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{{#Wiki_filter:Spent Fuel Management :
{{#Wiki_filter:Spent Fuel Management :
Safety and Efficiency Improvements Through Technology and Performance Margins
Safety and Efficiency Improvements Through Technology and Performance Margins


NEI-NRC Public Meeting
NEI-NRC Public Meeting
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August 19, 2024 Nuclear Energy: National Importance Inflation Reduction Act (IRA)
August 19, 2024 Nuclear Energy: National Importance Inflation Reduction Act (IRA)
* Congress sent a clear signal that nuclear is essential to the transition to a clean energy economy
* Congress sent a clear signal that nuclear is essential to the transition to a clean energy economy
* Backbone of stable electric grid
* Backbone of stable electric grid
* Meeting growing demand for more clean energy
* Meeting growing demand for more clean energy


ADVANCE Act
ADVANCE Act
* Maintains U.S. global leadership
* Maintains U.S. global leadership
* Enables testing, demonstration and deployment of accident tolerant fuels and advanced nuclear reactor fuel concepts
* Enables testing, demonstration and deployment of accident tolerant fuels and advanced nuclear reactor fuel concepts
* Supports modernization of licensing and oversight of operating reactors
* Supports modernization of licensing and oversight of operating reactors


                                                                                                                                                      ©2024 Nuclear Energy Institute       2 PIRT Implementation is a Key Opportunity to Modernize
©2024 Nuclear Energy Institute 2 PIRT Implementation is a Key Opportunity to Modernize


Enables efficiencies necessary for dry storage capabilities to keep pace with nuclear growth
Enables efficiencies necessary for dry storage capabilities to keep pace with nuclear growth
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Embodies NRC Principles of Good Regulation
Embodies NRC Principles of Good Regulation


                                                                                ©2024 Nuclear Energy Institute       3 The Opportunity
©2024 Nuclear Energy Institute 3 The Opportunity


Advanced fuels may increase source term and decay heat Load canisters more efficiently with shielding while reducing dose, handling and improving spent fuel pool management Ultra conservative assumptions reduce safety and efficiency Actionable definitions of gross rupture, performance-                                                                                                                                                                                                                             based peak clad temperature and thermal margin enable efficiencies and flexibility in analysis and operations-                                                                                                                                                                           enhance safety and efficiency Use of performance-                                                                                                                                                                                                                         based results provides a good example of how NRC can use risk insights and allow us to live up to our collective safety imperative
Advanced fuels may increase source term and decay heat Load canisters more efficiently with shielding while reducing dose, handling and improving spent fuel pool management Ultra conservative assumptions reduce safety and efficiency Actionable definitions of gross rupture, performance-based peak clad temperature and thermal margin enable efficiencies and flexibility in analysis and operations-enhance safety and efficiency Use of performance-based results provides a good example of how NRC can use risk insights and allow us to live up to our collective safety imperative


                                                                                                                            ©2024 Nuclear Energy Institute       4 Spent Fuel PIRTs -
©2024 Nuclear Energy Institute 4 Spent Fuel PIRTs -
Pathway to Implementation NRC Public Meeting
Pathway to Implementation NRC Public Meeting


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===Background===
===Background===
DEFINING SPENT FUEL PERFORMANCE MARGINS by NEI Spent Fuel Margins White Paper Development Task Force November 8, 2019


DEFINING SPENT  FUEL  PERFORMANCE  MARGINS by NEI Spent Fuel Margins White Paper Development Task Force November 8, 2019
Recommendations IV-1-5 Goals: Update thermal Most efficient regulatory modeling methods for implementation vehicle improved focus on safety pending further discussions:
including a revised thermal EPRI Topical Report and/or modeling metric and a NRC Standard Review Plan graded approach for thermal update modeling to expand margins and operational flexibilities with increased safety and cost savings


Recommendations IV-1-5 Goals: Update thermal                                                    Most efficient regulatory modeling methods for                                                    implementation vehicle improved focus on safety                                                pending further discussions:
6 © 2024 Electric Power Research Institute, Inc. All rights reserved.
including a revised thermal                                                EPRI Topical  Report  and/or modeling metric and a                                                      NRC Standard Review  Plan graded approach for thermal                                                update modeling to expand margins and operational flexibilities with  increased safety  and cost savings
 
6                                     © 2024 Electric Power Research Institute, Inc. All rights reserved.


===Background===
===Background===
Fuel Performance PIRT
Fuel Performance PIRT
      -                                                                             The onset of fuel failure is not abrupt, but rather a continuum no cliff-edge effect is associated with the current NRC recommended 400 °C limit (ISG-11 Rev. 3)
- The onset of fuel failure is not abrupt, but rather a continuum no cliff-edge effect is associated with the current NRC recommended 400 °C limit (ISG-11 Rev. 3)


Decay Heat PIRT
Decay Heat PIRT
      -                                                                             Regulatory guidance (RG. 3.54 Rev. 1) significantly overestimates decay heat over wide range of fuel burnups.
- Regulatory guidance (RG. 3.54 Rev. 1) significantly overestimates decay heat over wide range of fuel burnups.


Thermal PIRT
Thermal PIRT
      -                                                                               Excess conservatism in thermal calculations leads to negative impact on worker doseand fuel performance
- Excess conservatism in thermal calculations leads to negative impact on worker doseand fuel performance


7                                                         © 2024 Electric Power Research Institute, Inc. All rights reserved.
7 © 2024 Electric Power Research Institute, Inc. All rights reserved.


===Background===
===Background===
Gross Rupture PIRT
Gross Rupture PIRT
          -                                                                       RCS chemistry records from operation may be used to establish if fuel cladding gross rupture   failure occurred to determine storage requirements Alternate Fuel Performance Metrics PIRT
- RCS chemistry records from operation may be used to establish if fuel cladding gross rupture failure occurred to determine storage requirements Alternate Fuel Performance Metrics PIRT
          -                                                                       Increasing PCT limit to 450oC or 500oC   are potentially acceptable metrics to pursue
- Increasing PCT limit to 450oC or 500oC are potentially acceptable metrics to pursue


Other metrics considered but not recommended: hoop stress, average cladding temperature
Other metrics considered but not recommended: hoop stress, average cladding temperature


Excessive Layers of Conser vatisms                                                         More doseo theorkers Lessegulatory efficiency
Excessive Layers of Conser vatisms More doseo theorkers Lessegulatory efficiency


8                                                                                     © 2024 Electric Power Research Institute, Inc. All rights reserved.
8 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Objectives of PIRTs Implementation
Objectives of PIRTs Implementation


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PCT and Graded Approach
PCT and Graded Approach


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9 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Gross Rupture
Gross Rupture


10                                                             © 2024 Electric Power Research Institute, Inc. All rights reserved.
10 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Gross Rupture Topical Report -                                                                   Background
Gross Rupture Topical Report - Background


Unclear guidance in NUREG-2215
Unclear guidance in NUREG-2215
                -                                                         p xxviii:                 Gross Breach. A breach in the spent fuel cladding that is larger than either a pinhole leak or a hairline crack and allows the release of particulate matter from the spent fuel rod.                                                                                                         Current definition of gross
- p xxviii: Gross Breach. A breach in the spent fuel cladding that is larger than either a pinhole leak or a hairline crack and allows the release of particulate matter from the spent fuel rod. Current definition of gross
                -                                                       p8-                                                                                         35 SFAs with any of the following characteristics   are rupture non-actionable expected to be classified as damaged:                                                                                 due to:
- p8-35 SFAs with any of the following characteristics are rupture non-actionable expected to be classified as damaged: due to:
Reactor operating records or fuel classification records
Reactor operating records or fuel classification records
* Lack of criteria indicate                                                                         that the SFA contains fuel rods with gross regarding use of reactor breaches.                                                                                                                 operating records
* Lack of criteria indicate that the SFA contains fuel rods with gross regarding use of reactor breaches. operating records
                -                                                       p8-                                                                                             36: gross breaches should be considered to be                     any
- p8-36: gross breaches should be considered to be any
* Demonstration that cladding breach greater than 1 mm (0.04 in.) .                                                                             1mm criteria is met And in NUREG-2216                                                                                         difficult to achieve
* Demonstration that cladding breach greater than 1 mm (0.04 in.). 1mm criteria is met And in NUREG-2216 difficult to achieve
                -                                                               p7-                                                                                             49: The staff considers that adequate reactor operating records that identify only gaseous or volatile decay products (no heavy   metals) in the reactor coolant system are acceptable evidence that cladding breaches are no larger than a pinhole leak or hairline crack.
- p7-49: The staff considers that adequate reactor operating records that identify only gaseous or volatile decay products (no heavy metals) in the reactor coolant system are acceptable evidence that cladding breaches are no larger than a pinhole leak or hairline crack.


11                                                                           © 2024 Electric Power Research Institute, Inc. All rights reserved.
11 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Gross Rupture Topical Report
Gross Rupture Topical Report


Scope
Scope
        -                                                                               Implement new definition to use chemistry records in lieu of fuel inspections (e.g. sipping) to demonstrate cladding integrity Safety benefits of New Gross Rupture Definition
- Implement new definition to use chemistry records in lieu of fuel inspections (e.g. sipping) to demonstrate cladding integrity Safety benefits of New Gross Rupture Definition
        -                                                                           Better comply with ALARA principles Reduce dose to the workers
- Better comply with ALARA principles Reduce dose to the workers
        -                                                                         Reduce risk Avoid unnecessary handling by minimizing need for sipping campaigns and pool-side exams
- Reduce risk Avoid unnecessary handling by minimizing need for sipping campaigns and pool-side exams


New definition of gross rupture                                                       FSARs and CoC do not preclude to clarify NRC guidance and allow                                                     the use of the new gross stakeholders to use consistent                                                       rupture definition and actionable metrics Clarity Efficiency Reliability
New definition of gross rupture FSARs and CoC do not preclude to clarify NRC guidance and allow the use of the new gross stakeholders to use consistent rupture definition and actionable metrics Clarity Efficiency Reliability


12                                                                   © 2024 Electric Power Research Institute, Inc. All rights reserved.
12 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Gross Rupture Topical Report
Gross Rupture Topical Report


Topical report
Topical report
              -                                                                                 Technical basis for new definition of gross rupture based Input from Gross Rupture PIRT Guidance regarding:
- Technical basis for new definition of gross rupture based Input from Gross Rupture PIRT Guidance regarding:
                                -                                                                                     Applicability criteria (e.g., quality of chemistry records)
- Applicability criteria (e.g., quality of chemistry records)
                                -                                                                                     Key parameters to survey (e.g., increase in fuel products concentration during cycle and vs.
- Key parameters to survey (e.g., increase in fuel products concentration during cycle and vs.
previous cycle)
previous cycle)
Impacts on SRP and other NRC guidance documents
Impacts on SRP and other NRC guidance documents
              -                                                                                 Generic Directly referenceable   by licensees Expected         Industry Actions                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           Expected       NRC Actions
- Generic Directly referenceable by licensees Expected Industry Actions Expected NRC Actions


CoC amendments may not needed                                                                                                                                                 Review / approve TR (SER)
CoC amendments may not needed Review / approve TR (SER)
Most CoCs already have wording that allows using                                                                                                                     Revise guidance (SRP storage and transportation) the new definition                                                                                                                         industry does not need to wait to start Underlying documents for fuel qualification may                                                                                                                                     implementing once SER is issued need to be changed + criteria used in site                                                                                                                                             Revise inspection criteria procedures
Most CoCs already have wording that allows using Revise guidance (SRP storage and transportation) the new definition industry does not need to wait to start Underlying documents for fuel qualification may implementing once SER is issued need to be changed + criteria used in site Revise inspection criteria procedures


13                                                                                                                     © 2024 Electric Power Research Institute, Inc. All rights reserved.
13 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Benefits for the NRC
Benefits for the NRC


Clarification of NRC guidance                                                                                   Reduce risk inconsistencies                                                                                                       -                                                                             Eliminate unnecessary fuel moves
Clarification of NRC guidance Reduce risk inconsistencies - Eliminate unnecessary fuel moves
          -                                                                               Definition of gross rupture currently non-                                       Better compliance with ALARA actionable by industry                                                                                         principles
- Definition of gross rupture currently non-Better compliance with ALARA actionable by industry principles
          -                                                                             Inconsistency between storage and       -                                                                               Eliminate unnecessary dose-consuming transport SRPs                                                                                                       activities
- Inconsistency between storage and - Eliminate unnecessary dose-consuming transport SRPs activities
          -                                                                             Comply with principles of good regulation Generic implementation of criteria                                                                               Reduce undue burdens change for broad adoption                                                                                             -                                                                               Reduce number of damage fuel containers
- Comply with principles of good regulation Generic implementation of criteria Reduce undue burdens change for broad adoption - Reduce number of damage fuel containers


          -                                                                                   Reduce regulatory burden and review Recommendations to update guidance
- Reduce regulatory burden and review Recommendations to update guidance
          -                                                                               RCS chemistry applicability criteria
- RCS chemistry applicability criteria
          -                                                                               Technical justification of key parameters
- Technical justification of key parameters


14                                                                                         © 2024 Electric Power Research Institute, Inc. All rights reserved.
14 © 2024 Electric Power Research Institute, Inc. All rights reserved.
PCT and Graded Approach
PCT and Graded Approach


15                                             © 2024 Electric Power Research Institute, Inc. All rights reserved.
15 © 2024 Electric Power Research Institute, Inc. All rights reserved.
PCT and Graded Approach Topical Report
PCT and Graded Approach Topical Report


Scope
Scope
                    -                                                                                 Implement increased PCT limit of 450oC Include a graded approach for storage and transportation safety analyses Safety benefits
- Implement increased PCT limit of 450oC Include a graded approach for storage and transportation safety analyses Safety benefits


                    -                                                                                   Shorter loading times             Compliance with ALARA principles, such as:
- Shorter loading times Compliance with ALARA principles, such as:
                    -                                                                               Fewer canisters loaded
- Fewer canisters loaded
* Public: Less transportation events (precursor)
* Public: Less transportation events (precursor)
                    -                                                                                 Regulation efficiency increased
- Regulation efficiency increased
* Wo   r   ke   r s   : Increased shielding, Fewer/shorter
* Wo r ke r s : Increased shielding, Fewer/shorter
                    -                                                                                 Risk-informed analyses leveraged               loadings Operational Flexibility
- Risk-informed analyses leveraged loadings Operational Flexibility


                    -                                                                               More time for certain operations,
- More time for certain operations,
                    -                                                                             Eliminate supplemental cooling system,
- Eliminate supplemental cooling system,
                    -                                                                                   Add shielding
- Add shielding


16                                                                                                     © 2024 Electric Power Research Institute, Inc. All rights reserved.
16 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Peak Cladding Temperature -                         Graded Approach
Peak Cladding Temperature - Graded Approach


Performance Margin -                         Fuel rod has additional capacity to go to higher temperature without failure Methods Margin -                                                                   Conservatisms in the modeling Graded approach would require increased analytical rigor to tighten uncertainties as you approach 450°                                                                                                                                                       C limit PCT (°                                         C)Uncertainties reduction through analytical rigor
Performance Margin - Fuel rod has additional capacity to go to higher temperature without failure Methods Margin - Conservatisms in the modeling Graded approach would require increased analytical rigor to tighten uncertainties as you approach 450° C limit PCT (° C)Uncertainties reduction through analytical rigor


450
450
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400
400


Analytical Rigor Objective: Develop a risk-informed and graded approach and avoid making licensing more complicated with additional analyses where more margin exists
Analytical Rigor Objective: Develop a risk-informed and graded approach and avoid making licensing more complicated with additional analyses where more margin exists


17                                                                   © 2024 Electric Power Research Institute, Inc. All rights reserved.
17 © 2024 Electric Power Research Institute, Inc. All rights reserved.
NAC-                                                                                                                                                                                                                                                                                                         STC High-                                                                                                                                                                                                                                                                                                                                                                                                                                 Burnup Fuel Amendment
NAC-STC High-Burnup Fuel Amendment


Excessive analytical level of detail (academic exercise) required for a licensed system resulting in no impact to the safety of the design NAC initially provided thermal analysis, based on the existing NRC approved thermal methods/models for the NAC-                                                   STC to support reasonable assurance the cask would perform as required
Excessive analytical level of detail (academic exercise) required for a licensed system resulting in no impact to the safety of the design NAC initially provided thermal analysis, based on the existing NRC approved thermal methods/models for the NAC-STC to support reasonable assurance the cask would perform as required
* No basket design changes
* No basket design changes
* Change in individual fuel thermal loads and loading pattern NRCs thermal reviewers suggested that NAC needed to develop and qualify new, best estimate models for assessing HBU fuel performance, and included directions to use NUREG     -
* Change in individual fuel thermal loads and loading pattern NRCs thermal reviewers suggested that NAC needed to develop and qualify new, best estimate models for assessing HBU fuel performance, and included directions to use NUREG -
2152 (authored by the thermal reviewers) for the development and qualification of thermal models
2152 (authored by the thermal reviewers) for the development and qualification of thermal models


                                                                                                                                                                                                            ©2019 Nuclear Energy Institute       18
©2019 Nuclear Energy Institute 18


18 Why the industry believes the PIRT work and applying Risk Informed criteria is Valuable
18 Why the industry believes the PIRT work and applying Risk Informed criteria is Valuable


In 2019-                                                                                                                                                                                                                           20, NAC submitted an amendment for a content change using the license basis MOE.
In 2019-20, NAC submitted an amendment for a content change using the license basis MOE.
Ultimately, regulatory direction, via RAI, was for NAC to develop 3 brand new discrete thermal models to support a methodical discretization allowing performance of a Grid Convergence Index (GCI).
Ultimately, regulatory direction, via RAI, was for NAC to develop 3 brand new discrete thermal models to support a methodical discretization allowing performance of a Grid Convergence Index (GCI).
Why?   Because NACs reported PCT was within 25C of the 400C limit If the PCT limit is really a safety limit and Risk Informed Regulation determines that reporting temperatures within some percent triggers the need to address uncertainties (i.e. GCI performance) then this should be clear to the licensee through regulation and not invoked through the RAI process.
Why? Because NACs reported PCT was within 25C of the 400C limit If the PCT limit is really a safety limit and Risk Informed Regulation determines that reporting temperatures within some percent triggers the need to address uncertainties (i.e. GCI performance) then this should be clear to the licensee through regulation and not invoked through the RAI process.
After a long RAI process ultimately involving the GCI methodology, the associated costs to the project and delays in licensing resulted in a little over one degree F lower PCT for the three additional models.
After a long RAI process ultimately involving the GCI methodology, the associated costs to the project and delays in licensing resulted in a little over one degree F lower PCT for the three additional models.


                                                                                                                        ©2019 Nuclear Energy Institute       19
©2019 Nuclear Energy Institute 19


19 NAC-                                                                                                                                                                                                                                                                                                         STC High-                                                                                                                                                                                                                                                                                                                                                                                                                                 Burnup Fuel Amendment (Contd)
19 NAC-STC High-Burnup Fuel Amendment (Contd)


NAC was had no choice but to develop 3 brand new discrete thermal models (utilizing 900K, 3000K, 7200K elements including mesh refinement in axial direction)   to support a methodical discretization allowing development of a Grid Convergence Index (GCI)
NAC was had no choice but to develop 3 brand new discrete thermal models (utilizing 900K, 3000K, 7200K elements including mesh refinement in axial direction) to support a methodical discretization allowing development of a Grid Convergence Index (GCI)


Model ID                                                                                                                                                                                                                                                                                                                                                                 Number of PCT (F)                                                                                                                                                                                                                                                                                                                                                                                                                                                                             T (F)
Model ID Number of PCT (F) T (F)
Hexahedral Elements
Hexahedral Elements


Model No. 1                                                                                                                                                                                                                                                                                                                                               7,168,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 633                                                                                                                                                                 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                                                                                                                                                                                                                                                                          632                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           151 Model No. 3                                                                                                                                                                                                                                                                                                                                                                             896,000                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                               629                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                           151 Base Model                                                                                                                                                                                                                                                                                                                                                                                                             95,672                                                                                                                                                                                                                                                               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Model No. 1 7,168,000 633 151 Model No. 2 3,024,000 632 151 Model No. 3 896,000 629 151 Base Model 95,672 638 153


Performance of this work required over 2000 additional man -hours, demonstrated no significant change in PCT and resulted in no changes to the design or loading configuration(s)
Performance of this work required over 2000 additional man -hours, demonstrated no significant change in PCT and resulted in no changes to the design or loading configuration(s)
Proximity (~25F) of our calculated PCT, with no credit given for conservatisms in the model, to the PCT limit was used as the basis for requiring the GCI be performed
Proximity (~25F) of our calculated PCT, with no credit given for conservatisms in the model, to the PCT limit was used as the basis for requiring the GCI be performed


                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    ©2019 Nuclear Energy Institute       20
©2019 Nuclear Energy Institute 20


20 Benefits for the NRC
20 Benefits for the NRC


Improved clarity, efficiency, and reliability
Improved clarity, efficiency, and reliability
        -                                                                             Graded approach to apply resources more efficiently and effectively Generic implementation of criteria change for broad adoption
- Graded approach to apply resources more efficiently and effectively Generic implementation of criteria change for broad adoption
        -                                                                                 Reduce regulatory burden and review Recommendations to implement updated metrics into future NRC guidance
- Reduce regulatory burden and review Recommendations to implement updated metrics into future NRC guidance
        -                                                                             Clarify limits and uncertainties
- Clarify limits and uncertainties
        -                                                                               Reflect better understanding of thermal margins into NRC guidance Risk-                                                                                                                 informed application of operational margin to be leveraged to:
- Reflect better understanding of thermal margins into NRC guidance Risk-informed application of operational margin to be leveraged to:
        -                                                                                 Decrease dose to   the workers
- Decrease dose to the workers
        -                                                                             Decrease operational risks by eliminating unnecessary actions
- Decrease operational risks by eliminating unnecessary actions


21                                                                     © 2024 Electric Power Research Institute, Inc. All rights reserved.
21 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Implementation
Implementation


22                                                         © 2024 Electric Power Research Institute, Inc. All rights reserved.
22 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Potential Pathway
Potential Pathway


Fee waiver           Gross Rupture TR         SER Next:             request               NRC Review                                                 SRP / Guidance Gross Rupture                                     Plant Procedure                       Up d ates
Fee waiver Gross Rupture TR SER Next: request NRC Review SRP / Guidance Gross Rupture Plant Procedure Up d ates


TR                                             Up d ates
TR Up d ates


Future:                           PCT TR
Future: PCT TR


Fee         Case Study                               SER waiver       Gap Data           PCT TR NRC Review request Vendor CoC Amendment NRC Review Amendments Plant document updates
Fee Case Study SER waiver Gap Data PCT TR NRC Review request Vendor CoC Amendment NRC Review Amendments Plant document updates


23                                               © 2024 Electric Power Research Institute, Inc. All rights reserved.
23 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Timeline
Timeline


September 2024: Fee Waiver Request Letter for If fee waiver for                   Gross Rupture TR GR approved Q1 2025: Gross Rupture TR               Duration NRC review?
September 2024: Fee Waiver Request Letter for If fee waiver for Gross Rupture TR GR approved Q1 2025: Gross Rupture TR Duration NRC review?


TBD: Fee Waiver Request Letter for PCT and Graded Approach TRIf fee waiver
TBD: Fee Waiver Request Letter for PCT and Graded Approach TRIf fee waiver


for PCT approved TBD: PCT and Graded Approach TR
for PCT approved TBD: PCT and Graded Approach TR


24                                                         © 2024 Electric Power Research Institute, Inc. All rights reserved.
24 © 2024 Electric Power Research Institute, Inc. All rights reserved.
Summary
Summary


        -                                                                           The 5 PIRTs provide strong basis to improve regulatory efficiency, clarity and reliability for all stakeholders.
- The 5 PIRTs provide strong basis to improve regulatory efficiency, clarity and reliability for all stakeholders.
        -                                                                                 Objective is to   improve safety and efficiency:
- Objective is to improve safety and efficiency:
Decrease dose to   the workers Reduce accident precursor events (transportation)
Decrease dose to the workers Reduce accident precursor events (transportation)
Improve realism to optimize safety and efficiency
Improve realism to optimize safety and efficiency
        -                                                                             Near term: Gross Rupture TR Fee waiver request Directly applicable recommendations to improve regulatory guidance
- Near term: Gross Rupture TR Fee waiver request Directly applicable recommendations to improve regulatory guidance
        -                                                                               Longer term: PCT and Graded Approach TR Increased PCT limit Graded approach Operational impacts
- Longer term: PCT and Graded Approach TR Increased PCT limit Graded approach Operational impacts


25                                                                           © 2024 Electric Power Research Institute, Inc. All rights reserved.
25 © 2024 Electric Power Research Institute, Inc. All rights reserved.
TOGETHERSHAPING THE FUTURE OF ENERGY                                                                          
TOGETHERSHAPING THE FUTURE OF ENERGY  


www.epri.com       © 2024 Electric Power Research Institute, Inc. All rights reserved.
www.epri.com © 2024 Electric Power Research Institute, Inc. All rights reserved.
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Latest revision as of 07:26, 4 October 2024

NEI - Spent Fuel Management: Safety and Efficiency Improvements Through Technology and Performance Margins - NRC PIRTs Public Meeting Rev. 8.15.2024 Final
ML24229A001
Person / Time
Site: Nuclear Energy Institute
Issue date: 08/19/2024
From: Richter M
Nuclear Energy Institute
To:
Office of Nuclear Material Safety and Safeguards
Daneira Melendez
References
Download: ML24229A001 (26)
v • d • e


Text

Spent Fuel Management :

Safety and Efficiency Improvements Through Technology and Performance Margins

NEI-NRC Public Meeting

Mark Richter Technical Advisor Nuclear Energy Institute

August 19, 2024 Nuclear Energy: National Importance Inflation Reduction Act (IRA)

  • Congress sent a clear signal that nuclear is essential to the transition to a clean energy economy
  • Backbone of stable electric grid
  • Meeting growing demand for more clean energy

ADVANCE Act

  • Maintains U.S. global leadership
  • Enables testing, demonstration and deployment of accident tolerant fuels and advanced nuclear reactor fuel concepts
  • Supports modernization of licensing and oversight of operating reactors

©2024 Nuclear Energy Institute 2 PIRT Implementation is a Key Opportunity to Modernize

Enables efficiencies necessary for dry storage capabilities to keep pace with nuclear growth

Consistent with other notable improvements (e.g. license renewal)

Embodies NRC Principles of Good Regulation

©2024 Nuclear Energy Institute 3 The Opportunity

Advanced fuels may increase source term and decay heat Load canisters more efficiently with shielding while reducing dose, handling and improving spent fuel pool management Ultra conservative assumptions reduce safety and efficiency Actionable definitions of gross rupture, performance-based peak clad temperature and thermal margin enable efficiencies and flexibility in analysis and operations-enhance safety and efficiency Use of performance-based results provides a good example of how NRC can use risk insights and allow us to live up to our collective safety imperative

©2024 Nuclear Energy Institute 4 Spent Fuel PIRTs -

Pathway to Implementation NRC Public Meeting

Keith Waldrop Senior Technical Leader

August 19, 2024

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Background

DEFINING SPENT FUEL PERFORMANCE MARGINS by NEI Spent Fuel Margins White Paper Development Task Force November 8, 2019

Recommendations IV-1-5 Goals: Update thermal Most efficient regulatory modeling methods for implementation vehicle improved focus on safety pending further discussions:

including a revised thermal EPRI Topical Report and/or modeling metric and a NRC Standard Review Plan graded approach for thermal update modeling to expand margins and operational flexibilities with increased safety and cost savings

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Background

Fuel Performance PIRT

- The onset of fuel failure is not abrupt, but rather a continuum no cliff-edge effect is associated with the current NRC recommended 400 °C limit (ISG-11 Rev. 3)

Decay Heat PIRT

- Regulatory guidance (RG. 3.54 Rev. 1) significantly overestimates decay heat over wide range of fuel burnups.

Thermal PIRT

- Excess conservatism in thermal calculations leads to negative impact on worker doseand fuel performance

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Background

Gross Rupture PIRT

- RCS chemistry records from operation may be used to establish if fuel cladding gross rupture failure occurred to determine storage requirements Alternate Fuel Performance Metrics PIRT

- Increasing PCT limit to 450oC or 500oC are potentially acceptable metrics to pursue

Other metrics considered but not recommended: hoop stress, average cladding temperature

Excessive Layers of Conser vatisms More doseo theorkers Lessegulatory efficiency

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Objectives of PIRTs Implementation

Define pathways to leverage the benefits of all the PIRTs for

Gross Rupture

PCT and Graded Approach

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Gross Rupture

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Gross Rupture Topical Report - Background

Unclear guidance in NUREG-2215

- p xxviii: Gross Breach. A breach in the spent fuel cladding that is larger than either a pinhole leak or a hairline crack and allows the release of particulate matter from the spent fuel rod. Current definition of gross

- p8-35 SFAs with any of the following characteristics are rupture non-actionable expected to be classified as damaged: due to:

Reactor operating records or fuel classification records

  • Lack of criteria indicate that the SFA contains fuel rods with gross regarding use of reactor breaches. operating records

- p8-36: gross breaches should be considered to be any

  • Demonstration that cladding breach greater than 1 mm (0.04 in.). 1mm criteria is met And in NUREG-2216 difficult to achieve

- p7-49: The staff considers that adequate reactor operating records that identify only gaseous or volatile decay products (no heavy metals) in the reactor coolant system are acceptable evidence that cladding breaches are no larger than a pinhole leak or hairline crack.

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Gross Rupture Topical Report

Scope

- Implement new definition to use chemistry records in lieu of fuel inspections (e.g. sipping) to demonstrate cladding integrity Safety benefits of New Gross Rupture Definition

- Better comply with ALARA principles Reduce dose to the workers

- Reduce risk Avoid unnecessary handling by minimizing need for sipping campaigns and pool-side exams

New definition of gross rupture FSARs and CoC do not preclude to clarify NRC guidance and allow the use of the new gross stakeholders to use consistent rupture definition and actionable metrics Clarity Efficiency Reliability

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Gross Rupture Topical Report

Topical report

- Technical basis for new definition of gross rupture based Input from Gross Rupture PIRT Guidance regarding:

- Applicability criteria (e.g., quality of chemistry records)

- Key parameters to survey (e.g., increase in fuel products concentration during cycle and vs.

previous cycle)

Impacts on SRP and other NRC guidance documents

- Generic Directly referenceable by licensees Expected Industry Actions Expected NRC Actions

CoC amendments may not needed Review / approve TR (SER)

Most CoCs already have wording that allows using Revise guidance (SRP storage and transportation) the new definition industry does not need to wait to start Underlying documents for fuel qualification may implementing once SER is issued need to be changed + criteria used in site Revise inspection criteria procedures

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Benefits for the NRC

Clarification of NRC guidance Reduce risk inconsistencies - Eliminate unnecessary fuel moves

- Definition of gross rupture currently non-Better compliance with ALARA actionable by industry principles

- Inconsistency between storage and - Eliminate unnecessary dose-consuming transport SRPs activities

- Comply with principles of good regulation Generic implementation of criteria Reduce undue burdens change for broad adoption - Reduce number of damage fuel containers

- Reduce regulatory burden and review Recommendations to update guidance

- RCS chemistry applicability criteria

- Technical justification of key parameters

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PCT and Graded Approach

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PCT and Graded Approach Topical Report

Scope

- Implement increased PCT limit of 450oC Include a graded approach for storage and transportation safety analyses Safety benefits

- Shorter loading times Compliance with ALARA principles, such as:

- Fewer canisters loaded

  • Public: Less transportation events (precursor)

- Regulation efficiency increased

  • Wo r ke r s : Increased shielding, Fewer/shorter

- Risk-informed analyses leveraged loadings Operational Flexibility

- More time for certain operations,

- Eliminate supplemental cooling system,

- Add shielding

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Peak Cladding Temperature - Graded Approach

Performance Margin - Fuel rod has additional capacity to go to higher temperature without failure Methods Margin - Conservatisms in the modeling Graded approach would require increased analytical rigor to tighten uncertainties as you approach 450° C limit PCT (° C)Uncertainties reduction through analytical rigor

450

425

400

Analytical Rigor Objective: Develop a risk-informed and graded approach and avoid making licensing more complicated with additional analyses where more margin exists

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NAC-STC High-Burnup Fuel Amendment

Excessive analytical level of detail (academic exercise) required for a licensed system resulting in no impact to the safety of the design NAC initially provided thermal analysis, based on the existing NRC approved thermal methods/models for the NAC-STC to support reasonable assurance the cask would perform as required

  • No basket design changes
  • Change in individual fuel thermal loads and loading pattern NRCs thermal reviewers suggested that NAC needed to develop and qualify new, best estimate models for assessing HBU fuel performance, and included directions to use NUREG -

2152 (authored by the thermal reviewers) for the development and qualification of thermal models

©2019 Nuclear Energy Institute 18

18 Why the industry believes the PIRT work and applying Risk Informed criteria is Valuable

In 2019-20, NAC submitted an amendment for a content change using the license basis MOE.

Ultimately, regulatory direction, via RAI, was for NAC to develop 3 brand new discrete thermal models to support a methodical discretization allowing performance of a Grid Convergence Index (GCI).

Why? Because NACs reported PCT was within 25C of the 400C limit If the PCT limit is really a safety limit and Risk Informed Regulation determines that reporting temperatures within some percent triggers the need to address uncertainties (i.e. GCI performance) then this should be clear to the licensee through regulation and not invoked through the RAI process.

After a long RAI process ultimately involving the GCI methodology, the associated costs to the project and delays in licensing resulted in a little over one degree F lower PCT for the three additional models.

©2019 Nuclear Energy Institute 19

19 NAC-STC High-Burnup Fuel Amendment (Contd)

NAC was had no choice but to develop 3 brand new discrete thermal models (utilizing 900K, 3000K, 7200K elements including mesh refinement in axial direction) to support a methodical discretization allowing development of a Grid Convergence Index (GCI)

Model ID Number of PCT (F) T (F)

Hexahedral Elements

Model No. 1 7,168,000 633 151 Model No. 2 3,024,000 632 151 Model No. 3 896,000 629 151 Base Model 95,672 638 153

Performance of this work required over 2000 additional man -hours, demonstrated no significant change in PCT and resulted in no changes to the design or loading configuration(s)

Proximity (~25F) of our calculated PCT, with no credit given for conservatisms in the model, to the PCT limit was used as the basis for requiring the GCI be performed

©2019 Nuclear Energy Institute 20

20 Benefits for the NRC

Improved clarity, efficiency, and reliability

- Graded approach to apply resources more efficiently and effectively Generic implementation of criteria change for broad adoption

- Reduce regulatory burden and review Recommendations to implement updated metrics into future NRC guidance

- Clarify limits and uncertainties

- Reflect better understanding of thermal margins into NRC guidance Risk-informed application of operational margin to be leveraged to:

- Decrease dose to the workers

- Decrease operational risks by eliminating unnecessary actions

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Implementation

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Potential Pathway

Fee waiver Gross Rupture TR SER Next: request NRC Review SRP / Guidance Gross Rupture Plant Procedure Up d ates

TR Up d ates

Future: PCT TR

Fee Case Study SER waiver Gap Data PCT TR NRC Review request Vendor CoC Amendment NRC Review Amendments Plant document updates

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Timeline

September 2024: Fee Waiver Request Letter for If fee waiver for Gross Rupture TR GR approved Q1 2025: Gross Rupture TR Duration NRC review?

TBD: Fee Waiver Request Letter for PCT and Graded Approach TRIf fee waiver

for PCT approved TBD: PCT and Graded Approach TR

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Summary

- The 5 PIRTs provide strong basis to improve regulatory efficiency, clarity and reliability for all stakeholders.

- Objective is to improve safety and efficiency:

Decrease dose to the workers Reduce accident precursor events (transportation)

Improve realism to optimize safety and efficiency

- Near term: Gross Rupture TR Fee waiver request Directly applicable recommendations to improve regulatory guidance

- Longer term: PCT and Graded Approach TR Increased PCT limit Graded approach Operational impacts

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TOGETHERSHAPING THE FUTURE OF ENERGY

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