ALTHOUGH THE CONSTRUCTION OF ANY new nuclear plant is at least a decade away, power plant owners are slowly adding to the fleet in small increments. A way to increase nuclear generation without turning one spade of dirt has been quietly going on for more than 30 years. The pace of its use has quickened. And while the drive to use it will eventually increase electric generation from that source by the equivalent of building about eight new plants, the window for making those increases will start to close long before a single watt is drawn from any of the plants now formally proposed or contemplated by utilities across the country.

Nuclear power uprates have been the quiet partner in increased generation capacity at many of the nation's fleet of 104 reactors. But the frequency and amount of uprates has fluctuated significantly from practically no added generation in a given year, to perhaps as much as 1,000 megawatts in others.

A review of applications before the Nuclear Regulatory Commission and some companies’ recent actions reveals that the United States appears to be in the middle of a resurgence of nuclear power uprates. But that resurgence will last only a few more years until all the potential capacity gains have been obtained.

At the forefront of this recent resurgence has been Exelon, the largest nuclear generator in the United States, with 17 generators with a capacity of nearly 17,000 megawatts. In the past decade, its uprate program has added the equivalent of 1,100 megawatts.

And that's barely halfway through an aggressive outlay that will cost an additional $3.5 billion and that will add another 1,300 megawatts of capacity by 2017. Altogether, about 2,400 megawatts will have been added during the 18 years of the effort, the equivalent of two new plants. Exelon is still seeking to add plants to its fleet, so power uprates are the only short-term option it has to ramp up capacity.

“It's part of our overall strategy for our low-carbon roadmap that we have laid out through 2020,” said Shelley Keller, vice president of strategic initiatives for Exelon. That plan includes a reduction in Exelon's carbon footprint to 2001 levels by 2020. Exelon successfully completed a 38-megawatt uprate this past June at its Quad Cities plant in Illinois.

Economics is another factor driving the process. An uprate typically has an overnight cost of about $2,200 to $2,500 per kilowatt, or about half of the optimistic scenarios that peg new nuclear construction at $4,500 per kilowatt. Time is also a critical factor, with most individual projects taking in the neighborhood of three to five years to complete, including regulatory review. “We see uprates as a very important part of our overall strategy. It gives you a lot of bang for the buck,” Keller said.

Through dozens of uprates using efficiency gains, technological improvements and regulatory changes, power plants can increase their output from 2 percent to 20 percent based on a variety of factors.

The industry has performed most of its uprates during the past 15 to 20 years as technology has improved. To increase the power output of a reactor, typically a utility will refuel a reactor with either slightly more enriched uranium fuel or a higher percentage of new fuel. The reactor produces more thermal energy – more steam – to drive the turbine. Plant components such as pipes, valves, pumps, heat exchangers, electrical transformers and generators must be able to accommodate the stresses that exist at the higher power level.

Industry pros now say the process is well more than halfway complete – barring some events not now contemplated. “There have been about 5,000 megawatts added to the capacity of the fleet, and with what we see in front of the Nuclear Regulatory commission, there could be another 3,000 to 4,000 megawatts added,” said Tony Pietrangelo, senior vice president and chief nuclear officer of the trade group Nuclear Energy Institute. “Barring some technological breakthrough or different licensing basis, then we believe we will be maxed out.”

The process is by no means a replacement for new nuclear, but should only be seen as an adjunct to the existing fleet, Pietrangelo said.

The number of uprates began very slowly in the late 1970s and occasional increased in the 1980s. Activity picked up considerably in recent years and is expected to increase even more rapidly into the next decade. NRC approved five uprates from mid-2008 to mid-2009 and has 10 pending applications. It expects to receive another 38 power uprate applications during the next five years.

As in any modification of a plant's operating license, the NRC has to sign off on the project, which could take 12 to 18 months, depending on the complexity of the proposed uprate, according to Scott Burnell, spokesman for the NRC. “There's been more of a dialogue. We have gone back and forth with the applicants to work out the details. I'm not aware of any outright refusal,” Burnell said, though there has been an occasional withdrawal of an uprate proposal.

FPL is planning to increase the generating capac ity of its four existing nuclear units at Turkey Point and St. Lucie in Florida by an additional 100 megawatts each. A determination of need petition filed by the company was approved by the Florida Public Service Commission in early 2008 and also received approved site certification from the Florida Department of Environmental Protection. FPL plans to submit license amendment requests by the end of 2009 with NRC review and approval expected later this year. In the 2008–2009 reporting year, five approvals were granted to generators, including Comanche Peak units 1 and 2, part of Luminant Generation in Texas, and Millstone 3 in Connecticut, owned by Dominion. The total addition is more than 200 megawatts of capacity to the nuclear fleet.

Brown's Ferry units 2 and 3 of the Tennessee Valley Authority have projects nearing completion that will add 250 megawatts of capacity. Another pending application for a significant upgrade is at Point Beach units 1 and 2 on Lake Michigan in Wisconsin, owned by FPL.

According to the NRC, there are three categories of power uprates.

Measurement uncertainty recapture power uprates are less than 2 percent. They are achieved by implementing enhanced techniques for calculating reactor power. This involves the use of state-of-the-art feedwater flow measurement devices to more precisely measure feedwater flow, which is used to calculate reactor power. More precise measurements reduce the degree of uncertainty in the power level, which is used by analysts to predict the ability of the reactor to be safely shutdown under postulated accident conditions.

Stretch power uprates are typically up to 7 percent and are within the design capacity of the plant. The actual value for percentage increase in power a plant can achieve and stay within the stretch power uprate category is plant-specific and depends on the operating margins included in the design of a particular plant. Stretch power uprates usually involve changes to instrumentation setpoints but do not involve major plant modifications.

Extended power uprates are greater than stretch power uprates and have been approved for increases as high as 20 percent. These uprates require significant modifications to major balance-of-plant equipment such as the high-pressure turbines, condensate pumps and motors, main generators, transformers or a combination of these devices