All of these options are technically feasible, but none are what was originally planned, and all introduce major new uncertainties regarding the design and operation of future storage and disposal facilities.  These uncertainties will impact already large and uncertain future costs:  for example, as part of its 2013 assessment of the adequacy of the Nuclear Waste Fee to meet total disposal costs, the DOE estimated a range for $24 billion to $81 billion (2012 dollars) for future repository costs, not including costs associated with repackaging spent fuel.   

The dual purpose storage canisters themselves are large:  up to 2 meters in diameter and 5 meters in length, and the largest currently in use accommodate up to 37 intact fuel assemblies from pressurized water reactors, which account for about two thirds of the U.S. reactor fleet. A loaded canister may weigh on the order of 70 metric tons, and transportation shielding may increase the weight to 150 metric tons. Because it is economically advantageous for nuclear power plants to load larger canisters, the canister size exceeds sizes and weights that may be optimal for transportation and subsequent disposal.  Engineering solutions for hoist, ramp, and transporter operations appear to be feasible, but need to be accounted for in planning.

Although dual purpose canisters are certified by the Nuclear Regulatory Commission for both storage and subsequent transportation, the certificates of compliance set different temperature limits for storage versus transportation. This results in a situation where some canisters may need to cool before they can be transported. This delay may be on the order of decades for some canister designs, and in particular for higher-burnup fuels that generate more heat.

With respect to disposal, different geologies impose different temperature constraints on the underground environment. For example, some repository designs have assumed that the maximum temperature in clay backfill must remain below 100˚C, while salt may accommodate temperatures up to 200 to 250˚C. High thermal loads may be accommodated by cooling canisters above ground for many years, ventilating the repository for many years after waste emplacement, or increasing the spacing between canisters.  These choices will affect repository costs.

Constructing consolidated interim storage facilities has the potential to alleviate storage concerns at reactor sites and may provide a path to resolution of legal issues associated with federal responsibility for spent fuel management.  Consolidated storage facilities could also be used to provide flexibility in repackaging options for ultimate disposal.  Consolidated storage facilities will introduce additional cost and siting concerns, and technical issues associated with the mechanical effects of repeated transportation and storage will need to be addressed.

All options for the management and disposal of commercial spent nuclear fuel currently under consideration in the U.S. will require legislative and regulatory actions.