Washington ? The Nuclear Regulatory Commission on Tuesday required makers of new nuclear power plants to design the reactors so they can withstand the impact from a commercial jetliner.

The commission’s approval of the regulation concludes more than two years of deliberations over the potential threat of a large aircraft crashing into a nuclear power plant, an issue that gained attention after the Sept. 11 terrorist attacks.

The rule approved by the NRC in a 4-0 vote requires that the design of new reactors ensures that if an aircraft crashed into the plant, its rector containment would remain intact, cooling systems would continue to operate and spent fuel pools would be protected.

“This is a commonsense approach to address an issue raised by the tragic events of Sept. 11, 2001,” NRC Chairman Dale Klein said in a statement.

The regulation is stronger than a proposal considered by the NRC two years ago that called on manufacturers to consider how they might address the risk from an aircraft impact but required no specific standards or design changes.

This regulation adds “concrete criteria … which plant designs must meet to demonstrate compliance,” said Commissioner Gregory Jaczko, who had voted against the initial proposal as being inadequate.

The regulation will be incorporated in the certification of three new reactor designs before the commission. While no new reactor has been built for years, the NRC has received 17 applications for 26 reactors with additional ones expected in the months ahead.

The newly approved regulation does not apply to the 104 commercial reactors now operating.

In December, the NRC required operators of reactors now in use to develop strategies and response procedures to mitigate the damage from a large fire or explosion including one caused by impact from a jetliner. But it required no design changes to increase a reactor’s protection.