By Steven Mufson and Chico Harlan, Monday, March 14, 1:50 PM
Japan’s nuclear crisis deepened Monday as utility officials reported that four out of five pumps being used to flood the unit 2 reactor at the Fukushima Daiichi complex had failed and that the other pump had briefly stopped working, hastening the meltdown of fuel rods that at one point were fully exposed.
According to a report by Kyodo News agency, the fifth pump has been refueled and seawater mixed with boron is again being injected in a desperate bid to cool the reactor, but the fuel rods remain partially exposed and ultra-hot. The other four pumps were thought to have been damaged by a blast earlier Monday that destroyed a building at the nearby unit 3 reactor, Kyodo reported.
The new crisis in unit 2 increases the chances of another explosion will take place at the complex as hydrogen builds up in the outer building surrounding the reactor. A similar explosion on Saturday destroyed a building at the unit 1 reactor.
Day four of the battle to regain control of the damaged reactors at the Fukushima Daiichi complex has turned out to be one of the most difficult so far.
Earlier on Monday, the explosion at the unit 3 reactor rocked the seaside nuclear complex. The International Atomic Energy Agency reported that injections of sea water into units 1 and 3 had been interrupted due to a low level in a sea water supply reservoir, but the sea water injections were later restored.
Japanese government officials were quick to assert that the explosion at unit 3 did not damage the core containment structure, and they asserted that there would be little increase in radiation levels around the plant. But the explosion prompted Japan’s nuclear agency to warn those within 12 miles to stay indoors and keep air conditioners off. The blast also injured 11 people, one seriously.
While the hot fuel rods are still encased in six inches of steel, and then inside concrete, and then in a building with layers of steel and concrete, the intense heat they generate could eventually eat through those layers if Tokyo Electric and Japanese authorities do not figure out how to cool the rods. It is impossible to see into the reactor core, so officials are speculating about what is happening inside by using a variety of gauges and indicators.
The string of earthquake- and tsunami-triggered troubles at the Fukushima Daiichi plant began last Friday when a loss of grid power because of the earthquake followed by a loss of backup diesel generators because of the tsunami led to the failure of cooling systems needed to keep reactor cores from overheating.
On Saturday, a similar explosion occurred at unit 1. Trace amounts of radioactive elements cesium-137 and iodine-131 were also detected outside the plant.
The IAEA reported that Japan has now evacuated 185,000 people from towns near the nuclear complex. The agency said that Japan has distributed 230,000 units of stable iodine to evacuation centers from the area around Fukushima Daiichi and Fukushima Daini nuclear power plants. The iodine has not yet been administered to residents; the distribution is a precautionary measure in the event that this is determined to be necessary.
The ingestion of stable iodine can help to prevent the accumulation of radioactive iodine in the thyroid.
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 Power Co. continued 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 IAEA.