ML15222A347

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Presentation for 8-11-15 Public Meeting on Main Control Room Abandonment
ML15222A347
Person / Time
Site: Waterford Entergy icon.png
Issue date: 08/11/2015
From: Michael Orenak
Plant Licensing Branch IV
To:
Entergy Operations
Wang A
References
Download: ML15222A347 (24)
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Text

Waterford 3 MCR Abandonment Public Meeting NFPA 805 LAR Waterford 3 Main Control Room (MCR)

Abandonment Analysis Public Meeting August 11, 2015 Waterford 3 MCR Abandonment Public Meeting 1

Agenda

  • Introductions
  • Purpose
  • Evacuation of MCR (Procedure Overview)
  • MCR Abandonment Modeling

- Time Determination

- Scenario Development

- Human Reliability Analysis (HRA)

- Equipment Failures

- CCDP & CLERP

  • Variances from Deterministic Requirements (VFDR)

- VFDR Development

- VFDR Post Transition Modeling

  • Conclusions Waterford 3 MCR Abandonment Public Meeting 2

Introductions

  • John Jarrell - Manager, Regulatory Assurance
  • Mark Thigpen - Design Engineering, PRA
  • Kevin Fitzsimmons - NFPA 805 Project Manager (c)
  • Ricky Summitt - PRA Consultant (RSC Engineers)
  • Andy Spotts - PRA Consultant (JENSEN HUGHES)

(c) denotes on-site contractor Waterford 3 MCR Abandonment Public Meeting 3

Purpose Explain methods and assumptions used to develop the MCR Abandonment Fire PRA and provide insights into responses to PRA RAIs S04 and S04.01 to provide assurance that results obtained have a sound and acceptable basis.

Waterford 3 MCR Abandonment Public Meeting 4

MCR and Remote Shutdown Panel Overview Main Control Room (RAB 1A)

+46' Elev

+35 Relay Room (RAB 7)

Cable Spreading Room (RAB 1E) +35' Elev Remote Shutdown Panel (RAB 9)

A, B & A/B Switchgear LCP-43 (RAB 8)

+21' Elev Waterford 3 MCR Abandonment Public Meeting 5

Evacuation of MCR (Procedure Overview)

  • Upon confirmation of Cable Spreading Room or Main Control Room Fire, Shift Manager determines need to evacuate.
  • Main Control Room Actions
  • Recovery Actions
  • Actions to transfer control to LCP-43
  • Safe and Stable condition verified
  • Plant conditions maintained until decision to:

- Return to Main Control Room

- Proceed to Cold Shutdown Waterford 3 MCR Abandonment Public Meeting 6

MCR Abandonment Modeling

  • Timing determination
  • Scenario development
  • Human Action modeling
  • Equipment Failure (minor to major loss of function)
  • CCDP and CLERP values Waterford 3 MCR Abandonment Public Meeting 7

Time Determination

  • Loss of Habitability

- CFAST modeling used to determine abandonment times due to habitability

- CFAST results used for SF*NSP factor development for habitability abandonment scenarios (NUREG/CR 6850 Appendix E)

- Average abandonment time is approximately 14.6 minutes for scenarios in the Fire PRA

- At this point the operators would implement MCR abandonment per OP-901-502 Waterford 3 MCR Abandonment Public Meeting 8

Time Determination

  • Loss of Control

- Timing for loss of control is scenario-specific for various ignition sources

- Damage timing criteria guidance from Appendices H & S of NUREG/CR-6850 indicate timing is consistent with loss of habitability timing

- Once damage challenges plant control function, operators will implement MCR abandonment per OP-901-502 Waterford 3 MCR Abandonment Public Meeting 9

Time Determination

  • System Time Window

- MCR abandonment HRA (loss of control and habitability) allows 30 minutes to establish control at remote shutdown panel (LCP-43)

- This time provides at least a 30 minute buffer based on plant specific T/H analysis to feed SGs and prevent core uncovery

- System time window used in HRA is bounding for both loss of control and habitability scenarios Waterford 3 MCR Abandonment Public Meeting 10

Scenario Development

  • Loss of Habitability

- Transient fires

- Main Control Board fires

- Fixed Source fires (control panels)

- Abandonment scenarios developed with and without HVAC operating Waterford 3 MCR Abandonment Public Meeting 11

Scenario Development

  • Loss of Control

- Cable Spreading Room Fires (transients)

- MCR Fires leading to loss of control

  • Based on equipment controlled on key panels which, if lost, could impact key functions
  • Includes transients, fixed sources (panel fires), and MCB fires Waterford 3 MCR Abandonment Public Meeting 12

MCR Human Reliability Analysis

  • Based on the MCR abandonment procedure (draft for NFPA 805)
  • Operator actions relevant to Fire PRA important functions identified
  • Initial MCR actions
  • Recovery Actions
43) - operation of transfer switches in Relay Room

MCR Human Reliability Analysis

  • Initial MCR actions
  • Trip the Reactor
  • Direct field operator to locally trip RCP breakers
  • Secure Charging and Letdown
  • Verify Turbine and Generator tripped
  • Human Failure Events (HFE) developed for actions relevant to FPRA (securing charging/letdown)

Waterford 3 MCR Abandonment Public Meeting 14

MCR Human Reliability Analysis

  • Recovery Action to locally trip RCP breakers

- Prevents RCP Seal LOCA on loss of CCW

- Separate HFE developed and incorporated in MCR abandonment model Waterford 3 MCR Abandonment Public Meeting 15

MCR Human Reliability Analysis

  • Actions to establish control at LCP-43

- PCS Actions per RG 1.205 C.2.4

  • Operation of transfer switches in + 35 Relay Room

- Isolates MCR circuits and aligns control to LCP-43

- 6 sets of switches in 4 Auxiliary panels (62 total switches)

- Only 4 of 6 sets are PRA significant (2 sets assumed failed)

- Credit switch operation recovery from LCP-43 observation

- Each scenario expanded to consider combinations of failed switch operation and resulting equipment impacts Waterford 3 MCR Abandonment Public Meeting 16

MCR Human Reliability Analysis

- PCS Actions per RG 1.205 C.2.4

- Verify controllers transferred properly

  • EFW Flow Control Valves (4)
  • ADVs
  • Pressurizer Level and Pressure
  • Letdown Back Pressure

- Establish control

  • Match switch position to indication
  • Depress Push to Activate switches

- Bounding HFE developed for relevant PRA action to verify Emergency Feedwater Waterford 3 MCR Abandonment Public Meeting 17

Equipment Failures

  • Equipment Failures incorporated in 3 categories

- Impacts resulting from the fire (scenario specific based on fire source ZOI)

- Failed Transfer of LCP-43 Switch

  • Each set of switches mapped to relevant PRA equipment
  • Failed switch operation prevents operation from LCP-43 and modeled as failed in FPRA

- Random Failures from FPRA model Waterford 3 MCR Abandonment Public Meeting 18

CCDP and CLERP

  • Same quantification for Loss of Control as for Habitability based on HRA and fire impacts
  • CCDP and CLERP values quantified for specific scenarios
  • Over 800 scenarios developed based on possible failed transfer switch combinations for each original scenario
  • Post-Transition:

CCDP range from 1.0 to 2.83E-03 and CLERP range from 0.43 to 6.01E-05 Waterford 3 MCR Abandonment Public Meeting 19

VFDRs

  • Identified based on the deterministic separation criteria assuming MCR Abandonment and successful transfer to LCP-43
  • VFDRs applied to post transition plant model using guidance from FAQ 08-0054 to develop compliant plant model
  • Compliant plant model equals the post transition plant model with impact of all VFDRs removed (VFDR cable impact removed from fire area along with associated equipment)

Waterford 3 MCR Abandonment Public Meeting 20

Conclusions

  • The approach used to assess MCR/CSR Fires is performed in accordance with guidelines of NUREG/CR 6850, NEI 04-02 & FAQ 08-0054 Rev 1
  • The approach provides sufficient detail to define available equipment and capture both fire-induced and random failures during abandonment and with control at LCP-43 established
  • Risk and Risk Results within acceptable values Waterford 3 MCR Abandonment Public Meeting 21

Questions Waterford 3 MCR Abandonment Public Meeting 22

Remote Shutdown Panel (LCP-43)

NRC Public Meeting 23

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