Iran can enrich enough uranium to weapons-grade for five nuclear devices within a week, analysts have claimed.
But Tehran’s ability to build a viable missile-launched weapon is expected to take between six and 18 months, according to western intelligence reports.
Following threats from US President Donald Trump, Iranian supreme leader Ali Khamenei’s senior adviser said that it would acquire such a weapon if attacked.
“We are not moving towards [nuclear] weapons, but if you do something wrong in the Iranian nuclear issue, you will force Iran to move towards that because it has to defend itself,” Ali Larijani told state television on Monday.
That makes the coming months a crucial period for the region, said Dr Sanam Vakil, of the Chatham House think tank in London.
“We are in a crisis year where we could see negotiations, an Israeli attack and weaponisation all take place,” she told The National.
“There's a sequence to how this is going to go. To justify weaponisation, there will have to be an attack and for there to be an attack there will have to be efforts at negotiation.”
Eight bombs, two weeks
Although none of Iran’s centrifuges are enriching uranium to the 90 per cent level that defines weapons-grade material, it has a stockpile enriched to 60 per cent, according to the Washington-based Institute for Science and International Security.
With further enrichment, that material could fuel “up to five nuclear warheads within one week or eight within two weeks”, said Darya Dolzikova, an expert on nuclear proliferation at the Rusi think tank.
Iran Watch, which tracks the country’s ability to make nuclear weapons, also confirmed the figures but added in a report last month that for the uranium to pose a nuclear threat it would have to be processed further into weapon components.
It also said that if Iran chose to make nuclear weapons “it could do so at secret sites” rather than a well-known location, as “in a dash to make weapons…it would risk detection before success”.
Nuclear missile ‘unknowns’
While the material for making a bomb could be done quickly, the greater difficulty is to build and test a bomb, place it on a missile and fire it.
“Uranium is no longer a problem for the Iranians but to develop a nuclear weapon to put that fissile material into it is the bigger question, a much bigger unknown,” said Jeremy Binnie, an Iran missile analyst at Janes, the defence intelligence company.
The Khorramshahr is the most likely missile to be used as its 1,800kg payload would allow it to carry a nuclear device as far as 2,000 kilometres, putting Tel Aviv within range.
The first step will be moulding the uranium into a ball then developing a trigger mechanism to initiate the nuclear reaction for detonation.
“That's actually a pretty complex device to manufacture, as you need to wrap conventional explosives to the trigger mechanism housing,” said Mr Binnie.
Iran would also need to rebuild explosive testing chambers as the site in Parchin was taken down following the 2015 nuclear agreement.
“Intelligence estimates indicate that the Iranians aren't that advanced, and that will handicap their ability to very quickly develop a deliverable nuclear weapon,” Mr Binnie added.
That device would need 16kg of uranium U-235 for one weapon. However, if Iran chose to move more quickly, it could go with a 7kg nuclear warhead.
This would have a yield of just under the 16,000 tonnes of conventional explosives equivalent of the bomb dropped by the US on the Japanese city of Hiroshima in 1945, according to Iran Watch.
“Some experts believe that Iran could use less material, assuming Iran would accept a lower yield for each weapon,” its report said. “Iran could use as few as seven kilograms if Iran’s weapon developers possessed a 'medium' level of skill.”
Deep tunnels
Ms Dolzikova said intelligence estimates put Iran’s capability for a nuclear missile at between six and 18 months, which allows time to fully plan strikes.
But Iran has been only too aware of the likelihood of an attack on its nuclear programme and has dispersed and fortified its facilities.
Natanz, located 225km south of Tehran, is Iran’s flagship enrichment site with four tunnels bored into the mountain providing underground protection against air strikes.
Fordow, a heavily reinforced plant embedded in a mountain near Qom, was a former Islamic Revolutionary Guard Corps base built to withstand attack.
Much of its other sites can be dispersed, although they are vulnerable to both Israeli and American intelligence finding them either from human sources or satellite and communications intelligence.
Massive Ordnance Penetrator
Currently the US, Iran, Israel and European powers were “in the war of words and pre negotiation phase”, said Dr Vakil, but the clock was running out as there was a September deadline for the E3 countries (UK, France, Germany) to call in the “snapback mechanism” of UN sanctions against Iran that expire the following month.
“If they don't make a deal, there will be bombing,” Mr Trump told NBC News on Sunday. “It will be bombing the likes of which they have never seen before.”
But attacking its sites will come with great risk and be complex, although Israel has already demonstrated its ability to decimate Iran’s air defences with its air strikes last October.
To destroy mountain and tunnelled sites, beyond a nuclear weapon only the US-made GBU-57 Massive Ordnance Penetrator (MOP), a 13,000kg bomb, is capable of penetrating deep into the earth to destroy subterranean centres.
But the only aircraft that can carry the GBU-57 are the USAF’s B-2 or B-1 bombers.
Israel’s most powerful bomb, the GBU-28, can penetrate some bunkers but not deep enough for targets buried under mountains.
If Israel were to attempt a strike with its F-15I fighter bombers, it would face serious logistical challenges, including the need to refuel mid-air for long-range flights, as reported last year by The National.
