Is it safeguarded from terrorists?

Deep geology provides a barrier that gives significant protection against a terrorist attempt to obtain spent nuclear fuel. Although the spent fuel is retrievable, doing so requires setting up a rig, removing thousands of feet of rock and bentonite sealant, and operating a fishing system to pull up canisters one at a time. That is a process an experienced crew can accomplish but the cost and difficulty does not lend itself to a surreptitious terrorist attack.