Assessing
Fire Protection Findings for the
Significance Determination Process
Michelle Kichline
Reliability and Risk Analyst
Office of Nuclear Reactor Regulation
Division of Risk Assessment
Outline
• Introduction
• Description of the Performance Deficiency
• Characterization of the Performance
Deficiency
– Phase 1 and 2 analysis
• Analysis of the Performance Deficiency
– Phase 3 analysis
• Results
2
Introduction
Reactor Oversight Process (ROP)
Inspection Program
Performance
Indicators
3
Introduction
Inspection
Findings
Significance
Determination
Process
(SDP)
(IMC 0609)
Phase 2
Phase 1
Phase 3
4
Description of the
Performance Deficiency
Unit 1
Service
Water
(SW)
Pump 1A
Unit 2
SW Pump
1B
Unit 1
Emergency
Switchgear
Unit 1
SW Pump
2A
Room
(ESGR)
Unit 2
SW Pump
2B
Unit 1
Control
Room
5
Characterization of the
Performance Deficiency
Minor
Performance
Deficiencies
More than
Minor
Evaluate
Finding using
SDP
6
Phase 1
Flow
Chart
IMC 0609,
Appendix F,
Figure F.1
7
Analysis of the
Performance Deficiency
ΔCDF = DF x F x SF x AF x PNS x CCDP
Where:
•
•
•
•
•
•
•
ΔCDF = Change in core damage frequency
DF = Duration factor
F = Fire frequency for the fire ignition source
SF = Severity factor for the scenario
AF = Ignition source specific frequency adjustment factor
PNS = Probability of non-suppression for the scenario
CCDP = Conditional core damage probability for the scenario
8
Analysis of the
Performance Deficiency
9
Hot Gas Layer
Input Parameters
Compartment Width
11.6 m. [38 ft.]
Compartment Length
15.2 m. [50 ft.]
Compartment Height
6.1 m. [20 ft.]
Vent (door) Width
0.9 m. [3 ft.]
Vent (door) Height
2.1 m. [7 ft.]
Top of Vent from Floor
2.1 m. [7 ft.]
Interior Lining Thickness
3.7 m. [12 ft.]
Ambient Air Temperature
25°C [77°F]
Interior Lining Material
Concrete
Heat Release Rate of the Fire
200 kW
Input parameters for NUREG-1805, Spreadsheet 2.1, “Predicting Hot Gas Layer
Temperature and Smoke Layer Height in a Room Fire with Natural Ventilation.”
10
Smoke Detector Response
Input Parameters
Heat Release Rate of the Fire
70 kW
Radial Distance to Detector
0.9 m.
[3 ft.]
Height of Ceiling above Top of Fuel
3.6 m.
[11.75 ft.]
Ambient Air Temperature
25°C
[77°F]
Input parameters for NUREG-1805, Spreadsheet 10, “Estimating Smoke
Detector Response Time.”
11
Ball and Column
Zone of Influence
IMC 0609, Appendix F, Task 2.3.4, “Fire Ignition Source Screening.”
12
Cable Tray
Fire Progression
NUREG/CR-6850, Figure R-5, “Model for Fire Propagation in a Cable Tray Stack.”
13
Flame Height
Calculation
Hf = .235(HRR)2/5 – 1.02 D
Where:
• Hf = flame height in meters
• HRR = Heat release rate of the fire in kW
• D = Diameter of the fire in meters
14
Plume Centerline
Temperature Calculation
Heat Release Rate of the Fire
200 kW
Elevation Above the Fire Source
0.5 m. [1.67 ft.]
Area of Combustible Fuel
0.6 m2. [6 sq. ft.]
Ambient Air Temperature
25°C [77°F]
Input parameters for NUREG-1805, Spreadsheet 9, “Estimating Centerline
Temperature of a Buoyant Fire Plume.”
15
Thermoset Cable
Failure Time
Table A7.1 - Failure Time-Temperature Relationship for Thermoset Cables
Exposure Temperature
°C
330 ≤ T < 335
335 ≤ T < 340
340 ≤ T < 345
345 ≤ T < 350
350 ≤ T < 360
360 ≤ T < 370
370 ≤ T < 380
380 ≤ T < 390
390 ≤ T < 400
400 ≤ T < 410
410 ≤ T < 430
430 ≤ T < 450
450 ≤ T < 470
470 ≤ T < 490
T ≥ 490
°F
625 ≤ T < 634
634 ≤ T < 642
642 ≤ T < 651
651 ≤ T < 660
660 ≤ T < 680
680 ≤ T < 700
700 ≤ T < 716
716 ≤ T < 735
735 ≤ T < 752
752 ≤ T < 770
770 ≤ T < 805
805 ≤ T < 840
840 ≤ T < 880
880 ≤ T < 915
T ≥ 915
Time to Failure
(minutes)
IMC 0609, Appendix F, Attachment 7, Table A7.1
28
24
20
16
13
10
9
8
7
6
5
4
3
2
1
16
Probability of
Non-Suppression
Table A8.2 - Probability of Non-suppression for Fixed Fire
Suppression Systems Based on the Absolute Difference
Between Damage Time and Suppression Time
Time Delta: (tDamage - tSuppress )
PNSFixed
Negative Time up to 1 Minute
1.0
> 1 Minute to 2 Minutes
.95
> 2 Minutes to 4 Minutes
.80
> 4 Minutes to 6 Minutes
.5
> 6 Minutes to 8 Minutes
.25
> 8 Minutes to 10 Minutes
.1
> 10 Minutes
IMC 0609, Appendix F, Attachment 8, Table A8.2
0.0
17
Results
ΔCDF = DF x F x SF x AF x PNS x CCDP
Where:
• ΔCDF = Change in core damage frequency
• DF = Duration factor (= 1.0)
• F = Fire frequency for the fire ignition source (= 6E-5)
• SF = Severity factor for the scenario (= 0.1)
• AF = Ignition source specific frequency adjustment factor (= 1.0)
• PNS = Probability of non-suppression for the scenario (= .5)
• CCDP = Conditional core damage probability for the scenario
(= 1.8E-3)
18
Conclusion
• Must evaluate all possible fire growth scenarios
to determine total change in risk.
• Each scenario is evaluated using both its
expected and high confidence heat release
rates.
• Total change in CDF for this performance
deficiency was less than 1E-6 per year.
• Performance deficiency was corrected using
plant modifications.
19
Summary
NUREG1805
IMC
0609,
Appendix
F
PlantSpecific
Fire
Information
NUREG/
CR-6850
Detailed
Fire
Modeling
Risk Significance of the
Finding
20