Overview

At 4.00 on 28 March 1979, a transient occurred on Reactor No. 2 at Three Mile Island, near Harrisburg, Pennsylvania. A turbine tripped and caused a plant upset. The operators tried to restore conditions, but, misinterpreting the instrument signals, misjudged the situation and took actions which resulted in the loss of much of the water in the reactor and the partial uncovering of the core. Radio-activity escaped into the containment building. Site and general emergencies were declared.

The accident at Three Mile Island (TMI) (also referred to initially as Harrisburg) was the most serious accident which had occurred in the US nuclear industry.

The President set up a commission to investigate the accident. Their work is described in The Report of the Presidents Commission on the Accident at Three Mile Island (the Kemeny Report) (Kemeny, 1979).

The NRC carried out an investigation, reported in Investigation into the March 28, 1979 Three Mile Island Accident by Office of Inspection and Enforcement (the NRC Report) (NRC, 1979b). It also set up a task force, the findings of which are given in TMI-2 Lessons Learned Task Force Final Report (the Task Force Report) (NRC, 1979d).

Another report is Analysis of Three Mile Island Unit 2 accident by the Nuclear Safety Analysis Center (NSAC) of EPRI (1979a).

Hearings were also held by the US Congress (US Congress, 1979) at which evidence was taken from managers, engineers, process operators and others.

The Accident at Three Mile Island gives...