Henry Sokolski at NRO delivers this whopper:
[T]he fuel that France and Russia will send back to Iran will be far more weapons-usable it will be enriched with 19.75-percent nuclear-weapons-grade uranium than the 3.5-percent-enriched brew Iran currently has on hand. If Iran were to seize this more enriched fuel, it could make a bomb much more quickly than it could now.
Michael Roston sighs:
Iran isn’t going to get back fuel that “will be far more weapons-usable.” In fact it’s getting the opposite. Iran sends Russia the uranium gas it has, which enriches it to a higher level. Russia sends the fuel to France. France fashions the uranium into metal fuel rods that can be used in the reactor. To make that bomb usable, you’d have to take it out of fuel rod form and enrich it more, and then fashion it into a functioning warhead.
I’m not saying the guys at Los Alamos or at the best Russian labs couldn’t figure this out if they screwed around for a really long time with endless resources. But it’s not exactly how you go about building a credible nuclear deterrent.