On Saturday, Japan will turn off its last operational nuclear reactor, the Tomari plant on the island of Hokkaido. That means, since last year’s disaster in Fukushima, the country will have shut down all 54 of its nuclear power plants. But how long can Japan remain nuke-free?

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By contrast, the IEEJ report found, if Japan began switching its nuclear reactors back on this summer, the economy would grow 1.9 percent this year — largely because lower electricity prices would allow factories to ramp up production. What’s more, by curtailing its fossil-fuel imports, Japan would be able to run a trade surplus this year, instead of a projected $57 billion trade deficit. (Currently, Japan imports about 90 percent of its oil from the Middle East, and the country’s newfound appetite for crude has helped drive global prices upward.)

What Japan does with its reactors could have significant climate-change consequences, too. While Japan is trying to supplant its nuclear reactors with more solar, wind, and energy-saving measures, that’s a gradual task. The IEEJ report found that Japan’s emissions would grow 5.5 percent in 2012 if its reactors stayed off-line, as fossil fuel imports displaced carbon-free nuclear power. By contrast, restarting the reactors would cause Japan’s carbon emissions to drop by 5.3 percent in 2012, even as energy use grew.

That helps explain why Japan’s prime minister, Yoshihiko Noda, recently told The Washington Post that the country needed to restart the reactors, and soon. “I think it’s the government’s responsibility to ensure that there won’t be too much stress on the people and on mid- to small-size corporations,” Noda said. “So we must explain to the people of Japan clearly, with that in mind.” That wouldn’t be a popular decision, however — many of Japan’s local leaders and provincial governors have opposed a restart, at least until the government enacts stricter safety measures.

Even if Japan eases up on its nuclear moratorium, however, the effects of Fukushima are still likely to ripple through the world’s nuclear industry for years to come. No matter what happens this summer, it’s unlikely that Japan’s nuclear capacity will grow significantly in the years ahead. And Germany, Belgium, and Switzerland have all announced plans to phase out their nuclear power plants by 2025 at the latest.

Plenty of other countries are pushing ahead with planned reactors — from Argentina to Bulgaria to Russia. But the International Energy Agency now expects (pdf) that those plans will get bogged down in delays, as countries mull additional safety requirements and siting restrictions. (China, for instance, froze its approval process for new reactors after Fukushima happened, and the IEA expects the result to be 5-10 fewer plants by 2020.) Here’s a chart of reactors underway:

All told, there are roughly 440 nuclear reactors in operation around the world — and that number has stayed roughly constant for the past decade. The International Energy Agency had originally expected nuclear power to nearly double in the next decade, from 350 gigawatts of capacity to 650 gigawatts. But now? The IEA’s revising its forecasts down by at least 25 percent.