Long-lived fission productLong-lived fission products (LLFPs) are radioactive materials with a long half-life (more than 200,000 years) produced by nuclear fission of uranium and plutonium. Because of their persistent radiotoxicity, it is necessary to isolate them from humans and the biosphere and to confine them in nuclear waste repositories for geological periods of time. Nuclear fission produces fission products, as well as actinides from nuclear fuel nuclei that capture neutrons but fail to fission, and activation products from neutron activation of reactor or environmental materials.
Spontaneous fissionSpontaneous fission (SF) is a form of radioactive decay that is found only in very heavy chemical elements. The nuclear binding energy of the elements reaches its maximum at an atomic mass number of about 56 (e.g., iron-56); spontaneous breakdown into smaller nuclei and a few isolated nuclear particles becomes possible at greater atomic mass numbers. By 1908, physicists understood that alpha decay involved ejection of helium nuclei from a decaying atom. Like cluster decay, alpha decay is not typically categorized as a process of fission.
Chernobyl Nuclear Power PlantThe Chernobyl Nuclear Power Plant (ChNPP; Чорнобильська атомна електростанція; Чернобыльская атомная электростанция) is a nuclear power plant undergoing decommissioning. ChNPP is located near the abandoned city of Pripyat in northern Ukraine northwest of the city of Chernobyl, from the Belarus–Ukraine border, and about north of Kyiv. The plant was cooled by an engineered pond, fed by the Pripyat River about northwest from its juncture with the Dnieper.
Nuclear weapon designNuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three existing basic design types: pure fission weapons, the simplest, least technically demanding, were the first nuclear weapons built and, so far, the only type ever used in warfare, by the United States on Japan in World War II boosted fission weapons increase yield beyond that of the implosion design, by using small quantities of fusion fuel to enhance the fission chain reaction.
Critical massIn nuclear engineering, a critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties (specifically, its nuclear fission cross-section), density, shape, enrichment, purity, temperature, and surroundings. The concept is important in nuclear weapon design. When a nuclear chain reaction in a mass of fissile material is self-sustaining, the mass is said to be in a critical state in which there is no increase or decrease in power, temperature, or neutron population.
Nuclear power phase-outA nuclear power phase-out is the discontinuation of usage of nuclear power for energy production. Often initiated because of concerns about nuclear power, phase-outs usually include shutting down nuclear power plants and looking towards fossil fuels and renewable energy. Three nuclear accidents have influenced the discontinuation of nuclear power: the 1979 Three Mile Island partial nuclear meltdown in the United States, the 1986 Chernobyl disaster in the USSR (now Ukraine), and the 2011 Fukushima nuclear disaster in Japan.
Olkiluoto Nuclear Power PlantThe Olkiluoto Nuclear Power Plant (Olkiluodon ydinvoimalaitos, Olkiluoto kärnkraftverk) is one of Finland's two nuclear power plants, the other being the two-unit Loviisa Nuclear Power Plant. The plant is owned and operated by Teollisuuden Voima, and is located on Olkiluoto Island, on the shore of the Gulf of Bothnia, in the municipality of Eurajoki in western Finland, about from the town of Rauma and about from the city of Pori.
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.
Reduced moderation water reactorThe Reduced-Moderation Water Reactor (RMWR), also referred to as the Resource-renewable BWR, is a proposed type of light water moderated nuclear power reactor, featuring some characteristics of a fast neutron reactor, thereby combining the established and proven technology of light water reactors with the desired features of fast neutron reactors. The RMWR concept builds upon the Advanced Boiling Water Reactor and is under active development in theoretical studies, particularly in Japan.
Thermal-neutron reactorA thermal-neutron reactor is a nuclear reactor that uses slow or thermal neutrons. ("Thermal" does not mean hot in an absolute sense, but means in thermal equilibrium with the medium it is interacting with, the reactor's fuel, moderator and structure, which is much lower energy than the fast neutrons initially produced by fission.) Most nuclear power plant reactors are thermal reactors and use a neutron moderator to slow neutrons until they approach the average kinetic energy of the surrounding particles, that is, to reduce the speed of the neutrons to low-velocity, thermal neutrons.
