FIRE DYNAMICS TOOLS

1. FIRE DYNAMICS TOOLS An Educational Program to Improve the Level of Teaching Risk-Informed, Performance-based Fire Protection Engineering Assessment Methods

2. RESOURCES PROVIDED • All Participants will be given at the end of the course, a CD-ROM containing: • Handouts and visuals used in presentations • Reference materials, real-world example FHAs, and the latest version of FDTs • “Fire Dynamics Tools (FDT s) Quantitative Fire Hazard Analysis Methods for the U.S. Nuclear Regulatory Commission Fire Protection Inspection Program,” (NUREG-1805.1, June 2005). • “Verification and Validation of Selected Fire Models for Nuclear Power Plant Applications,” (NUREG-1824/EPRI 1011999, May 2007)

3. INTRODUCTION

4. INTRODUCTION • The U.S. Nuclear Regulatory Commission (NRC) has developed quantitative methods, known as the Fire Dynamics Tools (FDTs) to assist in performing Fire Hazard Analyses (FHAs) known as NUREG 1805. • This methodology has been implemented in Exceltm spreadsheets • The goal of this effort is to provide first-order calculations of potential postulated scenarios at nuclear power plants.

5. OBJECTIVES • Provide basic calculation methodology for use in assessing potential fire hazards in NRC-licensed nuclear power plants (NPPs). • The methodology uses simplified fire hazard analysis (FHA) techniques for credible fire scenarios. • The FDTs spreadsheets are designed to incorporated empirical correlations and mathematical calculations based upon fire dynamics principles.

6. REGULATORY BACKGROUND • “General Requirements” in Appendix R (10 CFR 50) states a fire protection program shall: • Prevent fires from starting • Rapidly detect, control, and extinguish fires that do occur • Protect structures, systems, and components

7. REGULATORY OBJECTIVES • FHAs for Nuclear Power Plants should: • Consider the potential for transient fire hazards • Determine the consequences of fire in any location in the plant • Pay attention to safe reactor shutdown while minimizing the chances for radioactive material releases • Specify measures for fire detection, suppression, containment, and prevention.

8. COMMON NPP FIRE HAZARDS • 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

9. TYPICAL FIRE HAZARDS 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 • 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

10. NPP FIRE SCENARIOS(NUREG 1824)

11. NPP 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

12. SWITCHGEAR ROOM FIRE

13. CABLE SPREADING ROOM FIRE

14. MAIN CONTROL ROOM FIRE

15. PUMP ROOM FIRE

16. TURBINE BUILDING ROOM FIRE

17. MULTI-COMP. CORRIDOR FIRE

18. MULTI-LEVEL BUILDING FIRE

19. CONTAINMENT BUILDING FIRE

20. FHAs USING FIRE MODELS

21. FHAs USING FIRE MODELS • FHAs of NPPs are typically assisted using fire models. • Three useful classes of fire models exist (Ref: NIST, RIC 2007):

22. FIRE MODELING OUTPUTS

23. FIRE MODELING PARAMETERS • (1) Hot gas layer temperature: This temperature is particularly important in NPP fire scenarios because it can provide an indication of target damage away from the ignition source. Models predict the increase in environmental temperature attributable to the energy released by a fire in a volume.

24. FIRE MODELING PARAMETERS • (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.

25. FIRE MODELING PARAMETERS • (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.

26. FIRE MODELING PARAMETERS • (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.

27. FIRE MODELING PARAMETERS • (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.

28. FIRE MODELING PARAMETERS • (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.

29. FIRE MODELING PARAMETERS • (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.

30. FIRE MODELING PARAMETERS • (8) Total heat flux to walls: This attribute evaluates 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 heat up, it can be an important factor in the heat balance in control volume(s) in contact with the surfaces.

31. FIRE MODELING PARAMETERS • (9) Wall temperature: This attribute was included as a separate attribute in this study to evaluate model capabilities to determine the temperature of walls, floors, and ceilings.

32. FIRE MODELING PARAMETERS • (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 fire induced conditions in the room.

33. FIRE MODELING PARAMETERS • (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).

34. FIRE MODELING PARAMETERS • (12) Oxygen concentration: This 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.

35. FIRE MODELING PARAMETERS • (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.

36. HAZARD METHODOLOGY • Tier A – Material Properties • A1 – (08) Burning duration of solids • A2 – (07) Heat Release Rate of cable tray fires • A3 – (03) Burning characteristics of liquid pool fires (HRR, burning duration, flame height)

37. HAZARD METHODOLOGY • Tier B – Plume Development • B1 – (09) Center line temperature of a fire plume • B2 – (04) Flame height calculations (wall, line, corner) • B3 – (05) Estimate radiant heat flux to target fuel • B4 – (06) Ignition temperature of a target fuel

38. HAZARD METHODOLOGY • Tier C – Compartment Factors • C1 – (02) Prediction of hot gas layer temperature • C2 – (10, 11, 12) Estimating detector/sprinkler response times • C3 – (13) Predicting compartment flashover • C4 – (14, 15) Predicting pressure rise in closed compartment, explosion pressure • C5 – (16) Predicting rate of hydrogen gas generation • C 6 – (17) Calculating fire resistance of structural members

39. HAZARD METHODOLOGY • Tier D – Tenability (Hazard Criteria) • D1 – (18) Estimating visibility through smoke • D2 – Heat release rate • D3 – Radiant heat exposure (2.5 kW/m2) • D4 – Layer temperature (100oC) • D5 – Layer smoke density (0.2/m) • D6 – Layer Carbon Monoxide (3,000 ppm) • D7 – Layer Oxygen (10 percent or less)

40. RECENT STUDIES • “Comparison of Three Fire Models in the Simulation of Accidental Fires,”G. Rein, A. Bar-Ilan, and A.C. Fernandez-Pello, University of California at Berkeley; and N. Alvares, Fire Sciences Applications, San Carlos, California, 2004. • Study applied and compared the predictive capabilities of Analytical, CFAST Zone, and FDS Field Models to three accidental fires • Findings were these three models produced results in relatively good agreement, particularly in early stages of fire development

41. ACCURACY OF FIRE MODELS • NUREG 1824 • Analysis

42. ACCURACY OF FIRE MODELS • NUREG 1824 Analysis

43. FIRE DYNAMICS TOOLS(Tier A)

44. HAZARD METHODOLOGY • Tier A – Material Properties • A1 – (08) Burning duration of solids • A2 – (07) Heat Release Rate of cable tray fires • A3 – (03) Burning characteristics of liquid pool fires (HRR, burning duration, flame height)

45. ESTIMATING BURNING DURATION OF SOLID COMBUSTIBLES (NUREG 1805 -Chap 8) 08_Burning_Duration_Solid.xls

46. OBJECTIVES • ESTIMATING BURNING DURATION OF SOLID COMBUSTIBLES • Introduce factors that influence the fire duration of solid combustibles. • Explain how to estimate fire durations for various solid combustibles. • Approximate first order estimates of burning durations.

47. BURNING DURATION • The burning duration is the time between ignition and the decay phase of a fire. • The burning duration (fire) for a given compartment size and ventilation condition is driven by the fuel load. • Given the mass of material being burned per second and the amount of material available to be consumed, it is possible to calculate a first order estimate for the total burning duration of a fuel.

48. BURNING DURATION • The burning duration of solid combustibles can be estimated if the HRR and total energy contained in the fuel are known.

49. ASSUMPTIONS/LIMITATIONS • (1) Combustion is incomplete (leaving some residual fuel) and takes place entirely within the confines of the compartment. • (2) Virtually all of the potential energy in the fuel is released in the involved compartment.

50. INPUT NEEDED • (1) fuel type (material) • (2) mass of solid fuel • (3) exposed fuel surface area