I'm not an expert, but the Fukushima's core problem was an older design based on active cooling, that requires continuous water input and thus electricity to run the water pumps. Current work is concentrated mostly on making nuclear plant as passive as possible, resulting in graceful shutdown in the event of supporting equipment failure. This involves finding a coolant that behaves predictably and nicely when various subsystems go down (water does not).

Additional reading: http://www.technologyreview.com/news/423307/newer-nuclear-re... https://en.wikipedia.org/wiki/Passive_nuclear_safety