By Gary Wolski, Vice President-New Build, Nuclear Division, Curtiss Wright Flow Control
At 4:30 a.m. on Dec. 2, 1957, the control rods at the Shippingport Atomic Power Station were raised just enough to allow the world’s first full-scale atomic electric power plant devoted exclusively to peacetime uses to reach criticality. After two weeks of testing and power ascension, the plant was providing electricity throughout the Pittsburgh area. Philip Fleger, Chairman of the Board for Duquesne Light Co., said, “The lessons already learned in building this pioneer station, the lessons yet to be learned in operating it, will be applied throughout the free world. Atomic power stations now under construction, as well as others still to be designed, will be more efficient and more economical because of it.”
Mr. Fleger’s statement held true: With 104 operating reactors in the United States today, these nuclear power plants are the safest, most efficient, cost effective base load energy producers available. The industry has learned how to operate and maintain these plants in a manner that maximizes safety and performance. In the late 1980s, as the pace of new plant construction began to slow, the capacity factor (ratio of electricity generated to what could have been generated at full power, for the same period) was approximately 60 percent. As the industry gained operating experience and knowledge, the capacity factor increased to over 90 percent in 2000, and remains above that mark today .
This achievement is due in part to improving the operating performance of plant equipment by identifying poor performing components and replacing them with designs better suited for that application. A pump trip or valve failure can place the plant in a condition of reduced power, or even shut it down. One by one, these poor performing components were replaced with different materials, different designs, different manufacturers, or a combination of these variables, until the plant was running at optimum performance.
As the power industry prepares to begin building nuclear power plants again in the United States, it is important to apply these operating lessons learned to new plant designs to avoid the costly learning curve experienced during the ‘80s and ‘90s. The lessons from the nuclear island are well understood, documented and applied, but there is less emphasis on the secondary side where components are sometimes referred to as ‘commodities.’
This includes the pump or valve or instrument that is necessary for operations, but not necessarily engineered for that specific application. These secondary side components can affect the performance and capacity of the plant as easily as those in the primary side of the plant.
One such example is the swing or tilting disc check valves installed at the discharge of two pumps in parallel resulting in water hammer and pump damage. Or the rubber-lined carbon steel butterfly valve installed in a brackish water environment whose rubber seat is damaged by crustaceans and whose body is corroded by the sea.
If we are to apply these lessons, we must understand them and relate them to current applications. And we must perform the necessary engineering to select the right technology, material and manufacturer. This effort will take time and nuclear experienced personnel, both of which are in demand and at a premium. The right technology and material for the application, more often than not, is more expensive than the commoditized component.
So, if applying these lessons will take more time, more experienced personnel and a higher component cost, while the industry is attempting to reduce the capital cost of building these plants, how can the industry justify doing it now? Why doesn’t the industry install the lowest-cost component today, reduce the price tag of the new reactor and retrofit the poor performing components as they fail?
The risk of this approach to the industry is a new fleet of plants operating at a lower capacity factor than the existing fleet, not obtaining the required return on their investment, and a loss of confidence in the industry by the public, the government, and the bankers, making it more difficult to build the next plant.
There is also an impact on the O & M cost of the operating plant. To fully understand this impact, an analysis was performed using data from an operating nuclear power plant for a specific application. This application was in the service water system where rubber-lined carbon steel butterfly valves were installed at the time of construction. The valves were operating in a brackish water environment and had zebra mussels growing on the seating surface, resulting in damage to the seats and high levels of corrosion and valve failure. This damage provided operational and maintenance limitations, as well as replacements required on a 10-year frequency.
The plant identified a solution component, but the valve’s initial cost was more expensive than the incumbent valve. The utility applied a total cost of ownership model to accurately compare the total costs required for this modification.
The plant was able to justify installing a titanium triple offset metal seated butterfly valve, which in turn, eliminated the seat damage, corrosion issue and operation and maintenance issues.
Using the actual utility data, and extrapolating over the anticipated 60-year life of a new nuclear power plant, the cost of installing the titanium valve was compared: at time of construction; after 10 years of operation (when the carbon steel valve required replacing); and not at all (not applying lessons learned and keeping the carbon steel valve in the system).
The result of this analysis concluded that it will cost the operating utility nearly six times as much over 60 years to not apply the lessons learned (installing titanium rotary disc butterfly valves) at the time of construction and would cost twice as much if they replaced the carbon steel valves with the titanium valves after 10 years of operation. The primary contributors for this difference are the additional costs associated with corrective maintenance, preventive maintenance, and in-service testing and inspection. These additional operation and maintenance costs makeup the difference in initial component costs in just five years of service.
Although there is an obvious financial and operational benefit to applying these lessons, the realities of lowering the initial cost of a new nuclear power plant may appear overwhelming.
It may be tempting to forgo the application of these lessons until well into the operating cycle, but the cost to the industry is too great. The industry must find a way to justify the cost of implementation, and be creative in ways to reduce its implementation cost. Leveraging the experience and knowledge of the nuclear supply chain is one such way.
The relationship between the utility, reactor designer, engineering procurement construction company and supplier must be different in the next round of nuclear construction. The supplier should be engaged early and often. Commitments should be made to allow the supplier to justify expending resources to assist in the system design and component selection. This early engagement and commitment, or partnering, can reduce and potentially eliminate the additional costs associated with time, experience and component selection.
The success of the first wave of new reactors will greatly determine the amplitude and frequency of the subsequent waves. This success, in part, will be through the understanding and implementation of the lessons of over a half of century of operating experience. Many of these lessons were achieved at the hands of the nuclear supplier base. Progressive utilization of this supplier resource can result in a cost effective implementation of lessons learned resulting in the safest, most cost effective and efficient fleet of new reactors.
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