Heavy water ( deuterium oxide , 2
H
2 O , D
2 ) is a water form containing an amount greater than the normal amount of the deuterium hydrogen isotope ( 2 H or D, also known as heavy hydrogen ), rather than common isotope hydrogen-1 ( 1 H or H, also called protium) that make up most of the hydrogen in normal water. The presence of deuterium provides different nuclear chemical properties, and increased mass gives different physical and chemical properties compared to normal "water light".
Video Heavy water
Description
Deuterium is an isotope of hydrogen with a nucleus containing neutrons and protons; the nucleus of the protium atom (normal hydrogen) consists only of protons. An additional neutron makes deuterium atoms about twice as heavy as a protium atom.
A heavy water molecule has two deuterium atoms in place of two protium atoms from ordinary "light" water. Heavy water molecules, however, are not much different from normal water molecules, because about 89% of the water molecule's weight comes from a single oxygen atom rather than two hydrogen atoms. The term daily heavy water refers to a very rich water mixture containing most of deuterium oxide D
2 O , but also some hydrogen-deuterium oxide (HDO) and a small amount of ordinary hydrogen oxide H
2 O molecule. For example, the heavy water used in the CANDU reactor is 99.75% enriched by the fraction of the hydrogen atom - which means that 99.75% of the hydrogen atom is the type of weight. By comparison, ordinary water ("plain water" used for deuterium standards) contains only about 156 deuterium atoms per million hydrogen atoms, which means that 0.0156% of hydrogen atoms are of gravity.
Heavy water is not radioactive. In its pure form, it has a density of about 11% greater than water, but is physically and chemically similar. However, differences in deuterium-containing water (especially those affecting biological properties) are greater than those of other commonly occurring isotopes because deuterium is unique among heavy weight isotopes that are twice as heavy as the lightest isotope. This difference increases the strength of water-hydrogen-oxygen bonds, and this in turn is enough to cause the differences that are important for some biochemical reactions. The human body naturally contains deuterium equivalent to about five grams of heavy water, which is harmless. When most water (& gt; 50%) in higher organisms is replaced by heavy water, the result is cell dysfunction and death.
Heavy water was first produced in 1932, a few months after the discovery of deuterium. With the discovery of nuclear fission at the end of 1938, and the need for neutron moderators who captured several neutrons, heavy water became an early nuclear energy research component. Since then, heavy water has become an important component in several types of reactors, both electrical and designed to produce isotopes for nuclear weapons. These heavy water reactors have the advantage of being able to run on natural uranium without using graphite moderators that pose a radiological and dust explosion hazard in the decommissioning phase. Most modern reactors use uranium enriched with plain water as a moderator.
Maps Heavy water
Other heavy water forms
Water of semiheavy
Semiheavy water , HDO, there is whenever there is water with mild hydrogen (protium, 1 H ) and deuterium (D or 2 H ) in the mix. This is because the hydrogen atoms (hydrogen-1 and deuterium) are quickly exchanged between water molecules. Water containing 50% H and 50% D in hydrogen actually contains about 50% HDO and 25% respectively H
2 O and D
2 O , in dynamic equilibrium. In normal water, about 1 molecule in 3200 is HDO (one hydrogen in 6,400 in D form), and a heavy water molecule ( D
2 O ) occurs only in the proportion of about 1 molecule in 41 million (ie one in 6,400 2 ). So semiheavy water molecules are much more common than "pure" (homoisotopic) heavy water molecules.
Heavy oxygen water
Water enriched in heavier isotopes of oxygen 17 /span> and 18
O is also commercially available, for example, to be used as a non-radioactive isotope tracker. This is "heavy water" because it is denser than ordinary water ( H
2 18
O about as densely D
2 O , H
2 17
O approximately halfway between H
2 O and D
2 O ) - but rarely called heavy water, because it contains no deuterium that gives D 2 O nuclear properties and biologically unusual This is more expensive than D 2 O because of the more difficult separation of 17 O and 18 O. H 2 18 O is also used for the production of fluorine-18 for radiopharmaceuticals and radiotracers and for positron emission tomography. Water attenuated
Tritium-containing water contains tritium ( 3 H) instead of protium ( 1 H) or deuterium ( 2 H), and therefore radioactive.
Physical properties
The physical properties of water and heavy water differ in several respects. Heavy water is less dissociated than light water at a certain temperature, and the actual concentration of D ion less than H ion will be to sample light water at that temperature same. The same goes for OD - vs. OH - ion. For heavy water Kw D 2 O (25.0 Â ° C) = 1,35 ÃÆ'â € "10 -15 , and [D ] must be the same [OD - ] for neutral water. So pKw D 2 O = p [OD - ] p ​​[D ] = 7.44 7.44 = 14.87 (25, 0 Â ° C), and p [D ] of neutral heavy water at 25.0 Â ° C is 7.44.
The heavy water PD is generally measured using a pH electrode that gives a pH value (real), or pHa, and at various pD temperatures real acid can be estimated from pH meter directly measured pHa, such as pD = pHa (clear read from pH meter) 0.41. Electrode correction for alkaline condition is 0.456 for heavy water. Correction of alkali then pD = PHa (clear readings of pH meters) 0.456. This correction is slightly different from p [D] and p [OD-] from 0.44 from the corresponding in heavy water.
Heavy water is 10.6% denser than ordinary water, and different physical properties can be physically seen without equipment if the frozen sample falls into normal water, as it will sink. If ice water is cold, higher melting ice temperatures can also be observed: melting at 3.7 ° C, and thus not melting in plain cold water.
Early experiments reported not a "slight difference" in the taste between plain water and heavy water. However, the mice given the choice between normal distilled water and heavy water can avoid heavy water based on odors, and it may have different flavors.
No physical property is listed for "semi-pure" pure water, as it is unstable as bulk liquids. In a liquid state, some water molecules are always in ionized state, which means that the hydrogen atom can exchange between different oxygen atoms. Semi-heavy water can, in theory, be made through chemical methods, but will quickly transform into a dynamic mix of 25% light water, 25% heavy water, and 50% semi-heavy water. However, if it is made in gas phase and directly stored in, semi heavy solid water in the form of ice can be stable. This is due to a collision between water vapor molecules that is almost completely ignored in the gas phase at standard temperatures, and once a collision crystallizes between molecules ceases altogether due to solid solid grid lattice structures.
History
Harold Urey discovered the deuterium isotope in 1931 and could then concentrate in water. Urey's adviser Gilbert Newton Lewis isolated the first sample of pure heavy water by electrolysis in 1933. George de Hevesy and Erich Hofer used heavy water in 1934 in one of the first biological tracer experiments, to estimate the rate of water spin in the human body. The history of large quantities of production and the use of heavy water in initial nuclear experiments is given below. Emilian Bratu and Otto Redlich studied the autodissociation of heavy water in 1934.
Effects on biological systems
The different isotopes of the chemical elements have slightly different chemical behavior, but for most elements the difference is too small to use, or even detectable. For hydrogen, however, this is not true. A larger chemical isotope effect is seen between protium (light hydrogen) versus deuterium and tritium as the bonding energy in chemistry is determined in quantum mechanics by the equation in which the reduced mass quantity of the nucleus and electrons appears. This quantity is altered in heavy hydrogen compounds (where deuterium oxide is the most common) rather than heavy isotope substitution in other chemical elements. The effect of this heavy hydrogen isotope is enlarged further in biological systems, which are highly sensitive to small changes in the properties of water solvents.
Heavy water is the only known chemical that affects the period of circadian oscillation, 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 its tasks, enzymes rely on their established hydrogen bonding network, both at the active center with its substrate, and outside the active center, to stabilize their tertiary structures. Since hydrogen bonds with deuterium are slightly stronger than ordinary hydrogen bonds, in a highly deuterized environment, some of the normal reactions in the cells are disrupted.
Being struck by heavy water is an elaborate assembly of spindle mitotic formation necessary for cell division in eukaryotes. Plants stop growing and seeds do not sprout when given only heavy water, because heavy water stops eukaryotic cell division. The deuterium cell is larger and is a modification of the direction of division. Cell membranes also change, and react first to the impact of heavy water. In 1972 it was shown that increasing the percentage of deuterium content in water reduces plant growth. Research conducted on the growth of prokaryotic microorganisms under conditions of severe hydrogen environments suggests that in these environments, all hydrogen atoms of water can be replaced with deuterium. Experiments show that bacteria can live in 98% of heavy water. However, all concentrations of more than 50% deuterium in water molecules are found to kill plants.
Effects on animals
Experiments on rats, mice and dogs have shown that 25% degrees of deuterated (sometimes unchangeable) sterility, because gametes and zygotes can not develop. High concentrations of heavy water (90%) quickly kill fish, tadpoles, flatworms, and Drosophila . Mammals (for example, rats) are given heavy water to drink to death after a week, when their body water approaches about 50% deuteration. The mode of death appears to be the same as that of cytotoxic poisoning (such as chemotherapy) or in acute radiation syndrome (although deuterium is not radioactive), and because deuterium action generally inhibits cell division. It is more toxic to malignant cells than normal cells but the required concentration is too high for regular use. As in chemotherapy, deuterium-toxic mammals die from bone marrow failure (bleeding and infection) and intestinal obstruction (diarrhea and fluid loss).
Despite the problems of plants and animals in life with too much deuterium, prokaryotic organisms such as bacteria, which have no deuterium-induced mitotic problems, can grow and multiply in fully deuterized conditions, resulting in the replacement of all hydrogen atoms in bacterial and DNA proteins by deuterium isotopes.
Full replacement of heavy atomic isotopes can be performed on higher organisms with other non-radioactive heavy isotopes (such as carbon-13, nitrogen-15, and oxygen-18), but this can not be done for stable isotopes of hydrogen.
Deuterium oxide is used to enhance thoracic neutron retention therapy, but this effect does not depend on the biological effects of deuterium per se, but on the deuterium ability to moderate (slowly) neutrons without capturing them.
Human toxicity
Because it will require very much water to replace 25% to 50% of human body water (water which in turn 50-75% of body weight) with heavy water, intentional or intentional with heavy water is not possible. to the point of ignoring the practical. Poisoning will require the victim to swallow large amounts of heavy water with no significant normal water intake for several days to produce a real toxic effect.
The oral dose of heavy water in the range of several grams, as well as the oxygen weight 18 O, is routinely used in human metabolic experiments. See double-labeled water testing. Since one of every 6,400 hydrogen atoms is deuterium, 50 kg of humans containing 32 kg of body water usually contain enough deuterium (about 1.1 g) to make 5.5 g of pure heavy water, so roughly this dose is needed to double the amount deuterium in the body.
The loss of blood pressure can partially explain the reported incidence of dizziness when swallowing heavy water. However, it is more likely that these symptoms may be associated with altered vestibular function.
Radiation contamination confusion weighs
Although many people associate heavy water especially with its use in nuclear reactors, pure heavy water is not radioactive. Commercial grade heavy water is a bit radioactive because of the small traces of natural tritium, but the same applies to ordinary water. Heavy water that has been used as a coolant in a nuclear power plant contains more tritium as a result of heavy deuterium neutron bombing in heavy water (tritium is a health risk when ingested in large quantities).
In 1990, a disgruntled employee at the Lepreau Nuclear Generating Station in Canada obtained a sample (estimated to be about "half a cup") of heavy water from the primary nuclear reactor heat transport loop, and loaded it into a cafeteria drink dispenser. Eight employees drink contaminated water. The incident was discovered when employees began to leave a sample of urine bioassay with high tritium levels. The amount of heavy water involved is well below levels that can cause severe water toxicity, but some employees receive high doses of radiation from tritium and chemicals that are activated neutrons in the water. This is not an incident of heavy water intoxication, but rather radiation poisoning from other isotopes in heavy water. Some news services are not careful to distinguish these points, and some people are left with the impression that heavy water is usually radioactive and more toxic than that. Even if pure heavy water has been used in an unlimited water cooler, it is unlikely that the incident will be detected or cause harm, since no employee is expected to get more than 25% of their daily drinking water from the source..
Production
On Earth, deuterised water, HDO, occurs naturally in normal water with a proportion of about 1 molecule in 3,200. This means that 1 of the 6,400 hydrogen atoms is deuterium, which is 1 part in 3,200 weight (weight of hydrogen). HDO can be separated from normal water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit the effects of kinetic isotopes. (For more information on the distribution of deuterium isotopes in water, see Vienna Standard Mean Ocean Water.) In theory, deuterium for heavy water can be made in nuclear reactors, but the separation from ordinary water is the cheapest mass production process.
The mass difference between the two isotopes of hydrogen translates into a difference in zero-point energy and thus becomes slightly different in reaction speed. Once HDO becomes a significant fraction of water, heavy water becomes more prevalent when water molecules trade hydrogen atoms very often. Production of pure heavy water by distillation or electrolysis requires a large cascade or electrolysis space and consumes a large amount of power, so a chemical method is generally preferred.
The most cost-effective process for producing heavy water is a double-exchange sulfide exchange process (known as the Girdler sulfide process) developed in parallel by Karl-Hermann Geib and Jerome S. Spevack in 1943.
The alternative process, patented by Graham M. Keyser, uses lasers to separate deuterated hydrofluorocarbons to form deuterium fluoride, which can then be separated physically. Although energy consumption for this process is much less than that of the Girdler sulphide process, this method is currently not economical because of the required hydrofluorocarbon procurement cost.
As noted, modern commercial heavy water is almost universally called, and sold as, deuterium oxide . It is most often sold in varying degrees of purity, from 98% enrichment to 99.75-99.98% deuterium enrichment (nuclear reactor level) and sometimes higher isotope purity. Argentina
Argentina is a major producer of heavy water, using an ammonia/hydrogen exchange factory supplied by Swiss Sulzer company. It is also a major exporter to Canada, USA, Germany, and other countries. The heavy water production facility located in Arroyito, Neuquà © n province is the largest heavy water production facility in the world. Argentina produces 200 tonnes of heavy water per year using instead of the bithermal S 2 method, but the isotope monotermals . USSR
In October 1939, Soviet physicists Yakov Borisovich Zel'dovich and Yulii Borisovich Khariton concluded that heavy water and carbon were the only viable moderators for natural uranium reactors, and in August 1940, together with Georgy Flyorov, submitted a plan to the Russian Academy of Science calculated that 15 tons of heavy water was required for the reactor. With the Soviet Union having no uranium mines at the time, young Academy workers were sent to Leningrad photography shops to buy uranium nitrate, but the entire heavy water project was suspended in 1941 when German forces invaded during Operation Barbarossa.
In 1943, Soviet scientists have discovered that all the scientific literature related to heavy water has disappeared from the West, which by Flyorov in a letter warns Soviet leader Joseph Stalin about, and at that time there were only 2-3 kg of heavy water across the country. In late 1943, the Soviet purchasing commission in the US earned 1 kg of heavy water and 100 kg more in February 1945, and by the end of World War II, the NKVD took over the project.
In October 1946, as part of Alsos Russia, NKVD was deported to the Soviet Union of Germany, German scientists who had worked on heavy water production during the war, including Karl-Hermann Geib, inventor of the Girdler sulphide process. These German scientists worked under the supervision of the German physical chemist Max Volmer at the Institute of Physical Chemistry in Moscow with the factory they built produced huge amounts of water in 1948.
United States
During the Manhattan Project, the United States built three heavy water production plants as part of the P-9 Project at Morgantown Ordnance Works, near Morgantown, West Virginia; at Wabash River Ordnance Works, near Dana and Newport, Indiana; and at Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. The rushing water is also obtained from the Cominco factory on the Trail, British Columbia, Canada. The Chicago Pile-3 experimental reactor used heavy water as a moderator and became critical in 1944. The three domestic production plants closed in 1945 after producing about 20 metric tons of products (about 20,000 liters). The Wabash factory reopened and began the resumption of heavy water production in 1952.
In 1953, the United States began to use heavy water in a plutonium production reactor at the Savannah River Site. The first of five heavy water reactors came online in 1953, and the latter was placed cold in 1996. SRS reactors are heavy water reactors so they can produce plutonium and tritium for US nuclear weapons programs.
The United States developed the production process of Girdler sulphide chemical exchange - first shown in large scale at Dana, the Indiana plant in 1945 and at Savannah River Plant, South Carolina in 1952. DuPont operated the SRP for USDOE until April 1, 1989, when Westinghouse took over.
India
India is one of the largest heavy water producers in the world through Heavy Water Board and also exporting to countries such as Republic of Korea and USA. The development of heavy water processes in India takes place in three phases: The first phase (late 1950s to mid 1980s) is the period of technological development, the second phase is the dissemination of technology and process stabilization (the mid-1980s to the early 1990s) and the phases the third saw the consolidation and shift towards increased production and energy conservation.
Japanese Empire
In the 1930s, it was alleged by the United States and the Soviet Union that Austrian chemist Fritz Johann Hansgirg built a pilot plant for the Japanese Empire in Japan that ruled North Korea to produce heavy water using a new process that he had discovered.
Norwegian
In 1934, Norsk Hydro built the first commercial heavy water plant in Vemork, Tinn, with a capacity of 12 tons per year. From 1940 and during World War II, this plant was under German control and the Allies decided to destroy its heavy factories and water to impede the development of German nuclear weapons. By the end of 1942, the planned raid by British air forces had failed, both gliders crashing. The robbers were killed in the accident or later executed by Germany. On the night of 27 February 1943 Operation Gunnerside succeeded. Norwegian commandos and local resistance succeeded in destroying small portions of electrolytic cells, wasting a great deal of water collected into the ducts of the plant.
On 16 November 1943, Allied air forces dropped more than 400 bombs on the site. Allied air raids prompted the Nazi government to move all available heavy water to Germany for safekeeping. On February 20, 1944, a Norwegian partisan drowned the M/FÃ ferry, Hydro that carried the water across Lake Tinn, at the cost of 14 Norwegian civilians, and most of the heavy water may be lost. Some barrels are only half full, and therefore can float, and may have been saved and transported to Germany.
A recent investigation of production records in Norsk Hydro and an analysis of barrels intact rescued in 2004 revealed that although the barrels in this delivery contained water pH 14 - indicating an alkaline electrolytic refining process - they did not contain high concentrations of D 2 O Although the delivery size is clear, the total quantity of pure heavy water is small enough, most barrels contain only 0.5-1% pure heavy water. Germany will need a total of about 5 tons of heavy water to run a nuclear reactor. The manifest clearly indicates that there is only half a ton of heavy water transported to Germany. Hydro brings too little heavy water to one reactor, let alone the 10 or more tonnes needed to make enough plutonium for nuclear weapons.
Israel admitted to running a Dimona reactor with heavy Norwegian water that was sold there in 1959. Through re-exports using Romania and Germany, India may also use Norway's heavy water.
Canada
As part of its contribution to the Manhattan Project, Canada builds and operates a 6 ton per year heavy electrolytic water mill per year on the Trail, British Columbia, which began operations in 1943.
The Canadian Atomic Energy Design (AECL) of the power plant requires heavy water in large quantities to act as a moderator of neutrons and coolants. AECL has ordered two heavy water plants, built and operated in the Atlantic of Canada in Glace Bay, Nova Scotia (by Deuterium of Canada Limited) and Port Hawkesbury, Nova Scotia (by General Electric Canada). This plant is proven to have significant design, construction and production problems. As a result, AECL built the Bruce Heavy Water Plant ( 44.1854 Â ° N 81.3618 Â ° W / 44.1854; -81.3618 ( Bruce Heavy Water Plant ) ) , which is then sold to Ontario Hydro, to ensure a reliable heavy water supply for future power generation. The two Nova Scotia plants were closed in 1985 when their production proved unnecessary.
Bruce Heavy Water Plant (BHWP) in Ontario is the world's largest heavy-water production plant with a capacity of 1600 tons per year at its peak (800 tons per year per full plant, two fully operational plants at its peak). It uses the Girdler sulfide process to produce heavy water, and requires 340,000 tons of feedwater to produce one ton of heavy water. It is part of a complex that includes eight CANDU reactors, which provide heat and power for heavy water plants. The site is located at Douglas Point/Bruce Nuclear Generating Station near Tiverton, Ontario on Lake Huron where it has access to the waters of the Great Lakes.
AECL issued a construction contract in 1969 for the first BHWP unit (BHWP A). Commissioning BHWP A was conducted by Ontario Hydro from 1971 to 1973, with the factory entering service on 28 June 1973 and the design production capacity reached in April 1974. Due to the success of BHWP A and the large amount of heavy water that would be required for a large number of CANDU nuclear power plant projects which is planned to come, Ontario Hydro commissioned three additional heavy water production sites for Bruce (BHWP B, C, and D). BHWP B began operations in 1979. The first two plants were significantly more efficient than planned, and the number of CANDU construction projects ended significantly lower than planned, leading to construction cancellation at BHWP C & amp; D. In 1984 BHWP A was closed. In 1993 Ontario Hydro has generated enough water to meet all anticipated domestic needs (which is lower than expected due to increased efficiency in the use and recycling of heavy water), so they shut down and destroy half of BHWP B capacity Remaining capacity continues to operate to meet the demand for heavy water exports until it was permanently closed in 1997, after which the plant was gradually dismantled and the site cleaned up.
AECL is currently researching more efficient and eco-friendly processes to create heavy water. This is important for the future of the CANDU reactor because heavy water represents about 15-20% of the total capital cost of each CANDU plant.
Iran
Since 1996 a factory for heavy water production is being built in Khondab near Arak. On August 26, 2006, Iranian President Ahmadinejad inaugurated the expansion of the country's heavy water mill. Iran has indicated that the heavy water production facility will operate in conjunction with a 40 MW research reactor that has a scheduled completion date in 2009.
Iran produced a deuterated solvent in early 2011 for the first time.
The core of the IR-40 should be redesigned under a nuclear agreement in July 2015.
Iran is currently allowed to store only 130 tons of heavy water.
Pakistan
Heavy water research reactors and natural uranium reactors weighing 50 MW th in Khushab, in Punjab province, are a key element of the Pakistan program for the production of plutonium, deuterium and tritium for advanced compact warheads (ie thermonuclear weapons). Pakistan managed to obtain tritium purification and storage plants as well as deuterium and tritium precursors from two German companies.
Other countries
Romania produces heavy water at the Drobeta Girdler sulphide plant for domestic and export purposes.
France operated a small factory during the 1950s and 1960s.
Heavy water exists in high concentrations in the Lake Tanganyika hypolimnion in East Africa. It is likely that the same high concentrations exist in lakes with the same limnology, but these are only 4% enrichment (24 vs. 28) and the water surface is usually enriched in D
2 by evaporation to extend larger faster H
< sub style = "font size: inherit; line-height: inherit; vertical-align: baseline"> 2 O evaporation.
Apps
Nuclear magnetic resonance
Deuterium oxide is used in nuclear magnetic resonance spectroscopy when using water as a solvent if the interesting nuclides are hydrogen. This is because the signal from the water-light solvent molecule ( 1 H 2 O) interferes with the observed signal from the attracted molecule dissolved in it. Deuterium has a different magnetic moment and therefore does not contribute to the <1-source H-NMR signal at the hydrogen-1 resonance frequency.
For some experiments, it may be desirable to identify unstable hydrogens in a compound, ie hydrogen which can easily be converted as H ions at several positions in a molecule. With the addition of D 2 O, sometimes referred to as D 2 O shake , exchange of labile hydrogen and replaced by deuterium ( 2 H) atoms. These positions in the molecule then do not appear in the H-NMR 1 spectrum.
Organic chemistry
Deuterium oxide is often used as a deuterium source to prepare special isotopologic organic compounds. For example, a C-H bond adjacent to a ketonic carbonyl group may be replaced by a C-D bond, using an acid or base catalyst. Trimethylsulfoxonium iodide, made of dimethyl sulfoxide and methyl iodide can be recrystallized from deuterium oxide, and then separated to regenerate methyl iodide and dimethyl sulfoxide, both labeled deuterium. In cases where specific double labeling by deuterium and tritium is contemplated, researchers should be aware that deuterium oxide, depending on age and origin, may contain some tritium.
Fourier Transformation Spectroscopy
Deuterium oxide is often used as a water substitute when collecting the protein FTIR spectrum in solution. H 2 O creates strong bands that overlap with my amide protein region. Bands from D 2 O shift away from the region of amide I.
Neutron Moderator
Heavy water is used in several types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with uranium-235 fissile than uranium-238, which captures neutrons without fissioning. CANDU reactors use this design. Light water also acts as a moderator, but because light water absorbs more neutrons than heavy water, a reactor that uses light water for a reactor moderator should use enriched uranium instead of natural uranium, otherwise criticality is not possible. Significant fractions of outdated reactors, such as the RBMK reactor at the USSR, were built using normal water for cooling but graphite as a moderator. However, the hazards of graphite in power reactors (partial graphite fires causing the Chernobyl disaster) have led to the termination of graphite in the design of standard reactors.
Since they do not require uranium enrichment, heavy water reactors are more of a concern in terms of nuclear proliferation. Plutonium breeding and extraction can be a relatively quick and cheap route to build nuclear weapons, since the chemical separation of plutonium from fuel is easier than the separation of the U-235 isotope from natural uranium. Among present and past nuclear armed states, Israel, India and North Korea first used plutonium from moderate heavy water reactors that burned natural uranium, while China, South Africa and Pakistan first built weapons using highly enriched uranium.
In the US, however, the first experimental atomic reactors (1942), as well as the Hanhattan Manhattan Project's production reactor that produces plutonium for the Trinity test and the Fat Man bomb, all use pure neutron (graphite) graphs combined with ordinary water. refrigeration pipes. They function with enriched uranium or heavy water. Production of Russian and English plutonium also uses a graphite-moderated reactor.
There is no evidence that civilian heavy-water power reactors - such as CANDU or Atucha designs - have been used to produce military fissile material. In countries that do not yet have nuclear weapons, the nuclear material at this facility is under IAEA protection to prevent any diversion.
Because of its potential for use in nuclear weapons programs, the ownership or import/export of large quantities of heavy water industry is subject to government control in some countries. Suppliers of heavy and heavy water production technologies typically apply the IAEA (International Atomic Energy Agency) to regulate the protection and accounting of materials for heavy water. (In Australia, Nuclear Non-Proliferation Act 1987 .) In the US and Canada, the amount of non-industrial heavy water (ie, in the gram to kg range) is routinely available without a special license through the dealer chemical supplies and commercial companies such as former world-leading producer, Ontario Hydro.
Neutrino Detector
The Sudbury Neutrino Observatory (SNO) in Sudbury, Ontario uses 1,000 tons of heavy water with loans from Atomic Energy of Canada Limited. The neutrino detector is 6,800 feet (2,100 m) underground in the mine, to protect from muons produced by cosmic rays. SNO was built to answer the question of whether electron-type neutrinos are produced by fusion at Sun (the only type that should be produced directly by the Sun, according to theory) might be able to transform into other types of neutrinos en route to Earth. SNO detects Cherenkov radiation in water from high-energy electrons generated from electron-type neutrinos as they undergo a charge-current interaction (CC) with neutrons in deuterium, converting them into protons and electrons (but only electrons are fast enough to produce Cherenkov radiation for detection). SNO also detects neutrino <-> electron scattering events (ES), in which neutrinos transfer energy to electrons, which then produce Cherenkov radiation that can be distinguished from those generated by CC events. The first of these two reactions is produced only by electron-type neutrinos, while the latter can be caused by all neutrino flavors. The use of deuterium is essential for the function of SNO, since the three "flavors" (types) of neutrinos can be detected in the third kind of reaction as well, neutrino-disintegration, in which any type of neutrino (electron, muon, or tau) propagates from the deuterium nucleus (deuteron) , transferring enough energy to break down deuterons loosely bound to free neutrons and protons through current neutral interactions (NC). This event is detected when the free neutrons are absorbed by 35 Cl - which is present from the NaCl which is deliberately dissolved in heavy water, causing the emission characteristic to catch gamma rays. Thus, in this experiment, heavy water not only provides the transparent medium necessary to produce and visualize the Cherenkov radiation, but also provides deuterium to detect exotic neutrons of type mu (?) And tau (?), As well as non-absorbent moderators. is to maintain the free neutrons of this reaction, until they can be absorbed by isotopes that are activated with detectable neutrons easily.
Testing metabolic rate in physiology and biology
Heavy water is used as part of the mixture with H 2 18 O for a general and safe average metabolic rate test in humans and animals undergoing their normal activities.
Tritium Production
Tritium is an active substance in self-powered lighting and nuclear fusion controlled, other uses include autoradiography and radioactive labeling. It is also used in the design of nuclear weapons to enhance fission weapons and initiators. Some tritium are made in moderate heavy water reactors when deuterium captures neutrons. This reaction has a small cross section (possibly one neutron capture event) and produces only a small amount of tritium, although it is sufficient to justify tritium cleansing from moderators every few years to reduce environmental risks from tritium escape.
Generating lots of tritium in this way will require reactors with very high neutron flux, or with a very high proportion of heavy water for nuclear fuel and very low neutron absorption by other reactor materials. Tritium must then be recovered by isotope separation from a much larger deuterium amount, unlike the production of lithium-6 (this method), where only chemical separation is required.
The section of the Deuterium absorption section for the thermal neutron is 0.52 millibarns (5.2 ÃÆ'â € "10 -32 m 2 ; 1 granary = 10 -28 m 2 ), while oxygen-16 and oxygen-17 are 0.19 and 0.24 millibarns respectively. 17 O makes up 0.038% natural oxygen, making a whole cross-section of 0.28 millibren. Therefore, in D 2 O with natural oxygen, 21% of the neutron capture is in oxygen, rising higher when 17 O builds from neutron capture at 16 O. Also, 17 O can emit alpha particles in neutron capture, producing radioactive carbon-14.
See also
References
External links
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