ML19183A312
| ML19183A312 | |
| Person / Time | |
|---|---|
| Issue date: | 07/02/2019 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| K. Hamburger 415-2022 | |
| Shared Package | |
| ML19183A307 | List: |
| References | |
| Download: ML19183A312 (25) | |
Text
Public Meeting - July 24, 2019 High Energy Arcing Faults (HEAF)
Working Group Status Update Nicholas Melly Nuclear Regulatory Commission Office of Nuclear Regulatory Research Marko Randelovic Electrical Power Research Institute Senior Technical Leader
Public Meeting - July 24, 2019
- Provide overview of NRC/EPRI working group (WG) activities and progress
- WG Mission
- PRA modeling approach / update
- Lessons learned from operational experience review
- Testing approach
- Project Plan Purpose 2
Public Meeting - July 24, 2019 NRC / EPRI Working Group (WG)
Charter Mission Statement
- To improve understanding of risk from electrical arcing fault hazards in nuclear power plants (NPPs).
Goals
- Better understand key factors contributing to:
- Occurrence
- Severity
- Advance HEAF fire PRA modeling
- Based on experimental data, operating experience, and engineering judgement
- Ignition frequency
- Zone of influence (ZOI)
- Analyze plant impact and risk implications Weekly Meetings
Public Meeting - July 24, 2019 Ken Fleischer (Fleischer Consultants)
Dane Lovelace (Jensen Hughes)
Shannon Lovvern (TVA)
Tom Short (EPRI)
Marko Randelovic (EPRI)
Ashley Lindeman (EPRI)
NRC / EPRI WG Team Project Managers Kelli Voelsing (EPRI)
Mark Henry Salley (NRC)
Project Sponsors Tina Taylor (EPRI)
Michael Cheok (NRC)
Dr. Chris LaFleur (SNL)
Nicholas Melly (NRC)
Kenn Miller (NRC)
Gabriel Taylor (NRC)
Public Meeting - July 24, 2019
- EPRI/NRC HEAF Methodology Report
- Extensive OpE review
- Fault Duration
- Fault Location
- HEAF Fire Ignition Frequency
- 1E vs. Non-1E investigation
- HEAF redefinition to fit OpE and modeling uses
- Risk Model Development
- Event Trees
- HEAF Non-Suppression Curve
- HEAF modeling guidance
- Data Analysis NRC/EPRI WG Activities
Public Meeting - July 24, 2019 Research and test durations are based on operating experience Millisecond fault occurrences are not part of the HEAF frequency bins OpE Review identified additional generator fed faults than previously known NRC/EPRI WG Activities Operating History (OpE review)
Plant Event Event classification Event Duration Palo Verde (M Voltage) 7/6/1988 Arc Blast 0.75 sec (actual duration)
DC Cook (M Voltage) 7/13/1990 HEAF Likely 0.5 sec Waterford (M Voltage) 6/10/1995 HEAF 4-8 sec (estimated:
generator fed)
SONGS (M Voltage) 2/3/2001 HEAF 4-8 sec (estimated:
generator fed)
Prairie Island (M Voltage) 8/3/2001 HEAF 4-8 sec (estimated:
generator fed)
Robinson (M Voltage) 3/28/2010 HEAF 1st Event: 20 sec (actual HEAF duration)
Robinson (M Voltage) 3/28/2010 HEAF 2nd Event: 3 Min high impedance fault followed by unknown duration HEAF event Palo Verde(M Voltage) 7/3/2013 HEAF Estimated < 2 seconds (however, photo evidence that protection may have operated much faster)
Brunswick (M Voltage) 2/7/2016 Arc Blast 0.15 sec (estimated duration)
Yankee Rowe (L Voltage) 8/2/1984 HEAF Unknown Fort Calhoun (L Voltage) 6/7/2011 HEAF 42 sec (actual duration)
River Bend (L Voltage) 2/12/2011 HEAF 12 Sec
Public Meeting - July 24, 2019 Fault Characteristics Fault Duration 0
2 4
6 8
10 12 Unknown 0.5 1
2 4
12 20 50 Number of Events Duration of Fault (seconds)
Actual Duration Estimated Duration Investigation of OpE event duration to ensure testing and modeling efforts representative
Public Meeting - July 24, 2019
- Low voltage cabinets were procured using input and recommendations from the WG
- Testing parameters will be adjusted accordingly to mimic faults from OpE
- Current WG activity to investigate typical protective device setpoints Evaluation of the US OE Low Voltage Plant Event Event classification Event Duration Germany (L Voltage) 5/30/1986 HEAF 8.5 Sec Yankee Rowe (L Voltage) 8/2/1984 HEAF Unknown Fort Calhoun (L Voltage) 6/7/2011 HEAF 42 sec (actual duration)
River Bend (L Voltage) 2/12/2011 HEAF 12 Sec Ref. Westinghouse I.B. 33-790-1E
Public Meeting - July 24, 2019 NRC/EPRI WG Activities Testing-Supply vs. Load Fall 2018 testing followed IEEE guidance with respect to arc wire location and size Working group review of OE on medium voltage switchgear revealed majority of the medium voltage switchgear events occurred in the supply switchgear configuration and involved main bus work
- Configuration and equipment type has been identified as parameters of interest
- Working group is currently discussing options to most accurately reflect realism in a testing environment
Public Meeting - July 24, 2019
- Event Frequency classification
- Need for clear definitions
- Subdivide Bin 16 (NUREG/CR-6850)
- Arc Fault Class 1 (Arc Flash)
- Arc Fault Class 2 (Arc Blast)
- Arc Fault Class 3 (HEAF)
- NRC working with NFPA/IEEE & EPRI Working Group
- Continued discussion to finalize definitions for arc fault events
- Updated frequencies for HEAF events to be developed by the NRC/EPRI HEAF WG to coincide with the ZOI methodology and event tree modeling approach NRC/EPRI WG Activities Frequency Review
Public Meeting - July 24, 2019 Arc Fault Classifications 11
Public Meeting - July 24, 2019
- Approach being developed by the WG to incorporate plant design with ZOI and HEAF susceptibility
- More accurate reflection of realism
- Major improvement over a one size fits all model
- Currently in the developmental stage with WG NRC/EPRI WG Activities PRA Risk Model Development
Public Meeting - July 24, 2019 NRC/EPRI WG Activities Risk Model Development Generic Frequency x
Ignition Source Weighting Factor Location SWGR Breaker Available Source Design Generator Circuit Breaker Duration ZOI End Sequence (Zone 2)
End Sequence (Zone 1 & 5)
< 2 ZOI 1 A2 N/A (Zone 2)
GCB Works
< 4 ZOI 2 B2 A1 Supply GCB Fails 4 - 8 ZOI 3 C2 B1 4 - 8 ZOI 3 D2 C1 (Zone 1)
< 4 ZOI 2 E2 A5 g*Wis
< 2 ZOI 1 F2 N/A (Zone 2)
GCB Works
< 4 ZOI 2 G2 N/A Load GCB Fails 4 - 8 ZOI 3 H2 N/A 4 - 8 ZOI 3 I2 N/A (Zone 1)
< 4 ZOI 2 J2 N/A SWGR Breaker Unavailable/Fails Unit Auxiliary Transformer Site Auxiliary Transformer Unit Auxiliary Transformer Site Auxiliary Transformer Generator Circuit Breaker No Generator Circuit Breaker No Generator Circuit Breaker Generator Circuit Breaker SWGR Breaker Available AND Functions SWGR Breaker Available AND Functions SWGR Breaker Unavailable/Fails
Public Meeting - July 24, 2019 Temperature and Heat Flux
- Both parameters will be modeled at multiple distances away from the arc location
- Will aid in a dynamic ZOI creation
- Link to SNL Fragility criteria testing (to be discussed in the afternoon)
Pressure (improved measurement techniques developed)
- Potential to measure impact on room pressure currently being explored Damage Zone Furthest extent of damage
- Thermal (i.e. ensuing fire damage / smoke damage)
- Physical ( i.e. thrown cabinet door, shrapnel)
Conductivity
- SNL Measurements
- Other Options HEAF Phase II Testing Measurement
Public Meeting - July 24, 2019 Mass of Material Vaporized Measurements pre-and post-testing to validate computer models and theory equations of vaporized material Potential to develop approximate energy release models from classical energy conversion models Cable Sample Material Cable samples placed at varying distances away from enclosure Byproduct Testing Samples Carbon Tape & Aerogel used in 2018 Carbon Tape & Silicon/Quartz in 2019 Conductivity measurements for aluminum deposited on surfaces Spectroscopy Heat Release Rate (HRR) measurement is impratical based on lessons learned in phase I testing HEAF Phase II Testing Measurement (continued)
Public Meeting - July 24, 2019
- SNL has experience with this type of measurement
- Surface conductivity
- Passive measurements
- Interdigitated resistivity measurement structures
- Parallel conductive traces
- Evaluate voltage holdoff/surface flashover properties
- Concentric ring surface resistance measurement (ASTM D257)
- This instrumentation will address the potential for failure of electronic equipment exposed to the arc ejecta or smoke generated by the HEAF event HEAF Phase II Testing Surface Conductivity Measurements
Public Meeting - July 24, 2019
- Conductivity sensor
- Active measurement
- Mesh design for EMI rejection
- Air conductance measured as voltage in circuit HEAF Phase II Testing Air Conductivity Measurements
Public Meeting - July 24, 2019 Purpose of the Mock Switchgear Test Unit (MSTU) is to verify if liberal amounts of aluminum combustion cloud byproduct/debris is sufficient to cause collateral damage (flashover) in nearby/adjacent medium voltage.
To the extent practical, the MSTU is to represent typical switchgear with respect to voltage, bus bar spacing and standoff insulators to ground MSTUs are portable, re-usable and do not require excessive power Provides prototypical configuration to evaluate flashover Mock Switchgear Test Unit Evaluate flashover (arc-over)
Public Meeting - July 24, 2019
- Design of the MSTU is based on a bounding approach to which type electrical distribution system (EDS) is most vulnerable to a flashover or tracking phenomenon out of:
- Wye system (solidly grounded)
- Wye system (resistance grounded)
- Wye (ungrounded neutral)
- Delta (ungrounded)
- Uninsulated bus bars Mock Switchgear Test Unit Evaluate flashover (arc-over)
Public Meeting - July 24, 2019 HEAF Phase II Testing Conductivity-Benefits and Limitations Type Benefit Limitation Surface Conductivity Known Measurement Technique Can measures hold off
/ break down in addition to surface resistance Passive design Does not measure air conductivity Requires failure criteria of components which may require additional testing or engineering judgment Air Conductivity Active instrumentation Limited number to deploy Mock Switchgear Close simulation of plant equipment Bounding result (Exclusionary)
Public Meeting - July 24, 2019 Aug/Sept 19 Phase II Tests Electrical Enclosures Legend OECD/NEA HEAF Phase 2 Tests U.S. NRC specific supplemental testing driven by generic issue aluminum HEAF program Uncommitted tests to explore unanticipated results/enhance repetition if necessary Enclosure Testing Aluminum Bus Bars Copper Bus Bars 6900 Volt 480 Volt 6900 Volt 25kA 15kA 35kA 25kA 4s 2-2 35 kA 480 Volt 25 kA 15kA 25kA 4s 2-5 4s 2-8 4s 2-9 4s 2-11 4s 2-12 4s 2-14 4s 2-17 4s 2-20 2s 2-22 4s 2-23 2s 2-1 2s 2-4 2s 2-7 2s 2-10 4s 2-24 X
X 8s 2-6 8s 2-3 2s 2-13 8s 2-15 2s 2-16 8s 2-18 4s 2-21 2s 2-19
Public Meeting - July 24, 2019 Legend OECD/NEA HEAF Phase 2 Tests U.S. NRC specific supplemental testing driven by generic issue aluminum HEAF program Uncommitted tests to explore unanticipated results/enhance repetition if necessary Aluminum Bus Steel Enclosure Copper Bus Aluminum Enclosure Aluminum Bus Aluminum Enclosure Copper Bus Steel Enclosure 4s 2-26 2s 2-25 2s 2-27 4s 2-28 4s 2-30 4s 2-32 2s 2-31 Bus Duct Testing 4160 Volt /
25 kA 2s 2-29 5s 2-33 5s 2-34 Phase II Tests Bus Ducts Aug/Sept 19
Public Meeting - July 24, 2019
- New information used as identified to re-evaluate objectives of test plan
- Changes being proposed to focus on
- Configuration
- Arc location
- Equipment design
- Decrement
- Arc Current
- Duration Phase II Test plan re-evaluation
Public Meeting - July 24, 2019 Phase II Tests Electrical Enclosures-Spring 2020 Enclosure Testing MV Supply Side Config.
Aluminum Horizontal Draw-out Breakers 2x-4 4s Vertical Lift Breakers 2x-3 4 s 2x-2 Decrement Curve*
Copper Vertical Lift Breakers 2x-1 Decrement Curve*
Focus of decrement curve testing is to be representative of NPP OpE and generator characteristics to determine appropriate testing conditions Decrement tests 2x-1 2x-2 Confirmatory tests 2x-3 2x-4 Working Group recommendations for both equipment procurement, test design conditions and applicability to plant realism has been incorporated into the upcoming Summer 2019 and Spring 2020 and test series and will continue to be actively incorporated into future testing
Public Meeting - July 24, 2019
- Project plan is being developed to capture all components of the HEAF research program and how they fit together
- History
- Scoping/Literature Studies
- Phase I Testing
- Small Scale Testing
- Phase II Testing
- Modeling and Analytical Work
- NRC webpage will be hosted for easy reference and tracking
- This will be in addition to the Generic Issues Dashboard site Project Plan