A simulated animation of a core melt in a light-water reactor after a loss-of-coolant accident. After reaching an extremely high temperature, the nuclear fuel and accompanying cladding liquefies and flows to the bottom of the reactor pressure vessel.Three of the reactors at Fukushima I overheated because the cooling systems failed after a tsunami flooded the power station, causing core meltdowns. This was compounded by hydrogen gas explosions and the venting of contaminated steam that released large amounts of radioactive material into the air.[1]Three Mile Island Nuclear Generating Station consisted of two pressurized water reactors manufactured by Babcock & Wilcox, each inside its own containment building and connected cooling towers. Unit 2, which suffered a partial core melt, is in the background.
A nuclear meltdown (core meltdown, core melt accident, meltdown or partial core melt[2]) is a severe nuclear reactor accident that results in core damage from overheating. The term nuclear meltdown is not officially defined by the International Atomic Energy Agency[3] or by the United States Nuclear Regulatory Commission.[4] It has been defined to mean the accidental melting of the core of a nuclear reactor,[5] however, and is in common usage a reference to the core's either complete or partial collapse.
A core meltdown accident occurs when the heat generated by a nuclear reactor exceeds the heat removed by the cooling systems to the point where at least one nuclear fuel element exceeds its melting point. This differs from a fuel element failure, which is not caused by high temperatures. A meltdown may be caused by a loss of coolant, loss of coolant pressure, or low coolant flow rate or be the result of a criticality excursion in which the reactor is operated at a power level that exceeds its design limits. Alternatively, an external fire may endanger the core, leading to a meltdown.
Once the fuel elements of a reactor begin to melt, the fuel cladding has been breached, and the nuclear fuel (such as uranium, plutonium, or thorium) and fission products (such as caesium-137, krypton-85, or iodine-131) within the fuel elements can leach out into the coolant. Subsequent failures can permit these radioisotopes to breach further layers of containment. Superheated steam and hot metal inside the core can lead to fuel–coolant interactions, hydrogen explosions, or steam hammer, any of which could destroy parts of the containment. A meltdown is considered very serious because of the potential for radioactive materials to breach all containment and escape (or be released) into the environment, resulting in radioactive contamination and fallout, and potentially leading to radiation poisoning of people and animals nearby.
^Martin Fackler (1 June 2011). "Report Finds Japan Underestimated Tsunami Danger". The New York Times.
^Commission, U. S. Nuclear Regulatory; Rasmussen, Norman C. (18 June 1975). "Reactor Safety Study: An Assessment of Accident Risks in U.S. Commercial Nuclear Power Plants". W.S. Hein – via Google Books.
^International Atomic Energy Agency (IAEA) (2007). IAEA Safety Glossary: Terminology Used in Nuclear Safety and Radiation Protection(PDF). Vienna, Austria: International Atomic Energy Agency. ISBN 978-92-0-100707-0. Retrieved 17 August 2009.
^United States Nuclear Regulatory Commission (NRC) (14 September 2009). "Glossary". Website. Rockville, Maryland, USA: Federal Government of the United States. pp. See Entries for Letter M and Entries for Letter N. Retrieved 3 October 2009.
A nuclearmeltdown (core meltdown, core melt accident, meltdown or partial core melt) is a severe nuclear reactor accident that results in core damage...
Japan's NuclearMeltdown", Season 2012, Episode 4, PBS Frontline Video of the Unit 1 explosion Video of the Unit 3 explosion Webcam Fukushima nuclear power...
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The world's first nuclear reactor meltdown was the NRX reactor at Chalk River Laboratories, Ontario, Canada in 1952. The worst nuclear accident to date...
books about the Chernobyl meltdown List of industrial disasters Lists of nuclear disasters and radioactive incidents Nuclear fallout effects on an ecosystem –...
generators led to loss of coolant and subsequent Nuclearmeltdown of three reactor cores. The Fukushima Daiichi nuclear disaster led to an uncontrolled release...
food chain. Nuclear technology portal Nuclearmeltdown Core damage frequency Fuel element failure Loss-of-coolant accident Nuclear power Nuclear power debate...
fall onto the reactor hall, causing a nuclearmeltdown. On 26 April 1986, reactor No. 4 suffered catastrophic meltdown resulting in a core explosion and open-air...
Look up meltdown in Wiktionary, the free dictionary. Meltdown may refer to: Nuclearmeltdown, a severe nuclear reactor accident Meltdown (security vulnerability)...
deposition levels, and time of the growing season". Three Mile Island The nuclearmeltdown at Three Mile Island in 1979 was categorized as a Level 5 accident...
the Chernobyl disaster, a lava-like glassy material formed in the nuclearmeltdown of reactor core 4. Chernobylite is highly radioactive due to its high...
between achievement of criticality and nuclearmeltdown as a result of an exponential power surge from the normal nuclear chain reaction, would be too short...
to: "China syndrome", a nuclearmeltdown scenario so named for the fanciful idea that there would be nothing to stop the meltdown tunneling its way to the...
provided to catch the molten core material (corium) of a nuclear reactor in case of a nuclearmeltdown and prevent it from escaping the containment building...
A nuclearmeltdown refers to the more serious hazard of releasing nuclear material into the surrounding environment. The most significant meltdowns occurred...
fatalities in the history of U.S. nuclear reactor operations. There was also a partial meltdown at the Enrico Fermi Nuclear Generating Station in Michigan...
safety coverups at a nuclear power plant. "China syndrome" is a fanciful term that describes a fictional result of a nuclearmeltdown, where reactor components...
radiation. Part of the wall was removed and sent to the Institute for Nuclear Research, where the caesium capsule was removed, identified by serial number...
to Meltdown is a pseudo-3D action game in which the player controls Homer as he races to the Springfield Nuclear Power Plant to prevent a nuclear meltdown...
system and were able to prevent a reactor meltdown. Although they were able to save themselves from a nuclearmeltdown, the entire crew, including Arkhipov...
2011). "Japan nuclear plant confirms meltdown of two more reactors; Fukushima Daiichi operator accused of delaying announcement of meltdowns in reactors...
The Three Mile Island accident was a nuclearmeltdown of the Unit 2 reactor (TMI-2) of the Three Mile Island Nuclear Generating Station on the Susquehanna...
NuclearMeltdowns (2013) Full Body Burden: Growing Up in the Nuclear Shadow of Rocky Flats (2012) The Gift of Time: The Case for Abolishing Nuclear Weapons...
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