Recently, Russian custom officials prevented 300 Japanese cars from entering the country because they were believed to be irradiated from the Fukishima nuclear power plant disaster. This made me wonder two things: first, can I get an awesome deal on a slightly radioactive FR-S, and second, how does a car actually become radioactive?
We talk about things becoming radioactive all the time, like it was Judiasm and the things would just have to ask a radioactive rabbi three times, take a bunch of classes, and one radioactive Bar Mitzvah later, they're radioactive. It always sounds like this magical force, and I know that's not the case. So, instead of guessing, I contacted Jalopnik's On-Call Physicist, Dr.Stephen Granade, to explain to me the process by which a car becomes radioactive:
How does it happen? In a word, dust.
When the Fukushima power plants melted down and had hydrogen explosions, they released a lot of radioactive material. Some of that was radioactive iodine and cesium, which started out as a gas before condensing on dust particles or binding to water and falling to Earth. The iodine is essentially all gone, as it has a half-life (the time for 1/2 of it to decay away) of 8 days, but the cesium has a half-life of 2 years (for cesium 134) or 30 years (for cesium 137).
At room temperature cesium's a liquid, but it binds nicely with soil (and dust!) and water. Now imagine that dust settling on cars, drifting into their upholstery, getting trapped in their air filters, and in general permeating everything. The result is a radioactive car, not because the frame or the fabric is now radioactive, but because radioactive cesium's been dusted everywhere. And it'll be all but impossible to remove from fabric and air filters and the like.
But hey, wait for about 100 years and you'll not only have a far less radioactive car but also a classic auto!
It's possible to turn non-radioactive items radioactive. For example, the neutron bomb that the US worked on would shoot out neutrons — one of the two particles in an atomic nucleus. Those free neutrons get captured by other atoms, which then become radioactive. But that's not what's happening in the case of these cars.
So there you go— not magic, but dust. Dust getting into every part of the car to such a degree you can't clean it out. I suppose if you discarded all the fabric, rubber, and soft parts, the bare metal drivetrain and frame could likely be decontaminated, but at that point it's probably cheaper to just get a new car. Thanks, science!