SPENT FUEL CHARACTERIZATION PROCESS

Paloma Viñas Peña Spent Nuclear Fuel Engineer

Enusa Industrias Avanzadas S.A.S.M.Epvp@enusa.es

IAEA TM on Spent Fuel CharacterizationVienna 12-14 November 2019

ENUSA APPROACH

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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?

ENUSA PROPRIETARY - CONFIDENTIAL

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

8ENUSA PROPRIETARY - CONFIDENTIAL

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

9ENUSA PROPRIETARY - CONFIDENTIAL

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?