Progress Energy has won a second extension of time to bolster the physical security of the Shearon Harris nuclear plant in Wake County as the company works to meet tougher standards imposed in the wake of the 9/11 terrorist attacks.

The U.S. Nuclear Regulatory Commission this week gave Raleigh-based Progress until Nov. 30, 2011 to make the required security upgrades -- 19 months after the original deadline of March 31, 2010 -- at the nuclear plant less than 25 miles southwest of Raleigh.

"One reason this was justified is that there were a limited number of vendors who could do the work and they were busy at numerous plants," said NRC spokesman Joey Ledford.

Nuclear plants are considered prime targets for a terrorist attack. A successful attack could cause a radioactive release, spread widespread panic, trigger emergency evacuations and paralyze a major economic region of the country.