A worker checks radiation levels on the window of a bus during a media tour at Japan's Fukushima Dai-ichi nuclear plant in the town of Okuma, Fukushima prefecture on June 12, 2013. - 

The news out of Fukushima just keeps getting worse. More than two years after a tsunami set off a nuclear meltdown at the Japanese power complex, government officials admit radiation leaks there are much more severe than first reported. And the cost to contain the leaks is pretty astounding. Officials say they'll spend almost $500 million on dealing with contaminated water alone.

Much of that money will be spent on building a nearly mile-long underground ice wall.

Ice walls are most commonly used on subway construction and mining projects. Engineers drill pipes into the ground, fill them with some sort of coolant and ....voila...the ground freezes. The idea at Fukushima is to block contaminated water from leaking into the sea. The challenge is it's never been done before on this scale at a nuclear disaster site. The presence of radioactivity ups the risk factor to a whole new level.

Ed Yarmak helped build an experimental ice wall at Oak Ridge National Laboratory in the 1990s. He says it's "old science" engineering-wise. But building such a massive ice wall at a radioactive site is new. "Keeping your people safe and not spreading the contamination around, that's the hardest part in this situation," says Yarmak.

But the $500 million ice wall is just a start. Officials figure clean-up, including getting the nuclear fuel rods safely off the site, will cost about $112 billion. Peter Bradford, a former nuclear regulator in the U.S., says it will also take years. Bradford served on the Nuclear Regulatory Commission during the Three-Mile Island disaster in the late 1970s. "It was five years before we even got cameras close enough to the core to be sure of how much damage there really was," says Bradford.

Bradford visited the evacuation zone around Fukushima last year. "There's a lot of mistrust about safety and what officials are saying," he says. Even the government's announcement to spend almost $500 million on the leaking-water crisis at Fukushima was met with cynicism by some. They noted the announcement came just days before the International Olympic Committee decides whether or not Tokyo will host the 2020 Olympic Games.

Follow Sarah Gardner at @RadioGardner