ML19162A418

01_03 Task 2 Comp Select

ML19162A418
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Issue date:	06/13/2019
From:	Nick Melly NRC/RES/DRA
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T. Rivera
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NUREG/CR-6850 FIRE PRA METHODOLOGY Module 1 Internal Event, At-Power Probabilistic Risk Assessment Model for SNPP Task 2: Fire PRA Component Selection Nicholas Melly - Nuclear Regulatory Commission Fire PRA Workshop June 24, 2019 - June 28, 2019 Rockville, MD U.S. NRC HQ

Component Selection Purpose (per 6850/1011989)

Purpose: Describe the procedure for selecting plant components to be modeled in a Fire PRA Fire PRA Component List

- Key source of information for developing Fire PRA Model (Task 5)

Used to identify cables that must be located (Task 3)

Process is iterative to ensure appropriate agreement among fire PRA Component List, Fire PRA Model, and cable identification Fire PRA Workshop 2019, Rockville, MD Slide 2 Module 1: Internal Event, At-Power PRA Model for SNPP

Corresponding PRA Standard Element Primary match is to element ES - Equipment Selection

- ES Objective (as stated in the PRA standard):

Select plant equipment that will be included/credited in the fire PRA plant response model.

Fire PRA Workshop 2019, Rockville, MD Slide 3 Module 1: Internal Event, At-Power PRA Model for SNPP

HLRs (per the PRA Standard)

HLR-ES-A: The Fire PRA shall identify equipment whose failure caused by an initiating fire, including spurious operation, will contribute to or otherwise cause an initiating event (6 SRs)

HLR-ES-B: The Fire PRA shall identify equipment whose failure, including spurious operation, would adversely affect the operability/functionality of that portion of the plant design to be credited in the Fire PRA (5 SRs)

HLR-ES-C: The Fire PRA shall identify instrumentation whose failure, including spurious operation, would impact the reliability of operator actions associated with that portion of the plant design to be credited in the Fire PRA (2 SRs)

HLR-ES-D: The Fire PRA shall document the fire PRA equipment selection, including that information about the equipment necessary to support the other fire PRA tasks (e.g., equipment identification, equipment type, normal, desired, failed states of equipment), in a manner that facilitates fire PRA applications, upgrades, and peer review (1 SR)

Fire PRA Workshop 2019, Rockville, MD Slide 4 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Scope (per 6850/1011989)

Fire PRA Component List should include the following major categories of equipment:

Equipment whose fire-induced failure (including spurious actuation) causes an initiating event Equipment needed to perform mitigating safety functions and to support operator actions Equipment whose fire-induced failure or spurious actuation may adversely impact credited mitigating safety functions Equipment whose fire-induced failure or spurious actuation may cause inappropriate or unsafe operator actions Fire PRA Workshop 2019, Rockville, MD Slide 5 Module 1: Internal Event, At-Power PRA Model for SNPP

Component Selection Approach (per 6850/1011989)

Step 1: Identify Internal Events PRA sequences to include in fire PRA Model (necessary for identifying important equipment)

Step 2: Review Internal Events PRA model against the Fire Safe Shutdown (SSD) Analysis and reconcile differences in the two analyses (including circuit analysis approaches)

Step 3: Identify fire-induced initiating events based on equipment affected Step 4: Identify equipment subject to fire-induced spurious operation that may challenge the safe shutdown capability Step 5: Identify additional mitigating, instrumentation, and diagnostic equipment important to human response Step 6: Include potentially high consequence related equipment Step 7: Assemble the Fire PRA Component List Fire PRA Workshop 2019, Rockville, MD Slide 6 Module 1: Internal Event, At-Power PRA Model for SNPP

Component Selection General Observations Two major sources of existing information are used to generate the Fire PRA Component List:

Internal Events PRA model Fire Safe Shutdown Analysis (Appendix R assessment)

Just tweaking your Internal Events PRA is probably NOT sufficient - Requires additional effort

- Consideration of fire-induced spurious operation of equipment

- Potential for undesirable operator actions due to spurious alarms/indications

- Additional operator actions for responding to fire (e.g., opening breakers to prevent spurious operation)

Just crediting Appendix R components may NOT be conservative

- True that all other components in Internal Events PRA will be assumed to fail, but:

May be missing components with adverse risk implications (e.g., event initiators or complicated SSD response)

May miss effects of non-modeled components on credited (modeled) systems/components and on operator performance Still need to consider non-credited components as sources of fires Fire PRA Workshop 2019, Rockville, MD Slide 7 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Overview of Scope In Appendix R In Internal Events PRA CDF/LERF vs.

New* analysis resources tradeoff

• - multiple spurious

- new sequences In Fire PRA perhaps not all of Appendix R New*

not all internal event sequences Fire PRA Workshop 2019, Rockville, MD Slide 8 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Assumptions The following assumptions underlie this procedure:

A good quality Internal Events PRA and Appendix R Safe Shutdown (SSD) analysis are available Analysts have considerable collective knowledge and understanding of plant systems, operator performance, the Internal Events PRA, and Appendix R SSD analysis Steps 4 thru 6 are applied to determine an appropriate number of spurious actuations to consider Configurations, timing, length of sustained spurious actuation, cable material, etc., among reasons to limit what will be modeled Note that HS duration is a current FAQ topic Fire PRA Workshop 2019, Rockville, MD Slide 9 Module 1: Internal Event, At-Power PRA Model for SNPP

From: Lessons Learned and Insights In-process FAQs FAQ 08-0051 Issue:

The guidance does not provide a method for estimating the duration of a hot short once formed This could be a significant factor for certain types of plant equipment that will return to a fail safe position if the hot short is removed or if MSO concurrence could trigger adverse impacts

- General approach to resolution:

Analyze the cable fire test data to determine if an adequate basis exists to establish hot short duration distributions

- Status:

Approved, but limited to AC hot shorts only Will be revisited with lessons learned from DESIREE-FIRE test results for DC hot shorts (NUREG/CR-7100)

Fire PRA Workshop 2019, Rockville, MD Slide 10 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Inputs/Outputs Task inputs and outputs:

Inputs from other tasks: Equipment considerations for operator actions from Task 12 (Post-Fire HRA)

Inputs from the MSO Expert Panel Reviews Could use inputs from other tasks to show equipment does not have to be modeled (e.g., Task 9 - Detailed Circuit Analysis or Task 11 -

Fire Modeling to show an equipment item cannot spuriously fail or be affected by possible fires)

Outputs to Task 3 (Cable Selection) and Task 5 (Risk Model)

Choices made in this task set the overall analysis scope Fire PRA Workshop 2019, Rockville, MD Slide 11 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details Step 1: Identify sequences to include and exclude from Fire PRA Some sequences can generally be excluded Sequences requiring passive/mechanical failures that can not be initiated by fires (e.g., pipe-break LOCAs, SGTR, vessel rupture)

Sequences that can be caused by a fire but are low frequency (e.g., ATWS in a PWR)

It may be decided to not model certain systems (i.e., assume failed for Fire PRA) thereby excluding some sequences (e.g., main feedwater as a mitigating system not important)

Possible additional sequences (recommend use of expert panel to address plant specific considerations)

Sequences associated with spurious operation (e.g., vessel/SG overfills, PORV opening, letdown or other pressure/level control anomalies)

MCR abandonment scenarios and other sequences arising from Fire Emergency Procedures (FEPs) and/or use of local manual actions Corresponding PRA Standard SRs: PRM-B5,B6 Fire PRA Workshop 2019, Rockville, MD Slide 12 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 2: Review the internal events PRA model against the fire safe shutdown analysis Identify and reconcile:

Differences in functions, success criteria, and sequences (e.g.,

Appendix R - no feed/bleed; PRA - feed/bleed)

Front-line and support system differences (e.g., Appendix R -

Need HVAC; PRA - Do not need HVAC)

System and equipment differences due to end-state and mission considerations (e.g., Appendix R - cold shutdown; PRA - hot shutdown)

Other miscellaneous equipment differences Include review of manual actions (e.g., actions needed for safe shutdown) in conjunction with Task 12 (HRA)

Corresponding PRA Standard SRs: ES-A3(a), ES-B1,B3 Fire PRA Workshop 2019, Rockville, MD Slide 13 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 3: Identify fire-induced initiating events based on equipment affected Consider equipment whose failure (including spurious actuation) will cause automatic plant trip Consider equipment whose failure (including spurious actuation) will likely result in manual plant trip, per procedures Consider equipment whose failure (including spurious actuation) will invoke Technical Specification Limiting Condition of Operation (LCO) necessitating a forced shutdown while fire may still be present (prior EPRI guidance recommended consideration of <8 hr LCO)

Compartments with none of the above need not have initiator though can conservatively assume simple plant trip Corresponding PRA Standard SRs: ES-A1,A3 & PRM-B3,B4,B5,B6 Fire PRA Workshop 2019, Rockville, MD Slide 14 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Since not all equipment/cable locations in the plant (e.g., all Balance of Plant systems) may be identified, judgment involved in identifying likely cable paths

- Need a basis for any case where routing is not verified

- Routing by exclusion (e.g., from a fire area, compartment, raceway) is a common and acceptable approach Should consider spurious event(s) contributing to initiators Related PRA standard SR: CS-A11 Fire PRA Workshop 2019, Rockville, MD Slide 15 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Instrument Air Compartment Compartment Compartment Compressor XX YY ZZ Cables judged Compartment Compartment to be here AA BB Compartment Compartment MCCs CC DD Fires cause loss of instrument air Fires assumed to cause loss of Fires assumed to cause loss instrument air of MCC(s) & subsequent effects (including loss of instrument air)

Fire PRA Workshop 2019, Rockville, MD Slide 16 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 4: Identify equipment whose spurious actuation may challenge the safe shutdown capability Examine multiple spurious events within each system considering success criteria PRA standard has specific requirements for multiple spurious events Review system P&IDs, electrical single lines, and other drawings Focus on equipment or failure modes not already on the component list (e.g., flow diversion paths)

Review/Incorporate PRA related scenarios identified by the MSO Expert Panel to identify new components/failure modes Review Internal Events System Notebooks to identify components/failure modes screened based on low probability combinations Fire PRA Workshop 2019, Rockville, MD Slide 17 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 4: Identify equipment whose spurious actuation may challenge the safe shutdown capability (cont.)

Be aware of any failure combinations that could cause or contribute to an initiating event Any new failure combinations that could cause or contribute to an initiating event should be addressed in Step 3 Any new equipment/failure modes should be added to component list for subsequent cable-tracing and circuit analysis Corresponding PRA Standard SRs: ES-B2,B3 Fire PRA Workshop 2019, Rockville, MD Slide 18 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Flow Diversion Path Examples from main to diversion takes 2 spurious flowpath path hot shorts to open diversion Div A MOV Div B MOV path Included in model takes 1 spurious to diversion hot short &

from main path flowpath failure of check Div A MOV valve to open CheckValve diversion path Screened from model if not potential high consequence event Fire PRA Workshop 2019, Rockville, MD Slide 19 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Example of a New Failure Mode of a Component App. R ensures MSIVs will close / remain closed Containment so as to isolate vessel1 Main Steam Line Reactor Vessel Inboard MSIV Outboard MSIV Fire PRA concerned with MSIVs closing / remaining closed AND will not spuriously close when want valves to remain open so as to use condenser as heat sink1 1

different cables and corresponding circuits and analyses may need to be accounted for Fire PRA Workshop 2019, Rockville, MD Slide 20 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel This approach complements but is not part of the published consensus methodology (6850/1011989)

Reference Documents NEI 00-01, Revision 2, Guidance for Post-Fire Safe Shutdown Circuit Analysis, May 2009 Focused on use of the generic list of MSOs provided in Appendix G, and the guidance provided in Section 4.4, Expert Panel Review of MSOs NEI 04-02 Frequently Asked Question (FAQ) 07-0038, Lessons Learned on Multiple Spurious Operations WCAP-16933-NP, Revision 0, PWR Generic List of Fire-Induced Multiple Spurious Operation Scenarios, April 2009 NRC Regulatory Guide 1.205, Risk-Informed, Performance-Based Fire Protection for Existing Light-Water Nuclear Power Plants, Revision 1, December 2009 Fire PRA Workshop 2019, Rockville, MD Slide 21 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Purpose Perform a systematic and complete review of credible spurious and MSO scenarios, and determine whether or not each individual scenario is to be included or excluded from the plant specific list of MSOs to be considered in the plant specific post-fire Fire PRA and Safe Shutdown Analysis (SSA)

Involves group what-if discussions of both general and specific scenarios that may occur Fire PRA Workshop 2019, Rockville, MD Slide 22 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Expert Panel Membership Fire Protection Fire Safe Shutdown Analysis: This expert should be familiar with the SSA input to the expert panel and with the SSA documentation for existing spurious operations PRA: This expert should be familiar with the PRA input to the expert panel Operations System Engineering Electrical Circuits Fire PRA Workshop 2019, Rockville, MD Slide 23 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Process Overview Process is based on a diverse review of the Safe Shutdown Functions.

Panel focuses on system and component interactions that could impact nuclear safety Review and discuss the potential failure modes for each safe shutdown function Identify MSO combinations that could defeat safe shutdown through those failure mechanisms Outputs are used in later tasks to identify cables and potential locations where vulnerabilities could exist MSOs determined to be potentially significant may be added to the PRA model and SSA Fire PRA Workshop 2019, Rockville, MD Slide 24 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Supporting Plant Information for Reviews Flow Diagrams Control Wiring Diagrams Single and/or Three Line Diagrams Safe Shutdown Logic Diagrams PRA Event Sequence Diagrams Post-Fire Safe Shutdown Analysis Fire PRA models, analyses and cutsets Plant operating experience Fire PRA Workshop 2019, Rockville, MD Slide 25 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

MSO Selection Review existing Safe Shutdown Analysis (SSA) list Expand existing MSOs to include all possible component failures Verify SSA assumptions are maintained Review generic list of MSOs (NEI 00-01 Revision 2, Appendix G)

Screen MSOs that do not apply to your plant (i.e., components or system do not exist)

Place all non-screened MSOs on plant specific list of MSOs Evaluate each MSO to determine if it can be screened due to design or operational features that would prevent it from occurring (i.e., breaker racked out during normal operation)

Review the generic MSO list for similar or additional MSOs Develop and evaluate list of new MSOs Fire PRA Workshop 2019, Rockville, MD Slide 26 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

MSO Development Identify MSO combinations that could defeat safe shutdown through the previously identified failure mechanisms The panel will build these MSO combinations into fire scenarios to be investigated The scenario descriptions that result should include the identification of specific components whose failure or spurious operation would result in a loss of a safe shutdown function or lead to core damage Fire PRA Workshop 2019, Rockville, MD Slide 27 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

MSO Development (cont.)

The expert panel systematically reviews each system (P&IDs, etc) affecting safe shutdown and the core for the following Safe Shutdown Functions:

Reactivity Control Decay Heat Removal Reactor Coolant Inventory Control Pressure Control Process Monitoring Support Functions Fire PRA Workshop 2019, Rockville, MD Slide 28 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Typical Generic PWR MSOs Scenario Description Loss of all RCP Spurious isolation of seal injection header flow, AND Seal Cooling Spurious isolation of CCW flow to Thermal Barrier Heat Exchanger (TBHX)

RWST Drain Spurious opening of multiple series containment sump Down via valves Containment Sump Fire PRA Workshop 2019, Rockville, MD Slide 29 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Typical Generic BWR MSOs RPV coolant drain through the Scram MSO opening of the solenoid valves Discharge Volume (SDV) vent and which supply control air to the air drain operated isolation valves Spurious Operations that creates RHR flow can be diverted to the RHR Pump Flow Diversion from containment through the RHR Torus RHR/LPCI, including diversion to the or Suppression Pool return line Torus or Suppression Pool isolation valves (E11-F024A, B and E11-F028A, B)

Fire PRA Workshop 2019, Rockville, MD Slide 30 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection MSO Expert Panel (Cont.)

Outputs and Documentation Plant specific list of MSOs MSO Expert Panel Review Report The MSO Expert Panel is a living entity and the Plant Specific list of MSOs is a living document MSO components that could have PRA impact are addressed in Task 2 MSO scenarios that have PRA impact are addressed in Task 5 Fire PRA Workshop 2019, Rockville, MD Slide 31 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (per 6850/1011989)

Step 5: Identify additional instrumentation/diagnostic equipment important to operator response (level of redundancy matters!)

Identify human actions of interest in conjunction with Task 12 (HRA)

Identify instrumentation and diagnostic equipment associated with credited and potentially harmful human actions considering spurious indications related to each action Is there insufficient redundancy to credit desired actions in EOPs/FEPs/ARPs in spite of failed/spurious indications?

Can a spurious indication(s) cause an undesired action because action is dependent on an indication that could be false?

If yes - Put indication on component list for cable/circuit review See new/expanded guidance developed by the RES/EPRI fire HRA collaboration Corresponding PRA Standard SRs: ES-C1,C2 Fire PRA Workshop 2019, Rockville, MD Slide 32 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details Guidance on identification of harmful spurious operating instrumentation and diagnostic equipment:

Assume instrumentation is in its normal configuration Focus on instrumentation with little redundancy Note that fire PRA standard has language on this subject (i.e.,

verification of instrument redundancy in fire context)

When verification of a spurious indication is required (and reliably performed), it may be eliminated from consideration When multiple and diverse indications must spuriously occur, those failures can be eliminated if the HRA shows that such failures would not likely cause a harmful operator action Include spurious operation of electrical equipment that would cause a faulty indication and harmful action Include inter-system effects Fire PRA Workshop 2019, Rockville, MD Slide 33 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 6: Include potentially high consequence related equipment High consequence events are one or more related failures at least partially caused by fire that:

By themselves cause core damage and large early release, or Single component failures that cause loss of entire safety function and lead directly to core damage Example of first case: Spurious opening of two valves in high-pressure/low pressure RCS interface, leading to ISLOCA Example of second case: Spurious opening of single valve that drains safety injection water source Corresponding PRA Standard SR: ES-A6 Fire PRA Workshop 2019, Rockville, MD Slide 34 Module 1: Internal Event, At-Power PRA Model for SNPP

Task 2: Fire PRA Component Selection Steps In Procedure/Details (Cont.)

Step 7: Assemble Fire PRA component list. Should include following information:

Equipment ID and description (may be indicator or alarm)

System designation Equipment type and location (at least compartment ID)

PRA event ID and description Normal and desired position/status Failed electrical/air position References, comments, and notes Note: Development of an actual/physical fire PRA component list is not a requirement of the PRA Standard Fire PRA Workshop 2019, Rockville, MD Slide 35 Module 1: Internal Event, At-Power PRA Model for SNPP

Sample Problem Exercise for Task 2, Step 1 Distribute blank handout for Task 2, Step 1 Distribute completed handout for Task 2, Step 1 Question and Answer Session Fire PRA Workshop 2019, Rockville, MD Slide 36 Module 1: Internal Event, At-Power PRA Model for SNPP

Sample Problem Exercise for Task 2, Steps 2 and 3 Distribute blank handout for Task 2, Step 2 Distribute completed handout for Task 2, Step 2 Question and Answer Session Discuss Step 3 Question and Answer Session Fire PRA Workshop 2019, Rockville, MD Slide 37 Module 1: Internal Event, At-Power PRA Model for SNPP

Sample Problem Exercise for Task 2, Steps 4 through 6 Distribute blank handout for Task 2, Steps 4 through 6 Distribute completed handout for Task 2, Steps 4 through 6 Question and Answer Session Fire PRA Workshop 2019, Rockville, MD Slide 38 Module 1: Internal Event, At-Power PRA Model for SNPP

Sample Problem Exercise for Task 2, Step 7 Distribute blank handout for Task 2, Step 7 Distribute completed handout for Task 2, Step 7 Question and Answer Session Fire PRA Workshop 2019, Rockville, MD Slide 39 Module 1: Internal Event, At-Power PRA Model for SNPP

Mapping HLRs & SRs for the ES Technical Element to NUREG/CR-6850, EPRI TR 1011989 Technical HLR SR 6850/1011989 Comments element sections that cover SR ES A The Fire PRA shall identify equipment whose failure caused by an initiating fire including spurious operation will contribute to or otherwise cause an initiating event.

1 2.5.3 2 3.5.3 Covered in Cable Selection chapter 3 2.5.3 4 2.5.1, 2.5.4 5 2.5.4 6 2.5.6 B The Fire PRA shall identify equipment whose failure including spurious operation would adversely affect the operability/functionality of that portion of the plant design to be credited in the Fire PRA.

1 2.5.2 2 2.5.4 3 5.5.1 Covered in Fire-Induced Risk Model chapter 4 3.5.3 Covered in Cable Selection chapter 5 n/a Exclusion based on probability is not covered in 6850/1011989 C The Fire PRA shall identify instrumentation whose failure including spurious operation would impact the reliability of operator actions associated with that portion of the plant design to be credited in the Fire PRA.

1 2.5.5 2 2.5.5 D The Fire PRA shall document the Fire PRA equipment selection, including that information about the equipment necessary to support the other Fire PRA tasks (e.g., equipment identification; equipment type; normal, desired, failed states of equipment; etc.) in a manner that facilitates Fire PRA applications, upgrades, and peer review.

1 n/a Documentation not covered in 6850/1011989 Fire PRA Workshop 2019, Rockville, MD Slide 40 Module 1: Internal Event, At-Power PRA Model for SNPP