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Portal:Nuclear technology

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The Nuclear Technology Portal

Introduction

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Uranium is a chemical element; it has symbol U and atomic number 92. It is a silvery-grey metal in the actinide series of the periodic table. A uranium atom has 92 protons and 92 electrons, of which 6 are valence electrons. Uranium radioactively decays, usually by emitting an alpha particle. The half-life of this decay varies between 159,200 and 4.5 billion years for different isotopes, making them useful for dating the age of the Earth. The most common isotopes in natural uranium are uranium-238 (which has 146 neutrons and accounts for over 99% of uranium on Earth) and uranium-235 (which has 143 neutrons). Uranium has the highest atomic weight of the primordially occurring elements. Its density is about 70% higher than that of lead and slightly lower than that of gold or tungsten. It occurs naturally in low concentrations of a few parts per million in soil, rock and water, and is commercially extracted from uranium-bearing minerals such as uraninite.

Many contemporary uses of uranium exploit its unique nuclear properties. Uranium-235 is the only naturally occurring fissile isotope, which makes it widely used in nuclear power plants and nuclear weapons. However, because of the low abundance of uranium-235 in natural uranium (which is, overwhelmingly, mostly uranium-238), uranium needs to undergo enrichment so that enough uranium-235 is present. Uranium-238 is fissionable by fast neutrons and is fertile, meaning it can be transmuted to fissile plutonium-239 in a nuclear reactor. Another fissile isotope, uranium-233, can be produced from natural thorium and is studied for future industrial use in nuclear technology. Uranium-238 has a small probability for spontaneous fission or even induced fission with fast neutrons; uranium-235, and to a lesser degree uranium-233, have a much higher fission cross-section for slow neutrons. In sufficient concentration, these isotopes maintain a sustained nuclear chain reaction. This generates the heat in nuclear power reactors and produces the fissile material for nuclear weapons. Depleted uranium (238U) is used in kinetic energy penetrators and armor plating.

The 1789 discovery of uranium in the mineral pitchblende is credited to Martin Heinrich Klaproth, who named the new element after the recently discovered planet Uranus. Eugène-Melchior Péligot was the first person to isolate the metal, and its radioactive properties were discovered in 1896 by Henri Becquerel. Research by Otto Hahn, Lise Meitner, Enrico Fermi and others, such as J. Robert Oppenheimer starting in 1934 led to its use as a fuel in the nuclear power industry and in Little Boy, the first nuclear weapon used in war. An ensuing arms race during the Cold War between the United States and the Soviet Union produced tens of thousands of nuclear weapons that used uranium metal and uranium-derived plutonium-239. Dismantling of these weapons and related nuclear facilities is carried out within various nuclear disarmament programs and costs billions of dollars. Weapon-grade uranium obtained from nuclear weapons is diluted with uranium-238 and reused as fuel for nuclear reactors. The development and deployment of these nuclear reactors continue globally as they are powerful sources of CO2-free energy. Spent nuclear fuel forms radioactive waste, which mostly consists of uranium-238 and poses a significant health threat and environmental impact. (Full article...)

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Credit: Cpl. Lynn P. Walker, Jr. (Marine Corps)
Battered religious figures stand watch on a hill above a tattered valley. Nagasaki, Japan. September 24, 1945, 6 weeks after the city was destroyed by the world's second atomic bomb attack. Photo by Cpl. Lynn P. Walker, Jr. (Marine Corps) NARA FILE #: 127-N-136176

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George Bogdanovich Kistiakowsky (Russian: Георгий Богданович Кистяковский, Ukrainian: Георгій Богданович Кістяківський, romanizedHeorhii Bohdanovych Kistiakivskyi; December 1 [O.S. November 18] 1900 – December 7, 1982) was a Ukrainian-American physical chemistry professor at Harvard who participated in the Manhattan Project and later served as President Dwight D. Eisenhower's Science Advisor.

Born in Boyarka in the old Russian Empire, into "an old Ukrainian Cossack family which was part of the intellectual elite in pre-revolutionary Russia", Kistiakowsky fled his homeland during the Russian Civil War. He made his way to Germany, where he earned his PhD in physical chemistry under the supervision of Max Bodenstein at the University of Berlin. He emigrated to the United States in 1926, where he joined the faculty of Harvard University in 1930, and became a citizen in 1933.

During World War II, Kistiakowsky was the head of the National Defense Research Committee (NDRC) section responsible for the development of explosives, and the technical director of the Explosives Research Laboratory (ERL), where he oversaw the development of new explosives, including RDX and HMX. He was involved in research into the hydrodynamic theory of explosions, and the development of shaped charges. In October 1943, he was brought into the Manhattan Project as a consultant. He was soon placed in charge of X Division, which was responsible for the development of the explosive lenses necessary for an implosion-type nuclear weapon. In July 1945, he watched the first atomic explosion in the Trinity test. A few weeks later, another implosion-type weapon (Fat Man) was dropped on Nagasaki.

From 1962 to 1965, Kistiakowsky chaired the National Academy of Sciences's Committee on Science, Engineering, and Public Policy (COSEPUP), and was its vice president from 1965 to 1973. He severed his connections with the government in protest against the war in Vietnam, and became active in an antiwar organization, the Council for a Livable World, becoming its chairman in 1977. (Full article...)

Nuclear technology news


16 July 2024 –
A malfunction causes an emergency shutdown of one of the four reactors at the Rostov Nuclear Power Plant in Rostov Oblast, Russia. Background radiation levels are reported as normal. (Reuters)
3 July 2024 – Russian invasion of Ukraine
Zaporizhzhia Nuclear Power Plant crisis
Three kamikaze drones attack an electrical substation for the Russian-held Zaporizhzhia Nuclear Power Plant, injuring eight workers, causing forest fires near the plant's switchyard, and leaving Enerhodar without power or water. (Reuters) (RFE/RL)

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