[From One - Many]

Also from the article: Proponents point out that this is a plus, as it is difficult to re-use pebble bed reactor waste for nuclear weapons.

Thus difficult but not impossible.

[Red Badger]

Difficult is an understatement. The individual balls are ceramic, and the nuclear materials are dispersed within that ball like the ingredients in a cake. It would be like trying to reclaim the cake’s ingredients.
The process of retrieving the nuclear materials would not be impossible for someone with the super sophisticated technology of a nuclear superpower, but would be wholly impractical for a small terrorist organization................