WASHINGTON—Structures that house reactor fuel at U.S. nuclear power plants would protect against a release of radiation even if struck by a large commercial jetliner, according to analyses conducted over the past several months by the Electric Power Research Institute (EPRI).
The independent analyses were conducted at the request of the Nuclear Energy Institute.
State-of-the-art computer modeling techniques determined that typical nuclear plant containment structures, used fuel storage pools, fuel storage containers, and used fuel transportation containers at U.S. nuclear power plants would withstand these impact forces despite some concrete crushing and bent steel.
The computer analyses, which cost more than $1 million, are summarized in a report entitled, “Deterring Terrorism: Aircraft Crash Impact Analyses Demonstrate Nuclear Power Plant’s Structural Strength.” A summary of the study’s findings is accessible on NEI’s web site at http://www.nei.org.
“The results of this study validate the industry’s confidence that nuclear power plants are robust and protect the fuel from impacts of a large commercial aircraft,” said Joe F. Colvin, NEI’s president and chief executive officer. “Clearly an impact of this magnitude would do great damage to a plant’s ability to generate electricity. But the findings show, far more importantly, that public health and safety would be protected.”
The study was performed for EPRI by ABS Consulting’s Irvine, Calif., office and by San Diego-based ANATECH. It was peer reviewed and critiqued as the computer modeling was being done by internationally recognized experts with decades of experience in structural analysis.
The analysis used several criteria that increased the severity of the crash scenario. Most notable was the assumption that a large aircraft traveling low to the ground at speeds similar to the estimated speed of the jetliner that struck the Pentagon on Sept. 11, 2001, precisely executes a hit that transfers the full impact of the crash to the structure being struck. Separate analyses assumed direct hits by both the aircraft’s fuselage and a 9,500-pound engine. This size engine is typical of the majority of aircraft currently in service; it would envelop engines on 767-400s, 757-300s, 747-400s, 737-800s, DC 10-30s, MD11s, A320-200s, A330-200s and L1011-500s.
The analysis also increased severity by assuming that a Boeing 767-400 would strike at its maximum takeoff weight (450,000 pounds) even though fuel would be consumed both in takeoff and en route to any power plant site.
The nuclear energy industry is confident in the robustness of nuclear plant structures that house reactor fuel to withstand aircraft impacts, even though they were not specifically designed for such impacts.
“This confidence is predicated on the fact that nuclear plant structures have thick concrete walls with heavy reinforcing steel and are designed to withstand large earthquakes, extreme overpressures and hurricane force winds,” the report states.
EPRI served as the technical lead on the study to test the bases for industry confidence in power plant structural strength against aircraft crash impacts. EPRI was founded in 1973 as a non-profit energy research consortium. Its mission is to provide science and technology-based solutions to global energy customers through scientific research, technology development, and product implementation.
The Boeing 767-400 was used for the analysis for several reasons. For example, Boeing aircraft account for almost two-thirds of the commercial aircraft registered in the United States. The Boeing 767 series is the most widely used “wide body” aircraft in the U.S. commercial fleet—with more planes than the 747 and 777 combined—and the 767-400 envelops 88 percent of all commercial flights in the United States employing Boeing aircraft.
Nuclear plant structures are considerably smaller than the World Trade Center towers and the Pentagon, making it physically impossible for both engines and the fuselage of the plane to transfer the full force of impact to the containment building or other facilities analyzed.
The assumed speed of the aircraft used in the study is 350 miles per hour—approximately the speed at which the aircraft struck the Pentagon, based on reported flight recorder data and analysis of security camera video that captured the impact. Experienced pilots say this is a realistic speed to apply in a scenario where the pilot of a large jetliner wishes to maintain flight maneuverability close to the ground and execute a precise hit.
Although full analytical details will not be released to the public for security reasons, NEI announced the following general results:
For the models representing all types of U.S. containment buildings, no parts of the engine, the fuselage, the wings or the jet fuel entered the containment buildings. The containment structure was not breached, despite some crushing and spalling (chipping of material at the impact point) of the concrete.
Evaluation of the models representing both types of used fuel pools determined that the stainless steel pool liner ensures there would be no loss of pool cooling water even though some crushing and cracking of the concrete occurred at the point of impact. Because the used fuel pools were not breached, there would be no release of radioactivity to the environment.
For the analyzed dry fuel storage facilities, the steel canister containing the used fuel assemblies was not breached. Because the dry storage structure was not breached, there would be no release of radioactivity to the environment.
For the analyzed used fuel transportation container, the container was not breached, so there would be no release of radioactivity to the environment.
Representative structures were analyzed because U.S. nuclear power plant construction varies from site to site.
See Deterring Terrorism: Aircraft Crash Impact Analyses Demonstrate Nuclear Power Plant's Structural Strength (EPRI Study)