Three Mile Island

Throughout American nuclear power history many accidents have occurred, but Three mile island stands out as one of the worst. This event shocked the nation and

The accident began around 0400 on March 28, 1979 a feed pump stopped functioning. When working properly this feed pump would remove heat from the steam generator. Because of this temperature and pressure began to rise. This resulted in the reactor having to preform a SCRAM. The control rods descended into the reactor in order to stop the fission process but heat was still being made. This triggered the pilot-operated relief valve to open automatically. After the pressure was reduced to a safe level the PORV was supposed to shut, however, it did not. The control panel indicated that the valve was closed but with no way to tell if it was closed the operators did not see that the valve stayed open. The open valve released steam and coolant water. This is the main cause of the coolant-loss meltdown that occurred.

With the PORV open and pressure dropping some of the water left in the reactor turned into steam and forced the water out of the reactor and into the pressurizer and steam surrounded the reactor core. Steam does not conduct heat as well as water causing some of the fuel pellets heated up and started melting, beginning the meltdown. A nuclear power plant has tanks of water ready to be pumped into the reactor in case of an accident. One of these automatically turned on. An operator noticed this but the pressurizer indicated that it was full of water so the operator shut off the emergency water because he assumed that because the pressurizer was full of water and the assumption that the PORV was shut.

During the first few hours of the accident while the pressurizer was filling with water some water escaped through the pressurizer valve and spilled onto the floor in the. This water had been exposed to radioactivity and became radioactive itself. This radioactivity could not be contained and...