Several changes have occurred since the issuance of NUREG-1536, “Standard Review Plan
(SRP) for Dry Cask Storage Systems,” that affect the staff’s approach to confinement
evaluation. The attachment to this ISG integrates the current staff approach into a revision of
ISG-5. The highlights of the changes include:
• Reflects October 1998 revisions to 10 CFR 72.104 and 10 CFR 72.106.
• Expands and clarifies acceptance criteria associated with confinement analysis and
acceptance of “leak tight” testing instead of detailed confinement analysis.

The closure weld for the outer cover plate for austenitic stainless steel designs may be
inspected using either volumetric or multiple pass dye penetrant techniques subject to the
following conditions:
• Dye penetrant (PT) examination may only be used in lieu of volumetric
examination only on austenitic stainless steels. PT examination should be done
in accordance with ASME Section V, Article 6, “Liquid Penetrant Examination.”
• For either ultrasonic examination (UT) or PT examination, the minimum

Compliance with 10 CFR 72.122(l) has been interpreted to mean that a licensee, during any
point in the storage cycle, must have a means of retrieving and repackaging individual fuel
assemblies even after an accident. The staff has reevaluated this interpretation.

This Interim Staff Guidance (ISG) provides guidance to the staff for determining if
storage systems to be licensed under 10 CFR Part 72 allow ready retrieval of spent fuel.
This guidance is not a regulation or a requirement.

This Interim Staff Guidance (ISG) provides guidance to the staff on classifying spent nuclear
fuel as either (1) damaged, (2) undamaged, or (3) intact, before interim storage or
transportation. This is not a regulation or requirement and can be modified or superseded by
an applicant with supportable technical arguments.

Revision 2

Stress corrosion cracking (SCC) of welded stainless steel dry storage canisters may potentially impact systems exposed to corrosive atmospheric elements, such as those occurring near salt water bodies. Conditions important for atmospheric-related SCC include concentration and chemical species of the contaminants, temperature, and humidity. Calvert Cliffs Nuclear Power Plant conducted this historically important first inspection of spent fuel canisters to collect data for an SCC evaluation as part of the EPRI-led Extended Storage Collaboration Program (ESCP).

Due to the delayed opening of a final geological repository for spent nuclear fuel, the lifespan of dry cask storage systems may be increased to 120 years or longer. To ensure safety over this extended period of interim storage, degradation mechanisms that have the potential to cause penetration of the canister confinement boundary must be evaluated and understood.

Use of an on-site dry transfer system (DTS) allows utilities with limited crane capacities or other plant restrictions to take advantage of large efficient storage systems. By using this system, utilities can also transfer fuel from loaded storage casks to transport casks without returning to their fuel storage pool.

The main question before the Transportation and Storage Subcommittee was whether the United States should change its approach to storing and transporting spent nuclear fuel (SNF) and high-level radioactive waste (HLW) while one or more disposal facilities are established.

This study provides a technical basis for informing policy decisions regarding strategies for the management and permanent disposal of spent nuclear fuel (SNF) and high-level radioactive waste (HLW) in the United States requiring geologic isolation. Relevant policy questions this study can help inform include the following: Is a “one-size-fits–all” repository a good strategic option for disposal? Do