Japan's fifth-biggest utility turned on the switches at one of its nuclear reactors on Tuesday, a momentous and fraught occasion for a country still grappling with the aftershock of a deadly nuclear meltdown four years ago.
Kyushu Electric Power Company's Sendai plant, located in the southern Kagoshima prefecture, is the first to come back online since Japan issued new safety requirements in 2013.
Japan's 48 functioning reactors have largely been shut since the catastrophe at Tokyo Electric Power Company's Fukushima Daiichi plant in 2011, one of the world's worst nuclear disasters.
Kyushu's Sendai reactor is one of at least 25 expected to restart over the course of the next decade as Prime Minister Shinzo Abe aims for nuclear power to generate 20-22 percent of the country's electricity by 2030, compared to 30 percent before the nuclear closures. Another 20 reactors are in various stages of the restart process, according to the Nuclear Energy Institute.
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Abe's ruling Liberal Democratic Party (LDP)—a group that's almost continually been in power since 1955)—has traditionally viewed nuclear power as a means of energy independence.
Tuesday's restart has far-reaching consequences for Japan's politics and economy. Here are the key issues:
Politics
The move is highly controversial among citizens, with regular opinion polls revealing that a clear majority of the population want Japan to end nuclear power.
A March telephone survey by Asahi Shimbun showed 59 percent of respondents were opposed to the restart of all plants. Meanwhile, 57 percent of more than 1,000 respondents were opposed to the Sendai plant's reactivation, a new Mainichi Shimbun public poll showed on Monday.
Fears of another meltdown and the option of focusing on renewable energy were some of the reasons commonly voiced at recent anti-nuclear protests throughout this year.
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"This is absolutely the worst possible timing given public opinion is significantly moving away from Abe: There is already backlash against his security bills and last week's Hiroshima commemoration didn't go well for him either," James Brown, assistant professor at Temple University in Tokyo, told CNBC, referring to new legislation that would end Japan's pacifist constitution.
"If we start to see some connection between nuclear issues and the collective self-defense concept behind the security bills, i.e. a connection between civilian and military nuclear usage, that's particularly dangerous for Abe's popularity."
Despite public disapproval, the government will be able to implement its nuclear policies due to the lack of a strong political opposition, Brown explained.
Safety
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.
Money
Finances are a key reason behind Abe's determination to bring nuclear power back.
Japan currently imports oil, primarily from the Middle East, and eliminating fossil fuels from its import bill could free up $65 billion—the amount Tokyo spent on liquefied natural gas in the past financial year.
However, the enormous import bill isn't sufficient reason for a nuclear resumption, Brown said.
"In the longer term, Japan's population will be in decline, they will be more efficient in energy usage, and overall gas demand should slow. The government is also going big on renewable energy, which should also lower demand."
Kyushu also received a $980 million government bailout last year so the government feels it doesn't have any choice except to go ahead with the restart in order to see a return on its investment, Aldrich added. Moreover, nuclear power doesn't come cheap, which means a lower oil import bill will be offset in higher nuclear costs.
"Marginal operating expenses are low but the longer-term costs are incredibly high. Regulatory standards have increased, so nuclear operators need to install more equipment, which means higher costs," Brown added.