0 5 10 15 20 25 30 35 40 0 30 60 90 120 150 180 210 240 270 300 330 360 390 Number of Tests Peak HRR (kW) 139 tests < 10 kW 0 1 2 3 4 5 6 7 8 9 10 400 550 700 850 1000 1150 1300 1450 1600 1750 1900 2050 2200 2350 2500 2650 Number of Tests Peak HRR (kW) 0 5 10 15 20 25 30 35 40 0 10 20 30 40 50 60 70 80 90 100 Number of Tests Total Energy Release (MJ) 166 tests < 5 MJ 0 1 2 3 4 5 6 7 8 9 10 100 140 180 220 260 300 340 380 420 460 500 540 580 620 660 700 Number of Tests Total Energy Release (MJ) 0 10 20 30 40 50 60 10 100 1000 10000 Heat of Combustion (MJ/kg) Peak HRR (kW) Cellulosic Mixed Other Thermoplastic 0 0.5 1 1.5 2 2.5 3 3.5 4 10 100 1000 10000 Q* Peak HRR (kW) Cellulosic Mixed Other Thermoplastic 0 0.05 0.1 0.15 0.2 10 100 1000 10000 CO Yield (kg CO/kg fuel) Peak HRR (kW) Cellulosic Mixed Other Thermoplastic 0 0.02 0.04 0.06 0.08 0.1 0.12 0.14 10 100 1000 10000 Soot Yield (kg soot/kg fuel) Peak HRR (kW) Cellulosic Mixed Other Thermoplastic 0 5 10 15 0 500 1000 1500 HRR (kW) Time (s) Single Rag 5 Rags Bag of 10 Rags 0 10 20 30 40 50 0 200 400 600 HRR (kW) Time (s) Single Rag 5 Rags 0 5 10 15 20 0 1000 2000 3000 4000 5000 HRR (kW) Time (s) Repeat 1 Repeat 2 Repeat 3 0 10 20 30 40 50 60 70 0 500 1000 1500 2000 2500 3000 3500 HRR (kW) Time (s) Repeat 1 Repeat 2 Repeat 3 0 20 40 60 80 100 0 700 1400 2100 2800 3500 HRR (kW) Time (s) Draped 1 Draped 2 Folded 0 50 100 150 200 0 800 1600 2400 3200 4000 HRR (kW) Time (s) Draped 1 Draped 2 Folded 0 20 40 60 80 0 900 1800 2700 3600 4500 HRR (kW) Time (s) Repeat 1 Repeat 2 Repeat 3 0 5 10 15 20 25 30 0 900 1800 2700 3600 4500 HRR (kW) Time (s) Repeat 1 Repeat 2 Repeat 3 0 20 40 60 80 100 0 500 1000 1500 HRR (kW) Time (s) Quarter Full Half Full Full 0 50 100 150 200 250 300 350 0 500 1000 1500 2000 2500 HRR (kW) Time (s) Quarter Full Half Full Full 0 100 200 300 400 500 600 700 0 100 200 300 HRR (kW) Time (s) Empty w/Peanuts w/Paper 0 50 100 150 0 100 200 300 HRR (kW) Time (s) Empty w/Peanuts w/Paper 0 10 20 30 40 50 60 70 0 100 200 300 HRR (kW) Time (s) Empty w/Peanuts w/Paper THE MEASURED HEAT RELEASE RATES OF TRANSIENT FUEL ITEMS FOUND IN NUCLEAR POWER PLANTS Jason Floyd and Matthew DiDomizio, Jensen Hughes, USA Kevin McGrattan and Matthew Bundy, National Institute of Standards and Technology, USA Marko Randelovic and Ashley Lindeman, Electric Power Research Institute, USA Interflam 2019 – July 2019 Hot Gas Layer (HGL) Model (typically CFAST) to determine damage Fire Modeling for PRA * in a Nutshell 1 Cable Trays (Targets) Zone of Influence (ZOI) Maximum distance where plume temperature or radiative flux can cause damage In ZOI = damaged Not in ZOI or HGL = undamaged In HGL = ? Transient Fires in PRA 2 PRA Realism 3 A transient fire is a fire that results from combustible materials not fixed in place like a motor, transformer, or electrical cabinet. A transient fire could occur anywhere that there is a surface where transient materials could be placed. The current recommended approach on treating transient fires is contained in NUREG/CR-6850 and NUREG/CR-6850 Supplement 1. The recommendation is that transient fires are represented by a gamma distribution with a 75 th percentile HRR of 142 kW and a 98 th percentile HRR of 317 kW with a growth rate of 2 minutes (unconfined) or 8 minutes (confined – e.g. trash can). In a PRA, transient fires are typically the number two or three source of fire risk in a nuclear power plant. At first fire PRAs were used for NFPA 805, to demonstrate that a plant met an overall limit on core damage frequency. It was recognized that conservatisms in the PRAs existed, but they were tolerated since plants were still able to meet risk targets. * PRA = probabilistic risk assessment Now PRAs are being used for risk informed maintenance activities. All plants have technical specifications which define minimum amounts of safety equipment that must be operational. If a plant drops below this it must go offline. For some equipment a brief time period for repair is allowed. Being offline can mean $1,000,000 a day or more in lost revenue. Technical specification times originated long before PRAs and were largely based on expert judgement. A plant can get a longer time for repair if the PRA shows the risk is small. PRA conservatism makes this more difficult. This has resulted in a number of research efforts to improve realism in fire PRAs. The Realism Issue 4 Project Outline 5 Ignition and Fuels 6 Phase 1: Burn fuel packages representative of transient fire events in the Fire Events Database (FEDB). • 290 tests of 99 fuel package were done using a 100 kW calorimeter at Jensen Hughes in Baltimore, MD USA (EPRI funded tests) and the 1 and 3 MW calorimeters at the National Institute of Standards and Technology in Gaithersburg, MD USA (US Nuclear Regulatory Commission [NRC] funded tests). Fires burned without intervention until there was no visible flame. • Ignition sources were selected to be representative of the strength and duration of those in FEDB events. Phase 2 (Future Work): Using the FEDB transient fire events, weight the test data and generate new gamma distributions for HRR and ZOI plus guidance on how to model the time-dependence of a transient fire. • Butane lighter – fast igniting fuels • Nylon wick – 6 cm x 1 cm nylon rope with 5 mL of heptane • Continuous flame – ~100 W propane flame from 0.5 cm tubing • Radiant panel – 15 cm x 25 cm panel at 30+ kW/m 2 representing a halogen work light. Cotton rags, paper, cardboard boxes, duct tape, tarps, debris piles, plastic buckets, vacuums, trash bags, mop+bucket, rope, plastic chain, power cords, safety cones and chain stanchions, plastic tubing, canvas tool bag with tools, wood scaffolding and pallets, laptop computer, tablet computer. Flammable liquids in plastic bottles, oil absorbing pads, tablet computer, temperature ventilation ducts The 317 kW 98 th percentile heat release rate is based on a set of 27 experiments from the literature at the time NUREG/CR- 6850 was being written. Some of the experiments contain fuel items not typically found in risk significant areas of a plant. As a whole, the set of experiments appear to be more severe than operational experience (all plants report fire events to a centralized database maintained by EPRI). A typical cable tray arrangement is for trays to run 0.3 to 0.6 m above electrical cabinets that are 1.8 to 2.1 m tall. This is within the ZOI of a 317 kW fire. This suggests that not only does the guidance lack realism (not matching operational experience) but it is also likely resulting in significant conservatisms in fire PRAs. For each fuel type there were multiple configurations and repeat tests. Peak HRR and Total MJ 7 Fire Characteristics 8 Cardboard Boxes 9 Trash Cans 10 Plastic Cart w/ Laptop 11 Rope/Hose 12 Safety Cone/Stanchion 13 Plastic Tarps 14 Cotton Rags 15 Medium Empty Box 15.2 m of 2.5 cm Nylon Rope 15.2 m of 1.9 cm Vinyl Water Hose Fire Resistant Tarp Non-Fire Resistant Tarp Dry Cotton Rags Cotton Rags w/5 mL Heptane Per Rag Stack of Four 23 cm Tall Plastic Safety Cone 102 cm Tall Plastic Chain Stanchion 0.11 m 3 Metal Trash Can 0.13 m 3 PE Trash Can Cans have PE bag, plastic water bottles (empty), paper Laptop, 3-ring Binder w/paper, and printer on two-shelf plastic work cart Small (0.006 m 3 ) Medium (0.03 m 3 ) Large (0.2 m 3 ) 0 500 1000 1500 2000 2500 3000 0 2000 4000 6000 HRR (kW) Time (s) Repeat 1 Repeat 2 Repeat 3 This test represents the worst transient fire event in the FEDB Test data will be published as a joint EPRI/NRC report (NUREG) This project was sponsored by the Electric Power Research Institute © 2019 Jensen Hughes, Inc. All rights reserved. Tests ≤ 400 kW Tests > 400 kW Tests ≤ 100 MJ Tests > 100 MJ