Walking a Nuclear Tightrope
Chapter 1 The Relevance of ear-plus Outages
CS reviewed those occasions when U.S. nuclear power reactors restarted follow- ing outages* lasting a year or more. We selected this performance measure because, while relatively brief nuclear reactor outages are com- monplace (many are planned for maintenance and refueling operations), year-plus outages are not. Since outages are very costly for a plant, an extended outage suggests the seriousness of the problems leading to it. U
The average length of refueling outages, which occur relatively frequently and continue to account for most outage time at U.S. reactors,
declined from 104 days in 1990 to 38 days in 2005 (Figure 1). As a result, a year-long reactor outage in 1990 was equivalent to more than 3.5 average refueling operations, but a year-long outage today is equivalent to more than nine refueling operations.
These comparisons suggest the extent to which safety margins had eroded prior to year- long outages and the cost of restoring the neces- sary margins—plant owners must expend the time and labor equivalent of several back-to-back refueling outages to climb out of the hole.
Figure 1. Average Length of Refueling Outages
1990 1991 1992 1993 1994 1995 1996 1997 1998 1999 2000
Source: Nuclear Energy Institute. 2006. Online at http://www.nei.org/documents/ U.S._Nuclear_Refueling_Outage_Days_Average.pdf.
“Outage” refers to the time in which a nuclear reactor is not providing power to the electrical grid. Since a nuclear power reactor’s sole
purpose is to generate electricity, plant owners have ample reason to minimize the number and duration of outages.