This is scary:
A gang arrested by Slovakian police was trafficking uranium so enriched that it could have been used by terrorists in a dirty bomb, it emerged today.
Two Hungarians and a Ukrainian man were arrested as they tried to sell the uranium last night. The consignment had been tracked by police after it came to their attention inside the former Soviet Union.
A total of 481.4 grams of uranium was found and investigators believe it contained 98.6 per cent uranium-235. Uranium is considered weapons-grade if it contains at least 85 per cent uranium-235.
There appears to be a lot of nonsense in the international press about this incident written by journalists who don’t understand a thing about radiation – not to mention a police chief who doesn’t either, given he spoke about a “dirty bomb” when no terrorist group would waste such a valuable commodity on a dirty bomb if the material is as described.
Natural uranium is a mixture of two isotopes – uranium-238, and uranium-235. Natural uranium contains about 99.3% uranium-238, with the balance u-235. Neither sort is particularly radioactive; they are very weak emitters of something called an alpha particle, which is only dangerous if you swallow it or inhale it. And, frankly, there’s probably more risk from the chemical toxicity of even highly enriched uranium (it’s a nasty heavy metal, just like lead) than there is from the radioactivity of the stuff. So it’s a very poor material to use as a dirty bomb, compared to the stuff in some medical devices, which emits much, much larger doses of much more penetrating gamma radiation. Even given the use of those materials, a dirty bomb is not nearly as deadly as you’d assume – but that’s a story for another day.
Why this stuff is scary is its potential use in a nuclear weapon. From natural uranium, there are two ways to get material you can make a nuclear weapon out of. First, you can put the uranium in a nuclear reactor, and convert some of the uranium-238 into plutonium. Secondly, you can use a variety of highly elaborate filtering schemes (uranium enrichment) to filter out the u-238 and get uranium with higher quantities of u-235 in it. Power reactors use about 5% enriched uranium. Modern research reactors generally use uranium with around 20% u-235 content. Anything above that is regarded as bomb-usable, and anything above 80% or so “bomb-grade” or “highly enriched” uranium, or HEU for short.
If you can get your hands on roughly 50 kilograms of HEU, you can almost put together a nuclear weapon in your local welders fabrication shop. It’s pretty simple – you get two bits of uranium and you slam them together at high speed, usually by propelling them together with explosives. No precision engineering required. If you do have a few physics PhDs handy, some high-precision machine tools, and the like, you can get the minimum quantity required down to maybe 12 kilograms, apparently. But the ease with which HEU can be turned into a crude bomb, if you have enough, is what makes it one of the scariest substances on Earth.
The quantities involved here are far lower than that. But, still, it’s a non-trivial quantity of the only material that Al-Queda or any other plausible terrorist group would ever fashion into a bomb. I’ll bet intelligence agencies around the world are currently trying to figure out exactly where the stuff came from, and whether there’s any more of it there.
Anyway, if this report is accurate and the material being smuggled was HEU, it should serve as a warning. As this article in the Bulletin of Atomic Scientists notes, HEU is used in research reactors across the world, and notably in many facilities across Russia. That material should be put in centralized, well guarded storage facilities, and, ultimately, disposed of – a process already happening, but sadly incomplete.