Iran nuclear sites may be beyond reach of "bunker busters"
Boeing’s 30,000-pound Massive Ordnance Penetrator (MOP), an ultra-large bunker buster for use on underground targets, with Iran routinely mentioned as its most likely intended destination, is a key element in the implicit U.S. threat to use force as a last report against Iran’s nuclear ambitions. Would that weapon, delivered in a gouging combination with other precision-guided munitions, pulverize enough rock to reach down and destroy the uranium enrichment chamber sunk deep in a mountain at Fordow, Iran’s best sheltered nuclear site?
While the chances of such a strike succeeding are slim, they are not so slim as to enable Tehran to rule out the possibility of one being attempted, according to defense experts contacted by Reuters. A “second best” result might be merely to block the plant’s surface entrances, securing its temporary closure, some said.
One U.S. official, speaking to Reuters on condition of anonymity, described an attack on the underground site, about 160 km (100 miles) south of Tehran near the Iranian holy city of Qom, as “hard but not impossible.” The vulnerability of the chamber at Fordow, believed buried up to 80 meters (260 feet) deep on a former missile base controlled by the elite Revolutionary Guards Corps, came into sharper focus on Monday when the United Nations nuclear watchdog confirmed that Iran had started enriching uranium at the site.
Critics of Iran’s nuclear program tend to agree that military action against Iran’s nuclear work would be their last and worst option. Not only would this risk civilian casualties, but Iran would seek to retaliate against Western targets in the region, raising the risk of a regional war and risking global economic turmoil.
Experts differ on the extent of the challenge at Fordow, but all agree it presents greater complexity than Iran’s other underground site at Natanz, 230 km (140 miles) south of Tehran where enrichment happens in a chamber estimated to be 20 meters underground, or less than a third of Fordow’s presumed depth.
Mark Fitzpatrick, an Iran expert at London’s International Institute for Strategic Studies, said that Natanz was buried under several layers of dirt and concrete but it was “nevertheless possible to damage it with precision bombing with one sortie to create a crater and second sortie to burst through the bottom of the crater to the facility below.” But the chamber at Fordow might be “impenetrable”, he said, due to its presumed depth.
His doubts were echoed by Robert Henson, Editor of Jane’s Air-Launched Weapons, to Reuters, who said it was likely that Fordow had been built to survive a sustained assault. “We know for a fact - or as near a fact as possible - that you will not be able to stop this program with air strikes. There continues to be a whole lot of hysterical posturing about this. In the meantime, it keeps backing the Iranians into a corner,” he said.
“Given that it (Fordow) is a relatively recent development, it has probably been designed with a lot of attention to protecting it against conventional strikes. You don’t necessarily have to obliterate it, mind. You could block the exits, block access to power, isolate it from life outside, and then you have effectively switched it off.
“But for sure it will have been designed with all of that in mind, and the Iranians will have done the best job they can to make it survivable.”
“With the Natanz facility, as it was being constructed, satellites gave us the information on where and how deep enrichment was to take place. Fordow on the other hand is an unknown. Where is the enrichment chamber? How deep? Which direction does the tunnel go?”
John Cochrane, a defense specialist at the London-based Exclusive Analyst risk consultancy, said he believed the bunker-busting MOP might make a difference. But he suggested Fordow was at the very limit of the bomb’s capacities, which he said could reach down to a maximum of 60 meters.
“Repeated strikes by Tomahawk cruise missiles and MOP might be effective in penetrating the site, if it is not as deep as 80m but, even then, we question whether an attack would have the same level of assurance in terms of damage as strikes on other ‘softer’ sites,” he told Reuters.
“We question from what little we have seen of open source imagery whether it is as deep as 80 meters. If it is, we don’t know for a fact but we think that is probably too deep for any form of air-delivered munitions, including MOP Cyber attack or physical assault by Special Forces may be the only attack options.”
With its nuclear program beset as never before by sanctions, sabotage and assassination, Iran must now make a new addition to its list of concerns: One of the biggest conventional bombs ever built.
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