I would have to do the math to determine how much plutonium is present at Fukishima and I don't have the data that would allow me to so. How many fuel rods, how old they are and what % was plutonium when new.
I think only one reactor was a plutonium reactor the other three are enriched uranium.
My main point was that in an air blast only the bomb parts (mostly) become fallout. Air blasts are much cleaner then ground blasts where tons and tons of dirt interact with the fissionable materials and become radioactive. Now perhaps the total radiation release is the same but ground blasts produce more much fallout.
Personally I think the article is greatly overstating the dangers. Spent fuel rods will over time cool down, so without knowing how long the rods have been in the pool it is difficult to know how great the danger. But if the rods are capable of melting the pool then the danger from those rods is very real. They are still pretty hot and there are hundreds of tons of them, not a few hundred pounds. And they will be reacting with the ground (dirt) not the atmosphere at 1500 feet.
I have read that the water temp in the pool is under 100C if so the rods are not all that hot. However that could change if all the rods wind up in a pile under the pool. The reactors are still very hot and still a big problem.
Part of the ambiguity of this question is the distinction between "used up" and "converted into energy". The uranium is "used up" when it is no longer uranium. The mass "converted into energy" is a much smaller number which is the energy converted from the difference in mass of the original uranium and the by-products of uranium fission.
Also, did you mean to write "U235" for the Hiroshima bomb?
I read that the total amount of fuel at Fukushima is about 2000 tons and that the six reactors contained 100 tons.
It's complicated to compare the contamination potential of a bomb with that of the Fukushima incident, but there's certainly a lot of "stuff" at Fukushima. What an incredible mess.