Japanese Nuclear Crisis Continues: An Update
April 14, 2011
Q1: Do we know the full impact of the accident at the Fukushima Daiichi nuclear power plants?
A1: The crisis continues one month after the first huge earthquake and tsunami that devastated Japan on March 11. Subsequent earthquakes, often called “aftershocks,” have resulted in temporary losses of off-site electricity to some nuclear power plants, but without the drastic consequences that triggered reactor core meltdowns at the Fukushima Daiichi power plant.
The full extent of the damage to Units 1 through 4 at Fukushima Daiichi (there are 6 in total) will likely not be known for years. This was true in the case of damage at the U.S. nuclear power plant at Three Mile Island in 1979, where half of the reactor core was discovered to have melted. Levels of radiation and the detection of certain radioactive isotopes offer clues, but not conclusive evidence. Experts estimate that fuel was exposed and partially melted in three of the Fukushima reactors (Units 1, 2, and 3) and in at least one spent fuel pool (Unit 4). Hydrogen explosions destroyed the secondary containment buildings at three units (1, 3, and 4), releasing radiation. The primary containment of the Unit 2 reactor is believed to have been breached. Radioactive water has leaked into the ocean. Although seawater was injected into at least two reactor cores and spent fuel ponds as an initial stopgap measure to provide cooling, officials have switched now to using fresh water to limit corrosion. It is not clear this can reverse the negative effect of salt on the cooling capacity of the plants. Off-site electricity is now available, but many of the cooling systems are not working. In short, the challenges for Japanese officials continue.
Q2: Is this as bad as Chernobyl?
A2: The Japanese government recently raised its assessment of the nuclear accident from a 4 to a 7 on the International Nuclear Events Scale (INES), which runs from 1 to 7. Three Mile Island was rated a 5; Chernobyl was rated a 7. The rating system roughly addresses the scope of the accident, releases of radiation, and the kinds of measures required to respond. Although this incident is on par with Chernobyl, it is still very different. At Chernobyl, the lack of containment and a graphite fire that raged for days meant widespread radioactive contamination that continues to be a problem today. Since the crisis in Japan is not yet over, there is no way of knowing how extensive radiation releases will be, but they have not been as severe as at Chernobyl. The Japanese government began to evacuate residents in a 20-kilometer zone around the Fukushima Daiichi and Daini plants soon after March 11, and it has recently ordered a number of communities outside of this zone to prepare for evacuation.
Q3: When can we expect this crisis to end?
A3: Japanese officials have said it may be months before automatic cooling systems are functional. Radiation levels continue to make recovery efforts difficult. Four of the six reactors at the site are unlikely to operate again. Once cooling is under control, the bulk of efforts will focus on ensuring that the reactors securely contain radiation. This will be a long, expensive effort for Japan.
Sharon Squassoni is a senior fellow and director of the Proliferation Prevention Program at the Center for Strategic and International Studies in Washington, D.C.
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