ATLANTA (AP) - Westinghouse Electric Co. must fix problems with its new nuclear reactor design before regulators decide whether the system can be used for the next generation of nuclear power plants, the chairman of a federal panel said Friday.
The decision threw uncertainty into the timeline for approving Westinghouse's AP1000 reactor design, a decision that had been expected by the end of the year. The nuclear power industry has been reeling since deadly earthquakes triggered a nuclear plant crisis in Japan.
"The NRC will always place its commitment to public safety and a transparent process before any other considerations," U.S. Nuclear Regulatory Commission Chairman Gregory Jaczko said in a statement Friday.
Federal officials cannot license any new nuclear power plants that use the reactor design until they decide the problems have been fixed.
Westinghouse has contracts to build reactors in Georgia, Florida and South Carolina. Utility firms in Alabama and North Carolina earlier submitted applications to the NRC seeking to use the same technology. Four AP1000 reactors are under construction in China.
Westinghouse said it remains confident in its design and will work with the NRC to resolve the issues, none of which the company considered a significant safety problem.
"The AP1000 is a safe, robust design and is worthy of receiving design certification," Westinghouse said in a statement.
NRC officials took issue with the shield building of the reactor design. The building is a concrete-and-steel structure meant to protect sensitive reactor parts from damage caused by a hurricane, tornado or even the impact of a hijacked jetliner.
In recent reports, NRC staffers said Westinghouse did not properly account for the combined stresses of an earthquake coupled with forces caused when materials change temperature.
"We're not saying that represents some huge problem, but it is something that needs to analyzed," NRC spokesman Scott Burnell said Friday.
Regulators also said that Westinghouse incorrectly calculated possible stresses on portions of the plant, including a tank used to hold emergency cooling water and on equipment that protects against radioactive releases in case its main cooling systems fail.
Supporters say the Westinghouse design will be a major improvement in safety because it relies on gravity, not electricity, to run its backup cooling systems. During a crisis, gravity would pull water from a large tank atop the reactor's containment building onto a steel container that surrounds a vessel holding radioactive fuel.
The crisis at the Fukushima Dai-ichi plant in Japan started after a March 11 earthquake and tsunami knocked out the backup generators needed to power its cooling systems.
Federal regulators had earlier questioned the strength of the shield building. While Jaczko said earlier this year that those issues had been satisfied, a prominent engineer in the agency dissented.
U.S. Rep. Ed Markey, D-Mass., praised the NRC's decision to more carefully review the reactor design. The nuclear power critic has called for a moratorium on licensing until regulators can fully study the accident in Japan.
"We must ensure that any nuclear power plant in this country can withstand a catastrophic impact and abides by the absolute highest standards for safety and security," Markey said in a statement.
Meanwhile, the NRC said late Friday that recent inspections of the 104 U.S. commercial nuclear reactors show that all of them are able to cope with power losses or damage to large areas of a reactor site following extreme events such as a natural disaster or terrorist attack.
The report summarizes inspections conducted in response to the nuclear crisis in Japan. The NRC found that all nuclear plants can effectively cool reactor cores and spent fuel pools following events such as an earthquake, fire or flood.
Of 65 operating nuclear plants, 12 had issues during inspections with one or more of the safety requirements imposed after the Sept. 11 terrorist attacks, the NRC said. Many of the discrepancies involved training of plant employees. Three of the 12 plants have resolved the problems and the remaining sites are actively working to resolve issues identified during the inspections, the NRC said.
"Our resident inspectors did a good job spotting problems as well as helping the plants identify areas for improvement," Jaczko said.
The problems included emergency pumps that were missing or did not work, as well as equipment that was stored in areas that could be vulnerable to earthquakes or floods, said Eliot Brenner, an NRC spokesman.