A series of nuclear reactors continue to deteriorate in the wake of Japan's devastating earthquake and tsunami, raising worries of a nuclear meltdown.
After two hydrogen explosions in three days at the Fukushima Daiichi plant, a third reactor has lost its ability to cool. Officials are increasingly concerned about unit 2 at the plant.
The fuel rods on unit 2 were fully exposed for a period of time, a dangerous development in the effort to stop the reactor from melting down. Workers are frantically pouring sea water over the rods, officials from the Tokyo Electric Power Company said.
"They continue to work hard to raise the water level to cover the fuel. Let's pray again," Tatsujiro Suzuki, Vice Chairman of Japan's Atomic Energy Commission, posted on Facebook today.
The exposure of the fuel rods means that the temperature in the reactor is likely to rise, which will allow it to make steam. The steam could lead to the creation of hydrogen and cause another explosion, experts said.
Knowing how long the fuel rods have been exposed is key to understanding if there is a real chance of a meltdown, Dr. Peter Hosemann, a nuclear energy expert and professor at the University of California at Berkeley, said.
"Having too much of the fuel rods exposed for too long of a time can lead to the core melt. Again, if a core melt happens the reactor pressure vessel and the containment are designed to contain it," Hosemann said.
While unit 1, the first reactor to explode at the plant, appears to be stable, unit 3, which exploded early Monday morning in Japan, reportedly has a leak in its bottom.
"We've never encountered this type of situation in history before," Joe Cirincione, a nuclear policy expert, said. "We are beyond a reactor crisis at this point, this is a nuclear system crisis. The entire northern part of the Japanese nuclear power system has been delivered a body blow."
The leak is making it difficult to keep the core of the reactor covered with sea water, Dr. Michio Kaku, a physicist, said.
"The situation is getting worse by the hour. We haven't hit bottom yet... We now have reports that unit 3 suffered perhaps a 90 percent uncovering of the core -- this is unprecedented since Chernobyl," Kaku said.
Japanese officials insist that things are under control at the nuclear plant and that radiation levels are safe.
"They haven't stabilized the sea water yet. Remember, they're hanging in there right there with the fingernails. This is how close we are to a full-scale meltdown. So it's stable in the sense that you're stable when you're hanging by your fingernails," Kaku said.