GLOSSARY OF NUCLEAR TERMS
Philippine Daily Inquirer
First Posted 03:55:00 03/19/2011
Containment: A structure that separates the reactor from the environment. It is usually made of high-density, steel-reinforced concrete.
Core: It contains the nuclear fuel and generates heat. It contains low-grade uranium, control systems and structural materials.
Coolant: The liquid or gas material circulating through the core to prevent overheating.
Decommissioning: The process of safely closing a nuclear power plant to retire it from service. This involves decontaminating the facility to reduce residual radioactivity and then releasing the property for unrestricted or (under certain conditions) restricted use. This often includes dismantling the facility or dedicating it to other purposes. Decommissioning begins after the nuclear fuel, coolant, and radioactive waste are removed.
Entomb: A method of decommissioning, in which radioactive contaminants are encased in a structurally long-lived material, such as concrete. The entombed structure is maintained and surveillance is continued until the entombed radioactive waste decays to a level permitting termination of the license of the nuclear facility and unrestricted release of the property.
Fission: The splitting of a heavy nucleus into two roughly equal parts accompanied by the release of a relatively large amount of energy.
Fuel rod: A long slender tube that holds uranium, which fuels a nuclear reactor.
International Atomic Energy Agency (IAEA): The agency, with 151 member states, that inspects nuclear and related facilities under safeguard agreements. It was established in 1957 to facilitate the peaceful use of atomic energy.
Meltdown: It refers to the melting of nuclear fuel rods in the reactor core, releasing radiation in the process. This happens when control rods are not able to control the chain reactions inside the core, or if cool water is not pumped into the reactor continuously.
In partial meltdown, the fuel rods may be only damaged, a portion of them having been left uncovered by cooling water long enough to crack, allowing the release of some radioactive elements in the fuel.
In full meltdown, all cooling water is lost and the rods become completely uncovered. Melting is all but guaranteed, as thousands of fuel pellets fall to the bottom of the reactor and heat themselves into a molten pool at several thousand degrees Celsius. The lava-like fuel might breach the reactor’s pressure vessel and then its containment, leading to widespread release of radioactivity.
Nuclear power plant: A facility that converts atomic energy into usable power.
Nuclear Reactor: A device that contains and controls sustained nuclear reactions. It produces heat that generates electricity.
Potassium iodide: A compound that scientists claim will give some protection from exposure to radioactive iodine-131, which is one of the fission products that can be released in a meltdown. Potassium iodide, however, will not give any protection against any other radioactive isotope that may be released in a meltdown at a nuclear power plant.
Pressurized water reactor: A common nuclear power reactor design in which very pure water is heated to a very high temperature by fission, kept under high pressure (to prevent it from boiling), and converted to steam by a steam generator. The resulting steam is used to drive turbines, which activate generators to produce electrical power.
Radiation: The particles or rays emitted from the nucleus of an unstable radioactive atom as a result of radioactive decay.
Radioactivity: The spontaneous decay of disintegration of an unstable atomic nucleus accompanied by the emission of radiation.
Sievert: A unit of measurement for radiation dosage. The World Health Organization says that the average person is exposed to 3 millisieverts a year of radiation from naturally occurring, medical and other sources. Exposure to 1,000 millisieverts (1 sievert) of radiation can cause radiation sickness.
Spill: The accidental release of radioactive materials.
Spent Fuel: The fuel rods which no longer have enough fissionable uranium to be efficiently used to produce power.
Spent Fuel Pool: An underwater storage and cooling facility for spent fuel assemblies that have been removed from a reactor.
Turbine: It transfers the heat from the coolant to electricity.
Uranium: A naturally radioactive and very dense element. Uranium-235 is the principal nuclear fuel material used in today’s nuclear power reactors.
Compiled by Lawrence de Guzman and Eliza Victoria, Inquirer Research
Sources: CNN; Global Development Research Center; Glossary of Environment Statistics; Lawrence Berkley National Laboratory; New York Times; United States Nuclear Regulatory Commission; whatisnuclear.com; world-nuclear.orgLinkback:
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