by Navy Capt (Ret) Pete O’Brien
The talks between the US and Iran appear to have come to nought. The central point of contention appears to be whether the Iranians will continue to enrich uranium; the US position is that Iran must not enrich uranium; Iran’s position is that they will not make weapons but they will keep enriching uranium.
It’s important to remind ourselves that the atomic bomb is 80 years old: this is not new technology. Any reasonable level of expertise – physicists, electrical engineers, mathematicians, etc. – expertise well spelled out in hundreds of histories, could, if given adequate amounts of time and money, build a nuclear weapon; not just a device, but a weapon that will fit under and airplane or on the end of a missile. The really hard part is the material – either highly enriched Uranium (HEU) or Plutonium – which is the material that actually produces the nuclear effects.
In case you’ve forgotten your high school physics, Uranium in nature is predominantly U238 – that is, has an atomic mass of 238, 92 protons and 146 neutrons. In nature, 99% of all Uranium is 238. By itself it is of lesser value (but not useless, heavy water reactors can use U238 to generate power). But, a bit less than 1% (0.71%) of Uranium is U235 – an isotope of Uranium with 3 fewer neutrons in its nucleus. If Uranium is enriched, that is, the amount of U235 is increased, it an be used to generate power – depending on the design, enriched fuel is 3-5% U235, though some reactors use higher concentrations (5-20% U235).
What exactly is enrichment? To “enrich” Uranium is to use any of a number of different means to separate U235 atoms from U238 atoms resulting in, when all is said and done, the desired percentage of U235.
But, to have the energy needed to get an explosion, in a weapon that is smaller than a large tractor-trailer, you need a much higher concentration of U235, what is referred to as highly enriched uranium or HEU. While weapons, such as Little Boy, the bomb dropped on Hiroshima, have been built with 80% enriched Uranium, the normal “target” is above 85% and often, reportedly, in the 90-93% range.
About those weapons: the technology and various designs have been around for decades and with the obvious exception of testing, much of this could be hidden in buildings that would appear as nothing more than office buildings from the outside. But testing – even without the nuclear material, requires special facilities for testing conventional explosives that are part of the initiation process. More importantly, the process of enriching Uranium is very much a “heavy industry” effort and has a large footprint. It not only is difficult to hide, it is simply large and complicated and expensive.
So, what this reduces to is this: HEU is the key to a weapon, and “making” HEU is the hard part.
All that said, does Iran, in fact have a design for a nuclear weapon? As it turns out, per the BBC and several other publications, Iran, North Korea and Libya, among others, were given nuclear weapons designs by the Pakistani nuclear engineer AQ Khan – as early as the 1990s. It’s worth noting that Pakistan was aided in its nuclear weapons development by China, a decision, per Tom Reed, SecAF under Reagan, that China made as early as 1981, and a policy that, per Peter Huessy of the Mitchell Institute, explains some of Beijing’s recent behavior; the current regime in Beijing wasn’t in place when these started, but they aren’t sorry for what they did.
So, we know to a certainty that Iran has weapon designs, and they have missiles. The only question mark is whether they have adequate amounts of HEU. The amount varies based on design and a number of other factors, particularly the level of enrichment. Little Boy used 64 kg (141 lbs) of 80% enriched (average) HEU in a bomb that weighed 9,700lbs. But that was – deliberately – a design that they knew would work. More sophisticated designs since then (to include Fat Man) use substantially less U235 (or plutonium) fuel. The various sources on the internet note that just 12 kg, (27lbs) of 93% enriched HEU will be sufficient to build an atomic bomb. For the purpose of understanding what Iran is capable of building, I’ll just use 20kg or 44.1lbs as a representative weight in HEU (not the total warhead itself), and assume that the weapons design they have will accommodate that mass of U235.
So, we are reduced to this simple question: Does Iran have 44.1 lbs of HEU? If not, how long would it take to make some? If so, exactly how much: enough for 1 weapon or for multiple weapons?
The answer to this is that it’s hard to know with a certainty but the International Atomic Energy Agency (the IAEA), which is charged with monitoring such things, has been conducting inspections of Iran’s facilities for a number of years, and providing public estimates of Iran’s nuclear capabilities. At the same time, there are several facilities that Iran will not allow the IAEA to inspect, 18 facilities at 9 sites, the IAEA web page states. So, what is happening there is not known. In any case, In their latest quarterly report (February 2025) the IAEA estimated that Iran had 274.8 kilograms (607 lbs) of 60% HEU. If refined down to 93% or greater HEU this would yield about 180 kgs (about 400 lbs) of weapons grade HEU, enough for 8-9 weapons. Note, the numbers will be inexact, dependent on the actual level of enrichment of the “60% HEU) and the specifics of their processes. But, 400lbs of 93% HEU is enough for at least 8 weapons. And the other Uranium can also, obviously, be further refined, providing more 93% HEU for weapons over a longer period of time.
How long would that take? That would be entirely dependent on how many centrifuges they are using to enrich the fuel, a number the IAEA does not know to a certainty. It may be weeks, it certainly could be done in months. It is not a function of a year or more.
And there is always the possibility that they started it months ago and already heave the 93% enriched fuel.
In April of 2024 Reuters estimated, based on IAEA findings, that Iran had the capacity to refine 60% HEU to weapons grade (90+% HEU) in a very short period of time: “close to zero, likely a matter of weeks or days.” And to then turn that HEU into a weapon?
Iran has always denied – and continues to deny – it has ever had a weapons development program. Yet, as noted above, there is solid evidence that they were given detailed designed information. Perhaps this is semantics: they never had a weapon design development program because they didn’t need one: they already had a working design, courtesy of AQ Khan. The former director of Iran’s nuclear program, Ali Akbar Salehi, compared making a nuclear weapon to building a car, and said Iran has the ability.
The IAEA noted: “Public statements made in Iran regarding its technical capabilities to produce nuclear weapons only increase the Director General’s concerns about the correctness and completeness of Iran’s safeguards declarations.”
So, it would seem that Iran either already has a nuclear weapon or will soon have one. And quickly after that, more than one. They could in short order have a small arsenal of a half-dozen or more. So, what is the US – and Israel – to do? Is that a risk that Israel, or the rest of the world, can accept? If not, the answer is clear; unpleasant, but clear.
