Japan Nuclear Crisis: Slow Progress with Emergency Cooling Systems
Photo: Gonzalo Déniz, CC
Latest Update: Japan's Nuclear Crisis: 2 Weeks After the Mega-Quake & Tsunami (March 25, 2011)
Big Challenges Remain Before Cooling Can be Fully Restored
While restoring electrical power was a big step forward, there still remains a lot of work to be done before the emergency cooling systems of the Fukushima 1 nuclear power station can be turned back on. The workers on site are doing heroic work under difficult conditions and they have our admiration. Read on for more details on what happened during the past day.
#27 shows the location of the spent fuel. Image: Wikipedia, CC
So now that power is reconnected, the next step is to get the emergency cooling system back in working condition. This means that workers now have to manually drain hundreds of gallons of radioactive water and vent radiactive gas from pumps and pipes, according to the NYT.
Another potential problem will be caused by salt from seawater. When the seawater evaporates, it leaves a lot of salt behind. Richard T. Lahey Jr., who was General Electric's chief of safety research for boiling-water reactors when the company installed them at the Fukushima 1 plant, estimates that around 57,000 lbs of salt have accumulated at unit #1 and close to 100,000 lbs at units #2 and 3. If this creates a crust around the fuel rods, it can insulate them and make them heat up faster than they otherwise would. But it is hard to know exactly how much salt stayed in the reactors since some of the seawater used for cooling has returned to the ocean.
Three workers were exposed to 170 to 180 millisievert of radiation in the underground of No. 3 reactor's turbine building. Two of them were hospitalized for possible radiation burns on their legs, according to Kyodo News. If you look at the radiation chart at the bottom of this post, you'll see that 170-180 millisievert is thankfully below the dose at which radiation sickness starts, but it is still high enough to pose a risk.
Photo: US Navy, CC/U.S. Navy photo by Mass Communication Specialist 3rd Class Kevin B. Gray/Released
Japanese authorities considering importing bottled water from overseas to ease fears about potential tap water contamination caused supplies to become scarce. The latest tests on thursday showed levels of iodine 131 falling to 79 becquerels, which is below the limit for infants in Japan.
It should be noted that the radiation limit in Japan is lower than the international one set by the International Atomic Energy Agency (IAEA), so there's probably a pretty big margin of safety built in, since the IAEA limit itself is probably conservative:
the limits recommended by the Japanese government appeared to be much lower than those of the International Atomic Energy Agency. Japan says older children and adults should get no more than 300 becquerels per liter while the I.A.E.A. recommends a limit of 3,000 becquerels. Greg Webb, an I.A.E.A. spokesman in Vienna, said he could not immediately provide his agency's recommendation for infants. (source)
Meanwhile in the US, the Nuclear Regulatory Commission (NRC) is launching a review of the US nuclear reactors. They will conduct a "short-term and long-term analyses of lessons learned from Japan. The reports also will address how lessons can be applied to the 104 U.S. nuclear reactors."
Previous Updates on Japan's Nuclear Crisis at Fukushima
-March 14: Mini-FAQ About Japan's Nuclear Power Plant Crisis
-March 15: 6 Important Questions About the Crisis at Japanese Nuclear Power Plants
-March 16: Update on Japan's Nuclear Crisis at Fukushima I
-March 17: Ongoing Crisis at Japan's Fukushima I Nuclear Power Plant
-March 18: Japan's Nuclear Crisis, One Week Later
-March 21: Limited Progress Cooling Fukushima's Nuclear Reactors
-March 22: Light at the End of the Tunnel for Japan's Nuclear Crisis?
-March 23: Japan Nuclear Crisis: External Power Reconnected at Fukushima 1
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