Reliable Security Information


On Sunday, March 1, the U.S. chief military and civilian defense leaders spoke out on Iran's atomic weapons program. Assuming both had full access to US intelligence on this program, it is surprising that they voiced two different views. Or is it? For parochial reasons, these two factions often have held different and opposing view points on crucial national security issues.

On one hand, Joint Chiefs of Staff Chairman Michael Mullen stated that Iran now has enough fissile material (very highly enriched uranium) for a bomb. On the other hand, Defense Secretary Robert Gates claimed, "They are not close to a stockpile, they are not close to a weapon at this point." Who's right and who's wrong on this highly important matter? The answer is neither. Both of them spoke politically, not technically, in making such unfounded remarks.

After the war, in quickly became apparent at Los Alamos that very high-grade plutonium (Pu-239) was far superior to highly enriched uranium (U-235) for making implosion warheads of the type that devastated Nagasaki. The Nagasaki warhead used six kilograms of Pu-239, which was detonated by a sphere of high explosives weighing about 5000 pounds and produced a yield of about 20 kilotons. By the early 1950s, implosion technology had been refined to a degree where a much smaller warhead one-tenth the weight and a much smaller plutonium investment could produce a yield of several kilotons, which would devastate an urban area roughly two-thirds that of that Nagasaki bomb, using significantly less plutonium. But that was a half-century or so ago. In terms of today's technology, most of it in the open market, it would be dangerous folly to assume that a nation such as Iran would not be capable of building warheads providing their ballistic missiles of intercontinental ranges and capable of inflicting horrendous damage on the United States.

Now all this brings up the question: Why is the US placing sole emphasis on Iranian production of highly enriched uranium to make atomic bombs? The answer is quite simple: Our nuclear weapons intelligence, form the very beginning, has been so poor and so politically driven, that it never has been possible for the US government to give honest and realistic appraisals of the nuclear threat against ourselves and our allies.

Now I don't pretend to know what Iran's nuclear weapon program is all about. But I do know what I would have been doing were I to have been in charge from the beginning. What I would have done was to use my centrifuges to make only enriched uranium, less than 10% U-235, and use this material to make very small reactors whose primary mission is not to make power, but rather to make so-called "dirty plutonium," through the neutron absorption of natural uranium, which is mainly U-238, and is very cheap. By dirty plutonium what I'm referring to is plutonium having an undesirable amount of Pu-240, which undergoes spontaneous fission, and if you're an old fashioned weapons designer ordered by the US military to produced extremely reliable warheads (90%+ reliable), the amount of this element should be minimized to the greatest practical extent. Otherwise the efficiency of the warhead may be reduced significantly. At the beginning, when we had a dearth of "weapon-grade" plutonium, this was understandable. Today, however, for a country wanting to get into the nuclear weapons business, this would be stupid. For going by the "dirty" route, atomic weapons could be made far more cheaply and abundantly and a much larger stockpile of warheads could be produced far more quickly and cheaply. The US military way, however precludes such logic; but perhaps a relatively poor and backward country such as Iran may have grasped this logic, which long has been in the public domain.

To be sure, dirty plutonium warheads are not as efficient as the clean ones, but by no means are they unacceptably inefficient. So, instead of what is 20 kilotons, the yield is only 10 kilotons or 5 kilotons, or even less compared to the Nagasaki 20 kilotons. By no means does that imply that the destructive urban blast area goes down by a factor of two or four. Far from it; the way the destructive area varies with the warhead yield is by the two-thirds power. If the area of destruction were reduced by one half or even two-thirds, this might be of precious little solace to the cities inhabitants.

Would Iran have embarked on such a development years ago, who knows but now they could have amassed a very sizable warhead stockpile. Five, ten, twenty? Who knows? We don't. Were such a program to have been mounted in secrecy, it could be very difficult for us to have detected and monitored it. And even if we did, what could we do about it? (Maybe a reporter should ask such a question of President Obama at a press conference.) Who knows, but to get a clue we might take the case of North Korea where years and years of efforts to curb or stop the nuclear weapons program has come to naught - and the futile game goes on and on. Perhaps we should stop fretting over the matter and let Iran alone do its own nuclear thing and try to get along with them better. After all, they are a sovereign nation and under no non-nuclear proliferation restrictions to do their own thing for their own reasons. Who are we to decide for them, even to the point of going to war with them? Haven't we already had enough with our Mid-East meddling? Will we ever learn to respect the advice of our Founding Fathers?

Comments (3)


The following is entirely based on publicly available information...

The reason a rogue state would use HEU vs Pu-239 is design. Plutonium requires an implosion design, while HEU could be used for either gun-type or implosion warheads. The engineering for gun-type warheads is simple. Which is why the US never even bothered to test that design before using it against Japan - only the implosion device was tested at Trinity.

HEU is easy to make without the need for reactors, safer to handle, and simpler to weaponize. Compared to 1st generation implosion warheads, a HEU gun-type design is also much lighter and less bulky. All of which are attractive features for a country in a hurry to get a functional weapon. The disadvanges of HEU would not deter a rogue state very much.

Mark Gubrud:

Sam Cohen should know if, in fact, small reactors, similar perhaps to
the 5 MW research reactor in Tehran, could be used to produce dirty
plutonium which could be used in implosion bombs, with low yield but
plenty to cook a small city. However, if Iran had been attempting do
this over the past decade or more, as he suggests would have been
possible, almost certainly we would know about it or have heard of
some evidence or rumors of such a program by now. The eyes of several
large intelligence collection organizations as well as countless minor
ones ( are watching everything nuclear that there
is any evidence suggesting Iran may have done. What Iran has done,
more or less openly since 2003, is quite a substantial effort to
develop uranium enrichment as a foundation for both a nuclear fuel
cycle and a weapons capability. They are also building an apparent
plutonium production reactor; at the same time, they are building
their technical infrastructure to support these ambitious plans.
There is no evidence of any very small reactors making dirty
plutonium, although this would make a good scenario for a commando
raid video game.


Remember the theory that the North Korean nuke test actually fizzled, given the low yield? Perhaps they used dirty plutonium in their device, hence, the lower yield. The North Korean test may have not been a fizzle at all, but merely the North Koreans following the path proposed in this blog. The plutonium for the test undoubtedly came from the fuel rods that they had recycled.

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