Replacing equipment inside a nuclear power plant requires careful planning that begins many months before the plant outage. Entergy has adopted advanced modeling and simulation tools that allow engineers to "walk through" the entire outage in a virtual model, thus avoiding unanticipated surprises.
Waterford 3, located about 25 miles west of New Orleans, is one of the dozen nuclear plants owned and/or operated by Entergy Nuclear. The 1,157-MW plant has a two-loop pressurized water reactor that began commercial operation on September 24, 1985. According to Entergy Nuclear, the plant’s cost per unit of electricity produced is one of the lowest in the Entergy system. Data from the Energy Information Administration showed Waterford 3 operated at a capacity factor of 89% during 2008.
As is the case with every operating nuclear plant, upgrades are in order. Entergy plans to replace the two steam generators, reactor vessel closure head, and control element drive mechanisms during an outage scheduled for 2011. The estimated cost of these plant upgrades is approximately $511 million. One important feature of this plant outage is the absolute necessity that every aspect of it be considered in the project plan. To that end, Entergy Nuclear has adopted digital modeling and virtual simulation, combined with scanning inside reactor containment buildings, to do the most thorough and cost-effective job of preparing for the engineering and for planning maintenance tasks.
These simulations are among the first of their kind in the U.S. nuclear power industry, and the potential return on investment using these digital tools is huge. John M. Mahoney, innovations leader for Entergy Corp., sums it up as "another day, another million dollars." Each day of a power plant outage means purchasing about $1 million in replacement power.
With that much money at stake, it is very easy to justify the investment in modeling and simulation technology for maintenance and refurbishment projects. A plant can be brought back online sooner when task sequencing is optimized through better planning. The same is true when potential delays are discovered early, preferably during the planning phase, and avoided when the cost and impact of any changes are minimal.
Combining Digital Tools
John Gaertner, tech executive for plant technology at the Electric Power Research Institute, pointed out that "nuclear power plants have excellent process management and plant configuration management. But they achieve it at great cost and with many resources consumed. Creating a virtual plant with scanning and PLM [product lifecycle management] will integrate information systems, visualize and access information, perform logistical and analytical simulations, communicate within plant processes, and interface easily with suppliers, contractors, and other entities."
"Not many innovative technologies come along these days that will change the way engineering is done, the way work plans are developed, and where training can be provided prior to doing work — especially all at once," Mahoney said. The problem is the complexity of the work that must be completed in a two- or three-week outage. For example, refueling a power plant takes more than 2,000 discrete tasks. This involves many different contractors and hundreds of pipe fitters, riggers, nuclear-certified welders, and so on. Few of them have ever been inside Waterford 3’s containment.
Because all U.S. nuclear power plants are at least 20 years old and predate 3-D design tools, it is impossible to find to up-to-date 3-D computer-assisted drawing (CAD) models for these plants. Good 3-D models can be intelligently built from 2-D engineering drawings by using techniques such as laser scanning and sketch-tracing. Until now, nuclear generation owners have planned plant outage work in traditional meetings and conferences using hundreds of paper drawings, project timelines, physical mockups, and other training aids. However, those methods no longer seem cost-effective.
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