I got a fourth response to my postings on nuclear energy. This was from a guy named Pete. He provided two links. The first is to a news release by the Nuclear Energy Institute dated December 23, 2002. The NEI used computer modeling techniques (related to what I did with my former employer) to study what would happen if a commercial aircraft was flown into a nuclear reactor. They used a variety of strike points on the reactor and on the airplane. In all simulations, the containment vessel was not breached. There was no leaked radiation. Even though reactors were built before the idea of using planes as missiles, the reactors were designed to withstand hurricane and earthquake as well as explosions within the reactor. They also studied the pools where fuel and spent rods are stored.
That leaves the engineering geeks among us wondering how the designers of reactors managed to keep things so secure. How about containment vessels with walls four feet thick packed with reinforcing bars. Photo here. Another factor is that reactors are a lot smaller than the World Trade Center and the Pentagon.
So don't allow terrorism to deter us from using nuclear energy as we move away from carbon.
Here's another idea proposed by the nuclear industry (though I don't have the link anymore). Instead of building reactors the size we've come to know, we could also build many reactors that are perhaps 1/100 or 1/1000 of conventional size. A lot harder to hit and a lot less disruptive to local environments.