Heavy water

Heavy water, also known as deuterium oxide (²H₂O or D₂O), is a special kind of water. In heavy water, the hydrogen atoms are made of deuterium, a heavier form of hydrogen, instead of the common hydrogen in regular water. This makes heavy water have unique properties.

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

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 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 in regular water. Heavy water is not radioactive and is only a little heavier than normal water. Because deuterium is heavier, 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, 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 nuclear reactions better than other materials.

Other heavy forms of water

Semiheavy water

Semiheavy water, HDO, is a type of water that has both light hydrogen (¹H) and deuterium (²H). This happens because hydrogen atoms move between water molecules quickly. In normal water, about 1 in 3,200 molecules is HDO.

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. If you drop a piece of frozen heavy water ice into normal water, it will sink to the bottom. Heavy water ice melts at a higher temperature (3.7 °C) than 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 found a special kind of hydrogen called deuterium. Later, he collected 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 worked on heavy water went to the Soviet Union to help make more.

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.

Heavy water can disrupt some important cell activities. 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 have trouble having 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, from 98% to almost 100% pure.

Production by country

Argentina

Argentina was an important maker of heavy water. It used a factory from Sulzer in Switzerland. The biggest factory was in Arroyito. In 2015, it made 200 short tons (180 tonnes) each year. But since 2017, this factory has not worked.

United States

During the Manhattan Project, the United States built three factories to make heavy water. These were part of the P-9 Project in places like Morgantown, West Virginia and Childersburg. One factory in Indiana started again in 1952.

The United States also used heavy water to help make plutonium. The first factory began in 1953 and the last stopped in 1996.

India

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

Norway

Main article: Norwegian heavy water sabotage

In 1934, Norsk Hydro built the first factory to make heavy water at Vemork. During World War II, Germany took control of the factory. The Allies tried to stop them. In 1943, Norwegian commandos damaged the factory. Later, Allied airplanes bombed it. In 1944, Norwegian resistance members sank a ferry carrying heavy water.

Canada

Canada built a factory at Trail, British Columbia during the Manhattan Project.

The Atomic Energy of Canada Limited (AECL) needed heavy water for its power plants. Two factories in Atlantic Canada had problems but later worked well. The biggest factory was the Bruce Heavy Water Plant (BHWP) in Ontario. It could make 1600 tonnes each year. It stopped working in 1997.

Iran

Since 1996, Iran has built a factory to make heavy water near Arak. Iran says it will use the heavy water for a research reactor. Under an agreement, Iran can only keep a small amount of heavy water and sells the extra.

Pakistan

Pakistan has two factories to make heavy water in Punjab. One is part of its weapons program. Pakistan does not sell its heavy water; it uses it for its own nuclear plants.

Other countries

Romania once made heavy water for its own use and to sell. France also had a small factory in the past.

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.

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.