Capacity Factors Study generates high marks for nuclear plant performance
Nearly half of the licensed power reactors (47 of 104, or 45.19 percent) had capacity factors of 90 percent or more from the start of 2001 through the end of 2003. Capacity factor is the ratio of the electricity generated by a power plant compared to the electricity that could have been produced if the plant had operated at full power, nonstop.
When utilities ordered reactors in the 1960s and 1970s, they expected that capacity factors of about 65 to 75 percent would allow them to produce electricity at competitively low costs. The vast majority of U.S. power reactors now routinely achieve capacity factors far beyond those levels. The Nuclear News article calculated the capacity factors from each plant's design electrical rating (DER), which the editors think most closely reflects a power plant's intended capability.
The median three-year DER net capacity factor of the 104 reactors was 89.66 percent in 2001-2003. This continues a fairly steady rise of the median of more than 22 percentage points over six three-year periods. The median capacity factor in 1986-1988 of the 77 reactors in service then and still operating today was 67 percent. In all of the three-year periods before 1986, the median capacity factors were lower than in any three-year period from 1986-1988 onward.
The article also showed that the two different types of power reactors in the United States--pressurized water reactors (PWRs) and boiling water reactors (BWRs)--performed about equally well in 2001-2003. Historically, the PWR median capacity factor had been five to 10 points higher than that of BWRs. In 2001-2003, the median capacity factor of the nation's 35 BWRs was 90.36 percent, slightly better than the 89.53 percent median among the 69 PWRs.
Only two of the 104 licensed power reactors had capacity factors lower than 70 percent in 2001-03: FirstEnergy Nuclear Operating Company's Davis-Besse, a pressurized water reactor in Ohio, which was out of service for most of the three-year period for major repairs and revamping of its operations as required by the U.S. Nuclear Regulatory Commission; and the Tennessee Valley Authority's Browns Ferry-1, a boiling water reactor in Alabama, which has been out of service since 1985 but is being refurbished by the TVA with the goal of restart in 2007. Davis-Besse resumed full-power operation in April 2004.
The full article will be available online in mid-May from the American Nuclear Society's Web site, www.ans.org/pubs/magazines/nn.
