Heavy water

Heavy water (deuterium oxide, 2
H
2
O
, D
2
O
) is a form of water that contains a larger than normal amount of the hydrogen isotope deuterium (2
H
or D, also known as heavy hydrogen), rather than the common hydrogen-1 isotope (1
H
or H, also called protium) that makes up most of the hydrogen in normal water.[4] The presence of deuterium gives the water different nuclear properties, and the increase of mass gives it slightly different physical and chemical properties when compared to normal water.

Heavy water
Spacefill model of heavy water
Names
IUPAC name
(2H2)Water[3]
Other names
  • Deuterium oxide[1]
  • Water-d2[2]
  • Dideuterium monoxide
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.029.226
EC Number 232-148-9
97
KEGG
MeSH Deuterium+Oxide
RTECS number ZC0230000
UNII
Properties
D
2
O
Molar mass 20.0276 g mol−1
Appearance Colorless liquid
Odor Odorless
Density 1.107 g mL−1
Melting point 3.82 °C; 38.88 °F; 276.97 K
Boiling point 101.4 °C (214.5 °F; 374.5 K)
Miscible
log P −1.38
1.328
Viscosity 1.25 mPa s (at 20 °C)
1.87 D
Hazards
NFPA 704
Flammability code 0: Will not burn. E.g., waterHealth code 1: Exposure would cause irritation but only minor residual injury. E.g., turpentineReactivity code 0: Normally stable, even under fire exposure conditions, and is not reactive with water. E.g., liquid nitrogenSpecial hazards (white): no codeNFPA 704 four-colored diamond
0
1
0
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).

Explanation

Deuterium is a hydrogen isotope with a nucleus containing a neutron and a proton; the nucleus of a protium (normal hydrogen) atom consists of just a proton. The additional neutron makes a deuterium atom roughly twice as heavy as a protium atom.

A molecule of heavy water has two deuterium atoms in place of the two protium atoms of ordinary "light" water. The weight of a heavy water molecule, however, is not substantially different from that of a normal water molecule, because about 89% of the molecular weight of water comes from the single oxygen atom rather than the two hydrogen atoms. The colloquial term heavy water refers to a highly enriched water mixture that contains mostly deuterium oxide D
2
O
, but also some hydrogen-deuterium oxide (HDO) and a smaller amount of ordinary hydrogen oxide H
2
O
. For instance, the heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction—meaning that 99.75% of the hydrogen atoms are of the heavy type. For comparison, ordinary water (the "ordinary water" used for a deuterium standard) contains only about 156 deuterium atoms per million hydrogen atoms, meaning that 0.0156% of the hydrogen atoms are of the heavy type.

Heavy water is not radioactive. In its pure form, it has a density about 11% greater than water, but is otherwise physically and chemically similar. Nevertheless, the various differences in deuterium-containing water (especially affecting the biological properties) are larger than in any other commonly occurring isotope-substituted compound because deuterium is unique among heavy stable isotopes in being twice as heavy as the lightest isotope. This difference increases the strength of water's hydrogen-oxygen bonds, and this in turn is enough to cause differences that are important to some biochemical reactions. The human body naturally contains deuterium equivalent to about five grams of heavy water, which is harmless. When a large fraction of water (> 50%) in higher organisms is replaced by heavy water, the result is cell dysfunction and death.[5]

Heavy water was first produced in 1932, a few months after the discovery of deuterium.[6] With the discovery of nuclear fission in late 1938, and the need for a neutron moderator that captured few neutrons, heavy water became a component of early nuclear energy research. Since then, heavy water has been an essential component in some types of reactors, both those that generate power and those 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 radiological[7] and dust explosion[8] hazards in the decommissioning phase. Most modern reactors use enriched uranium with ordinary water as the moderator.

Other heavy forms of water

Semiheavy water

Semiheavy water, HDO, exists whenever there is water with light hydrogen (protium, 1
H
) and deuterium (D or 2
H
) 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 H
2
O
and D
2
O
, in dynamic equilibrium. In normal water, about 1 molecule in 3,200 is HDO (one hydrogen in 6,400 is in the form of D), and heavy water molecules (D
2
O
) only occur in a proportion of about 1 molecule in 41 million (i.e. one in 6,4002). Thus semiheavy water molecules are far more common than "pure" (homoisotopic) heavy water molecules.

Heavy-oxygen water

Water enriched in the heavier oxygen isotopes 17
O
and 18
O
is also commercially available, e.g., for use as a non-radioactive isotopic tracer. It is "heavy water" as it is denser than normal water (H
2
18
O
is approximately as dense as D
2
O
, H
2
17
O
is about halfway between H
2
O
and D
2
O
)—but is rarely called heavy water, since it does not contain the deuterium that gives D2O its unusual nuclear and biological properties. It is more expensive than D2O due to the more difficult separation of 17O and 18O.[9] H218O is also used for production of fluorine-18 for radiopharmaceuticals and radiotracers and for positron emission tomography.

Tritiated water

Tritiated water contains tritium (3H) in place of protium (1H) or deuterium (2H), and therefore it is radioactive.

Physical properties

Physical properties of isotopologues of water[10]
Property D2O (Heavy water) HDO (Semiheavy water) H2O (Light water)
Freezing point 3.82 °C (38.88 °F) (276.97 K) 2.04 °C (35.67 °F) (275.19 K) 0.0 °C (32 °F) (273.15 K)
Boiling point 101.4 °C (214.5 °F) (374.55 K) 100.7 °C (213.3 °F) (373.85 K) 100.0 °C (212 °F) (373.15 K)
Density at STP (g/mL) 1.1056 1.054 0.9982
Temp. of maximum density 11.6 °C Unverified 3.98 °C[11]
Dynamic viscosity (at 20 °C, mPa·s) 1.2467 1.1248 1.0016
Surface tension (at 25 °C, N/m) 0.07187 0.07193 0.07198
Heat of fusion (kJ/mol) 6.132 6.227 6.00678
Heat of vaporisation (kJ/mol) 41.521 Unverified 40.657
pH (at 25 °C)[12] 7.44 ("pD") 7.266 ("pHD") 7.0
pKb (at 25 °C)[12] 7.44 ("pKb D2O") Unverified 7.0
Refractive index (at 20 °C, 0.5893 μm)[13] 1.32844 Unverified 1.33335

The physical properties of water and heavy water differ in several respects. Heavy water is less dissociated than light water at given temperature, and the true concentration of D+ ions is less than H+ ions would be for a light water sample at the same temperature. The same is true of OD vs. OH ions. For heavy water Kw D2O (25.0 °C) = 1.35 × 10−15, and [D+ ] must equal [OD ] for neutral water. Thus pKw D2O = p[OD] + p[D+] = 7.44 + 7.44 = 14.87 (25.0 °C), and the p[D+] of neutral heavy water at 25.0 °C is 7.44.

The pD of heavy water is generally measured using pH electrodes giving a pH (apparent) value, or pHa, and at various temperatures a true acidic pD can be estimated from the directly pH meter measured pHa, such that pD+ = pHa (apparent reading from pH meter) + 0.41. The electrode correction for alkaline conditions is 0.456 for heavy water. The alkaline correction is then pD+ = pHa(apparent reading from pH meter) + 0.456. These corrections are slightly different from the differences in p[D+] and p[OD-] of 0.44 from the corresponding ones in heavy water.[14]

Heavy water is 10.6% denser than ordinary water, and heavy water's physically different properties can be seen without equipment if a frozen sample is dropped into normal water, as it will sink. If the water is ice-cold the higher melting temperature of heavy ice can also be observed: it melts at 3.7 °C, and thus does not melt in ice-cold normal water.[15]

An early experiment reported not the "slightest difference" in taste between ordinary and heavy water.[16] However, rats given a choice between distilled normal water and heavy water were able to avoid the heavy water based on smell, and it may have a different taste.[17] Some humans have reported that heavy water produces a "burning sensation or sweet flavor".[18]

No physical properties are listed for "pure" semi-heavy water, because it is unstable as a bulk liquid. 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 could, in theory, be created via a chemical method, but it 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 deposited into a solid, semi heavy water in the form of ice could be stable. This is due to collisions between water vapour molecules being almost completely negligible in the gas phase at standard temperatures, and once crystallized, collisions between the molecules cease altogether due to the rigid lattice structure of solid ice.

History

Harold Urey discovered the isotope deuterium in 1931 and was later able to concentrate it in water.[19] Urey's mentor Gilbert Newton Lewis isolated the first sample of pure heavy water by electrolysis in 1933.[20] George de Hevesy and Erich Hofer 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.[21] The history of large-quantity production and use of heavy water in early nuclear experiments is given below.[22] Emilian Bratu and Otto Redlich studied the autodissociation of heavy water in 1934.[23]

Effect on biological systems

Different isotopes of chemical elements have slightly different chemical behaviors, but for most elements the differences are far too small to use, or even detect. For hydrogen, however, this is not true. The larger chemical isotope-effects seen between protium (light hydrogen) versus deuterium and tritium manifest because bond energies in chemistry are determined in quantum mechanics by equations in which the quantity of reduced mass of the nucleus and electrons appears. This quantity is altered in heavy-hydrogen compounds (of which deuterium oxide is the most common) more than for heavy-isotope substitution in other chemical elements.[24] This isotope effect of heavy hydrogen is magnified further in biological systems, which are very sensitive to small changes in the solvent properties of water.

Heavy water is the only known chemical substance that affects the period of circadian oscillations, consistently increasing the length of each cycle. The effect is seen in unicellular organisms, green plants, isopods, insects, birds, mice, and hamsters. The mechanism is unknown.[25]

To perform their tasks, enzymes rely on their finely tuned networks of hydrogen bonds, both in the active center with their substrates, and outside the active center, to stabilize their tertiary structures. As a hydrogen bond with deuterium is slightly stronger[26] than one involving ordinary hydrogen, in a highly deuterated environment, some normal reactions in cells are disrupted.

Particularly hard-hit by heavy water are the delicate assemblies of mitotic spindle formation necessary for cell division in eukaryotes. Plants stop growing and seeds do not germinate when given only heavy water, because heavy water stops eukaryotic cell division.[27][28] The deuterium cell is larger and is a modification of the direction of division.[29][30] The cell membrane also changes, and it reacts first to the impact of heavy water. In 1972 it was demonstrated that an increase in the percentage content of deuterium in water reduces plant growth.[31] Research conducted on the growth of prokaryote microorganisms in artificial conditions of a heavy hydrogen environment showed that in this environment, all the hydrogen atoms of water could be replaced with deuterium.[32][33][34] Experiments showed that bacteria can live in 98% heavy water.[35] However, all concentrations over 50% of deuterium in the water molecules were found to kill plants.

Effect on animals

Experiments in mice, rats, and dogs[36] have shown that a degree of 25% deuteration causes (sometimes irreversible) sterility, because neither gametes nor zygotes can develop. High concentrations of heavy water (90%) rapidly kill fish, tadpoles, flatworms, and Drosophila. Mammals (for example, rats) given heavy water to drink die after a week, at a time when their body water approaches about 50% deuteration.[37] The mode of death appears to be the same as that in cytotoxic poisoning (such as chemotherapy) or in acute radiation syndrome (though deuterium is not radioactive), and is due to deuterium's action in generally inhibiting cell division. It is more toxic to malignant cells than normal cells but the concentrations needed are too high for regular use.[36] As in chemotherapy, deuterium-poisoned mammals die of a failure of bone marrow (bleeding and infection) and intestinal-barrier functions (diarrhea and fluid loss).

Despite 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.[36][38]

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. This is a consequence of the relative difference in nuclear mass between the isotopes of hydrogen that is the greatest in all elements.[39][24] This isotopic effect alters physical properties of heavy water to a greater extent than other isotopes, and consequently induces toxicity at high concentration due to slowing down of essential biochemical reactions.[24]

Deuterium oxide is used to enhance boron neutron capture therapy, but this effect does not rely on the biological effects of deuterium per se, but instead on deuterium's ability to moderate (slow) neutrons without capturing them.[36]

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 (water being in turn 50–75% of body weight[40]) with heavy water, accidental or intentional poisoning with heavy water is unlikely to the point of practical disregard. Poisoning would require that the victim ingest large amounts of heavy water 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 6,400 hydrogen atoms is deuterium, a 50 kg human containing 32 kg of body water would normally contain enough deuterium (about 1.1 g) to make 5.5 g of pure heavy water, so roughly this dose is required to double the amount of deuterium in the body.

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.[41]

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 in Canada obtained a sample (estimated as about a "half cup") of heavy water from the primary heat transport loop of the nuclear reactor, and loaded it into a cafeteria drink dispenser. Eight employees drank some of the contaminated water. The incident was discovered when employees began leaving bioassay urine samples with elevated tritium levels. The quantity of heavy water involved was far below levels that could induce heavy water toxicity, but several employees received elevated radiation doses from tritium and neutron-activated chemicals in the water.[42] 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 actually 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.[43]

Production

On Earth, deuterated water, HDO, occurs naturally in normal water at a proportion of about 1 molecule in 3,200. This means that 1 in 6,400 hydrogen atoms is deuterium, which is 1 part in 3,200 by weight (hydrogen weight). The HDO may be separated from normal water by distillation or electrolysis and also by various chemical exchange processes, all of which exploit a kinetic isotope effect. With the partial enrichment also occurring in natural bodies of water under particular evaporation conditions.[44] (For more information about the isotopic distribution of deuterium in water, see Vienna Standard Mean Ocean Water.) In theory, deuterium for heavy water could be created in a nuclear reactor, but separation from ordinary water is the cheapest bulk production process.

The difference in mass between the two hydrogen isotopes translates into a difference in the zero-point energy and thus into a slight difference in the speed of the reaction. Once HDO becomes a significant fraction of the water, heavy water becomes 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 cost-effective process for producing heavy water is the dual temperature exchange sulfide process (known as the Girdler sulfide process) developed in parallel by Karl-Hermann Geib and Jerome S. Spevack in 1943.[45]

An alternative process,[46] patented by Graham M. Keyser, uses lasers to selectively dissociate deuterated hydrofluorocarbons to form deuterium fluoride, which can then be separated by physical means. Although the energy consumption for this process is much less than for the Girdler sulfide process, this method is currently uneconomical due to the expense of procuring the necessary hydrofluorocarbons.

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 enrichment (nuclear reactor grade) and occasionally even higher isotopic purity.

Argentina

Argentina is the main producer of heavy water, using an ammonia/hydrogen exchange based plant supplied by Switzerland's Sulzer company. It is also a major exporter to Canada, Germany, the US and other countries. The heavy water production facility located in Arroyito is the world's largest heavy water production facility. Argentina produces 200 short tons (180 tonnes) of heavy water per year using, not H2S bithermal method, but monothermal ammonia-hydrogen isotopic exchange.[47][48][49][50][51]

Soviet Union

In October 1939, Soviet physicists Yakov Borisovich Zel'dovich and Yulii Borisovich Khariton concluded that heavy water and carbon were the only feasible moderators for a natural uranium reactor, and in August 1940, along with Georgy Flyorov, submitted a plan to the Russian Academy of Sciences calculating that 15 tons of heavy water were needed for a reactor. With the Soviet Union having no uranium mines at the time, young Academy workers were sent to Leningrad photographic shops to buy uranium nitrate, but the entire heavy water project was halted in 1941 when German forces invaded during Operation Barbarossa.

By 1943, Soviet scientists had discovered that all scientific literature relating to heavy water had disappeared from the West, which Flyorov in a letter warned Soviet leader Joseph Stalin about,[52] and at which time there was only 2–3 kg of heavy water in the entire country. In late 1943, the Soviet purchasing commission in the U.S. obtained 1 kg of heavy water and a further 100 kg in February 1945, and upon World War II ending, the NKVD took over the project.

In October 1946, as part of the Russian Alsos, the NKVD deported to the Soviet Union from Germany the German scientists who had worked on heavy water production during the war, including Karl-Hermann Geib, the inventor of the Girdler sulfide process.[53] These German scientists worked under the supervision of German physical chemist Max Volmer at the Institute of Physical Chemistry in Moscow with the plant they constructed producing large quantities of heavy water by 1948.[45][54]

United States

During the Manhattan Project the United States constructed three heavy water production plants as part of the P-9 Project at Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. Heavy water was also acquired from the Cominco plant in Trail, British Columbia, Canada. The Chicago Pile-3 experimental reactor used heavy water as a moderator and went critical in 1944. The three domestic production plants were shut down in 1945 after producing around 20 metric tons of product (around 20,000 litres).[55] The Wabash plant was reopened and began resumption of heavy water production in 1952.

In 1953, the United States began using heavy water in plutonium production reactors at the Savannah River Site. The first of the five heavy water reactors came online in 1953, and the last was placed in cold shutdown in 1996. The SRS reactors were heavy water reactors so that they could produce both plutonium and tritium for the US nuclear weapons program.

The U.S. developed the Girdler sulfide chemical exchange production process—which was first demonstrated on a large scale at the Dana, Indiana plant in 1945 and at the Savannah River Plant, South Carolina in 1952. DuPont operated the SRP for the USDOE until 1 April 1989, when Westinghouse took it over.

India

India is one of the world's largest producers of heavy water through its Heavy Water Board and also exports to countries like Republic of Korea and the US. Development of heavy water process in India happened in three phases: The first phase (late 1950s 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.

Empire of Japan

In the 1930s, it was suspected by the United States and Soviet Union that Austrian chemist Fritz Johann Hansgirg built a pilot plant for the Empire of Japan in Japanese ruled northern Korea to produce heavy water by using a new process he had invented.[56]

Norway

Deuterium oxide Norsk
"Heavy water" made by Norsk Hydro

In 1934, Norsk Hydro built the first commercial heavy water plant at Vemork, Tinn, with a capacity of 12 tonnes per year.[57] From 1940 and throughout World War II, the plant was under German control and the Allies decided to destroy the plant and its heavy water to inhibit German development of nuclear weapons. In late 1942, a planned raid by British airborne troops failed, both gliders crashing. The raiders were killed in the crash or subsequently executed by the Germans. On 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.[58]

On 16 November 1943, the Allied air forces dropped more than 400 bombs on the site. The Allied air raid prompted the Nazi government to move all available heavy water to Germany for safekeeping. On 20 February 1944, a Norwegian partisan sank the ferry M/F Hydro carrying heavy water across Lake Tinn, at the cost of 14 Norwegian civilian 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.

Recent investigation of production records at Norsk Hydro and analysis of an intact barrel that was salvaged in 2004 revealed that although the barrels in this shipment contained water of pH 14—indicative of the alkaline electrolytic refinement process—they did not contain high concentrations of D2O.[59] Despite the apparent size of the 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. Hydro was carrying far too little heavy water for one reactor, let alone the 10 or more tons needed to make enough plutonium for a nuclear weapon.[59]

Israel admitted running the Dimona reactor with Norwegian heavy water sold to it in 1959. Through re-export using Romania and Germany, India probably also used Norwegian heavy water.[60][61]

Canada

As part of its contribution to the Manhattan Project, Canada built and operated a 1,000 pounds (450 kg) to 1,200 pounds (540 kg) per month (design capacity) electrolytic heavy water plant at Trail, British Columbia, which started operation in 1943.[62]

The Atomic Energy of Canada Limited (AECL) design of power reactor requires large quantities of heavy water to act as a neutron moderator and coolant. AECL ordered two heavy water plants, which were built and operated in Atlantic Canada at Glace Bay, Nova Scotia (by Deuterium of Canada Limited) and Port Hawkesbury, Nova Scotia (by General Electric Canada). These plants proved to have significant design, construction and production problems. Consequently, AECL built the Bruce Heavy Water Plant (44°11′07″N 81°21′42″W / 44.1854°N 81.3618°W),[63] which it later sold to Ontario Hydro, to ensure a reliable supply of heavy water for future power plants. The two Nova Scotia plants were shut down in 1985 when their production proved unnecessary.

The Bruce Heavy Water Plant (BHWP) in Ontario was the world's largest heavy water production plant with a capacity of 1600 tonnes per year at its peak (800 tonnes per year per full plant, two fully operational plants at its peak). It used the Girdler sulfide process to produce heavy water, and required 340,000 tonnes of feed water to produce one tonne of heavy water. It was part of a complex that included eight CANDU reactors, which provided heat and power for the heavy water plant. The site was located at Douglas Point/Bruce Nuclear Generating Station near Tiverton, Ontario, on Lake Huron where it had access to the waters of the Great Lakes.[64]

AECL issued the construction contract in 1969 for the first BHWP unit (BHWP A). Commissioning of BHWP A was done by Ontario Hydro from 1971 through 1973, with the plant entering service on June 28, 1973 and design production capacity being achieved in April 1974. Due to the success of BHWP A and the large amount of heavy water that would be required for the large numbers of upcoming planned CANDU nuclear power plant construction projects, Ontario Hydro commissioned three additional heavy water production plants for the Bruce site (BHWP B, C, and D). BHWP B was placed into service in 1979. These first two plants were significantly more efficient than planned, and the number of CANDU construction projects ended up being significantly lower than originally planned, which led to the cancellation of construction on BHWP C & D. In 1984 BHWP A was shut down. By 1993 Ontario Hydro had produced enough heavy water to meet all of its anticipated domestic needs (which were lower than expected due to improved efficiency in the use and recycling of heavy water), so they shut down and demolished half of the capacity of BHWP B. The remaining capacity continued to operate in order to fulfill demand for heavy water exports until it was permanently shut down in 1997, after which the plant was gradually dismantled and the site cleared.[65][66]

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 15–20% of the total capital cost of each CANDU plant.[66]

Iran

Since 1996 a plant for production of heavy water was being constructed at Khondab near Arak.[67] On 26 August 2006, Iranian President Ahmadinejad inaugurated the expansion of the country's heavy-water plant. 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.[68][69]

Iran produced deuterated solvents in early 2011 for the first time.[70]

The core of the IR-40 is supposed to be re-designed based on the nuclear agreement in July 2015.

Iran is permitted to store only 130 tonnes (140 short tons) of heavy water.[71] Iran exports excess production after exceeding their allotment making Iran the world's third largest exporter of heavy water.[72][73]

Pakistan

The 50 MWth 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 acquiring a tritium purification and storage plant and deuterium and tritium precursor materials from two German firms.[74]

Other countries

Romania used to produce heavy water at the now decomissioned Drobeta Girdler sulfide plant for domestic and export purposes.[75]

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

Heavy water exists in elevated concentration in the hypolimnion of Lake Tanganyika in East Africa.[76] It is likely that similar elevated concentrations exist in lakes with similar limnology, but this is only 4% enrichment (24 vs 28)[77] and surface waters are usually enriched in D
2
O
by evaporation to even greater extend by faster H
2
O
evaporation.

Applications

Nuclear magnetic resonance

Deuterium oxide is used in nuclear magnetic resonance spectroscopy when using water as solvent if the nuclide of interest is hydrogen. This is because the signal from light-water (1H2O) solvent molecules interfere with observing the signal from the molecule of interest dissolved in it. Deuterium has a different magnetic moment and therefore does not contribute to the 1H-NMR signal at the hydrogen-1 resonance frequency.

For some experiments, it may be desirable to identify the labile hydrogens on a compound, that is hydrogens that can easily exchange away as H+ ions on some positions in a molecule. With addition of D2O, sometimes referred to as a D2O shake, labile hydrogens exchange away and are substituted by deuterium (2H) atoms. These positions in the molecule then do not appear in the 1H-NMR spectrum.

Organic chemistry

Deuterium oxide is often used as the source of deuterium for preparing specifically labelled isotopologues of organic compounds. For example, C-H bonds adjacent to ketonic carbonyl groups can be replaced by C-D bonds, using acid or base catalysis. Trimethylsulfoxonium iodide, made from dimethyl sulfoxide 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 must be aware that deuterium oxide, depending upon age and origin, can contain some tritium.

Infrared spectroscopy

Deuterium oxide is often used instead of water when collecting FTIR spectra of proteins in solution. H2O creates a strong band that overlaps with the amide I region of proteins. The band from D2O is shifted away from the amide I region.

Neutron moderator

Heavy water is used in certain types of nuclear reactors, where it acts as a neutron moderator to slow down neutrons so that they are more likely to react with the fissile uranium-235 than with uranium-238, which captures neutrons without fissioning. The CANDU reactor uses this design. Light water also acts as a moderator, but because light water absorbs more neutrons than heavy water, reactors using light water for a reactor moderator must use enriched uranium rather than natural uranium, otherwise criticality is impossible. A significant fraction of outdated power reactors, such as the RBMK 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) has led to the discontinuation of graphite in standard reactor designs.

Because they do not require uranium enrichment, heavy water reactors are more of a concern in regards to nuclear proliferation. The breeding and extraction of plutonium can be a relatively rapid and cheap route to building a nuclear weapon, as chemical separation of plutonium from fuel is easier than isotopic separation of U-235 from natural uranium. Among current and past nuclear weapons states, Israel, India, and North Korea[78] first used plutonium from heavy water moderated reactors burning natural uranium, while China, South Africa and Pakistan first built weapons using highly enriched uranium.

In the U.S., however, the first experimental atomic reactor (1942), as well as the Manhattan Project Hanford production reactors that produced the plutonium for the Trinity test and Fat Man bombs, all used pure carbon (graphite) neutron moderators combined with normal water cooling pipes. They functioned with neither enriched uranium nor heavy water. Russian and British plutonium production also used graphite-moderated reactors.

There is no evidence that civilian heavy water power reactors—such as the CANDU or Atucha designs—have been used to produce military fissile materials. In nations that do not already possess nuclear weapons, nuclear material at these facilities is under IAEA safeguards to discourage any 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.

Neutrino detector

The Sudbury Neutrino Observatory (SNO) in Sudbury, Ontario uses 1,000 tonnes of heavy water on loan from Atomic Energy of Canada Limited. The neutrino detector is 6,800 feet (2,100 m) underground in a mine, to shield it from muons produced by cosmic rays. SNO was built to answer the question of whether or not electron-type neutrinos produced by fusion in the Sun (the only type the Sun should be producing directly, according to theory) might be able to turn into other types of neutrinos on the way to Earth. SNO detects the Cherenkov radiation in the water from high-energy electrons produced from electron-type neutrinos as they undergo charged current (CC) interactions with neutrons in deuterium, turning them into protons and electrons (however, only the electrons are fast enough to produce Cherenkov radiation for detection). SNO also detects neutrino↔electron scattering (ES) events, where the neutrino transfers energy to the electron, which then proceeds to generate Cherenkov radiation distinguishable from that produced by CC events. The first of these two reactions is produced only by electron-type neutrinos, while the second can be caused by all of the neutrino flavors. The use of deuterium is critical to the SNO function, because all three "flavours" (types) of neutrinos[79] may be detected in a third type of reaction as well, neutrino-disintegration, in which a neutrino of any type (electron, muon, or tau) scatters from a deuterium nucleus (deuteron), transferring enough energy to break up the loosely bound deuteron into a free neutron and proton via a neutral current (NC) interaction. This event is detected when the free neutron is absorbed by 35Cl present from NaCl 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 and 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.

Tritium production

Tritium 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 for boosted fission weapons and initiators. Some tritium is created in heavy water moderated reactors when deuterium captures a neutron. This reaction has a small cross-section (probability of a single neutron-capture event) 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 require reactors with very high neutron fluxes, or with a very high proportion of heavy water to nuclear fuel and very low neutron absorption by other reactor material. The tritium would then have to be recovered by isotope separation from a much larger quantity of deuterium, unlike production from lithium-6 (the present method), where only chemical separation is needed.

Deuterium's absorption cross section for thermal neutrons is 0.52 millibarns (5.2 × 10−32 m2; 1 barn = 10−28 m2), while those of oxygen-16 and oxygen-17 are 0.19 and 0.24 millibarns, respectively. 17O makes up 0.038% of natural oxygen, making the overall cross section 0.28 millibarns. Therefore, in D2O with natural oxygen, 21% of neutron captures are on oxygen, rising higher as 17O builds up from neutron capture on 16O. Also, 17O may emit an alpha particle on neutron capture, producing radioactive carbon-14.

See also

References

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External links

Advanced heavy-water reactor

The advanced heavy-water reactor (AHWR) is the latest Indian design for a next-generation nuclear reactor that burns thorium in its fuel core. It is slated to form the third stage in India's three-stage fuel-cycle plan. This phase of the fuel cycle plan is supposed to be built starting with a 300MWe prototype in 2016.

CANDU reactor

The CANDU, for Canada Deuterium Uranium, is a Canadian pressurized heavy-water reactor design used to generate electric power. The acronym refers to its deuterium oxide (heavy water) moderator and its use of (originally, natural) uranium fuel. CANDU reactors were first developed in the late 1950s and 1960s by a partnership between Atomic Energy of Canada Limited (AECL), the Hydro-Electric Power Commission of Ontario, Canadian General Electric, and other companies.

There have been two major types of CANDU reactors, the original design of around 500 MWe that was intended to be used in multi-reactor installations in large plants, and the rationalized CANDU 6 in the 600 MWe class that is designed to be used in single stand-alone units or in small multi-unit plants. CANDU 6 units were built in Quebec and New Brunswick, as well as Pakistan, Argentina, South Korea, Romania, and China. A single example of a non-CANDU 6 design was sold to India. The multi-unit design was used only in Ontario, Canada, and grew in size and power as more units were installed in the province, reaching ~880 MWe in the units installed at the Darlington Nuclear Generating Station. An effort to rationalize the larger units in a fashion similar to CANDU 6 led to the CANDU 9.

By the early 2000s, sales prospects for the original CANDU designs were dwindling due to the introduction of newer designs from other companies. AECL responded by cancelling CANDU 9 development and moving to the Advanced CANDU reactor (ACR) design. ACR failed to find any buyers; its last potential sale was for an expansion at Darlington, but this was cancelled in 2009. In October 2011, the Canadian Federal Government licensed the CANDU design to Candu Energy (a wholly owned subsidiary of SNC-Lavalin), which also acquired the former reactor development and marketing division of AECL at that time. Candu Energy offers support services for existing sites and is completing formerly stalled installations in Romania and Argentina through a partnership with China National Nuclear Corporation. SNC Lavalin, the successor to AECL, is pursuing new Candu 6 reactor sales in Argentina (Atucha 3), as well as China and Britain. Sales effort for the ACR reactor has ended.

Carolinas–Virginia Tube Reactor

Carolinas–Virginia Tube Reactor (CVTR), also known as Parr Nuclear Station, was an experimental pressurized tube heavy water nuclear power reactor at Parr, South Carolina in Fairfield County. It was built and operated by the Carolinas Virginia Nuclear Power Associates.

Deuterium

Deuterium (or hydrogen-2, symbol D or 2H, also known as heavy hydrogen) is one of two stable isotopes of hydrogen (the other being protium, or hydrogen-1). The nucleus of deuterium, called a deuteron, contains one proton and one neutron, whereas the far more common protium has no neutron in the nucleus. Deuterium has a natural abundance in Earth's oceans of about one atom in 6420 of hydrogen. Thus deuterium accounts for approximately 0.0156% (or, on a mass basis, 0.0312%) of all the naturally occurring hydrogen in the oceans, while protium accounts for more than 99.98%. The abundance of deuterium changes slightly from one kind of natural water to another (see Vienna Standard Mean Ocean Water).

The deuterium isotope's name is formed from the Greek deuteros, meaning "second", to denote the two particles composing the nucleus. Deuterium was discovered and named in 1931 by Harold Urey. When the neutron was discovered in 1932, this made the nuclear structure of deuterium obvious, and Urey won the Nobel Prize in 1934. Soon after deuterium's discovery, Urey and others produced samples of "heavy water" in which the deuterium content had been highly concentrated.

Deuterium is destroyed in the interiors of stars faster than it is produced. Other natural processes are thought to produce only an insignificant amount of deuterium. Nearly all deuterium found in nature was produced in the Big Bang 13.8 billion years ago, as the basic or primordial ratio of hydrogen-1 to deuterium (about 26 atoms of deuterium per million hydrogen atoms) has its origin from that time. This is the ratio found in the gas giant planets, such as Jupiter. However, other astronomical bodies are found to have different ratios of deuterium to hydrogen-1. This is thought to be a result of natural isotope separation processes that occur from solar heating of ices in comets. Like the water cycle in Earth's weather, such heating processes may enrich deuterium with respect to protium. The analysis of deuterium/protium ratios in comets found results very similar to the mean ratio in Earth's oceans (156 atoms of deuterium per million hydrogens). This reinforces theories that much of Earth's ocean water is of cometary origin. The deuterium/protium ratio of the comet 67P/Churyumov-Gerasimenko, as measured by the Rosetta space probe, is about three times that of earth water. This figure is the highest yet measured in a comet.Deuterium/protium ratios thus continue to be an active topic of research in both astronomy and climatology.

Fugen Nuclear Power Plant

Fugen ふげん (Fugen) was a prototype Japanese nuclear test reactor.

Fugen was a domestic Japanese design for a demonstration Advanced Thermal Reactor. It was a heavy water moderated, boiling light water cooled reactor.

The reactor was started in 1979 and shut down in 2003. As of 2018, it is undergoing decommissioning.

It is located in Myōjin-chō, in the city of Tsuruga, Fukui.

The name "Fugen" is derived from Fugen Bosatsu (Samantabhadra), a Buddhist deity.

The reactor was the first in the world to use a full MOX fuel core.

It had 772 assemblies, the most in the world. It has received the title of a historic landmark from the American Nuclear Society.

The design boils ordinary water like a boiling water reactor (BWR) but uses heavy water as a moderator as in a CANDU reactor.

The electrical output was 165 MW and the thermal output was 557 MW.

Core temperature: 300 °C

Pellet centerline temperature: 2200 °C

Fuel conversion time: 6 monthsThe plant is located on a site that covers 267,694 m2 (66 acres); buildings occupy 7,762 m2 (1.9 acres), and it has 46,488 m2 of floor space. It employed 256 workers.

IR-40

IR-40 is an Iranian 40 megawatt (thermal) heavy water reactor under construction at Khondab, near Arak, adjacent to the 1990s era Arak Heavy Water Production Plant. Civil works for the construction began in October 2004. It was initially planned that the reactor would begin nuclear operations in 2014.

KS 150

KS 150 is a Gas Cooled Reactor using Heavy Water as a moderator (GCHWR) nuclear reactor design. A single example, A-1, was constructed at the Bohunice Nuclear Power Plant in Jaslovské Bohunice, Czechoslovakia. The power plant suffered a series of accidents, the worst being an accident on February 22, 1977 rated INES-4. Since 1979 the plant has been undergoing decommissioning.

Montreal Laboratory

The Montreal Laboratory in Montreal, Quebec, Canada, was established by the National Research Council of Canada during World War II to undertake nuclear research in collaboration with the United Kingdom, and to absorb some of the scientists and work of the Tube Alloys nuclear project in Britain. It became part of the Manhattan Project, and designed and built some of the world's first nuclear reactors.

After the Fall of France, some French scientists escaped to Britain with their stock of heavy water. They were temporarily installed in the Cavendish Laboratory at the University of Cambridge, where they worked on reactor design. The MAUD Committee was uncertain whether this was relevant to the main task of Tube Alloys, that of building an atomic bomb, although there remained a possibility that a reactor could be used to breed plutonium, which might be used in one. It therefore recommended that they be relocated to the United States, and co-located with the Manhattan Project's reactor effort. Due to American concerns about security (many of the scientists were foreign nationals) and patent claims by the French scientists and Imperial Chemical Industries (ICI), it was decided to relocate them to Canada instead.

The Canadian government agreed to the proposal, and the Montreal Laboratory was established in a house belonging to McGill University; it moved to permanent accommodation at the Université de Montréal in March 1943. The first eight laboratory staff arrived in Montreal at the end of 1942. These were Bertrand Goldschmidt and Pierre Auger from France, George Placzek from Czechoslovakia, S. G. Bauer from Switzerland, Friedrich Paneth and Hans von Halban from Austria, and R. E. Newell and F. R. Jackson from Britain. The Canadian contingent included George Volkoff, Bernice Weldon Sargent and George Laurence, and promising young Canadian scientists such as J. Carson Mark, Phil Wallace and Leo Yaffe.

Although Canada was a major source of uranium ore and heavy water, these were controlled by the Americans. Anglo-American cooperation broke down, denying the Montreal Laboratory scientists access to the materials they needed to build a reactor. In 1943, the Quebec Agreement merged Tube Alloys with the American Manhattan Project. The Americans agreed to help build the reactor. Scientists who were not British subjects left, and John Cockcroft became the new director of the Montreal Laboratory in May 1944. The Chalk River Laboratories opened in 1944, and the Montreal Laboratory was closed in July 1946. Two reactors were built at Chalk River. The small ZEEP went critical on 5 September 1945, and the larger NRX on 21 July 1947. NRX was for a time the most powerful research reactor in the world.

Møsvatn

Møsvatn (or Møsvann) is tenth-largest lake in Norway with a surface area of 78.31 km2. It lies primarily Møsstrond, Vinje in Telemark. The lake lies in the watershed of the Skien river (Skiensvassdrag) and discharges into the Måna river. Along the shores of the lake, many traces of stone age settlers can be found. It is 919 meters above sea level and regulated to use for hydroelectric production. Some of Norway’s highest mountain farms can be found here as well.

On 19 November 1942, as part of the efforts to sabotage German heavy water production, gliderborne troops were to land on the frozen lake Møsvatn near the Vemork hydroelectric plant, run by Norsk Hydro, near Rjukan. This effort was not successful; however ultimately the Norwegians stopped the heavy water production activities and helped limit the German nuclear weapons research program.

The museum and visitor's centre Hardangervidda Natursenter is located close to the lake. From Skinnarbu there is a boattrip with the MB Fjellvåken to Mogen.

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 or a similar fissile nuclide.

Commonly used moderators include regular (light) water (roughly 75% of the world's reactors), solid graphite (20% of reactors) and heavy water (5% of reactors).Beryllium has also been used in some experimental types, and hydrocarbons have been suggested as another possibility.

Norwegian heavy water sabotage

The Norwegian heavy water sabotage (Bokmål: Tungtvannsaksjonen, Nynorsk: Tungtvassaksjonen) was a series of operations undertaken by Norwegian saboteurs during World War II to prevent the German nuclear weapon project from acquiring heavy water (deuterium oxide), which could have been used by the Germans to produce nuclear weapons. In 1934, at Vemork, Norway, Norsk Hydro built the first commercial plant capable of producing heavy water as a byproduct of fertilizer production. It had a capacity of 12 tonnes per year. During World War II, the Allies decided to remove the heavy water supply and destroy the heavy water plant in order to inhibit the German development of nuclear weapons. Raids were aimed at the 60 MW Vemork power station at the Rjukan waterfall in Telemark, Norway.

Prior to the German invasion of Norway on 9 April 1940, the Deuxième Bureau (French military intelligence) removed 185 kg (408 lb) of heavy water from the plant in Vemork in then-neutral Norway. The plant's managing director, Aubert, agreed to lend the heavy water to France for the duration of the war. The French transported it secretly to Oslo, on to Perth, Scotland, and then to France. The plant remained capable of producing heavy water. The Allies remained concerned that the occupation forces would use the facility to produce more heavy water for their weapons programme. Between 1940 and 1944, a sequence of sabotage actions, by the Norwegian resistance movement—as well as Allied bombing—ensured the destruction of the plant and the loss of the heavy water produced. These operations—codenamed Grouse, Freshman, and Gunnerside—finally managed to knock the plant out of production in early 1943.

In Operation Grouse, the British Special Operations Executive (SOE) successfully placed four Norwegian nationals as an advance team in the region of the Hardanger Plateau above the plant in October 1942. The unsuccessful Operation Freshman was mounted the following month by British paratroopers; they were to rendezvous with the Norwegians of Operation Grouse and proceed to Vemork. This attempt failed when the military gliders crashed short of their destination, as did one of the tugs, a Handley Page Halifax bomber. The other Halifax returned to base, but all the other participants were killed in the crashes or captured, interrogated, and executed by the Gestapo.

In February 1943, a team of SOE-trained Norwegian commandos succeeded in destroying the production facility with a second attempt, Operation Gunnerside, later evaluated by SOE as the most successful act of sabotage in all of World War II. These actions were followed by Allied bombing raids. The Germans elected to cease operation and remove the remaining heavy water to Germany, but Norwegian resistance forces sank the ferry carrying the water, SF Hydro, on Lake Tinn.

Operation Freshman

Operation Freshman was the codename given to a British airborne operation conducted in November 1942 during World War II. It was the first British airborne operation conducted using Airspeed Horsa gliders, and its target was the Vemork Norsk Hydro chemical plant in Telemark, Norway which produced heavy water for Nazi Germany. By 1942, the German nuclear weapons programme had come close to being able to develop a nuclear reactor, but in order for the reactor to function it would require a great deal of heavy water. The source of the heavy water was the Norsk Hydro plant, which had been occupied in 1940; when the British government learned of the German nuclear developments, it was decided that a raid would be launched to destroy the plant and deny the Germans the heavy water required to develop a nuclear weapon. Several tactics were discussed and discarded as impractical, and it was finally decided that a small airborne force composed of sappers from the Royal Engineer units attached to 1st Airborne Division would land by glider a short distance from the plant, demolish it with explosives and then escape over the Norwegian border into Sweden.

After a period of extensive training, the airborne force took off in two aircraft–glider combinations on the night of 19 November 1942. Both managed to reach the Norwegian coast, but neither was able to reach their objective. The first pair suffered from navigational difficulties and severe weather, which resulted in the tow rope snapping and the first glider crash-landing, with its Halifax tug aircraft returning to base; three airborne troops were killed outright, with the survivors captured shortly after the crash. The second pair fared even worse, with both aircraft and glider crashing into a mountain for unknown reasons; the aircrew and some airborne troops were killed outright, and those who survived were taken prisoner. None survived for very long, being executed as a result of Adolf Hitler's Commando Order, which stated all Commando personnel were to be immediately executed upon capture. At the end of the war, Wehrmacht personnel were tried and condemned to death for their part in the executions.

P-9 Project

The P-9 Project was the codename given during World War II to the Manhattan Project's heavy water production program. The Cominco plant at Trail, British Columbia, was upgraded to produce heavy water. DuPont built three plants in the United States: at the Morgantown Ordnance Works, near Morgantown, West Virginia; at the Wabash River Ordnance Works, near Dana and Newport, Indiana; and at the Alabama Ordnance Works, near Childersburg and Sylacauga, Alabama. The American plants operated from 1943 until 1945. The Canadian plant at Trail continued in operation until 1956. Three nuclear reactors were built using the heavy water produced by the P-9 Project: Chicago Pile 3 at Argonne, and ZEEP and NRX at the Chalk River Laboratories in Canada.

Pressurized heavy-water reactor

A pressurized heavy-water reactor (PHWR) is a nuclear reactor, commonly using natural uranium as its fuel, that uses heavy water (deuterium oxide D2O) as its coolant and neutron moderator. The heavy water coolant is kept under pressure, allowing it to be heated to higher temperatures without boiling, much as in a pressurized water reactor. While heavy water is significantly more expensive than ordinary light water, it creates greatly enhanced neutron economy, allowing the reactor to operate without fuel-enrichment facilities (offsetting the additional expense of the heavy water) and enhancing the ability of the reactor to make use of alternate fuel cycles. At the beginning of 2001, 31 heavy water cooled and moderated nuclear power plants were in operation, having a total capacity of 16.5 GW(e), representing roughly 7.76% by number and 4.7% by generating capacity of all current operating reactors.

R4 nuclear reactor

R4 nuclear reactor was a nuclear reactor built at Marviken and the fourth nuclear reactor built in Sweden. It was heavy water moderated and intended for the dual role of 130MWe of power generation as well as plutonium production. It had a central role in the Swedish nuclear weapon programme. During the mid 1960s, the social democratic government officially abandoned the project of designing Swedish nuclear weapons and the Marviken-plant became derelict. It was never loaded with fuel, and the project was cancelled in 1970.

The turbine hall was subsequently used for an oil-fired power station, and the pressure vessel and containment building were subsequently used for experiments into reactor behaviour under accident conditions.

The Nuclear reactor, the oil fired power station and surronding 250 hectares of land and water was acquired by Synthesis Real Estate during 2018.

Steam-generating heavy water reactor

Steam Generating Heavy Water Reactor (SGHWR) is a United Kingdom design for commercial nuclear reactors. It is similar to the Canadian CANDU reactor designs in that it uses a low-pressure reactor vessel containing high-pressure piping for the coolant, which reduces construction costs and complexity.

SGHWR was a heavy water moderated reactor, which used ordinary (light) water as coolant, in contrast with earlier UK designs that used graphite moderators which led to very large reactor sizes. Unlike CANDU, the SGHWR uses slightly enriched uranium fuel, which allows for higher burnup and more economical fuel cycles. The modern CANDU ACR-1000 reactor design uses a similar concept, as does the Italian CIRENE, hosted at Latina Nuclear Power Plant.

Only a single SGHWR was ever built, the small 100 MW prototype reactor at Winfrith, often known simply as the "Winfrith Reactor". It was connected to the grid in 1967 and ceased operation in 1990 after 23 successful years. [1] It was owned by the United Kingdom Atomic Energy Authority. Decommissioning is now being carried out by Magnox Ltd on behalf of the Nuclear Decommissioning Authority.

A similar design was the Gentilly Nuclear Generating Station in Quebec, but this was not successful and shut down after a short lifetime.

Tinnsjå

Tinnsjå (English: Lake Tinn), also called Tinnsjø and Tinnsjøen, is one of the largest lakes in Norway, and one of the deepest in Europe. It is located between the municipalities of Tinn and Notodden in Telemark county. At its source in the west, the Måna river flows out of Møsvatn and past Rjukan into Tinnsjå. From the north, the river Mår flows from the Mår, Gøystavatn, and Kalhovdfjorden lakes into Tinnsjå. Tinnsjå is part of the Skiensvassdrag, and drains via the Tinnelva river in the south, down to Heddalsvatn.

In 1944, during the German occupation of Norway, the ferry SF Hydro was sunk in Tinnsjå by the Norwegian resistance. The Germans were using the ferry to transport a large quantity of heavy water to Germany, where it was to be used for nuclear weapon research. The heavy water had been produced at Vemork, a factory located in Rjukan. The wreck of the ferry was discovered in 1993. In 2004, it was investigated and filmed for an episode of NOVA; heavy water samples were recovered and deuterium isotopic enrichment was confirmed.

In 2004 a film crew shooting footage for a new documentary on the heavy water sabotage became aware of an unusual fish, swimming near the lake bottom at a depth of 430 m. Two specimens of the previously unknown fish were captured in April 2005. Analysis revealed the fish to be closely related to Arctic char. The light-colored, translucent fish is up to 15 cm long and lacks a swim bladder.

Tritiated water

Tritiated water is a radioactive form of water where the usual protium atoms are replaced with tritium. In its pure form it may be called tritium oxide (T2O or 3H2O) or super-heavy water. Pure T2O is corrosive due to self-radiolysis. Diluted, tritiated water is mainly H2O plus some HTO (3HOH). It is also used as a tracer for water transport studies in life-science research. Furthermore, since it naturally occurs in minute quantities, it can be used to determine the age of various water-based liquids, such as vintage wines.

The name super-heavy water helps distinguish the tritiated material from heavy water, which instead contains deuterium.

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. At opening, it was the world's largest power plant with a capacity of 108 MW.Vemork was later the site of the first plant in the world to mass-produce heavy water developing from the hydrogen production then used for the Haber process. During World War II, Vemork was the target of Norwegian heavy water sabotage operations. The heavy water plant was closed in 1971, and in 1988 the power station became the Norwegian Industrial Workers Museum.

A new power plant was opened in 1971 and is located inside the mountain behind the old.

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