They should have at least gone liquid thorium or something similar... much safer, I get why they have this plant I think it's 30-40 years old and thorium wasn't in great supply then, but now when they mine things like lithium and other rare-earth materials they mine up thorium in abundance, and aside from use in molten thorium reactors... it doesn't really have any other industrial uses.
Maybe this will be a lesson to Japan, and other nations, to finally use the safer nuclear options.