ML19212A736

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04_17_Fire HRA Training_Recov_Depend_Uncert
ML19212A736
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Issue date: 07/31/2019
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NRC-RES/EPRI FIRE PRA METHODOLOGY:

Task 12 - Fire HRA Recovery, Dependency, Uncertainty Analysis NRC-RES Fire PRA Workshop Module IV August 5-9, 2019 Rockville, MD

Outline of the Presentation

1. Introduction to HRA
2. Overview of the EPRI/NRC Fire HRA Guidelines
3. Identification and definition of fire human failure events
4. Qualitative analysis
5. Fire HRA Application Experience
6. Quantitative analysis a) Screening b) Scoping c) Detailed EPRI approach & ATHEANA (detailed)
7. Recovery analysis (as in cut set post-processing)
8. Dependency analysis
9. Uncertainty analysis Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 2 Fire PRA Workshop 2019, Rockville, MD

Operator Actions in Cutsets (Example)

Cutset Event

  1. Frequency Value Event ID Event Description 1 1.50E-07 2.50E-04 %DBALOCA Design Basis Large LOCA 6.00E-04 OPER-RECIRC Operator Fails to Align SI/CS For Recirculation 2 7.50E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 3.00E-05 ALIGN-HOTLEG Operator Fails to Algin Hot Leg Recirc 3 3.80E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 1.90E-03 CS-MP-10A-S Motor-Driven CS Pump 10A Fails to Start 8.00E-03 CS-MP-10B-M Motor-Driven CS Pump 10B in Test or Maintenance 4 3.80E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 8.00E-03 SI-MP-01A-M Motor-Driven Pump 01A in Test or Maintenance 1.90E-03 SI-MP-01B-S Motor-Driven SI Pump 01B Fails to Start 5 3.80E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 1.90E-03 SI-MP-01A-S Motor-Driven SI Pump 01A Fails to Start 8.00E-03 SI-MP-01B-M Motor-Driven Pump 01B in Test or Maintenance 6 3.60E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 1.44E-05 SI-MV-001-T Motor-Operated Valve 001 Spuriously Operates 7 3.33E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 7.00E-03 SI-HX-01A-M Heat Exchanger 01A in Test or Maintenance 1.90E-03 SI-MP-01B-S Motor-Driven SI Pump 01B Fails to Start 8 3.33E-09 2.50E-04 %DBALOCA Design Basis Large LOCA 7.00E-03 SI-HX-01B-M Heat Exchanger 01B in Test or Maintenance 1.90E-03 SI-MP-01A-S Motor-Driven SI Pump 01A Fails to Start Identify Recovery:

Operator Fails to Manually Control Valve after Spurious

Operator Actions in Fault Trees System SystemFails Fails Recovery to toProvide Provide can be Adequate AdequateFlowFlow within an OROR HFE Pump P1 Inadequate Inadequate T1 T1 Fails to Provide P1 Flow Through OP Flow Through OP-1 Adequate Flow Valves Valve Train 1 Tank T1 OR AND Example 1:

Fails AND Operator Fails to Start Pump P1 P1 V1 V2 FTS FTR P1 InadequateV1 HFE added OP-2 PWR Flow Through as Recovery Pump P1 Pump P1 No Power Valve V1 to Functional Example 2:

Fails to Fails to To Pump P1 OR Failure Operator Start Run for Fails to Open Valve 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> Manually after Auto Fails V1 V1 P1 V1 OP-3 FTO FS MNT PWR Valve V1 Valve V1 Valve Control Left Pump P1 No Power Fails to Spurious Closure Misaligned (so no Auto)

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 4 To Valve V1 Fire PRA Workshop 2019, Rockville, MD In Maintenance Open (Pre-initiator)

Recovery within a Human Failure Event Treated in the evaluation of the basic HEP.

Examples include:

- Self-review such as Procedure-related checks.

- Peer checking within a shift or after shift change..

- Shift Technical Advisor (STA) review.

EPRI HRA Approach - addressed via Cognitive Recovered and Execution Recovered modules - CBDTM per EPRI TR-100259

- Based on the time available for recovery.

ATHEANA Approach - treated directly via conditional probabilities

- When qualitative information is first converted into a quantitative estimate of the HEP, recovery of any initial error is addressed to the extent appropriate.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 5 Fire PRA Workshop 2019, Rockville, MD

Recovery at the Cutset Level PRA Standard definition - Restoration of a function lost as a result of a failed system, structure, or component (SSC) by overcoming or compensating for its failure.

Generally modeled by using HRA techniques.

Adding cutset level recovery actions is common practice in PRA, and adds realism based on expected plant response.

Credits feasible & reasonable actions that were not included previously in the PRA Corresponding PRA Standard SRs: Part 2, HR-H Part 4, HRA-D1 and -D2 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 6 Fire PRA Workshop 2019, Rockville, MD

Recovery per the PRA Standard HLRs Supporting Requirements generally follow fire SR HRA-D:

  • HLR-HRA-D: The Fire PRA shall include recovery actions only if it has been demonstrated that the action is plausible and feasible for those scenarios to which it applies, particularly accounting for the effects of fires (2 SRs)

Additional supporting requirements reference recovery:

  • HLR-AS-A: The accident sequence..scenarios shall address.

operator actions, including recovery actions (11 SRs)

  • HLR-QU-A5: Include recovery actions in quantification
  • HLR-HR-H: This HLR is analogous to HLR-HRA-D for Fire Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 7 Fire PRA Workshop 2019, Rockville, MD

Recovery Analysis Fire HRA Recovery uses the same process as for other fire HFEs 1.Identification and Definition

- Consider existing internal events PRA recovery actions

- From cutset review, identify risk-significant sequences with recovery potential

- From fire and post-trip action procedures, use recovery-related steps to identify new recovery HFEs

- Feasibility analysis is required, the same as for any new human failure events.

NUREG-1792, HRA Good Practices NUREG/CR-6850 (EPRI 1011989)

NUREG-1921, Sections 3.5 and 4.3 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 8 Fire PRA Workshop 2019, Rockville, MD

Feasibility Consideration from Circuit Analysis (per NUREG/CR-6850 [EPRI 1011989])

In some cases, electrical cable failures will result in permanent damage to electrical or mechanical equipment that precludes certain types of recovery actions.

- For example, MOVs with modified torque and/or limit switches to respond to IN 92-18.

- Spurious operation of an MOV due to a hot short that bypasses the valves torque switch might cause permanent binding of the valve, precluding manual operation of the valve at a later time Cases of this nature should be documented and discussed with systems analysts to ensure recovery actions accurately reflect the prevailing conditions.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 9 Fire PRA Workshop 2019, Rockville, MD

Recovery Analysis Fire HRA (continued)

2. Qualitative Analysis

- Review cutsets & the event tree to define the sequence progression and key functional successes and failures that the operators must address (the scenario context).

- Talk-through procedure-based recovery actions with operators or training personnel.

3. Quantification using the NUREG-1921 approaches

- Often using Detailed Fire HRA as recovery is generally done for the risk-significant cutsets.

Recommended to ensure thorough analysis of timing, PSFs and context

- Could use Scoping or Screening for cutsets that are not significant

4. Incorporation into fire PRA model, including review of Dependency between HFEs (next training topic))

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 10 Fire PRA Workshop 2019, Rockville, MD

Other Uses of the Term Recovery Not in NUREG-1921

1. System or Component restoration based on empirical data

- Modeled directly with data, not HRA..

- Examples:. Recovery of Offsite Power, or Repair

2. NFPA 805 Recovery Actions typically mitigate a Variance from Deterministic Criteria (VFDR) such as cable separation

- NFPA 805, Section 1.6.52, defines a recovery action as activities to achieve the nuclear safety performance criteria that take place outside the main control room or outside the primary control station(s) where a primary control station Dedicated shutdown or alternative shutdown controls, which have been reviewed and approved by the NRC.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 11 Fire PRA Workshop 2019, Rockville, MD

Outline of the Presentation

1. Overview of the EPRI/NRC Fire HRA Guidelines
2. Identification and definition of fire human failure events
3. Qualitative analysis
4. Quantitative analysis a) Screening b) Scoping c) EPRI approach (detailed) d) ATHEANA (detailed)
5. Recovery analysis
6. Dependency analysis
7. Uncertainty analysis Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 12 Fire PRA Workshop 2019, Rockville, MD

Dependency Overview HFE1 COG + EXE Time HFE2 COG + EXE Time HFE1 Cue HFE2 Cue Failure (or success) in one task Time can influence the likelihood of failure (or success) in a subsequent task.

Factors that affect this dependence often include:

- Tasks are performed closely in time.

- Same operator performing both tasks.

- Tasks performed in the same locality.

- Tasks are directed by the same procedure.

- Tasks are initiated based on the same cue.

The strength of the influence of the factor varies.

Treatment of dependency in the model can be affected by the PRA as well as the HRA quantification method.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 13 Fire PRA Workshop 2019, Rockville, MD

Dependency Analysis Evaluation Process Dependency evaluation

- ASME/ANS PRA standard requires that multiple human actions in an accident sequence or cutset be identified, degree of dependency assessed, and joint HEP calculated Steps

1. Identify combinations of multiple operator actions in fire scenario (regardless if screening, scoping or detailed quantification)
2. Evaluate dependencies within scenario
3. Incorporate dependency evaluation into Fire PRA model Application

- For Fire PRA, preliminary dependency analysis performed in combination with NUREG/CR-6850 (EPRI 1011989) Task 11, Detailed Fire Modeling & finalized as part of Task 14, Fire Risk Quantification Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 14 Fire PRA Workshop 2019, Rockville, MD

Applicable Requirements (HLRs per the PRA Standard)

Dependency

  • HLR-AS-B: Dependencies that can impact the ability of the mitigating systems to operate and function shall be addressed (7 SRs)
  • HLR-HR-G: The assessment of the probabilities of the post-initiator HFEs shall be performed using a well-defined and self-consistent process that addresses the plant-specific and scenario-specific influences on human performance, and addresses potential dependencies between human failure events in the same accident sequence (8 SRs)
  • HLR-QU-C: Model quantification shall determine that all identified dependencies are addressed appropriately (3 SRs)
  • HLR-FQ-C: [Fire Risk] Model quantification shall determine that all identified dependencies are addressed appropriately (1 SR)

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 15 Fire PRA Workshop 2019, Rockville, MD

Dependency Analysis Basic Dependency Ground Rules Ground rules applicable to EPRI HRA & ATHEANA approaches

- The first HFE in a sequence is always independent EPRI HRA approach from THERP

- The EPRI HRA approach looks for common causal factors, termed common cognitive.

- Dependence impact is one-directional in chronological order.

- The THERP dependence model (called positive dependence) is adopted, i.e., failure of an event increases the probability of failure of a subsequent event.

- In a chronological sequence, an HFE depends only on the immediately preceding HFE (given no common cognitive element).

- An HFE is independent of an immediately preceding, relevant success.

ATHEANA approach considers the context & collective set of actions (actions required for success as well as Unsafe Actions)

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 16 Fire PRA Workshop 2019, Rockville, MD

Dependency Analysis EPRI Approach First, identify cutsets containing multiple operator actions Approaches to evaluate the combinations of operator actions:

1. Use actual data from simulators

- Highly resource intensive, and probably not practical

2. Analyze each HFE combination in detail

- Highly resource intensive but more comprehensive

3. Assume complete dependence (only credit 1 HFE per cutset)

- Not resource intensive

- Impact on risk metric could be unacceptably over-conservative

4. Apply a systematic set of rules to assign different levels of dependence (recommended approach)

- Moderate resource requirements

- Impact on risk metric could be acceptable Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 17 Fire PRA Workshop 2019, Rockville, MD

Dependency Analysis EPRI Levels of Dependence Intervening Dependence Crew Cognitive Cue Demand Manpower Location Sequential Timing Stress Case Success Level

  • Dependency Common 1 CD Factors High or Moderate 2 CD Same 3

HD Sufficient

- Same Crew Same Simultaneous Different High or Moderate 5

4 MD LD

- Cognition Insufficient 6 CD (cues/proced High or Moderate 7 CD 0-15 ure) 8 HD Different High or Moderate 9 HD 15-30

- Timing 10 MD No Same High or Moderate 11 MD 30-60

- Resources High or Moderate 12 13 LD

- Location LD Sequential >(60-120) 14 ZD

- Stress High or Moderate 15 LD Different 16 ZD High or Moderate 17 LD Different 18 ZD Yes 19 ZD

Dependency Analysis EPRI Dependency Formulas from THERP For example, for two HFEs with HEP1 = 1E-3, HEP2 = 1E-3 that occur in a combination HFE1 HFE2, the Conditional HEP (CHEP) for HFE2 and the Joint HEP (JHEP) for a given level of dependence (DL) are:

Conditional Conditional HEP HEP2 Joint HEP Level Equation (given initial (HEP1 X CHEP2)

HEP1 is 1E-3)

Zero HEP1 1.00E-03 1.00E-06 Low (1+19 X HEP1) / 20 5.10E-02 5.10E-05 Medium (1+ 6 X HEP1) / 7 1.44E-01 1.44E-04 High (1 + HEP1) / 2 5.01E-01 5.01E-04 Complete 1 1.00E+00 1.00E-03 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 19 Fire PRA Workshop 2019, Rockville, MD

Example-1:

EPRI Joint HEP Calculation HFE1 COG + EXE Time HFE2 COG + EXE Time HFE1 Cue HFE2 Cue Given the following two HFEs in a cutset Time

- HEP1: Operators fail to actuate SI

- HEP2: Operators fail cooldown and depressurization Calculate the Joint HEP for failure to actuate SI and failure to cooldown and depressurize given Moderate dependency HEP CHEP2 HEP1 CHEP2 JHEP Calculation JHEP 2 Calculation 4.5E-4 1E-3 1.43E-1 HEP1x CHEP2 6.44E-5

= 4.5E-4 x 1.43E-1 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 20 Fire PRA Workshop 2019, Rockville, MD

ATHEANA consideration of dependency In ATHEANA, the potential for multiple Unsafe Actions (UA) contributing to a particular HFE is considered.

- By breaking the HFE into UAs, the specific dependency can be modeled more appropriately and explicitly.

Modeling and analyzing at the UA level provides the means to explicitly investigate the potential impact of different UAs on the plant response, as well as on other human actions ATHEANA considers dependency when there is a significant perceived dependency between a particular UA associated with the HFE and some other human failure modeled in the PRA (either upstream or downstream in the chain of events depicted by the PRA sequence)

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 21 Fire PRA Workshop 2019, Rockville, MD

Outline of the Presentation

1. Overview of the EPRI/NRC Fire HRA Guidelines
2. Identification and definition of fire human failure events
3. Qualitative analysis
4. Quantitative analysis a) Screening b) Scoping c) EPRI approach (detailed) d) ATHEANA (detailed)
5. Recovery analysis
6. Dependency analysis
7. Uncertainty analysis Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 22 Fire PRA Workshop 2019, Rockville, MD

Uncertainty Definitions Uncertainty in the context of PRA and HRA is defined as the representation of the confidence in the state of knowledge about the parameter values and models used in constructing the PRA Uncertainty analysis process:

- Identify and characterize sources of uncertainty

- Evaluate their impact on the PRA results, and

- Developing a quantitative measure, or means to measure, to the extent practical Guidance now available via NUREG-1855 (Rev 1) and EPRI 1016737 on parameter and modeling uncertainties in PRA Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 23 Fire PRA Workshop 2019, Rockville, MD

Applicable HLRs (per the PRA Standard)

Uncertainty

  • HLR-HR-G: The assessment of the probabilities of the post-initiator HFEs shall be performed using a well-defined and self-consistent process that addresses the plant-specific and scenario-specific influences on human performance, and addresses potential dependencies between human failure events in the same accident sequence (8 SRs)
  • HLR-QU-E: Uncertainties in the PRA results shall be characterized. Sources of model uncertainty and related assumptions shall be identified, and their potential impact on the results understood (4 SRs)
  • HLR-UNC-A: The Fire PRA shall identify sources of CDF and LERF uncertainties and related assumptions and modeling approximations. These uncertainties shall be characterized such that their potential impacts on the results are understood (2 SRs)

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 24 Fire PRA Workshop 2019, Rockville, MD

Uncertainty Overview For fire HRA, uncertainties are addressed in the same manner as for internal events HRA The HRA should characterize the uncertainty in the estimates of the HEPs consistent with the quantification approach, and provide mean values for use in quantification In fire HRA, key assumptions may include timing or selections of performance shaping factors Corresponding PRA Standard SRs: Part 2, HR-G8, QU-E3 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 25 Fire PRA Workshop 2019, Rockville, MD

Examples of issues contributing to Fire HRA Uncertainty Operators rely on a set of instruments as reliable information sources.

- Those instruments whose cables were not traced may or may not be affected by the fire.

- Uncertainty is the amount of distraction & time lost.

Fire response procedures are generally on an area-basis, but the detailed fire modeling shows there can be a wide range of fire-induced initiating event.

- The Fire PRA model may know the specific context.

- The operator may need time to recognize and understand the fire impacts.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 26 Fire PRA Workshop 2019, Rockville, MD

Uncertainty Analysis Potential Sources of HRA Modeling Uncertainty Category Potential Sources of Input Uncertainty Timing data inputs (Tsw, Tdelay, Tcog, and Texe) where Tdelay can be impacted by uncertainty due to the scenario such as the procedure step with the cue may be different for one initiator than another initiator. Example, start AFW from ES-0.1 vs.

FR-H1.

Timing Impact of timing variations on short time window or time constrained scenarios.

Ability to obtain more than one operators input to timing estimates to reduce variability.

Impact on cues such that the indications may not be accurate.

Cues (including spurious) Compelling indications or cues that may distract the operator from the modeled task.

Scenario such that there is the potential for several spurious alarms or indications.

Stress Assessment of stress Workload Assessment of workload Training Frequent and specific enough to be known when needed?

Impact of single versus multiple procedures.

Procedures Plant-specific procedures not in standard format.

Factors that would suggest an increased dependency level such as a common Dependency cognitive impact (both HFEs operating from the same cue).

Sources of Uncertainty are Identified, then can be evaluated as Sensitivity Studies Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 27 Fire PRA Workshop 2019, Rockville, MD

Uncertainty on the HEP Uncertainty using the EPRI Approach to Detailed FHRA Cognitive:

- HEP estimation using CBDT method - driven by uncertainties on assessment of decision tree branch points, e.g.,

- Adequacy of training, clarity of procedures

- Quality of Human-Machine Interface

- HEP estimation using HCR/ORE method:

Uncertainty in HEP is affected by uncertainties in

- T1/2 = Crew median response time

- TW = TSW -Tdelay- TEXE so a function of uncertainty in inputs

- = Deviation between crews Execution: HEP estimation using THERP where the approach is to assign an EF solely based on HEP from THERP Table 20-20 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 28 Fire PRA Workshop 2019, Rockville, MD

Uncertainty in detailed HRA ATHEANA ATHEANA uncertainty analysis is performed by developing probability distributions using expert elicitation The facilitator, with the assistance of the experts, puts forth two questions that progressively move the entire group from a qualitative evaluation to a quantitative estimate of the HEP and its uncertainty distribution:

1. Given all the relevant evidence, how difficult or challenging is the action of interest for the scenario/context and why?
2. Hence, what is the probability distribution for the HEP that best reflects this level of difficulty or challenge considering uncertainty?

Applications of ATHEANA have found it useful to first provide a calibration mechanism for the experts to begin to interpret their qualitative conclusions into a probability Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 29 Fire PRA Workshop 2019, Rockville, MD

ATHEANA -

Suggested Set of Initial Calibration Points for the Experts Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 30 Fire PRA Workshop 2019, Rockville, MD

Uncertainty Analysis References NUREG-1855, Guidance on the Treatment of Uncertainties Associated with PRAs in Risk-Informed Decision Making, Rev.

1, Draft for Comment March 2013 EPRI 1016737, Treatment of Parameter and Model Uncertainty for Probabilistic Risk Assessments, December 2008 NUREG-1880, ATHEANA Users Guide, June 2007 EPRI 1009652, Guideline For Treatment of Uncertainty In Risk-Informed Applications, December 2005 NUREG-1792, Good Practices for Implementing Human Reliability Analysis (HRA), Sandia National Laboratories, 2005 NUREG/CR-1278, "Handbook of Human Reliability Analysis with Emphasis on Nuclear Power Plant Applications," (THERP)

Swain, A.D. and Guttmann, H. E., August 1983 Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 31 Fire PRA Workshop 2019, Rockville, MD

Examples of fire recovery actions Fire Initiated Scenario Type Operator Objective (not Selected HFE for recovery recovery)

Fire induced loss of DC power Override and control MSIS OP FT control ESFAS and causes spurious ESFAS with during fire, if nothing done ADV given Fire normal cues then primary safeties lift in about 80 min.

Fire induced trip with Loss of Provide makeup to CST 121 OP FT Provide Makeup to CST CST Makeup for AFW with following a fire given fire normal cues Fire induced LOCA: Pzr valve Respond to loss of primary OP FT Depressurize to 3/4 inch line open coolant and establish secondary Containment Spray Pump cooling during fire Shutoff Head given fire with sample line open Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 33 Fire PRA Workshop 2019, Rockville, MD

Consideration of procedures and timing for fire recovery actions Standard Time Supplemental Fire Time POST TRIP Fire Operator Actions HFE Required Procedure Window ACTIONS Scenario for Fire Description (diagnosis + FIRE AOI SO23-13-21 (Tsw) EOI SO23 execution) R18 1 R22 MSIS Override and OP FT control 40 80 Step 8 VERIFY Attachment 2- 12.0 AFW, isolation control MSIS ESFAS and RCS Heat MSS, MFW OPERATIONS (spurious during fire, if ADV given Removal then go to 3.0 ADV from fire) nothing done then Fire with criteria satisfied Operations (3.1.3) "When with primary safeties lift Normal Cues MSIS isolation an ADV is needed, then normal in about 80 min. OK use ADVs OPERATE HV-8421 (for a cues and AFW Train A shutdown), or HV-8419 (for a Train B shutdown), in Local/Manual per SO23 2.18.1, Attachment for Local Manual Operation of HV-8419(HV-8421)

Atmospheric Dump Valves.

Fire HRA - Recovery, Dependency, Uncertainty Analysis Slide 34 Fire PRA Workshop 2019, Rockville, MD

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