ML11090A087
| ML11090A087 | |
| Person / Time | |
|---|---|
| Site: | Three Mile Island  |
| Issue date: | 04/05/2011 |
| From: | Shanley L Exelon Nuclear |
| To: | Office of Nuclear Reactor Regulation |
| Bowen, Jeremy | |
| Shared Package | |
| ML11090A079 | List: |
| References | |
| NUMARC 93-01, Rev 4 | |
| Download: ML11090A087 (18) | |
Text
Public Meeting Concerning Rev 4 to
NUMARC 93-01 Rockville, MDMarch292011 March 29 , 2011TMI Fire (a)(4) Tabletop Pilot Method and Results Leo Shanley Methodology*Use Fire PRA to identify important components based on table in 93-01 Rev. 4*Fire PRA CDF top event quantified DetermineequipmenttoconsiderinscopeofTMI Fire (a)(4) Pilot -Overview 2 Determine equipment to consider in scope of Section 11 revisions Determine important scenarios when equipment is unavailable Obtain insights and help identify Risk Management Actions (RMA)*Focus of Fire PRA use will be on development and application of insights Why not use CDF values directly (i.e., similar to internal events)?*Fire PRAs are in various states of refinement at the 10 Exelon sites Fire PRA level of detail not yet comparable to that of Internal EPRATMI Fire (a)(4) Pilot -Overview 3 E vents PRA*General conservatisms in methodology, some of which are being addressed by industry
initiatives*Specific conservatisms revealed when removing equipment from service TMI Fire PRA Status*Fire PRA databases updated in 2007, underlying PRA model updated in 2009
- InternallyreviewedbutnotpeerreviewedTMI Fire (a)(4) Pilot -Overview 4 Internally reviewed , but not peer reviewed*Includes SSEL components
- Scenarios and cutsetshave not yet been reviewed against specific maintenance
configurations Scope: "-identify equipment within the existing (a)(4) scope that is found to have appreciable impact on core damage mitigation for fire
initiators."*Lookin g for com p onents that
, when removed TMI Fire (a)(4) Pilot -Methodology 5gp,from service, result in one or more scenarios where no success paths are available (i.e.,
CCDP = "1.0")
Per the table in NUMARC 93-01 (Draft) Rev. 4, these components require risk management actions if removed from service for 3 -30 days*Should be able to screen scenarios that already have CCDP = "1.0" in the base case Table from NUMARC 93-01 (Draft) Rev. 4
[Section 11.3.7.3] TMI Fire (a)(4) Pilot -MethodologyNumber of Core Damage Avoidance Success Paths Available1 or More Success Paths AvailableNo Success Paths Available 6Duration of UnavailabilityDuration of Unavailability<3d3-30d>30d<3d3-30d>30dNormal Controls RMANormal ControlsRMAAvoidConfig.
Risk Management Actions (RMA): "-develop a process for implementing risk management actions related to fire risk impacts of equipment identified-"
- ReviewFireCDF cutsetsforcaseswithTMI Fire (a)(4) Pilot -Methodology 7 Review Fire CDF cutsets for cases with identified equipment out-of-service Identify the scenarios in which there are no success/mitigation paths Determine what is driving scenario The RMA must address the initiator or plant configuration that results in core damage Scope*Started with at-power internal events (a)(4) scope of equipment Approximately 160 components that affect the PRA are included in the TMI (a)(4) model.TMI Fire (a)(4) Pilot -Results 8*Quantified Fire PRA CDF with (a)(4) components unavailable one at a time.
Identified scenarios of interest by comparing CCDP for each scenario with base case CCDP for each scenarioUsed PARAGON software to help automate process of quantification and CCDP calculations Scope*Identified about 50 components that resulted in one or more scenarios that met
the criteria MostlyelectricalbusesECCSpumpsServiceTMI Fire (a)(4) Pilot -Results 9 Mostly electrical buses , ECCS pumps , Service Water and EDGs Some asymmetry in trains (EFW, 120V Vital AC)*Nothing unexpected -most potentially fire risk significant components are important for internal events TMI Fire (a)(4) Pilot -Scope ResultsElectrical Buses, MCCs, Distribution Panels (19)*4kV ESF Buses (2), 480V ESF Buses and MCCs (10), DC Distribution (6) Panels, 120V Vital AC (1) ECCS (8)10 ()*Make-up Pumps (3), Decay Heat Removal Pumps (2), BWST Suction Valves (2), BWSTService and Component Cooling Water (11)*Service Water Pumps (3), Decay Heat Service Water Pumps and HX (2), Nuclear Services CCW HX (2),
Decay Heat CCW Pumps (2), Intermediate CCW
Pumps (2)
TMI Fire (a)(4) Pilot -Scope ResultsEmergency Feedwater (4)*Motor-driven EFW Pump (1), Turbine-driven EFW Pump (1), Turbine-driven EFW Turbine Inlet Valve (1)
CST (1)11 Diesel Generators (3)*EDG (2), SBO DG (1) Miscellaneous (6)*250/125VDC Batteries (2), ESF Instrument Air Compressors (2), 120V Vital AC Inverter (1), Atmospheric Dump Valve (1)
Risk Management Actions (RMA)*Reviewed CCDP =1 cutsetsto characterize the scenarios and develop RMAs With one train unavailable, a fire affecting the other train could result in core damageTMI Fire (a)(4) Pilot -Results 12*Affected Fire Areas and Scenarios Minimum of one scenario in one fire area (e.g., EDG-1A)Some equipment important to fire (buses, ECCS pumps) have many scenarios (>15) in multiple fire
areas (>5)
Risk Management Actions (RMA)*Nearly all identified components require RMAs in current (a)(4) program (e.g., protect opposite train, minimize time in configuration)
Internal events CDF or LERF > 2x BaselineTMI Fire (a)(4) Pilot -Results 13Reduced Defense-in-depth*About 60% of the identified components have Tech Spec AOTs <
72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.*Nearly half of the identified components are not normally removed from service while at-
powerBuses, MCCs, Batteries, BWST, CST Transients/Cable Fires*Sensitivity to or control of hot work in fire zones or areas within fire zones*Minimize transient combustibles
- Fire watchesHihEAiFlt(HEAF)TMI Fire (a)(4) Pilot -Potential RMAs 14 Hi g h E nergy A rc i ng F au lt s (HEAF)*Minimize electrical switchingIncipient Detection*Ensure it's available for scenarios where it's important Suppression*Ensure automatic suppression systems are available where important and/or brief Fire Brigade TMI Fire (a)(4) Pilot -DHR Pump RMAEquip IDEquip DescriptionFire Area IDFire Area DescriptionDetection/ SuppressionCause of FireNo. of ScenariosPotential RMAsDH-P-1ADHR Pump 1AAB-FZ-5281' General AreaNoneCable fires in various trays with potential to spread to other trays2 (B01, B02)Avoid or minimize hotworkin area. 1 (B06)Avoid or minimize hotworkin area.CB-FA-2b322' 1S (Train B) ESF 480V Incipient DetectionFire in Remote Shutdown Transfer 1 (E01)a) Ensure detection s ystem is available 15)SwitchgearSwitch Panel with failure of detection or fire brigade response yb) Brief operators and fire brigade on significance of fire in this room.Cable fire with potential to spread to other trays1 (F04)Avoid or minimize hotworkin area.CB-FA-2c322' Tech Support Center Incipient DetectionFire in cabinet RS-SCC-B2 with failure of detection or fire brigade1 (J02)a) Ensure detection system is availableb) Brief operators and fire brigade on significance of fire in this room.
TMI Fire (a)(4) Pilot -EDG RMAsEquip IDEquip DescriptionFire Area IDFire Area DescriptionDetection/ SuppressionCause of FireNo. of ScenariosPotential RMAsEG-Y-1AEDG 1ACB-FA-3b338' 1E (Train B) Switchgear Room Incipient DetectionHEAF in 1E switchgear1 (B6)Avoid or minimize breaker manipulations on 1E switchgear 16EG-Y-1BEDG 1BCB-FA-3a338' 1D (Train A) Switchgear Room Incipient DetectionHEAF in 1D switchgear5 (B3, B4, B5, B6, B7)Avoid or minimize breaker manipulations on 1D switchgearEG-Y-4SBO DGCB-FA-1306' Rad Con Office and Lab AreaNoCable fire in tray with propagation to other trays 2 (B01, B03)Avoid or minimize hotworkin area Fire PRA can be used to identify fire risk significant equipment*No 'surprises' in equipment identified -most equipment already risk significant for internal events*Identified equipment list is manageable -nearly half fititlldfiTMI Fire (a)(4) Pilot -Conclusions 17 o f equ i pmen t i s no t norma ll y remove d f rom serv i ce while at-powerFire PRA can be used to establish RMAs*Review needed at the cutset level to evaluate the scenario and develop RMAs*Some components have many scenarios that may require RMAs Lessons Learned*Fire PRAs provide conservative results when equipment removed from service -some
screening needs to be done during review*Need to account for fla g s and s p lit fractions
-TMI Fire (a)(4) Pilot -Conclusions 18 gpbest to set them to 1.0 to ensure nothing is missed*More than 1 component removed from service Are there new scenarios beyond the union of the individual equipment scenarios?
Some cases were reviewed as part of tabletop Generally not found