You're all working too hard on this.
The answer to nuclear waste involves two steps:
First, make sure you have a robust breeder cycle to help greatly reduce high-level wastes.
Second, do NOT bury the remaining wastes in inaccessible caverns.
Store it in heavily reinforced surface facilities, probably on military bases or military-type bases out in the wastelands of the U.S. Using an existing military base would be cheapest. Such facilities will protect the wastes from terrorists, protect the environment from the wastes, and be easily inspectable. More importantly, when someone comes up with a better solution, they'll be accessible in proper containers.
Hydrogen warheads are stored on such secure military facilities, and nobody's sweating blood about that.