Pournelle's cost numbers are probably low, but he's right that volume and standardized systems would reduce costs. He's also right in that the primary obstacles are political.

A modern nuclear containment vessel is designed to take airplane hits, and there are other methods of defending against that sort of attack. A nuclear facility is neither more or less open to terrorist attack than a chemical refinery, a dam, or any other target whose destruction would cause widespread damage.

The only thing stopping us from using nuclear power as a solution for energy independence, not to mention CO2 issues, is political will.