They do have reactors though, do they not? Hitting the spent fuel pools and/or the reactors would produce detectable radioactive contamination. The HEU? Not so much as its half-life is 700 million years, and the stuff is dense and will quickly settle down.
Why would they not have reactors? Plutonium bombs are more efficient than uranium bombs, so of course they should want to make some plutonium. Remember, they claim they need HEU for civilian reactors.
