Claim: Black dust all over japan - radioactive - fukushima?


Anyone ever heard of the supposed black radioactive dust either settling or seen in air conditioner filters supposedly over a large area of japan? Its at least 2 years old and its supposed to be either corium (melted down nuclear core material) or radioactive algae/moss.

All websites that feature it are either anti nuclear or conspiracy websites.
All of the studies of the black dust stuff seems to come from the guy in this video in the first link. His claim of 40,000 petabecquerels/kg is grossly at odds with what he will present to the APHA in November of this year (second link) where he toned the hot particle down to 1 PBq/kg. He's a civil engineer.

40,000 petabecquerels/kg is ridiculous because a radionuclide with that specific activity will have a half-life of 39 hours at the longest. His microscopic "hot particle" had an activity of 310 Bq. It would have decayed away to nothing in 41 days yet it was discovered last year?
hmm good points Chew. But one rebuttal is that the low half life can be explained if fukushima is continuously or sporadically emitting radioactive dust through cracks in the ground