Nuclear Reactor Accidents

Three Mile Island Reactor 2 (TMI-2) Accident on March 28, 1979, was the most serious in U.S. commercial nuclear power plant operating history. This link gives a summary of the events.

The major layout of the nuclear reactor, the power generating building, and the cooling tower are shown here.

What Happened at Three Mile Island in March also gives a quick summary of the event.

The Chernobyl Reactor Accident

The Chernobyl Reactor The Soviet RBMK reactor has individual fuel channels, using ordinary water as coolant and graphite moderator. It evolved from reactors designed for plutonium production, and portion of it from the above link is shown here.

The accident at Chernobyl Unit 4 gives a rather detailed account.

Nuclear Reactor Accidents

In addition to the TMI-2 and Chernobyl accidents, the folowing accidents have been extracted from a report given by the IEEE site. But the site has been moved.
Reactor typeLocationAccident typeYearIodine-131 release, curiesComments
Graphite-moderated, gas-cooledSellafield, Britaingraphite fire195720,000
Graphite-moderated, water cooledChernobyl, Ukrainesupercriticality, steam explosion and graphite fire19867 million, perhaps far greater (see text)Safety experiment went awry; total release 50 to 80 million curies or more; potential for continuing large releases exists
Sodium-cooled fast breederLagoona Beach (near Detroit) U.S.cooling system block, partial meltdown1966release confined to the secondary containmentreactor was being tested for full power, but did not reach it; four minutes from indication of negative reactivity to meltdown
Sodium-cooled fast breederMonju, Japanmajor secondary sodium leak1995 secondary sodium was not radioactive; reactor was in test phase; extensive sodium contamination in plant
Light water reactor, PWR typeThree Mile Island, near Harrisburg, U.S.cooling system failure, partial meltdown197913 to 17secondary containment prevented release of millions of curies of I-131; accident developed over several hours
Light water reactor, BWRnear Idaho Falls, U.S.accidental supercriticality followed by explosion and destruction of the reactor196180small U.S. Army experimental reactor using HEU fuel; 3 operators were killed
Heavy water cooled and moderated reactorChalk River, Canadalack of coolant for a fuel element1958radioactivity apparently contained within buildingHighest worker dose 19 rem
Heavy water moderated, light water cooled, experimental reactorChalk River, Canadainadvertent supercriticality and partial meltdown1952"There was some release of radioactivity"President Jimmy Carter helped in the clean-up
Heavy water moderated and cooled, CANDU typeNarora, Rajasthan, Indiaturbine fire; emergency core cooling system operated to prevent meltdown system1993apparently no release of radioactivity

Sources: Chernobyl: NRC 1987 and Medvedev 1990; Sellafield: Makhijani et al. eds. 1995, Chapter 8; Three Mile Island: TMI Commission 1979 ; Lagoona Beach (Fermi-I) Alexanderson, ed. 1979 and Fuller 1975; Idaho: Horan and Gammill 1963 and Brynes et al. 1961; Monju: press reports; Chalk River: John May 1989 and Weinberg 1994; Narora, press reports. Full references are available here.