What will Iran do with a bomb?

The picture to the left is the "Little Boy Bomb" that was dropped on Hiroshima.

The previous post described this as a uranium bomb. What that means is that it contains two pieces of the uranium isotope with a mass number of 235 that are shot together to make an explosive nuclear reaction.

Uranium is an atom with 92 protons in its nucleus, but with different numbers of neutrons. The mass number is the sum of the protons and neutrons. Uranium-235 makes up less than 1% of the atoms of naturally occurring uranium. So to make a bomb, you need to separate the U-235 from the rest of the uranium, which is mostly heavier U-238, assemble two smaller pieces in a way so that when they are rapidly brought together, they explode. This is not difficult for a country like Iran, which has a huge oil revenues to fund this work.

Separating the uranium is the difficult part of this work, since chemical separations don't work. There are two ways to separate the isotopes. One is to make charged atoms called ions, and send them at a high speed through a strong magnetic field. The magnetic field will cause the flight path of the ions to curve, with heavier ions going in a less curved path. Once the ions hit the a device called a "collector", which is placed at different distances along the flight paths in the vessel, they lose their charge and are converted back to atoms. The collector will accumulate U-235 atoms. When the U-235 concentration in uranium becomes higher than the normal concentration, the uranium is called "Enriched Uranium". When the U-235 concentration is lower than natural uranium, it is called "Depleted Uranium."

The instrument used to enrich uranium using magnetic fields is called a "Calutron". This is an expensive, but not technologically difficult method to produce bomb grade enriched uranium, and was the technique used to make the U-235 that went into the Little Boy Bomb.

Another way to enrich uranium is to react the uranium with fluorine to create uranium hexaflouride, which is a gas at elevated temperatures. This can be spun in a high speed gas centrifuge and gradually enriched, as the lighter U-235 will migrate to the top of the centrifuge tube and the heavier U-238 will migrate th the bottom. This process is repeated many times and requires many expensive centrifuges. This is the technique Iran is using to make bomb grade uranium.

The view that Iran is making enriched uranium for "peaceful purposes" is incredible. There is plenty of lightly enriched uranium available for nuclear power applications, and Iran has only a single nuclear power reactor. They are producing highly enriched uranium for only one possible purpose: to make a bomb. Yesterday, November 20, Iran stated that they were in the process of building 60,000 centrifuges for its nuclear "fuel" needs.

The production of uncontrolled highly enriched uranium with centrifuges is not consistent with nuclear power fuel needs. But it is consistent with making an atomic bomb. A simple atomic bomb will take about 25 kg of highly enriched uranium. Once Iran has this quantity (or any other country that wants to make a bomb), assembling a weapon requires only existing military technology, and is much simpler than making a plutonium bomb.

Iran will build a bomb as soon as they have enough highly enriched uranium. What will they do with it?

Why Iran is scarier than North Korea

The picture is of the mushroom cloud over Nagasaki. This explosion was made with a plutonium based fusion bomb, the same type North Korea tried to explode a few weeks ago, but failed. Even though radioactivity was detected, that was more from the dispersion of the partially fissioned and unfissioned plutonium than from a successful fission bomb, such as the one shown to the right.

In other words, the North Korean bomb was a dud. The reason it failed is that plutonium bombs are hard to make. Plutonium fissions so quickly that conventional explosives have a hard time compressing the plutonium into a small lump for a long enough time to allow a significant amount of the plutonium to split and release all its energy. An improperly built plutonium bomb blows itself apart too soon.

Creating a plutonium bomb requires complicated machining and advanced detonator technology. But plutonium is created in a nuclear reactor, so it was readily available to the North Koreans because they have a reactor, and can use it to convert uranium to plutonium.

In the World War II the U.S. exploded three fission bombs. The first was a test of a plutonium bomb to be sure it would work. The second was the uranium bomb exploded over Hiroshima, and the third was the plutonium bomb over Nagasaki. The uranium bomb was never tested prior to use in combat. Uranium bombs are much easier to manufacture, once you have enough highly enriched uranium. In the case of the Hiroshima bomb, it was just assembled, and tested in combat. The problem is that the highly enriched uranium (HEU) needed to make the bomb is very difficult and expensive to make. It requires special devices such as a calutron, which can only make a small amount at a time, or very high speed centrifuges, which are a complex technology and difficult to keep clandestine. Still, it is what the Iranians are working on. Once they have enough HEU, the rest of the assembly of the bomb is not difficult.

Also, North Korea is surrounded by countries who are highly motivated to keep them from producing a bomb, especially China, who have significant influence on North Korea. Iran has enough oil revenue to be free of influence of its neighbors if its neighbors do not act in a very aggressive manner to keep the bomb out of the hands of the Tehran regime.

North Korea, even with plutonium in hand, is not as great a threat as Iran who are actively enriching uranium.