Nuclear station to get new towers of power
Union Tribune (2009-02-04) M Icheal Burge
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How do you move a 640-ton, 65-foot-tall steam generator 15 miles up the coast?
Over the past three weeks crews moved an enormous generator from Camp Pendleton to the San Onofre Nuclear Generating Station, where it will be installed inside one of the containment domes this fall.
A second generator is on its way from the Marine Corps base, where the two were delivered recently after a trip across the Pacific from Kobe, Japan, to Long Beach.
Officials with Southern California Edison, which operates the 2,200-megawatt power plant in the northwest corner of San Diego County, say the new generators are needed to replace older ones that became obsolete before their expected 40-year life span ends.
Each of San Onofre's two reactors uses nuclear fission to heat water that is circulated in a closed pipe to two steam generators. The heated pipe passes through the generator, which has a separate water system that flashes into steam. That steam drives the turbines that generate electricity.
Each generator is laced with 9,727 tubes.
"The original plant's lifetime was 40 years," said Ross Ridenoure, a Southern California Edison senior vice president and San Onofre's chief nuclear officer.
"What we're seeing is very, very small, microscopic cracks" in the old generators' tubes, Ridenoure said. The water in the generators is not radioactive.
San Onofre has two operating nuclear reactors - units 2 and 3. Unit 1 was shut down in 1992.
The licenses for them expire in 2022 and '23. Ridenoure said Southern California Edison hasn't decided whether to apply for an extension, but given the $670 million investment in four new steam generators - two for each reactor - it appears likely.
The replacement project, including the transportation of the generators up the coast, was the subject of extensive hearings in 2005. The utility needed approval from eight federal and state agencies to undertake the project.
The two replacement generators, manufactured by Mitsubishi Heavy Industries, arrived at Del Mar Basin at Camp Pendleton on Jan. 10.
Then the first of the pair was put onto a vehicle called a "crawler" that carried it eight miles up the beach until it reached the Las Pulgas Road exit of Interstate 5.
There it was shifted to another trailer that took it up I-5, then on frontage roads to the plant. Its top speed was 5 mph.
"(The specialized trailer) has 16 axles and 256 tires," Ridenoure said.
It takes about two weeks for each generator to make that final leg of its journey.
Shipping the generators to the plant will be child's play compared with installing them.
To do that, a 28-foot-wide hole will be cut in each containment dome, the old generators will be taken out and the new generators put in their place.
The domes - gigantic, semi-spherical structures that are the first things southbound motorists visiting San Diego see from I-5 - weren't meant to be breached, Ridenoure said.
The concrete skin on each dome is 4 to 6 feet thick, he said, and is reinforced with steel bars about the diameter of an adult's forearm. The process of cracking the domes is akin to peeling back a skin and dismantling a skeleton.
Then everything will have to be put back the way it was.
Unit 2's generators will be replaced this autumn. Unit 3's new generators will be delivered and installed next year. Each unit will be shut down for about four months while the replacement takes place.
San Onofre has undergone extensive scrutiny recently by the Nuclear Regulatory Commission.
In December, the commission reported that the plant's staff didn't notice that a backup battery for safety systems was inoperable between 2004 and 2008.
Other problems include falsified fire-safety records that the commission made public a year ago. At the time, Edison officials said they had fired or disciplined seven workers for safety and security violations.
Each reactor can generate 1,100 megawatts of electricity when operating at full power, enough to supply 1.4 million households. Southern California Edison owns 78 percent of the plant, San Diego Gas & Electric 20 percent and the city of Riverside 2 percent.
Michael Burge: (760) 476-8230; firstname.lastname@example.org