0 0.1 6 0.12 Sprinkler Activation Time Sprinkler 1.11 0.41 1.01 0.2 0 0.9 1 0.20 0.9 3 0.1 5 0.06 Smoke Detector Act. Time Temp. Rise 1.07 0.5 8 1.77 0.3 9 1.4 4 0.3 8 1.22 0.34 0.34 33Module III: ProcessFire Detection/Suppression AnalysisAssess fire detection timingAssess timing, reliability, and effectiveness of fixed fire suppression systemsAssess manual fire brigade responseEstimate probability of fire suppression as a function of timeCorresponding PRA Standard SRs: FSS

-D6, D7, D8 34Module III: ProcessCalculate Severity FactorThe time to target damage, and as a result the non

-suppression probability, is a function of the postulated heat release rateThe severity factor should be calculated in combination with the non-suppression probabilityCorresponding PRA Standard SRs: FSS

-C4, D5 35Use of Special ModelsThere are fire scenarios critical to NPP applications that are beyond capability of existing computational fire models

-Cable fires-High energy arcing faults and fires

-Fire growth inside the main control board

-Fire propagation between control panels

-The methods described here are documented in EPRI 1011989 & NUREG/CR-6850, "EPRI/NRC

-RES Fire PRA Methodology for Nuclear Power Facilities."

36Module III: ProcessDocument Analysis ResultsThe first tier documentation should be sufficient in detail to allow for an independent reader to understand

-Scenarios postulated, the basis for their selection and analysis,-The tools utilized in the analysis and basis for selection, -The final results of the analysisThe second tier documentation should provide the details of each individual analysis performed including:

-Details of scenario selection process, -The fire modeling analyses performedAll specific considerations and assumptions should be recorded clearly