The January 2007 issue of
POWER included an article (“
Tow nuclear power I&C out of the ‘digital ditch’ ”) describing instrumentation and control (I&C) upgrade projects at nuclear power plants as “stalled” and “checkered, at best.” To be sure, some projects have experienced technical problems and may have missed their budget and/or schedule. But they are anomalies and are not indicative of a widespread problem in the nuclear industry, as the author suggests.
Fully recognizing that the article was addressing unit-specific design and management issues, we would like to offer a few case studies of successful projects and invite others to do the same. In this way, we can together learn to capitalize on the real successes in the industry.
In general, a successful project begins at the highest management level at a plant with a definitive statement of the business objectives and a well-defined plan for procurement, design, testing, installation, training, and operation. It’s our position that properly organized and staffed I&C projects can be implemented successfully. This article presents case studies of three successful upgrade projects at nuclear plants. Each case covers the scope, approach, and details of the project and explains why it should be considered a success (see box).
Case study #1: Turbine controls upgrade at Energy Northwest’s Columbia station
The old digital electro-hydraulic (DEH) turbine control system at Columbia Generating Station (Figure 1), a 1,250-MW boiling water reactor (BWR), was obsolete and not single-failure-tolerant. Component and subsystem failures had resulted in unit trips, power reductions, load swings, and operation in manual control for extended periods of time.
1. Death of DEH. Engineers at Energy Northwest’s Columbia Generating Station replaced the plant’s digital electro-hydraulic control system with a new, fully digital one that is single-fault-tolerant. Courtesy: Energy Northwest
To resolve these problems, Energy Northwest replaced the old DEH control system with a new, state-of-the-art system that is single-fault-tolerant and can be repaired on-line. The new system employs redundant input signal devices, redundant digital signal processors, and redundant output devices. It also features improved control algorithms and start-up and shutdown control procedures, and provides additional information on turbine-generator performance to operators and engineers.
On a fast track. A key objective of the replacement project was to complete it during a refueling outage scheduled to occur 13 months after the contract award to the control system vendor. Meeting such a tight schedule without compromising the quality of work was a major challenge.
Replacing the control system and related input/output (I/O) devices required making the following changes:
- Replacing the five DEH cabinets in the main control room with four new cabinets containing the redundant control equipment and I/O, a new turbine overspeed protection circuit, and new digital synchronizing and load control equipment.
- Replacing the switches, indicators, and recorders on the main control board with touchscreen displays.
- Installing new turbine control system hardware and software on the existing operator training simulator.
- Installing seven new speed sensors: three for speed control, three for overspeed protection, and one spare.
- Connecting the new turbine controls to the plant’s distributed control system (DCS) through a firewall.
Energy Northwest’s management team realized that executing such a large and complex project on such an aggressive timeline would require close coordination of all participants’ work. Accordingly, among the project management tools put to use were a single integrated schedule, an integrated project action tracking list, and a common weekly meeting for all organizations. The formation of a dedicated project team was followed by establishment of a formal division of work and a formal work sequence.
The controls vendor chosen was Invensys (www.invensys.com), which supplied its TMR (triple-modular redundant) Tricon turbomachinery control system for integrated turbine protection and reactor pressure control. The Tricon TMR system also executes an all-new turbine trip control scheme whose inputs include digitally delivered measurements of lube oil parameters, thrust, vacuum, and overspeed. The Tricon system brings together more than 600 critical monitoring and control system I/O points from the plant’s turbine and generator.
On this project, Sargent & Lundy (www.sargentlundy.com) provided a range of engineering services that included a conceptual study, specification development, bid evaluation, a plant modification package, procedural updates, installation and test support, and project management assistance.
Strategy. The project’s overall strategy was to perform as much pre-outage installation work as possible within the confines of an operating plant. That work included the installation of conduits and cable pulls in areas accessible with the plant on-line. Work during the refueling outage included the removal of existing DEH cabinets from the control room and installation of speed probes, thrust probes, pressure transmitters, and linear variable differential transformers (LVDTs). It also included installation of new cabinets in the control room and installation of operator workstations with touchscreens in the main control board and on the lead operator’s desk.
Formal test or validation procedures were developed for each phase of the project and successfully completed before moving on to the next phase. They included:
- Factory acceptance tests of original equipment
- Testing of software and touchscreens (performed on the plant simulator)
- Modification and power ascension tests
- Site acceptance tests following installation of the complete system
Regarding the project’s speed of execution, W. Scott Oxenford—vice president of technical services at Energy Northwest—noted that, “its most remarkable aspect was the timeline of design and implementation. In March 2006 we issued the Limited Notice to Proceed to Invensys and had our initial on-site kick-off meeting with all present. Only 10 months later, the system was installed in the simulator, ready to support two cycles of operator training. Six months after that, the system was operating with precision.”
Through the use of sound project management methods and tools, selection of the right project team, and remaining focused on the objectives, this complex digital upgrade project was successfully completed on an extremely tight schedule, during a planned outage.
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