Kyushu's Sendai reactor was commissioned around 30 years ago, raising doubts whether the unit may be too old to withstand future disasters, such as the large earthquakes common across Japan.  "They are on the edge, seeing as most reactors above 40 years of age are considered to be aging," Daniel Aldrich, professor of political science and co-director of the Center for Resilience Studies at Northeastern University in Boston, told CNBC.  The country has embraced stricter guidelines and new technology for the entire nuclear industry since the 2011 tragedy, but according to Aldrich, "the question is, for Japan to extend the life and licensing of these aging reactors, can they convince the population that these reactors are safe?"  The Sendai reactor is also located near an active volcano.  "Plants now have waterproofing, airlocks installed around outside gates and generators on roofs. Even with a strong tsunami, these kind of backup measures should work but a volcano is a different area, one that most critics say units are not prepared for in the case of massive natural disaster," Aldrich said.  Moreover, the mandatory evacuation plans issued by the government in the case of a disaster are lacking and don't bode well for confidence, Temple University's Brown warned. The evacuation procedures only cover areas in a 10 kilometer radius of the Sendai plant, with no detailed plan for distances outside that perimeter, he said, adding that the volcano is about 50 kilometers away from the reactor.  "It's a really hard sell to convince people living in these areas that these evacuation plans are realistic for the kind of disaster we saw in Fukushima," Aldrich added.
Japan's fifth-biggest utility is set to turn on the switches at one of its nuclear reactors on Tuesday, a momentous occasion for the country.