Some former residents of a town evacuated eight years ago after the 2011 Fukushima nuclear plant disaster have been allowed to move back for the first time.

On March 11, 2011, a 15-meter tsunami flooded three of the Daiichi plant's six reactors, killing the power and allowing the reactor cores to melt and radiation to seep out.

On Wednesday, two neighborhoods in Ōkuma were declared safe. Nearby Futaba, the other major evacuated town, remains a no-go area.

Despite the declaration, nuclear radiation levels in Ōkuma are 20 times higher than they were before the disaster. A 2018 survey showed only 13% of ex-residents wanted to return.

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Japan has allowed residents to move back to a town in Fukushima which had been under strict evacuation orders since the 2011 nuclear power plant disaster blanketed it in deadly radiation.

On March 11, 2011, 15-meter tsunami waves triggered by an earthquake flooded three of six reactors in the Fukushima Daiichi Nuclear Power Plant, causing the nearby towns of Futaba and Ōkuma to be covered in a haze of radiation.

On Wednesday Japanese authorities said radiation levels in Ōkuma's Ogawara and Chuyashiki districts, about 40% of the town, are low enough for humans to return, the Asahi Shimbun reported.

The Fukushima plant. YouTube/DocumentaryTV

The level of nuclear radiation in Ōkuma is now at 20 millisievert — the same as what people who work in nuclear power plants experience — but before the disaster it was as low as 1 millisievert, the Associated Press (AP) reported.

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In total 160,000 people had to flee the area after the earthquake caused waves to disable the reactor's power supply, leading to widespread nuclear contamination. Of those, 10,000 lived in Ōkuma.

Reactor units 1 to 4 are seen over storage tanks for radioactive water are seen at Fukushima Daiichi nuclear power plant in Okuma town, Fukushima prefecture. Reuters

The government, in tandem with the plant's owners Tokyo Electric Power Co., have been working ceaselessly to decontaminate the area since the disaster, removing topsoil, chopping down trees, and scrubbing houses and roads clean, AP reported.

An elderly man taken by wheelchair to be scanned for levels of radiation in Koriyama, Fukushima Prefecture. Sunday, March 13, 2011. AP

"We are finally standing on a starting line of reconstruction," the mayor of Ōkuma, Toshitsuna Watanabe, told reporters on Wednesday.

The town is getting back on its feet, with a new corner shop, town hall, and 50 new homes all opening in May.

Ōkuma's town center, hospital, and main train station, however, are still off limits, rending the town's facilities limited.

Evacuees of Ōkuma, who are dressed in protective suits, offer prayers for victims of the disaster, one year after the disaster Reuters

There's no guarantee residents will repopulate the town, though. A 2018 survey of ex-residents found only 13% wanted to return to their old homes, the AP reported.

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Nearby Futaba is still off-limits to people, but the government said it hopes it will re-open in 2020.