EPRI Nuclear Plant Structural Studies
[Source: NEI InfoWire, June 18]
The Nuclear Energy Institute is releasing preliminary results of an EPRI (Electric Power Research Institute) study that claims that reactor containment buildings would withstand credible aircraft crash scenarios proposed in the aftermath of 9/11:
"- The industry is very confident that the containment building would safely protect the reactor in the unlikely possibility that a commercial airliner is used as a weapon against nuclear power plants. Preliminary results of an industry study indicate that a commercial aircraft like that used in the Sept. 11 attacks would not likely penetrate the robust containment buildings where the reactor is located. Neither the mass of the aircraft nor the engines would likely penetrate the containment building.
- EPRI performed the studies of nuclear plant structural strength at the request of the Nuclear Energy Institute. Four engineering companies performed the engineering studies: ABS, Environmental Qualification Engineering, Erin Engineering, and Fauske and Associates. These companies are recognized industry experts in structural analysis. The results of the studies are being reviewed by an industry task force and are expected to be final by the end of June. Details of the report will not be distributed publicly due to the sensitive nature of the information, however the Nuclear Regulatory commission will be briefed on the results.
- The study did not analyze every type of containment structure, but used a containment building that is representative of a typical containment structure at nuclear power plants.
- The study evaluated the impact of a Boeing 767 - the aircraft used in the Sept. 11 attacks - and engineers are confident that containment buildings can safely protect the reactor against most commercial aircraft (including 757s and 777s). Assuming the low profile of nuclear power plants relative to the World Trade Center the study used the aircraft ground speed and angles associated with the Pentagon attack. That is the most realistic scenario in the unlikely event that an airliner is hijacked and used to attack a nuclear power plant. Given the ground forces at low altitude, a pilot could not accurately fly an aircraft at the speed of the World Trade Center attacks and target structures low to the ground like nuclear power plants.
- Given the angles at which aircraft would have to fly to strike containment buildings, the containment dome would only receive a glancing blow. It is virtually impossible for a skilled pilot to control a commercial aircraft in a steep dive that could hit a containment structure at the top of the containment dome. In fact, the wings of commercial jets likely would sheer off of the plane in such a steep dive a high speeds. Moreover, pilots cannot precisely control a large commercial aircraft at that steep dive angle.
- Spent fuel storage vaults at nuclear power plants also would be protected from direct aircraft crashes. Walls of spent fuel vaults typically are even thicker than reactor containment walls. All plants have this robust protection of concrete walls around their fuel vaults. The study also analyzed a 767 hitting a spent fuel vault, and although there is significant damage to the 4-foot to 5-foot thick concrete walls of the vault, the stainless steel liner of the vault remains intact and protects the used reactor fuel. Because the concrete walls absorb most of the energy from the aircraft, there is no penetration of the stainless steel liner that could cause a breach of the vault. There is not drainage of cooling water out of the vault in this scenario. The impact of an airliner on nuclear fuel dry storage containers is still being evaluated.
- The study also considered the consequences should auxiliary buildings at nuclear plants be struck by a commercial airliner. These buildings typically are 18-inch thick reinforced concrete. A commercial aircraft would penetrate the exterior walls of these structures, and the resulting damage to some plant systems would depend on he specific location and interior structure of the building. In any event, the availability of redundant and diverse safety equipment at other locations at the plant could be used to safety shut down the reactor."