Hamaoka Nuke Plant, which sits on a soft rock right by the beach, wouldn't need a big tsunami from a big earthquake to get knocked out. All it would take is an earthquake the size that's anticipated in the region (Tokai) for a long time and which is said to be overdue.
Even the Fukushima I Nuke Plant accident was not caused by the tsunami. It was the earthquake that knocked down the only power transmission tower that supplied electricity to the plant, and that was the beginning of the crisis at the plant that has affected wide areas in the entire northern hemisphere. Of all the TEPCO's power transmission towers, that was the only tower that fell down.
But never mind the details like that. The embattled PM Naoto Kan would do anything and everything to show to people in Japan that he's in charge, and he "requested" Hamaoka Nuke Plant be stopped because "it does not have adequate measures against the tsunami that may be generated after a big Tokai earthquake.
By the time the tsunami from the big quake hits Hamaoka, there may be not much left to sweep away.
Yomiuri reports (5/7/2011) that:
Prime Minister Kan held a press conference at the Prime Minister's Official Residence and announced that he had requested Chubu Electric Power Company to halt all the reactors at its Hamaoka Nuclear Power Plant (Omaezaki City, Shizuoka Prefecture). The request was conveyed to Chubu Electric by Minister of Economy and Industry Kaieda.
As to the reason for the request, Kan pointed out the necessity for stronger measures against tsunami such as breakwater because of the high likelihood of a Tokai earthquake centered in Shizuoka Prefecture, and said "It is for the safety and security for the citizens. I also considered the grave effect on the Japanese society if a serious accident were to happen [at Hamaoka Plant]. Chubu Electric is likely to obey the Prime Minister's request.
The Prime Minster's "request" has no legal basis nor power of enforcement.
Goshi Hosono, the PM's assistant who had said they "didn't feel like announcing" that there was probably a core meltdown at Fukushima, said of his boss' decision that "it was a political decision because of very high probability (84% probability within the next 30 years) of the Tokai earthquake". Right. And natural disasters like earthquake and tsunami will be prevented by that political decision.
Haven't they learned anything in the past 7 weeks or so? Betting on a high probability wouldn't have stopped the earthquake of March 11 (which had been assigned a very, very low probability) and tsunami (also assigned a very, very low probability), or the complete shut down of the power of any source (assigned a very, very, very low probability close to zero).
The opposition groups against Hamaoka Nuke Plant are some of the most vocal, visible, and the most organized of all the groups in Japan that oppose nuclear power plants. Kan must have figured it would be very easy to score some points with these groups.
As for Hamaoka, as this blog has pointed out in the past (here and here), the plant sits on an active fault or two, practically on the beach. The Tokai earthquake itself and the resulting liquefaction would knock the plant out before tsunami would come. (And Godzilla will come...)