Japan restarted one of its nuclear reactors on Tuesday, the first to begin operating under new safety codes since the Fukushima disaster. The No. 1 reactor at Kyushu Electric Power was started after more than four years of being powered down following the 2011 meltdown.

The meltdown was triggered by an earthquake and tsunami. The reactor is back online and running without any problems, said a Kyushu spokesperson, according to Fox News. Japan relies heavily on nuclear power.

New, strict safety codes have been put into place following the disaster. A second reactor is scheduled to be back online Friday. It should reach full capacity in September. The country's 43 reactors were powered down for two years so they could be checked for safety.

Currently, power companies in Japan are awaiting approval to restart a total of 23 reactors.

Japan imports almost all the fuel it uses to power homes, cars and factories. Since the Fukushima disaster, energy costs in the country have risen by 20 percent or more, according to The New York Times.

Anti-nuclear groups have protested the restarting of the reactors, according to Forbes. Japan has no natural coal, oil or gas in the country. Almost 90 percent of the nation's energy is imported.