PressTV yesterday carried a threat from an Iranian lawmaker (and Reuters also reports the threat) that should the current round of P5+1 talks on Iran’s nuclear technology break down, Iran would begin enriching uranium to 60% in order to produce fuel for a nuclear-powered submarine. The state of Iran’s submarine technology suggests that this is mostly an idle threat, but there is a very easy route for the P5+1 group to diffuse the threat before it becomes a “red line” issue. France, a member of the P5+1 group, has a new generation of nuclear reactors for submarines that relies on a fuel known as “caramel”, which is only enriched to 7.5% uranium. Providing one of these reactors to Iran would allow them to power a submarine with nuclear fuel without having to enrich to weapons grade or near weapons grade.
The US Office of Naval Intelligence tells us (pdf) that Iran is the only nation near the Persian Gulf possessing submarines. However, the submarine fleet is meager and mostly composed of very small vessels. From the Nuclear Threat Initiative:
Iran’s submarine force currently consists of three Russian Kilo-class diesel-electric submarines (Tareq 901, Noor 902, Yunes 903), one 350-400-ton Nahang and an expanding force of roughly a dozen 120-ton Ghadir-class midget submarines.
The three Kilo-class diesel-electric submarines, called Tareq-class in Iran, were commissioned from 1992 to 1996. Iran allegedly paid USD600 million for each boat and they are all based at Bandar Abbas in the Straits of Hormuz (Tehran is reportedly contemplating the relocation of its submarines from the shallow waters of Bandar Abbas to naval facilities in deeper waters at Chah Bahar in the Gulf of Oman).  Two of the Kilo-class submarines are operational at any one time and they are occasionally deployed in the eastern mouth of the Straits, the Gulf of Oman or the Arabian Sea. Their utility in the Persian Gulf is, however, somewhat limited as Kilo-class boats require a depth of at least 164 feet and can therefore only access about one third of the Gulf. Unique water conditions (water salinity and strong currents) in the Gulf further limit the boats’ operational use unless the submarines are deployed to deeper waters in the Gulf of Oman or the Arabian Sea.
Only the kilo-class submarines, which Iran does not manufacture, are large enough to be powered by a nuclear reactor. And NTI tells us that a retrofit of one of the Russian kilo-class vessels would be the likely home of a nuclear reactor, but Iran does not have the technology for the reactor itself: Read more