The Three Mile Island Accident (Part 4)

Three Mile Island has been of interest to human factors engineers as an example of how groups of people react to and make decisions under stress. There is now a general consensus that the accident was exacerbated by wrong decisions made because the operators were overwhelmed with information, much of it irrelevant, misleading or incorrect. As a result of the TMI-2 incident, nuclear reactor operator training has been improved. Before the incident it focused on diagnosing the underlying problem; afterward, it focused on reacting to the emergency by going through a standardized checklist to ensure that the core is receiving enough coolant under sufficient pressure. In addition to the improved operating training, improvements in quality assurance, engineering, operational surveillance and emergency planning have been instituted. Improvements in control room habitability, “sight lines” to instruments, ambiguous indications and even the placement of “trouble” tags were made; some trouble tags were covering important instrument indications during the accident. Improved surveillance of critical systems, structures and components required for cooling the plant and mitigating the escape of radionuclides during an emergency were also implemented. In addition, each nuclear site needed to have an approved emergency plan to direct the evacuation of the public within a ten mile Emergency Planning Zone (EPZ); and to facilitate rapid notification and evacuation. This plan is periodically …