ML18277A205
| ML18277A205 | |
| Person / Time | |
|---|---|
| Issue date: | 10/04/2018 |
| From: | Office of Nuclear Reactor Regulation |
| To: | |
| Mehta S | |
| Shared Package | |
| ML18277A208 | List: |
| References | |
| Download: ML18277A205 (9) | |
Text
FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Plant: Various Date: August 22, 2018
Contact:
Robert Cavedo Phone: (301) 938-0397 Mark Schairer (508) 532-7137 Patricia Pringle (410) 495-4496 Ashley Lindeman (704) 595-2538 Travis Weber (508)532-7141 Email: Robert.cavedo@exeloncorp.com mvs@epm-inc.com patricia.pringle@exeloncorp.com alindeman@epri.com tjw@epm-inc.com Distribution: (NEI Internal Use)
FPRA TF BWROG PWROG Purpose of FAQ:
Using NUREG/CR-6850 Supplement 1 Section 17, Appendix A, and Appendix B data, this FAQ provides recommended steady state burn durations and decay durations for the standard transient packages.
Relevant NRC document(s):
NUREG/CR-6850 Supplement 1 (FAQ 08-0052)
Details:
NRC document needing interpretation (include document number and title, section, paragraph, and line numbers as applicable):
NUREG/CR-6850 Supplement 1 Section 17 (FAQ 08-0052)
Circumstances requiring interpretation or new guidance:
The guidance in NUREG/CR-6850 Supplement 1 Section 17 (FAQ 08-0052) specifies growth rates for typical transient packages but doesnt specify a steady state burn duration or decay rate.
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FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Detail contentious points if licensee and NRC have not reached consensus on the facts and circumstances:
None.
Potentially relevant existing FAQ numbers:
FAQ 08-0052 Response Section:
Proposed resolution of FAQ and the basis for the proposal:
The guidance in NUREG/CR-6850 Supplement 1 Section 17 (FAQ 08-0052) does provide the basis for the growth rate in Appendices A and B. This includes several complete heat release rate (HRR) growth profiles. These same profiles are used to estimate the steady state burn duration and decay portions of the curve.
The risk contribution of transient scenarios is a function of the peak heat release rate and the total energy deposited from the fire. As the NUREG/CR-6850 guidance already provides the peak HRR (317 kW Table G-1), the burn durations and decay profiles should be related to the energy deposited by the fire. This is estimated by discretizing the HRR curves in the NUREG/CR-6850 Supplement 1 Appendices A and B to assign a MJ total energy deposited for each curve. The development for these curves is contained in Attachment 1 of this FAQ. Per NUREG/CR-68050 Supplement 1 the LBL fires are discounted as not being typical of nuclear power plant applications. Here is the summary chart of the bounding MJs released for each HRR test group.
Table 1 Summary of NUREG/CR-6850 Supplement 1 Appendices A and B HRR MJ Released Total Energy
- Test [MJ]
A-1 NUREG/CR-4680 test 7, small trash can fire 33.5 A-2 NUREG/CR-4680 test 8, small trash can fire 74.3 A-3 NUREG/CR-4680 test 9, large trash can fire 239 B-3 The heat release rate profile from SNL test 5 involving fuel package 3 15.2 Page 2 of 9
FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Based on the already defined t-squared growth rates, a 317 kW transient fire proposed in NUREG/CR-6850 uses 12.7 MJ for the uncontained 2 minute growth rate and 50.7 MJ for the 8 minute growth rate. The integral of t-squared is t-cubed/3. As the equations is divided by t-squared, the integrated energy for a t-squared growth is T/3.
12.7 MJ = 317 kW
- 120 seconds / 3 / 1000 kJ/MJ 50.7 MJ = 317 kW
- 480 seconds / 3 / 1000 kJ/MJ If the remaining energy is assigned directly to the steady state burn duration, then the remaining burn durations for each test would be:
Table 2 Maximum Steady Burn Duration given Conservation of Test Energies Non-Contained Fires Contained Fires (time in minutes) (time in minutes)
MJ Used Total HRR Growth MJ Used in Steady Growth in Steady
- MJ kw mins Growth mins mins Growth mins A-1 33.5 317 N/A N/A N/A 8 50.7 0 A-2 74.3 317 N/A N/A N/A 8 50.7 0.2 A-3 239 317 N/A N/A N/A 8 50.7 8.8 B-3 15.2 317 2 12.7 0 N/A N/A 0 This provides a range of steady state burn durations from 0 minutes to 9 minutes. Although not representative of the physical fire phemonon, the total energy released is a key metric in fire risk analysis. It is worth noting the bounding values in the context of how the HRR growth profile will be used.
NUREG/CR-6850 Appendix G provides a complete growth curve for a typical electrical cabinet:
12 minutes t-squared growth, 8 minutes peak burn, and 19 minutes linear decay.
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FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve If these same ratios were applied to transient scenarios the resultant growth curves would be:
Table 3 Transient Growths Ratios from Electrical Cabinet Growth Transient Electrical mins 2-min 8-min t-Squared 12 2 8 Peak 8 1.3 5.3 Linear Decay 19 3.2 12.7 The final piece of data is the peak burn durations and decay time from the NUREG/CR-6850 Supplement 1 Appendices A and B tests. This is summarized as:
Table 4 NUREG/CR-6850 Supplement 1 Appendices A and B tests Total
- MJ Peak Decay 1 33.5 40 15 2 74.3 50 15 3 239 10 50 7 15.2 4 12 This shows a wide range of peak burn durations and decay times. The combination of this information should be done to ensure realistic modeling of transient fires. As peak HRR is already covered by existing guidance, the total amount of energy released should be the main driver in the establishment of the full growth profile.
In general, the peak heat release rate will be shorter than the growth, but to persevere the energy deposited the 2- min transient fire is considered to be twice as long as the peak time. The 8-minute transient fire is 2/3 of the peak time. The linear decay times are considered to be double the peak times.
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FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Table 5 Recommend Transient Growth Curves Transient 2-min 8-min 317 kW MJ Released t-Squared 2 8 12.7 50.7 Peak 6 7 114.1 133.1 Linear Decay 12 14 114.1 133.1 Total 241 317 These transient curves when used with a 317 kW peak HRR fire provide a bounding amount of energy released compared to the testing results shown in Attachment 1 of this FAQ. The amount of energy is the most important metric beyond the peak heat release rate which is already define.
As these curves bound the energy released in testing, this provides a reasonable representation of the room heat-up.
If appropriate, provide proposed rewording of guidance for inclusion in the next Revision:
Replace the guidance in NUREG/CR-6850 Supplement 1 Section 17 with Table 5 representing the full growth profile.
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FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Attachment 1 The total MJs released for each of the tests contained in NUREG/CR-6850 Supplement 1 Appendices A and B is estimated by discretized the bounding HRR distribution shown in each Figure. This is done by noting the key time points where the HRR changes in an Excel chart.
The kJ for each discretized step is changing by multiplying the seconds for each step by the average HRR for the endpoint of the step (i.e. linear ramp). The kJ for all the steps are summed.
This total is divided by 1000 to convert to total MJs released. The analysis for each curve follows:
MJ Released for NUREG/CR-6850 Supplement 1 Figure A-1 Figure A-2 Time [min] Time [sec] HRR [kW] Energy [kJ]
14 0 0 1 0 12 2.4 144 1 144 2.5 150 7 42 10 14.9 894 7 5208 8 15 900 12 72 6 54 3240 12 28080 4 55 3300 0 0 2 0
Sum Energy [MJ] 33.546 0 500 1000 1500 2000 2500 3000 3500 Page 6 of 9
FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Attachment 1 MJ Released for NUREG/CR-6850 Supplement 1 Figure A-2 Figure A-1 Time [min] Time [sec] HRR [kW] Energy [kJ]
0 0 2 0 2.4 144 2 288 2.5 150 17 102 9.9 594 17 7548 30 10 600 10 60 25 12.4 744 10 1440 12.5 750 25 150 20 21.9 1314 25 14100 15 22 1320 20 120 10 64.1 3846 20 50520 65 3900 0 0 5 0
Sum Energy [MJ] 74.328 0 1000 2000 3000 4000 5000 Page 7 of 9
FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Attachment 1 MJ Released for NUREG/CR-6850 Supplement 1 Figure A-3 Figure A-3 Time [min] Time [sec] HRR [kW] Energy [kJ]
0 0 4 0 1.9 114 4 456 2 120 35 210 12.4 744 35 21840 12.5 750 52 312 21.9 1314 52 29328 22 1320 38 228 27.4 1644 38 12312 27.5 1650 114 684 37.9 2274 114 71136 38 2280 50 300 47.4 2844 50 28200 47.5 2850 88 528 54.9 3294 88 39072 55 3300 38 228 70 4200 38 34200 Sum Energy [MJ] 239.034 Page 8 of 9
FAQ Number 18-0015 FAQ Revision 0 (Draft v6)
FAQ Title Transient Fire Growth Curve Attachment 1 MJ Released for NUREG/CR-6850 Supplement 1 Figure B-3 Figure A-7 Time [min] Time [sec] HRR [kW] Energy [kJ]
0 0 2 0 1.9 114 2 228 2 120 27 162 6.9 414 27 7938 7 420 18 108 9.9 594 18 3132 10 600 10 60 13.9 834 10 2340 14 840 3 18 20.9 1254 3 1242 21 1260 0 0 Sum Energy [MJ] 15.228 Page 9 of 9