Zoom out to view Chernobyl’s radiation over Fukushima. Rotate to the Ukraine to see Chernobyl in context. Download File (source: UNSCEAR / MEXT ) This embedded version of Google Earth may have limited functionality on some browsers.

This Sunday (11 September) marks the six-month anniversary of the triple meltdown at the Fukushima Daiichi nuclear power plant in Japan. The accident has slipped from the headlines, but new data are coming out all the time. Some of the most recent findings are allowing the best comparison yet of Fukushima with Chernobyl.

A lot of media outlets (ourselves included) first made the Fukushima-Chernobyl comparison back in April, when the Japanese revised their estimate of the Fukushima accident—rating it a seven on the seven-point international INES scale. The conclusion most reached at the time was that, although the rating was the same, Fukushima was a much smaller accident.

A couple of things have changed since those first reports. First, the Japanese doubled their estimate of the radiation released by Fukushima in June to 7.7×1017 Becquerels (Bq). Then, on 30 August, they released the first maps of radioactive caesium-137 (Cs-137) contamination from the plant. Cs-137 has a half-life of 30 years, and it’s considered the major long-term contaminate for both accidents.

With the new Cs-137 data, we can now directly compare the fallout from Chernobyl to Fukushima. Check out the Google Earth mashup above (zoom out to see Chernobyl on top of Fukushima, and rotate over to the Ukraine to see Chernobyl in context).



The first thing that you can see is that Chernobyl is indeed quite a bit bigger. In fact, the permanent exclusion zone (red) encompasses most of the Fukushima fallout map (download the .kmz) to toggle the overlay on and off). If Fukushima had been a Chernobyl-scale crisis, significant amounts of radiation would have spread all the way up to Iwate Prefecture, and depending on the winds, it’s not inconceivable that Tokyo might have been hit with serious levels of fallout.

But that’s not the whole story. If Chernobyl had happened over Japan, much of its Cs-137 contamination would have ended up in the Pacific. Similarly, a good deal of the Fukushima fallout isn’t seen here because it has blown out into the ocean. Indeed, the total estimate delivered to the International Atomic Energy Agency in June states that Fukushima has released 1.5×1016 becquerels (Bq) of Cs-137—about a fifth of the Cs-137 from Chernobyl. The total radioactive release from Fukushima is currently estimated at about 5.5% of Chernobyl, which spewed an incredible 1.4×1019Bq.

The Fukushima fallout is notable for what it doesn’t contain. Some very nasty contaminants like strontium-90, americium-241, and various plutonium isotopes are all absent in any significant quantity because the concrete vessels around the reactors appear to be largely intact. In Chernobyl, the explosion and subsequent fire spewed these extremely dangerous isotopes far and wide.

The bottom line here is that Fukushima and Chernobyl are comparable, and a comparison really helps underscore the differences. Fukushima’s heavy containment vessels limited the spread of some dangerous isotopes, but the coastal location makes marine contamination a much bigger issue than it ever was for Chernobyl. The latest maps suggest that there will be a permanent exclusion zone to the northwest of Fukushima, but it will likely be quite a bit smaller than the one at Chernobyl.

For a quick update on what’s been happening at Fukushima, check out our latest video:

For continuing coverage of the Fukushima crisis, check out our Japan quake special.

For a selection of our coverage in Japanese, visit Nature Asia Pacific.