I feel that the question is not if Tepco decides to dump low level radioactive waste into the ocean rather than let it evaporate into the air. It is - what are we doing pretending these things make economic sense in the first place.
You would think people would figure out that if an atomic reactor melts down, cracks open (which has happened twice now & almost a third time at 3 mile island) - makes a good chunk of land uninhabitable for the foreseeable future with radio active cesium - it would ruin any economic reason for their further construction or their continued operation. Let's put aside for the moment those other unresolved problems such as where to store the radioactive waste the existing ones generate on a good day. It will be interesting to see how much it will cost and how long it will take to clean this one up - I've heard 40 years and 100+ billion dollars in an engineering journal - it's needless to say an extremely hard problem - think lots of robots that haven't been even designed yet as people can't get near the messy critical places to do any work. In general it's very hard to make anything fail proof and economic - especially when the consequences of failure are unthinkable. For example the Earth quake that was in the DC area a couple of years ago was centered close to an atomic power plant in Virginia - I recall the magnitude of the Earth quake was very close to the design limit of the reactor.