I worked at the second largest operating one in the country here in New Jersey. It is the one owned by PSE&G, Salem/Hope Creek Nuclear Plant. I worked for security, so I have much knowlegde about nuclear power plants and the security. I worked there for 5 years. First off most Nulclear plants where you see those big Towers with steam coming out of them, they are called cooling towers. That is the design of Hope Creek. Three Mile Island is the same. They are virtually useless to attack. The reactors are deep underground for both. Salem is a little different. The cooling system and reactor are are contained inside a ball. Trust me when I say this, no plane is going to penetrate those balls. They are more than 20 feet thick reinforced concrete and steel. They were designed to withstand a missle blast. But they were designed 20 years ago. Outside of flying in it would be almost impossible of breaking the perimeter without being found out. Any breach, the reactor places and critical areas will be protected and shutdown if necessary. The entire perimeters are protected by microwave alarms. The gap between the inner fence and outer fence is too large to pole vault over. All of the critical places are protected by huge steel doors. Most are deep under ground. The control centers where the operators are, are enclosed in thick glass and steel. Outside of a grenade or small rocket launcher you can forget getting in. There are armed guards on site. Nothing gets in or out. Every vehicle is checked inside, outside, and even under. The detectors where people enter detect metal and chemicals for explosives. The xray machines are powerful enough to literrally look through a human body. It would have to be an inside job. And the only way is to get the reactors to over heat. But they are programmed to shut down regardless if anything goes astray. Trust me the Nuclear Plants are like fortresses. And even for an inside job, it would have to be more sophicated than the airplanes. Many floors and places where some damage could be done are just not accessible. There are many many guards on site. Just to work there you'll go through a background check like the the FBI. It would be extremely difficult to attack a Nuke plant. Just so many layers of security. But I will say this if by some stroke of genius some one did blow up, just bend over and say goodbye. The Nuke plants here are generating far more power than the one is Russia that leaked. But they are without question one of the most safest places against terrorism or public harm. Hell the danger with them is those elctromagnetic waves from the power lines leaving the Nuke plant. My knowlegde is limited to that of here in NJ, but the NRC makes sure that all Nuke plants operate under very strict guidelines. I mean very strict guidelines.