Japanese plant races to contain meltdowns after two blasts; third reactor loses cooling capacity
Gallery: Massive rescue, cleanup efforts underway in Japan: After the earthquake and tsunami, entire towns in Japan are impossible to reach. But search-and-rescue teams are fanning out in what will be a lengthy, complex endeavor.
TOKYO — A second explosion rocked Japan’s seaside Fukushima Daiichi nuclear complex Monday, this time destroying an outer building at unit 3. A Japanese government official separately said that a third reactor at the six-reactor facility had lost its cooling capacity, adding to the complications facing the engineers who try to limit the damage of a partial meltdown.
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Video: Days after the devastating earthquake in Japan, damage can be seen for miles at a stretch over Sendai, Japan. It is being estimated that nearly 10,000 people may have died in the quake and subsequent tsunami. (March 13)
The explosion at unit 3 did not damage the core containment structure, and Japanese authorities asserted that there would be little increase in radiation levels around the plant. But the explosion -- a result of hydrogen build-up -- prompted Japan’s nuclear agency to warn those within 12 miles to stay indoors and keep air conditioners off.
The blast injured 11 people, one seriously.
The string of earthquake- and tsunami-triggered troubles at the Fukushima Daiichi plant began with the failure of the primary and back-up cooling systems, necessary to keep reactors from overheating.
On Saturday, a similar explosion occurred at unit 1. Trace amounts of radioactive elements cesium-137 and iodine-131 have been detected outside the plant.
The U.S. Seventh Fleet said on Monday that some of its personnel, who are stationed 100 miles offshore from the Fukushima Daiichi plant, had come into contact with radioactive contamination. The airborne radioactivity prompted the fleet to reposition its ships and aircraft.
Using sensitive instruments, precautionary measurements were conducted on three helicopter aircrews returning to USS Ronald Reagan after conducting disaster relief missions near Sendai. Those measurements identified low levels of radioactivity on 17 air crew members.
The low level radioactivity was easily removed from affected personnel by washing with soap and water, and later tests detected no further contamination.
Like the Saturday explosion at unit 1, the blast at unit 3 took place after a buildup of hydrogen was vented by the reactor. The hydrogen was produced by the exposure of the reactor’s fuel rods and their zirconium alloy casing to hot steam.
In normal conditions, the fuel rods would be covered and cooled by water.
The explosion occurred as Tokyo Electric entered day four of its battle against a cascade of failures at its two Fukushima nuclear complexes, using fire pumps to inject tens of thousands of gallons of seawater into two reactors to contain partial meltdowns of ultra-hot fuel rods.
The tactic produced high pressures and vapors that the company vented into its containment structures and then into the air, raising concerns about radioactivity levels in the surrounding area where people have already been evacuated. The utility said that at one of the huge, complicated reactors, a safety relief valve was opened manually to lower the pressure levels in a containment vessel.
But the limited vapor emissions were seen as far less dire than the consequences of failure in the fight against a more far-reaching partial or complete meltdown that would occur if the rods blazed their way through the reactor’s layers of steel and concrete walls.
The potential size of the area affected by radioactive emissions could be large. A state of emergency was declared briefly at another nuclear facility, the Onagawa plant, after elevated radioactivity levels were detected there. Later, Japanese authorities blamed the measurement on radioactive material that had drifted from the Fukushima plant, more than 75 miles away, according to the International Atomic Energy Agency.
The IAEA noted that forecasts said winds would be blowing to the northeast, away from the Japanese coast, over the next three days.
Tokyo Electric said radioactivity levels inside the plant and at its nearby monitoring post were higher than normal. Although levels had fallen Sunday, the Kyodo News Agency said that radiation at the plant’s premises rose Monday over the benchmark limit of 500 microsievert per hour at two locations, measuring 751 microsievert at the first location at 2:20 a.m. and 650 at the second at 2:40 a.m., according to information Tokyo Electric gave the government. The hourly amounts are more than half the 1,000 microsievert to which people are usually exposed in one year.
In addition to one worker hospitalized for radiation exposure, two others felt ill during stints in the control rooms of Fukushima Daiichi units 1 and 2.
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 an explosion Saturday destroyed a building housing the reactor, the spent fuel pool, in accordance with General Electric’s design, is placed above the reactor. Tokyo Electric said it was trying to figure out how to maintain water levels in the pools, indicating that the normal safety systems there had failed, too. Failure to keep adequate water levels in a pool would lead to a catastrophic fire, said nuclear experts, some of whom think that unit 1’s pool may now be outside.
“That would be like Chernobyl on steroids,” said Arnie Gundersen, a nuclear engineer at Fairewinds Associates and a member of the public oversight panel for the Vermont Yankee nuclear plant, which is identical to the Fukushima Daiichi unit 1.
People familiar with the plant said there are seven spent fuel pools at Fukushima Daiichi, many of them densely packed.
Gundersen said the unit 1 pool could have as much as 20 years of spent fuel rods, which are still radioactive.
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