Heavy water

Heavy water, also known as deuterium oxide (²H₂O or D₂O), is a special kind of water where the hydrogen atoms are made of deuterium, a heavier form of hydrogen, instead of the common hydrogen found in regular water. Because of this difference, heavy water has unique properties that make it useful in science and industry.

Deuterium is a heavy isotope of hydrogen, and heavy water contains these deuterium atoms. It is often used in nuclear reactors and has different physical properties from regular water. For example, it is about 10.6% denser and has a higher melting point. Heavy water can affect living things by changing how enzymes and cells work, and very high amounts can be harmful.

One of the most common ways to make heavy water is through a process called the Girdler sulfide process. Heavy water is used in many different areas, such as nuclear magnetic resonance, infrared spectroscopy, and neutron moderation. It also helps in detecting particles called neutrinos and in creating important radioactive materials like plutonium and tritium.

Composition

The nucleus of a deuterium atom has a neutron and a proton, while a normal hydrogen atom has just a proton. This extra neutron makes deuterium about twice as heavy as normal hydrogen.

A molecule of heavy water has two deuterium atoms instead of the two normal hydrogen atoms found in regular water. Heavy water is not radioactive and is only a little heavier than normal water. However, because deuterium is much heavier than normal hydrogen, it can change how some chemical reactions work in living things. Our bodies naturally contain a small amount of deuterium, which is harmless. But if too much heavy water replaces normal water in living things, it can stop cells from working properly.

Heavy water was first made in 1932, and it became important for early nuclear energy research after the discovery of nuclear fission in 1938. It is used in some reactors because it can help control the nuclear reactions better than other materials.

Other heavy forms of water

Semiheavy water

Semiheavy water, HDO, is found when water has both light hydrogen (¹H) and deuterium (²H). This happens because hydrogen atoms switch between water molecules quickly. In normal water, about 1 in 3,200 molecules is HDO, and pure heavy water molecules (D₂O) are much rarer.

Heavy-oxygen water

Water with heavier oxygen atoms ¹⁷O and ¹⁸O is also available. It is denser than normal water but is not usually called heavy water because it does not have extra deuterium. This type of water is used to make fluorine-18 for radiopharmaceuticals and radiotracers, as well as in positron emission tomography. It is more expensive to produce because separating these oxygen atoms is difficult.

Tritiated water

Tritiated water contains tritium (³H) instead of normal hydrogen. Because tritium is radioactive, tritiated water is also radioactive.

Physical properties

Heavy water looks and feels a bit different from regular water. It is denser, about 10.6% heavier, so if you drop a piece of frozen heavy water ice into normal water, it will sink to the bottom. Heavy water ice also melts at a higher temperature (3.7 °C) compared to regular ice, so it won’t melt in very cold water.

People have noticed that heavy water might taste a little sweet. Some animals can even tell the difference by smell. Unlike regular water, heavy water doesn’t have the same blue color because its molecules vibrate differently, which changes how it absorbs light.

History

In 1931, a scientist named Harold Urey discovered a special kind of hydrogen called deuterium. Later, he was able to collect it in water. Another scientist, Gilbert Newton Lewis, made the first sample of pure heavy water in 1933.

During World War II, a company in Sweden made heavy water and sold it to both Germany and the Manhattan Project. After the war, scientists from Germany who had worked on heavy water were brought to the Soviet Union to help make more of it.

Effect on biological systems

Different types of hydrogen atoms can act a little differently in chemical reactions. This is especially true for hydrogen and its heavier form, called deuterium, which is found in a special kind of water known as heavy water. These small changes can affect living things because even tiny differences matter in biological processes.

Heavy water can disrupt some important cell activities, especially those that need precise arrangements of molecules held together by hydrogen bonds. Because bonds with deuterium are slightly stronger, some normal cell processes don’t work right. For example, plants may stop growing, and some animals can become unable to have babies or even stop living when exposed to too much heavy water. However, some simple organisms, like certain kinds of bacteria, can survive in environments where water contains mostly deuterium.

Production methods

The most common way to make heavy water is called the Girdler sulfide process. This method was created in 1943 by two scientists. Today, heavy water is usually sold in different levels of purity, ranging from 98% to almost 100% pure.

Production by country

Argentina

Argentina was a main producer of heavy water, using a plant supplied by Switzerland's Sulzer company. It was also a big exporter to Canada, Germany, the US, and other countries. The heavy water facility in Arroyito was the world's largest. Argentina made 200 short tons (180 tonnes) of heavy water each year in 2015. Since 2017, this plant has not been working.

United States

During the Manhattan Project, the United States built three heavy water production plants as part of the P-9 Project in Morgantown, West Virginia, near Newport, Indiana, and near Childersburg and Sylacauga, Alabama. Heavy water was also gotten from a plant in Trail, British Columbia, Canada. The Chicago Pile-3 experimental reactor used heavy water and started working in 1944. The three plants in the US stopped in 1945 after making about 81,470 lb (36,950 kg) of heavy water. One plant in Indiana started making heavy water again in 1952.

In 1953, the United States began using heavy water in plutonium production reactors at the Savannah River Site. The first of five heavy water reactors began working in 1953, and the last stopped in 1996. These reactors were used to make both plutonium and tritium for the US nuclear weapons program.

The US created the Girdler sulfide chemical exchange method, first shown at a large scale in Dana, Indiana in 1945 and at the Savannah River Site in 1952.

India

India makes the most heavy water in the world through its Heavy Water Board. It sells heavy water to countries like the Republic of Korea, China, and the United States.

Norway

Main article: Norwegian heavy water sabotage

In 1934, Norsk Hydro built the first commercial heavy water plant at Vemork, Tinn, making 4 kilograms (8.8 lb) each day. From 1940 through World War II, the plant was controlled by Germany, and the Allies tried to destroy it to stop Germany from making nuclear weapons. In late 1942, a British raid called Operation Freshman failed.

On the night of 27 February 1943, Operation Gunnerside succeeded. Norwegian commandos and local resistance workers damaged important parts of the plant, and heavy water was dumped down the factory drains.

On 16 November 1943, Allied airplanes dropped bombs on the site. This led the Nazi government to move heavy water to Germany for safety. On 20 February 1944, Norwegian resistance members sank a ferry, the M/F Hydro, carrying heavy water across Lake Tinn. Most of the heavy water was lost. Some barrels may have been saved and taken to Germany.

Recent checks of records and a barrel saved in 2004 showed that the water carried was not very pure heavy water. Germany would have needed about 5 tons of heavy water to run a nuclear reactor, but only about half a ton was being sent to Germany. The German nuclear weapons program was not as advanced as the Manhattan Project, and no reactor in Nazi Germany came close to starting up. Even if they had more heavy water, it would not have helped.

Israel admitted using Norwegian heavy water sold to it in 1959 in its Dimona reactor. India likely also used Norwegian heavy water through deals with Romania and Germany.

Canada

As part of its work on the Manhattan Project, Canada built and ran a plant at Trail, British Columbia to make heavy water, starting in 1943.

The Atomic Energy of Canada Limited (AECL) needs lots of heavy water for its power reactors. AECL built two heavy water plants in Atlantic Canada at Glace Bay, Nova Scotia, and Point Tupper, Richmond County, Nova Scotia. These plants had problems, but the Glace Bay plant reached full production in 1984 and the Point Tupper plant in 1974. The two Nova Scotia plants stopped in 1985 because they were not needed anymore.

The Bruce Heavy Water Plant (BHWP) in Ontario was the world's biggest heavy water plant, able to make 1600 tonnes each year at its peak. It used the Girdler sulfide process and needed 340,000 tonnes of water to make one tonne of heavy water. It was part of a group that included eight CANDU reactors, which gave heat and power to the plant. The plant was at Douglas Point/Bruce Nuclear Generating Station near Tiverton, Ontario, close to Lake Huron and the Great Lakes.

AECL gave the contract in 1969 for the first BHWP unit (BHWP A). It started working in 1973 and reached full production in 1974. Because BHWP A worked well and fewer CANDU reactors were being built than expected, plans for three more plants (BHWP C & D) were stopped. BHWP A stopped in 1984. By 1993, Ontario Hydro had enough heavy water, so they shut down half of BHWP B. The rest kept working to sell heavy water until it stopped for good in 1997. The plant was then taken apart.

Iran

Since 1996, a plant to make heavy water has been built near Arak. On 26 August 2006, Iranian President Ahmadinejad opened an expansion of the plant. Iran says the plant will work with a 40 MW research reactor planned to finish in 2009. Iran made deuterated solvents for the first time in early 2011. The core of the IR-40 is planned to be changed based on the nuclear agreement from July 2015.

Under the Joint Comprehensive Plan of Action, Iran can only keep 130 tonnes (140 short tons) of heavy water. Iran sells extra heavy water, making it the world's third biggest seller. In 2023, Iran sells heavy water, and buyers have offered over 1,000 dollars per liter.

Pakistan

In Pakistan, there are two heavy water production sites in Punjab. The Khushab Nuclear Complex, started in 1995–96, is a key part of Pakistan's program to make weapon-grade plutonium, deuterium, and tritium for advanced warheads (i.e. thermonuclear weapons). Another heavy water facility in Multan makes heavy water for nuclear power plants in Karachi and Chashma.

In the early 1980s, Pakistan got a tritium cleaning and storing plant and materials for making deuterium and tritium from two firms in East Germany. Unlike India and Iran, Pakistan does not sell its heavy water; it is only used for its weapons program and local nuclear power plants.

Other countries

Romania made heavy water at the now-closed Drobeta Girdler sulfide plant for home use and to sell. France had a small plant in the 1950s and 1960s.^{[citation needed]}

Applications

Nuclear magnetic resonance

Deuterium oxide is used in special tests to study chemicals when water is needed. Normal water can make it hard to see the results, but deuterium oxide helps scientists get clearer answers. It works because deuterium behaves differently in tests.

Organic chemistry

Deuterium oxide helps scientists create special versions of chemical compounds. This is useful for studying how chemicals change and react in experiments.

Infrared spectroscopy

Deuterium oxide is used instead of water when studying proteins. Normal water can block some details, but deuterium oxide makes it easier to see what’s happening.

Neutron moderator

Heavy water is used in some nuclear reactors to slow down particles. This helps the reactor work safely with natural uranium. Most reactors use different materials, but heavy water has special uses.

Neutrino detector

The Sudbury Neutrino Observatory used a huge amount of heavy water to study tiny particles from the Sun. The heavy water helped scientists learn how these particles change during their journey to Earth.

Metabolic rate and water turnover testing in physiology and biology

Heavy water mixed with special water is used to measure how fast animals and people use energy. It helps scientists understand how bodies stay healthy.

Tritium production

Tritium, a material used in glow-in-the-dark items and special science work, can be made in heavy water reactors. However, only small amounts are produced this way. Most tritium comes from other methods.