Pressurized water reactorA pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs constitute the large majority of the world's nuclear power plants (with notable exceptions being the UK, Japan and Canada). In a PWR, the primary coolant (water) is pumped under high pressure to the reactor core where it is heated by the energy released by the fission of atoms. The heated, high pressure water then flows to a steam generator, where it transfers its thermal energy to lower pressure water of a secondary system where steam is generated.
Traveling wave reactorA traveling-wave reactor (TWR) is a proposed type of nuclear fission reactor that can convert fertile material into usable fuel through nuclear transmutation, in tandem with the burnup of fissile material. TWRs differ from other kinds of fast-neutron and breeder reactors in their ability to use fuel efficiently without uranium enrichment or reprocessing, instead directly using depleted uranium, natural uranium, thorium, spent fuel removed from light water reactors, or some combination of these materials.
Decay heatDecay heat is the heat released as a result of radioactive decay. This heat is produced as an effect of radiation on materials: the energy of the alpha, beta or gamma radiation is converted into the thermal movement of atoms. Decay heat occurs naturally from decay of long-lived radioisotopes that are primordially present from the Earth's formation. In nuclear reactor engineering, decay heat continues to be generated after the reactor has been shut down (see SCRAM and nuclear chain reactions) and power generation has been suspended.
Minor actinideThe minor actinides are the actinide elements in used nuclear fuel other than uranium and plutonium, which are termed the major actinides. The minor actinides include neptunium (element 93), americium (element 95), curium (element 96), berkelium (element 97), californium (element 98), einsteinium (element 99), and fermium (element 100). The most important isotopes of these elements in spent nuclear fuel are neptunium-237, americium-241, americium-243, curium-242 through -248, and californium-249 through -252.
Atucha Nuclear Power PlantThe Atucha Nuclear Complex, or Atucha Nuclear Power Plant, is the location for two adjacent nuclear power plants in Lima, Zárate, Buenos Aires Province, about from Buenos Aires, on the right-hand shore of the Paraná de las Palmas River. Both are pressurized heavy-water reactors (PHWR) employing a mixture of natural uranium and enriched uranium (0.85% of 235U), and use heavy water for cooling and neutron moderation.
Fermi 1Fermi 1 was the United States' only demonstration-scale breeder reactor, built during the 1950s at the Enrico Fermi Nuclear Generating Station on the western shore of Lake Erie south of Detroit, Michigan. It used the sodium-cooled fast reactor cycle, in which liquid sodium metal is used as the primary coolant instead of more typical nuclear reactor designs which are cooled with water. Sodium cooling allows for a more compact core with surplus neutrons, which are used to produce more fission fuel by converting a surrounding "blanket" of 238U into 239Pu which can be fed back into a reactor.
Iodine-129Iodine-129 (129I) is a long-lived radioisotope of iodine which occurs naturally, but also is of special interest in the monitoring and effects of man-made nuclear fission products, where it serves as both tracer and potential radiological contaminant. 129I is one of seven long-lived fission products. It is primarily formed from the fission of uranium and plutonium in nuclear reactors. Significant amounts were released into the atmosphere as a result of nuclear weapons testing in the 1950s and 1960s.
Fluoride volatilityFluoride volatility is the tendency of highly fluorinated molecules to vaporize at comparatively low temperatures. Heptafluorides, hexafluorides and pentafluorides have much lower boiling points than the lower-valence fluorides. Most difluorides and trifluorides have high boiling points, while most tetrafluorides and monofluorides fall in between. The term "fluoride volatility" is jargon used particularly in the context of separation of radionuclides. Valences for the majority of elements are based on the highest known fluoride.
Online refuellingIn nuclear power technology, online refuelling is a technique for changing the fuel of a nuclear reactor while the reactor is critical. This allows the reactor to continue to generate electricity during routine refuelling, and therefore improve the availability and profitability of the plant. Online refuelling allows a nuclear reactor to continue to generate electricity during periods of routine refuelling, and therefore improves the availability and therefore the economy of the plant.
North Korea and weapons of mass destructionNorth Korea has a military nuclear weapons program and, as of early 2020, is estimated to have an arsenal of approximately 30 to 40 nuclear weapons and sufficient production of fissile material for six to seven nuclear weapons per year. North Korea has also stockpiled a significant quantity of chemical and biological weapons. In 2003, North Korea withdrew from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). Since 2006, the country has been conducting a series of six nuclear tests at increasing levels of expertise, prompting the imposition of sanctions.
