The purpose of this interim staff guidance (ISG) is to supplement standard review plan guidance
for evaluating the helium leakage testing and ASME Code1
required pressure
(hydrostatic/pneumatic) testing that is specified for the dry storage system (DSS) confinement
boundary. These acceptance tests are necessary to clearly demonstrate that the DSS
confinement boundary has been fabricated in accordance with the design criteria, and that its
operation complies with the intended safety bases of the confinement system and regulatory

Under the current guidance in ISG-1, Revision 1, “Damaged Fuel,” the definition of intact fuel
includes fuel rods containing no cladding defects greater than pinhole leaks or hairline cracks.
During the cask water removal process parts of, or all of, the fuel rods will be exposed to a
gaseous atmosphere. If the gaseous atmosphere is oxidizing, oxidation of fuel pellets or fuel
fragments can occur if a cladding breach exists (such as a pinhole). Oxidation may occur

Given the growing industry need to store spent reactor fuel of increasingly higher burnups and
heat loads in dry storage casks, and eventually to transport that same spent fuel in
transportation packages, analyzing the performance of casks and other radioactive material
packages has become a greater challenge. Finite Element, Finite Difference, and Finite
Volume analysis computer codes, defined here as Computational Modeling Software (CMS),
are tools used by many licensees to analyze cask and package performance in the structural

The standard review plans for storage of spent nuclear fuel and transportation of fissile
materials do not address, in detail, the technical considerations for crediting the neutron
absorber content of metal matrix composites used for preventing nuclear criticality. The Division
of Spent Fuel Storage and Transportation (SFST) considers the application of acceptance
criteria and methodology described in the recently developed American Standard for Testing
and Materials (ASTM) standard practice C1671-07, “Standard Practice for Qualification and

Authority for licensees to transport radioactive material comes from 10 CFR Part 71. Licensees
are authorized to transport Type B quantities and fissile materials in NRC-certified packages
under the general license in 71.17. Unlike 10 CFR Part 72, Part 71 does not include change
authority, that is, there is no specific Part 71 regulation that allows licensees to make changes in
the design or operation of an NRC-certified package without prior NRC approval. However,

This Interim Staff Guidance (ISG) provides review guidance for meeting the fissile material
package standards in 10 CFR 71.55(e). The provisions of 71.55(e) require that a fissile
material package be subcritical under hypothetical accident conditions assuming that the fissile
material is in the most reactive credible configuration consistent with the damaged condition of
the package and the chemical and physical form of the contents, and water moderation occurs
to the most reactive credible extent consistent with the damaged condition of the package and

The purpose of this ISG is to address the design and testing of the various closure welds (“lid
welds”) associated with the redundant closure of all-welded austenitic stainless steel canisters:

As an acceptable confinement boundary under 10 CFR Part 72.236(e) (Ref. 1) for
purposes of demonstrating no credible leakage of radioactive material during storage
and satisfying the dose limits under normal and off-normal conditions in 10 CFR Parts
72.104(a) and 72.106(b).

Guidance is necessary on the interim storage of greater than Class C (GTCC) waste due to the
revision of Title 10 of the Code of Federal Regulations (10 CFR) Part 72. The revision to 10
CFR Part 72 is documented in final rule, ìInterim Storage for GTCC Waste,î and permits the
storage of GTCC wastes at independent spent fuel storage installations (ISFSI) or monitored
retrievable storage (MRS) facilities. The GTCC wastes, if stored at an ISFSI, must be in solid
form, and stored in a separate container (i.e., GTCC waste may not be stored in a cask that

Issuance of specific guidance for review of Emergency Plans for facilities licensed pursuant to
10 CFR Part 72 and removal of the reference to Regulatory Guide 3.67, "Standard Format and
Content for Emergency Plans for Fuel Cycle and Materials Facilities," as included in NUREG-
1567, Standard Review Plan for Spent Fuel Dry Storage Facilities (March 2000).

Due, in part, to a number of material-related issues identified during dry cask storage system
(DCSS) and transportation package application reviews and field implementation, the staff has
recognized the need for specific guidance for the review of materials selected by the applicant
for its DCSS or transportation package.