*Worsening picture at Japanese power plant

Emergency efforts to pump seawater into one of the reactors has failed, at least temporarily, increasing the risk of an uncontrolled release of radioactive material. Tokyo Electric Power says that water levels inside the reactor's containment vessel are falling, which means that fuel rods are being exposed. From the NYT:

The more time that passes with fuel rods uncovered by water and the pressure inside the containment vessel unvented, the greater the risk that the containment vessel will crack or explode, creating a potentially catastrophic release of radioactive material into the atmosphere -- an accident that would be by far the worst to confront the nuclear power industry since the explosion of the Chernobyl nuclear power plant 25 years ago.

In reactor No. 2, which is now the most damaged of the three at the Daiichi plant, at least parts of the fuel rods have been exposed for several hours, which also suggests that some of the fuel has begun to melt. If more of the fuel melts before water can be injected in the vessel, the fuel pellets could burn through the bottom of the containment vessel and radioactive material could pour out that way -- often referred to as a full meltdown.

"They're basically in a full-scale panic" among Japanese power industry managers, said a senior nuclear industry executive late Monday night. The executive is not involved in managing the response to the reactors' difficulties but has many contacts in Japan. "They're in total disarray, they don't know what to do."

*Update:

Tokyo Electric announced that workers had succeeded in opening a malfunctioning valve controlling the vents, reducing pressure in the container vessel. It then resumed flooding the reactor with water. The company said water levels were not immediately rising to the desired level, possibly because of a leak in the containment vessel. Still, a Tokyo Electric official said the situation was improving. "We do not feel that a critical event is imminent," he told a press conference.