ML17340B101
| ML17340B101 | |
| Person / Time | |
|---|---|
| Site: | Nuclear Energy Institute |
| Issue date: | 12/13/2017 |
| From: | Cavedo R Exelon Generation Co, Nuclear Energy Institute |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML17340B096 | List: |
| References | |
| Download: ML17340B101 (8) | |
Text
Moving Towards more Realistic Cabinet Damage Rob Cavedo
Potential Realism Improvement Moving towards more Realistic Cabinet Damage 1
All trains and functions that can be affected by a fire are assumed to occur at the cabinet ignition frequency.
For most cabinets, this is a mildly conservative assumption (e.g. breaker goes open/breaker goes closed).
For cabinets that control multiple trains from different power supplies, this can be overly conservative.
Industry events of cabinets with multiple trains do not show the loss of all trains (e.g. single alarm card damaged others functional, single HS malfunction, etc.).
Identification of Relevant Guidance Moving towards more Realistic Cabinet Damage 2
NUREG/CR-6850 Section 8.5.1.2 (pg. 8-10)
Proposed Approach to Enhance Realism Moving towards more Realistic Cabinet Damage 3
Use a 25% chance all functions in a cabinet are lost and a 75% chance a single function is lost. This is based on a review of the sixteen control cabinet scenarios in the Fire Events Database (FEDB) only three are considered to represent broad damage to the cabinet.
A train is defined as any equipment in the cabinet powered from the same ultimate external power supply to the cabinet.
If all equipment in the cabinet is powered from the same external source, then this method cannot be applied.
This would only apply to scenarios with NO EXTERNAL damage. If the fire is large enough to damage external equipment, then larger internal losses are expected.
Data for Proposed Approach to Enhance Realism Moving towards more Realistic Cabinet Damage 4
Data (3-of-16 is wide spread damage):
FireID Specific Component Challenging Determination Event Date Fire Characterization Fire Characterization Type Extent Source Damage Power Effect 69 Control Cabinet 4 U(NC-PC) 8/29/1994 Fire damaged cables in control cabinet (located in the Switchyard).
Fire caused by breakdown of insulation in a control cable. The insulation breakdown was located where the insulation came in contact with a protruding tap of a wire wound power resistor.
Insulation breakdown due to aging (25 years) and water intrusion.
Other (specify)
Unknown Scram 98 Control Cabinet 2-PC 10/8/1998 During a 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> post maintenance run of the EDG Smoldering combustion - internal to component Confined to the object of origin Entered an LCO 187 Control Cabinet 2-PC 8/16/1999 thick grey smoke observed Flaming combustion - internal to component Confined to the object of origin (broad/extensive damage)
None 303 Control Cabinet 2-PC 3/1/2000 Electrical short resulting in burning insulation and paint in Plant Heating Boiler Control Cabinet.
Flaming combustion - external to component Confined to the object of origin (broad/extensive damage)
None 20272 Relay Rack 4 U(NC-PC) 9/10/1990 Unknown Other (specify)
Confined to the object of origin Unknown 30276 Other 2-PC 7/24/2006 Lighting battery box smoking, flames observed coming out near transformer Flaming combustion - internal to component Confined to the object of origin None 30281 Relay Rack 1-CH 6/5/2008 Failed relay in controm room cabinet due to overheating.
Evidence of smoke, opened panel and saw relay with failed insulation. No flaming observed.
Smoldering combustion - external to component Confined to the object of origin (localized/single subcomponent)
None 30338 Control Cabinet 2-PC 3/30/2006 Discovered fire in blower. Extinguished using CO2. Contacted electricians to investigate problem. Electricians disconnected the blower from its power source and removed the blower from the cabinet. Blower found to be full of dust and dirt. Smoke detecter in cabinet did not alarm while the area inside the panel was hazy with smoke.
Flaming combustion - internal to component Confined to the object of origin (localized/single subcomponent)
None 30478 Control Cabinet 2-PC 9/9/2005 Source of fire a bunch of relays, wiring sustained significant damage to insulation Flaming combustion - internal to component Confined to the object of origin (broad/extensive damage)
None 30513 Control Cabinet 2-PC 5/27/2008 Voltage transformer overheated and ignited combustible material located inside transformer housing Flaming combustion - internal to component Confined to the object of origin None 30522 Control Cabinet 2-PC 9/12/2000 fire kept to electrical cabinet. Damage to internals with noticable charring and smoke damage, external box had some heat and smoke damage.
Flaming combustion - internal to component Confined to the object of origin None 50473 Wall Mounted 2-PC 6/26/2000 small flames from relay with smoke, water intrusion, sparking and smoke before power removed Flaming combustion - internal to component Confined to the object of origin None 50784 Relay Rack 2-PC 11/20/2005 Testing relay, started to smoke - fuses pulled and shot with extinguisher Flaming combustion - external to component Confined to the object of origin (localized/single subcomponent)
None 50811 Control Cabinet 2-PC 1/9/2001 relay burning, found extinguisher and put out Flaming combustion - internal to component Confined to the object of origin (localized/single subcomponent)
None 83-1 Wall Mounted 2-PC 4/4/1996 Smoke was discovered in the back boards area of the control room by a security offer who was performing an hourly fire watch.
Smoke was emitting from the emergency lightning UPS. Damage limited to cabinet involved and adjoining cables Flaming combustion - internal to component Confined to the object of origin (localized/single subcomponent)
None 83-2 Wall Mounted 2-PC 4/4/1996 DC EQUP room fire - fire limited to transformer enclosure and involved only internals.
Flaming combustion - internal to component Confined to the object of origin (localized/single subcomponent)
None
Example Moving towards more Realistic Cabinet Damage 5
Flow controllers for Pump A and B are in Cabinet X.
Given a per panel ignition frequency of 1E-4, the conservative and more realistic results are:
Only benefit is in the Fire within a cabinet region Conservative full Cabinet Loss Improved Cabinet Modeling Case Description Impact Frequency Frequency X1 Fire within Cabinet Both FC A and B Lost 7.00E-05 1.75E-05 X2 Fire within Cabinet FC A lost; FC B functional N/A 2.63E-05 X3 Fire within Cabinet FC B lost; FC A functional N/A 2.63E-05 X4 Fire Damages cabinet and Target FCs A and B Lost and 1st Target 2.80E-05 2.80E-05 X5 Fire Damages whole room Whole Room Lost 2.00E-06 2.00E-06 Sum Check 1.00E-04 1.00E-04
Industry Benefit Moving towards more Realistic Cabinet Damage 6
Maximum site benefit is 20% CDF reduction. The average industry benefit is 2%.
Questions Moving towards more Realistic Cabinet Damage 7