Visiting Radioactive Chernobyl

Carolyn and I visited the Chernobyl reactor site with a Singularity University reunion organized by Andrew Bain (who did an amazing job, BTW, thanks!).

We had a walk to the crippled facility, the visitors center (in the shadow of the west wall of the crippled reactor), and a walk around the town of Pripyat made famous by Elena.

Chernobyl seems a particularly relevant lesson in light of the hysteria over radiation reaching the US from Fukushima. It has been 25 years since the reactor accident at Chernobyl and it is a good test of what will happen in Japan.

In Fukishima the reactor cores melted and cooling water carried radioactive material into the ocean, while there were gaseous emissions of hot materials, including (apparently) some radio isotope emissions. There were a few explosions, but of hydrogen liberated by thermal reaction – that is chemical explosions (not a “hydrogen bomb” as in an explosive fusion reaction). When Chernobyl’s reactor 4 blew up, the core blew open and the 2,000 ton upper plate launched 30 meters in the air, through the roof of the containment building, to crash down 90 degrees rotated into the core base. Without coolant, the core itself vaporized (kind of a fizzle yield bomb, about 3 tons of TNT) which blew almost all of the fuel into the air to disperse over the countryside, mostly into Belarus.

We measured radiation levels on the site as we went:

• 0.14 µSv/h in Kiev (granite buildings).
• 0.10 µSv/h at the 30km exclusion zone
• 0.10 µSv/h at the 10km exclusion zone
• 0.66 µSv/h at the south fence line of the reactor
• 3.41 µSv/h at the monument in front of the west wall of the containment
• 7.04 µSv/h in some dirt at the abandoned amusement park
• 16.07 µSv/h in the car driving over the plume – that was the only place where it seemed as trees hadn’t returned immediately.

According to XKCD, a NY-LA flight = 5 hrs = 40µSV = 8µSv/h.

Working at the visitors center, right next to the destroyed reactor, results in an exposure rate less than half that a flight attendant gets. Not that it would be smart to dig around (the contaminated dust from the explosion is estimated to be buried about 10cm by now), nor would I suggest eating the local produce, but walking around one needs only minor precautions such as long pants and closed shoes as beta emissions are highest at ground level and are significantly absorbed by the air before getting to head level. The ground we walked on had been cleaned, radioactivity levels were higher in the woods and other areas that hadn’t been scrubbed and stripped, but by now are no longer particularly dangerous.

25 years after the explosion there is a lot of activity on the site and on a nice summer day, we were told, 1,000 tourists might visit. We were one of three small groups when we were there, a bit early in the season, and at 8, the largest.

The site itself has become very beautiful, pretty woods with lots of birds and apparently moose and other large animals roaming around more or less happily free of people. The degree to which the surrounding forest has overtaken the abandoned town of Pripyat is quite amazing and shows the transience of human construction. Like every tour group, we visited the iconic school and amusement park, which are particularly poignant.

On the way out, we had to pass through a tourniquet (or turnstile in alternate translation) with radiation detectors. We were told that if we were contaminated we would have to try to clean up to get a passing score and anything that couldn’t pass had to remain. Nobody set off any alarms.