“...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.