There are no data indicating that one nuclear reactor design is safer than another. In the United States, 69 of the 104 operating nuclear reactors are pressurized water reactors. The other 35 are boiling water reactors. Each design has multiple layers of protection (defense-in-depth) and both designs have performed safely and reliably. They both are licensed by the independent Nuclear Regulatory Commission and operated to the same levels of regulatory requirements and safety. The accident at Three Mile Island involved a pressurized water reactor; the Fukushima nuclear energy accident involved boiling water reactors.
The recent accident in Japan was based on a total loss of electrical power including offsite and onsite A.C. power and onsite D.C. power, triggered by a historically massive earthquake, followed by a very large tsunami. In the United States, reactors are designed and licensed for anticipated natural hazards that they are likely to encounter, including earthquakes, floods, hurricanes, and tornadoes (see NEI’s fact sheet on emergency preparedness at nuclear energy facilities).
There is still a great deal that must be learned about Fukushima Daiichi before conclusions can be developed. As information about the accident in Japan is analyzed and the root causes are determined, the industry will work to make U.S. nuclear energy facilities even safer.
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