"The cost of dismantling the Fukushima plant may reach 20 trillion yen"
That's ridiculous! Don't the Japs have any ingenuity?
All they have to do is spend a million on an expired super tanker (like the one below being scrapped in India). Then excavate and vacuum all the contaminated sites and dump it all into the tanker. They can also mix it with cement to make it solid. Then just sink the ship in the middle of the Pacific where it 10km deep.
It would take 200 years to decompose and would contribute no more than than the background radiation already in sea water.