Iranian Nukes - Plain Language Repost

This spring I took a look at the Iranian nuclear options.

The summary version is that I think the focus on uranium enrichment is a red herring (unless there is intelligence that says there is a policy decision in Iran to go that route - presumably following Pakistan - except the public evidence is consistent with Iran following all options for nuclear development, HEU, Pu-239 breeding from power reactors, and from natural uranium heavy water reactors).

The way for Iran to get a few nukes quickly, is to reprocess the fuel of the Bushehr-1 reactor, after a "short burn" (to avoid Pu-240 contamination from over exposure).
That would require explicit violation of IAEA rules, and a breech with the Russians, who have been dragging their feet on supplying the fuel for Bushehr.

Well, no more. Russia is shipping the fuel by March 2007 for operation by autumn.
If the Iranians broke ranks, and have a reprocessing cycle in place, then they could extract Pu-239 starting early 2008.
Some Big IFs in there.

In a previous post I did a somewhat cryptic discourse on the physics options for Iran to make nuclear bombs, and why I was concerned about the near future.

There is more discussion at Cosmic Variance and Nuclear Mangos, but I wanted to straighten and simplify what I think the key immediate issue is, partly for my own line of thought.

Iran is a signatory of the Non-Proliferation Treaty.
As such it is entitled to develop civilian nuclear power, and to receive assistance from the nuclear powers to do so.
The assistance may include proliferation safeguards and IAEA supervision.

Iran has had a nuclear power program for over 30 years dating back to the Shah.
They bought a large (1 GigaWatt) fission reactor from the Russians (current contractor), Bushehr-1. On the gulf coast, it is in a complex that is intended to host more reactors. The Iraqis bombed it in 1984 (several times 1985-88 according to Wiki) I believe; progress on reconstruction was intermittent and it is not yet operational. It is complete, or essentially complete, in construction. What is missing is the fuel - several tons of moderately enriched uranium. The Russians have repeatedly posponed delivery of the fuel.
The Iranians are angry over this, there are huge cost overruns and excessive delays.
The reactor is due to go online, delivering power to the grid in october this year.
To do so, the Russians have either already sent the fuel to Iran, or must to so in the very near future.
The Iranians will need to do some off-line operation to shake down the reactor before it goes online.
That means this summer.

It is actually sensible for Iran to have a nuclear power program. They are large, need to supply a lot of electricity to their grid, and long term they are better off having substantial baseline nuclear power and sell the oil and gas instead of burning it to produce electricity.

Both the USA and Iranian internal political situations are such that each assumes the other is operating in bad faith.
Not just "normal bad faith", both assume the other intends a worst possible outcome.
Internal political situation in both countries is unusually volatile and there may be play in exacerbating external tensions for internal political leverage.

Iran has reasons to want nuclear weapons in a hurry, looking at their situation from the outside with a neutral perspective.
They are surrounded by potentially hostile powers, several of which are nuclear powers, and have recently fought a major war in which WMDs were used against them when the opponent was faltering.
The "axis-of-evil" speech and subsequent events suggest that bilateral deterrence is prudent for the axis-of-evil countries.
Contrast the treatment of North Korea with Iraq.

Over the last 15-20 years, Iran has setup and tested everything they need to have a completely independent nuclear fuel cycle. They can mine uranium. They have tested plutonium production and extraction and done lab scale experiments on plutonium chemistry and matierals science. They have experimented with uranium enrichment and have in construction facilities to do their own enrichment, which can be done to moderate levels for fuel for powers, or continued to highly enriched levels for bomb construction. What they have not apparently done yet is set up production of their own nuclear materials on large scale. They are brushing very close to their treaty committments under NPT but have not made a blatant open breach with their treaty agreements. They're pushing it.

So: how can you get nukes in a hurry.

There are three kinds of nuclear weapons:
Fission bombs made with highly enriched uranium [HEU] (>> 80% of the U-235 isotope, natural uranium is 99+% U-238 isotope) - these are moderate yield ( ~ ten kilotons TNT equivalent); this is what was dropped on Hiroshima. They are very simple to make if you have the HEU. They are heavy, and hard to put on missiles.

Fission bombs made from plutonium, specifically Pu-239 (used on Nagasaki). These have low-moderate yield (kiloton to over 100 kiloton). These are harder to engineer, and a new design is thought to require testing if you want to be sure they will work. They can also be "boosted" to somewhat higher yields, testing would probably be required for that. They can be made light and compact, with some practise.

Thermonuclear weapons (fusion or H-bombs). These use fission bombs (Pu-239 type) as triggers to start much more energetic (fusion) nuclear reactions. They are hard to do, and probably not an issue in the foreseeable future. They can be made to have very, very high explosive yield (tens of megatons - thousand times more powerful than fission bombs).

So, realistically, to build nuclear weapons, you need either pure plutonium-239, or highly enriched uranium.
Countries that have become nuclear powers have used both techniques. The associated engineering is not trivial, but it is solved, fairly well known and just not that intrinsically hard. It is literally 1940s-50s technology.
Most of the media focus is on Iran's announcements on uranium enrichment, in part because of the implications for the long term, in part because it is being played up by analysts and pundits, and in part because it is how Pakistan got their bomb, and they aided Iran covertly.

To make Pu-239 you need a working nuclear reactor (a big one is better, higher throughput).
You put unenriched or depleted uranium, rich in U-238 isotope in the reactor (either in the core, or around it in a "blanket").
If you keep it in a short time (~ 3-4 months or less) neutrons from U-235 fission "breed" U-238 into Pu-239.
If you keep the uranium in too long you get Pu-240 and Pu-241 which "poison" explosive fission, the bombs either explore incompletely with low yield, or possibly detonate spontaneously without a trigger.
For efficient power production you want the fuel in the reactor for a long time, and separating Pu-239 from Pu-240 is very hard. Separating Pu-239 from U-238 is quite easy, it is chemistry. It can be done quickly if you are willing to take moderate risks.

So, how could Iran get nuclear weapons?

Well, simplest way is to buy them.
There are at least three potential suppliers.
This has some problems - you don't know if they sold you a dud unless you test; if you test you better have bought several. which is harder than one, and then the game is also up. World will know, and they will know who sold it to you.
Intelligence agencies ought to be able to isotopically single out where any nuke came from, and I don't think the Iranians know enough to successfully "spike" any test to mask the production signature.
You can't really deter with bought nukes, just retaliate.

The Big Worry in the media is the HEU bomb, since the Iranians are setting up enrichment.
Now, a moderately wealthy nation with ~ 100 physicists (10-20 good, rest competent); few hundred chemists and engineers (competent) and couple of thousand honest construction workers and machine tool operators, and with large electrical power supply, can go from zero to full HEU production, enough to make many kilograms per year, in about 3 years.
IF the politicians don't micromanage the process, and the technical people are motivated and honest.
With modern management techniques, it would probably take 10 years.
An enrichment facility allows a NPT signatory to cut loose, they don't need a nuclear power to supply part of the fuel loop, they don't have to honour any external reprocessing safeguards. They can either have their own completely internal power cycle, build bombs, or both.
Iran is probably 5-10 years from doing this. It will not get them a bomb this year.
They can do it somewhat quicker if they take commercial moderately enriched uranium and enrich that rather than raw ore.
So, they could divert civilian fuel to their own enrichment plant to make HEU quickly. They could hide or obfuscate the process by mixing unenriched uranium in to make up for the missing bit, leaving less enriched uranium. The reactor should still work, but less efficiently. Risky but they might be able to obfuscate long enough to finish enrichment to HEU levels.

You can make nuclear reactors that work on natural (unenriched) uranium.
These are somewhat harder to build, the simplest most robust design use "heavy water".
Iran has a heavy water production facility.
IF they built a moderate power HIDDEN nuclear reactor and it went operational more than a year ago, they could have made enough plutonium for a bomb or two, and possibly be producing one-to-few per year.
It seems unlikely they could have done this and gone operational without USA or Israel noticing.

In my opinion Iran has a window to make several Pu-239 bombs quickly right around now, at a considerable diplomatic cost.
The way they can do this is to get the fuel for Busherh-1 reactor, and after the core is turned on, shut the reactor down early and pull out the partially burned fuel and chemically extract the Pu-239.
This would require an open and blatant violation of IAEA safeguards, a breech of the NPT, and possibly the expulsion of the Russian engineers at the reactor (or their detention or passive acquiescence). It would certainly be noticed.
BUT, if everything else is already in place, the Iranians could then very quickly extract Pu-239 from the partially burned fuel. Enough for something like 3-10 bombs, depending on their efficiency and design capabilities.
Their window to this is the next 3-9 months. If the fuel is in too long it is useless until the next refueling cycle.
IF the Russians have or will soon deliver the fuel for Bushehr-1.
I would be most curious to know if anyone else know for sure whether it has been shipped to Iran.

NB: the timeline above is predicated on Russian fuel delivery, now scheduled for spring 2007. A year later than previously scheduled.

The Iranians know this.
The Israelis know this.
Probably some people in Washington DC know this. Certainly people in some other particular locations in the US know this.

IF you fear Iranian intentions, and assume worst case scenarios, this scenario rationalises a pre-emptive strike, before the Iranians have the opportunity to do a fast burn at Bushehr-1.
Since you might as well be hung for a sheep as a lamb, any strike then escalates to a full pre-emptive knock-out against all identified Iranian nuclear facilities.

The political and economic consequences would be very bad. Potentially catastrophic.
Quite frankly, I think the US internal reaction would be a severe schism, while the Iranians would unify.
US political pundits seem to think the opposite, that the Iranians would schism and overthrow the current government while the US would consolidate around the government.

This is why I am seriously concerned that the US may launch a pre-emptive air strike on Iran in the near future.

Oh, I get the sense that the DC "beltway pundits" have become accustomed to thinking of airstrikes as "no big deal". With Iraq from 1991-2003 having repeated small airstrikes, and the bombings in the Balkans in the mid-90s, there seems to be some perception that Iran could just sock it up and accept that the US might choose to send a few squadrons of heavy bombers over. No biggie, grouch about it for a few weeks maybe, some transient market panic, what the call a trading opportunity in Congressional staff offices. (Hm, be interesting to see if oil and gold futures are trading from laptops in DC at anomalous levels).
It is a big deal. Iran is kinda prickly about the whole thing, and nations that are on the receiving end of pre-emptive large air strikes traditionally count it as Acts of War. Ye Olde All Out War, not these late twen-cen half-ass wars.

It would not be fun at all.