In normal conditions, the fuel rods would be covered and cooled by water

"Earlier on Monday, the explosion at the Unit 3 reactor rocked the seaside nuclear complex. The International Atomic Energy Agency reported that injections of seawater into units 1 and 3 had been interrupted because of a low level in a seawater supply reservoir, but the seawater injections were later restored."

"Although Tokyo Electric said it also continued to deal with cooling system failures and high pressures at half a dozen of its 10 reactors in the two Fukushima complexes, fears mounted about the threat posed by the pools of water where years of spent fuel rods are stored."

"At the 40-year-old Fukushima Daiichi Unit 1, where the explosion Saturday destroyed a building housing the reactor, the spent fuel pool, in accordance with General Electric’s design, is placed above the reactor"

"People familiar with the plant said there are seven spent fuel pools at Fukushima Daiichi, many of them densely packed."

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