The raw volume in metric tons of debris out there is beyond comprehension.
It cannot be solved by surface vessels doing garbage collection. At least, not before the next tsunami rolls in somewhere else and does the same thing. The Fukushima debris is only a fraction of what's out there. There's a giant floating garbage dump in the Pacific, and the Fukushima stuff will merge with it as it all decomposes.
Eventually, all this material will sink to the bottom of the ocean and decompose. It's buoyant right now, but it won't remain buoyant forever.