<P> Current fission reactors in operation around the world are second or third generation systems, with most of the first - generation systems having been retired some time ago . Research into advanced generation IV reactor types was officially started by the Generation IV International Forum (GIF) based on eight technology goals, including to improve nuclear safety, improve proliferation resistance, minimize waste, improve natural resource utilization, the ability to consume existing nuclear waste in the production of electricity, and decrease the cost to build and run such plants . Most of these reactors differ significantly from current operating light water reactors, and are generally not expected to be available for commercial construction before 2030 . </P> <P> The nuclear reactors to be built at Vogtle are new AP1000 third generation reactors, which are said to have safety improvements over older power reactors . However, John Ma, a senior structural engineer at the NRC, is concerned that some parts of the AP1000 steel skin are so brittle that the "impact energy" from a plane strike or storm driven projectile could shatter the wall . Edwin Lyman, a senior staff scientist at the Union of Concerned Scientists, is concerned about the strength of the steel containment vessel and the concrete shield building around the AP1000 . </P> <P> The Union of Concerned Scientists has referred to the EPR (nuclear reactor), currently under construction in China, Finland and France, as the only new reactor design under consideration in the United States that "...appears to have the potential to be significantly safer and more secure against attack than today's reactors ." </P> <P> One disadvantage of any new reactor technology is that safety risks may be greater initially as reactor operators have little experience with the new design . Nuclear engineer David Lochbaum has explained that almost all serious nuclear accidents have occurred with what was at the time the most recent technology . He argues that "the problem with new reactors and accidents is twofold: scenarios arise that are impossible to plan for in simulations; and humans make mistakes". As one director of a U.S. research laboratory put it, "fabrication, construction, operation, and maintenance of new reactors will face a steep learning curve: advanced technologies will have a heightened risk of accidents and mistakes . The technology may be proven, but people are not". </P>

To what extent has fission been used to generate electricity in the us