Nuclear plants in the U.S. have always had a requirement to have some form of emergency plan. However, the Three Mile Island (TMI) event in 1979 showed that there needed to be more pre-planning, training, cooperation, and drills between those organizations that would be required to respond to a nuclear plant emergency - federal, state, and utility agencies. That event provided an impetus for enhancing the management role of the Federal Emergency Management Agency. Some other required changes that occurred after the TMI event were:
On a world-wide basis, the International Atomic Energy Agency (IAEA) has identified the 7 level International Nuclear Event Scale (INES). Both the IAEA and the Nuclear Energy Institute (NEI) have published information regarding that system.
Levels of Emergency
The Notification of Unusual Event (NOUE) is the lowest NRC emergency action level and requires that the utility notify the Nuclear Regulatory Commission (NRC) and the state emergency agency. The NUE indicates there is a degradation of safety systems, although not serious enough to warrant special activation of the utility emergency organization.
If we remember that nuclear plants are designed with 3 barriers - fuel clad, reactor cooling system piping and vessel, and the containment - between the radioactive materials in the fuel and the public, the remaining emergency classes are generally based on successive breach of those boundaries.
Warning sirens may be installed in rings around the plant out to the 10 mile (16km) radius. These sirens are used to alert people who live in the surrounding community to turn on their radios or TVs and tune to the Emergency Alert System. In many areas, the sirens are also intended for notifying the public of other types of emergencies, e.g. tornadoes, hurricanes, tsunamis (tidal waves). The Emergency Alert System would make the announcement of an evacuation.
During normal operation, control of the plant is managed from the central control room. During an emergency at a nuclear plant, three additional command centers are used for management of the emergency - operation support center (OSC), technical support center (TSC), emergency operations facility (EOF). The control room still manages the reactor and main plant systems.
The decision to evacuate would likely occur at the general emergency level.
Return to the area would depend on an assessment of the amount of radioactive deposition in the area (including the impact on agricultural products and livestock) by utility, local, state, and federal agencies.
Drills and Exercises
Medical, small scale, and full scale emergency drills and exercises are required to ensure that personnel are training and able to respond properly to any type of emergency that occurs at the plant. These drills test parts of the organization not normally involved in the more frequently performed control room simulator drills.
Frequency of Emergencies
Typically a number of NOUEs (40 in 1997) will occur each year. Alert level emergencies occur less frequently (3 in 1997) among all 100+ US plants. The TMI event was only one of a handful of events that would warrant the site area emergency classification. Although it did not happen in the US, the Chernobyl event would have been classified as a general emergency.
Copyright © 1996-2008. The Virtual Nuclear Tourist. All rights reserved. Revised: December 9, 2007.