The Times of London claims to have a document indicating that Iran is working on uranium deuteride neutron initiators for nuclear weapons.
The article, like so many of its type, presents a document of unknown provenance from anonymous sources. Mark Fitzpatrick, a reliable analyst, is quoted, but I wouldn't be surprised if the more sensational of his quotes were taken out of context. And he attaches strong "if" clauses to what he's said.
Jeffrey Lewis notes that A. Q. Khan, who's been restless lately, has talked about uranium deuteride as a neutron initiator, and that Iran has gotten information from Khan. So Khan or one of his circle may be the Times's "Asian intelligence source," thoroughly unreliable, as Albright points out in that link and I did earlier.
And the timing, just as sanctions are being discussed and Iran makes another proposal, seems suspicious. Every time Iran tries to get a bit more credibility (and it certainly could do that more effectively!), something like this shows up. Sort of makes one suspicious.
Update: Bob Mackey has a good post about secrets when they don't stay secret.