ML19212A733
| ML19212A733 | |
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| Issue date: | 07/31/2019 |
| From: | Office of Nuclear Regulatory Research |
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| D. Stroup 415-1649 | |
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NRC-RES/EPRI FIRE PRA METHODOLOGY Task 12 - Fire HRA EPRI Approach to Detailed Fire HRA Quantification Examples 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
- 8. Dependency analysis
EPRI HRA CalculatorTM EPRI software was used, but is not required.
EPRI HRA Calculator TM version 4.1.1 was used for following examples.
Current version of the software is version 5.1 EPRI Approach Examples Slide 3 Fire PRA Workshop 2019, Rockville, MD
Assumptions for Examples Example Plant is a 2-loop Westinghouse PWR using Standard Westinghouse EOPs Fire PRA modeling is developed sufficiently
- Detailed scenario descriptions and information available Fire Response Procedures
- Implemented in parallel to the EOPs, and
- Operators enter the fire procedures at the same time as they enter the EOPs Fire and reactor trip modeled to occur at the same time (T=0)
EPRI Approach Examples Slide 4 Fire PRA Workshop 2019, Rockville, MD
Crew Composition For Example Problems Staffing: Minimum staffing of the plant is as follows:
Inside Control Room: Outside Control Room:
Shift Manager* (SM)
Local Plant Operators Crew #
Shift Supervisor (SS) Shift Technical Auxiliary Operators 3 Advisor** (STA) Turbine Hall Operator 2 Unit 1 Aux bldg/Water Treatment 2 Control Control Control Operator Operator Operator*** Crew composition and titles are (OPER1) (OPER2) (OPER3) plant specific
- Dealing with high-level management issues (e.g., communicating with NRC)
- Can be outside CR. Will be in CR within 10 minutes of reactor trip.
Division of Labor During Fire Scenario Following detection of fire, some crew members become members of the fire brigade and are unable to assist in actions directed by the control room. The fire brigades only duty is to extinguish the fire.
Total # Assisting # Available *This includes members of fire Crew Member Available with fire* for EOP brigade and staff occupied with Before Fire actions FPs or otherwise occupied due to the fire Shift Manager 1 1 0 Shift Supervisor 1 0 1 STA 1 0 1 Control Room Operators 2 1 1 Plant operators 7 4 3 The EPRI approach reflects the plant practice that while the fire is ongoing no members of the fire brigade are available to assist with local or control room actions.
EPRI Approach Examples Slide 6 Fire PRA Workshop 2019, Rockville, MD
Generic Fire Response Timeline (Plant-specific information may vary)
Time (Minutes)
T=0 Fire causes reactor trip T=0 Control room receives fire alarm and actives fire brigade Control room sends local operator to investigate fire T=5 Control room starts implementing fire procedures in parallel to EOPs T=10 Fire brigade is expected to be assembled and fighting fire within 10 minutes of activations T=15 Emergency Response Facility (ERF) activated and unusual event declared. Typical, plant policy states that if a fire is not under control within 15 minutes must declare unusual event.
T=70 Fire is out 99% of all fires are extinguished per FAQ 50 EPRI Approach Examples Slide 7 Fire PRA Workshop 2019, Rockville, MD
Example 1 - Operator fails to manually align 115kV bus (SBO)
Initial Conditions:
Steady state, full power operation.
- Minimal staff on shift.
- No out-of-service safe shutdown equipment.
Initiating Event: Fire in turbine hall causes SBO HFE: Operator fails to manually align 115kV (alternate power) power following loss of both buses.
EPRI Approach Examples Slide 8 Fire PRA Workshop 2019, Rockville, MD
Accident Sequence & Success Criteria Accident Sequence o Fire causes reactor trip o Reactor trip and turbine trip successful.
o AFW failed due to the fire.
o PORV spuriously opens due to the fire.
o The Main Generator breaker opens and the BOP buses are powered through XTF0001 (reverse) and XTF0002.
o EDG A is failed by the fire and fails to start.
o EDG B starts and the Engineered Safety Feature (ESF) Loading Sequencer loads onto bus.
o EDG B trips due to fire damage. The ESF Loading Sequencer is still sending a signal to trip the normal and alternate feeder breakers (for EDG protection) to the bus.
o All diesels failed - SBO o DC power remains available until batteries deplete. Batteries will last for 4 hrs EPRI Approach Examples Slide 9 Fire PRA Workshop 2019, Rockville, MD
Accident Sequence (continued)
Operators Success Criteria o Locally trip the alternate feeder breaker by removing power from the ESFLS to remove the trip open signal.
o Energize XSW1DA or 1DB from the alternate power source.
Consequence of failure: Core damage due to stuck open PORV EPRI Approach Examples Slide 10 Fire PRA Workshop 2019, Rockville, MD
Expected Crew Response Time Event Comment T=0min Fire and Reactor Trip T=0min Control Room dispatches fire brigade to fight the fire; Fire brigade comprised of 3 Local Plant Operators immediate memorized actions (steps 1-3 EOP 0) performed T=3min EOP 0, step 3 indicates SBO. Procedure transition brief OPER1 designated to perform ECA 0.0; OPER2 designated to held by SS to alert all control room staff that they have an start reviews of fire procedures SBO and fire. They will be entering ECA 0.0 T=5min OPER1 begins ECA 0.0 T=7min Step 4 ECA 0.0 dispatch local plant operator to Assume this Local Plant Operator will be tied up restoring AFW investigate failure of AFW and not available to assist in additional actions T=10min STA arrives Begins monitoring critical safety functions T=15min OPER1 reaches step 10 ECA 0.0, notifies SS that they By this time OPER2 has finished reading through fire need to transition to AOP 304 procedures T=15min SS briefs control room staff on the AOP coordination with 7 contingent time critical action (need in the first hr) in fire the fire procedures procedure; 2 necessary. Confirmed: fire procedure actions will not interfere with AOP actions; sufficient personnel available to do both in parallel. Late actions (>4hr) are postponed until SBO is recovered.
T=20min OPER1 begins AOP 304; OPER2 begins directing fire OPER2 dispatches 1 local plant operator to perform fire procedure actions procedure actions T=35min OPER1 arrives at step 17 of AOP 304 (locally remove Cue for action power from ESFLS)
EPRI Approach Examples Slide 11 Fire PRA Workshop 2019, Rockville, MD
Expected Procedure Progression o Upon Reactor Trip, enter EOP-0 o Step 3 of EOP-0 verifies that buses are energized. Buses are de-energized; this will take the operator to ECA 0.0 [Station Blackout Procedure]
o Step 10 of ECA 0.0 checks that buses 1DB and 1 DA are energized. Both buses are de-energized; this will take the operator to AOP 304 due to loss of bus with no EDG.
o Step 13 of AOP 304 directs the crew to determine cause of loss of ESF bus o Steps 17 and 18 of AOP 34 provide the execution steps.
EPRI Approach Examples Slide 12 Fire PRA Workshop 2019, Rockville, MD
Cognitive Procedure Guidance EPRI Approach Examples Slide 13 Fire PRA Workshop 2019, Rockville, MD
Execution Procedure Guidance Steps 17 and 18 of AOP 304 are the relevant execution steps for this HFE:
EPRI Approach Examples Slide 14 Fire PRA Workshop 2019, Rockville, MD
Cues The cues for this HFE are straight forward however communication between control room and local operators will be impacted by the SBO and the fire.
The control room operators direct local operators to investigate for problems and then report back to the control room.
The travel pathways are not blocked by the fire EPRI Approach Examples Slide 15 Fire PRA Workshop 2019, Rockville, MD
Simulator Observation (SBO non-fire scenario)
Procedure/step Time (Minutes) Comments : Cue; Feedback; Confusing; Additional information required Initial Conditions 0 G01 out of service Unit trip on loss of 1X03 and 1X04. Bus transfer H02 to H01 did not occur, 1a05 EOP-0 dead (G01 OOS, G02 failed to start) and 1A06 powered from G03.
Step 1 & 2 Lost power on 1A06, G03 tripped off - Transition to ECA-0.0 0 EOP-0 Immediate actions started EOP-0 Verify Safeguard buses energized Step 3 Transition to ECA 0.0 There was a short team brief to make the announcement that there was a transition RNO 2 to ECA 0.0 ECA-0.0 Steps 1&2 5 Verify reactor trip and turbine trip ECA-0.0 Step 3 7 Maintain RCS Inventory ECA-0.0 Verified 1P29 AFW pump on and feeding both SGs Step 4 CRO makes call for local RO to investigate TDAFW and try and start AFW.
RNO 8 Then briefs STA on status of TDAFW ECA-0.0 Step6 9 Attempted start of G02, failed.
ECA-0.0 Attempted start of G03, failed -
Step 7 9 GO to Step 10 ECA-0.0 Check 1DB bus and 1DA are energized Step 10 RNO If 1DA is de-energized Go to AOP-304.01 (LOSS OF BUS 1DA WITH THE DIESEL NOT AVAILABLE) 10 If 1DB is de-energized Go to AOP-304.02 (LOSS OF BUS 1DB WITH THE DIESEL NOT AVAILABLE)
EPRI Approach Examples Slide 16 Fire PRA Workshop 2019, Rockville, MD
Timing o T = 0 Start of fire and reactor trip o TSW = 90 minutes Time to core damage based on an IPE thermal hydraulic run for loss of AFW and a station blackout with one primary PORV stuck open.
o Tdelay = 30 minutes from reactor trip unit operators reach step 13 Based on simulator observation for a similar scenario for SBO it took operators 10 minutes to get through ECA 0.0 step 10 Simulation based on non-fire SBO so an additional time has been added to account for fire impacts.
It is estimated that it will take about 10 minutes to reach step 13 of AOP-304 Tdelay=20+10 minutes o Tcog = 10 minutes based on operator interviews. This is the time operators estimated it would take to locally investigate status of breaker.
This includes time for the SS and STA to confer, coordinate with the fire procedures, approve the action and communicate to control room operators to commence steps 17 and 18.
EPRI Approach Examples Slide 17 Fire PRA Workshop 2019, Rockville, MD
Timing (contd) o Texe = 20 minutes o The action to locally remove power from the Train B ESF Loading Sequencer is trained on using Job Performance Measure (JPM) 12654 - Align ALT Feed Breaker. This JPM has a time requirement to be able to complete the local portion of the actions within 15 minutes, and this has been verified by observations of the JPM. The timing starts once the operator is given the instructions to perform this action and ends once the MCR action had been complete (end of step 18).
o As part of this JPM the operators train on putting on flash gear which is required to locally remove power from the Train B ESF Loading Sequencer. The flash gear is stored in a cabinet at the entrance to the relay room.
o After the operators complete the local action they will need to return to the control room to tell the control room operators they were successful. This additional travel time is expected to take 5 minutes.
o Under ideal conditions the Local Plant Operator could use the phone to call the control room. However, for fire, no cable tracing was performed on the phone lines so the telephones are assumed to unavailable.
o Texe = 15 minutes + 5 minutes = 20 minutes EPRI Approach Examples Slide 18 Fire PRA Workshop 2019, Rockville, MD
Timeline Based on timeline a moderate dependency is considered for recovery EPRI Approach Examples Slide 19 Fire PRA Workshop 2019, Rockville, MD
CBDTM - Unrecovered EPRI Approach Examples Slide 20 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-a Data not available Warning or Indication Indication Alternative Training on pc a Available in Accurate in Indication CR Procedure From the control room the operators can determine that the (a) neg.
bus is failed. However the procedure directs the operators to (b) neg.
locally verify the status of the bus (c) neg.
(d) 1.5E-03 Yes (e) 5.0E-02 No (f) 5.0E-01 (g)
CBDTM decision tree:
pc-b Data not attended to pcb Low vs. high Check vs. Front vs. back Alarmed vs. Nominal workload monitor panel not alarmed probability Front Check (a) neg.
Alarmed Back (b) 1.5E-4 Low Not alarmed (c) 3.0E-3 Alarmed Front (d) 1.5E-4 Yes Not alarmed Monitor (e) 3.0E-3 No Alarmed Back (f) 3.0E-4 Not alarmed (g) 6.0E-3 Alarmed Front (h) neg.
Not alarmed Check (i) neg.
Alarmed Back (j) 7.5E-4 Not alarmed High (k) 1.5E-2 Alarmed (l) 7.5E-4 Front Not alarmed (m) 1.5E-2 Monitor Alarmed (n) 1.5E-3 Back Not alarmed (o) 3.0E-2 EPRI Approach Examples Slide 22 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-c Data misread or miscommunicated pcc Indicator easy Good/bad Formal com- Nominal to locate indicator munications probability (a) neg.
(b) 3.0E-3 (c) 1.0E-3 Yes (d) 4.0E-3 No (e) 3.0E-3 (f) 6.0E-3 (g) 4.0E-3 (h) 7.0E-3 EPRI Approach Examples Slide 23 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-d Information misleading pcd All cues as Warning of Specific General Nominal stated differences training training probability Yes (a) neg.
No (b) 3.0E-3 (c) 1.0E-2 (d) 1.0E-1 (e) 1.0 EPRI Approach Examples Slide 24 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-e Relevant step in procedure missed pce Obvious vs. Single vs. Graphically Placekeeping Nominal hidden multiple distinct aids probability (a) 1.0E-3 Single (b) 3.0E-3 Obvious (c) 3.0E-3 (d) 1.0E-2 (e) 2.0E-3 Multiple (f) 4.0E-3 (g) 6.0E-3 Yes (h) 1.3E-2 No Hidden (i) 1.0E-1 EPRI Approach Examples Slide 25 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-f Misinterpret instruction Standard, pcf unambiguous All required Training on Nominal wording information step probability (a) neg.
(b) 3.0E-3 (c) 3.0E-2 Yes (d) 3.0E-3 No (e) 3.0E-2 (f) 6.0E-3 (g) 6.0E-2 EPRI Approach Examples Slide 26 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-g Error in interpreting logic pcg Not And or or Both and Practiced Nominal statement statement and or scenario probability (a) 1.6E-2 (b) 4.9E-2 (c) 6.0E-3 (d) 1.9E-2 (e) 2.0E-3 Yes (f) 6.0E-3 (g) 1.0E-2 No (h) 3.1E-2 (i) 3.0E-4 (j) 1.0E-3 (k) neg.
(l) neg.
EPRI Approach Examples Slide 27 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-h Deliberate violation Belief in Adverse Policy of adequacy of consequence Reasonable verbatim Nominal pch instruction if comply alternative compliance probability Yes (a) neg.
(b) 5.0E-1 No (c) 1.0 (d) neg.
(e) neg.
EPRI Approach Examples Slide 28 Fire PRA Workshop 2019, Rockville, MD
CBDTM Summary Unrecovered EPRI Approach Examples Slide 29 Fire PRA Workshop 2019, Rockville, MD
No recoveries are applied to Pcc because there are no extra operators available to assist in locally investigating the status of the bus and reporting back to the control room EPRI Approach Examples Slide 30 Fire PRA Workshop 2019, Rockville, MD
Execution PSFs Environment:
Availability and Accessibility: Given location of fire and layout of plant, the relay room is accessible and there is no degraded environment (e.g., no smoke) in the relay room or en route to the relay room.
Visibility: Given a SBO event, lighting will be significantly reduced (i.e., flashlights and/or emergency lighting).
Communications: Under ideal conditions the local plant operator could use the phone to call the control room. However, for the fire, no cable tracing was performed on the phone lines so the telephones are assumed to unavailable.
Heat/Humidity: Normal - fire effects do not reach this area, however, after some time (>action window) there could be a rise in temperature due to SBO.
Special Requirements:
Operators are required to wear flash gear to locally remove power from the Train A ESF Loading Sequencer.
Operators will need key to access relay rooms due to loss of power all doors will be locked.
EPRI Approach Examples Slide 31 Fire PRA Workshop 2019, Rockville, MD
Portable lighting due to SBO and operators may need to use flashlights Tools are selected because the operators are required to obtain keys from the control room.
The operators are required to wear flash Execution is considered to gear to perform the local action be complex due to the communication required between control room and local plant operators EPRI Approach Examples Slide 32 Fire PRA Workshop 2019, Rockville, MD
EPRI Stress Decision Tree EPRI Approach Examples Slide 33 Fire PRA Workshop 2019, Rockville, MD
Critical Steps (Execution) o LOCALLY Reset ESFLS to clear trip signal Plant Operator, stationed at or near the MCR, gets ESFLS panel key from the MCR and proceeds to the Relay Room Dons flash gear Opens left cabinet (~2ft from floor) and locally removes power from the loading sequencer Alert control operator that the trip signal is clear and that break can closed from the control room o Close Breaker in MCR Ensure BUS 1DA XFER INIT Switch is in OFF Close BUS 1DA ALT FEED Breaker Verify BUS 1DA potential lights are energized EPRI Approach Examples Slide 34 Fire PRA Workshop 2019, Rockville, MD
EPRI Approach Examples Slide 35 Fire PRA Workshop 2019, Rockville, MD EPRI Approach Examples Slide 36 Fire PRA Workshop 2019, Rockville, MD Execution Summary EPRI Approach Examples Slide 37 Fire PRA Workshop 2019, Rockville, MD
Summary Results EPRI Approach Examples Slide 38 Fire PRA Workshop 2019, Rockville, MD
Example 2 Operators fail to perform feed and bleed during a fire For this example, the HFE has been quantified in detail for internal events EPRI Approach Examples Slide 39 Fire PRA Workshop 2019, Rockville, MD
Scenario Description Initial Conditions:
- Steady state, full power operation. Night shift with minimal staff onsite.
- No out-of-service unavailability pertinent to this scenario Initiating Event: Fire in turbine hall causes reactor trip. IE - TRANS HFE: Operators fail to perform feed and bleed (fire)
Fire Impacts: The fire fails AFW, MFW and 2/4 SG level indicators in the control room.
EPRI Approach Examples Slide 40 Fire PRA Workshop 2019, Rockville, MD
Accident Sequence Operator fails to perform feed and bleed EPRI Approach Examples Slide 41 Fire PRA Workshop 2019, Rockville, MD
Procedure FR-H.1
- 11. Check For Loss Of Secondary Heat Sink: Return to Step 1 WR S/G Level LESS THAN 15% in 2 S/G EPRI Approach Examples Slide 42 Fire PRA Workshop 2019, Rockville, MD
Procedure FR-H.1 EPRI Approach Examples Slide 43 Fire PRA Workshop 2019, Rockville, MD
Procedure FR-H.1 EPRI Approach Examples Slide 44 Fire PRA Workshop 2019, Rockville, MD
Fire Procedure EPRI Approach Examples Slide 45 Fire PRA Workshop 2019, Rockville, MD
Timeline T = 0 reactor trip and start of the fire Tsw = 60 minutes -time to SG dryout Tdelay= 20 minutes -time to cue Texe = 5 minutes - time to execute and procedurally verify execution steps. (Based on operator interviews)
For internal events
- Tcog=1 minutes (all cues and indications are accurate)
For fire case with 2/4 SG levels impacted
- Tcog=5 minutes to determine which SG levels indicators are accurate.
EPRI Approach Examples Slide 46 Fire PRA Workshop 2019, Rockville, MD
Timeline For fire analysis dependency level assigned is MD For internal events case dependency level assigned is LD EPRI Approach Examples Slide 47 Fire PRA Workshop 2019, Rockville, MD
Cues and Indications SG level in both SGs less than 15%
Same cue as for internal events except the fire has impacted 2/4 SG level indicators Cue is considered to be poor EPRI Approach Examples Slide 48 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-a Data not available Warning or Indication Indication Alternative Training on Internal pc a Available in CR Accurate in Indication events Procedure selection (a) neg. Fire selection (b) neg.
(c) neg.
(d) 1.5E-03 Yes (e) 5.0E-02 No (f) 5.0E-01 (g)
CBDTM decision tree:
pc-b Data not attended to Internal pcb Low vs. high workload Check vs.
monitor Front vs. back panel Alarmed vs.
not alarmed Nominal probability events Check Front (a) neg.
selection Alarmed Back (b) 1.5E-4 Low Not alarmed (c) 3.0E-3 Fire Alarmed Yes Front (d) 1.5E-4 selection Not alarmed Monitor (e) 3.0E-3 No Alarmed Back (f) 3.0E-4 Not alarmed (g) 6.0E-3 Alarmed Front (h) neg.
Not alarmed Check (i) neg.
Alarmed Back (j) 7.5E-4 Not alarmed High (k) 1.5E-2 Alarmed (l) 7.5E-4 Front Not alarmed (m) 1.5E-2 Monitor Alarmed (n) 1.5E-3 Back Not alarmed (o) 3.0E-2 EPRI Approach Examples Slide 50 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-c Data misread or miscommunicated Fire Internal selection events selection pcc Indicator easy Good/bad Formal com- Nominal to locate indicator munications probability (a) neg.
(b) 3.0E-3 (c) 1.0E-3 Yes (d) 4.0E-3 No (e) 3.0E-3 (f) 6.0E-3 (g) 4.0E-3 (h) 7.0E-3 EPRI Approach Examples Slide 51 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-d Information misleading pcd All cues as Warning of Specific General Nominal stated differences training training probability Yes (a) neg.
No (b) 3.0E-3 (c) 1.0E-2 (d) 1.0E-1 (e) 1.0 Internal Fire events selection selection EPRI Approach Examples Slide 52 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-e Relevant step in procedure missed pce Obvious vs. Single vs. Graphically Placekeeping Nominal hidden multiple distinct aids probability Internal (a) 1.0E-3 events selection Single (b) 3.0E-3 Obvious (c) 3.0E-3 Fire selection (d) 1.0E-2 (e) 2.0E-3 Multiple (f) 4.0E-3 (g) 6.0E-3 Yes (h) 1.3E-2 No Hidden (i) 1.0E-1 EPRI Approach Examples Slide 53 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-f Misinterpret instruction Standard, pcf unambiguous All required Training on Nominal wording information step probability (a) neg.
(b) 3.0E-3 (c) 3.0E-2 Yes (d) 3.0E-3 No (e) 3.0E-2 (f) 6.0E-3 (g) 6.0E-2 Internal Fire events selection selection EPRI Approach Examples Slide 54 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-g Error in interpreting logic pcg Not And or or Both and Practiced Nominal statement statement and or scenario probability Internal (a) 1.6E-2 events (b) 4.9E-2 selection (c) 6.0E-3 (d) 1.9E-2 (e) 2.0E-3 Fire selection Yes (f) 6.0E-3 (g) 1.0E-2 No (h) 3.1E-2 (i) 3.0E-4 (j) 1.0E-3 (k) neg.
(l) neg.
EPRI Approach Examples Slide 55 Fire PRA Workshop 2019, Rockville, MD
CBDTM decision tree:
pc-h Deliberate violation Belief in Adverse Policy of adequacy of consequence Reasonable verbatim Nominal pch instruction if comply alternative compliance probability Yes (a) neg.
(b) 5.0E-1 No (c) 1.0 (d) neg.
(e) neg.
Internal Fire events selection selection EPRI Approach Examples Slide 56 Fire PRA Workshop 2019, Rockville, MD
CBDTM Unrecovered = 1.7E-1 No credit has been given to the usage of the fire procedures EPRI Approach Examples Slide 57 Fire PRA Workshop 2019, Rockville, MD
Calculation of Recovery Factor Using CBDTM an HEP for operators fail to enter fire procedure and diagnose failed indications can be calculated.
Cue - Fire alarm in the control room. The fire alarm will direct the operators to the fire procedure and correct attachment Timeline - This action occurs concurrently with other FR-H.1 actions.
- Tsw= 55 minutes -Longest time in which operators can delay entering FR-H.1 and still successfully perform feed and bleed (60 minutes-5 minutes)
- Tdelay= 5 minutes - Time to enter fire procedures
- Tcog = 5 minutes - Time to determine which indications are correct.
- Texe = 5 minutes - Tm is the time to implement feed and bleed. This time needs to be included to determine the correct time available for recovery.
EPRI Approach Examples Slide 58 Fire PRA Workshop 2019, Rockville, MD
Calculation of Recovery Factor MD Dependency Recovery HEP 1.4E-1 Recovery HEP is calculated to be 6E-3 and does not include dependencies.
Based on timing a Moderate dependency is assigned.
Recovery HEP with dependency is (1+ 6 X6E-3) / 7 =1.4E-1 Pcog with recoveries is 2.3E-2 EPRI Approach Examples Slide 59 Fire PRA Workshop 2019, Rockville, MD
Execution Same execution steps as for Internal Events EPRI Approach Examples Slide 60 Fire PRA Workshop 2019, Rockville, MD
Execution Recovery Moderate dependency is assigned for recovery EPRI Approach Examples Slide 61 Fire PRA Workshop 2019, Rockville, MD
Execution PSFs Fire is outside the control room and has no impact on the control room.
Stress is the same as for internal events Internal Fire events selection selection EPRI Approach Examples Slide 62 Fire PRA Workshop 2019, Rockville, MD
HEP Summary Operator fails to perform feed and bleed during fire with 2/4 SG levels impacted Operator fails to perform feed and bleed (internal events)
EPRI Approach Examples Slide 63 Fire PRA Workshop 2019, Rockville, MD