From the first article linked, there is a single informant that claims nuclear material was aboard a scuttled ship. The article as linked provides no further information, but mere allegation is sufficient for mdsolar to blame nuclear power.
In the actual article, one will note that there is no actual speculation about the Yakuza having any ill-intent. Indeed, it seems to be a general article about how the Yakuza win contracts in construction and cleanup. And after a massive earthquake and tsunami, there's lots of cleanup to be done.
As an interesting aside, he article claims that the Yakuza get 3% of the total construction in Japan. I see no reason to suspect that wouldn't include projects related to all forms of energy. I trust mdsolar would agree with my "Japanese solar power in bed with organized crime" headline.
There are legitimate gripes about nuclear power. Indeed, the numbers I've seen suggest operating costs that aren't substantially below any other forms of energy. But the sort of fear campaign spread by mdsolar (someone who himself stands to profit from such fears, see his profile for links) is unacceptable.
Real Users are afraid they'll break the machine -- but they're never afraid to break your face.