ML17340B101

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 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.).

1 Moving towards more Realistic Cabinet Damage

Identification of Relevant Guidance NUREG/CR-6850 Section 8.5.1.2 (pg. 8-10) 2 Moving towards more Realistic Cabinet Damage

Proposed Approach to Enhance Realism 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.

3 Moving towards more Realistic Cabinet Damage

Data for Proposed Approach to Enhance Realism Data (3-of-16 is wide spread damage):

Specific Challenging FireID Component 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). Other (specify) Unknown Scram 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.

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 Confined to the object of origin Entered an LCO to component 187 Control Cabinet 2-PC 8/16/1999 thick grey smoke observed Flaming combustion - internal to Confined to the object of origin None component (broad/extensive damage) 303 Control Cabinet 2-PC 3/1/2000 Electrical short resulting in burning insulation and paint in Plant Flaming combustion - external to Confined to the object of origin None Heating Boiler Control Cabinet. component (broad/extensive damage) 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 Flaming combustion - internal to Confined to the object of origin None transformer component 30281 Relay Rack 1-CH 6/5/2008 Failed relay in controm room cabinet due to overheating. Smoldering combustion - external Confined to the object of origin None Evidence of smoke, opened panel and saw relay with failed to component (localized/single subcomponent) insulation. No flaming observed.

30338 Control Cabinet 2-PC 3/30/2006 Discovered fire in blower. Extinguished using CO2. Contacted Flaming combustion - internal to Confined to the object of origin None electricians to investigate problem. Electricians disconnected the component (localized/single subcomponent) 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.

30478 Control Cabinet 2-PC 9/9/2005 Source of fire a bunch of relays, wiring sustained significant Flaming combustion - internal to Confined to the object of origin None damage to insulation component (broad/extensive damage) 30513 Control Cabinet 2-PC 5/27/2008 Voltage transformer overheated and ignited combustible material Flaming combustion - internal to Confined to the object of origin None located inside transformer housing component 30522 Control Cabinet 2-PC 9/12/2000 fire kept to electrical cabinet. Damage to internals with noticable Flaming combustion - internal to Confined to the object of origin None charring and smoke damage, external box had some heat and component smoke damage.

50473 Wall Mounted 2-PC 6/26/2000 small flames from relay with smoke, water intrusion, sparking and Flaming combustion - internal to Confined to the object of origin None smoke before power removed component 50784 Relay Rack 2-PC 11/20/2005 Testing relay, started to smoke - fuses pulled and shot with Flaming combustion - external to Confined to the object of origin None extinguisher component (localized/single subcomponent) 50811 Control Cabinet 2-PC 1/9/2001 relay burning, found extinguisher and put out Flaming combustion - internal to Confined to the object of origin None component (localized/single subcomponent) 83-1 Wall Mounted 2-PC 4/4/1996 Smoke was discovered in the back boards area of the control room Flaming combustion - internal to Confined to the object of origin None by a security offer who was performing an hourly fire watch. component (localized/single subcomponent)

Smoke was emitting from the emergency lightning UPS. Damage limited to cabinet involved and adjoining cables 83-2 Wall Mounted 2-PC 4/4/1996 DC EQUP room fire - fire limited to transformer enclosure and Flaming combustion - internal to Confined to the object of origin None involved only internals. component (localized/single subcomponent) 4 Moving towards more Realistic Cabinet Damage

Example 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:

Conservative full Cabinet Improved Cabinet Only Loss Modeling benefit is in Case Description Impact Frequency Frequency the Fire X1 Fire within Cabinet Both FC A and B Lost 7.00E-05 1.75E-05 within a X2 Fire within Cabinet FC A lost; FC B functional N/A 2.63E-05 cabinet X3 Fire within Cabinet FC B lost; FC A functional N/A 2.63E-05 region 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 5 Moving towards more Realistic Cabinet Damage

Industry Benefit Maximum site benefit is 20% CDF reduction. The average industry benefit is 2%.

6 Moving towards more Realistic Cabinet Damage

Questions 7 Moving towards more Realistic Cabinet Damage