Whoever it was, that sold the Nipponese government the idea of having a nuclear power plant so close to the shore, must have been the same minds behind the Shoreham plant fiasco on Long Island, NY, and the San Onofre plant brouhaha in California.
Cooling water!
For the steam turbines to work, the condenser needs to cooled.
Having a nice cool ocean nearby cuts costs.
I live 15 Miles from San Onofre.
The reason is it being shuttered is because the Replacement Steam Generators they installed, built in Japan by Mitsubishi, experienced premature failure of the internal steam tubes due to a design flaw that found its way into the two production units.
The location of the Plant has nothing to do with the shutdown.
Since we are SDG&E Customers, we are paying for the shutdown along with Edison Customers.