Cesium – an element occurring naturally in rocks, soil and dust. The breakdown of uranium fuel in nuclear reactors produces radioactive forms including cesium-134 and cesium-137, exposure to which can cause nausea, vomiting, diarrhea, bleeding and death.
Curie – a measure of radioactivity, with 1 curie equal to the activity of one gram of radium.
Erythema – redness of the skin due to capillary congestion, it can be caused by radiation exposure.
Iodine-131 – a radioactive element produced in nuclear reactors. Absorbed into the body, it accumulates in the thyroid gland, which controls metabolism, and can cause cancer and other diseases.
Kemeny Commission – a panel created in April 1979 by President Jimmy Carter to investigate the Three Mile Island disaster. It was chaired by John G. Kemeny, president of Dartmouth College, and released its final report on Oct. 31, 1979.
Noble gases – a group of chemical elements that occur in nature in a number of isotopes, some of which are unstable and emit radiation.
Nuclear fission – the splitting of an atom accompanied by the release of energy. In a nuclear reactor, the fission energy is converted to heat used to generate electricity via steam turbines.
Nuclear meltdown – a severe nuclear reactor problem that occurs when there is a loss of control over the reactor core, causing the radioactive fuel to melt and release highly radioactive and other toxic elements.
Nuclear reactor core - the part of a nuclear reactor containing the nuclear fuel; it is where nuclear reactions take place.
Radiation, ionizing – subatomic particles or electromagnetic waves energetic enough to detach electrons from atoms or molecules. It includes alpha particles, beta particles and gamma rays.
Radiation poisoning or sickness – damage to organ tissue due to excessive exposure to ionizing radiation. Acute symptoms include erythema, nausea, vomiting, diarrhea, hair loss and internal bleeding.
Radium – an extremely radioactive chemical element that was at one time used in self-luminous paints for watch dials, leading to radiation-related illnesses in dial painters.
Rem — an acronym that stands for “roentgen equivalent in man,” this is a unit for measuring absorbed doses of radiation equivalent to one roentgen of X-rays or gamma rays.
Roentgen — a unit of measurement for ionizing radiation.
Scram – an emergency shutdown of a nuclear reactor, also referred to as a “trip,” achieved by inserting neutron-absorbing control rods into the reactor core.
Strontium – a highly reactive chemical element whose radioactive isotope, strontium-90, is produced by nuclear fission. It takes the place of calcium in bones and can lead to bone disorders including cancer.
Three Mile Island Units 1 and 2 – the two reactors at the commercial nuclear power plant located south of Harrisburg, Pa. on an island in the Susquehanna River. TMI-2 suffered a partial meltdown on March 28, 1979 and is no longer in operation. Originally built by General Public Utilities Corp. and operated by Metropolitan Edison, TMI-1 is now operated by Chicago-based Exelon while Unit 2 is owned by Met-Ed.
Uranium – a radioactive element used by fuel in nuclear reactors.