> Computed risks for new reactors are lower than for current designs "when only internal events are considered," according to a 2009 report that the Nuclear Energy Institute wrote for the NRC. (That includes fires or pipe breaks, for example.) But when risks of damage caused by external events — earthquakes, for example — are factored in, the new reactors are no safer than older reactors. In addition, because utilities have no operating experience with the new reactors, the probable risk assessments are purely theoretical and not as reliable as years of actual operating data from existing plants.
> The new designs are engineered only to withstand a predictable sequence of events, something engineers theorize may happen. In nuclear parlance that is called a "design basis accident." The new reactors, like their older counterparts, are not designed to survive an unexpected sequence of events. That is the critical flaw, says Lyman: "Three Mile Island was a beyond-design-basis accident."