ML19212A730
| ML19212A730 | |
| Person / Time | |
|---|---|
| Issue date: | 07/31/2019 |
| From: | Office of Nuclear Regulatory Research |
| To: | |
| D. Stroup 415-1649 | |
| Shared Package | |
| ML19212A718 | List: |
| References | |
| Download: ML19212A730 (62) | |
Text
NRC-RES/EPRI FIRE PRA METHODOLOGY Task 12 - Fire HRA Scoping Quantification Approach NRC-RES Fire PRA Workshop Module IV August 5-9, 2019 Rockville, MD
Course Overview
- 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
- 8. Dependency analysis
Three General Approaches to HRA Quantification Screening: Slightly modified from NUREG/CR-6850 (EPRI 1011989) to cover late (after fire is out) events Scoping fire HRA quantification approach (new)
- Less conservative than screening, but designed to be slightly more conservative than detailed approaches
- Some actions may result in an HEP of 1.0 Two detailed fire HRA quantification approaches, modified for application in fire scenarios
- EPRI Cause-Based Decision Tree Method (CBDTM) &
HCR/ORE; THERP
- ATHEANA Fire HRA - Scoping Method Slide 3 Fire PRA Workshop 2019, Rockville, MD
Purpose of Scoping Approach Provides less conservative but more realistic HEPs for HFEs surviving screening
- Straightforward approach
- HEPs generally more conservative than those obtained with more detailed analysis
- Limits need for detailed analysis for many HEPs Relies on feasibility assessment and time margin to account for many of the uncertainties associated with fire scenarios (e.g., per NUREG-1852)
Requires simple judgments about PSFs Fire HRA - Scoping Method Slide 4 Fire PRA Workshop 2019, Rockville, MD
Categories of Actions Addressed in Scoping Flowcharts New and existing main control room (MCR) actions New and existing local (ex-control room) actions Actions associated with using alternate shutdown means
- due to MCR habitability issues, or
- due to difficulties in controlling the plant from the MCR because of the effects of the fire Recovery of Errors of Commission (EOCs) or Errors of Omission (EOOs) due to spurious instrumentation
- Supports addressing spurious instrument effects as described in Part 4 (Internal Fires) of ASME/ANS Combined PRA Standard (HLR-ES-C1 and C2)
Fire HRA - Scoping Method Slide 5 Fire PRA Workshop 2019, Rockville, MD
Categories of Actions NOT Addressed in Scoping Flowcharts Complex diagnosis should not be addressed with the Scoping Method
- Simplified approach not appropriate for cognitively complex or challenging scenarios Example of cognitively complex or challenging scenarios:
- Cues directly relevant to the action being modeled do not match the procedural guidance
- Plants that implement SISBO procedures
- Actions pertaining to deciding to abandon the MCR*
- Scenarios that may include potentially distracting spurious operations
- scoping approach may be used to quantify HFEs subsequent to the decision to abandon.
Fire HRA - Scoping Method Slide 6 Fire PRA Workshop 2019, Rockville, MD
Steps for Using Scoping Fire HRA Approach
- 1. Ensure minimum criteria are met
- 2. Assess feasibility of operator actions
- 3. Calculate time margin
- 4. Assess key conditions and PSFs
- 5. Use flowcharts to quantify
- 6. Selection scheme directs to one of the following:
INCR = In MCR actions EXCR = ex-MCR actions (actions normally performed locally)
ASD = Alternative Shutdown (including MCR Abandonment due to habitability or transferring command and control to outside the MCR due to an inability to control the plant)
SPI = recovery of errors due to spurious instrumentation Fire HRA - Scoping Method Slide 7 Fire PRA Workshop 2019, Rockville, MD
Minimum Criteria
- 1. Procedures
- Should match the scenario
- Should cover each operator action being modeled
- Support both diagnosis & execution of the action
- Exceptions:
Execution of skill-of-the-craft actions Recovery of EOO or EOC in some cases related to self-or crew-recovery for inappropriate response to spurious indications
- 2. Training - on the procedures and the actions
- 3. Availability and accessibility of equipment Fire HRA - Scoping Method Slide 8 Fire PRA Workshop 2019, Rockville, MD
Assessment of Feasibility in Scoping HRA Examines information regarding the action, context, scenario and timing Primarily based on action/scenario timing and environmental conditions (dense smoke)
Refer to Qualitative Analysis presentation sections on Tools for Feasibility Assessment and conducting Talk-and Walk-throughs, as well as NUREG-1921 sections:
- 4.3 Feasibility Assessment
- 4.11 Reviews with Plant Operations Fire HRA - Scoping Method Slide 9 Fire PRA Workshop 2019, Rockville, MD
Feasibility Assessment Factors Sufficient time*
- Timeline used to model operator performance
- Sources of timing information (e.g., job performance measures
[JPMs], training exercises, Appendix R feasibility demonstrations)
Sufficient manpower (both inside and outside control room)
Primary cues available/sufficient (e.g., is there a fire impact?)
Proceduralized and trained (plus certain skill-of-the-craft actions)
- See NUREG-1921, Sections 4.3.4.1 Sufficient Time & 4.6.2 PSFs - Timing Fire HRA - Scoping Method Slide 10 Fire PRA Workshop 2019, Rockville, MD
Feasibility Assessment Factors (contd)
Proceduralized and trained
- Plus certain skill-of-the-craft actions Accessible location (both travel path and action location; effects of environmental and security measures must be considered)
Equipment and tools available and accessible, e.g.,
- Keys for locked doors
- Radios, ladders, flashlights, protective clothing, SCBA Fire HRA - Scoping Method Slide 11 Fire PRA Workshop 2019, Rockville, MD
Time Margin Extra time included to account for potential fire effects and variabilities, such as:
- Uncertainties from conditions unable to be simulated in training
- Potential variability in crew response times and individual differences
- Variations in fire type and related plant conditions Within the scoping approach, time margins are required to be calculated for all actions or set of actions Time estimates should be as realistic as possible
- Look for tipping points meaning situations where time available ~ time to respond Similar to guidance in NUREG-1852 Fire HRA - Scoping Method Slide 12 Fire PRA Workshop 2019, Rockville, MD
Calculation of Time Margin Tsw Tavail Treqd Tdelay Tcog Texe T0 Cue Crew Action Action no received diagnosis complete longer Start complete beneficial Fire HRA - Scoping Method Slide 13 Fire PRA Workshop 2019, Rockville, MD
Calculation of Time Margin (continued)
Some actions may involve either (or a mix of both) serial and parallel actions, with overlapping tasks
- In these cases, determination of the time margin may not be as straightforward as illustrated
- For more guidance, see Appendix A of NUREG-1852.
Tipping Points - a few additional minutes of estimated time results in different HEP in scoping method
- Range of times should be collected, not just a point estimate
- Initially choose conservative time estimate and refine later if HEP significantly impacts fire PRA model quantification results Fire HRA - Scoping Method Slide 14 Fire PRA Workshop 2019, Rockville, MD
Assessing Key Conditions & PSFs within the Scoping Flowcharts
- Procedures (criteria for using Scoping)
- Should match the scenario
- Should be relatively easy to follow given the pattern of indications
- Serves as a proxy for diagnostic complexity
- Response action execution complexity
- Assessed as high or low
- Complexity is usually considered low if:
Requires a single step Performed by a single crew member Multiple simple steps performed by single crew members working independently Clear procedures or skill-of-craft
- Complexity is usually considered high if:
Multiple steps that may be ambiguous or difficult Multiple crew members performing coordinated steps Multiple location steps if coordination/communication required Multiple functions (e.g., both electrical and mechanical alignment)
Fire HRA - Scoping Method Slide 15 Fire PRA Workshop 2019, Rockville, MD
Assessing Key Conditions & PSFs within the Scoping Flowcharts (continued)
Timing of cues for the action relative to expected fire suppression time.
- If fire type unknown, fire suppression assumed to be 70-minutes (all fires)
- If fire type is known, may use the 99th %ile value (yellow) from FAQ 08-0050 (NUREG 6850 supplement 1, or NUREG-2169)
- Fire must be considered on-going for the fire types in red Outdoor Flammab Electrical Transient PWR T/G fires Oil fires Welding All Fires Control High Time energy Cable transform containm le gas fires fires (min) arcing Room fires faults ers ent 0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 1.0 5 0.883 0.947 0.836 0.881 0.684 0.602 0.531 0.687 0.392 0.189 0.446 0.714 10 0.780 0.897 0.698 0.776 0.468 0.362 0.282 0.472 0.153 0.036 0.199 0.510 15 0.689 0.850 0.584 0.683 0.320 0.218 0.150 0.325 0.060 0.007 0.089 0.364 20 0.609 0.805 0.488 0.602 0.219 0.131 0.080 0.223 0.024 0.001 0.040 0.260 25 0.538 0.762 0.408 0.530 0.150 0.079 0.042 0.153 0.009
- 0.018 0.186 30 0.475 0.722 0.341 0.467 0.102 0.048 0.023 0.105 0.004
- 0.008 0.133 35 0.419 0.684 0.285 0.411 0.070 0.029 0.012 0.072 0.001
- 0.004 0.095 40 0.370 0.647 0.238 0.362 0.048 0.017 0.006 0.050 *
- 0.002 0.068 45 0.327 0.613 0.199 0.319 0.033 0.010 0.003 0.034 * *
- 0.048 50 0.289 0.581 0.166 0.281 0.022 0.006 0.002 0.024 * *
- 0.035 55 0.255 0.550 0.139 0.248 0.015 0.004
- 0.016 * *
- 0.025 60 0.226 0.521 0.116 0.218 0.010 0.002
- 0.011 * *
- 0.018 65 0.199 0.493 0.097 0.192 0.007 0.001
- 0.008 * *
- 0.013 70 0.176 0.467 0.081 0.169 0.005 *
- 0.005 * *
- 0.009 75 0.155 0.443 0.068 0.149 0.003 *
- 0.004 * *
- 0.006 80 0.137 0.419 0.057 0.131 0.002 *
- 0.002 * *
- 0.005 85 0.121 0.397 0.047 0.116 0.002 *
- 0.002 * *
- 0.003 90 0.107 0.376 0.040 0.102 0.001 *
- 0.001 * *
- 0.002 95 0.095 0.356 0.033 0.090 * * * * * *
- 0.002 100 0.084 0.337 0.028 0.079 * * * * * *
Assessing Key Conditions & PSFs within the Scoping Flowcharts (continued)
Action time window
- Time from the occurrence of the cues for action until the action is no longer beneficial
- Short time window = 30 minutes or less
- Long time window = greater than 30 minutes Level of smoke and other hazardous elements in the action areas
- Need for special equipment (e.g., SCBA)
- Impairment of vision or prevention of the execution of the action Accessibility
- Location of action
- Travel path Fire HRA - Scoping Method Slide 17 Fire PRA Workshop 2019, Rockville, MD
Use of Scoping Flowcharts HFEs quantified based on:
- Assessment of key PSFs
- Location of the actions associated with the HFE
- Condition of relevant instrumentation A Search Scheme directs the analyst to the correct flowchart for quantification:
- In-MCR action (INCR)
- Ex-MCR action (EXCR)
- Alternative Shutdown (ASD)
- Recovery of error due to spurious instrumentation (SPI)
Some HFEs quantified within the Search Scheme lead to HEP = 1.0 Fire HRA - Scoping Method Slide 18 Fire PRA Workshop 2019, Rockville, MD
Selection Scheme Directs analyst to correct quantification flowchart Fire HRA - Scoping Method Slide 19 Fire PRA Workshop 2019, Rockville, MD
Selection Scheme Direct to ASD or SPI tree Cues are not necessary to answer yes to D1, but likely their absence will still result in HEP = 1.0 later on Fire HRA - Scoping Method Slide 20 Fire PRA Workshop 2019, Rockville, MD
Selection Scheme Directs analyst to correct quantification flowchart Fire HRA - Scoping Method Slide 21 Fire PRA Workshop 2019, Rockville, MD
Selection Scheme Direct to INCR or EXCR Fire HRA - Scoping Method Slide 22 Fire PRA Workshop 2019, Rockville, MD
INCR - In-MCR Actions Used for the following HFEs:
- New HFEs identified outside the Internal Events PRA, such as for Fire
- Existing HFEs from the Internal Events that survive quantitative screening Addresses diagnosis and execution of the action in the MCR
- Presumes no challenge to MCR habitability or functionality from fire (see ASD)
Fire HRA - Scoping Method Slide 23 Fire PRA Workshop 2019, Rockville, MD
INCR Scoping HRA for in MCR Actions Fire HRA - Scoping Method Slide 24 Fire PRA Workshop 2019, Rockville, MD
INCR Fire Suppressed?
- 70 minutes from reactor trip
- Fire specific timing [FAQ-08-0050]
- Challenging fires (e.g., turbine generator fires) assume fire has not been suppressed.
Fire HRA - Scoping Method Slide 25 Fire PRA Workshop 2019, Rockville, MD
INCR Scoping HRA for in MCR Actions Fire HRA - Scoping Method Slide 26 Fire PRA Workshop 2019, Rockville, MD
INCR Fire on-going Short time window (<30 min)
Fire HRA - Scoping Method Slide 27 Fire PRA Workshop 2019, Rockville, MD
INCR Scoping HRA for in MCR Actions Fire HRA - Scoping Method Slide 28 Fire PRA Workshop 2019, Rockville, MD
INCR Fire on-going Long time window (>30 min)
Fire HRA - Scoping Method Slide 29 Fire PRA Workshop 2019, Rockville, MD
INCR Look-up Table HEP Lookup Table Time Margin HEP HEP Label A > 100% 0.005 INCR2 50 - 99% 0.025 INCR3
< 50% 1.0 INCR4 B > 100%
50 - 99%
0.025 0.125 INCR5 INCR6 Note that some C
< 50%
> 100%
1.0 0.001 INCR7 INCR8 tables (e.g., G) 50 - 99%
< 50%
0.005 1.0 INCR9 INCR10 absorb the 50-99%
D > 100% 0.005 INCR11 TM into one <100%
50 - 99% 0.025 INCR12
< 50% 1.0 INCR13 because multiplying E > 100% 0.05 INCR14 50 - 99% 0.25 INCR15 the >100% TM by 5
< 50% 1.0 INCR16 F > 100% 0.1 INCR17 already causes 50 - 99% 0.5 INCR18
< 50% 1.0 INCR19 HEP=1 G > 100% 0.2 INCR20
< 100% 1.0 INCR21 H > 100% 0.25 INCR22
< 100% 1.0 INCR23 I > 100% 0.5 INCR24
< 100% 1.0 INCR25 J > 100% 0.01 INCR26 50 - 99% 0.05 INCR27
< 50% 1.0 INCR28 K > 100% 0.02 INCR29 50 - 99% 0.1 INCR30
< 50% 1.0 INCR31 L > 100% 0.04 INCR32 50 - 99% 0.2 INCR33
< 50% 1.0 INCR34 M > 100% 0.05 INCR35 50 - 99% 0.25 INCR36
< 50% 1.0 INCR37 N > 100% 0.1 INCR38 50 - 99% 0.5 INCR39
< 50% 1.0 INCR40 O > 100% 0.2 INCR41
< 100% 1.0 INCR42 Fire HRA - Scoping Method Slide 30 Fire PRA Workshop 2019, Rockville, MD
EXCR - Ex-MCR Actions Also addresses new and existing HFEs Addresses diagnosis and execution of the action(s)
- Diagnosis within the MCR
- Execution locally (i.e., ex-MCR)
If action is require both in the MCR and locally, this tree should be used Major differences from INCR tree
- Action location accessibility?
- Presence of dense smoke or other impact to visibility?
Fire HRA - Scoping Method Slide 31 Fire PRA Workshop 2019, Rockville, MD
EXCR Scoping HRA for ex-MCR Actions Fire HRA - Scoping Method Slide 32 Fire PRA Workshop 2019, Rockville, MD
EXCR
- Fire Suppressed?
- 70 minutes from reactor trip
- Fire specific timing
[FAQ-08-0050]
- Challenging fires (e.g., turbine generator fires) assume fire has not been suppressed.
Fire HRA - Scoping Method Slide 33 Fire PRA Workshop 2019, Rockville, MD
EXCR Scoping HRA for ex-MCR Actions Fire HRA - Scoping Method Slide 34 Fire PRA Workshop 2019, Rockville, MD
EXCR Fire on-going Short time window
(< 30 min)
Fire HRA - Scoping Method Slide 35 Fire PRA Workshop 2019, Rockville, MD
EXCR Scoping HRA for ex-MCR Actions Fire HRA - Scoping Method Slide 36 Fire PRA Workshop 2019, Rockville, MD
EXCR Fire on-going Long time window
(> 30 min)
Fire HRA - Scoping Method Slide 37 Fire PRA Workshop 2019, Rockville, MD
EXCR Look-up Table HEP Lookup Table Time Margin HEP HEP Label
> 100% 0.01 EXCR6 P 50 - 99% 0.05 EXCR7
< 50% 1.0 EXCR8
> 100% 0.05 EXCR9 Q 50 - 99% 0.25 EXCR10
< 50% 1.0 EXCR11
> 100% 0.002 EXCR12 R 50 - 99% 0.01 EXCR13
< 50% 1.0 EXCR14
> 100% 0.01 EXCR15 S 50 - 99% 0.05 EXCR16
< 50% 1.0 EXCR17
> 100% 0.5 EXCR18 T
< 100% 1.0 EXCR19
> 100% 0.1 EXCR20 U 50 - 99% 0.5 EXCR21
< 50% 1.0 EXCR22
> 100% 0.2 EXCR23 V
< 100% 1.0 EXCR24
> 100% 0.4 EXCR25 W
< 100% 1.0 EXCR26
> 100% 0.02 EXCR27 X 50 - 99% 0.1 EXCR28
< 50% 1.0 EXCR29
> 100% 0.04 EXCR30 Y 50 - 99% 0.2 EXCR31
< 50% 1.0 EXCR32
> 100% 0.08 EXCR33 Z 50 - 99% 0.4 EXCR34
< 50% 1.0 EXCR35
> 100% 0.1 EXCR36 AA 50 - 99% 0.5 EXCR37
< 50% 1.0 EXCR38
> 100% 0.2 EXCR39 AB
< 100% 1.0 EXCR40
> 100% 0.4 EXCR41 AC
< 100% 1.0 EXCR42 Fire HRA - Scoping Method Slide 38 Fire PRA Workshop 2019, Rockville, MD
ASD - Alternative Shutdown Application to 2 situations:
- Uninhabitable environment in MCR
- Transfer of command and control to outside the MCR due to an inability to control the plant (loss of MCR functionality)
If the crew decides to stay in the MCR (i.e., direct the crew response and perform actions from the MCR to the extent possible), but collect some information or take some actions outside the MCR as necessary to reach safe shutdown (referred to as remote shutdown), actions should be quantified as ex-MCR actions and the EXCR flowchart should be used Differences from INCR tree:
- Instruments supporting cues necessary for diagnosis protected from fire effects?
- Action location accessibility & not in direct fire path?
- Presence of dense smoke or other impact to visibility?
Fire HRA - Scoping Method Slide 39 Fire PRA Workshop 2019, Rockville, MD
ASD Scoping HRA for Alternative Shutdown Actions Fire HRA - Scoping Method Slide 40 Fire PRA Workshop 2019, Rockville, MD
ASD D41 refers to diagnosis D42 refers to execution Fire HRA - Scoping Method Slide 41 Fire PRA Workshop 2019, Rockville, MD
ASD Scoping HRA for Alternative Shutdown Actions Fire HRA - Scoping Method Slide 42 Fire PRA Workshop 2019, Rockville, MD
ASD Short time window (< 30 min)
Fire HRA - Scoping Method Slide 43 Fire PRA Workshop 2019, Rockville, MD
ASD Scoping HRA for Alternative Shutdown Actions Fire HRA - Scoping Method Slide 44 Fire PRA Workshop 2019, Rockville, MD
ASD Long time window (> 30 min)
Fire HRA - Scoping Method Slide 45 Fire PRA Workshop 2019, Rockville, MD
ASD Look-up Table HEP Lookup Table Time Margin HEP* HEP Label
> 100% 0.2 ASD9 AD
< 100% 1.0 ASD10
> 100% 0.4 ASD11 AE
< 100% 1.0 ASD12
> 100% 0.8 ASD13 AF
< 100% 1.0 ASD14
> 100% 0.04 ASD15 AG 50 - 99% 0.2 ASD16
< 50% 1.0 ASD17
> 100% 0.08 ASD18 AH 50 - 99% 0.4 ASD19
< 50% 1.0 ASD20
> 100% 0.16 ASD21 AI 50 - 99% 0.8 ASD22
< 50% 1.0 ASD23
> 100% 0.2 ASD24 AJ
< 100% 1.0 ASD25
> 100% 0.4 ASD26 AK
< 100% 1.0 ASD27
> 100% 0.8 ASD28 AL
< 100% 1.0 ASD29 Fire HRA - Scoping Method Slide 46 Fire PRA Workshop 2019, Rockville, MD
SPI - EOC or EOO Due to Spurious Instrumentation Assumes the EOC or EOO has been committed &
quantifies the probability that the error would remain uncorrected Assume an EOC or EOO if:
- Cables are routed through the fire area*
- Instrumentation not required for an Appendix R action, so cannot assume it is protected by fire barrier wrap
- Single affected instrument can lead operator to take action Dont assume an EOC or EOO if:
- Operator is suspicious of the equipment or instrument because it may be suspect due to location of fire
- Demonstrated redundancy and diversity
- or routing is not known (exclusion approach)
Fire HRA - Scoping Method Slide 47 Fire PRA Workshop 2019, Rockville, MD
SPI - Spurious Instrumentation Spurious instrumentation refers to the instrumentation necessary for the operator to diagnose the action (e.g.,
expected cues from the procedure)
Analyst judgment required in cases of partial spurious indication (e.g., 2 out of 4 instruments fail vs. 2 out of 10 instruments fail). In these cases the analyst should consider:
- How do the instruments fail?
- Is it likely to cause the operator to fail to diagnose the problem?
Fire HRA - Scoping Method Slide 48 Fire PRA Workshop 2019, Rockville, MD
SPI - Recovery of an EOC or EOO Recovery prompted by either:
- Procedural guidance
- Contextual information or subsequent cues in conjunction with existing procedures Recognition for need to recover may be either through:
- Recognition of an error
- Recognition of the need for the function Recovery possible by:
- Reversal of the action (EOC)
- Use of alternative system (EOC)
- Performance of the necessary action (EOO)
Fire HRA - Scoping Method Slide 49 Fire PRA Workshop 2019, Rockville, MD
SPI Scoping HRA for EOC or EOO due to spurious instrumentation Fire HRA - Scoping Method Slide 50 Fire PRA Workshop 2019, Rockville, MD
SPI Initial questions Fire HRA - Scoping Method Slide 51 Fire PRA Workshop 2019, Rockville, MD
SPI Scoping HRA for EOC or EOO due to spurious instrumentation Fire HRA - Scoping Method Slide 52 Fire PRA Workshop 2019, Rockville, MD
SPI Action completed within the MCR Fire HRA - Scoping Method Slide 53 Fire PRA Workshop 2019, Rockville, MD
SPI Scoping HRA for EOC or EOO due to spurious instrumentation Fire HRA - Scoping Method Slide 54 Fire PRA Workshop 2019, Rockville, MD
SPI Action completed locally (ex-MCR)
Fire HRA - Scoping Method Slide 55 Fire PRA Workshop 2019, Rockville, MD
SPI Look-up Table
> 100% 0.25 SPI11 AM
< 100% 1.0 SPI12
> 100% 0.5 SPI13 AN
< 100% 1.0 SPI14
> 100% 0.05 SPI15 AO 50 - 99% 0.25 SPI16
< 50% 1.0 SPI17
> 100% 0.1 SPI18 AP 50 - 99% 0.5 SPI19
< 50% 1.0 SPI20
> 100% 0.2 SPI21 AQ
< 100% 1.0 SPI22
> 100% 0.25 SPI23 AR
< 100% 1.0 SPI24
> 100% 0.5 SPI25 AS
< 100% 1.0 SPI26
> 100% 0.1 SPI27 AT 50 - 99% 0.5 SPI28
< 50% 1.0 SPI29
> 100% 0.2 SPI30 AU
< 100% 1.0 SPI31
> 100% 0.4 SPI32 AV
< 100% 1.0 SPI33
> 100% 0.5 SPI34 AW
< 100% 1.0 SPI35
> 100% 0.5 SPI36 AX
< 100% 1.0 SPI37 Fire HRA - Scoping Method Slide 56 Fire PRA Workshop 2019, Rockville, MD
HEP Values Base HEP = 1E-3 (lowest attainable value)
Within a flowchart, HEP values are based on:
- Timing of the cue for an action relative to start of fire
- Length of action time window
- Level of execution complexity
- Level of smoke (area of action & travel path)
- Accessibility of action site (area of action & travel path)
Fire HRA - Scoping Method Slide 57 Fire PRA Workshop 2019, Rockville, MD
Multipliers Applied to HEPs Within Flowchart HEPs adjusted within a flowchart
- Fire effects ongoing - significant increase
- Action time window 30 mins - moderate increase
- High execution complexity - moderate increase
- Increases in smoke level - slight increase
- Decrease in time margin - moderate increase HEPs based in part on amount of time margin (TM) available
- TM < 50%
- 50% < TM < 100%
- TM > 100%
Fire HRA - Scoping Method Slide 58 Fire PRA Workshop 2019, Rockville, MD
Multipliers Applied to HEPs Across Flowcharts HEP in Base Flowchart Adjustment Value HEP in Scoping Flowchart INCR 2 EXCR EXCR 2 ASD INCR for in-MCR actions; 5 SPI EXCR for ex-MCR actions Change in PSF Scoping Approach Multipliers Fire effects ongoing (i.e., < 70 minutes 10 from the start of the fire)
Action time window < 30 minutes 5 High execution complexity 5 Increases in smoke level 2 Decreases in time margin:
from > 100% to 50%-99% 5 from > 50% to < 50% Set HEP = 1.0 Fire HRA - Scoping Method Slide 59 Fire PRA Workshop 2019, Rockville, MD
Summary of Scoping Quantification
Purpose:
- Offers less conservative and more realistic HEPs compared to the screening approach
- More conservative but less resource intensive than more detailed HRA methods
- Categories:
- In-MCR or local (ex-MCR) actions
- Alternative shutdown
- Recovery of errors due to spurious instrumentation
- Quantification:
- Relies on assessment of feasibility of actions, time margin, and simple judgments about a few PSFs
- Quantification performed through use of flowcharts Fire HRA - Scoping Method Slide 60 Fire PRA Workshop 2019, Rockville, MD
Conclusions on Scoping Analysis Useful to address actions for which
- Screening analysis is inadequate
- Additional resources required for detailed analysis may be unwarranted More detailed analyses should be pursued when
- Conditions are beyond those addressed by scoping approach
- Resulting HFEs continue to be significant contributors to risk Examples via Handouts Fire HRA - Scoping Method Slide 61 Fire PRA Workshop 2019, Rockville, MD
Questions?
Fire HRA - Scoping Method Slide 62 Fire PRA Workshop 2019, Rockville, MD