The answer your probably looking for is 'melt down' however a melt down is a very rare event and the worst form of 'nuclear accident'.
the reactor accident at the chernobyl nuclear power plant.
The term "Broken Arrow" is used to indicate a nuclear accident involving a nuclear weapon that does't pose the threat indicated. The term "excursion" (as in nuclear excursion) or "criticality accident" is applied to a nuclear reactor or nuclear material accident, respectively.
There are many ways a nuclear accident may occur, however most nuclear power plant accident occur due to problem in an reactor.
Meltdown is a term that describes the melting of a nuclear-reactor core as a result of a nuclear accident
Meltdown is a term that describes the melting of a nuclear-reactor core as a result of a nuclear accident
The Chernobyl Nuclear Power Plant underwent a level 7 event - the worst accident so far. The plant, located in the Soviet Union near Pripyat in Ukraine lost its number four reactor on 26 April 1986. A link to the Wikipedia article on the accident is provided.
The #4 reactor is the reactor at the Chernobyl Nuclear Power Plant (Pripyat, Ukraine) that exploded on April 26, 1986. It is still the worst nuclear accident to ever take place anywhere.
A nuclear meltdown is an informal term for a severe nuclear reactor accident that results in core damage from overheating. A meltdown occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point which at least one nuclear fuel plate exceeds its melting point.
Thankfully there haven't been many nuclear accidents, however when they do happen they can be severe the worst nuclear accident/disaster was the explosion of reactor No.4 at the Chernobyl Nuclear power plant in 1986 on April the 26th.
Worst reactor accident to that date. The Japanese 2011 accident may turn out to be worse however.
A Nuclear Reactor.
There are a few dangers that are inherent in a nuclear reactor. The major danger inherent in a nuclear reactor is the effects of radiation. Radiation poisoning can be extremely deadly and harmful. Other inherent dangers include radioactive waste and the potential catastrophic damage of an accident such as at Chernobyl.