Japan switched on a nuclear reactor Tuesday on the southern island of Kyushu, marking a first, tentative return to nuclear energy after catastrophic meltdowns four years ago at the Fukushima plant.

The reactor is the first to be restarted under strict new regulations governing safety at nuclear power plants in this ­earthquake-prone nation, and its operation advances a key goal of Prime Minister Shinzo Abe.

At 10:30 a.m. Tuesday, workers at Kyushu Electric Power’s Sen­dai plant pulled the control rods out of reactor No. 1, triggering nuclear fission for the first time since it was taken offline in May 2011, Kyodo News reported. The reactor is expected to start generating power by Friday, and the plant’s second reactor is set to be turned on in October.

“We prioritize safety more than anything,” Abe told reporters the day before the restart. “Based on the harsh experience of Fukushima, we will not restart any plants unless they are approved as they meet the world’s strictest standards.”

After a devastating earthquake and tsunami caused a triple meltdown at the Fukushima Daiichi nuclear power plant on Japan’s east coast in March 2011, the country idled all of its nuclear reactors while it conducted safety checks and drew up new regulations.

A protester shouts slogans during an anti-nuclear rally in front of the prime minister's official residence in Tokyo. (Shizuo Kambayashi/AP)

This led to skyrocketing electricity prices as Japan had to import oil and gas for energy, further straining public finances and family budgets. Household electricity bills rose 25 percent over four years through March, Kyodo News reported, citing government data.

As he tries to kick-start the economy, Abe has been promoting a return to nuclear power as a critical way to boost growth and help Japan become more efficient.

Tuesday’s move could pave the way for the country’s 42 other workable reactors to come back online, although safety inspections and legal challenges may delay the process. Only five reactors at three sites have been cleared for restart under the new rules, and a court has blocked one of those.

With memories of the Fukushima disaster — the world’s worst nuclear accident since the 1986 catastrophe at the Chernobyl plant in Ukraine — still fresh, polls show that a majority of Japanese oppose returning to an energy source they consider unsuitable for such earthquake-prone islands.

Anti-nuclear protesters gather daily at an intersection near government ministries in Tokyo, and they have been rallying outside the heavily guarded plant in Kyushu for several days.

“I cannot understand why operations are resuming,” Tatsuya Yoshioka, director of rally organizer Peace Boat, said Monday, according to the Asahi newspaper.

Protesters at the plant, at the southern tip of mainland Japan, included Naoto Kan, who was prime minister during the Fukushima disaster.

The meltdowns forced the evacuation of more than 160,000 people from the surrounding area, parts of which remain radioactive zones. Tens of thousands of people continue to live in temporary housing and will likely never be able to return to their homes.

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