Fukushima nuclear accident, Japan

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Nuclear accident at Three Mile Island

The nuclear accident at the nuclear power plant at Three Mile Island occurred on March 28, 1979, one year after the commissioning of Unit 2 (TMI-2). The nuclear accident occurred the second reactor of the plant;. Reactor pressurized water

The Three Mile Island is located about 16 km from Harrisburg in the state of Pennsylvania, in the United States.

On the 4am circuit responsible for supplying water to the turbines disconnected which caused him to stop the cooling function of the primary circuit.

View of the nuclear power plant at Three Mile Island. Protagonist of a nuclear accident in 1979.


Overheating produced in the core of the reactor resulted in an increase in pressure in the primary circuit, causing the introduction of control rods designed to automatically stop the nuclear reactor.

Additional water was pumped through the cooling circuit of an emergency. However, the valves controlling the passage to the steam generator is blocked for a while. The responsible engineer disconnected the corresponding control operator and confused various measuring instruments.

Because of these errors, the contaminated water came flooding the containment building that surrounds the reactor. Thus radioactive gases were released into the atmosphere (xenóny krypton). In addition, they left large amounts of water with a low level of radioactive contamination, which ended up in the river.

When six years later it was possible to enter the premises, an introduced camera could show that had melted part of the nuclear fuel.

Thirty thousand people living around the nuclear plant, spread over a radius of 8 km, were exposed to certain levels of radioactivity, although the effects of radiation were very small.

According to the Nuclear Regulatory Commission (NRC) estimated the effective dose equivalent to the 7th of April was 3,300 people. This represents an increase of 1.5% in the annual equivalent dose received in the area for natural radiation, which is 1 mSv.

The nuclear accident at the Three Mile Island was rated as level 5 on the International Nuclear Event Scale (INES scale).

This accident led to the further improvement of the safety of nuclear power plants, defining corrective measures that have been included in all countries with nuclear facilities, and the development of training programs for staff formacióny of the installation.

References for the nuclear accident at Three Mile Island

Virtual Museum of Three Mile Island (English)

"A Nuclear Nightmare in Pennsylvania" - 20 years later

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