For more than four decades, the Kansai region has relied on Fukui Prefecture's nuclear power plants, including 11 operated by Kansai Electric Power Co. (Kepco), to keep the region powered up.

But now that a growing number of plants are nearing or have reached the end of their 40-year life cycle, the question is: What's next?

While most of the discussion is focused on whether to continue running or decommission them, there is an interesting — to be polite — school of thought among certain politicians that says they should be replaced with underground reactors.