SPENT FUEL CHARACTERIZATION PROCESS
Paloma Viñas Peña Spent Nuclear Fuel Engineer
Enusa Industrias Avanzadas [email protected]
IAEA TM on Spent Fuel CharacterizationVienna 12-14 November 2019
ENUSA APPROACH
engineer
engineer
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OUTLINE
ENUSA PROPRIETARY - CONFIDENTIAL
• INTRODUCTION
• ENUSA CHARACTERIZATION PROCESS
• WHAT ARE WE LOOKING FOR AND WHY
• Leaking fuel analysis
• Corrosion phenomenon
• Damages in top nozzle
• Other important data
• DATA & KNOWLEDGE MANAGEMENT ISSUES
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Operation Wet Storage( SNF Pool)
Dry storage(Dry Cask)
Deep Geological Storage
CentralizedTemporary
Storage
INTRODUCTION: Spanish boundary conditions and ENUSA activities
ENUSA activities are focus on the analysis of characteristics of the fuel assemblies stored in the SNF pool in order to ensure its proper management for storage and transport in dry cask
ENUSA PROPRIETARY - CONFIDENTIAL
Main objective: assure of fulfillment of the nuclear safety functions✓ Sub-criticality control✓ Confinement✓ Residual heat removal✓ Shielding✓ Retrievability
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ENUSA SPENT NUCLEAR FUEL CHARACTERIZATION (SNFC) PROCESS : What are we looking for and why?
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Enusa has developed a SNFC process that covers several areas and it is based on:
• Fulfillment of the nuclear safety functions
• International experience and ours (more than 600 fuel assemblies characterizedand classified for dry cask storage in the last 8 years)
Itemwith defects
Areas of analysis Safety functions affected to storage and transport in dry casks
CladdingIntegrity:✓ Leaks✓ Corrosion phenomenon
• Confinement• Sub-criticality control• Retrievability• Shielding Residual heat removal
Fuel assemblyLose of structural integrity
• Retrievability• Shielding Residual heat removal• Sub-criticality control
Damage in top nozzle • Retrievability
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ENUSA SNFC PROCESS: Leaking fuel analysis
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Data for analysis Why do we need?
NPP records of radiochemicalparameters
Identify the existence of leaks in the SNF assemblies that operated in the cycle
Fission products analysis codeIdentify number of leaks and their
characteristics
Inspections:• Sipping
• In-can sipping• In-mast sipping
• Ultrasonic• Visual inspections
Find out the leaking rod or failed assembly
Irradiation data:• Irradiation cycles• Position in each irradiation cycle• Burn up after each irradiation cycle• Burn up to EOL
For coherence analysis between the number of leaks estimated and
inspection’s results
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ENUSA SNFC PROCESS: Corrosion phenomenon
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Objective: Avoid rupture problems due to degradation phenomenon during dry storage and transportation
Data for analysis Why do we need?
Cladding materialDeveloped a predictive criteria which identify more likely cases Irradiation data:
• Burn up after each irradiation cycle• Burn up to EOL
Visual inspections1.- Based on spanish NPP´s operative experience it has been defined visual patterns to determine cladding spalling2.-Identify fuel assemblies affected
Oxide thickness calculations on critical vanesBelow a limit may be admissible with specific studies
Hoop stress at EOL calculations
Public spalling examples
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ENUSA SNFC PROCESS: Damages in top nozzle
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Top nozzle inserts fractured due to ISCCTop nozzle inserts intacts
Data for analysis Why do we need?
Manufacturing related data• Material• [%C]• Assembly process
Identify affected population
Visual inspections Identify elements with top nozzle inserts fractured
SNF pool inlet temperature
Identify more susceptible population
SNF pool chemical control
Irradiation history• Cycles on reactor• Cycles on SNF Pool
C1 C2 C3 C4 C5 C6 C7 C8
Resin exposure period
Group 1
Group 2
Group 3
Group 4
Group 5
Group 6
Group 7
Group 8
Group 9
Group 10
Group 11
19861981 1982 1983 1984 1985
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1987 1988 1989 1990 1991 1992
Failure rate
9
66
81
100
0
17
0
0
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ENUSA SNFC PROCESS: Damages in top nozzle
Spring screw fracture due to SCC
Data for analysis Why do we need?
Manufacturing related data• Material• Design• Drawings
Identify affected population
Nº Irradiation cycles
Visual and others inspections Identify elements with spring screws fractures
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ENUSA SNFC PROCESS: Other important data
Data for analysis Why do we need?
Result of visual integrity inspections • Oxide deposit analysis• Presence of foreign objects• Structural damage
Specific evaluation case to case in order to assure that SNF assembly keeps structural integrity during storage and transport
Manufacturing related data• Materials• Design specifications• Drawings
To perform:• Different calculations with codes • Shielding analysis• Other analysis
Data related to cycles• Burn up• Length• Chemistry program
International experience Identify possible problems for our fuel
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ENUSA SNFC PROCESS: Core component
ENUSA PROPRIETARY - CONFIDENTIAL
Data for analysis Why do we need?
Manufacturing related data• Materials• Design specifications• Drawings
ISG-9 requirementsIrradiation data:• Irradiation cycles• Position in each irradiation
cycle
International experience Identify possible problems
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DATA & KNOWLEDGE MANAGEMENT ISSUES
• A large population of SNF assemblies has to be characterized and different kinds of
data must to be:
✓ Accessible
✓ Reliable
✓ Easy to manage
• Some examples of data that need to be preserved:
✓ Manufacturing records
✓ Results of inspections
✓ Irradiation history
✓ Operative experience analysis
• Tool for knowledge management has been developed
ENUSA PROPRIETARY - CONFIDENTIAL
www.enusa.es
THANK YOU VERY MUCH FOR YOUR ATTENTION
ANY QUESTIONS?