Exelon’s Approach to Power Uprates
By Craig Lambert, Vice President, Power Uprates, Exelon Corp.
In late 2008, Exelon Nuclear embarked on its second major campaign of power uprates across the nuclear fleet. Prior to this second campaign, Exelon Nuclear had completed uprates of approximately 1,100 MWe over the past 10 years. The initiative started with the performance of a fleetwide conceptual study to determine what uprate was possible at each unit. Exelon owns and operates 17 nuclear units at 10 different sites located in Illinois, Pennsylvania and New Jersey. The study reviewed what prior changes were completed, what additional power increase could be accomplished, pinch point considerations (equipment or systems that had little or no remaining margin) and material condition deficiencies. Cost estimates were developed and economic analyses were performed for various business case scenarios. These scenarios included assumptions if only megawatts.
|In 2009 Exelon announced an uprate of 38 MW at the Quad Cities plant that launched a series of planned power uprates across the fleet. Photo courtesy of Exelon Corp.|
Proposed plans were presented for approval through various corporate committees, with concurrence achieved to embark on the next uprate campaign. The plan outlined which uprate should be initiated for each station and when. In addition, the overall plan included component upgrades, such as generator rewinds and turbine retrofits. The planned equipment upgrades and power uprates across the Exelon nuclear fleet would generate between 1,300 and 1,500 additional megawatts, at ownership. (Several of the Exelon nuclear units are co-owned. The additional megawatts achieved through the power uprates applicable to the co-owner share are not reflected in these numbers.) This would be roughly the equivalent of a new advanced reactor without turning a spade of dirt.
Uprates have significant advantages over new nuclear plant construction as they can add equivalent low-cost baseload generation at a lower construction cost with less disruption and lower production risk.
Exelon’s projects fall in the following four categories:
Measurement uncertainty recapture (MUR) uprates, in which more accurate feedwater flow measurement allows more precise reactor power measurement. Power uprate increases up to about 1.7 percent are possible. MUR uprates require Nuclear Regulatory Commission (NRC) approval.
Extended power uprates (EPU), in which reactor power can be increased by up to 20 percent. EPU’s involve significant analysis including modifying or replacing selected components with greater capacity, such as larger pumps and valves. NRC approval is required.
Generator rewinds, in which replacing certain generator components with new copper makes it possible for the generator to produce more electricity. NRC approval is not required.
Turbine Retrofits, in which advanced technology has allowed production of new and better shapes and sizes of turbine parts, such as blades, rotors and casings. These new parts make the turbines more efficient. NRC approval is not required.
Midway through 2011, Exelon had completed projects that resulted in the addition of 194 MWe, with an additional 50 MWe (all at ownership) expected by the end of the year. Since 2009, main generator rewinds and switchyard upgrades have been completed at four units. Two low-pressure turbine retrofits were completed and MURs at four units were also accomplished. License application requests (LAR) have been submitted to the NRC for MURs at four additional units, with approval expected in mid 2012. We also have EPU license application requests under development for four units.
|An application for uprates of 58.4 MW at Byron Generating Station Units 1 and 2 was submitted to NRC in June 2011. Photo courtesy of Exelon Corp.|
The project has four additional LP turbine retrofits planned for completion by the end of 2012. Two units will be completed in late 2011 and the remaining two units in late 2012. In addition to increasing electrical output, the turbine retrofit projects have addressed significant material condition issues with the old turbines. The isophase bus duct system was also replaced with the two retrofits completed thus far. Consistent with the proposed implementation plan, approval to proceed with MURs on five units and a two-unit EPU were recently received. Corporate authorization for each project is now under development.
The business case for each ongoing and proposed EPU projects is reevaluated several times each year, based on the significant cost and planned electrical output for the corporation. Several key factors that are considered during the reevaluation include projected power prices, discount rates, cost assumptions, tax assumptions and in- service dates. As a result of these reviews, a recommendation was made and accepted not to proceed with an EPU at one station. The overall cost of this project resulted in a marginal business case with more risk than benefit to proceed.
With the large number of projects underway at multiple nuclear units, the project has been able to leverage economy of scale in its vendor contracting strategy. Common multi-unit contracts have been established for major components, services and functions. As an example, common contracts were established for the six low-pressure turbine retrofits, main generator rewinds at 11 units and supply of 11 flow meters (LEFM’s) associated with the MUR’s. Service contracts were established for steam dryer analysis at six units, MUR nuclear steam supply system analysis at eight units and EPU analysis at six units. Other common unit contracts include installation services at all units, balance of plant engineering and design changes at all units and large equipment disposal services at six units.
Some of the strategies included in the multi-unit contracts include performing basic engineering once and training installers on common procedures and processes once and applying to many units. Other aspects include common inventories for the same equipment, common quality and surveillance programs for equipment from the same vendor and use of blanket contracts with favorable terms and conditions. The contracting strategy will save the company millions of dollars and also provide future cost predictability.
The power uprate campaign is in its fourth year, with another six years of work remaining. Very good progress has been achieved thus far. The expectation is that another 1,000 MWe of additional output will be achieved by the power uprate organization based on the key plans and strategies established and the strong corporate commitment to these initiatives.