Fact Sheets

Timeline of Safety Enhancements to US Nuclear Energy Facilities

A timeline of safety enhancements that the U.S. nuclear industry has made since 1980.


1980—Formation of Institute of Nuclear Power Operations (INPO). Accredits training programs, conducts site inspections, shares lessons learned and operational information throughout industry, all with a goal of ensuring that plants achieve excellence above and beyond regulatory requirements. (Identified in 2011 by President’s BP/Gulf oil spill commission as a model for the oil industry.)

1980s—Expanded use of probabilistic risk assessment (PRA). This is a means to gain insights into the strengths and weaknesses of plant design and operation by calculating risk to determine what can go wrong, its likelihood, and its consequences. PRAs estimate frequencies of events that damage the reactor core, estimate frequencies of accidents that release radioactivity, and estimate consequences in terms of injuries and damage to environment.

1980s—Implemented hardware changes. This includes equipment qualification, the verification of ability of equipment to withstand harsh environments during and following “design basis” events. Also includes improved instrumentation and control systems.

1980s—Developed post-accident sampling systems. A program to sample radionuclides to help assess accident conditions and impacts and to take appropriate steps to recover from a severe event.

1980s—Developed emergency operating procedures. These symptom-based procedures were based on lessons learned from the Three Mile Island accident, and were developed for all reactor types.

1988—NRC finalized the station blackout rule. Designed to provide further assurance that a loss of both off-site and on-site emergency AC power systems would not adversely affect public health and safety. The rule requires that plants be capable of withstanding a station blackout for a specified duration and of maintaining core cooling during that period.

1990s—Established severe accident management guidelines. Designed to manage and mitigate severe events that are beyond “design basis” specifications. Plants evaluated site-specific vulnerabilities and implemented plant and procedural improvements to bolster safety. These guidelines were developed based on insights from probabilistic risk assessments that identified important accident sequences. The guidelines provide operators and emergency managers with predetermined strategies to mitigate these events. The strategies focus on protecting the containment, and assume that the fuel cladding and reactor cooling system are lost.

2002-2010—Post 9/11 precautions. Identified potential vulnerabilities associated with loss of large area of a plant. Site enhancements and operating practices to mitigate severe accident scenarios, such as aircraft impact, that include complete loss of off-site power, all on-site emergency power sources and loss of large areas of the plant. Developed additional methods and procedures to provide cooling to the reactor and the used fuel pool, and staged additional equipment at every plant site. More than $2 billion in additional security-related expenditures over the past decade in this area.

2003—Post Davis-Besse materials initiative. The industry developed a materials reliability initiative spearheaded by an executive-level oversight group composed of senior industry executives with broad experience in materials issues. The purpose was to address materials issues strategically and pro-actively through additional research, enhanced inspections and by implementing mitigation/repair strategies. Industry and INPO also strengthened the safety culture initiative.

2011—Detailed inspections of every U.S. nuclear plant site focused on important equipment needed to respond successfully to extreme events like fires and flood. This work included analysis to identify any potential that equipment functions could be lost during seismic events appropriate for the site, and development of strategies to mitigate any potential vulnerabilities. Facilities also verified their capability to mitigate flooding and the impact of floods on systems inside and outside the plant. Specific actions include verifying required materials and equipment are properly located to protect them from flood.

2011—INPO compiled a detailed timeline of events at the Fukushima Daiichi nuclear power station after the March 11 earthquake and tsunami. The detailed report was prepared as part of the integrated response to the Japan events to extract and apply relevant safety lessons.

2012—FLEX response strategy. The heart of this effort is adding more portable, backup safety equipment at each reactor. More than 1,500 pieces of equipment have been acquired or ordered including portable generators, diesel-driven pumps and satellite phones. The additional portable equipment will provide power and water to maintain key safety functions in the absence of AC power and heat transfer capability from permanently installed safety systems. These functions are reactor core cooling, used fuel pool cooling and containment integrity.

2012—Regional response centers. The industry is developing regional response centers in Memphis and Phoenix that will serve as dispatch points for additional equipment and resources. The regional response centers will be capable of delivering another full set of portable safety equipment, radiation protection equipment, electrical generators, pumps and other emergency response equipment to an affected site within 24 hours after an extreme event.