Call Me Back - with Dan Senor - Part 1: How Iran built its nuclear program - with David Albright

Episode Date: June 27, 2025

Watch Call me Back on YouTube: youtube.com/@CallMeBackPodcastCheck out Ark Media’s other podcasts: For Heaven's Sake: lnk.to/rfGlrA‘What’s Your Number?’: lnk.to/rbGlvMFor sponsorship inquiries, please contact: [e-mail] contact us and sign up for updates visit: arkmedia.org/Ark Media on Instagram: instagram.com/arkmediaorgDan on X: x.com/dansenorDan on Instagram: instagram.com/dansenorTo order Dan Senor & Saul Singer’s book, The Genius of Israel: https://tinyurl.com/bdeyjsdnToday’s Episode (Part I)On Saturday June 21st, the U.S. dropped 14, 30,000 pound bunker-buster bombs on Iran’s three key nuclear sites: Natanz, Esfahan and the infamous Fordo, where 12 of the 14 bombs were dropped.Since the bombing of these three nuclear sites, which President Donald Trump said were “completely and totally obliterated,” there has been some speculation in the press  as to how much damage was actually done.While the world scrambles to figure out what was destroyed, what was damaged, and what was left intact, we are asking what was Iran’s actual nuclear program and how was it built?To help answer those questions, we asked physicist and weapons expert David Albright, who is the President and Founder of the Institute for Science and International Security. David has written numerous books and assessments on nuclear weapons programs and has testified on multiple occasions on nuclear issues before the U.S. Congress. Check out David’s work here: https://www.amazon.com/stores/author/B001HPEB5C/allbooks?ingress=0&visitId=1b1c48b5-d51b-4ce5-b43e-dc94a51aadec–CREDITS:ILAN BENATAR - Producer & EditorMARTIN HUERGO - Sound EditorMARIANGELES BURGOS - Additional EditingMAYA RACKOFF - Operations DirectorGABE SILVERSTEIN - ResearchYUVAL SEMO - Music Composer

You are listening to an Art Media Podcast. What they've done and accelerated in recent months is taking the 20% and running it through these cascades to make at Ford Automix 60%. And what they've effectively done is by making 60%, if they wanted to break out, they could have enough weapon-grade uranium for a bomb in a matter of days and have enough for almost 10 and within a month. And so here you have an example where they're speeding up the timeline to be able to make weapon-grade uranium and getting the benefit because to get to 60% you've exerted 99 percent of the effort.

It's 10 a.m. on Thursday, June 26 in New York City. It's 5 p.m. on Thursday, June 26, where Israelis have gotten through another day without nationwide sirens, as the ceasefire between Israel and Iran seems to hold. On the night of Saturday, June 21st, the U.S. dropped 14 30,000 pound bunker buster bombs on Iran's three key nuclear sites, Natanz, Esfahan, and of course, the infamous Fordow, where 12 of the 14 bombs were dropped. On Monday, Iran responded by launching missiles at an American air base in Qatar. And then later that day, President Trump announced a ceasefire through a post on Truth Social.

Since the American bombing of these three nuclear sites, which President Trump announced a ceasefire through a post on Truth Social. Since the American bombing of these three nuclear sites, which President Trump said were, quote, completely and totally obliterated, close quote, people have been speculating as to how much damage was actually done. But it's important to remember it's just that speculation. Satellite images suggest that the explosions destroyed access routes and tunnels leading to the facilities because they are located deep underground it would take time before any operatives, be that Iranian, American, or Israeli, or IAEA or anyone could reach the materials and machines held in these facilities to assess their conditions

there's also this trending question of the 400 kilograms of enriched uranium, which Iran reportedly hid before the American attack. While the world scrambles to figure out what was destroyed, what was damaged and what was left intact, in fact, just this morning there was a press conference at the Pentagon addressing some of these very specific issues. We think there are some other important questions being left out of the discussion. What is Iran's nuclear program made of and how does or how did it work? What are the steps that need to happen between enriching uranium and creating a nuclear warhead? What does it take for a country to build and facilitate this process? What does it mean if some steps in the process are destroyed

while others remain intact without having access to these kinds of primers, any chatter about how much damage was inflicted is uninformed at best and completely random at worst. So we decided to turn to an actual nuclear physicist who has the answers to these questions at his fingertips. I wouldn't go as far as saying that this would be nuclear physics for dummies, but it is nuclear physics after all, and most of us are not nuclear physicists, at least those of us who host the Call Me Back podcast. So we're calling this everything you always wanted to know about Iran's nuclear program,

but we're afraid to ask. By addressing these topics, we hope to better understand the bigger picture when it comes to Iran's nuclear program, before and after the American and Israeli strikes. We hope this way it can better inform how you think about news that we'll be learning in the weeks and months ahead about what actually happened to its program and whether or not it can be revived. Today's episode is going to be split into two parts. In the first part, we'll focus on Iran's nuclear program before the strikes. In the second part, we'll be joined by Lahav Harkov, who is a reporter for the

Jewish Insider, who is based in Israel. And she's been investigating with Israeli experts and intelligence officials, what we know about the damage done to Iran's nuclear program after the strikes. For now, I'm happy to welcome physicist and weapons expert David Albright. David is the president and founder of the Institute for Science and International Security and has authored several books on nuclear proliferation. He's been widely consulted by government officials from numerous administrations over a number of years, administrations of both parties on these issues. David, thanks so much for joining us.

Good to be here. I want to jump into this because we have a lot to cover. As I said, most of us, or at least your dutiful host, is not a nuclear physicist, although it seems these days, I'm now on X, it seems that everybody's a nuclear physicist. I had no idea that all these people had deep backgrounds in nuclear physics. But assume me and most of our audience are not nuclear physicists. I want to start with the basics. What are the key manufacturing steps and facilities necessary to build a nuclear weapon capability?

Just leave Iran out of it for now. Just generally speaking, if you're a country, you're a government that wants to build a nuclear weapons program or capability, what are the basic steps? nuclear weapons program or capability. What are the basic steps? Well there's two principal areas that have to be mastered. One is the production of nuclear explosive material we call it. And it can either be weapon-grade uranium typically or plutonium. And that's usually referred to as kind of as the long pole in the tent of making a nuclear weapon. But there's other steps as well. One set of steps has to do with making the weapon itself.

It involves, let's say if we're just talking about implosion weapons, it involves high explosives, initiators of those high explosives that have to go off simultaneously. It involves making the nuclear explosive material into a metal core. And then you have to have something called a neutron initiator to start the chain reaction at the right moment. And so that set is separate, really, from making the fissile material or the weapon-grade uranium.

Then the third stage is have a delivery system that we've sort of left the arrow where you can just drops a nuclear weapon by a bomber because the countries that are typically seeking them don't have the capabilities to get through their enemies air defenses. And so they have to build a warhead, nuclear warhead that'll fit on a ballistic missile. And that's another challenging set of steps. Let's say if I want to just focus on weapon-grade uranium,

you have to start with uranium. And you would love it if uranium could be used directly to nuclear weapon. But unfortunately, what you're trying to use in the uranium is an isotope uranium 235. And that isotope is just less than 1% of uranium content, almost the rest is uranium 238. And so you have to have a process to take the uranium from the ground and then get it into a form that you can then subject to what's called a uranium enrichment process. The most popular one for nuclear weapons programs is called the gas centrifuge, which is a rapidly spinning tube. And it spins at extremely high velocity, essentially the speed of a bullet from a low-quality handgun, it's difficult to make.

But before it gets to the centrifuge, you're going to have to convert it at a facility, and this is a facility that's not particularly easy to make, but it takes a uranium from the mine, which is in an oxide form, and then turns it into a chemical compound called uranium hexafluoride. And that's a material that if it's under low pressure will turn into a gas. At room temperature and normal pressures it's actually a solid. And the problem is it's very difficult to get uranium to combine with an element to turn into a gas, and it's a gas that goes into a gas centrifuge.

And that facility to do this conversion can take years to build for a country, a developing country or a country like Iran. And then once it has that kind of material, it can then feed it into a gas centrifuge, as we call it. It's called the feed material. And then it's enriched. Now, you want to enrich it in the sense

that you're increasing the fraction of uranium-235 in it. And so one of the first steps that has to be mastered is to just get it up to about 5% uranium-235. And that takes a tremendous amount of enrichment effort. If you think about weapon-grade uranium, that's 90% uranium-235, that when you're at the 5% enrichment stage, you're actually 70% of the way in terms of enrichment output or effort to having the 90% enriched. And so a program that wants to build a bomb

is gonna have to build a lot of centrifuges just to make this what we call low enriched uranium or less than 5% enriched uranium. Can I just ask about that? Because I'm often confused about that. Why these intervals five to I always hear 5% and then I hear 60% and then we hear 90%. Why are those the set intervals? Some of it's arbitrary. I mean, a lot of these designs were developed by the Pakistani nuclear weapons program and they were using European centrifuges that they essentially stole the designs for. And you could theoretically enrich from natural uranium to weapon-grade uranium, but there's

another property of centrifuges, particularly for programs that aren't like the United States programs, is they can break easily. And they can break in a sense that they can actually take out their neighbors in the pipework. And I probably should mention that these centrifuges are connected together by pipes. And they have to have a point where you put in the gas, the feed gas, and then you have to have places where you take out the product and then the waste. What's called the tails. So you have a set of centrifuges connected by pipes.

And if one of those breaks, it can send a pressure spike down the pipe work and destroy all the centrifuges in that particular cascade of or collection of centrifuges. And so typically what you have is programs that develop cascades that are relatively small that in the scheme of getting to weapon-grade uranium can only enrich stepwise. And so you create a cascade that goes from natural to 5%. Turns out the same cascade, another one, same design, can go from 5% to 20%. And in a sense, it's the best it can do with the kind of centrifuges that are in place

and still have a cascade that if you lose it, it's not devastating. If you only had one cascade going from natural to weapon grade uranium and some of them break, it can take out essentially your entire enrichment plant. And so what you do is have 70% of your centrifuges are making four and a half, 5% enriched uranium. And then the 30% that remain mostly are dedicated to going from 5% to 20%.

And then a much smaller number go from 20% to 60%. And then a very tiny number go from 60% to 90%. Because the way this works, it's not linear. So going from 60% to 90% takes 1% of the total enrichment effort of going from natural up to weapon grade uranium. OK, so the facility, just I want to better understand, so the facility one needs to do that, just describe it. What is the place that this happens?

In very simple terms, just assume like I've never walked into one of these facilities. So you're describing to me, if I walked into one of these facilities. So you're describing to me, you know, if I walked into one of these facilities, I would see what? The uranium hexaforide comes in in a canister. If it's natural, it could weigh up to 13 tons. And it is put into essentially an oven. And it's a solid in that container.

And then it's heated. And then as it's heated, it turns into a gas. And then that gas enters a cascade. And the cascades would be essentially just a big hall. Typically, it's going to be two stories high and fairly, depending on the size of your program, fairly substantial. But it's very common to have in these smaller programs to have a hall that's 60 meters by 100 meters.

And it can hold about 6,000 of these centrifuges. And that's sufficient to make maybe 100 kilograms of weapon-grade uranium a year, assuming it's a medium-quality centrifuge. And so what you see essentially is a big hall. And one of the challenges for intelligence agencies is a centrifuge requires almost no electricity. I mean, it's really an amazing device.

And it has almost zero radioactive emissions. And so you can't detect it from a distance. And also, it literally looks like a warehouse building. It's very hard to detect it with overhead imagery. So it's always been a challenge to try to find these things. I mean, there's other ways to do it, but some have been missed for years, in fact. So in terms of the size of a place, to do what you're describing, how much physical

space does the country need? It's really proportional to how many centrifuges you want. Some facilities are designed to hold 100,000, and they're pretty big buildings. And so if you want 6,000, you can sort of estimate the size, 100 meters by 60 is pretty good size for that. And then on the other side, once you've gone through the enrichment process and you have enriched uranium you want to 5% or 20%, and then there's a fraction of uranium that's depleted in uranium-235. And that's called the tails.

And so they come out and they typically in the more traditional plants, you want to put it back into a tank. And so you'd have some set of equipment that would basically take the gas and turn it into a solid inside a canister. And so in the old programs, literally if you had these four steps, you would take the canister of 5% enriched uranium and move it physically to an oven, technically it's called an autoclave, that then would heat it and inject the gas into the cascade to go from 5% to 20%. Okay, so we've all been hearing about Natanz, Isfahan, and Fordow.

So you've explained to me what the necessary manufacturing facilities are. Now can you describe the facilities that we associate with the names of these cities in Iran, Natanz, Isfahan, and Fordow? We just say matter of fact, there's Fordow, there's Isfahan. But what are these facilities in each of these places and what were they doing? I mentioned the process of taking uranium from mine and turning it into uranium hexafluoride. That was done at Asfahan. And then there's the process, once you're

done with the enrichment, then you want to turn it into some usable form. If it's military, it's weapon-grade uranium metal. And so Asfahan is a critical part of this process. And it's often left out in the discussion of Iran. The enrichment plants in Iran have really come out of two tracks. The Natanz facility was developed by the Iran's Atomic Energy Organization as a plant that would have 50,000 centrifuges in two buried boxes,

essentially 25 feet underground, that would be making up to 5% enriched uranium. And that 5% was envisioned to be used to make fuel and also to supply the Fordow plant with 5% enriched uranium, which would then take it up to weapon-grade uranium. And so the Fordow plant was originally part of the nuclear weapons program that's codenamed the Iman Plan that reached its peak in the early 2000s. It's a huge way toward weapon-grade uranium and that they would supply a certain amount to the Al Gidear project, which would then go up to weapon-grade uranium. After the Iman Plan closed, and they had mostly finished their job, but they didn't have any

weapon-grade uranium or the ability to make weapon-grade uranium. So actually, the Al Ghadir project continued after the Amman plant formally closed and eventually was discovered by Western intelligence probably in around 2008. And then when caught, Iran had a history of, okay, we'll call it civil and we'll let IA inspectors come in. And they did. And I talked to some of the

centrifuge people that went in and they came out convinced that it was still designed to make weapon grade uranium. A team of inspectors went back later and the things that had indicated that it was weapon grade uranium was how the pipes were organized, the kind of a measuring equipment, the size of the fee stations, had all been changed. So all this piping is suddenly removed, and it's very elaborate piping in a gas centrifuge plant. And the Harynians said, well, we needed to paint the ceiling.

And so it was pretty clear when caught, they then converted to making low enriched uranium. And it took them a long time to figure out the story to tell the energy agency, because they have to declare what exactly they're gonna do in the plan. They went through three, four iterations to try to settle down, and eventually started to make 20% enriched uranium there.

So in a sense, they were implementing the original Ahmad plan, which is, okay, four down will go from the 5% up. And since 2021, they've also been making 60%. And they've been fairly innovative going, learning to jump a step, go from 5% to 60%. Since December, they've been concentrated on creating large amounts of 60%. So they've been going from 20 to 60 and now they have a sizable stock of 60%,

which is almost virtually hairs breath away from what the grade uranium. Okay. So according to the IAEA, the international atomic energy agency, as of last week, at least Iran had amassed what they are estimating as 408.6, to be precise, 408.6 kilograms of uranium enriched to 60%. Now what do most people fail to understand about enriching uranium? You went through this a little bit, but when you go from zero to five and then 10 to 50, like can you hit that one more time?

What that actually means at a very practical level? What they've done and accelerated in recent months is taking the 20% and running it through these cascades to make, at Ford, how to make 60%. And what they've effectively done is by making 60%, if they wanted to break out, they could have enough weapon grade uranium for a bomb in a matter of days and have enough for almost 10

within a month. And so here you have an example where they're speeding up the timeline to be able to make weapon-grade uranium and getting the benefit because to get to 60 percent, you've exerted 99 percent of the effort. Okay, so it's safe to say from 60% to 90% is the shortest step. So if Iran can just get a critical mass of enriched uranium to 60%, then that's where people say when Iran is days away or Iran was days away from having a nuclear weapons capability, it was that it had gotten some amount of enriched uranium to 60% and then it was a matter of when they dashed from 60 percent to 90 percent.

But whenever they chose to do that, it's just that. It's a dash. It's not a marathon. It's a very short period of time. That's right. And that's been part of their strategy is across the board on nuclear weapons, shorten the timeframes to be able to build the bomb. And you can look at the nuclear weaponization program in the same way and see that they're

reactivating activities in the last year and a half to work on high explosives, the initiation of high explosives, looking again at the theoretical models, and so probably working on the neutron initiator that would start to chain reaction. And all these things are being done. And it's a bomb program. on initiator that would start the chain reaction. And all these things were being done. And it's a bomb program. You need to take the weapon-grade uranium and send it off to a facility to convert it

into the form used in a nuclear weapon of the type Ron's design, and that's metal. And so you have to have a process to convert the uranium hexafluoride, the weapon-grade uranium hexafluoride, into weapon grade uranium metal. And Iran had part of that process at Esfahan.

So that was something at Esfahan that attracted a lot of attention. And if Iran was legitimately just building this program for civilian needs, right, for medical isotopes or whatever, I mean, just non-military purposes. At what level would they need to enrich their uranium? At what percent? Almost all of it would be less than 5%. So it's really hard to argue that this is anything but an effort to be prepared to more quickly build nuclear weapons. I don't want to get bogged down on what Iran's explanations are for what they've done, but this is a key point.

What has been their explanation when they've been caught enriching at much higher levels than five percent when they say they only want the program for civilian purposes? Like, I don't want to get into the merits of what there's I just want to understand what do they actually say? Well, they say they'll, you know, they can use it to better produce medical isotopes. There is a can use highly rich geranium, anything greater than 20% and, and make certain types of medical isotopes that are very important. But you can also make it in 20%. In the end, the excuse was, they didn't even

take the excuse seriously. They just said, okay, 2% has been converted into some civilian like form. And but the rest stays in uranium hexafluoride form that's suitable for further enrichment. Okay. I want to take just a step back and if we take all the necessary steps for building a nuclear weapon from building out the facilities and the assembly line, if you will, to getting the raw materials to enriching the uranium at the various levels,

the various thresholds. So you went through to processing it into a solid, to engineering the weapon, to placing it on the missile. If all of that was boiled down to a progress bar that goes from zero to 100, how far along was Iran? I would have two progress bars. I would separate making it a non-missile deliverable nuclear weapon, which could be used for testing

or secretly placing in another country, while placing it in Israel or the United States. It was a pointed comment. Basically, he was saying, don't think we need missiles or planes to deliver a nuclear weapon into your country's US and Israel. And so we would traditionally think that

as sort of a terrorist kind of delivery system, but it was one of the founders of the nuclear weapons program saying that on a TV show So it was a chilling message But if you take a progress bar on that particular non missile deliverable weapon They were about 90% done Wow if you want to then say okay Well now let's broaden the bar to missile delivery I would guess they were 80% done on having a missile deliverable, maybe 70% done. They had some significant challenges to do.

But one of the things that alarmed people recently was that people who work on the weapon itself, they're the nuclear people, they're huddling together, highly secret programs, and it's a testament to Israeli intelligence that we know what we know. But they had reached the point where they wanted to start meeting with the missile people again. They had done that during the Amman plan. Israel learned that they were going to set up a meeting between the nuclear weaponeers

in a sense and the people who would be helping make the reentry vehicle for the warhead for missile delivery. That's what we hear when we hear that the weapons group, that's the weapons group that's actually taking this and turning into a weapon. And the weapons group is starting to meet again. To meet, well, it's the people making this kind of the nuclear warhead itself, and they have to fit it into a reentry vehicle. And it has to be a certain size. But more importantly, it has to be very rugged and be able to withstand launch,

work in a highly reliable manner and fire at the right moment. And it's a tricky business because if it fires one mile above the surface, it's going to make a bright light and cause some damage, but not as much as if it fires at the targeted range of, let's say, a quarter mile. And so you have to do many steps separate from building the nuclear weapon itself to put in as a warhead on a ballistic missile. And that meeting between the weapon ears that I would call nuclear weapon ears and the missile people was going to happen. And so at that point,

you have a pretty active nuclear weapons program. It's still no official decision by the supreme leader, but it's reaching a point where it's kind of hard to tell. OK, before we wrap, David, with this part of the conversation, just one other question. When there was this talk, you said this now deceased nuclear scientist who said that they could take the components and they don't need a warhead, they don't need a missile, they could activate it in some kind of terrorist like act. This is, I guess, what determined the user. But we heard a quote unquote dirty bomb. It's not a dirty bomb, it's a nuclear weapon. It's a nuclear weapon, I guess, delivered.

It's a bomb that's a half a meter across, so it's not even that large. And how reliable, if you're the one who wants to activate it, how reliable is that use of the nuclear materials? Well, that's, I think, the 10% in the progress line you gave, which incidentally, before the war, our assessment was six months to do that. This is all separate from the weapon-grade uranium, although it includes the conversion of the weapon-grade uranium enriched to hexafluoride into metal. But it was six months in shortening. For some, it was three months, but it was six months and shortening some for some it was three months, but it was getting dangerously short to make this non missile deliverable warhead. And so for me, the 10%

is really about getting the thing to work tested as a system. And you don't need to blow it off underground and have a nuclear explosion, but you need to test it as a complete system and make sure all the parts function properly. And it's, it goes under the rubric of cold tests, where you have a surrogate material in the core substituting for the weapon-grade uranium. It can be natural uranium metal. And then you just fire it and see if everything works, including the neutron initiator,

which creates a spurt of neutrons. And so that's the 10% that we didn't think they'd finished. And that's why they needed, we didn't think they'd finished and that's why they needed, we would estimate needed several months. Okay. Now that we have some sort of grip on Iran's nuclear program, I want to talk about what remains of it following the Israeli attacks and of course the deployment of the US bunker buster bombs by the B-2 bombers.

So that'll be in part two of this conversation. you