ML15342A101

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TORMIS Computer Code Methodology Public Meeting Slides
ML15342A101
Person / Time
Site: Byron  Constellation icon.png
Issue date: 12/09/2015
From:
Exelon Generation Co
To: Joel Wiebe
Plant Licensing Branch III
Joel Wiebe, NRR/DORL
References
Download: ML15342A101 (11)
v • d • e


Text

Byron Station TORMIS Computer Code Methodology License Amendment Request December 9, 2015

Agenda

  • Introductions and Opening Remarks
  • Meeting Purpose
  • TORMIS Computer Code Methodology use and preliminary results
  • License Amendment Request

- Overview

- Proposed Updated Final Safety Analysis Report (UFSAR) Changes

  • Summary and Conclusions 1

Meeting Purpose

  • Outline the key attributes of the proposed License Amendment Request:

- Utilize the TORMIS computer code methodology regarding tornado missile protection

  • Engage the NRC in an open and transparent dialog regarding the proposed approach to identify technical and regulatory areas of concern that warrant additional discussion to ensure they are adequately addressed in the License Amendment Request
  • Provide clarification to any NRC questions 2

TORMIS Computer Code Methodology

  • Exelon is proposing to use the TORMIS methodology to assess tornado missile strike probability for equipment important to safety that is currently not protected from tornado missiles at Byron Station

- TORMIS uses a Monte Carlo simulation method that simulates tornado strikes on a nuclear station

  • The TORMIS analysis is performed in accordance with the requirements of:

- NRC Safety Evaluation Report (SER) (November 1983) for TORMIS; and

- RIS 2008-14, Use of TORMIS Computer Code for Assessment of Tornado Missile Protection (June 2008)

  • Approximately 136 individual targets were evaluated:

- Over 27.7 billion TORMIS tornado missile simulations were performed

- The requirements for missile strike probability discussed in the TORMIS SER have been met; and the issues identified in RIS 2008-14 have been addressed 3

License Amendment Request - Overview

  • NRC approval is requested for use of the TORMIS computer code methodology
  • Utilization of the TORMIS computer code methodology has no impact on the Technical Specifications (TS); therefore, this License Amendment Request contains no TS changes 4

License Amendment Request - Overview (contd)

  • The complete TORMIS analysis consists of the following five volumes):

- Volume I TORMIS Results

- Contains the analysis results and TORMIS control data inputs

- Volume II Tornado Hazard

- Develops the tornado hazard data inputs to TORMIS

- Volume III Plant Model and Missile Characteristics

- Contains the plant model and missile characteristics data

- Volume IV Computer Code Verification

- Includes the TORMIS verification documentation

- Volume V Finite Element Analysis

- Develops the critical missile velocities that produce crimping of the:

  • Diesel AFP exhaust pipe cover plates

License Amendment Request - Overview (contd)

  • Exelon intends on submitting only Volume I of the TORMIS analysis, excluding the input and output files. Volume I includes the following topics:

- Calculation Methodology

- Methodology Limitations and Conservatisms

- Major Assumptions and Engineering Judgments

- Calculation Inputs

- Details of the Calculation

- Acceptance Criteria

- Conclusion

  • A complete discussion on how the Byron Station TORMIS analysis complies with the requirements of the NRC TORMIS SER and RIS 2008-14 is presented in the TORMIS analysis, Volume I, Section 9, Acceptance Criteria
  • The TORMIS analysis results will now allow certain components/equipment to be credited in various design analysis that previously were not credited due to lack of tornado missile protection 6

License Amendment Request - Overview (contd)

  • The availability of this equipment may now be used as input changes to existing design analysis methodologies, utilizing the normal licensee design change processes, to yield more favorable analytical results/consequences; for example:

- Operability Evaluation 13-007, Ultimate Heat Sink Capability with Loss of Service Water Cooling Tower Fans, is currently in place which demonstrates operability of the UHS assuming no Essential Service Water Cooling Tower (SXCT) fans are available for post-tornado Reactor Coolant System (RCS) cooldown

- The TORMIS analysis results demonstrate that either 2 or 3 SXCT fans survive a tornado strike on the facility

- Crediting SXCT fans in the existing the UHS post-tornado cooldown analysis will yield favorable results and allow closure of the associated Operability Evaluation 7

License Amendment Request - UFSAR Changes

  • The UFSAR will be revised to reflect use of the TORMIS methodology. The following USFSAR section will be revised as appropriate:

- Section 3.5, Missile Protection 8

Summary and Conclusions

  • NRC approval of the TORMIS computer code methodology will:

- Resolve the current Byron Station tornado missile protection deficiencies and provide an acceptable tool to resolve future tornado protection issues should they arise

- Demonstrate the availability of components/equipment which may be used as input changes to existing design analysis methodologies, utilizing the normal licensee design change processes, to yield favorable results/consequences; e.g., the UHS post-tornado cooldown design basis analysis

- Enable resolution and closeout of open Operability Evaluations e.g., Operability Evaluation 13-007, Ultimate Heat Sink Capability with Loss of Service Water Cooling Tower Fans 9

Questions ?

10

Byron Station TORMIS Computer Code Methodology License Amendment Request December 9, 2015

Agenda

  • Introductions and Opening Remarks
  • Meeting Purpose
  • TORMIS Computer Code Methodology use and preliminary results
  • License Amendment Request

- Overview

- Proposed Updated Final Safety Analysis Report (UFSAR) Changes

  • Summary and Conclusions 1

Meeting Purpose

  • Outline the key attributes of the proposed License Amendment Request:

- Utilize the TORMIS computer code methodology regarding tornado missile protection

  • Engage the NRC in an open and transparent dialog regarding the proposed approach to identify technical and regulatory areas of concern that warrant additional discussion to ensure they are adequately addressed in the License Amendment Request
  • Provide clarification to any NRC questions 2

TORMIS Computer Code Methodology

  • Exelon is proposing to use the TORMIS methodology to assess tornado missile strike probability for equipment important to safety that is currently not protected from tornado missiles at Byron Station

- TORMIS uses a Monte Carlo simulation method that simulates tornado strikes on a nuclear station

  • The TORMIS analysis is performed in accordance with the requirements of:

- NRC Safety Evaluation Report (SER) (November 1983) for TORMIS; and

- RIS 2008-14, Use of TORMIS Computer Code for Assessment of Tornado Missile Protection (June 2008)

  • Approximately 136 individual targets were evaluated:

- Over 27.7 billion TORMIS tornado missile simulations were performed

- The requirements for missile strike probability discussed in the TORMIS SER have been met; and the issues identified in RIS 2008-14 have been addressed 3

License Amendment Request - Overview

  • NRC approval is requested for use of the TORMIS computer code methodology
  • Utilization of the TORMIS computer code methodology has no impact on the Technical Specifications (TS); therefore, this License Amendment Request contains no TS changes 4

License Amendment Request - Overview (contd)

  • The complete TORMIS analysis consists of the following five volumes):

- Volume I TORMIS Results

- Contains the analysis results and TORMIS control data inputs

- Volume II Tornado Hazard

- Develops the tornado hazard data inputs to TORMIS

- Volume III Plant Model and Missile Characteristics

- Contains the plant model and missile characteristics data

- Volume IV Computer Code Verification

- Includes the TORMIS verification documentation

- Volume V Finite Element Analysis

- Develops the critical missile velocities that produce crimping of the:

  • Diesel AFP exhaust pipe cover plates

License Amendment Request - Overview (contd)

  • Exelon intends on submitting only Volume I of the TORMIS analysis, excluding the input and output files. Volume I includes the following topics:

- Calculation Methodology

- Methodology Limitations and Conservatisms

- Major Assumptions and Engineering Judgments

- Calculation Inputs

- Details of the Calculation

- Acceptance Criteria

- Conclusion

  • A complete discussion on how the Byron Station TORMIS analysis complies with the requirements of the NRC TORMIS SER and RIS 2008-14 is presented in the TORMIS analysis, Volume I, Section 9, Acceptance Criteria
  • The TORMIS analysis results will now allow certain components/equipment to be credited in various design analysis that previously were not credited due to lack of tornado missile protection 6

License Amendment Request - Overview (contd)

  • The availability of this equipment may now be used as input changes to existing design analysis methodologies, utilizing the normal licensee design change processes, to yield more favorable analytical results/consequences; for example:

- Operability Evaluation 13-007, Ultimate Heat Sink Capability with Loss of Service Water Cooling Tower Fans, is currently in place which demonstrates operability of the UHS assuming no Essential Service Water Cooling Tower (SXCT) fans are available for post-tornado Reactor Coolant System (RCS) cooldown

- The TORMIS analysis results demonstrate that either 2 or 3 SXCT fans survive a tornado strike on the facility

- Crediting SXCT fans in the existing the UHS post-tornado cooldown analysis will yield favorable results and allow closure of the associated Operability Evaluation 7

License Amendment Request - UFSAR Changes

  • The UFSAR will be revised to reflect use of the TORMIS methodology. The following USFSAR section will be revised as appropriate:

- Section 3.5, Missile Protection 8

Summary and Conclusions

  • NRC approval of the TORMIS computer code methodology will:

- Resolve the current Byron Station tornado missile protection deficiencies and provide an acceptable tool to resolve future tornado protection issues should they arise

- Demonstrate the availability of components/equipment which may be used as input changes to existing design analysis methodologies, utilizing the normal licensee design change processes, to yield favorable results/consequences; e.g., the UHS post-tornado cooldown design basis analysis

- Enable resolution and closeout of open Operability Evaluations e.g., Operability Evaluation 13-007, Ultimate Heat Sink Capability with Loss of Service Water Cooling Tower Fans 9

Questions ?

10

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