“...On the same page there is a note about the high value of 530 Sv/h reported for point number 2: although a direct comparison is not 100% correct, if one was to measure the radiation right on the surface of a fuel bundle one day after the stopping of the nuclear reaction, the dose rate value would be of the order of several tens of thousands Sievert per hour. (This certainly helps put things in perspective.)”
https://www.physicsforums.com/threads/japan-earthquake-nuclear-plants-part-2.711577/page-56
These guys have been the best source for info on Fukushima.
Mostly nuke plant operators and students to be operators participate.
I’m thinking there is a lot of Exaggeration and dare I say inaccuracy with the levels of Radiation in this article. For the most part, ... I venture to say.... there isn’t an instrument on the planet that can measure these (mentioned Rad) levels with any kind of accuracy. As for the math problem and extrapolation(s) there are factors that are not consistent and yet cannot be ignored. Conditions for Sky Shine are not always predictable, and Ionizing Radiation interacts in various ways with differing results (buildup, etc.,) to attenuation by differing natural materials.
I agree at Fukushima, some localized...Rad levels are lethal, -however to project such Grave Danger conditions to Spikes of Unimaginable Levels to the Northern Hemisphere, - is reminiscent of the Connie days at TMI. BTW, With those levels, the electronics integrity in any Robotics, or drone device(s), would be let us say ? somewhat ..... unstable.