Atlantic Group employees Jack Scott (left) and Michael Roadcap work inside Unit 2 where a generator is being replaced during this fall's scheduled refueling project.

Workers load equipment into North Anna Power Station Unit 2 during a reactor refueling project. Adding to the magnitude of the job this fall, a new generator will be installed in Unit 2 after 30 years of service.

North Anna Power Station radiological protection personnel Mark Detrick (left) and Trey Perrin monitor work being done inside Unit 2 on Lake Anna in Louisa County.

Refueling a reactor at North Anna plant is a big job, made even bigger when a generator is replaced

Date published: 10/1/2008

By RUSTY DENNEN

Inside North Anna Power Station, technicians remotely monitor the activities of workers wearing white protective suits in what looks like an enormous equipment-filled cave.

A crew works inside the reinforced-concrete dome, or containment area, that houses Unit 2's nuclear reactor on Lake Anna in Louisa County.

Except for certain times such as this, it's off-limits to workers.

Peering at a bank of video screens, Trey Perrin and Mark Detrick keep track of those in the vicinity of the reactor and other radiation sources.

The scene is but one dimension of refueling--a routine but critical task at North Anna and the rest of the nation's 104 commercial nuclear power plants.

Like the family car, nuclear reactors must be refueled. Every nine months, one of North Anna's two 921-megawatt reactors is shut down for that purpose, while other maintenance and repairs are done.

Unit 2's outage began Sept. 15, and the refueling process won't be completed until mid-October.

This refueling is all the more complicated because a massive generator is also being replaced on Unit 2, which began operation in 1980.

ORCHESTRATED EFFORT

Eric Hendrixson, the plant's director of station safety and licensing, says refueling has changed little since the first reactor went online here in 1978, but that technology is making it faster and more efficient.

"You still need to refuel; physics is physics," Hendrixson said. "Rotating equipment still wears out"

The refueling and generator project will take the same amount of time as a typical refueling.

"It's well-planned and orchestrated. It's not something we wake up one morning and say, 'Hey, let's have a refueling outage,'" he said.

"You're laying out large pieces of it, saying, 'OK, we're replacing a generator or turbine, or upgrading components, and we slowly work our way through."

The outage is a window of opportunity for equipment maintenance and testing that can't be done when the reactor is running.

For each refueling, "We bring in anywhere from 1,000 to 1,200 supplemental contract employees"--mechanics, electricians, welders, scaffold builders, for example--who do specialized work, he said. Many travel from one refueling to another throughout the country.

That's in addition to about 850 employees who typically work at North Anna.

North Anna Power Station generates 1,786 megawatts of electricity from its two units--enough to power 450,000 homes. Unit 1 began operation in June 1978 and Unit 2 followed in December 1980. Dominion power, which owns and operates the plant, is planning a third reactor. The station, near Mineral in Louisa County, is named after the North Anna River, which was dammed to create Lake Anna. Its waters are drawn to cool the reactors. --Dominion Virginia Power The fuel for North Anna's two reactors is enriched uranium dioxide, compressed into small ceramic pellets and stacked in metal-alloy tubes called fuel rods. The rods are bundled together in 8-inch by 14-foot fuel assemblies. There are 157 fuel assemblies in each reactor. Reactor shut down and cools to about 100 degrees, plant systems tested. Turbine generator disassembled--4 days. Reactor container lid removed; fuel assemblies taken out and stored in spent fuel pool--4 days. Maintenance and inspections on reactor and coolant system. Turbine generator reassembled with refurbished parts--9 days. New and partially used fuel reloaded in reactor--2 days. Reactor head bolted back on, more tests on plant equipment, operators begin warming reactor--5 days. Restart process continues. Reactor heats up to 547 degrees, coolant system pressurized, turbine generator assembly completed--3 days. Operators start nuclear chain reaction, increase power to 10 percent. Steam begins spinning electrical generator to proper speed--4 days. Turbine generator connected to power grid, reactor slowly raised to full power--4 days. --Dominion Virginia Power

Date published: 10/1/2008