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Explore the people, places, events, achievements, struggles and stories that shaped our journey.
Movements, leaders, victories and the continuing fight for equality.
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Mansa Musa was the ruler of the Mali Empire in West Africa. Details recorded here should be sourced; unknown information is left blank.
MORE →Reflects the personal views, recollections, and perspective of the author, Mike Davis.
This is a personal recollection on the Move fire on May 13, 1985
A generation II reactor is a design classification for a nuclear reactor, and refers to the class of commercial reactors built until the end of the 1990s.[1] Prototypical and older versions of PWR, CANDU, IPHWR, BWR, AGR, RBMK and VVER are among them.[1]
These are contrasted to generation I reactors, which refer to the early prototype of power reactors, such as Shippingport, Magnox/UNGG, AMB, Fermi 1, and Dresden 1.[1] The last commercial Gen I power reactor was located at the Wylfa Nuclear Power Station[2] and ceased operation at the end of 2015. The nomenclature for reactor designs, describing four 'generations', was proposed by the US Department of Energy when it introduced the concept of generation IV reactors.
The designation generation II+ reactor is sometimes used for modernized generation II designs built post-2000, such as the Chinese CPR-1000, in competition with more expensive generation III reactor designs. Typically, the modernization includes improved safety systems and a 60-year design life.[citation needed]
Generation II reactor designs generally had an original design life of 30 or 40 years.[3] This date was set as the period over which loans taken out for the plant would be paid off. However, many generation II reactors are being life-extended to 50 or 60 years, and a second life-extension to 80 years may also be economical in many cases.[4] By 2013 about 75% of still operating U.S. reactors had been granted life extension licenses to 60 years.[5]
Chernobyl's No.4 reactor that exploded was a generation II reactor, specifically RBMK-1000.
Fukushima Daiichi's three destroyed reactors were generation II reactors; specifically Mark I Boiling water reactors (BWR) designed by General Electric. In 2016, unit 2 at the Watts Bar Nuclear Generating Station came online and is likely to be the last generation II reactor to become operational in the United States.
Many generation II PWRs built by American firms are custom designed for each specific plant, such as those built by Babcock&Wilcox, Combustion Engineering, and Westinghouse. In contrast, with BWRs, CANDUs, in France, Japan, Sweden, and in the Soviet Union with the VVER and the RBMK, reactor designs were highly standardized, allowing parts to be retrofitted and exchanged across plants. In Germany, BWRs and PWRs were highly standardized, designed by KWU[6] with the exception of the Pre-Konvoi PWR reactors which were not standarized.
Asea-atom, later ABB-atom, in Sweden, developed the standarized BWR-75 reactor design, of which 6 were built.
The only remaining commercial Gen I plant, the Wylfa Nuclear Power Station in Wales, was scheduled for closure in 2010. However, the UK Nuclear Decommissioning Authority announced in October 2010 that the Wylfa Nuclear Power Station will operate up to December 2012.
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 | This article about nuclear power and nuclear reactors for power generation is a stub. You can help Wikipedia by adding missing information. |
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A generation II reactor is a design classification for a nuclear reactor, and refers to the class of commercial reactors built until the end of the 1990s. Prototypical and older versions of PWR, CANDU, IPHWR, BWR, AGR, RBMK and VVER are among them. These are contrasted to generation I reactors, which refer to the early prototype of power reactors, such as Shippingport, Magnox/UNGG, AMB, Fermi 1, and Dresden 1. The last commercial Gen I power reactor was located at the Wylfa Nuclear Power Station and ceased operation at the end of 2015. The nomenclature for reactor designs, describing four 'generations', was proposed by the US Department of Energy when it introduced the concept of generation IV reactors. The designation generation II+ reactor is sometimes used for modernized generation II designs built post-2000, such as the Chinese CPR-1000, in competition with more expensive generation III reactor designs. Typically, the modernization includes improved safety systems and a 60-year design life. Generation II reactor designs generally had an original design life of 30 or 40 years. This date was set as the period over which loans taken out for the plant would be paid off. However, many generation II reactors are being life-extended to 50 or 60 years, and a second life-extension to 80 years may also be economical in many cases. By 2013 about 75% of still operating U.S. reactors had been granted life extension licenses to 60 years. Chernobyl's No.4 reactor that exploded was a generation II reactor, specifically RBMK-1000. Fukushima Daiichi's three destroyed reactors were generation II reactors; specifically Mark I Boiling water reactors (BWR) designed by General Electric. In 2016, unit 2 at the Watts Bar Nuclear Generating Station came online and is likely to be the last generation II reactor to become operational in the United States. Many generation II PWRs built by American firms are custom designed for each specific plant, such as those built by Babcock&Wilcox, Combustion Engineering, and Westinghouse. In contrast, with BWRs, CANDUs, in France, Japan, Sweden, and in the Soviet Union with the VVER and the RBMK, reactor designs were highly standardized, allowing parts to be retrofitted and exchanged across plants. In Germany, BWRs and PWRs were highly standardized, designed by KWU with the exception of the Pre-Konvoi PWR reactors which were not standarized. Asea-atom, later ABB-atom, in Sweden, developed the standarized BWR-75 reactor design, of which 6 were built.
Generation III reactors, or Gen III reactors, are a class of nuclear reactors designed to succeed Generation II reactors, incorporating evolutionary improvements in design. These include improved fuel technology, higher thermal efficiency, significantly enhanced safety systems (including passive nuclear safety), and standardized designs intended to reduce maintenance and capital costs. They are promoted by the Generation IV International Forum (GIF). The first Generation III reactors to begin operation were Kashiwazaki 6 and 7 advanced boiling water reactors (ABWRs) in 1996 and 1997. From 2012, both have been shut down due to a less permissive political environment in the wake of the Fukushima nuclear accident. Due to the prolonged period of stagnation in the construction of new reactors and the continued (albeit declining) popularity of Generation II/II+ designs in new construction, relatively few third generation reactors have been built.
A pressurized water reactor (PWR) is a type of light-water nuclear reactor. PWRs are the most common type of nuclear power reactor, representing almost 70% of the world's commercial reactor fleet. Some countries, such as Canada and (historically) the United Kingdom, have relied heavily on other designs (CANDU pressurized heavy‑water reactors and gas‑cooled reactors respectively) while others, including Japan and India, operate a mix of PWRs and other reactor types (notably boiling water reactors and pressurized heavy‑water reactors). In a PWR, water is used both as a neutron moderator and as coolant fluid for the reactor core. In the core, water is heated by the energy released by the fission of atoms contained in the fuel. Using high pressure (around 155 bar: 2250 psi) ensures that the water stays in a liquid state. The heated water then flows to a steam generator, where it transfers its thermal energy to the water of a secondary cycle kept at a lower pressure which allows it to vaporize. The resulting steam then drives steam turbines linked to an electric generator. A boiling water reactor (BWR) by contrast does not maintain such high pressure in the primary cycle and the water vaporizes inside the reactor pressure vessel before being sent to the turbine. Most PWR designs make use of two to six steam generators (although there are some experimental and smaller designs that use one steam generator), each associated with a coolant loop. PWRs were originally designed to serve as nuclear marine propulsion for nuclear submarines and were used in the original design of the second commercial power plant at Shippingport Atomic Power Station. PWRs are operated in the United States, France, Russia, China, South Korea and several other countries. The majority are Generation II reactors; newer Generation III designs such as the AP1000, Hualong One, APR-1400 and VVER-1000. New Generation III+ reactor designs: the AP1000, VVER-1200, CAP-1400, and EPR. The first AP1000 and EPR reactors were connected to the power grid in China in 2018.
The RBMK (Russian: Реактор большой мощности канальный, РБМК; reaktor bolshoy moshchnosti kanalnyy, "high-power channel-type reactor") is a class of graphite-moderated nuclear power reactor designed and built by the Soviet Union. It is somewhat like a boiling water reactor as water boils in the pressure tubes. It is one of two power reactor types to enter serial production in the Soviet Union during the 1970s, the other being the VVER reactor. The name refers to its design where instead of a large steel pressure vessel surrounding the entire core, the core is surrounded by a cylindrical annular steel tank inside a concrete vault and each fuel assembly is enclosed in an individual 8.4 cm (inner) diameter pipe (called a "technological channel"). The channels also contain the coolant, and are surrounded by graphite. The RBMK is an early Generation II reactor and the oldest commercial reactor design still in wide operation. Certain aspects of the original RBMK reactor design had several shortcomings, such as the large positive void coefficient, the 'positive scram effect' of the control rods and instability at low power levels—which contributed to the 1986 Chernobyl disaster, in which an RBMK experienced an uncontrolled nuclear chain reaction, leading to a steam and hydrogen explosion, large fire, and subsequent core meltdown. Radioactive material was released over a large portion of northern and southern Europe—including Sweden, where evidence of the nuclear disaster was first registered outside of the Soviet Union, and before the Chernobyl accident was communicated by the Soviet Union to the rest of the world. The disaster prompted worldwide calls for the reactors to be completely decommissioned; however, there is still considerable reliance on RBMK facilities for power in Russia with the aggregate power of operational units at almost 7 GW of installed capacity. Most of the flaws in the design of RBMK-1000 reactors were corrected after the Chernobyl accident and a dozen reactors have since been operating without any serious incidents for over thirty years. RBMK reactors may be classified as belonging to one of three distinct generations, according to when the particular reactor was built and brought online: Generation 1 – during the early-to-mid 1970s, before OPB-82 General Safety Provisions were introduced in the Soviet Union. Generation 2 – during the late 1970s and early 1980s, conforming to the OPB-82 standards issued in 1982. Generation 3 – post Chernobyl accident in 1986, where Soviet safety standards were revised to OPB-88; only Smolensk-3 was built to these standards. Beside RBMK, there are several other graphite-moderated reactors. A graphite-moderated Magnox reactor exists in North Korea at the Yongbyon Nuclear Scientific Research Center. While the gas cooled Magnox, AGR and pebble bed reactors (Such as the Dragon reactor at Winfrith) use graphite as moderators their use of gases (carbon dioxide for Magnox and AGR, while helium for Dragon) as heat transfer fluids causes them to have no void coefficient. 4 EGP-6 graphite water reactors which are a scaled down version of the RBMK were operating at the world's second northernmost nuclear power plant i.e. the Bilibino Nuclear Power Plant. One EGP-6 was shut down permanently in 2020. The remaining three EGP-6 were shut down permanently in December 2025.
Before the 1921 destruction of Tulsa’s Greenwood District, Black residents had created a remarkable center of business and community life. The district included stores, professional offices, entertainment venues and homes owned by Black citizens. Understanding Greenwood means learning what was built—not only what was burned.
MORE →Mae Jemison, aboard Space Shuttle Endeavour in 1992.
