Spent Fuel Management at “Stand Alone ISFSI” Sites

Spent Fuel Management at “Stand Alone ISFSI” Sites

By: Paul Plante, Project Manager

Connecticut Yankee/Maine Yankee/Yankee Rowe

IAEA Technical Meeting on the Management of Spent Fuel at Shutdown Reactor Sites: 11-13 June 2018

What is an Stand Alone ISFSI?


It is a site where: • The reactor building and associated structures

have been decommissioned, • The associated waste has been removed, • The licensed facility has been reduced in size

and scope to an ISFSI. • The facility is in steady state, long term

operating mode awaiting fuel package removal by the federal government.

Before


After


The 3 Yankees

CY

YR Connecticut Yankee 40 Spent Fuel Dry Casks 3 GTCC Dry Casks NAC MPC System CoC Expires 4/10/20

Yankee Rowe 15 Spent Fuel Dry Casks 1 GTCC Dry Casks NAC MPC System CoC Expires 4/10/20

Maine Yankee 60 Spent Fuel Dry Casks 4 GTCC Dry Casks NAC UMS System CoC Expires 11/20/20

MY


Cask System Life Cycle at ISFSI Only Sites • Initial 20 year license life.

During this time, inspection and maintenance requirements are found in the initial Certificate of Compliance (CoC) or Site Specific License and the FSAR.

• Period of Extended Operation (40 years) During this time, revised inspection and

maintenance plans will be found in the renewed CoC or Site Specific License and the FSAR.


Spent Fuel Issues for Stand Alone ISFSI Sites

• Cask system maintenance, inspections and repairs.

• Dry storage system amendments and relicensing.

• Aging management for dry storage systems. • Canister susceptibility to aging mechanisms

(Such as CISCC). • Site characterization for aging management. • Potential repair and mitigation issues.


-Cask system maintenance and inspections-


Requirements for the initial 20 yrs. are in the CofC and FSAR: • Cleaning and sealing casks and pads, • Annual Inspections of the casks and pads, • Coating repairs, • Concrete repairs when necessary, • Temperature monitoring system maintenance

and upgrades.

Typical Vertical Concrete Cask


Cask system maintenance and inspections


Examples of Reportable Tier 3 Damage


Third-Tier Crack

Pad Delamination From Original Construction


-Dry Storage System Amendments & Relicensing-

• Complicated and ever evolving. • NRC developing and revising NUREG’s. • NEI 14-03 Guidelines to the industry. • EPRI activities and the technical basis for

relicensing. • ASME Code Case development. • Sometimes involves amendments to address

operating issues.




-Aging Management for Dry Storage Systems-

• Will require new site specific program and procedures to be integrated into the existing site architecture.

• Will be based on a standardized approach identified in the MAPS NUREG and NEI 14-03 Industry Guidance.

• Canister Inspections will be based on EPRI Aging Management Program published in March, 2017 and eventually on ASME Code Case N-860.


Aging Management Approach


Canister susceptibility to aging mechanism-SCC


• Using EPRI Susceptibility Criteria, determine the relative ranking of canisters and their susceptibility to CISCC.

• Results: • Maine Yankee: ZISFSI = 2 / Vcan = 4-5 • Conn. Yankee: ZISFSI = 1 / Vcan = 4-5 • Yankee Rowe: ZISFSI = 1 / Vcan = 5

• Use this ranking, OE and known environmental characteristics of the ISFSI to develop a strategy for canister inspections.

Maine Yankee Located on the Back River Brackish Water-Tidal About 12 miles from Open Ocean


Determine the nature of the site environment: - For use in EPRI susceptibility rankings. - To determine the significance of Operating experience from other sites. - To assess the nature of the site using technical literature on atmospheric corrosion.

-Site characterization for aging management-

Atmospheric Sampling Program • Started in August 2012. • Utilizes a Hi-Q continuous

duty air sampler. • Adjustable flow 20-100 lpm


Seasonal Comparison of Atmospheric Conditions

0

0.5

1

1.5

2

2.5

Atm

osph

eric

Con

cent

ratio

n (µ

g/m

3 )

Month

Atmospheric Chloride Concentration: Maine Yankee ISFSI & Acadia National Park CASTNET Site

ANP High

MY ISFSI High

ANP Low

MY ISFSI Low


SEM/EDS Analysis of Atmospheric Samples Typical particles collected on 5 micron PTFE Filter

Elemental map of particles collected

Chloride-containing particles isolated


Atmospheric Chloride Deposition: Wet Candle Testing

• Based on ASTM G140-02



Wet Candle (Chloride Deposition Rate) Result Comparison Site Time period Distance to

source Range of values (mg/m2/day)

Maine Yankee ISFSI 2013-2017 19K meters (to open ocean)

1.0 – 5.1

Yankee Rowe ISFSI 2014-2017 160K meters 0.8 – 2.0

Kure Beach, NC (near-ocean) 1

1962-1998 250 meters 50 - 200

Kure Beach, NC (oceanfront) 1

1962-1998 25 meters 200 - 700

Cape Town, South Africa3

2013-2014 50 meters 126.69

2013-2014 150 meters 27.26

2013-2014 250 meters 30.87

2013-2014 2.7K meters 11.23

2013-2014 13.5K meters 10.54

Surface Salt Sampling - Methods

2014 Sampling Event:

Wipe samples were collected using PTFE, dry cellulose, and wetted cellulose media

Samples collected from vertical and horizontal vent surfaces

2016 Sampling Event:

Objective: collect measurements on vents, shield plug, and from within canister in coordination with EPRI NDI robot demonstration

Tested surfaces: Inlet & outlet vents on three storage casks:

VCC2 inlet & outlet

VCC9 inlet & outlet

VCC20 inlet & outlet

Shield plug

Coated steel cask base

Analysis Laboratory analysis of chloride content

Elcometer in-situ analysis

SEM/EDS analysis of cask interior sample



Site Chloride Concentration (mg/m2)

Maine Yankee 0-11

SMUD5 18.5

Hope Creek6 <2.5 -60

Diablo Canyon6 2.0 – 58

Calvert Cliffs 7 < 50

Koeberg (Winter) 8 1,000 – 2,000

Koeberg (Summer) 8 2,500 – 5,000

Kure Beach (25m)9 76,000 – 228,000

Kure Beach (250m)9 21,000 – 60,000

NUREG/CR-717010 100 – 10,000

CRIEPI Threshold for 304L11 800

Surface Deposit Survey

Canister Inspection Approach


• The ROV was fitted with a borescope camera for inspections. • It can traverse 90° turns for navigating through the inlet and outlet vents

and is driven by magnetic wheels for vertical runs on carbon steel surfaces.

Canister Surface Inspection Footage (GTCC)


• Left view shows manufacturer’s identification number stamped on canister shell showing detail of inspection capability.

• Right view shows junction of a canister vertical and horizontal seam weld.

Canister Surface Inspection Footage


• Likely iron contamination from initial fabrication.

Potential repair and mitigation issues.


Industry initiatives to identify and scope various: repair options such as: mitigation options such as:

Welded repairs Peening or Burnishing Thermal Spray Coatings Brazing/soldering Contaminate traps Patch Repairs Periodic surface cleaning Non-metallic Encapsulation or coatings

Potential repair and mitigation issues.


One example: Failed Canister Over-pack at Maine Yankee

Summary


• Even in steady state ISFSI Only status, there are many issues requiring attention: • Involvement in industry activities particularly for

areas where policy is being developed. • Working with industry partners as well as

government agencies. • Supporting research and development on tools to

ensure long term adequacy of dry storage systems.

Abbreviations and Acronyms


• ASME: American Society of Mechanical Engineers • ASTM: American Society for Testing and Materials • CISCC: Chloride Induced Stress Corrosion Cracking • CoC: Certificate of Compliance • EPRI: Electric Power Research Institute • FSAR: Final Safety Analysis Review • GTCC: Greater Than Class C Waste • ISFSI: Independent Spent Fuel Storage Installation • MAPS: Managing Aging Processes NUREG Document • MPC: Multipurpose Canister System • NAC: NAC International • NEI: Nuclear Energy Institute • ROV: Remote Operated Vehicle • SEM/EDS: Scanning Electron Microscopy/Energy Dispersive Spectroscopy • UMS: Universal Multipurpose Storage System

Spent Fuel Management at “Stand Alone ISFSI” Sites

By: Paul Plante, Cask Relicensing Project Manager

Connecticut Yankee/Maine Yankee/Yankee Rowe


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Spent Fuel Management at “Stand Alone ISFSI” Sites

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