Edwin S. Lyman, PhD

Nuclear Control Institute

September 21, 2001






Since the occurrence of the tragic events of September 11, 2001 at the World Trade Center and the Pentagon, there has been considerable concern among the public regarding the ability of nuclear power plants to withstand a direct attack by large, high-speed passenger jets with nearly full fuel tanks. The U.S. Nuclear Regulatory Commission (NRC) does not require detailed reviews of aircraft hazards to nuclear power plants to be carried out except for plants with non-negligible probabilities of being affected by an aircraft crash, i.e. those located near busy airports, military training routes or federal airways.[1] However, even for those plants for which such reviews have been conducted, "the NRC did not specifically contemplate attacks by aircraft such as Boeing 757s or 767s and nuclear power plants were not designed to withstand such crashes," and detailed engineering analyses of a large airliner crash have not yet been performed."[2]


Despite this admitted absence of technical evidence, both the nuclear industry and the NRC have been giving the impression in their public statements that nuclear reactors would be likely to survive such a severe attack. For instance, a Nuclear Energy Institute (NEI) fact sheet states that "reactors at nuclear power plants are enclosed in containment buildings made of steel and reinforced concrete up to four feet thick" and that "inside the containment building, the reactor is encased in a steel pressure vessel up to a foot thick," which "minimizes the risk of penetration from outside forces."


However, a straightforward calculation shows that a large passenger jet like a Boeing 767, colliding into the reinforced concrete containment structure of a typical U.S. nuclear reactor, would in fact have a high likelihood of penetrating the containment.

While certain U.S. reactor designs are more vulnerable than others, all are potentially at risk. Gross structural failure of the containment building is also a possibility, especially for older plants which have experienced age-related degradation of containment materials.


The shock of such an impact would probably cause substantial damage to plant systems inside the containment, and the effect of a subsequent jet fuel fire or explosion would cause further mechanical and thermal damage to the containment, metal reactor components and the reactor vessel itself. Following such an assault, the possibility of an unmitigated loss-of-coolant accident and significant release of radiation into the environment is a very real one.



* Details of the calculation to determine containment vulnerability to penetration by a large commercial jet are being withheld from this version of the report. The full report is being provided to the Nuclear Regulatory Commission, the Nuclear Energy Institute and other appropriate entities.

[1] U.S. Nuclear Regulatory Commission (NRC), Standard Review Plan, NUREG-0800, Sec.

[2] U.S. NRC, "NRC Reacts to Terrorist Attacks," press release 01-112, September 21, 2001.