Reply #4: The graphic assumes a constant plume

[FBaggins]

Radiation monitoring at the site imply that it's anything but constant, but if you're going to build a model you have to start with SOME assumptions.

Note that the model has nothing at all to do with radiation levels. There just isn't enough information to guess at that. It's just a visual depiction of how the plume might spread and when various monitoring stations could be guessed to start picking things up.