Duke Energy Progress has discovered a hairline fracture in the reactor head at the Shearon Harris Nuclear Power Plant, Unit 1, in New Hill, NC, the company revealed in a regulatory filing. Duke says the quarter-inch crack near a nozzle that penetrates the reactor head, poses no threat to safety or to the environment. It was discovered during the plant's current refueling shut-down.
The most newsworthy aspect to the discovery is in hindsight. The crack is similar to a small crack that was missed during 2012 refueling and inspection shutdown, but was discovered in May 2013, when technicians were reviewing plant data.
Duke Energy Power, subsequently, shut down the Westinghouse Three-Loop pressurized water reactor 20 miles southwest of Raleigh for a month-long inspection and repair. The Nuclear Regulatory Commission reacted by instigating steps to ensure the company would catch such fractures in the inspection process.
The plant's manager's plant vice president Ernie Kapopoulos at the time noted that the crack in the six-inch thick vessel head was not dangerous, but missing the crack, given that's what the inspection was looking for, was problematic.
There are 65 nozzles in the vessel head of the reactor and in the 2012 shutdown, Duke, using ultrasound, found and repaired four, while missing the fifth one, which was a quarter of an inch long.