ML19046A390

Presentation Binder

ML19046A390
Person / Time
Issue date:	01/23/2019
From:	Kenneth Hamburger Office of Nuclear Regulatory Research
To:
Kenneth Hamburger 415-2022
Shared Package
ML19046A388	List: ML19046A389 ML19046A390 ML19046A391 ML19046A392 ML19046A393
References
20181317
Download: ML19046A390 (76)

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Generic Issue (GI) Program Status for PRE-GI-018 Related to High Energy Arcing Faults involving Aluminum Kenneth Hamburger January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Safety & Security

• Please keep visitor badges visible while on NRC property

• First floor access okay without escort

• Anywhere else requires NRC escort

• Fire and emergencies

• Follow NRC staff/security direction 2

PRE-GI-018 Update, January 23, 2019

Meeting Logistics

• Meeting transcribed

• Please identify yourself when speaking (every time)

• Please speak into the microphones

• Webinar participation

• Facilitated

• Keep the meeting on schedule and on topic

• Public comments 3

PRE-GI-018 Update, January 23, 2019

High Energy Arcing Faults Involving Aluminum Meeting Objectives Mark Henry Salley, P.E.

Branch Chief Office of Nuclear Regulatory Research January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Objectives

• Communication

• PRE-GI-018 status update

• Confirmatory testing to-date

- Share some early observations from September 2018 medium-voltage tests

• Next series of confirmatory tests

- Planning stages

- Target date late summer/early fall 2019

• Draft NRC/EPRI Working Group charter

• Open discussion

- Thoughts, ideas, and suggestions 2

PRE-GI-018 Update, January 23, 2019

Generic Issue (GI) Program Status for PRE-GI-018 Related to High Energy Arcing Faults involving Aluminum Stan Gardocki GI Program Manager Office of Nuclear Regulatory Research January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

GI Program Three Stages Issue submitted to GI Program Screening Assessment Implementation Issue exits program when issue fails to meet Or closed when screening criteria, for example: licensees actions

• Referred to other regulatory process for action completed and

• Referred for additional long-term research verified 2

PRE-GI-018 Update, January 23, 2019

3 PRE-GI-018 Update, January 23, 2019

PRE-GI-018 Activities To-Date

• March 4, 2016 - NRR performed a safety review and determined no immediate actions required (ML16064A250)

• May 6, 2016 - RES submitted into the GI Program (ML16126A096)

• May 17, 2016 - GI Program Staff initial screening complete, recommended forming review board (GIRP) (ML16132A415)

• July 15, 2017 - GIRP issued screening report that determined the seven screening criteria were met, recommended proceed to assessment stage (ML16349A027)

• August 22, 2018 - GIRP issued assessment plan (ML18172A185) 4 PRE-GI-018 Update, January 23, 2019

PRE-GI-018 Next Steps

• GIRP will issue an Assessment Report to determine whether the issue should continue to next stage, regulatory office implementation (ROI)

• If yes, then a transition team is formed, issue moves out of RES into appropriate regulatory office, NRR

• NRR determines the necessary regulatory actions (example: issue appropriate generic communications)

• Based upon potential regulatory requirements (if applicable), licensees may have to take actions

• Based on potential regulatory actions, NRR will determine if public meeting will be held 5

PRE-GI-018 Update, January 23, 2019

Assessment Plan Timeline Initial screening report issued Assessment report issued GI Submittal GIRP screening NRR immediate report issued safety GIRP members assessment appointed 01/01/2016 06/30/2016 12/28/2016 06/27/2017 12/25/2017 06/24/2018 12/22/2018 06/21/2019 12/19/2019 06/17/2020 Public Phase I Test Workshop Phase II Test PIRT Exercise Small Scale Phase II Test Large Communication Plan Scale for Al HEAF Information Notice 2017-04 EPRI/NRC ZOI Working Group Pilot Plant Selection Pilot Plant Study 6 Risk/Safety Determination PRE-GI-018 Update, January 23, 2019 Complete Assessment

High Energy Arcing Faults (HEAF)

AL Phase II Confirmatory Testing Preliminary Observations Nicholas Melly Office of Nuclear Regulatory Research Division of Risk Analysis January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Purpose

• Provide an overview of the High Energy Arcing Fault (HEAF) confirmatory testing performed for PRE-GI-018

• Discuss preliminary insights and project goals

• Discuss future testing parameters, schedule and milestones 2

PRE-GI-018 Update, January 23, 2019

Phase II Draft Test Plan

• Public Comment Period

- OECD/NEA Phase I members for comment on June 30, 2017

- Federal Register notice (82 FR 36006) published on August 2, 2017

- Public comment period closed September 1, 2017 3

PRE-GI-018 Update, January 23, 2019

Phase II Draft Test Plan

• Official Public Comment Period

- Federal Register notice (82 FR 36006) published on August 2, 2017

- Public comment period closed September 1, 2017

• 5 comments from NEI

• 32 comments from OECD

- 29 Additional comments received from EPRI on January 12, 2018

- 28 Additional comments received from NEI on May 17, 2018

- 4 Additional comments received from industry technical expert on May 17, 2018

• 98 comments received in total

- International and U.S. Industry

• All comments dispositioned and publically released

- ML18233A469 4

PRE-GI-018 Update, January 23, 2019

HEAF Phase II Test Structure - Enclosures Enclosure Testing Copper Bus Bars Aluminum Bus Bars 480 Volt 6900 Volt 480 Volt 6900 Volt 15kA 25kA 25kA 35kA 15kA 25kA 25 kA 35 kA 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s X X 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 *

• Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program

• Uncommitted tests to explore unanticipated results/enhance repetition if necessary 5

PRE-GI-018 Update, January 23, 2019

Measurement Limitations

• Melting point of Inconel approximately 2,400°F (1,325°C)

• No measurement locations beyond 3 ft.

Before After 6

PRE-GI-018 Update, January 23, 2019

Phase II Improvements Tungsten Slug Calorimeter

• 1 in. diameter tungsten slug Structural Insulation Insulation Board

• Durable for high incident heat fluxes in direct arc plume Thermocouple environment q total 25 mm T (oC)

• Calcium Silicate insulating board Metal Cylinder 7

PRE-GI-018 Update, January 23, 2019

Phase One (I) Pressure Electromagnetic Interference (EMI)

• EMI tends to be most severe during large changes in current, voltage, and arc activity, and these are the same periods where large changes are expected in enclosure pressure

• Positive and negative pressure peaks occur at the onset of the arc, and are of similar magnitude

• New techniques have been developed for Phase II of testing 8

PRE-GI-018 Update, January 23, 2019

Pressure Phase Two (II)

• Strain-gauge type sensor

• Quartz type gauge

• Dynisco Pressure Transducer PT150-50

• Fiber Optic Cabling

• Omega PX-329 9

PRE-GI-018 Update, January 23, 2019

Infrared(IR)

Camera Capabilities

• Non-intrusive temperature measurement

- Using video as test data

• Visualization through smoke

• Speed - rapid event

• Dynamic temperature range

- Ambient to >2000 oC

• Compromises

- Resolution - field of view

- Speed

- Temperature Range (Dynamic Range) 10 PRE-GI-018 Update, January 23, 2019

IR Camera Improvements

• Phase I Camera Capabilities

- High Speed Recording

- Limited Temperature Range

- High Resolution

• Phase II Camera Capabilities

- Greater Temperature Range

- Higher Resolution 11 PRE-GI-018 Update, January 23, 2019

Data Collection

• Phase II of testing will use an isolated data acquisition system with an independent power supply

• Redundant systems will be available for possible arc shorting consequences

• 72 channels 12 PRE-GI-018 Update, January 23, 2019

Test Setup 13 PRE-GI-018 Update, January 23, 2019

Phase II Instrumentation Thermal Capacitance Slug (Tungsten) 14 PRE-GI-018 Update, January 23, 2019

Sandia Camera Angles 15 PRE-GI-018 Update, January 23, 2019

Weights and Measures 16 PRE-GI-018 Update, January 23, 2019

Phase II HEAF Testing Medium Voltage Equipment

• Single compartment GE Magne-blast M-36 metal clad switchgear containing aluminum busbar 17 PRE-GI-018 Update, January 23, 2019

Phase II HEAF Testing Pre Test Arrangement 24 18 PRE-GI-018 Update, January 23, 2019

Phase II HEAF Testing Shorting Wire 19 PRE-GI-018 Update, January 23, 2019

Phase II HEAF Testing Post Test Observations 2-19 2-22 2s, 2s, 25kA 35kA 2-21 2-24 4s, 4s, 25kA 35kA 20 PRE-GI-018 Update, January 23, 2019

Phase II HEAF Testing Post Test Observations 2-22 2-19 2-21 2-24 21 PRE-GI-018 Update, January 23, 2019

Tungsten Thermocouple Damage State/ Survivability Before After 22 PRE-GI-018 Update, January 23, 2019

Plate Thermocouple Damage State/ Survivability 23 PRE-GI-018 Update, January 23, 2019

ASTM F1959 Thermocouple Damage State/Survivability Before After 24 PRE-GI-018 Update, January 23, 2019

HEAF Deposition 25 PRE-GI-018 Update, January 23, 2019

Metal Ejecta 26 PRE-GI-018 Update, January 23, 2019

New Measurement for Future Tests Cloud Particulate Conductivity

• IPC Standard IPC-TM-650 https://www.ipc.org/TM/2.6.3.3b.pdf

• NIST Tech Note https://nvlpubs.nist.gov/nistpubs/TechnicalNotes/NIST.

TN.1985.pdf 27 PRE-GI-018 Update, January 23, 2019

HEAF Phase II Next Test Series Enclosure Testing Copper Bus Bars Aluminum Bus Bars 480 Volt 6900 Volt 480 Volt 6900 Volt 15kA 25kA 25kA 35kA 15kA 25kA 25 kA 35 kA 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s X X 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 *

• Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program

• Uncommitted tests to explore unanticipated results/enhance repetition if necessary 28 PRE-GI-018 Update, January 23, 2019

HEAF Phase II Next Test Series Bus Duct Testing 4160 Volt /

25 kA Copper Bus Copper Bus Aluminum Bus Aluminum Bus Steel Enclosure Aluminum Enclosure Steel Enclosure Aluminum Enclosure 5s 5s 2s 4s 2s 4s 2s 4s 2s 4s 2-33 2-34 2-25 2-26 2-27 2-28 2-29 2-30 2-31 2-32 Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program Uncommitted tests to explore unanticipated 29 results/enhance repetition if necessary PRE-GI-018 Update, January 23, 2019

NRC/OECD Phase II Actions

• Public Comment Period Closes................................................ September 2, 2017 (Completed)

• OECD Comment Period...................................... August 31 / September 15, 2017 (Completed)

• OECD HEAF Meeting................................................................. October 12, 2017 (Completed)

• HEAF Workshop ......................................................................... April 18-19, 2018 (Completed)

• OECD HEAF Meeting....................................................................... April 23, 2018 (Completed)

• Comment Resolution ....................................................................... May 11, 2018 (Completed)

• Final Test Plan..........................................................................September 1, 2018 (Completed)

• Signed International Agreement .............................Spring 2019 (Target)

• International Equipment Delivery.........................................................Spring 2019 (Target)

• Initial Test Series............................................................... September 10-14, 2018 (Completed)

• Second Series of Tests (To correspond w/ International OECD Meeting)........................ Spring- May 2019 (Target)

• Remaining Tests......................................................................... 2019/ 2020/ 2021 30 PRE-GI-018 Update, January 23, 2019

High Energy Arcing Faults (HEAF)

AL Future Planning and Equipment Selection Gabriel Taylor & Kenn Miller Office of Nuclear Regulatory Research January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Purpose

• Communicate NRC planned equipment types for testing

• Solicit feedback from stakeholders 2

PRE-GI-018 Update, January 23, 2019

HEAF Phase II - PERFORMED September tests Enclosure Testing Copper Bus Bars Aluminum Bus Bars 480 Volt 6900 Volt 480 Volt 6900 Volt 15kA 25kA 25kA 35kA 15kA 25kA 25 kA 35 kA 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s X X 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 *

• Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program

• Uncommitted tests to explore unanticipated results/enhance repetition if necessary 3

PRE-GI-018 Update, January 23, 2019

HEAF Phase II - PLANNED Low Voltage Enclosure Testing Copper Bus Bars Aluminum Bus Bars 480 Volt 6900 Volt 480 Volt 6900 Volt 15kA 25kA 25kA 35kA 15kA 25kA 25 kA 35 kA 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s 2s 4s 8s 2s 4s 8s 2s 4s 4s 2s 4s 4s X X 2-1 2-2 2-3 2-4 2-5 2-6 2-7 2-8 2-9 2-10 2-11 2-12 2-13 2-14 2-15 2-16 2-17 2-18 2-19 2-20 2-21 2-22 2-23 2-24 *

• Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program

• Uncommitted tests to explore unanticipated results/enhance repetition if necessary 4

PRE-GI-018 Update, January 23, 2019

Low Voltage Enclosures Aluminum Bus

• Westinghouse DS switchgear

• GE AK Series

• 1600A or 2000A frame size

• 42kA to 65kA interrupting capacity 5

PRE-GI-018 Update, January 23, 2019

HEAF Phase II - PLANNED MV Bus Ducts Bus Duct Testing 4160 Volt /

25 kA Copper Bus Copper Bus Aluminum Bus Aluminum Bus Steel Enclosure Aluminum Enclosure Steel Enclosure Aluminum Enclosure 2s 4s 2s 4s 2s 4s 2s 4s 5s 5s 2-25 2-26 2-27 2-28 2-29 2-30 2-31 2-32 *

• Legend OECD/NEA HEAF Phase 2 Tests US NRC Specific Spplemental Testing driven by Generic Issue Aluminum HEAF Program Uncommitted tests to explore unanticipated results/enhance repetition if necessary 6

PRE-GI-018 Update, January 23, 2019

MV Bus Ducts General Characteristics

• Non-segregated phase bus duct

• Medium Voltage: 4.16kV

• 1200 - 2000A rated

• 31.5 - 63kA withstand

• IEEE C37.23

• Stabilize arc location

- Gap at arc location?

- Epoxy insulation?

7 PRE-GI-018 Update, January 23, 2019

MV Bus Ducts Aluminum Components

• Enclosure

- 11 gauge aluminum housing

• Conductor

- ASTM B236

• Other design considerations?

8 PRE-GI-018 Update, January 23, 2019

Decrement Curve

• Working with EPRI and KEMA to implement decrement curve

- 6.9kV metal-clad switchgear

- Requires new contract

- Laboratory analysis & verification 9

PRE-GI-018 Update, January 23, 2019

Summary

• Continued focus on aluminum

• Equipment donations welcome

• Decrement curve

- Implementation slow due to contracting process

- Industry support could expedite this 10 PRE-GI-018 Update, January 23, 2019

High Energy Arcing Faults NRC-EPRI Working Group Charter Mark Henry Salley, P.E.

Branch Chief Office of Nuclear Regulatory Research January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Mission Statement

• To improve understanding of risk from electrical arcing fault hazards in nuclear power plants (NPPs).

2 PRE-GI-018 Update, January 23, 2019

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

- What can go wrong?

- How likely is it?

- What are the consequences?

3 PRE-GI-018 Update, January 23, 2019

Working Group Members Ken Fleischer (Fleischer Consultants) JS Hyslop (NRC)

Dane Lovelace (Jensen Hughes) Nicholas Melly (NRC)

Shannon Lovvern (TVA) Kenn Miller (NRC)

Tom Short (EPRI) Gabriel Taylor (NRC)

Marko Randelovic/ Chris LaFleur (SNL)

Ashley Lindeman(EPRI)

Project Managers Project Sponsors Kelli Voelsing (EPRI) Tina Taylor (EPRI)

Mark Henry Salley (NRC) Michael Cheok (NRC) 4 PRE-GI-018 Update, January 23, 2019

Deliverables

• Improved risk models

- Frequency and binning

- Zone of influence

• Risk to NPPs

- Pilot plants

• Updated guidance

• Communication with stakeholders 5

PRE-GI-018 Update, January 23, 2019

NRC Priorities

• Aluminum HEAF Generic Issue

- Zone of influence

- Physical/thermal damage

- Effects of products of combustion cloud

• OECD/NEA Testing

- Additional test data (primarily copper)

• NRC/EPRI Working Group

- Develop realistic models

- International OECD/NEA peer review

• Improve NUREG/CR-6850 Appendix M

- Improve FAQ-07-0035 Bus Duct Guidance for HEAFs 6

PRE-GI-018 Update, January 23, 2019

The following 5 slides were presented by:

Victoria K Anderson Technical Advisor Risk and Technical Services Nuclear Energy Institute

HEAF Aluminum Pre-GI

• Decisions regarding a Generic Issue are designed to be risk-informed Specifically: CDFHEAF Al = CDF(HEAF Al) - CDF(HEAF Baseline)

HEAF Aluminum Pre-GI

• Past Generic Issues were dispositioned according to Most Fire PRA CDF(HEAF CDF versus CDF Baseline) results found in changes green region

• Likely the case for this pre-GI

• Decisions based on conservative assumptions could result in inappropriate decisions

• A single fire PRA assessment without realistic assessment of the baseline risk, and event-specific initiating event frequencies and consequences, will lead to inaccurate assessments

HEAF Aluminum Pre GI Potentially erroneous conclusion without Decisions based on considering full spectrum of plant configurations conservative assumptions and possible events could result in industry-wide assessment that Need to consider whether these points are driven by does not apply to vast conservatism in HEAF Al majority of plants, i.e.: testing or CCDP estimation

- Assumption Al is always present

- HEAF Al is always more energetic

- HEAF Al always increases CCDP

- HEAF AI based on the worst case fire scenario applies to all plants

HEAF Aluminum Pre-GI

• Comparison with previous GI on new seismic hazard information

• Seismic PRAs not available to the extent fire PRAs currently are

• Even with limited risk-informed approach, high variability in decision making impact

• Resolution of the issue requires better realism in assessment AND in resolution of pre-GI

• Assuming a one-size fits all would waste resources

• Crediting realistic HEAF Al impacts, protections against feeding HEAF, existence of Al is critical

• Imperative to accurately assess baseline

• Most plants may not require action

Industry Priorities for HEAF Evaluations

• Understanding and evaluating data from previous tests and OE

• Achieve consensus on technical approach for frequency and zone of influence work

• Complete additional testing to resolve any identified gaps

• Complete realistic evaluation of plants using testing data and OE Timeline needs to support execution of these steps in order

High Energy Arcing Fault (HEAF)

Technical Considerations for Understanding Risk Kelli Voelsing RSM Program Manager NRC Public Meeting January 23, 2019 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Assuming the worst case Invasive surgery to Location/size remove the Type of Cancer malignancy Stage Poisonous Genetic Markers chemotherapy with damaging Targeted therapies side-effects on the market Risks and sickness Other treatments from radiation supporting quality therapy of life Not all cancers, and not all arcing faults, are the same 2 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Current Bin 16 Treatment in NUREG/CR-6850 (1011989)

P1-Al?

P1-Al?

P1 P1 C-178A C-178A Current Bin 16 treatment applies one probability and one ZOI to all events 3 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Examples of Differentiating Factors in Arcing Fault Events Energy - Medium Voltage or Low Voltage Location - potentially affecting safety significant equipment SSC - Switchgear, Motor Control Center, Isophase/Non-seg bus duct Source of fault - Breaker-side or load-side Electrical configuration - e.g.,

Unit-connected* and protection scheme Material - Presence and location of aluminum Operational issues - Cleanliness, maintenance, human performance

• Plant electrical system design found in fossil and nuclear plants that do not employ a generator breaker that can isolate the energy source (main generator) from the fault during generator coast-down as the voltage collapses 4 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Elements of HEAF Working Group Charter To improve understanding of risk from electrical arcing fault hazards in nuclear power plants (NPPs)

1. Improved risk models - supported by all available information (e.g., testing, data, OE, expert engineering judgement)

Realistic representation of frequency of events represented in Bin 16 Appropriate modeling of various zones of influence (ZOI) for events included in Bin 16

2. Risk to NPPs - Evaluation of potential increase in risk of actual plants considering impact of frequency and ZOI work as well as-built, as-operated plant

3. Updated guidance - Enhanced fidelity and realism for modeling arcing fault events in Fire PRA

4. Communication with stakeholders 5 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Early Insights Related to Frequency Work Limited data - Total population in Bin 16 from 1964-2017 is 28 events

- Includes a wide variety of equipment

- Data includes arcing flash/blast events (at least 10) and HEAF events

- Data includes events with and without post-event fire and damage

- With only 28 events, creating multiple sub-bins of 0-1 events makes it difficult to break down further and retain statistically useful information Within Bin 16 there are useful insights about the which events occur under which conditions

- Medium Voltage (MV) SSCs - 84% of the Bin 16 events that were damaging occurred in MV equipment

- Low Voltage (LV) SSCs - Only 2 damaging events occurred in LV equipment. In both cases, there was insufficient energy to trip the protection features. This prolonged the event, but there is no indication of a HEAF, and the damage term was related to post-event fire, not the HEAF

- Of the events with external damage, 7 out of 11 were in buses (isophase/non-seg buses) that are less likely to impact safety -

significant equipment based on plant configuration 6 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Early Insights Related to ZOI Work Limited data - Fragility of SSCs versus contact with the by-product

- Current ZOI used for Bin 16 is based on a SONGS event (Appendix M).

- Small scale nor large scale test results on HEAF by-product characterization are not available Significant useful insights about the which events occur under which conditions

- Al2O3 is an excellent insulator material with very low conductivity

- In most conditions Al oxidizes to Al2O3 very rapidly

- Presence of Al2O3 white dust may not cause failure

- The arc travels away from the source.

Cable trays are not likely to be located directly in front/back of switchgear cabinets.

- Bus ducts likely have a downward directed conical ZOI when not constrained by barriers (e.g., floor)

- Arc flash and arc blast events have negligent ZOIs 7 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Early Insights on Plant Risk Average plant risk is an elusive concept

- A review of all units in the US shows that ~70% of plants are NOT susceptible to a long-duration generator fed fault on the safety related bus (i.e. do not have the unit connected design).

- Even when long-duration generator fed faults can occur the following factors must be considered Voltage will decay rapidly as the generator spins down Presence or absence of Al, proximity to fault location Equipment in the ZOI

- It is not rare to have aluminum in bus ducts (isophase and non-seg) due to weight/cost Risk is depending on SSCs within the ZOI This is generally a low contributor to risk in most plant fire PRAs -

outside/non-safety related equipment is impacted 8 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Test Considerations Breaker initiated versus switchgear initiated faults

- OE shows that the frequency is for these is different.

- Breaker-side initiated faults may not be able to persist long enough to impact Al with high energy

- Consequences may be different Data for evaluating damage

- Target selection to assure results are representative of plant equipment

- Actual location and data collection to assess impact on operation

- OE does not suggest large-scale deposition of by-products and damage outside the cubicle

- Clarity on what conductivity/material is being measured is required Representative conditions that can lead to longer durations for the 4-second and 8-second faults

- MV - Generator wind-down voltage curve for decay of voltage during spin down

- LV - Not enough energy to trip the protection scheme 9 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

Refined Bin 16 Treatment in Supplemental NUREG/CR-6850 (1011989) Guidance C-178A C-178A P3 P1 P4 P2 All arcing fault events are not the same -

Risk should consider probability of various event types and associated ZOIs 10 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

TogetherShaping the Future of Electricity 11 www.epri.com © 2019 Electric Power Research Institute, Inc. All rights reserved.

High Energy Arcing Faults Involving Aluminum Closing Remarks Michael Franovich Division Director Office of Nuclear Reactor Regulation January 23, 2019 1

PRE-GI-018 Update, January 23, 2019

Closing Remarks

• Thank you

• Transparency, public involvement, and clear communication

• Realistic assessment of the hazard

• Risk-Informed Resolution 2

PRE-GI-018 Update, January 23, 2019