Heavy water

Heavy water

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Encyclopedia
Heavy water is water highly enriched in the hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 isotope
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...

 deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

; e.g., heavy water used in CANDU reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...

s is 99.75% enriched by hydrogen atom-fraction (in ordinary water, the deuterium-to-hydrogen ratio is about 156 deuterium atoms per million hydrogen atoms). The term "heavy water" today is somewhat colloquial, and pure heavy water for research and commercial use is generally commerically offered, and referred to, as deuterium oxide. It is not radioactive. It is about 11% denser than water, but otherwise, is physically and chemically similar. However, the difference (especially the biological properties) is larger than in most other isotope-substituted compounds
Isotopologue
Isotopologues are molecules that differ only in their isotopic composition. Simply, the isotopologue of a chemical species has at least one atom with a different number of neutrons than the parent....

 because deuterium is unique among heavy stable isotope
Stable isotope
Stable isotopes are chemical isotopes that may or may not be radioactive, but if radioactive, have half-lives too long to be measured.Only 90 nuclides from the first 40 elements are energetically stable to any kind of decay save proton decay, in theory...

s in being twice as heavy as the lightest isotope. This difference increases the strength
Bond energy
In chemistry, bond energy is the measure of bond strength in a chemical bond. It is the heat required to break one Mole of molecules into their individual atoms. For example, the carbon-hydrogen bond energy in methane E is the enthalpy change involved with breaking up one molecule of methane into...

 of water's hydrogen-oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

 bond, and this in turn is enough to cause differences that are important to some biochemical reactions.

The human body naturally contains deuterium equivalent to five grams of heavy water, which is thought to be harmless. Similar doses are used as non-radioactive tracer
Tracer
Tracer may refer to:* Histochemical tracer, a substance used for tracing purposes in histochemistry, the study of the composition of cells and tissues...

s in human and animal metabolic experiments. However, in animal studies when heavy water replaces ~25% to 50% of the body's water, it interferes with cellular mitotic apparatus and prevents cell division. 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 poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ing with heavy water is unlikely to the point of practical disregard.

Heavy water was first produced in 1932, a few months after the discovery of deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

. With the discovery of nuclear fission
Nuclear fission
In nuclear physics and nuclear chemistry, nuclear fission is a nuclear reaction in which the nucleus of an atom splits into smaller parts , often producing free neutrons and photons , and releasing a tremendous amount of energy...

 in late 1938, and the need for a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 that captured few neutrons, heavy water became an important component of early nuclear energy
Nuclear power
Nuclear power is the use of sustained nuclear fission to generate heat and electricity. Nuclear power plants provide about 6% of the world's energy and 13–14% of the world's electricity, with the U.S., France, and Japan together accounting for about 50% of nuclear generated electricity...

 programs during World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

 (1939–1945). Partly because of Nazi Germany
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

's overreliance on heavy water, it didn't produce a functioning reactor for the duration of the war. Since then, heavy water is an essential component in some types of reactor, either for power or for nuclear-weapons isotopes, such as plutonium-239
Plutonium-239
Plutonium-239 is an isotope of plutonium. Plutonium-239 is the primary fissile isotope used for the production of nuclear weapons, although uranium-235 has also been used and is currently the secondary isotope. Plutonium-239 is also one of the three main isotopes demonstrated usable as fuel in...

. These heavy water reactor
Heavy water reactor
A pressurised heavy water reactor is a nuclear power reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water as its coolant and moderator. The heavy water coolant is kept under pressure in order to raise its boiling point, allowing it to be heated to higher...

s have the advantage of being able to run on natural uranium without the use of hazardous graphite moderators. Most modern reactors use enriched uranium
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...

 and normal "light water" (H2O) moderator.

Semiheavy water


Semiheavy water, HDO, exists whenever there is water with light hydrogen (protium
Hydrogen atom
A hydrogen atom is an atom of the chemical element hydrogen. The electrically neutral atom contains a single positively-charged proton and a single negatively-charged electron bound to the nucleus by the Coulomb force...

, 1H) and deuterium (D or 2H) in the mix. 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
Dynamic equilibrium
A dynamic equilibrium exists once a reversible reaction ceases to change its ratio of reactants/products, but substances move between the chemicals at an equal rate, meaning there is no net change. It is a particular example of a system in a steady state...

.
In regular water, about 1 molecule in 3,200 is HDO (one hydrogen in 6,400 is D). By comparison, heavy water D2O occurs at a proportion of about 1 molecule in 41 million (i.e., one in 6,4002). This makes semiheavy water far more common than "normal" heavy water.

Heavy-oxygen water


Water enriched in the heavier oxygen isotopes 17O and 18O is also commercially available, e.g. for use as a non-radioactive isotopic tracer. It qualifies as 'heavy water' in being denser than normal water (H218O is as dense as D2O, H217O is halfway between H2O and D2O), but is rarely called heavy water, since it doesn't contain the deuterium which gives D2O its unusual nuclear and biological properties. It is more expensive than D2O due to the more difficult separation of 17O and 18O.

Physical properties (with comparison to light water)

Property D2O (Heavy water) H2O (Light water)
Freezing point
Freezing Point
Freezing Point is a news journal in the People's Republic of China which has been the subject of controversy over its criticism of Communist Party officials and the sympathetic ear it lent to a Chinese historian who had criticized official history textbooks...

 (°C)
3.82 0.0
Boiling point
Boiling point
The boiling point of an element or a substance is the temperature at which the vapor pressure of the liquid equals the environmental pressure surrounding the liquid....

 (°C)
101.4 100.0
Density
Density
The mass density or density of a material is defined as its mass per unit volume. The symbol most often used for density is ρ . In some cases , density is also defined as its weight per unit volume; although, this quantity is more properly called specific weight...

 at STP
Standard conditions for temperature and pressure
Standard condition for temperature and pressure are standard sets of conditions for experimental measurements established to allow comparisons to be made between different sets of data...

 (g/mL)
1.1056 0.9982
Temp. of maximum density (°C) 11.6 4.0
Dynamic viscosity (at 20°C, mPa·s
Second
The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

)
1.25 1.005
Surface tension
Surface tension
Surface tension is a property of the surface of a liquid that allows it to resist an external force. It is revealed, for example, in floating of some objects on the surface of water, even though they are denser than water, and in the ability of some insects to run on the water surface...

 (at 25°C, μJ
Microjoule
Microjoule is a team that builds ultra-efficient vehicles. It is composed of students and advisors at Lycée La Joliverie in St Sébastien sur Loire, France. The team has broken the world record for most efficient gasoline-powered vehicle three times:...

)
7.193 7.197
Heat of fusion (cal
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

/mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...

)
1,515 1,436
Heat of vaporisation (cal
Calorie
The calorie is a pre-SI metric unit of energy. It was first defined by Nicolas Clément in 1824 as a unit of heat, entering French and English dictionaries between 1841 and 1867. In most fields its use is archaic, having been replaced by the SI unit of energy, the joule...

/mol
Mole (unit)
The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...

)
10,864 10,515
pH
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 (at 25°C)
7.41 (sometimes "pD") 7.00
Refractive index
Refractive index
In optics the refractive index or index of refraction of a substance or medium is a measure of the speed of light in that medium. It is expressed as a ratio of the speed of light in vacuum relative to that in the considered medium....

 (at 20°C, 0.5893 μm
Micrometre
A micrometer , is by definition 1×10-6 of a meter .In plain English, it means one-millionth of a meter . Its unit symbol in the International System of Units is μm...

)
1.32844 1.33335

Physical properties obvious by inspection: Heavy water is 10.6% denser than ordinary water, a difference which is not immediately obvious. 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 (it will sink). If the water is ice-cold the higher melting temperature of heavy ice can also be observed – it melts at 3.8 °C, and thus holds up very well in ice-cold normal water.

An early experiment reported not the "slightest difference" in taste between ordinary and heavy water; on the other hand, rats given a choice between distilled normal water and heavy water were able to avoid the heavy water based on smell, and it may be possible that it has a different taste)

No physical properties are listed for "pure" semi-heavy water, because it is unstable 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. Semi-heavy water can be created by a chemical method but would rapidly transform into a dynamic mixture of 25% light water, 25% heavy water, and 50% semi-heavy water (however if it were made in the gas phase and directly frozen to a solid, this semiheavy ice would be stable).

History


Harold Urey
Harold Urey
Harold Clayton Urey was an American physical chemist whose pioneering work on isotopes earned him the Nobel Prize in Chemistry in 1934...

 discovered the isotope deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

 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
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 in 1933. George de Hevesy
George de Hevesy
George Charles de Hevesy, Georg Karl von Hevesy, was a Hungarian radiochemist and Nobel laureate, recognized in 1943 for his key role in the development of radioactive tracers to study chemical processes such as in the metabolism of animals.- Early years :Hevesy György was born in Budapest,...

 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.
Emilian Bratu
Emilian Bratu
Emilian Bratu was a Romanian chemical engineer, founder of chemical engineering education in Romania. With the Austrian physical chemist Otto Redlich he studied the dissociation constant of heavy water.-Life and work:...

 and Otto Redlich
Otto Redlich
Otto Redlich was an Austrian physical chemist and chemical engineer who is best known for his development of equations of state like Redlich-Kwong equation. Besides this he had numerous other contributions to science....

 studied the autodissociation of heavy water in 1934.

Effect on biological systems


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
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

 manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass
Reduced mass
Reduced mass is the "effective" inertial mass appearing in the two-body problem of Newtonian mechanics. This is a quantity with the unit of mass, which allows the two-body problem to be solved as if it were a one-body problem. Note however that the mass determining the gravitational force is not...

 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
Circadian rhythm
A circadian rhythm, popularly referred to as body clock, is an endogenously driven , roughly 24-hour cycle in biochemical, physiological, or behavioural processes. Circadian rhythms have been widely observed in plants, animals, fungi and cyanobacteria...

, 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.

To perform their tasks, enzyme
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...

s rely on their finely tuned networks of hydrogen bond
Hydrogen bond
A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine, that comes from another molecule or chemical group. The hydrogen must be covalently bonded to another electronegative atom to create the bond...

s, both in the active center with their substrates, and outside the active center, to stabilize their tertiary structure
Tertiary structure
In biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...

s. 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
Mitotic spindle
In cell biology, the spindle fibers are the structure that separates the chromosomes into the daughter cells during cell division. It is part of the cytoskeleton in eukaryotic cells...

 formation necessary for cell division
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...

 in eukaryote
Eukaryote
A eukaryote is an organism whose cells contain complex structures enclosed within membranes. Eukaryotes may more formally be referred to as the taxon Eukarya or Eukaryota. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear...

s. 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
Isotope effect
Isotope effect can refer to:* Kinetic isotope effect* Magnetic isotope effect* Superconductive transition temperature varying by isotope atomic weight; See BCS theory#Successes of the BCS theory...

. 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%.

Effect on animals


Experiments in mice, rats, and dogs have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gamete
Gamete
A gamete is a cell that fuses with another cell during fertilization in organisms that reproduce sexually...

s nor zygote
Zygote
A zygote , or zygocyte, is the initial cell formed when two gamete cells are joined by means of sexual reproduction. In multicellular organisms, it is the earliest developmental stage of the embryo...

s can develop. High concentrations of heavy water (90%) rapidly kill fish
Fish
Fish are a paraphyletic group of organisms that consist of all gill-bearing aquatic vertebrate animals that lack limbs with digits. Included in this definition are the living hagfish, lampreys, and cartilaginous and bony fish, as well as various extinct related groups...

, tadpole
Tadpole
A tadpole or polliwog is the wholly aquatic larval stage in the life cycle of an amphibian, particularly that of a frog or toad.- Appellation :...

s, flatworm
Flatworm
The flatworms, known in scientific literature as Platyhelminthes or Plathelminthes are a phylum of relatively simple bilaterian, unsegmented, soft-bodied invertebrate animals...

s, and Drosophila
Drosophila
Drosophila is a genus of small flies, belonging to the family Drosophilidae, whose members are often called "fruit flies" or more appropriately pomace flies, vinegar flies, or wine flies, a reference to the characteristic of many species to linger around overripe or rotting fruit...

. Mammals, such as rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

s, 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
Cytotoxicity
Cytotoxicity is the quality of being toxic to cells. Examples of toxic agents are a chemical substance, an immune cell or some types of venom .-Cell physiology:...

 (such as chemotherapy
Chemotherapy
Chemotherapy is the treatment of cancer with an antineoplastic drug or with a combination of such drugs into a standardized treatment regimen....

) 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. As in chemotherapy, deuterium-poisoned mammals die of a failure of bone marrow (bleeding and infection) and intestinal-barrier functions (diarrhea
Diarrhea
Diarrhea , also spelled diarrhoea, is the condition of having three or more loose or liquid bowel movements per day. It is a common cause of death in developing countries and the second most common cause of infant deaths worldwide. The loss of fluids through diarrhea can cause dehydration and...

 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. 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
Boron Neutron Capture Therapy
Boron neutron capture therapy is an experimental form of radiotherapy that uses a neutron beam that interacts with boron injected into a patient...

, 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.

Toxicity in humans


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 poison
Poison
In the context of biology, poisons are substances that can cause disturbances to organisms, usually by chemical reaction or other activity on the molecular scale, when a sufficient quantity is absorbed by an organism....

ing 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 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. However, it is more likely that this symptom can be attributed to altered vestibular function.

Heavy water radiation contamination confusion


Although many people associate heavy water primarily with its use in nuclear reactors, pure heavy water is not radioactive. Commercial-grade heavy water is slightly radioactive due to the presence of minute traces of natural tritium, but the same is true of ordinary water. Heavy water that has been used as a coolant in nuclear power plants contains substantially more tritium as a result of 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
Point Lepreau Nuclear Generating Station
Point Lepreau Nuclear Generating Station is a Canadian nuclear power station located 2 km northeast of Point Lepreau, New Brunswick. The facility was constructed between 1975-1983 by NB Power, the provincially-owned public utility....

 in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat transport loop of the nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...

, and loaded it into the employee water cooler
Water cooler
A water cooler or water dispenser is a device that cools and dispenses water. They are generally broken up in two categories: bottleless and bottled water coolers...

. Eight employees drank some of the contaminated water. The incident was discovered when employees began leaving bioassay
Bioassay
Bioassay , or biological standardization is a type of scientific experiment. Bioassays are typically conducted to measure the effects of a substance on a living organism and are essential in the development of new drugs and in monitoring environmental pollutants...

 urine samples with elevated tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

 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. 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 employee would be expected to get much more than 25% of their daily drinking water from such a source.

Production


On Earth
Earth
Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

, deuterated 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
Distillation
Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

 or electrolysis
Electrolysis
In chemistry and manufacturing, electrolysis is a method of using a direct electric current to drive an otherwise non-spontaneous chemical reaction...

 and also by various chemical exchange processes, all of which exploit a kinetic isotope effect
Kinetic isotope effect
The kinetic isotope effect is the ratio of reaction rates of two different isotopically labeled molecules in a chemical reaction. It is also called "isotope fractionation," although this term is somewhat broader in meaning...

. (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
Zero-point energy
Zero-point energy is the lowest possible energy that a quantum mechanical physical system may have; it is the energy of its ground state. All quantum mechanical systems undergo fluctuations even in their ground state and have an associated zero-point energy, a consequence of their wave-like nature...

 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. Production of 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
Girdler sulfide process
The Girdler sulfide process, also known as the Geib–Spevack process, is an industrial production method for making heavy water , an important component of many nuclear reactors because it acts as a neutron moderator. It takes its name from Karl-Hermann Geib and Jerome S...

.

An alternative process, patented by Graham M. Keyser, uses lasers to selectively dissociate deuterated hydrofluorocarbons to form deuterium fluoride
Fluoride
Fluoride is the anion F−, the reduced form of fluorine when as an ion and when bonded to another element. Both organofluorine compounds and inorganic fluorine containing compounds are called fluorides. Fluoride, like other halides, is a monovalent ion . Its compounds often have properties that are...

, 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.

As noted, modern commercial heavy water is almost universally referred to, and sold as, deuterium oxide. It is most often sold in various grades of purity, from 98% enrichment to 99.75% - 99.98% deuterium enrichement (nuclear reactor grade) and occasionally even higher isotopic purity.

USSR/Russia


Production was first started in 1934 in Dnepropetrovsk, but was interrupted during Operation Barbarossa
Operation Barbarossa
Operation Barbarossa was the code name for Germany's invasion of the Soviet Union during World War II that began on 22 June 1941. Over 4.5 million troops of the Axis powers invaded the USSR along a front., the largest invasion in the history of warfare...

. After 1946 five plants with summary annual production of 20 tons were constructed.

United States


In 1953, the United States began using heavy water in plutonium
Plutonium
Plutonium is a transuranic radioactive chemical element with the chemical symbol Pu and atomic number 94. It is an actinide metal of silvery-gray appearance that tarnishes when exposed to air, forming a dull coating when oxidized. The element normally exhibits six allotropes and four oxidation...

 production reactors at the Savannah River Site
Savannah River Site
The Savannah River Site is a nuclear reservation in the United States in the state of South Carolina, located on land in Aiken, Allendale and Barnwell Counties adjacent to the Savannah River, southeast of Augusta, Georgia. The site was built during the 1950s to refine nuclear materials for...

. 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
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

 for the US nuclear weapons program.

The U.S. developed the Girdler sulfide
Girdler sulfide process
The Girdler sulfide process, also known as the Geib–Spevack process, is an industrial production method for making heavy water , an important component of many nuclear reactors because it acts as a neutron moderator. It takes its name from Karl-Hermann Geib and Jerome S...

 chemical exchange production process which was first demonstrated on a large scale at the Dana, Indiana
Dana, Indiana
Dana is a town in Helt Township, Vermillion County, Indiana, United States. The population was 608 at the 2010 census. It is primarily a farming community.Famed World War II war correspondent Ernie Pyle was born on a tenant farm near Dana...

 plant in 1945 and at the Savannah River Plant, South Carolina in 1952. The SRP was operated by DuPont
DuPont
E. I. du Pont de Nemours and Company , commonly referred to as DuPont, is an American chemical company that was founded in July 1802 as a gunpowder mill by Eleuthère Irénée du Pont. DuPont was the world's third largest chemical company based on market capitalization and ninth based on revenue in 2009...

 for the USDOE until 1 April 1989 at which time the operation was taken over by Westinghouse
Westinghouse Electric Company
Westinghouse Electric Company LLC is a nuclear power company, offering a wide range of nuclear products and services to utilities throughout the world, including nuclear fuel, service and maintenance, instrumentation and control and advanced nuclear plant designs...

.

India


India is the world's largest producer of heavy water through its Heavy Water Board
Heavy Water Board
Heavy Water Board , a constituent unit under Department of Atomic Energy in the Government of India is primarily responsible for production of Heavy Water which is used as a 'moderator' and 'Coolant' in nuclear power as well as research reactors....

 and also exports to countries like Republic of Korea and the United States.
Development of heavy water process in India happened in three phases:
The first phase (late1950s to mid 1980s) was a period of technology development, the second phase was of deployment of technology and process stabilisation (mid 1980s to early 1990s) and third phase saw consolidation and a shift towards improvement in production and energy conservation.

Norway


In 1934, Norsk Hydro
Norsk Hydro
Norsk Hydro ASA is a Norwegian aluminium and renewable energy company, headquartered in Oslo. Hydro is the fourth largest integrated aluminium company worldwide. It has operations in some 40 countries around the world and is active on all continents. The Norwegian state holds a 43.8 percent...

 built the first commercial heavy water plant at Vemork
Vemork
Vemork is the name of a hydroelectric power plant outside Rjukan in Tinn, Norway. The plant was built by Norsk Hydro and opened in 1911, its main purpose being to fix nitrogen for the production of fertilizer. Vemork was later the site of the first plant in the world to mass-produce heavy water...

, Tinn
Tinn
Tinn is a municipality in Telemark county, Norway. It is part of the traditional region of Øst-Telemark. The administrative centre of the municipality is the town of Rjukan....

, with a capacity of 12 tonnes per year. From 1940 and throughout World War II
World War II
World War II, or the Second World War , was a global conflict lasting from 1939 to 1945, involving most of the world's nations—including all of the great powers—eventually forming two opposing military alliances: the Allies and the Axis...

, the plant was under German
Nazi Germany
Nazi Germany , also known as the Third Reich , but officially called German Reich from 1933 to 1943 and Greater German Reich from 26 June 1943 onward, is the name commonly used to refer to the state of Germany from 1933 to 1945, when it was a totalitarian dictatorship ruled by...

 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
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

, 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
SF Hydro
SF Hydro was a Norwegian steam powered railway ferry that operated on Tinnsjø in Telemark. The ferry operated between Mæl and Tinnoset between 1914 and 1944, connecting the two railways Rjukanbanen and Tinnosbanen. The railway was used to transport raw materials and fertilizer from Norsk Hydro's...

 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
The Heroes of Telemark
The Heroes of Telemark is a 1965 war film directed by Anthony Mann based on the true story of the Norwegian heavy water sabotage during World War II...

, and also in a level of the PlayStation 2/Xbox game, Secret Weapons Over Normandy
Secret Weapons Over Normandy
Secret Weapons Over Normandy or is a World War II-based arcade flight simulation video game released on November 18, 2003. Published by LucasArts and developed by Totally Games, the game is composed of 15 objective-based missions set in 1940s European, North African, and the Pacific theatres of war...

.)

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
PH
In chemistry, pH is a measure of the acidity or basicity of an aqueous solution. Pure water is said to be neutral, with a pH close to 7.0 at . Solutions with a pH less than 7 are said to be acidic and solutions with a pH greater than 7 are basic or alkaline...

 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, most barrels only containing 0.5–1% 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.

Canada


As part of its contribution to the Manhattan Project
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

, Canada built and operated a 6 tonnes per year electrolytic heavy water plant at Trail, BC
Trail, British Columbia
Trail is a city in the West Kootenay region of the Interior of British Columbia, Canada.-Geography:Trail has an area of . The city is located on both banks of the Columbia River, approximately 10 km north of the United States border. This section of the Columbia River valley is located between the...

, 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
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 and coolant. AECL ordered two heavy water plants which were built and operated in Atlantic Canada
Atlantic Canada
Atlantic Canada is the region of Canada comprising the four provinces located on the Atlantic coast, excluding Quebec: the three Maritime provinces – New Brunswick, Prince Edward Island, and Nova Scotia – and Newfoundland and Labrador...

 at Glace Bay
Glace Bay, Nova Scotia
Glace Bay is a community in the eastern part of the Cape Breton Regional Municipality in Nova Scotia, Canada. It forms part of the general area referred to as Industrial Cape Breton....

 (by Deuterium of Canada Limited) and Port Hawkesbury
Port Hawkesbury, Nova Scotia
-Historical residents:*Henry Nicholas Paint , member of Parliament for Richmond county, merchant and land owner. His family received land grants at Belle Vue on the Strait of Canso in 1817 and at Point Tupper in 1863, and did much to develop the local communities in the area.*Arthur John Langley ...

, Nova Scotia
Nova Scotia
Nova Scotia is one of Canada's three Maritime provinces and is the most populous province in Atlantic Canada. The name of the province is Latin for "New Scotland," but "Nova Scotia" is the recognized, English-language name of the province. The provincial capital is Halifax. Nova Scotia is the...

 (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
Ontario Hydro
Ontario Hydro was the official name from 1974 of the Hydro-Electric Power Commission of Ontario which was established in 1906 by the provincial Power Commission Act to build transmission lines to supply municipal utilities with electricity generated by private companies already operating at Niagara...

, 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
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 was the world's largest heavy water production plant with a capacity of 700 tonnes per year. It used the Girdler sulfide process
Girdler sulfide process
The Girdler sulfide process, also known as the Geib–Spevack process, is an industrial production method for making heavy water , an important component of many nuclear reactors because it acts as a neutron moderator. It takes its name from Karl-Hermann Geib and Jerome S...

 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 reactor
CANDU reactor
The CANDU reactor is a Canadian-invented, pressurized heavy water reactor. The acronym refers to its deuterium-oxide moderator and its use of uranium fuel...

s which provided heat and power for the heavy water plant. The site was located at Douglas Point
Douglas Point
The Douglas Point Nuclear Generating Station was Canada’s first full-scale nuclear power plant and the second CANDU Pressurised Heavy Water Reactor....

 near Tiverton, Ontario on Lake Huron
Lake Huron
Lake Huron is one of the five Great Lakes of North America. Hydrologically, it comprises the larger portion of Lake Michigan-Huron. It is bounded on the east by the Canadian province of Ontario and on the west by the state of Michigan in the United States...

 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
Girdler sulfide process
The Girdler sulfide process, also known as the Geib–Spevack process, is an industrial production method for making heavy water , an important component of many nuclear reactors because it acts as a neutron moderator. It takes its name from Karl-Hermann Geib and Jerome S...

 involves large amounts of hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...

, 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
Atomic Energy of Canada Limited
Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...

 (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.

Iran


On 26 August 2006, Iranian President Ahmadinejad inaugurated an expansion of the country's heavy-water plant near Arak
Arak, Iran
-Industries:thumb|right|250px|wagon parsArak is one of the main industrial cities of Iran, possessing many plants for heavy industries especially for the metal and machinery industries, including:...

. Iran has indicated that the heavy-water production facility will operate in tandem with a 40 MW research reactor that had a scheduled completion date in 2009.

Pakistan


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 (i.e. thermonuclear weapons). Pakistan succeeded in illicitly acquiring a tritium purification and storage plant, and deuterium and tritium precursor materials from two German firms.

Other countries


Argentina
Argentina
Argentina , officially the Argentine Republic , is the second largest country in South America by land area, after Brazil. It is constituted as a federation of 23 provinces and an autonomous city, Buenos Aires...

 is another declared producer of heavy water, using an ammonia/hydrogen exchange based plant supplied by Switzerland's Sulzer company.

Romania
Romania
Romania is a country located at the crossroads of Central and Southeastern Europe, on the Lower Danube, within and outside the Carpathian arch, bordering on the Black Sea...

 also produces heavy water at the Drobeta Girdler Sulfide plant and exports it from time to time.

France operated a small plant during the 1950s and 1960s.

Nuclear magnetic resonance


Deuterium oxide is used in nuclear magnetic resonance spectroscopy when the solvent of interest is water and the nuclide
Nuclide
A nuclide is an atomic species characterized by the specific constitution of its nucleus, i.e., by its number of protons Z, its number of neutrons N, and its nuclear energy state....

 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
Magnetic moment
The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it...

 from hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 and therefore does not contribute to the NMR signal at the hydrogen resonance frequency.

Organic chemistry


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
Trimethylsulfoxonium iodide
Trimethylsulfoxonium iodide is a sulfoxonium salt. It is used to generate dimethyloxosulfonium methylide by reaction with sodium hydride. The latter compound is used as a methylene-transfer reagent, and is used to prepare epoxides....

, made from dimethyl sulfoxide
Dimethyl sulfoxide
Dimethyl sulfoxide is an organosulfur compound with the formula 2SO. This colorless liquid is an important polar aprotic solvent that dissolves both polar and nonpolar compounds and is miscible in a wide range of organic solvents as well as water...

 and methyl iodide can be recrystallized from deuterium oxide, and then dissociated to regenerate methyl iodide and dimethyl sulfoxide, 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


Deuterium oxide is often used instead of water when collecting FTIR
Fourier transform spectroscopy
Fourier transform spectroscopy is a measurement technique whereby spectra are collected based on measurements of the coherence of a radiative source, using time-domain or space-domain measurements of the electromagnetic radiation or other type of radiation....

 spectra of proteins in solution. H2O creates a strong band that overlaps with the amide
Amide
In chemistry, an amide is an organic compound that contains the functional group consisting of a carbonyl group linked to a nitrogen atom . The term refers both to a class of compounds and a functional group within those compounds. The term amide also refers to deprotonated form of ammonia or an...

 I region of proteins. The band from D2O is shifted away from the amide I region.

Neutron moderator


Heavy water is used in certain types of nuclear reactors where it acts as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....

 to slow down neutrons so that they are more likely to react with the fissile
Fissile
In nuclear engineering, a fissile material is one that is capable of sustaining a chain reaction of nuclear fission. By definition, fissile materials can sustain a chain reaction with neutrons of any energy. The predominant neutron energy may be typified by either slow neutrons or fast neutrons...

 uranium-235
Uranium-235
- References :* .* DOE Fundamentals handbook: Nuclear Physics and Reactor theory , .* A piece of U-235 the size of a grain of rice can produce energy equal to that contained in three tons of coal or fourteen barrels of oil. -External links:* * * one of the earliest articles on U-235 for the...

 than with uranium-238
Uranium-238
Uranium-238 is the most common isotope of uranium found in nature. It is not fissile, but is a fertile material: it can capture a slow neutron and after two beta decays become fissile plutonium-239...

 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 for a reactor moderator must use enriched uranium
Enriched uranium
Enriched uranium is a kind of uranium in which the percent composition of uranium-235 has been increased through the process of isotope separation. Natural uranium is 99.284% 238U isotope, with 235U only constituting about 0.711% of its weight...

 rather than natural uranium, otherwise criticality
Critical mass
A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The...

 is impossible. A significant fraction of outdated power reactors, such as the RBMK
RBMK
RBMK is an initialism for the Russian reaktor bolshoy moshchnosti kanalniy which means "High Power Channel-type Reactor", and describes a class of graphite-moderated nuclear power reactor which was built in the Soviet Union. The RBMK reactor was the type involved in the Chernobyl disaster...

 reactors in the USSR, were constructed using normal water for cooling but graphite as a moderator. However, the danger of graphite in power reactors (graphite fires in part led to the Chernobyl disaster
Chernobyl disaster
The Chernobyl disaster was a nuclear accident that occurred on 26 April 1986 at the Chernobyl Nuclear Power Plant in Ukraine , which was under the direct jurisdiction of the central authorities in Moscow...

) has led to the dicontinuation of graphite in standard reactor designs

Because they do not require uranium enrichment, heavy water reactor
Heavy water reactor
A pressurised heavy water reactor is a nuclear power reactor, commonly using unenriched natural uranium as its fuel, that uses heavy water as its coolant and moderator. The heavy water coolant is kept under pressure in order to raise its boiling point, allowing it to be heated to higher...

s are of concern in regards to nuclear proliferation
Nuclear proliferation
Nuclear proliferation is a term now used to describe the spread of nuclear weapons, fissile material, and weapons-applicable nuclear technology and information, to nations which are not recognized as "Nuclear Weapon States" by the Treaty on the Nonproliferation of Nuclear Weapons, also known as the...

. The breeding and extraction of plutonium can be a relatively rapid and cheap route to building a nuclear weapon
Nuclear weapon
A nuclear weapon is an explosive device that derives its destructive force from nuclear reactions, either fission or a combination of fission and fusion. Both reactions release vast quantities of energy from relatively small amounts of matter. The first fission bomb test released the same amount...

, 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
Natural uranium
Natural uranium refers to refined uranium with the same isotopic ratio as found in nature. It contains 0.7 % uranium-235, 99.3 % uranium-238, and a trace of uranium-234 by weight. In terms of the amount of radioactivity, approximately 2.2 % comes from uranium-235, 48.6 % uranium-238, and 49.2 %...

, 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
Manhattan Project
The Manhattan Project was a research and development program, led by the United States with participation from the United Kingdom and Canada, that produced the first atomic bomb during World War II. From 1942 to 1946, the project was under the direction of Major General Leslie Groves of the US Army...

 Hanford production reactors which produced the plutonium for the Trinity test
Trinity test
Trinity was the code name of the first test of a nuclear weapon. This test was conducted by the United States Army on July 16, 1945, in the Jornada del Muerto desert about 35 miles southeast of Socorro, New Mexico, at the new White Sands Proving Ground, which incorporated the Alamogordo Bombing...

 and Fat Man
Fat Man
"Fat Man" is the codename for the atomic bomb that was detonated over Nagasaki, Japan, by the United States on August 9, 1945. It was the second of the only two nuclear weapons to be used in warfare to date , and its detonation caused the third man-made nuclear explosion. The name also refers more...

 bombs, all used pure carbon (graphite) neutron moderators combined with normal water cooling pipes, 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
Atucha I nuclear power plant
Atucha I is one of two operational nuclear power plants of Argentina. It is located in the town of Lima, Zárate, Buenos Aires, about from Buenos Aires, on the right-hand shore of the Paraná de las Palmas River....

 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
Ontario Hydro
Ontario Hydro was the official name from 1974 of the Hydro-Electric Power Commission of Ontario which was established in 1906 by the provincial Power Commission Act to build transmission lines to supply municipal utilities with electricity generated by private companies already operating at Niagara...

. 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
Sudbury Neutrino Observatory
The Sudbury Neutrino Observatory is a neutrino observatory located 6,800 feet underground in Vale Inco's Creighton Mine in Sudbury, Ontario, Canada. The detector was designed to detect solar neutrinos through their interactions with a large tank of heavy water. The detector turned on in May 1999,...

 (SNO) in Sudbury, Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....

 used 1000 tonnes of heavy water on loan from Atomic Energy of Canada Limited
Atomic Energy of Canada Limited
Atomic Energy of Canada Limited or AECL is a Canadian federal Crown corporation and Canada's largest nuclear science and technology laboratory...

. The neutrino detector
Neutrino detector
A neutrino detector is a physics apparatus designed to study neutrinos. Because neutrinos are only weakly interacting with other particles of matter, neutrino detectors must be very large in order to detect a significant number of neutrinos. Neutrino detectors are often built underground to isolate...

 is 6800 feet (2,072.6 m) 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 neutrino
Neutrino
A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with a half-integer spin, chirality and a disputed but small non-zero mass. It is able to pass through ordinary matter almost unaffected...

s produced by fusion in the Sun
Sun
The Sun is the star at the center of the Solar System. It is almost perfectly spherical and consists of hot plasma interwoven with magnetic fields...

 (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 Cherenkov radiation
Cherenkov radiation
Cherenkov radiation is electromagnetic radiation emitted when a charged particle passes through a dielectric medium at a speed greater than the phase velocity of light in that medium...

 in the water from high-energy electrons produced from electron-type neutrino
Neutrino
A neutrino is an electrically neutral, weakly interacting elementary subatomic particle with a half-integer spin, chirality and a disputed but small non-zero mass. It is able to pass through ordinary matter almost unaffected...

s as they undergo reactions with neutron
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

s in deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...

, 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 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
Neutron
The neutron is a subatomic hadron particle which has the symbol or , no net electric charge and a mass slightly larger than that of a proton. With the exception of hydrogen, nuclei of atoms consist of protons and neutrons, which are therefore collectively referred to as nucleons. The number of...

 and proton
Proton
The proton is a subatomic particle with the symbol or and a positive electric charge of 1 elementary charge. One or more protons are present in the nucleus of each atom, along with neutrons. The number of protons in each atom is its atomic number....

. 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 Cherenkov 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



Tritium
Tritium
Tritium is a radioactive isotope of hydrogen. The nucleus of tritium contains one proton and two neutrons, whereas the nucleus of protium contains one proton and no neutrons...

 is the active substance in self-powered lighting and controlled nuclear fusion, its other uses including autoradiography and radioactive labeling. It is also used in nuclear weapon design
Nuclear weapon design
Nuclear weapon designs are physical, chemical, and engineering arrangements that cause the physics package of a nuclear weapon to detonate. There are three basic design types...

 for boosted fission weapon
Boosted fission weapon
A boosted fission weapon usually refers to a type of nuclear bomb that uses a small amount of fusion fuel to increase the rate, and thus yield, of a fission reaction. The neutrons released by the fusion reactions add to the neutrons released in the fission, as well as inducing the fission reactions...

s and initiators. Some is created in heavy water moderated reactors when deuterium captures a neutron. This reaction has a small cross-section
Neutron cross-section
In nuclear and particle physics, the concept of a neutron cross section is used to express the likelihood of interaction between an incident neutron and a target nucleus. In conjunction with the neutron flux, it enables the calculation of the reaction rate, for example to derive the thermal power...

 (the imaginary neutron-capturing area around the nucleus) and produces only small amounts of tritium, although enough to justify cleaning tritium from the moderator every few years to reduce the environmental risk of tritium escape.

Producing a lot of tritium in this way would need reactors with very high neutron fluxes, or with a very high proportion of heavy water to nuclear fuel
Nuclear fuel
Nuclear fuel is a material that can be 'consumed' by fission or fusion to derive nuclear energy. Nuclear fuels are the most dense sources of energy available...

 and very low neutron absorption by other reactor material. The tritium would then have to be recovered by isotope separation
Isotope separation
Isotope separation is the process of concentrating specific isotopes of a chemical element by removing other isotopes, for example separating natural uranium into enriched uranium and depleted uranium. This is a crucial process in the manufacture of uranium fuel for nuclear power stations, and is...

 from a much larger quantity of deuterium, unlike production from lithium-6 (the present method), where only chemical separation is needed.

Deuterium's absorption cross section for thermal neutrons is 0.52 millibarn
Barn (unit)
A barn is a unit of area. Originally used in nuclear physics for expressing the cross sectional area of nuclei and nuclear reactions, today it is used in all fields of high energy physics to express the cross sections of any scattering process, and is best understood as a measure of the...

s (barn=10−28 m2, milli=1/1000), while oxygen-16's is 0.19 millibarns and oxygen-17
Oxygen-17
Oxygen-17 is a low abundant isotope of oxygen . Being the only stable isotope of oxygen possessing a nuclear spin and the unique characteristic of field-independent relaxation it enables NMR studies of metabolic pathways of compounds incorporating oxygen at high magnetic fields Oxygen-17 is a low...

's is 0.24 barns. 17O makes up 0.038% of natural oxygen
Oxygen
Oxygen is the element with atomic number 8 and represented by the symbol O. Its name derives from the Greek roots ὀξύς and -γενής , because at the time of naming, it was mistakenly thought that all acids required oxygen in their composition...

, making the overall cross section 0.28 millibarns. Therefore in D2O with natural oxygen, 21% of neutron capture
Neutron capture
Neutron capture is a kind of nuclear reaction in which an atomic nucleus collides with one or more neutrons and they merge to form a heavier nucleus. Since neutrons have no electric charge they can enter a nucleus more easily than positively charged protons, which are repelled...

s are on oxygen, rising higher as 17O builds up from neutron capture on 16O. Also, 17O emits an alpha particle
Alpha particle
Alpha particles consist of two protons and two neutrons bound together into a particle identical to a helium nucleus, which is classically produced in the process of alpha decay, but may be produced also in other ways and given the same name...

 on capture, producing radioactive carbon-14
Carbon-14
Carbon-14, 14C, or radiocarbon, is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues , to date archaeological, geological, and hydrogeological...

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See also


  • Norwegian heavy water sabotage
    Norwegian heavy water sabotage
    The Norwegian heavy water sabotage was a series of actions undertaken by Norwegian saboteurs during World War II to prevent the German nuclear energy project from acquiring heavy water , which could be used to produce nuclear weapons...

  • Cold fusion
    Cold fusion
    Cold fusion, also called low-energy nuclear reaction , refers to the hypothesis that nuclear fusion might explain the results of a group of experiments conducted at ordinary temperatures . Both the experimental results and the hypothesis are disputed...

  • Vienna Standard Mean Ocean Water
  • Deuterium
    Deuterium
    Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...


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