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The actinide or actinoid series encompasses the 15 metallic chemical elements with atomic numbers from 89 to 103, actinium through lawrencium. The actinide series derives its name from the first element in the series, actinium. The informal chemical symbol An is used in general discussions of actinide chemistry to refer to any actinide.
Deuterium is one of two stable isotopes of hydrogen. The nucleus of a deuterium atom, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutrons in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom of deuterium among every 6,420 atoms of hydrogen. Thus deuterium accounts for approximately 0.0156% by number of all the naturally occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another.
Hafnium is a chemical element with the symbol Hf and atomic number 72. A lustrous, silvery gray, tetravalent transition metal, hafnium chemically resembles zirconium and is found in many zirconium minerals. Its existence was predicted by Dmitri Mendeleev in 1869, though it was not identified until 1923, by Dirk Coster and George de Hevesy, making it the penultimate stable element to be discovered. Hafnium is named after Hafnia, the Latin name for Copenhagen, where it was discovered.
Heavy water is a form of water whose hydrogen atoms are all deuterium rather than the common hydrogen-1 isotope that makes up most of the hydrogen in normal water. The presence of the heavier hydrogen isotope gives the water different nuclear properties, and the increase in mass gives it slightly different physical and chemical properties when compared to normal water.
Helium-3 is a light, stable isotope of helium with two protons and one neutron. Other than protium, helium-3 is the only stable isotope of any element with more protons than neutrons. Helium-3 was discovered in 1939.
Lithium is a chemical element with the symbol Li and atomic number 3. It is a soft, silvery-white alkali metal. Under standard conditions, it is the least dense metal and the least dense solid element. Like all alkali metals, lithium is highly reactive and flammable, and must be stored in vacuum, inert atmosphere, or inert liquid such as purified kerosene or mineral oil. It exhibits a metallic luster. It corrodes quickly in air to a dull silvery gray, then black tarnish. It does not occur freely in nature, but occurs mainly as pegmatitic minerals, which were once the main source of lithium. Due to its solubility as an ion, it is present in ocean water and is commonly obtained from brines. Lithium metal is isolated electrolytically from a mixture of lithium chloride and potassium chloride.
Tritium or hydrogen-3 is a rare and radioactive isotope of hydrogen with a half-life of about 12 years. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of the common isotope hydrogen-1 (protium) contains one proton and zero neutrons, and that of hydrogen-2 (deuterium) contains one proton and one neutron.
A period 2 element is one of the chemical elements in the second row of the periodic table of the chemical elements. The periodic table is laid out in rows to illustrate recurring (periodic) trends in the chemical behavior of the elements as their atomic number increases; a new row is started when chemical behavior begins to repeat, creating columns of elements with similar properties.
A natural nuclear fission reactor is a uranium deposit where self-sustaining nuclear chain reactions occur. The conditions under which a natural nuclear reactor could exist had been predicted in 1956 by Paul Kuroda. The remnants of an extinct or fossil nuclear fission reactor, where self-sustaining nuclear reactions have occurred in the past, can be verified by analysis of isotope ratios of uranium and of the fission products. An example of this phenomenon was discovered in 1972 in Oklo, Gabon by Francis Perrin under conditions very similar to Kuroda's predictions.
Isotope geochemistry is an aspect of geology based upon the study of natural variations in the relative abundances of isotopes of various elements. Variations in isotopic abundance are measured by isotope ratio mass spectrometry, and can reveal information about the ages and origins of rock, air or water bodies, or processes of mixing between them.
Neutron activation is the process in which neutron radiation induces radioactivity in materials, and occurs when atomic nuclei capture free neutrons, becoming heavier and entering excited states. The excited nucleus decays immediately by emitting gamma rays, or particles such as beta particles, alpha particles, fission products, and neutrons. Thus, the process of neutron capture, even after any intermediate decay, often results in the formation of an unstable activation product. Such radioactive nuclei can exhibit half-lives ranging from small fractions of a second to many years.
Hydrogen (1H) has three naturally occurring isotopes, sometimes denoted 1
H
, 2
H
, and 3
H
. 1
H
and 2
H
are stable, while 3
H
has a half-life of 12.32(2) years. Heavier isotopes also exist, all of which are synthetic and have a half-life of less than one zeptosecond (10−21 s). Of these, 5
H
is the least stable, while 7
H
is the most.
Nuclear fuel is material used in nuclear power stations to produce heat to power turbines. Heat is created when nuclear fuel undergoes nuclear fission.
In chemistry, isotopologues are molecules that differ only in their isotopic composition. They have the same chemical formula and bonding arrangement of atoms, but at least one atom has a different number of neutrons than the parent.
There are three known stable isotopes of oxygen (8O): 16
O
, 17
O
, and 18
O
.
An isotopic signature is a ratio of non-radiogenic 'stable isotopes', stable radiogenic isotopes, or unstable radioactive isotopes of particular elements in an investigated material. The ratios of isotopes in a sample material are measured by isotope-ratio mass spectrometry against an isotopic reference material. This process is called isotope analysis.
In applications such as nuclear reactors, a neutron poison is a substance with a large neutron absorption cross-section. In such applications, absorbing neutrons is normally an undesirable effect. However, neutron-absorbing materials, also called poisons, are intentionally inserted into some types of reactors in order to lower the high reactivity of their initial fresh fuel load. Some of these poisons deplete as they absorb neutrons during reactor operation, while others remain relatively constant.
A nucleogenic isotope, or nuclide, is one that is produced by a natural terrestrial nuclear reaction, other than a reaction beginning with cosmic rays. The nuclear reaction that produces nucleogenic nuclides is usually interaction with an alpha particle or the capture of fission or thermal neutrons. Some nucleogenic isotopes are stable and others are radioactive.
Nuclear transmutation is the conversion of one chemical element or an isotope into another chemical element. Nuclear transmutation occurs in any process where the number of protons or neutrons in the nucleus of an atom is changed.
Oklo Mine, located in Oklo, Gabon on the west coast of Central Africa, is believed to be the only natural nuclear fission reactor. Oklo consists of 16 sites at which self-sustaining nuclear fission reactions are thought to have taken place approximately 1.7 billion years ago, and ran for hundreds of thousands of years. It is estimated to have averaged under 100 kW of thermal power during that time.
References
- ↑ Hoefs, Jochen (1997). Stable Isotope Geochemistry. Springer Verlag. ISBN 978-3-540-40227-5.
- ↑ Blunier, Thomas; Bruce Barnett; Michael L. Bender; Melissa B. Hendricks (2002). "Biological oxygen productivity during the last 60,000 years from triple oxygen isotope measurements". Global Biogeochemical Cycles. 6. 16 (3): 1029. Bibcode:2002GBioC..16.1029B. doi: 10.1029/2001GB001460 .
- ↑ Arai, T.; S. Nakao; K. Mori; K. Ishimori; I. Morishima; T. Miyazawa; B. Fritz-Zieroth (31 May 1990). "Cerebral Oxygen Utilization Analyzed by the Use of Oxygen-17 and its Nuclear Magnetic Resonance". Biochem. Biophys. Res. Commun. 169 (1): 153–158. doi:10.1016/0006-291X(90)91447-Z. PMID 2350339.
- ↑ http://www.nrc.gov/docs/ML1016/ML101650129.pdf Estimation of Carbon-14 in Nuclear Power Plant Gaseous Effluents; EPRI; June 10, 2010
- ↑ A Compact, Low Cost, Tritium Removal Plant for Candu-6 Reactors; S.K. Sood, C. Fong, and K.M. Kalyanam; Ontario Hydro
- ↑ Blackett, P. M. S. (1925). "The Ejection of Protons from Nitrogen Nuclei, Photographed by the Wilson Method". Proceedings of the Royal Society of London. Series A. 107 (742): 349–360. Bibcode:1925RSPSA.107..349B. doi: 10.1098/rspa.1925.0029 .
- ↑ Rutherford, Ernest (1919). "Collision of alpha particles with light atoms IV. An anomalous effect in nitrogen". Philosophical Magazine. 6th series. 37: 581–587. doi:10.1080/14786440608635919.
- ↑ Giauque, W. F.; Johnston, H. L. (1929). "An Isotope of Oxygen, Mass 17, in the Earth's Atmosphere". J. Am. Chem. Soc. 51 (12): 3528–3534. doi:10.1021/ja01387a004.