Saturday, January 9, 2010

Do-it-yourself nuke

John McPhee is such a tease.

He wrote "The Curve of Binding Energy" in 1973, and rogues have yet to build a workable atomic bomb, as far as we know. If so, it is not because McPhee offers too little information.

We learn that a sphere of plutonium the size of a billiard ball would suffice. We're taught how to convert plutonium nitrate and plutonium oxide into more or less pure plutonium -- at home. And then the reader is basically taught how to fabricate a uranium weapon, by a former nuclear weapons designer, Theodore Taylor.

Taylor specialized in miniaturing nuclear weapons, giving us the W-54 warhead employed in the Davy Crockett 155 mm recoilless rifle. The W-54 had a puny yield compared to other nuclear weapons, but just right for a terrorist. The smallest atomic weapon in the U.S. arsenal, as far as the public is concerned, is the spacial atomic demolition munition, which also uses the W-54 device and weighs about 160 pounds.

Small fission devices are also necessary as the triggers for larger hydrogen bombs. Taylor made many "small" designs, but he refuses to disclose them explicitly to McPhee.

The question, if you are pretty much insane, is where to get your hands on the enriched uranium or the purified plutonium?

McPhee wrote in 1973 that the nation's large stockpile of plutonium, which is generated by civilian reactors, is stored casually in poorly guarded structures that could be breached in a few minutes.

What the intruder would have found 30 years ago were heavy casks each containing about 2 pounds of plutonium nitrate. Thieves take a few of them home. Then what?

(Caution: don't even think of trying any part of this, even minus the radioactive stuff. No kidding. )

Here's all they have to to: Add oxalic acid to the plutonium nitrate. Plutonium oxide crystals will precipitate out. Roast these crystals to dry them. Then you buy some hydrofluoric acid and heat it in a quartz crucible. Direct the hydrogen fluoride gas into the crucible and bake at 500 degrees centigrade. What you get is plutonium fluoride. Now take another crucible and line it with magnesium oxide. Add water to make a paste. Add 170 grams of calcium and 50 grams of iodine. Put 500 grams of plutonium fluoride in the crucible, top with argon gas, and close the container.
Heat to 750 degrees C. in an induction furnace. The mixture will react and heat itself up to 1,600 degrees. During the next 10 minutes, the crucible cools down to 800 degrees. Now take the crucible out of the furnace and let it cool to room temperature.

Then, if you've managed to do all of this without setting your basement on fire, blowing yourself up, or otherwise avoiding serious injury or poisoning, pour some nitric acid into the crucible to wash away the iodine flakes and calcium fluoride salt.

What you have left is a small lump of plutonium. Repeat several times, and then figure out how large a sphere you need to construct, and how thick a layer of explosives you must use to wrap around the sphere, and figure out a way to make all of the explosives detonate simultaneously to the plutonium sphere will be compressed to a supercritical mass.

One would require a fairly large, sophisticated laboratory equipped with the right, and not easily obtained chemicals, to carry this out. Configuring the plutonium is also not a trivial problem. The amount you need depends on what you use as a reflector.

You'd pretty much need to be a weapons designer like Taylor to carry this off. Making the plutonium is not the only problem, either. Plutonium metal exposed to humid air rapidly forms oxides and hydrides that crack off and burn spontaneously.

McPhee does not mention this part, perhaps purposely.

Well, wouldn't it be easier to hijack a truck carrying enriched uranium oxide powder on its way to fashioned into reactor fuel pellets?

Sure. Put four and half kilograms (about nine pounds) on a vibrating tray in a laboratory furnace, while heating up hydrofluoric acid in a stoppered flask. Guide the hydrofluoric acid gas through a tube to the furnace and heat up to 500 degrees C. What you end up with is uranium tetrafluoride, which you dump into a crucible with powdered magnesium and potassium chlorate.

Sounds like we're making fireworks.

Put the crucible into a strong steel container and then use something like a toaster coil to heat the mixture to 600 degrees. The uranium tetrafluoride and magnesium ignite, creating uranium metal and magnesium fluoride. Repeat.

McPhee's point seems to be that reckless, motivated lunatics unafraid of death, could conceivably synthesize materials necessary for making an atomic bomb. Many experts consider these scenarios farfetched.

They point out that stealing a bomb would be much simpler. The U.S. military is aware of this, and configures most bombs and other nuclear munitions with protective devices that render the devices unexplodable if tampered with.

McPhee's point about more closely managing and guarding nuclear materials is still valid. The U.S. is spending $250 billion to improve security at nuclear power plants, nuclear waste sites, weapons fabrication plants and munitions storage facilities.

Russia is also attempting to gather and protect fission and fusion weapons scattered across the former Soviet Union. International efforts to curtail proliferation must also be strengthened.

None of this is simple, but if we are frightened by a man who sets his underwear on fire in a passenger plane, we should be terrified at the thought of suicidal maniacs getting their hands on atomic bombs.