Three Mile Island Essay

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Pages: 3

The Three Mile Island Accident

Introduction
On March 28th, 1979 the Three Mile Island accident occurred. It was a partial nuclear meltdown that happened due to a number of reasons, but human error was the main benefactor to the meltdown. The Three Mile Island nuclear plant is located in dauphin country, Pennsylvania, United States and still has one operational core: TMI1. It was placed on point 5 of a 7 point nuclear disaster scale.

The reactors
Both TMI1 and TMI2 were (is, in the case of TMI1) pressurised water reactors designed by Babcock & Wilcox the difference being that unit 1 was slightly smaller with a net generating capacity of 852 MWe and unit 2 was slightly larger with a generating capacity of 906 MWe.

The accident
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This would cause a series of pumps to turn off thus, the steam generators stopped receiving water and the heat and pressure increased in the reactor coolant system. The reactor entered an emergency shutdown: Control rods were lowered into the core to halt the nuclear chain reaction. However, the reactor continued to generate decay heat and because the turbine was no longer generating steam heat had ceased to be removed from the reactors primary loop.
Once the secondary pumps had stopped the auxiliary kicked in automatically. The valves on all the auxiliary pumps had been closed for routine maintenance which meant the system was unable to pump any water. By closing these valves, they violated a key nuclear regulatory commission (NRC) (the NRC’s role is to protect the peoples of America’s health and safety related to nuclear energy) according to which a reactor must be shut down if all auxiliary pumps are closed for maintenance. Later on this was recognised as a key benefactor to the meltdown by NRC