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Mark Schairer Engineering Planning and Management, Inc.
Mark Schairer Engineering Planning and Management, Inc.


Description of Potential Realism Improvement: NSP Data Conservatism There is a disconnect between the average durations of fire scenarios in Fire PRAs vs. fire event experience The fire durations include time lags or delays associated with reporting time to control the fire versus time to extinguish the fire and time associated with de
Description of Potential Realism Improvement: NSP Data Conservatism There is a disconnect between the average durations of fire scenarios in Fire PRAs vs. fire event experience The fire durations include time lags or delays associated with reporting time to control the fire versus time to extinguish the fire and time associated with de-energizing equipment, offsite fire brigade response, and water application In Fire PRAs, the source scenarios reach peak HRR in 12 minutes.
-energizing equipment, offsite fire brigade response, and water application In Fire PRAs, the source scenarios reach peak HRR in 12 minutes. Using FLASH
Using FLASH-CAT, multiple trays are involved well before 20 minutes. Peak ZOI and HGL occur before 20 minutes.
-CAT, multiple trays are involved well before 20 minutes. Peak ZOI and HGL occur before 20 minutes.
Typically, on-site fire brigade arrival is expected to be 10-15 minutes, and upon arrival, fire is under control within 5-10 minutes.
Typically, on
-site fire brigade arrival is expected to be 10-15 minutes, and upon arrival, fire is under control within 5
-10 minutes.
From the NSP data, more than 25% of fire events have durations longer than 20 minutes 2
From the NSP data, more than 25% of fire events have durations longer than 20 minutes 2
Identification of Relevant Guidance 3 NUREG-2169, Section 5.2. NSP Estimation Update, provides the following probability distributions for rates of fires suppressed per unit time,  (data is based on fire events from 1981
 
-2009)
Identification of Relevant Guidance NUREG-2169, Section 5.2. NSP Estimation Update, provides the following probability distributions for rates of fires suppressed per unit time,  (data is based on fire events from 1981-2009) 3
 
Proposed Approach to Enhance Realism: Initial Assessment Review fire event information obtained from NRC Event Reports, Licensee Event Reports, or through Plant contacts.
Proposed Approach to Enhance Realism: Initial Assessment Review fire event information obtained from NRC Event Reports, Licensee Event Reports, or through Plant contacts.
Re-examine when the fires were under control, rather than totally extinguished. At the control point, the fire is no longer a threat to fire spread, hot gas layer formation, additional target damage.
Re-examine when the fires were under control, rather than totally extinguished. At the control point, the fire is no longer a threat to fire spread, hot gas layer formation, additional target damage.
Consider limiting data to only the more recent fire events to be consistent with fire ignition frequency data 4
Consider limiting data to only the more recent fire events to be consistent with fire ignition frequency data 4
Proposed Approach to Enhance Realism: Initial Assessment Initial scoping of high
-duration electrical cabinet fires from NRC Event Reports:
5 EPRI Fire ID Event Date Power Mode Fire Severity Bin Designation NSP Category Suppression Time (min) 1097 11/15/1986 Low-power operation Undetermined 26 Electrical 95 418 4/28/1984 Low-power operation Challenging 10 Electrical 60 642 11/4/1987 Power operation Challenging 15.1 Electrical 50 98 10/8/1998 RF PC 15 Electrical 46 30362 12/16/2001 RF PC 21 Electrical 45 50829 9/11/2004 PO PC 23 Electrical 45 175 11/22/2009 CD CH 15 Electrical 45 121 4/26/2003 PO U 21 Electrical 37 505 1/8/1986 Low-power operation Undetermined 21 Electrical 36 20302 7/25/1993 PO U 15 Electrical 35 238 1/24/1981 Power operation Challenging 21 Electrical 30 557 1/31/1987 Low-power operation Challenging 22 Electrical 30 656 12/17/1987 Power operation Challenging 22 Electrical 30 97 6/10/1998 PO PC 22 Electrical 29 10626 12/11/2002 PO PC 21 Electrical 27 235 12/30/1992 PO PC 26 Electrical 25 Preliminary estimates based on expert judgement For events over 20 minutes in duration, reduce the duration by half, but not less than 20 minutes; Events under 20 minutes were unaltered i.e., 50 min event was reduced to 25 min, while 30 min event to 20 min


The average duration was reduced by ~20%
Proposed Approach to Enhance Realism: Initial Assessment Initial scoping of high-duration electrical cabinet fires from NRC Event Reports:
NSP      Suppression Time EPRI Fire ID Event Date    Power Mode        Fire Severity Bin Designation Category        (min) 1097      11/15/1986 Low-power operation Undetermined        26        Electrical        95 418        4/28/1984 Low-power operation  Challenging        10        Electrical        60 642        11/4/1987  Power operation    Challenging      15.1      Electrical        50 98        10/8/1998        RF                PC            15        Electrical        46 30362      12/16/2001        RF                PC            21        Electrical        45 50829      9/11/2004        PO                PC            23        Electrical        45 175      11/22/2009        CD                CH            15        Electrical        45 121        4/26/2003        PO                U            21        Electrical        37 505        1/8/1986  Low-power operation Undetermined        21        Electrical        36 20302      7/25/1993        PO                U            15        Electrical        35 238        1/24/1981  Power operation    Challenging        21        Electrical        30 557        1/31/1987 Low-power operation  Challenging        22        Electrical        30 656      12/17/1987  Power operation    Challenging        22        Electrical        30 97      6/10/1998          PO                PC            22        Electrical        29 10626      12/11/2002        PO                PC            21        Electrical        27 235      12/30/1992        PO                PC            26        Electrical        25 5
 
Summary of Anticipated Realism Improvements Preliminary estimates based on expert judgement For events over 20 minutes in duration, reduce the duration by half, but not less than 20 minutes; Events under 20 minutes were unaltered i.e., 50 min event was reduced to 25 min, while 30 min event to 20 min Average Total Number  Sum of            NSP at time =
NSP Curve                              Duration Events    Durations              20
[min]
NUREG-2169            177      1815    10.3      0.142 Estimate of Improvement      177      1492      8.4      0.093 The average duration was reduced by ~20%
NSP at 20 minutes reduced by 35%
NSP at 20 minutes reduced by 35%
6 NSP Curve Total Number Events Sum of Durations Average Duration [min] NSP at time =
6}}
20 NUREG-2169 177 1815 10.3 0.142 Estimate of Improvement 177 1492 8.4 0.093 Summary of Anticipated Realism Improvements}}

Revision as of 09:54, 22 October 2019

12/13/2017 Meeting Presentation, Conservatism in Non-Suppression Probability (NSP) Data
ML17340B098
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Site: Nuclear Energy Institute
Issue date: 12/13/2017
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Conservatism in Non-Suppression Probability (NSP) Data FPRA FAQ Public Meeting December 13, 2017 Presented by:

Mark Schairer Engineering Planning and Management, Inc.

Description of Potential Realism Improvement: NSP Data Conservatism There is a disconnect between the average durations of fire scenarios in Fire PRAs vs. fire event experience The fire durations include time lags or delays associated with reporting time to control the fire versus time to extinguish the fire and time associated with de-energizing equipment, offsite fire brigade response, and water application In Fire PRAs, the source scenarios reach peak HRR in 12 minutes.

Using FLASH-CAT, multiple trays are involved well before 20 minutes. Peak ZOI and HGL occur before 20 minutes.

Typically, on-site fire brigade arrival is expected to be 10-15 minutes, and upon arrival, fire is under control within 5-10 minutes.

From the NSP data, more than 25% of fire events have durations longer than 20 minutes 2

Identification of Relevant Guidance NUREG-2169, Section 5.2. NSP Estimation Update, provides the following probability distributions for rates of fires suppressed per unit time, (data is based on fire events from 1981-2009) 3

Proposed Approach to Enhance Realism: Initial Assessment Review fire event information obtained from NRC Event Reports, Licensee Event Reports, or through Plant contacts.

Re-examine when the fires were under control, rather than totally extinguished. At the control point, the fire is no longer a threat to fire spread, hot gas layer formation, additional target damage.

Consider limiting data to only the more recent fire events to be consistent with fire ignition frequency data 4

Proposed Approach to Enhance Realism: Initial Assessment Initial scoping of high-duration electrical cabinet fires from NRC Event Reports:

NSP Suppression Time EPRI Fire ID Event Date Power Mode Fire Severity Bin Designation Category (min) 1097 11/15/1986 Low-power operation Undetermined 26 Electrical 95 418 4/28/1984 Low-power operation Challenging 10 Electrical 60 642 11/4/1987 Power operation Challenging 15.1 Electrical 50 98 10/8/1998 RF PC 15 Electrical 46 30362 12/16/2001 RF PC 21 Electrical 45 50829 9/11/2004 PO PC 23 Electrical 45 175 11/22/2009 CD CH 15 Electrical 45 121 4/26/2003 PO U 21 Electrical 37 505 1/8/1986 Low-power operation Undetermined 21 Electrical 36 20302 7/25/1993 PO U 15 Electrical 35 238 1/24/1981 Power operation Challenging 21 Electrical 30 557 1/31/1987 Low-power operation Challenging 22 Electrical 30 656 12/17/1987 Power operation Challenging 22 Electrical 30 97 6/10/1998 PO PC 22 Electrical 29 10626 12/11/2002 PO PC 21 Electrical 27 235 12/30/1992 PO PC 26 Electrical 25 5

Summary of Anticipated Realism Improvements Preliminary estimates based on expert judgement For events over 20 minutes in duration, reduce the duration by half, but not less than 20 minutes; Events under 20 minutes were unaltered i.e., 50 min event was reduced to 25 min, while 30 min event to 20 min Average Total Number Sum of NSP at time =

NSP Curve Duration Events Durations 20

[min]

NUREG-2169 177 1815 10.3 0.142 Estimate of Improvement 177 1492 8.4 0.093 The average duration was reduced by ~20%

NSP at 20 minutes reduced by 35%

6

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