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Projects

Davis-Besse Nuclear Power Station

View of an old steam generator on the saddle transfer gantry system. View of an old steam generator on the saddle transfer gantry system.
An old steam generator inside a containment building.

Completing a Steam Generator Replacement Project Requires Skill and Customer Collaboration

Owned by FirstEnergy Nuclear Operating Company, Davis-Besse is a pressurized-water nuclear reactor that produces 908 megawatts of electricity, enough to power 450,000 homes without producing greenhouse gasses. Maintenance on nuclear power plants is complex and critical to their safe, ongoing operations. When done correctly, it extends a plant’s operating life by decades. 

FirstEnergy selected Bechtel to replaced the two “once-through” steam generators and the reactor vessel closure head at Davis-Besse Nuclear Power Station near Oak Harbor, southeast of Toledo, Ohio. 

The generators function as heat exchangers, producing the steam that drives the turbine generator. Each of the new steam generators for Davis-Besse weighs 550 tons. Bechtel was the original architect engineer for Davis-Besse when the plant was constructed in the 1970s. We also performed the Davis-Besse head replacement in 2002 and the Beaver Valley Unit 1 steam generator replacement in 2006

During the course of more than 30 years, Bechtel has set records for the lowest radiation exposure, shortest replacement outages, and best employee safety performing its steam generator replacement work.

View of an old steam generator on the saddle transfer gantry system.

The Replacement Process

In the world of steam generator replacements, crews must work amid radiological conditions and space constraints that change as the project evolves. Because access is so tight, welding can be particularly difficult. Workers also must contend with hot pipes, and dust and smoke must be controlled. All of this puts a premium on safety and planning.

For the Davis-Besse job, which required 500 workers, Bechtel performed its usual training beforehand on a mockup of the unit to ensure that craft workers are proficient in containment vessel cutting, welding, and post-weld heat-treating.

Extending Plant Life

Plant owners can prolong a generator’s life with enhanced maintenance and testing programs, but they often discover that it’s less expensive to replace them. Enhanced maintenance efforts can cost millions of dollars over time and result in additional radiation doses for plant workers who must come in contact with the equipment. Frequent repairs also can place the plant at risk for an unplanned outage.

Bechtel was architect-engineer for the original two-unit Davis-Besse facility, completed in 1978. The relationship between Bechtel and owner FirstEnergy expanded to include operating plant support for Davis-Besse Unit 1 as well as the utility’s other nuclear plants, including Perry Unit 1, also in Ohio, and Beaver Valley Units 1 and 2, in Shippingport, Pennsylvania. 

When Davis-Besse’s reactor pressure vessel closure head needed replacement in 2002, First Energy trusted Bechtel to complete the project — the first such replacement in the United States. FirstEnergy later tapped Bechtel to perform a steam generator replacement at Beaver Valley Unit 1 in 2006. 

How does a steam generator work?

Steam generators use heat from a nuclear power plant’s reactor core to create steam, which drives the plant’s turbines to create electricity. 

Each steam generator contains thousands of alloy tubes through which hot radioactive water is pumped under high pressure. This process prevents the water from boiling. As the water flows through the tubes, it heats nonradioactive water outside the tubes to make steam.

A typical steam generator has more than 3,000 alloy tubes. The tubes are expected to last for about 40 years, but metallurgy and water chemistry issues often shorten their useful lives considerably. When about 15 percent of these tubes have corroded, a plant suffers from significant maintenance costs and the inability to maintain full power.

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