Japanese Nuclear Crisis

March 15, 2011

Q1: How bad is the damage to Japan’s nuclear power plants from the earthquake?

A1: Japan operates 54 nuclear power reactors that provide about 30 percent of Japan’s electricity (compared to the United States’ 104 plants providing 20 percent of total electricity). Eleven reactors automatically shut down with the tremendous earthquake on March 11. These reactors are at four sites in the areas struck by the earthquake. Shutdown is the first and very important step in reactor safety. Many nonnuclear electricity generating stations (thermal, hydro, etc.) also shut down, particularly in the northeast of Japan. The critical difference is that nuclear reactors require continuous power after a shutdown to cool the radioactive fuel.

Of the 11 that shut down, one had a fire (Onagawa), four had hydrogen explosions (Fukushima Daiichi 1, 2, 3, 4), and fuel may have partially melted in the Daiichi units 2 and 3.  With the hydrogen explosions, the secondary containment buildings are no longer intact to keep in radiation that might be released from the steel containment structures, which appear so far to be intact. There is a concern about the integrity of the primary steel containment of Daiichi Unit 2. Unit 4, which had been shut down for maintenance, experienced a fire near the spent fuel pond and an explosion that Japanese officials have attributed to combustible hydrogen. Officials are cooling the cores of the reactors with seawater, a last resort. Efforts to keep Unit 2 cool with seawater previously ran into trouble. It is unlikely that these reactors will operate again. 

Q2: How does this compare to Chernobyl or Three Mile Island?

A2: This is not a Chernobyl. The 1986 Chernobyl accident—rated “7” on the International Nuclear Events Scale (INES), which runs from 1 to 7—started out as a power surge during a test that escalated out of control because of a flaw in the reactor design. The lack of a containment structure around the reactor worsened the radioactive contamination, and cleanup continues today at Chernobyl. At Three Mile Island, the reactor was shut down and containment held, despite partial core meltdown. In Japan, it appears that there are risks at four of the six reactors at the Fukushima site. Fukushima is now considered a “4” on the International Nuclear Events Scale (compared to a “5” for Three Mile Island).

The situation in Japan is much more like Three Mile Island, where a partial core meltdown occurred because of loss of coolant. Radiation levels have risen, not just within the facilities but also at the perimeters, and there have been at least a dozen confirmed cases of radiation exposure. The detection of Cs-137 in the air suggests the fuel has partially melted in some of the reactors. Increased radiation at the facilities makes already difficult conditions even more so and workers’ exposure must be limited. 

Q3: What does this mean for citizens of Japan and for the future of nuclear power in general?

A3: The government of Japan has evacuated citizens in a 20-kilometer zone around the Fukushima Daiichi and Daini plants to minimize the potential health threats. Some radiation levels are being detected in Tokyo. It is too soon to tell what impact this will have on nuclear power in Japan, in light of the tremendous challenges of responding to the devastation caused by the earthquake, tsunami, and aftershocks. Japan was planning build nine new reactors by 2020 and another five by 2030.

Sharon Squassoni is a senior fellow and director of the Proliferation Prevention Program at the Center for Strategic and International Studies (CSIS) in Washington, D.C. Jane Nakano is a fellow with the CSIS Energy and National Security Program.

Critical Questions is produced by the Center for Strategic and International Studies (CSIS), a private, tax-exempt institution focusing on international public policy issues. Its research is nonpartisan and nonproprietary. CSIS does not take specific policy positions. Accordingly, all views, positions, and conclusions expressed in this publication should be understood to be solely those of the author(s).

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