actually, it is not as simple as keeping that uranium "spinning".
in order to have operational weapons grade uranium you need to establish a way to stabilize the reaction, and stabilize it in a way that keeps the uranium weapons grade, without having it cause a meltdown.
after that they have to design a way to start a reaction, this involves a canister being fired directly into the core of a reactor.
these mechanisms have to be designed, then scaled down to a size that will fit on a missile. that is not too easy, that is why america first had a BOMB that had to be towed by plane to it's destination. it took 20 years before the BOMB was fitted onto a rocket that would have the reliability and accuracy to deliver a nuclear warhead.
if it was as simple as operating centrifuges for a little longer they would have nuclear weapons already, the fact that they don't, only enforces the theory that the complexity and costs of the matter make it very VERY hard to design that system.
i'm not worried, not yet....