ML17340B101

12/13/2017 Meeting Presentation, Moving Towards Mmre Realistic Cabinet Damage

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
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ML17340B096	List: ML17340B097 ML17340B098 ML17340B100 ML17340B101 ML17340B102 ML17340B103 ML17340B104 ML17340B105 ML17340B106
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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):

FireIDSpecific ComponentChallenging DeterminationEvent DateFire CharacterizationFire Characterization TypeExtent Source DamagePower Effect 69Control Cabinet4 U(NC-PC)8/29/1994Fire 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)UnknownScram 98Control Cabinet2-PC10/8/1998During 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 EDGSmoldering combustion - internal to componentConfined to the object of originEntered an LCO 187Control Cabinet2-PC8/16/1999thick grey smoke observedFlaming combustion - internal to componentConfined to the object of origin (broad/extensive damage)None 303Control Cabinet2-PC3/1/2000Electrical short resulting in burning insulation and paint in Plant Heating Boiler Control Cabinet.Flaming combustion - external to componentConfined to the object of origin (broad/extensive damage)None 20272Relay Rack4 U(NC-PC)9/10/1990UnknownOther (specify)Confined to the object of originUnknown 30276Other2-PC7/24/2006Lighting battery box smoking, flames observed coming out near transformerFlaming combustion - internal to componentConfined to the object of originNone 30281Relay Rack1-CH6/5/2008Failed 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 componentConfined to the object of origin (localized/single subcomponent)None 30338Control Cabinet2-PC3/30/2006Discovered 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 componentConfined to the object of origin (localized/single subcomponent)None 30478Control Cabinet2-PC9/9/2005Source of fire a bunch of relays, wiring sustained significant damage to insulationFlaming combustion - internal to componentConfined to the object of origin (broad/extensive damage)None 30513Control Cabinet2-PC5/27/2008Voltage transformer overheated and ignited combustible material located inside transformer housingFlaming combustion - internal to componentConfined to the object of originNone 30522Control Cabinet2-PC9/12/2000fire 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 componentConfined to the object of originNone 50473Wall Mounted2-PC6/26/2000small flames from relay with smoke, water intrusion, sparking and smoke before power removedFlaming combustion - internal to componentConfined to the object of originNone 50784Relay Rack2-PC11/20/2005Testing relay, started to smoke - fuses pulled and shot with extinguisherFlaming combustion - external to componentConfined to the object of origin (localized/single subcomponent)None 50811Control Cabinet2-PC1/9/2001relay burning, found extinguisher and put outFlaming combustion - internal to componentConfined to the object of origin (localized/single subcomponent)None83-1Wall Mounted2-PC4/4/1996Smoke 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 cablesFlaming combustion - internal to componentConfined to the object of origin (localized/single subcomponent)None83-2Wall Mounted2-PC4/4/1996DC EQUP room fire - fire limited to transformer enclosure and involved only internals. Flaming combustion - internal to componentConfined 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 LossImproved Cabinet ModelingCaseDescriptionImpactFrequencyFrequency X1Fire within CabinetBoth FC A and B Lost7.00E-051.75E-05 X2Fire within CabinetFC A lost; FC B functionalN/A2.63E-05 X3Fire within CabinetFC B lost; FC A functionalN/A2.63E-05 X4Fire Damages cabinet and TargetFCs A and B Lost and 1st Target2.80E-052.80E-05 X5Fire Damages whole roomWhole Room Lost2.00E-062.00E-06Sum Check1.00E-041.00E-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