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.

Guidance regarding supplemental shielding that may be installed at an independent
spent fuel storage installation (ISFSI) to meet the requirements of 10 CFR 72.104(a).

The purpose of this guidance is to, (1) clarify the meaning of a real individual as used in 10
CFR 72.104, (2) specify how the applicant may perform dose evaluations beyond the controlled
area for site-specific and general Independent Spent Fuel Storage Installation (ISFSI) licenses,
and (3) clarify standard review plan (SRP) text regarding dose calculations outside the
controlled area.

Fuel rod buckling analyses under bottom end drop conditions have traditionally been performed
to demonstrate integrity of the fuel following a cask drop accident. The methodology described
by Lawrence Livermore National Laboratory (LLNL) to analyze the buckling of irradiated spent
fuel assembly under a bottom end drop in their report UCID-21246 is a simplified approach. It
assumed that buckling occurred when the fuel rod segment between the bottom two spacer
grids reached the Euler buckling limit. The weight of fuel pellets was neglected in the analysis;

The staff has broadened the technical basis for the storage of spent fuel including assemblies
with average burnups exceeding 45 GWd/MTU. This revision to Interim Staff Guidance No. 11
(ISG-11) addresses the technical review aspects of and specifies the acceptance criteria for
limiting spent fuel reconfiguration in storage casks. It modifies the previous revision of the ISG
in three ways: (1) by clarifying the meaning of some of the acceptance criteria contained in

There is no existing American Society of Mechanical Engineers (ASME) Code for the design
and fabrication of spent fuel dry storage casks. Therefore, ASME Code Section III, is
referenced by NUREG-1536, “Standard Review Plan for Dry Cask Storage Systems,” as an
acceptable standard for the design and fabrication of dry storage casks. However, since dry
storage casks are not pressure vessels, ASME Code Section III, cannot be implemented
without allowing some alternatives to its requirements.

Revision 1