The federal Nuclear Regulatory Commission staff Thursday fined the Sacramento Municipal Utility District $50,000 in connection with a leak last June of 16,000 gallons of radioactive water inside the Rancho Seco nuclear power plant's reactor building.
The leak from a weld in a reactor coolant gas venting pipe was caused in part by the utility's failure to correct engineering problems first called to its attention in 1981, NRC spokesman Greg Cook said.
Cook added that there never was any danger to the public or personnel at the power plant, located 25 miles southeast of Sacramento.
The June 23 leak, which was discovered by employees of the utility district, occurred in a venting pipe that was installed in response to the March, 1979, accident at the Three Mile Island nuclear power plant near Harrisburg, Pa.
Cook described the Rancho Seco plant as a "sister plant" to Three Mile Island because it was also designed and built by Bechtel Corp.
The pipe allows plant operators to remove gases from the reactor coolant system to prevent pressure from building up, exploding and possibly resulting in a meltdown of the reactor's nuclear core.
At the time of the leak, utility district spokesman Brad Smith said, the plant was in the process of starting up, there was no gas in the pipe and the radiation level in the water was relatively low.
"If it had to happen, it happened at a good time," Smith said.
But Cook added, "It's certainly our opinion that the vibration that caused that weld to crack would not have occured" if the utility district had carried out corrective action first suggested in 1981 by the Bechtel Corp. Cook said that failure was inadvertent.
The leak prompted inspections of 349 pipe supports intended to enable the plant to withstand a major earthquake. The utility district discovered that 223 of them were incorrectly placed and two were not installed at all.