Have other reactors upgraded to ASDs?
The answer is yes. That’s important, because plants considering the same modification can benefit from lessons learned by the pioneers and from their operating and maintenance experience.
Specifically, Energy Northwest’s 1,157-MW Columbia Generating Station retrofitted load-commutated inverter-type ASDs for its recirculation pumps in the mid-1990s. Tennessee Valley Authority’s (TVA’s) Browns Ferry Nuclear (BFN) Plant also installed three Perfect Harmony Model WCII units (the predecessor of the WCIII) between 2003 and 2005 and has since accumulated more than eight years of operating experience on them. Siemens made about 50 changes to the WCII based on lessons learned from the BFN installation by a TVA users’ group. Finally, Southern Nuclear’s Plant Hatch and Progress Energy’s Brunswick Plant have purchased the Perfect Harmony WCIII drives and have begun designing them into systems scheduled for installation in the spring of 2009.
Examine your business case
Because the new ASDs are more efficient than M-G sets, they should reduce house loads. This reduction for Quad Cities Unit 1 is anticipated to be 2.5 MW. Although the expected improvement in system reliability from the upgrade is harder to quantify, it should be significant, as should the reduction in maintenance costs. Fuel savings also should be realized because, unlike M-G sets, ASDs can deliver full flow at the end of the nuclear fuel cycle.
Exelon Nuclear has concluded that a project to upgrade from M-G sets or flow-control valves to ASDs will deliver a positive net present value and a very attractive internal rate of return, with typical business case assumptions. How good would the economics be at your BWR? You’ll have to do your own analyses that take into account the particulars of your plant. But at Exelon Nuclear, the results of in-depth studies convinced corporate management that adding ASDs at Quad Cities in the spring of 2009, and at the remainder of its BWR fleet in the future, is an excellent idea.
—James W. Morgan (james.morgan@exeloncorp.com) is a principal engineer for instrumentation and control with ILD Inc. (www.ildpower.com). On assignment to Exelon Nuclear’s corporate engineering department, he is the lead engineer responsible for Exelon’s fleetwide upgrade of reactor recirculation pump flow control systems.
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