... but your claim appears to be wrong
Vulnerability of US Power Plants to Terrorist Attack and Internal Sabotage
... As early as 1982, the Argonne National Laboratory, a Department of Energy (DOE) facility, conducted a study detailing the likely damage that a jetliner could inflict on the concrete containment walls protecting nuclear reactors. The study described possible scenarios where an accidental jetliner crash could compromise the safety of a nuclear power plant's primary containment wall and interior structure. The report estimated that even if just 1% of a jetliner's fuel ignited after impact, it would create an explosion equivalent to 1,000 pounds of dynamite inside a reactor building. An explosion of this magnitude impacting on a containment structure that has already been weakened by the crash of a high-speed jetliner crash could potentially compromise the integrity of the power plant. While the report refrained from providing detail, in these accident scenarios, about how and when radioactivity might be released, it stated that "the breaching of some of the plant's concrete barriers may often be tantamount to a release of radioactivity" ...
Immediately after the September 11 attacks, the NRC stated that American nuclear power plants could withstand the crash of a commercial jetliner like those used against the WTC and the Pentagon. Within days of this assertion, however, the agency spokesmen found themselves backpedaling and stating that before Sept. 11 the NRC had not considered and prepared for the danger of an aerial attack on U.S. nuclear reactors involving large commercial planes loaded with jet fuel. The agency had no serious contingency plans for such attack because, as the NRC spokesman Victor Dricks stated, "it was never considered credible that suicidal terrorists would hijack a large commercial airliner and deliberately crash it into a nuclear power plant."7
The International Atomic Energy Agency (IAEA) has also confirmed that current nuclear power plants are structurally vulnerable against the September 11 attack scenario that destroyed the World Trade Center Buildings. According to IAEA Spokesman David Kyd, "
Reactors have the most robust engineering of any buildings in the civil sector - only missile silos and nuclear bunkers are built to be tougher. They are designed to be earthquake-proof, and our experiences in California and Japan have shown them to be so. They are also built to withstand impacts, but not that of a wide-bodied passenger jet full of fuel. A deliberate hit of that sort is something that was never in any scenario at the design stage. These are vulnerable targets and the consequences of a direct hit could be catastrophic." In an interview with CNN's Moneyline program, Kyd asserted that successful use of a large passenger airliner to attack a nuclear power plant is a rather unlikely scenario. In the course of the same interview however, Kyd acknowledged that, if such an attack were successfully conducted, "the containment could be breached and the cooling system of the reactor could be impaired to the point where radioactivity might well be set free."8
According to experts, if a large airliner were to hit a nuclear power plant's containment structure, the jet engines could penetrate the structure, leading to the introduction within the building of jet fuel and most likely a severe explosion and fire similar to those witnessed at the WTC and the Pentagon on September 11. Nuclear power plants are not well equipped to deal with severe fires, known as "common-mode failures." Such accidents could actually cause various safety systems to fail simultaneously, leading to a loss of coolant that cannot be mitigated and ultimately resulting in a meltdown of the nuclear fuel ...
http://www.psr.org/home.cfm?id=pressroom18