Crucial components that contain high-pressure, radioactive water at the San Onofre Nuclear Generating Station are, in many places, nearly too worn to function, said an Nuclear Regulatory Commission spokesman.
There is no danger to plant workers or the public because both reactors at the San Onofre station are shut down-- and .
But, the components are only one to two years old and cost hundreds of millions of dollars, raising troubling questions about their functioning.
The plant is producing no electricity. As crews are assessing and planning repairs to leaks at Unit 3 at the plant, the unplanned shutdown, an expert told KPBS, is costing Southern California Edison from $600,000 to $1 million per day.
Problems have been identified in the heat-exchanger tubes that boil water in the steam generators at the plant; there are two generators in each of the two reactors at the plant.
The high-pressure, superheated, radioactive water that runs through the tubes has started to wear through walls of the heat exchangers.
"They've looked at about 80 percent of the tubes in Unit 2," said NRC spokesman Victor Dricks. "Two of the tubes have more than 30 percent wear and have to be plugged and taken out of service. Sixty-nine others have more than 20 percent wear. Over 800 others have less than 20 percent wear, but more than 10 percent."
These aren't the leaky tubes that caused the Tuesday shutdown of Unit 3 at the San Onofre plant, but the same component at Unit 3 has been isolated as the site of the leak.
Unit 2 has been shut down to replace the massive turbines and reactor head at the unit. The wear was detected as part of the routine inspection of equipment that technicians conduct before restarting the reactor, whether for a routine refueling outage or for refurbishments like the turbine replacement.
A spokesman for Mitsubishi, the manufacturer of the components in question, issued a statement Monday saying they were assissting Southern California Edison crews in assessing the damage.
“Mitsubishi is aware of the issue reported at the San Onofre Nuclear Generating Station and has been in contact with the customer, Southern California Edison," said Mitsubishi spokesman Pat Boyle. "The investigation of the incident is being conducted by our customer. However, as the manufacturer of the steam generators, we will do whatever we can to support our customer in resolving the issue.”
The damage raises questions about possible flaws in , but there are dozens of factors that could be involved. Contractors installing the equipment, shipping personnel and plant staff all have roles to play in the installation and operation of the steam generators.
Mitsubishi representatives are on-site consulting as Southern California Edison crews investigate the damage.
"They [SCE] are talking with the manufacturer," Dricks said. "It's unusual. They'll have to determine what caused it."
The tubes are heat exchangers. The nuclear fuel rods super-heat water within a primary system. This water runs through these hundreds of tubes, set up like a car radiator, at a pressure of about 2,500 pounds-per-square-inch.
The heat boils water in a secondary system that makes steam to turn giant turbines. The electricity generated by San Onofre can power more than a million homes at any given time.
San Diego Gas & Electric owns a significant stake in the plant, but SCE is charged with maintaining and operating it.
EDITOR'S NOTE: This story was updated Feb. 6, 2012 with comments from the Mitsubishi spokesman.