Deuterium oxide - definition of deuterium oxide by The Free Dictionary Deuterium oxide - definition of deuterium oxide by The Free Dictionary deuterium oxide n. Water in which deuterium replaces hydrogen, D2O, isolated for use as a moderator in certain nuclear reactors. deuterium oxide (Elements & Compounds) another name for heavy water ThesaurusAntonymsRelated WordsSynonymsLegend: heavy water moderator - any substance used to slow down neutrons in nuclear reactors Want to thank TFD for its existence? Tell a friend about us , add a link to this page, or visit the webmaster's page for free fun content . Link to this page: moderator References in periodicals archive ? In the deuterium oxide dose-to-mother technique, the mother consumes an accurately weighed dose of deuterium oxide, which rapidly equilibrates with her body water, including her milk.

'Energy efficient' orangutans need less food fuel than we do Identification of 3,4-Dihydroxy-2-oxo-butanal (L-threosone) as intermediate compound in oxidative degradation of dehydro-L-ascorbic acid and 2,3-diketo-L-gulonic acid in a deuterium oxide phosphate buffer. Copyright © 2003-2017 Farlex, Inc Disclaimer All content on this website, including dictionary, thesaurus, literature, geography, and other reference data is for informational purposes only. This information should not be considered complete, up to date, and is not intended to be used in place of a visit, consultation, or advice of a legal, medical, or any other professional. Deuterium oxide,Buy Deuterium oxide– Get Deuterium oxide,Deuterium oxide Suppliers,Deuterium oxide Sales NO.1 From: Mr.Anthony E-mail: ********** GREEN STONE company is the perfect choice for Deuterium oxide supplier. It frees you from worry about Product's quality, and its price is very reasonable, what' s more, they are free shipping all over the world.

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The average particle size is about 40-500 nm, and the purity is above 99.5%. News Deuterium oxide | Define Deuterium oxide at Dictionary.com deuterium oxide British Dictionary definitions for deuterium oxide Expand another name for heavy water Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012 NOVA | Hitler's Sunken Secret | Dangerous Water | PBS To Norwegian Resistance fighters during World War II, heavy water was a mysterious substance considered so perilous that they were willing, under orders from the Special Operations Executive in London, to sacrifice the lives of their countrymen in order to keep it out of Nazi hands. Learn more about heavy water—its discovery, uses, and why it remains a threat today—by clicking on the images above or simply scrolling down.—Susan K. Lewis What is it?

Heavy water is a form of water with a unique atomic structure and properties coveted for the production of nuclear power and weapons. Like ordinary water—H20—each molecule of heavy water contains two hydrogen atoms and one oxygen atom. The difference, though, lies in the hydrogen atoms. In ordinary water, each hydrogen atom has just a single proton in its nucleus. In heavy water, each hydrogen atom is indeed heavier, with a neutron as well as a proton in its nucleus. This isotope of hydrogen is called deuterium, and heavy water's more scientific name is deuterium oxide, abbreviated as D20. With the weight of extra neutrons, heavy-water ice will sink to the bottom of a beaker filled with ordinary H20. How is it Used in Nuclear Power Plants? Nuclear power plants harness the energy of countless atoms of uranium splitting apart, or fissioning, in a chain reaction. Heavy water can help keep such a chain reaction going. As each uranium atom breaks apart, it shoots out neutrons that can go on to split other atoms. But the neutrons are much more likely to trigger new fission events if they are slowed down.

Like traffic cops, heavy water's deuterium atoms effectively curb the pace of neutrons without capturing them. Nuclear reactors that use heavy water can employ a form of uranium commonly found in nature (U-238) rather than requiring so-called enriched uranium, which contains a higher percentage of easily split uranium atoms (U-235) but is expensive to produce. Heavy-water nuclear reactors generate electricity in China (above), Canada, and India. No commercial plants in the U.S. use heavy water. Why is it Dangerous? In its natural state, common uranium (U-238) can't generate destructive nuclear explosions. It either must be enriched—made more concentrated in a rare form of uranium (U-235)—or converted into plutonium (Pu-239). Heavy water can play a role in breeding weapons-grade plutonium from common uranium. In a heavy-water nuclear reactor, when neutrons bombard U-238, some uranium atoms absorb an additional neutron and are transformed into Pu-239. On the eve of World War II, scientists both in Germany and Great Britain realized that heavy water could be used in this way to make nuclear weapons.

And because this potential still exists today, the International Atomic Energy Agency and various national governments monitor the production and distribution of heavy water. Heavy water provides a path to turn common uranium into plutonium, one of the easily split or "fissile" materials that fuels nuclear bombs. What Countries Make It? When Norsk Hydro began producing heavy water in 1934, Norway became the first country with a commercial heavy-water plant. The Nazi invasion of Norway in 1940 transferred control of the plant—and most of the world's heavy water—to Germany. In the early 1940s, Allied countries joined the race for heavy water, and by 1944, the Manhattan Project had made 20 tons of the precious liquid, more than enough to fill the first heavy-water nuclear reactor. America's atomic weapons program ultimately relied more on graphite than on heavy water in nuclear reactors, but the United States has continued to produce heavy water for military use ever since the '40s. Today, Canada and India, which both rely on heavy-water nuclear power plants for electricity, make the most heavy water. Other countries with heavy-water production facilities include Argentina, Iran, Romania, and Russia.

Satellite images taken in February 2005 reveal a heavy-water plant in Arak, Iran. Iran claims the facility will help the country produce electricity, not plutonium for bombs. How Was it Discovered? In 1913, chemists Arthur Lamb and Richard Leen at New York University tried to find a definitive value for the density of pure water, but despite meticulous experiments, they kept getting varying results. Their "failure" was, in retrospect, important evidence for the existence both of heavy water and of isotopes—atoms of an element that have the same number of protons but a different number of neutrons and, therefore, different weights. That same year, independently, the notion of an isotope was proposed for the first time. By 1931, the existence of isotopes was firmly established, and Harold Urey at Columbia University, together with colleague George Murphy, first glimpsed hydrogen's heavier isotope deuterium using a technology called spectroscopy. They later distilled deuterium from liquid hydrogen, clinching proof of its existence. Urey won the Nobel Prize in Chemistry in 1934 for discovering deuterium, the key component of heavy water.

Gilbert Lewis, a renowned chemist at U.C. Berkeley, isolated the first sample of essentially pure heavy water from ordinary water in 1933. How is it Made? Heavy water is naturally present in ordinary water, so it's more accurate to speak of "isolating" rather than "making" it. Separating out significant quantities, though, is no easy trick because heavy water constitutes only one part in 4,500. Gilbert Lewis isolated the first samples in 1933 using electrolysis—sending an electric current through water to separate it into its elements. His technique relied on the fact that H20 breaks apart more readily than D20, and the residual water left after electrolysis is relatively rich in D20. By reprocessing the residual water over and over again, he could eventually purify heavy water. With his lab equipment, however, Lewis's process was time-consuming and expensive. Norsk Hydro, which already used electrolytic cells in the early 1930s to make fertilizer, seized the chance to make heavy water on an industrial scale.

By 1935, the Norwegian company was shipping heavy water to scientists throughout Europe who wanted it for physics, chemistry, and biomedical research. Today, heavy water is isolated in a variety of ways, including a distillation method akin to making brandy from wine. Other methods exploit the different affinities that deuterium and hydrogen have for various compounds. After the Nazis took control of the Norsk Hydro plant in 1940, they expanded the number of electrolytic cells from nine to 18, doubling the plant's production of heavy water. Product Name Deuterium oxide | Sigma-Aldrich Note: This product can be packaged on demand. For information on pricing, availability and packaging of custom sizes, please contact Stable Isotopes Customer Service .

Sodium acetate + water in deuterium oxide, 99.9 atom % D 1 Product Result deuterium oxide | Sigma-Aldrich deuterium oxide EMAIL THIS PAGE TO A FRIEND To Email: Select the checkbox on up to 4 items, then click 'compare' for a detailed product comparison *Please select more than one item to compare Empirical Formula (Hill Notation): D2O Molecular Weight: 20.03 Note: This product can be packaged on demand. For information on pricing, availability and packaging of custom sizes, please contact Stable Isotopes Customer Service . Deuterium oxide Linear Formula: D₂O Molecular Weight: 20.03 g/mol Synonym: Heavy water-d2,18O, Unnormalized water-18O Linear Formula: D218O Note: This product can be packaged on demand. For information on pricing, availability and packaging of custom sizes, please contact Stable Isotopes Customer Service . Deuterium oxide-18O Note: This product can be packaged on demand. For information on pricing, availability and packaging of custom sizes, please contact Stable Isotopes Customer Service .

Sodium acetate + water in deuterium oxide, 99.9 atom % D 1 Product Result Synonym: Acetic-d3 acid-d, Tetradeuteroacetic acid Linear Formula: CD3CO2D Empirical Formula (Hill Notation): C4H5BrO2 Molecular Weight: 164.99 Deuterium Oxide | Definition of Deuterium Oxide by Merriam-Webster Britannica.com: Encyclopedia article about deuterium oxide Seen and Heard What made you want to look up deuterium oxide? Please tell us where you read or heard it (including the quote, if possible). Heavy_water Heavy_water (at 25 °C, 100 kPa) Infobox disclaimer and references Heavy water is water which contains a higher proportion than normal of the isotope deuterium , as deuterium oxide, D2O or ²H2O, or as deuterium protium oxide, HDO or ¹H²HO. [1] Its physical and chemical properties are somewhat similar to those of water , H2O.

Heavy water may contain as much as 100% D2O, and usually the term refers to water which is highly enriched in deuterium. The isotopic substitution with deuterium alters the bond energy of the hydrogen-oxygen bond in water, altering the physical, chemical, and especially biological properties of the pure or highly-enriched substance to a larger degree than is found in most isotope-substituted chemical compounds. Heavy water should not be confused with hard water or with tritiated water. Contents Other meanings Semiheavy water Semiheavy water, HDO, also exists whenever there is water with hydrogen-1 (or protium ) and deuterium present in the mixture. This is because hydrogen atoms (hydrogen-1 and deuterium) are rapidly exchanged between water molecules. Water containing 50% H and 50% D in its hydrogen actually contains about 50% HDO and 25% each of H2O and D2O, in dynamic equilibrium . Semiheavy water, HDO, occurs naturally in regular water at a proportion of about 1 molecule in 3,200 (each hydrogen has a probability of 1 in 6,400 of being D).

Heavy water, D2O, by comparison, occurs naturally at a proportion of about 1 molecule in 41 million (i.e., 1 in 6,4002). Heavy-oxygen water A common type of heavy- oxygen water H218O is available commercially for use as a non-radioactive isotopic tracer (see doubly-labeled water for discussion), and qualifies as "heavy water" insofar as having a higher density than normal water (in this case, similar density to deuterium oxide). Even more expensively, water is available in which the oxygen is 17O. However, these types of heavy-isotope water are rarely referred to as "heavy water", as they do not contain the deuterium which gives D2O its characteristically different nuclear and biological properties. Heavy-oxygen waters with normal hydrogen, for example, would not be expected to show any toxicity whatsoever (see discussion of toxicity below). Physical properties (with comparison to light water) Property 7.41 (sometimes "pD") 7.00 No physical properties are listed for "pure" semi-heavy water, because it cannot be isolated in bulk quantities.

In the liquid state, a few water molecules are always in an ionised state , which means the hydrogen atoms can exchange among different oxygen atoms. A sample of hypothetical "pure" semi-heavy water would rapidly transform into a dynamic mixture of 25% light water, 25% heavy water, and 50% semi-heavy water. Physical properties obvious by inspection: Heavy water is 10.6% more dense than ordinary water, a difference which is nearly impossible to notice in a sample of it (which otherwise looks and tastes exactly like normal water). One of the few ways to demonstrate heavy water's physically different properties without equipment, is to freeze a sample and drop it into normal water. Ice made from heavy water sinks in normal water. If the normal water is ice-cold this phenomenon may be observed long enough for a good demonstration, since heavy-water ice has a slightly higher melting-temperature (3.8 °C) than normal ice, and thus holds up very well in ice-cold normal water. [1] History Harold Urey discovered the isotope deuterium in 1931 and was later able to concentrate it in water.

Urey's mentor Gilbert Newton Lewis isolated the first sample of pure heavy water by electrolysis in 1933. George de Hevesy and Hoffer used heavy water in 1934 in one of the first biological tracer experiments, to estimate the rate of turnover of water in the human body. The history of large-quantity production and use of heavy water in early nuclear experiments is given below. [2] Effect on biological systems Heavy isotopes of chemical elements have very slightly different chemical behaviors, but for most elements the differences in chemical behavior between isotopes are far too small to use, or even detect. For hydrogen, however, this is not true. The larger chemical isotope-effects seen with deuterium and tritium manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass of the nucleus and electrons appears. This quantity is altered in heavy-hydrogen compounds (of which deuterium oxide is the most common and familiar) far more than for heavy-isotope substitution in other chemical elements. This isotope effect of heavy hydrogen is magnified further in biological systems, which are very sensitive to small changes in the solvent properties of water.

To perform their tasks, enzymes rely on their finely tuned networks of hydrogen bonds , both in the active center with their substrates, and outside the active center, to stabilize their tertiary structures . As a hydrogen bond with deuterium is slightly stronger than one involving ordinary hydrogen, in a highly deuterated environment, some normal reactions in cells are disrupted. Particularly hard-hit by heavy water are the delicate assemblies of mitotic spindle formation necessary for cell division in eukaryotes. Because eukaryotic cell division stops in heavy water, seeds therefore do not germinate in heavy water, and plants stop growing when given only heavy water. Effect on animals Experiments in mice, rats, and dogs [3] have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy water (90%) rapidly kills fish, tadpoles, flatworms, and drosophila. Mammals such as rats given heavy water to drink die after a week, at a time when their body water approaches about 50% deuteration.

The mode of death appears to be the same as that in cytotoxic poisoning (such as chemotherapy ) or in acute radiation syndrome (though deuterium is not radioactive), and is due to deuterium's action in generally inhibiting cell division. Deuterium oxide is used to enhance boron neutron capture therapy . [3] It is more toxic to malignant cells than normal cells but the concentrations needed are too high for regular use. [3] As in chemotherapy, deuterium-poisoned mammals die of a failure of bone marrow (bleeding and infection) and intestinal-barrier functions (diarrhea and fluid loss). Notwithstanding the problems of plants and animals in living with too much deuterium, prokaryotic organisms such as bacteria (which do not have the mitotic problems induced by deuterium) may be grown and propagated in fully deuterated conditions, resulting in replacement of all hydrogen atoms in the bacterial proteins and DNA with the deuterium isotope. [3] Full replacement with heavy atom isotopes can be accomplished in higher organisms with other non-radioactive heavy isotopes (such as carbon-13 and nitrogen-15), but this cannot be done for the stable heavy isotope of hydrogen.

Toxicity in humans Because it would take a very great deal of heavy water to replace 25% to 50% of a human being's body water (which in turn is 70% of body weight) with heavy water, accidental or intentional poisoning with heavy water is unlikely to the point of practical disregard. For a poisoning, large amounts of heavy water would need to be ingested without significant normal water intake for many days to produce any noticeable toxic effects (although in a few tests, volunteers drinking large amounts of heavy water have reported dizziness, a possible effect of density changes in the fluid in the inner ear). For example, a 70 kg human containing 50 kg of water and drinking 3 liters of pure heavy water per day, would need to do this for almost 5 days to reach 25% deuteration, and for about 11 days to approach 50% deuteration. Thus, it would take a week of drinking nothing but pure heavy water for a human to begin to feel ill, and 10 days to 2 weeks (depending on water intake) for severe poisoning and death.

In the highly unlikely event that a human were to receive a toxic dose of heavy water, the treatment would involve the use of intravenous water replacement (due to possible intestinal dysfunction and problems with absorption of fluids). This would be done via 0.9% (normal physiologic) saline solution with other salts as needed, perhaps in conjunction with diuretics. Oral doses of heavy water in the multi-gram range, along with heavy oxygen 18O, are routinely used in human metabolic experiments. See doubly-labeled water testing. Since 1 in every 6400 hydrogen atoms is deuterium, a 50 kg human containing 32 kg of body water would normally contain enough deuterium (about 1.1 gram) to make 5.5 grams of pure heavy water, so roughly this dose is required to double the amount of deuterium in the body. Confused report of a "heavy water" contamination incident In 1990, a disgruntled employee at the Point Lepreau Nuclear Generating Station in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat transport loop of the nuclear reactor, and loaded it into the employee water cooler.

Eight employees drank some of the contaminated water. The incident was discovered when employees began leaving bioassay urine samples with elevated tritium levels. The quantity of heavy water involved was far below levels which could induce heavy water toxicity per se, but several employees received elevated radiation doses from tritium and neutron-activated chemicals in the water. [4] This was not an incident of heavy water poisoning, but rather radiation poisoning from other isotopes in the heavy water. Some news services were not careful to distinguish these points, and some of the public was left with the impression that heavy water is normally radioactive and more severely toxic than it is. Even if pure heavy water had been used in the water cooler indefinitely, it is not likely the incident would have been detected or caused harm, since no employees would be expected to get as much as 25% of their daily drinking water from such a source. [5] Production On Earth, semiheavy water, HDO, occurs naturally in regular water at a proportion of about 1 molecule in 3200. This means that 1 in 6400 hydrogen atoms is deuterium, which is 1 part in 3200 by weight (hydrogen weight).

The HDO may be separated from regular water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect . (For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water .) The difference in mass between the two hydrogen isotopes translates into a difference in the zero-point energy and thus into a slight difference in the speed at which the reaction proceeds. Once HDO becomes a significant fraction of the water, heavy water will become more prevalent as water molecules trade hydrogen atoms very frequently. To produce pure heavy water by distillation or electrolysis requires a large cascade of stills or electrolysis chambers, and consumes large amounts of power, so the chemical methods are generally preferred. The most important chemical method is the Girdler sulfide process. United States In 1953, the United States began using heavy water in plutonium production reactors at the Savannah River Site. The first of the five heavy water reactors came online in 1953, and the last was placed in cold shutdown in 1996. The SRS reactors were heavy water reactors so that they could produce both plutonium and tritium for the US nuclear weapons program.

The U.S. developed the Girdler Sulfide chemical exchange production process which was first demonstrated on a large scale at the Dana, Indiana plant in 1945 and at the Savannah River Plant, South Carolina in 1952. The SRP was operated by DuPont for the USDOE until April 1, 1989 at which time the operation was taken over by Westinghouse. Norway In 1934, Norsk Hydro built the first commercial heavy water plant at Vemork, Tinn, with a capacity of 12 tonnes per year. From 1940 and throughout World War II, the plant was under German control and the allies decided to destroy the plant and its heavy water to inhibit German development of nuclear weapons. In late 1942, a raid by British paratroopers failed when the gliders they were in crashed. All the raiders were killed in the crash or shot by German army troops. But in the night of 27 February 1943 Operation Gunnerside succeeded. Norwegian commandos managed to demolish small but key bits of the electrolytic cells, dumping the accumulated heavy water down the factory drains.

Arguably (see below) this prevented Germany from building a nuclear reactor (German nuclear weapons would not have automatically followed the reactor for many reasons). The Norsk Hydro operation is one of the great commando/sabotage operations of the war. On 16 November 1943, the allied air forces dropped more than 400 bombs on the site. The allied air raid prompted the Nazi government to move all available heavy water to Germany for safekeeping. On 20 February 1944, a Norwegian partisan sank the ferry M/F Hydro carrying the heavy water across Lake Tinn, at the cost of 14 Norwegian civilians, and most of the heavy water was presumably lost. A few of the barrels were only half full, and therefore could float, and may have been salvaged and transported to Germany.

(These events were dramatized in the 1965 movie, The Heroes of Telemark.) However, recent investigation of production records at Norsk Hydro and analysis of an intact barrel that was salvaged in 2004 revealed that although the barrels in this shipment contained water of pH 14 — indicative of the alkaline electrolytic refinement process — they did not contain high concentrations of D2O. Despite the apparent size of shipment, the total quantity of pure heavy water was quite small, each barrel only containing between 1/2–1% pure heavy water. The Germans would have needed a total of about 5 tons of heavy water to get a nuclear reactor running. The manifest clearly indicated that there was only half a ton of heavy water being transported to Germany. The Hydro was carrying far too little heavy water for even one reactor, let alone the 10 or more tons needed to make enough plutonium for a nuclear weapon. The Hydro shipment on 20 February 1944 was probably destined for an experimental reactor project.

Canada As part of its contribution to the Manhattan Project, Canada built and operated a 6 tonnes per year electrolytic heavy water plant at Trail, BC, which started operation in 1943. The Atomic Energy of Canada Limited (AECL) design of power reactor requires large quantities of heavy water to act as a neutron moderator and coolant. AECL ordered two heavy water plants which were built and operated in Atlantic Canada at Glace Bay (by Deuterium of Canada Limited) and Port Hawkesbury, Nova Scotia (by General Electric Canada). These plants proved to have significant design, construction and production problems and so AECL built the Bruce Heavy Water Plant, which it later sold to Ontario Hydro, to ensure a reliable supply of heavy water for future power plants. The two Nova Scotia plants were shut down in 1985 when their production proved to be unnecessary. The Bruce Heavy Water Plant in Ontario was the world's largest heavy water production plant with a capacity of 700 tonnes per year. It used the Girdler sulfide process to produce heavy water, and required 340,000 tonnes of feed water to produce one tonne of heavy water.

It was part of a complex that included 8 CANDU reactors which provided heat and power for the heavy water plant. The site was located at Douglas Point in Bruce County on Lake Huron where it had access to the waters of the Great Lakes. The Bruce plant was commissioned in 1979 to provide heavy water for a large increase in Ontario's nuclear power generation. The plants proved to be significantly more efficient than planned and only three of the planned four units were eventually commissioned. In addition, the nuclear power programme was slowed down and effectively stopped due to a perceived oversupply of electricity, later shown to be temporary, in 1993. Improved efficiency in the use and recycling of heavy water plus the over-production at Bruce left Canada with enough heavy water for its anticipated future needs. Also, the Girdler process involves large amounts of hydrogen sulfide , raising environmental concerns if there should be a release. The Bruce heavy-water plant was shut down in 1997, after which the plant was gradually dismantled and the site cleared. Atomic Energy of Canada Limited (AECL) is currently researching other more efficient and environmentally benign processes for creating heavy water.

This is essential for the future of the CANDU reactors since heavy water represents about 20% of the capital cost of each reactor. India India is the world's second largest producer of heavy water through its Heavy Water Board. Iran On August 26, 2006, Iranian President Ahmadinejad inaugurated an expansion of the country's heavy-water plant near Arak. Iran has indicated that the heavy-water production facility will operate in tandem with a 40 MW research reactor that has a scheduled completion date in 2009. [6] In an interview which aired on the Iranian News Channel (IRINN) on August 27, 2006, Iranian Nuclear Chief Mohammad Sa'idi claimed that heavy water could be used to treat AIDS and cancer. Daily consumption was recommended. [7] Other countries Argentina is another declared producer of heavy water, using an ammonia/hydrogen exchange based plant supplied by Switzerland's Sulzer company. Romania also produces heavy water at the Drobeta Girdler Sulfide plant and has exported from time to time. France operated a small plant during the 1950s and 1960s.

United Kingdom The Department of Atomic Energy built a station at Loch Morar in 1947, possibly investigating using the loch as a source of heavy water. [8] Applications Nuclear magnetic resonance Deuterium oxide is used in nuclear magnetic resonance spectroscopy when the solvent of interest is water and the nuclide of interest is hydrogen. This is because the signal from the water solvent would interfere with the signal from the molecule of interest. Deuterium has a different magnetic moment from hydrogen and therefore does not contribute to the NMR signal at the hydrogen resonance frequency. Neutron moderator Heavy water is used in certain types of nuclear reactors where it acts as a neutron moderator to slow down neutrons so that they can react with the uranium in the reactor. The CANDU reactor uses this design. Light water also acts as a moderator but because light water absorbs more neutrons than heavy water, reactors using light water must use enriched uranium rather than natural uranium, otherwise criticality is impossible. The use of heavy water essentially increases the efficiency of the nuclear reaction.

Because of this, heavy water reactors will be more efficient at breeding plutonium (from uranium-238 ) or uranium-233 (from thorium-232 ) than a comparable light-water reactor, leading them to be of greater concern in regards to nuclear proliferation. The breeding and extraction of plutonium can be a relatively rapid and cheap route to building a nuclear weapon, as chemical separation of plutonium from fuel is easier than isotopic separation of U-235 from natural uranium. Heavy water moderated research reactors or specifically-built plutonium breeder reactors have been used for this purpose by most, if not all, states which possess nuclear weapons, although historically the first nuclear weapons were produced without it. (Pure carbon may be used as a moderator, even in unenriched uranium nuclear reactors. Thus, in the U.S., the first experimental atomic reactor (1942), as well as the Manhattan Project Hanford production reactors which produced the plutonium for the Trinity test and Fat Man bombs, all used pure carbon neutron moderators and functioned with neither enriched uranium nor heavy water).

There is no evidence that civilian heavy water power reactors, such as the CANDU or Atucha designs, have been used for military production of fissile materials. In states which do not already possess nuclear weapons, the nuclear material at these facilities is under IAEA safeguards to discourage any such diversion. Due to its potential for use in nuclear weapons programs, the possession or import/export of large industrial quantities of heavy water are subject to government control in several countries. Suppliers of heavy water and heavy water production technology typically apply IAEA (International Atomic Energy Agency) administered safeguards and material accounting to heavy water. (In Australia, the Nuclear Non-Proliferation (Safeguards) Act 1987.) In the U.S. and Canada, non-industrial quantities of heavy water (i.e., in the gram to kg range) are routinely available through chemical supply dealers, and directly commercial companies such as the world's former major producer Ontario Hydro, without special license. Current (2006) cost of a kilogram of 99.98% reactor-purity heavy water, is about $600 to $700.

Smaller quantities of reasonable purity (99.9%) may be purchased from chemical supply houses at prices of roughly $1 per gram. Neutrino detector The Sudbury Neutrino Observatory (SNO) in Sudbury, Ontario uses 1000 tonnes of heavy water on loan from Atomic Energy of Canada Limited. The neutrino detector is 6800 feet underground in a deep mine, in order to shield it from muons produced by cosmic rays . SNO was built to answer the question of whether or not electron-type neutrinos produced by fusion in the Sun (the only type the Sun should be producing directly, according to theory) might be able to turn into other types of neutrinos on the way to Earth. SNO detects the Čerenkov radiation in the water from high-energy electrons produced from electron-type neutrinos as they undergo reactions with neutrons in deuterium , turning them into protons and electrons (only the electrons move fast enough to be detected in this manner). SNO also detects the same radiation from neutrino↔electron scattering events, which again produces high energy electrons. These two reactions are produced only by electron-type neutrinos.

The use of deuterium is critical to the SNO function, because all three "flavours" (types) of neutrinos [9] may be detected in a third type of reaction, neutrino-disintegration, in which a neutrino of any type (electron, muon, or tau) scatters from a deuterium nucleus ( deuteron ), transferring enough energy to break up the loosely-bound deuteron into a free neutron and proton . This event is detected when the free neutron is absorbed by 35Cl− present from NaCl which has been deliberately dissolved in the heavy water, causing emission of characteristic capture gamma rays. Thus, in this experiment, heavy water not only provides the transparent medium necessary to produce and visualize Čerenkov radiation, but it also provides deuterium to detect exotic mu type (μ) and tau (τ) neutrinos, as well as a non-absorbent moderator medium to preserve free neutrons from this reaction, until they can be absorbed by an easily-detected neutron-activated isotope. Metabolic rate testing in physiology/biology Heavy water is employed as part of a mixture with H218O for a common and safe test of mean metabolic rate in humans and animals undergoing their normal activities.

This metabolic test is usually called the doubly-labeled water test. Space-based non-toxic cooling systems Heavy water (D2O) has a similar high heat of fusion to regular water, but freezes at a slightly higher temperature. It has been proposed as a non-toxic heatsink for space based cooling applications, where D2O ice acts as a heatsink to remove water vapor in air, but without danger that the water vapor will freeze to water-ice, because D2O ice maintains temperatures too high for this to occur. See U.S. Patent 5,246,061 . Such a system has not yet been tested. Tritium production Tritium is an important material in nuclear weapon design for boosted fission weapons and initiators, and also has civilian industrial applications. Some is created in heavy water moderated reactors when deuterium captures a neutron. This reaction has a small cross-section and produces only small amounts of tritium, although enough so that cleaning tritium from the moderator may be desirable after several years to reduce the risk of tritium escape and radiation exposure.

Production of large amounts of tritium in this way would require reactors with very high neutron fluxes, or with a very high proportion of heavy water to nuclear fuel and very low neutron absorption by other reactor material. The tritium would then have to be recovered by isotope separation from a much larger quantity of deuterium, unlike tritium production from lithium-6 (the present method of tritium production), where only chemical separation is needed. Deuterium's absorption cross section for thermal neutrons is .52 millibarns, while oxygen-16 's is .19 millibarns and oxygen-17 's is .24 barn. 17O makes up .038% of natural oxygen , which has an overall absorption cross section of .28 millibarns. Therefore in D2O with natural oxygen, 21% of neutron captures are on oxygen, a proportion that may rise further as 17O accumulates from neutron capture on 16O. Also, 17O emits an alpha particle on capture, producing radioactive carbon-14 .

Heavy water in popular culture The song "Distant Early Warning" by Rush contains the line "There's no swimming in the heavy water, no singing in the acid rain". The fictional superhero Jay Garrick, "The Flash" acquired his powers of superspeed in a laboratory mishap involving experiments with heavy water. He fell asleep working late at night and inhaled the heavy water fumes until morning. The novel Specific Gravity by J. Matthew Neal (2007) features a victim who is slowly poisoned by deuterium oxide placed in his drinking water. Heavy water is shown as a part of a secret Nazi experiment in a Hogan's Heroes episode, "Go light on the heavy water". Chaplain Tappman from Joseph Heller's novel Closing Time mysteriously excretes heavy water instead of urine. The band Styx have a song titled "Heavy Water" on their album Brave New World. The novel Hominids by Robert J. Sawyer (2002) features a fictionalized account of the Sudbury Neutrino Observatory, which is mentioned above. Heavy water is sought by the Eurondans in Stargate SG-1 episode The Other Side.

The Thomas Dolby song "One of Our Submarines" contains the line, "Drinking heavy water from a stone." Dolby has admitted that when he wrote the song, he had no idea exactly what heavy water is. In the animated TV series G.I. Joe: A Real American Hero (1983), heavy water was one of three elements needed to power the M.A.S.S. device. In the text based web game Ogame Heavy water known as Deuterium is used as an important fuel in different applications such as buildings and fuel for ships. See also Heavy water | Gravity Wiki | Fandom powered by Wikia Infobox references Heavy water is water containing a higher-than-normal proportion of the hydrogen isotope deuterium , either as deuterium oxide, D2O or ²H2O, or as deuterium protium oxide, HDO or ¹H²HO. [1] Physically and chemically, it resembles water , H2O; in water, the deuterium-to-hydrogen ratio is about 156ppm, (see Vienna Standard Mean Ocean Water ).

Heavy water is water that was highly enriched in deuterium , by as much as 100% D2O. The isotopic substitution with deuterium alters the bond energy of the water's hydrogen- oxygen bond, altering the physical, chemical, and, especially, the biological properties of the pure, or highly-enriched, substance to a degree greater than is found in most isotope-substituted chemical compounds. Pure heavy water is not radioactive . It is about 11% denser than water, but otherwise, is physically very similar to water. Heavy water exhibits dose and species-dependent chemical toxicity. The adult human body naturally contains deuterium equivalent to that in five grams of heavy water, which is thought to be harmless. Comparable laboratory doses are used as non- radioactive tracers in human and animal metabolic experimentation. However, larger concentrations of heavy water are toxic in eukaryotic organisms, when heavy water replaces about 25% to 50% of the body's water. At these levels, the substance interferes with cellular mitotic apparatus , preventing cell-division. Single-celled prokaryotic organisms such as bacteria , which do not have a mitotic apparatus, may survive and grow slowly in heavy water.

However, eukaryotic organisms as simple as single-celled protozoa, and including all higher (multi-cellular) organisms, if given only heavy water, soon stop dividing and growing. For example, plant seeds will not germinate in heavy water. Mammals given heavy water fall ill from lack of needed blood-cell and intestinal-cell replacement, and die when about 50% of their body-water has been replaced with heavy water. Relatively pure heavy water was produced in 1933, soon after the discovery of deuterium , the stable heavy isotope of hydrogen. With the discovery of nuclear fission in late 1938, and the need for a neutron moderator that captured few neutrons, heavy water became an important component of early nuclear energy programs during World War II (1939–1945). Partly because of Nazi Germany 's (1933–1945) technological reliance upon scarce heavy water for nuclear reactor research, they failed to produce a functioning nuclear reactor during the duration of the war.

Since then, heavy water is an essential component in the design of some nuclear reactors, either for generating electric power or for producing nuclear-weapons isotopes, such as plutonium-239 . Most contemporary enriched- uranium nuclear reactors use normal "light water" (H2O) for neutron moderation. Contents Edit Semiheavy water, HDO, exists whenever there is water with hydrogen-1 (or protium ) and deuterium present in the mixture. This is because hydrogen atoms (hydrogen-1 and deuterium) are rapidly exchanged between water molecules. Water containing 50% H and 50% D in its hydrogen actually contains about 50% HDO and 25% each of H2O and D2O, in dynamic equilibrium . Semiheavy water, HDO, occurs naturally in regular water at a proportion of about 1 molecule in 3,200 (each hydrogen has a probability of one in 6,400 of being D). Heavy water, D2O, by comparison, occurs naturally at a proportion of about 1 molecule in 41 million (i.e., one in 6,4002).

This makes semiheavy water far more prevalent than "normal" heavy water. Heavy-oxygen water Edit A common type of heavy-oxygen water H218O is available commercially for use as a non-radioactive isotopic tracer (see doubly-labeled water for more information), and it qualifies as "heavy water" in that it has a higher density than normal water (in this case, similar density to deuterium oxide). At higher expense (due to the greater difficulty in separation of O-17, a less common heavy isotope of oxygen), water is available in which the oxygen is enriched to varying degrees with 17O. These types of heavy-isotope water are rarely referred to as "heavy water", as they do not contain the deuterium which gives D2O its characteristically different nuclear and biological properties. Heavy-oxygen waters with normal hydrogen, for example, would not be expected to show any toxicity whatsoever (see discussion of toxicity below). Physical properties (with comparison to light water) Edit Harold Urey discovered the isotope deuterium in 1931 and was later able to concentrate it in water.

[5] Urey's mentor Gilbert Newton Lewis isolated the first sample of pure heavy water by electrolysis in 1933. [6] George de Hevesy and Hoffer used heavy water in 1934 in one of the first biological tracer experiments, to estimate the rate of turnover of water in the human body. The history of large-quantity production and use of heavy water in early nuclear experiments is given below. [7] Effect on biological systems Edit Heavy isotopes of chemical elements have slightly different chemical behaviors, but for most elements the differences in chemical behavior between isotopes are far too small to use, or even detect. For hydrogen, however, this is not true. The larger chemical isotope-effects seen with deuterium and tritium manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass of the nucleus and electrons appears. This quantity is altered in heavy-hydrogen compounds (of which deuterium oxide is the most common and familiar) more than for heavy-isotope substitution in other chemical elements. This isotope effect of heavy hydrogen is magnified further in biological systems, which are very sensitive to small changes in the solvent properties of water.

Heavy water is the only known chemical substance that affects the period of circadian oscillations , consistently increasing the length of each cycle. The effect is seen in unicellular organisms, green plants, isopods, insects, birds, mice, and hamsters. The mechanism is unknown. [8] To perform their tasks, enzymes rely on their finely tuned networks of hydrogen bonds , both in the active center with their substrates, and outside the active center, to stabilize their tertiary structures . As a hydrogen bond with deuterium is slightly stronger [9] than one involving ordinary hydrogen, in a highly deuterated environment, some normal reactions in cells are disrupted. Particularly hard-hit by heavy water are the delicate assemblies of mitotic spindle formation necessary for cell division in eukaryotes . Plants stop growing and seeds do not germinate when given only heavy water, because heavy water stops eukaryotic cell division. It has been proposed that low doses of heavy water can slow the aging process by helping the body resist oxidative damage via the isotope effect .

[10] A team at the Institute for the Biology of Ageing, located in Moscow, conducted an experiment to determine the effect of heavy water on longevity using fruit flies and found that while large amounts were deadly, smaller quantities increased lifespans by up to 30%. [11] Effect on animals Edit Experiments in mice, rats, and dogs [12] have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy water (90%) rapidly kill fish , tadpoles , flatworms , and Drosophila . Mammals, such as rats , given heavy water to drink die after a week, at a time when their body water approaches about 50% deuteration. The mode of death appears to be the same as that in cytotoxic poisoning (such as chemotherapy ) or in acute radiation syndrome (though deuterium is not radioactive), and is due to deuterium's action in generally inhibiting cell division. It is more toxic to malignant cells than normal cells but the concentrations needed are too high for regular use.

[12] As in chemotherapy, deuterium-poisoned mammals die of a failure of bone marrow (bleeding and infection) and intestinal-barrier functions ( diarrhea and fluid loss). Notwithstanding the problems of plants and animals in living with too much deuterium, prokaryotic organisms such as bacteria, which do not have the mitotic problems induced by deuterium, may be grown and propagated in fully deuterated conditions, resulting in replacement of all hydrogen atoms in the bacterial proteins and DNA with the deuterium isotope. [12] Full replacement with heavy atom isotopes can be accomplished in higher organisms with other non-radioactive heavy isotopes (such as carbon-13, nitrogen-15, and oxygen-18), but this cannot be done for the stable heavy isotope of hydrogen. Deuterium oxide is used to enhance boron neutron capture therapy , but this effect does not rely on the biological effects of deuterium per se, but instead on deuterium's ability to moderate (slow) neutrons without capturing them.

[12] Toxicity in humans Edit Because it would take a very large amount of heavy water to replace 25% to 50% of a human being's body water (which in turn is 70% of body weight) with heavy water, accidental or intentional poisoning with heavy water is unlikely to the point of practical disregard. For a poisoning, large amounts of heavy water would need to be ingested without significant normal water intake for many days to produce any noticeable toxic effects. Oral doses of heavy water in the range of several grams, as well as heavy oxygen 18O, are routinely used in human metabolic experiments. See doubly-labeled water testing. Since one in about every 6400 hydrogen atoms is deuterium, a 50 kg human containing 32 kg of body water would normally contain enough deuterium (about 1.1 gram) to make 5.5 grams of pure heavy water, so roughly this dose is required to double the amount of deuterium in the body. The American patent U.S. Patent 5,223,269 is for the use of heavy water to treat hypertension (high blood pressure).

A loss of blood pressure may partially explain the reported incidence of dizziness upon ingestion of heavy water. Heavy water radiation contamination confusion Edit Although many people associate heavy water primarily with its use in nuclear reactors, pure heavy water is not particularly radioactive. Pure heavy water is slightly radioactive from minute traces of contaminating natural tritium present in it, but the same is true of ordinary water as well. Heavy water which has been used as a coolant in nuclear power plants contains substantially more tritium due to neutron bombardment of the deuterium in the heavy water ( Tritium is a health risk when ingested in large quantities). In 1990, a disgruntled employee at the Point Lepreau Nuclear Generating Station in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat transport loop of the nuclear reactor , and loaded it into the employee water cooler . Eight employees drank some of the contaminated water. The incident was discovered when employees began leaving bioassay urine samples with elevated tritium levels. The quantity of heavy water involved was far below levels that could induce heavy water toxicity, but several employees received elevated radiation doses from tritium and neutron-activated chemicals in the water.

[13] This was not an incident of heavy water poisoning, but rather radiation poisoning from other isotopes in the heavy water. Some news services were not careful to distinguish these points, and some of the public were left with the impression that heavy water is normally radioactive and more severely toxic than it is. Even if pure heavy water had been used in the water cooler indefinitely, it is not likely the incident would have been detected or caused harm, since no employees would be expected to get as much as 25% of their daily drinking water from such a source. [14] Production Edit On Earth , semiheavy water, HDO, occurs naturally in regular water at a proportion of about 1 molecule in 3200. This means that 1 in 6400 hydrogen atoms is deuterium, which is 1 part in 3200 by weight (hydrogen weight). The HDO may be separated from regular water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect .

(For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water .) The difference in mass between the two hydrogen isotopes translates into a difference in the zero-point energy and thus into a slight difference in the speed at which the reaction proceeds. Once HDO becomes a significant fraction of the water, heavy water will become more prevalent as water molecules trade hydrogen atoms very frequently. To produce pure heavy water by distillation or electrolysis requires a large cascade of stills or electrolysis chambers, and consumes large amounts of power, so the chemical methods are generally preferred. The most important chemical method is the Girdler sulfide process . An alternative process [15] , patented by Graham M. Keyser, uses lasers to selectively dissociate deuterated hydrofluorocarbons to form deuterium fluoride , which can then be separated by physical means. Although the energy consumption for this process is much less than for the Girdler sulfide process, this method is currently uneconomical due to the expense of procuring the necessary hydrofluorocarbons. United States Edit In 1953, the United States began using heavy water in plutonium production reactors at the Savannah River Site .

The first of the five heavy water reactors came online in 1953, and the last was placed in cold shutdown in 1996. The SRS reactors were heavy water reactors so that they could produce both plutonium and tritium for the US nuclear weapons program. The U.S. developed the Girdler sulfide chemical exchange production process which was first demonstrated on a large scale at the Dana, Indiana plant in 1945 and at the Savannah River Plant, South Carolina in 1952. The SRP was operated by DuPont for the USDOE until 1 April 1989 at which time the operation was taken over by Westinghouse . Norway Main article: Norwegian heavy water sabotage In 1934, Norsk Hydro built the first commercial heavy water plant at Vemork , Tinn , with a capacity of 12 tonnes per year [16] . From 1940 and throughout World War II , the plant was under German control and the allies decided to destroy the plant and its heavy water to inhibit German development of nuclear weapons. In late 1942, a planned raid by British airborne troops failed, both gliders crashing.

The raiders were killed in the crash or subsequently executed by the Germans. In the night of 27 February 1943 Operation Gunnerside succeeded. Norwegian commandos and local resistance managed to demolish small but key parts of the electrolytic cells, dumping the accumulated heavy water down the factory drains. Had the German nuclear program followed similar lines of research as the U.S. Manhattan Project , such heavy water would have been crucial to obtaining plutonium from a nuclear reactor. The Norsk Hydro operation is one of the great commando sabotage operations of the war. On 16 November 1943, the allied air forces dropped more than 400 bombs on the site. The allied air raid prompted the Nazi government to move all available heavy water to Germany for safekeeping. On 20 February 1944, a Norwegian partisan sank the ferry M/F Hydro carrying the heavy water across Lake Tinn , at the cost of 14 Norwegian civilians' lives, and most of the heavy water was presumably lost. A few of the barrels were only half full, and therefore could float, and may have been salvaged and transported to Germany.

(These events were dramatized in the 1965 movie, The Heroes of Telemark , and also in a level of the Playstation 2 game, Secret Weapons Over Normandy.) Recent investigation of production records at Norsk Hydro and analysis of an intact barrel that was salvaged in 2004 revealed that although the barrels in this shipment contained water of pH 14 — indicative of the alkaline electrolytic refinement process — they did not contain high concentrations of D2O. [17] Despite the apparent size of shipment, the total quantity of pure heavy water was quite small, most barrels only containing between 1/2–1% pure heavy water. The Germans would have needed a total of about 5 tons of heavy water to get a nuclear reactor running. The manifest clearly indicated that there was only half a ton of heavy water being transported to Germany. The Hydro was carrying far too little heavy water for even one reactor, let alone the 10 or more tons needed to make enough plutonium for a nuclear weapon.

[17] Canada Edit As part of its contribution to the Manhattan Project , Canada built and operated a 6 tonnes per year electrolytic heavy water plant at Trail, BC , which started operation in 1943. The Atomic Energy of Canada Limited (AECL) design of power reactor requires large quantities of heavy water to act as a neutron moderator and coolant. AECL ordered two heavy water plants which were built and operated in Atlantic Canada at Glace Bay (by Deuterium of Canada Limited) and Port Hawkesbury , Nova Scotia (by General Electric Canada). These plants proved to have significant design, construction and production problems and so AECL built the Bruce Heavy Water Plant ( map location ), which it later sold to Ontario Hydro , to ensure a reliable supply of heavy water for future power plants. The two Nova Scotia plants were shut down in 1985 when their production proved to be unnecessary. The Bruce Heavy Water Plant in Ontario was the world's largest heavy water production plant with a capacity of 700 tonnes per year. It used the Girdler sulfide process to produce heavy water, and required 340,000 tonnes of feed water to produce one tonne of heavy water.

It was part of a complex that included 8 CANDU reactors which provided heat and power for the heavy water plant. The site was located at Douglas Point in Bruce County on Lake Huron where it had access to the waters of the Great Lakes . The Bruce plant was commissioned in 1979 to provide heavy water for a large increase in Ontario's nuclear power generation. The plants proved to be significantly more efficient than planned and only three of the planned four units were eventually commissioned. In addition, the nuclear power programme was slowed down and effectively stopped due to a perceived oversupply of electricity, later shown to be temporary, in 1993. Improved efficiency in the use and recycling of heavy water plus the over-production at Bruce left Canada with enough heavy water for its anticipated future needs. Also, the Girdler process involves large amounts of hydrogen sulfide , raising environmental concerns if there should be a release. The Bruce heavy water plant was shut down in 1997, after which the plant was gradually dismantled and the site cleared. Atomic Energy of Canada Limited (AECL) is currently researching other more efficient and environmentally benign processes for creating heavy water.

This is essential for the future of the CANDU reactors since heavy water represents about 20% of the capital cost of each reactor. India India is the world's second largest producer of heavy water through its Heavy Water Board . Iran Edit On 26 August 2006, Iranian President Ahmadinejad inaugurated an expansion of the country's heavy-water plant near Arak . Iran has indicated that the heavy-water production facility will operate in tandem with a 40 MW research reactor that has a scheduled completion date in 2009. [18] Pakistan Edit The 50 MWt, heavy water and natural uranium research reactor at Khushab, in Punjab province, is a central element of Pakistan's program for production of plutonium, deuterium and tritium for advanced compact warheads. Pakistan succeeded in illicitly acquiring a tritium purification and storage plant, and deuterium and tritium precursor materials from two German firms. [19] Other countries Edit Argentina is another declared producer of heavy water, using an ammonia/hydrogen exchange based plant supplied by Switzerland's Sulzer company.

Romania also produces heavy water at the Drobeta Girdler Sulfide plant and is exporting it from time to time. France operated a small plant during the 1950s and 1960s. Applications Edit Deuterium oxide is used in nuclear magnetic resonance spectroscopy when the solvent of interest is water and the nuclide of interest is hydrogen. This is because the signal from the water solvent would interfere with the signal from the molecule of interest. Deuterium has a different magnetic moment from hydrogen and therefore does not contribute to the NMR signal at the hydrogen resonance frequency. Organic Chemistry Edit Deuterium oxide is often used as the source of deuterium for preparing specifically-labelled isotopologs of organic compounds. For example, C-H bonds adjacent to ketonic carbonyl groups can be replaced by C-D bonds, using acid or base catalysis. Trimethylsulfoxonium iodide, made from dimethylsulfoxide and methyl iodide can be recrystallized from deuterium oxide, and then dissociated to regenerate methyl iodide and dimethylsulfoxide, both deuterium labelled.

In cases where specific double labelling by deuterium and tritium is contemplated, the researcher needs to be aware that deuterium oxide, depending upon age and origin, can contain some tritium. Fourier transform spectroscopy Edit Deuterium oxide is often used instead of water when collecting FTIR spectra of proteins in solution. H2O creates a strong band that overlaps with the amide I region of proteins. The band from D2O is shifted away from the amide I region. Neutron moderator Edit Heavy water is used in certain types of nuclear reactors where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238 which captures neutrons without fissioning. The CANDU reactor uses this design. Light water also acts as a moderator but because light water absorbs more neutrons than heavy water, reactors using light water must use low enriched uranium rather than natural uranium, otherwise criticality is impossible. Because they do not require uranium enrichment , heavy water reactors are of concern in regards to nuclear proliferation .

The breeding and extraction of plutonium can be a relatively rapid and cheap route to building a nuclear weapon , as chemical separation of plutonium from fuel is easier than isotopic separation of U-235 from natural uranium. Among current and past nuclear weapons states , Israel, India, and North Korea first used plutonium from heavy water moderated reactors burning natural uranium , while China, South Africa and Pakistan first built weapons using highly enriched uranium . However, in the U.S., the first experimental atomic reactor (1942), as well as the Manhattan Project Hanford production reactors which produced the plutonium for the Trinity test and Fat Man bombs, all used pure carbon neutron moderators and functioned with neither enriched uranium nor heavy water. Russian and British plutonium production also used graphite-moderated reactors. There is no evidence that civilian heavy water power reactors, such as the CANDU or Atucha designs, have been used for military production of fissile materials. In states which do not already possess nuclear weapons, the nuclear material at these facilities is under IAEA safeguards to discourage any such diversion. Due to its potential for use in nuclear weapons programs, the possession or import/export of large industrial quantities of heavy water are subject to government control in several countries.

Suppliers of heavy water and heavy water production technology typically apply IAEA (International Atomic Energy Agency) administered safeguards and material accounting to heavy water. (In Australia, the Nuclear Non-Proliferation (Safeguards) Act 1987.) In the U.S. and Canada, non-industrial quantities of heavy water (i.e., in the gram to kg range) are routinely available without special license through chemical supply dealers and commercial companies such as the world's former major producer Ontario Hydro . Current (2006) cost of a kilogram of 99.98% reactor-purity heavy water, is about $600 to $700. Smaller quantities of reasonable purity (99.9%) may be purchased from chemical supply houses at prices of roughly $1 per gram. [20] Neutrino detector Edit The Sudbury Neutrino Observatory (SNO) in Sudbury , Ontario used 1000 tonnes of heavy water on loan from Atomic Energy of Canada Limited . The neutrino detector is 6800 feet underground in a deep mine, in order to shield it from muons produced by cosmic rays .

SNO was built to answer the question of whether or not electron-type neutrinos produced by fusion in the Sun (the only type the Sun should be producing directly, according to theory) might be able to turn into other types of neutrinos on the way to Earth. SNO detects the Čerenkov radiation in the water from high-energy electrons produced from electron-type neutrinos as they undergo reactions with neutrons in deuterium , turning them into protons and electrons (only the electrons move fast enough to be detected in this manner). SNO also detects the same radiation from neutrino↔electron scattering events, which again produces high energy electrons. These two reactions are produced only by electron-type neutrinos. The use of deuterium is critical to the SNO function, because all three "flavours" (types) of neutrinos [21] may be detected in a third type of reaction, neutrino-disintegration, in which a neutrino of any type (electron, muon, or tau) scatters from a deuterium nucleus ( deuteron ), transferring enough energy to break up the loosely-bound deuteron into a free neutron and proton .

This event is detected when the free neutron is absorbed by 35Cl− present from NaCl which has been deliberately dissolved in the heavy water, causing emission of characteristic capture gamma rays. Thus, in this experiment, heavy water not only provides the transparent medium necessary to produce and visualize Čerenkov radiation, but it also provides deuterium to detect exotic mu type (μ) and tau (τ) neutrinos, as well as a non-absorbent moderator medium to preserve free neutrons from this reaction, until they can be absorbed by an easily-detected neutron-activated isotope. Metabolic rate testing in physiology/biology Heavy water is employed as part of a mixture with H218O for a common and safe test of mean metabolic rate in humans and animals undergoing their normal activities. This metabolic test is usually called the doubly-labeled water test . Tritium production See also: Tritium#Deuterium Tritium is an important material in nuclear weapon design for boosted fission weapons and initiators, and also has civilian industrial applications. Some is created in heavy water moderated reactors when deuterium captures a neutron.

This reaction has a small cross-section and produces only small amounts of tritium, although enough so that cleaning tritium from the moderator may be desirable after several years to reduce the risk of tritium escape and radiation exposure. Production of large amounts of tritium in this way would require reactors with very high neutron fluxes, or with a very high proportion of heavy water to nuclear fuel and very low neutron absorption by other reactor material. The tritium would then have to be recovered by isotope separation from a much larger quantity of deuterium, unlike tritium production from lithium-6 (the present method of tritium production), where only chemical separation is needed. Deuterium's absorption cross section for thermal neutrons is .52 milli barns , while oxygen-16 's is .19 millibarns and oxygen-17 's is .24 barn. 17O makes up .038% of natural oxygen , which has an overall absorption cross section of .28 millibarns.

Therefore in D2O with natural oxygen, 21% of neutron captures are on oxygen, a proportion that may rise further as 17O accumulates from neutron capture on 16O. Also, 17O emits an alpha particle on capture, producing radioactive carbon-14 . See also

Question: What is a more familiar name for deuterium oxide ?
Answer: HEAVY WATER