Yesterday, the Sendai Nuclear Power Station Unit 1 became the first nuclear reactor to return to service since Japan shut down its entire program in the wake of the Fukushima meltdown. It will take several days to start generating electricity and roughly a month to reach its full 846 MegaWatts capacity, but the restart marks a major milestone for a country that once received about a third of its power from nuclear fission.

According to the Energy Information Administration, Japan once had 54 individual reactors in service. Six of those are at Fukushima, and thus have been removed from service. Another five have been permanently shut as well. The remainder are now subject to revised safety rules following the flaws identified at Fukushima. After obtaining operational approval from the national regulator, plants also need to obtain an OK from the local prefecture's government.

So far, nearly half haven't even filed for approval with the regulators. Of the remaining 24 reactors, only five have been approved and are awaiting on decisions from the local government. One of those five is a second reactor at Sendai, which is expected to restart later in the autumn. But two of the others, according to the EIA, are held up indefinitely. "Fukui Prefecture continues to oppose the restart of Takahama Units 3 and 4," the EIA said.

The current government hopes to have nuclear power back up to 20 percent of the grid by 2030. But it also plans to double renewable generation, having it reach the same 20 percent figure by 2020. In the intervening, post-Fukushima period, however, the country has been forced to boost its use of fossil fuels.