Unlearned Lessons of Year-plus Reactor Outages

The report analyzes 51 'year-plus' reactor outages in the U.S. since 1966, finding that over 70% were caused by systemic 'safety restoration' needs resulting from inadequate corrective action programs (CAPs). It argues that the NRC has failed to monitor safety margins effectively, often relying on optimistic perceptions rather than reality, and recommends that the NRC improve CAP assessments, expand generic communications to include non-hardware problems, and increase transparency with Congress.

• Between 1966 and 2006, 41 of the 130 licensed U.S. nuclear power reactors experienced one or more outages lasting a year or more, totaling 51 such outages.
• The majority of extended outages—over 70%—were 'safety restoration outages' caused by cumulative, systemic degradation of components and programmatic breakdowns rather than single accidents or specific component failures.
• The report estimates that these 51 extended outages resulted in nearly $82 billion in lost revenue (in 2005 dollars) and accounted for approximately 135 reactor years of downtime.
• A primary cause of these outages is the failure of Corrective Action Programs (CAPs), which are federally required under Appendix B to 10 CFR Part 50 to identify and fix problems promptly.
• The NRC often fails to accurately assess CAP effectiveness, as evidenced by the Davis-Besse plant, where the NRC gave the CAP high marks in March 2001, only for a subsequent inspection in 2004 to find that 80% of reviewed corrective responses had weaknesses.
• Safety decisions are frequently guided by perception rather than reality; inspectors often fail to find problems at plants perceived as 'good' and only identify them after a 'sea change' in perception occurs during an outage.
• The NRC's generic communications program is too narrowly focused on hardware problems and fails to alert plant owners about non-hardware or programmatic breakdowns that lead to extended outages.
• The report identifies a lack of internal communication within the NRC, noting that regional staff may be unaware of problems known to headquarters staff, preventing the agency from 'connecting the dots' regarding plant safety.

APA

Lochbaum, D. (2006). Unlearned Lessons of Year-plus Reactor Outages. Union of Concerned Scientists. https://www.ucs.org/sites/default/files/2019-09/nuclear_tightrope_report-highres.pdf

Chicago

Lochbaum, David. Unlearned Lessons of Year-plus Reactor Outages. Union of Concerned Scientists, 2006. https://www.ucs.org/sites/default/files/2019-09/nuclear_tightrope_report-highres.pdf.

Wikipedia

{{cite report |last1=Lochbaum |first1=David |title=Unlearned Lessons of Year-plus Reactor Outages |publisher=Union of Concerned Scientists |date=September 2006 |url=https://www.ucs.org/sites/default/files/2019-09/nuclear_tightrope_report-highres.pdf |access-date=23 October 2026 |via=Climate Insights Directory}}

BibTeX

@techreport{lochbaum2006unlearned, author = {Lochbaum, David}, title = {{Unlearned Lessons of Year-plus Reactor Outages}}, institution = {Union of Concerned Scientists}, year = {2006}, month = sep, url = {https://www.ucs.org/sites/default/files/2019-09/nuclear_tightrope_report-highres.pdf}, urldate = {2026-10-23}, note = {Indexed by Climate Insights Directory} }