Japan Tsunami Update: Nuclear Power Plant in Meltdown

TOKYO— A day after Japan’s devastating Tohoku earthquake and tsunami, core meltdown is underway the Fukushima No.1 nuclear power plant and, at this point, appears to be unstoppable. A mid-afternoon blast on Saturday demolished the structure housing an overheated and leaking reactor, raising the probability of a full-scale nuclear disaster, which could release radiation across the U.S. and even parts of Europe.

Just past noon in Japan, the Industrial Nuclear Safety Agency reported that the radioactive isotopes cesium and iodine had been detected by a monitoring station near the Fukushima plant. The facility has six reactors, three of them operating at the time of the earthquake. Two of these are overheating and Reactor 1 is leaking radioactive particles into the atmosphere.

The presence of these isotopes in air samples is a sure indicator of an uncontrolled chain reaction. Japanese nuclear engineers are explaining that overheated uranium rods seared through their metal casings, triggering the start of nuclear fission. The regulatory agency's statement contradicts the earlier claim of the plant’s operator, TEPCO, that all uranium rods were intact.

The afternoon explosion, which injured four workers, is hampering efforts by emergency workers to pump cold water into the reactor and release steam through safety valves. The internal steam pressure inside the reactor vessel is more than twice the approved level of the original design.

Truck-mounted generators have restored electrical power. The government has been frantically trying to locate robots to reopen the control room, which is now 1,000 times more radioactive than safe levels for humans. The cooling water is being provided by a common fire engine.

If temperatures and internal pressure cannot be significantly lowered soon, the likelihood of a fractured reactor barrier is increased. If the reactor shell cracks, the internal water will vaporize, creating conditions for uncontrolled fission and massive radioactive releases into the atmosphere.

Over the past 24 hours, the evacuation area for local residents has been widened from a diameter of three kilometers to 20 kilometers (12.4 miles). Over the same time period, outdoor radiation levels have risen from eight times higher than normal to 20 times higher, according to the monitoring station near Fukushima No.1.