From National Public Radio:
Federal regulators knew when they renewed the Vermont Yankee nuclear plant's license last month that electrical cables serving key plant safety systems had been submerged in water for extended periods of time, Nuclear Regulatory Commission documents show.
A nuclear watchdog group says the issue has new urgency following the nuclear disaster in Japan, in which tsunami flooding knocked cooling systems out of service, causing reactors to overheat at the Fukushima Dai-ichi nuclear station.
An NRC report in December said 23 reactors around the country had electrical cable failures between 1988 and 2004, with nine more instances since 2007 of cables improperly being submerged in water.
"Because these cables are not designed or qualified for submerged or moist environments, the possibility that more than one cable could fail has increased," the report said. "This failure could disable safety-related accident mitigation systems."
The agency's documents show it has been concerned about submerged electrical cables at U.S. nuclear plants for years. The cables, usually housed in concrete boxes or small tunnels underground, get wet from rain, melting snow or groundwater, the NRC said.