One of the primary reasons of the optimism for new nuclear plant construction progress in the U.S. is the significant increase in plant reliability and availability over the last 40 years. This paper provides insights on how the nuclear industry worked to improve the capacity factor and efficiency of nuclear power stations and ultimately reduce the cost to operate nuclear power plants in the U.S..

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While the number of nuclear power plants in the United States has remained relatively constant for the past several decades, (the last nuclear reactor to begin commercial operation, Watts Barr, came online in 1996) the percentage of nuclear power in the national energy mix has increased, as shown in the Figure 1. (data from EIA)

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Although a number of new plants came on-line in the 1970’s and 1980’s, a significant part of the increase in nuclear generation was achieved by a substantial increase in the overall capacity factor of the U.S. plants from about 60% in 1980 to over 90% today.

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This large increase in capacity factor was achieved by reducing outages, extending fuel cycles, using higher burnup fuel, reducing unplanned outages and reducing the number of fuel failures. This increase in capacity factor combined with increases in power in various plants (power uprates) allowed nuclear power plants to maintain and increase their share of electricity generation. Such an increase in nuclear power generation is the equivalent of having built 25–30 nuclear power plants during that period.

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The improvement of planned outage duration and unplanned outage frequencies improved during the last 30 years. Figure 2 shows the reduction of unplanned outages from about 9 to 3 events per year from the time period of 1976–1979 to 1986–91, subsequently. Figure 3 shows the length of the planned outages reduced from 106 days for an average operating plant in 1991 to 38 days in 2008. The reduction in planned outage length and the number of unplanned outages represents a significant improvement in the reliability, cost and safety of nuclear power plants.

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Additionally, power uprate, which allowed plants to operate at a higher power, and power plant life extension, which extended the operating life of a power plant beyond 40 years, provided more electrical power to be generated at a reduced total production cost.

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These initiatives and other cost and performance based programs improved the overall performance of nuclear power generation in the U.S. and has provided adequate improved cost and safety justifications for building more reactors in the U.S..