Is more radiation absorbed by the ground or the atmosphere?

We put this question to Dr Ian Farnan from the Department of Earth Sciences at Cambridge University:

It very much depends on the way that the release happens. If you look at the Chernobyl incident, the radioactive cloud or the explosion took it up 30,000 feet in the atmosphere. Here, the major release is coming from a leak in one of these steam separation or pressure regulator devices below the reactor where there's a 20 centimetre crack, and that's going straight out into the sea, so that's going into the ground water system around the reactor.