[nohat]

You said

> If you somehow got your hands on a modern nuclear weapon and you had a team of PhD engineers, a year of time, and the best tools in the world, you might be able to get the radioactive material out, but you absolutely would not make it explode.

I'm saying that there's no "might" about extracting the radioactive materials. Nor do you need "a team of PhD engineers, a year of time, and the best tools in the world". An angle grinder and a couple days should suffice.

As for making it explode, that may indeed be very difficult, but I am not highly confident given the military's general attitude and track record. Hopefully my cynicism is unfounded, but supercomputer simulations primarily designed to ensure that aging weapons still function doesn't really help with security.

[dreamcompiler]

The US military does not design US nuclear weapons or their safety systems. Of course military requirements are factored in, but design responsibilities and final authority for use are in civilian hands, by law. That's why the Department of Energy is a separate entity from the Department of Defense.

Obviously the military could make mistakes when the weapons are in their custody, but civilian designs make sure those mistakes don't cause an unplanned detonation. Nor can a rogue military unit arbitrarily decide to start WW III. If they tried, the weapons would turn into bricks.