Iida said Fukushima Daiichi's reactors remain too hot to pour concrete, but he suggested pouring a slurry of minerals and sand over them to carry away heat before encasing them.

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Each of the 65-foot-tall, 640-ton generators -- built by Japan's Mitsubishi Heavy Industries -- are packed with thousands of narrow tubes that carry hot, pressurized water from the reactors.

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These rods, while not as hot as the ones currently in the reactors, also require cooling water to prevent overheating that could lead to a meltdown.

FORBES: What the Japanese Government/Media Doesn't Want You to Know About the Nuclear Crisis