... At least when it comes to the release of radioactive cesium-137, which has a half life of about 30 years.

The amount of radioactive cesium that has leaked from a tsunami-hit nuclear plant is about equal to 168 of the atomic bombs dropped on Hiroshima at the end of World War II, Japan's nuclear agency said Friday. ... NISA has said the radiation leaked from Fukushima was about one-sixth of what the Chernobyl disaster released in 1986.

A separate government report released Thursday said that 22 percent of Cesium-137 and 13 percent of Iodine-131 released from the plant during the crisis have fallen on the ground, with the remaining either fell into the ocean or outside the area of simulation.

If it's not on the ground and not in ocean, I assume "outside the area of simulation" means everywhere else on the planet earth.

Elsewhere in Japan today, Prime Minister Naoto Kan has resigned.