Federal regulators on [December 22] signed off on a next-generation nuclear reactor slated for Florida Power & Light's Turkey Point plant and five other utilities in the Southeast, paving the way for construction of the first new reactors in the U.S. in three decades. The Nuclear Regulatory Commission's approval of the Westinghouse AP 1000 design was a major milestone for the nuclear power industry, which hasn't built a new reactor since the Three Mile Island accident in Pennsylvania in 1979. Opponents of the AP 1000 ... bristled at the decision. [Some elected officials and] environmental groups ... contend the NRC fast-tracked" the AP 1000 without thoroughly addressing potential safety concerns or incorporating lessons learned from the March meltdown of the nuclear plant in Fukushima, Japan, disabled by an earthquake and tsunami. Arnie Gunderson, an outside expert ... warned the design might be vulnerable to rust that could cause dangerous holes and cracks in the steel reactor containment vessel - a particular problem in the marine environment of Turkey Point. Another study, commissioned by NC Warn, a North Carolina anti-nuclear group, and Friends of the Earth, argued the safety margin for an accidental high pressure build-up inside the reactor was dangerously slim.