Regulatory Guide 3.78
| ML25120A238 | |
| Person / Time | |
|---|---|
| Issue date: | 05/07/2025 |
| From: | Darrell Dunn NRC/NMSS/DFM/MSB |
| To: | |
| References | |
| RG-3.078 | |
| Download: ML25120A238 (1) | |
NRC Regulatory Guide 3.78 Darrell Dunn Senior Materials Engineer Materials and Structural Branch Division of Fuel Management Office of Nuclear Material Safety and Safeguards May 7, 2025
Topics
Renewal reviews
Dry storage system certificate of compliance (CoC)
Independent spent fuel storage installation (ISFSI) licenses
Chloride induced stress corrosion cracking (CISCC) operating experience
American Society of Mechanical Engineers (ASME) Code Case N-860
NRC Regulatory Guide (RG) 3.78
Potential approach for non-inland ISFSI sites
Summary May 2025 NEI Used Fuel Management Conference
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CoC and ISFSI license renewals
- NUREG-1927, Revision 1, Standard Review Plan for Renewal of Specific Licenses and Certificates of Compliance for Dry Storage of Spent Nuclear Fuel June 2016
- NUREG-2214, Managing Aging Processes in Storage (MAPS) Report July 2019 oRenewal review is not a reevaluation of the technical basis for the original CoC
or ISFSI license approval oAssure continued safe operation oConsider potential aging mechanisms and effects
- Aging management review oUpdate time limited aging analyses (TLAAs)
oSupplemental evaluations (if necessary)
oAging management programs (AMPs)
May 2025 NEI Used Fuel Management Conference
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CISCC operating experience
- Observed on components at operating reactors located close to a saltwater shoreline
- Considered credible for stainless steel dry storage canisters based on:
o Operating reactor experience o Canister design and materials o Operating environments
- Inspections conducted to date have not shown evidence of CISCC on dry storage canisters o Decay heat may have prevented salt deliquescence o No inspections yet at ISFSIs sites with the highest CISCC susceptibility ranking Koeberg Fontevraud 7 A108T03 Sept 2010
Philip Doubell May 2025 NEI Used Fuel Management Conference
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- Developed from 2015-2020 after a request from the NRC to ASME
- Applicable to welded, austenitic stainless steel canisters exposed to ambient air by passive ventilation
- Assumes that CISCC is the most credible and bounding degradation mechanism
- Uses EPRI-3002005371, Susceptibility Assessment Criteria for CISCC to set initial inspection population oCISCC ranking: ZISFSI = Clstarting + Cladj + AHadj oHigh rank site: ZISFSI 8 oLow rank site: ZISFSI 7 May 2025 NEI Used Fuel Management Conference
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- Examinations on welded regions of canisters oCISCC
oIndications of localized corrosion
- Progressive inspection methodology oVisual screening examination oVisual assessment examination oSupplemental examination (surface or volumetric)
- Maximum inspection interval can be increased from 10 to 20 years for ZISFSI 7 sites with no indications of CISCC
May 2025 NEI Used Fuel Management Conference
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Regulatory Guide 3.78 Purpose and Applicability Identify acceptable ASME Boiler and Pressure Vessel Code (ASME Code),
Section XI, Inservice Inspection Code Cases for use by ISFSI specific licensees, general licensees, and certificate of compliance (CoC) holders licensed under Title 10 of the Code of Federal Regulations (10 CFR) Part 72.
ASME Code Case Endorsement ASME Code Case N-860, Inspection Requirements and Evaluation Standards for Spent Nuclear Fuel Storage and Transportation Containment Systems May 2025 NEI Used Fuel Management Conference
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Opportunity to risk inform NRC guidance on CISCC AMPs
- Methodology in ASME
oCISCC susceptibility assessment oInspection intervals
- Additional information oPower reactor operational experience with CISCC
oISFSI locations oInspection results Jerry Stephenson, Manager, ISFSI Engineering San Onofre Community Engagement Panel Meeting Thursday, March 20, 2025 May 2025 NEI Used Fuel Management Conference
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Canister inspection intervals may be safely increased Up to 40-year inspection interval for inland ISFSI sites (ZISFSI 3)
- Low probability of CISCC initiation
- Slow CISCC growth rate oAbsence of aggressive chloride containing salts oLow, or very low, surface chloride concentrations oLow chloride load, with relatively high concentrations of nitrate May 2025 NEI Used Fuel Management Conference
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Potential approach for non-inland ISFSI sites
- Probability of CISCC occurring under representative conditions oSalt deposit composition oRelative humidity
- Consequence analysis for CISCC of the confinement barrier oDose from fuel particulates, crud, volatile species, and noble gasses oSettling of fuel particulates oSlow release rate oHelium loss and subsequent effects on the fuel EPRI-3002005371 ZISFSI
Number of ISFSI sites (estimated)
Number of canisters (estimated)
Maximum inspection interval (yr)
1-3
60
3,259
40
4-7
6
307
20
8-10
5
315
10
May 2025 NEI Used Fuel Management Conference
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Summary
- Improved efficiency by endorsement of ASME Code Case N-860 in Regulatory Guide 3.78 with increased inspection intervals up to 40 years for ZISFSI 3 sites
- Licensing: Aging Management Program (AMP) development licensees/CoC
holders and NRC review of renewal applications
- Oversight: AMP implementation, increased inspection intervals, and NRC
inspection of licensees procedures
- Potential work to evaluate increased inspection intervals at non-inland ISFSI sites
- Regulatory Guide 3.78 may be updated to include future acceptable ASME
Section XI code cases applicable to 10 CFR Part 72 licensees and CoC holders May 2025 NEI Used Fuel Management Conference
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NRC Regulatory Guide 3.78 Darrell Dunn Senior Materials Engineer Materials and Structural Branch Division of Fuel Management Office of Nuclear Material Safety and Safeguards May 7, 2025