Fukushima Radiation Spread: Wide Dispersion and Localized Hot Spots
Yesterday’s issue of PNAS contains two papers that are first steps in tracking the radiation released by the meltdowns at the Fukushima nuclear plant. Both contain bits of good news: a substantial amount of the radiation went out over the Pacific, and most of the remainder is concentrated immediately northwest of the crippled reactors. However, they also indicate that some isotopes released by the damaged reactors were spread fairly widely across the country, raising the prospect of localized hot spots.
The two papers take somewhat different approaches to understanding where the radiation went. One of them actually involves environmental sampling of the radiation emitted by five different isotopes that were released from Fukushima. The second builds an atmospheric model of the isotopes’ spread, and calibrates the model against real-world data.
Both studies indicate that the dominant factor that determined when and where contamination occurred was rain, which brought radioisotopes released into the atmosphere to earth. That interacted with the specific timing of different events—the explosions that destroyed the reactor buildings and the venting of radioactive steam—to create complex patterns of radioactive contamination. So, for example, a large release on March 15 ended up primarily contained in the prefecture of Fukushima itself. In contrast, a release on March 21 was able to travel further, and resulted in contamination of a number of neighboring prefectures (Japan has 47 prefectures overall).