The NRC's proposed rules are meant to protect new reactors against a deliberate hit by a jet like those that rammed into the World Trade Center and Pentagon on September 11, 2001, the commission said.
"This is the most recent step in a broad, proactive effort to improve the security of reactors initiated by the NRC after September 11," NRC Chairman Dale Klein said.
"We need more technical analysis to understand how to address this.
The proposal would apply to companies that want to build new reactors whose designs have not received NRC certification, a spokesman for the NRC said. It will not apply to the nation's existing 104 civilian nuclear power plants, which already have adequate protection, he said.
The proposal will be made public later this year and could take effect next year, he said.
The proposal is less stringent than one backed by NRC Commissioner Gregory Jaczko, which would have required new nuclear plants to be built to withstand a large commercial aircraft impact.
U.S. utilities have not ordered new nuclear plants in about 25 years due to cost and safety concerns, but the NRC could weigh upward of 20 new applications for the first wave of new U.S. nuclear plants in coming months.
The NRC said it already requires the owners of nuclear reactors to take steps to minimize damage from large fires and explosions from any type of attack.
However, companies that ask the NRC to new approve reactor designs would have to "assess how the design, to the extent practicable, can have greater built-in protections to avoid or mitigate the effects of a large commercial aircraft impact."
"This proposal gives us the chance to assess and make practicable changes to new reactor designs early in the design process," Klein said.
The rules would apply to reactor design proposals submitted by General Electric Co., French-based Areva, and Japanese-based Mitsubishi Heavy Industries the spokesman said.
And even though the rules would not explicitly apply to four new reactor designs already certified by the NRC, it would be "in the interest of both the designers and their clients to adopt these changes at the design stage," Klein said.
The rules would likely require designers to weigh how an aircraft strike would impact the plant operator's ability to keep the reactor core cool enough to avoid a meltdown, and to keep radioactive gases from escaping into the atmosphere, the NRC said.
The Nuclear Energy Institute, which lobbies for U.S. nuclear operators, said the proposal is appropriate, because plant designers already weigh cataclysmic events like hurricanes and earthquakes.