Girdler sulfide process
Encyclopedia
The Girdler sulfide process, also known as the Geib–Spevack (GS) process, is an industrial production method for making heavy water
(deuterium
oxide), an important component of many nuclear reactor
s because it acts as a neutron moderator
. It takes its name from Karl-Hermann Geib and Jerome S. Spevack, who independently invented it in the early 1940s, or the Girdler company, which built the first American plant using the process.
The method is an isotopic
exchange process between H2S
and H2O ("light" water), that produces heavy water over several steps. It is a highly energy intensive process. Normal water contains 115 parts per million of deuterium, relative to hydrogen.
Until its closure in 1997, the Bruce Heavy Water Plant in Ontario
(located close to the Bruce Nuclear Generating Station
) was the world's largest heavy water production plant, with a capacity of 700 tonnes per year. 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.
Presently, India has seven heavy water production plants. The first of these to use the Girdler process is located at Rawatbhata near Kota, Rajasthan.
extraction is done based on the difference in separation between 30 °C and 130 °C.
Hydrogen sulfide
gas is circulated in a closed loop between the cold tower and the hot tower (although these can be separate towers, they can also be separate sections of one tower, with the cold section at the top). Demineralised
and deaerated
water is fed to the cold tower where deuterium migration preferentially takes place from the hydrogen sulfide gas to the liquid water. This "enriched" water from the cold tower is fed to the hot tower where deuterium transfer takes place from the liquid water to the hydrogen sulfide gas. An appropriate "cascade" setup accomplishes enrichment. Using one tower instead of a cascade is possible, but in practice it never occurs, as the tower size and process inventory would be much larger.
Normally in this process, water is enriched to 15–20% deuterium. Further enrichment to "reactor-grade" heavy water (> 99% deuterium) is done in a vacuum distillation
unit.
Heavy water
Heavy water is water highly enriched in the hydrogen isotope deuterium; e.g., heavy water used in CANDU reactors is 99.75% enriched by hydrogen atom-fraction...
(deuterium
Deuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
oxide), an important component of many nuclear reactor
Nuclear reactor
A nuclear reactor is a device to initiate and control a sustained nuclear chain reaction. Most commonly they are used for generating electricity and for the propulsion of ships. Usually heat from nuclear fission is passed to a working fluid , which runs through turbines that power either ship's...
s because it acts as a neutron moderator
Neutron moderator
In nuclear engineering, a neutron moderator is a medium that reduces the speed of fast neutrons, thereby turning them into thermal neutrons capable of sustaining a nuclear chain reaction involving uranium-235....
. It takes its name from Karl-Hermann Geib and Jerome S. Spevack, who independently invented it in the early 1940s, or the Girdler company, which built the first American plant using the process.
The method is an isotopic
Isotope
Isotopes are variants of atoms of a particular chemical element, which have differing numbers of neutrons. Atoms of a particular element by definition must contain the same number of protons but may have a distinct number of neutrons which differs from atom to atom, without changing the designation...
exchange process between H2S
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
and H2O ("light" water), that produces heavy water over several steps. It is a highly energy intensive process. Normal water contains 115 parts per million of deuterium, relative to hydrogen.
Until its closure in 1997, the Bruce Heavy Water Plant in Ontario
Ontario
Ontario is a province of Canada, located in east-central Canada. It is Canada's most populous province and second largest in total area. It is home to the nation's most populous city, Toronto, and the nation's capital, Ottawa....
(located close to the Bruce Nuclear Generating Station
Bruce Nuclear Generating Station
Bruce Nuclear Generating Station is a Canadian nuclear power station located on the eastern shore of Lake Huron, in the communities of Inverhuron and Tiverton, Ontario. It occupies 932 ha of land. The facility derives its name from Bruce County in which it is located, in the former Bruce Township...
) was the world's largest heavy water production plant, with a capacity of 700 tonnes per year. 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.
Presently, India has seven heavy water production plants. The first of these to use the Girdler process is located at Rawatbhata near Kota, Rajasthan.
The process
Each of a number of steps consists of two sieve tray columns. One column is maintained at 30 °C and is called the cold tower and the other at 130 °C and is called the hot tower. DeuteriumDeuterium
Deuterium, also called heavy hydrogen, is one of two stable isotopes of hydrogen. It has a natural abundance in Earth's oceans of about one atom in of hydrogen . Deuterium accounts for approximately 0.0156% of all naturally occurring hydrogen in Earth's oceans, while the most common isotope ...
extraction is done based on the difference in separation between 30 °C and 130 °C.
Hydrogen sulfide
Hydrogen sulfide
Hydrogen sulfide is the chemical compound with the formula . It is a colorless, very poisonous, flammable gas with the characteristic foul odor of expired eggs perceptible at concentrations as low as 0.00047 parts per million...
gas is circulated in a closed loop between the cold tower and the hot tower (although these can be separate towers, they can also be separate sections of one tower, with the cold section at the top). Demineralised
Water purification
Water purification is the process of removing undesirable chemicals, materials, and biological contaminants from contaminated water. The goal is to produce water fit for a specific purpose...
and deaerated
Deaeration
Deaeration is the removal of air molecules from another gas or liquid. It can refer to:*Use of a deaerator.*Degasification, the removal of dissolved gases, such as oxygen, from liquids....
water is fed to the cold tower where deuterium migration preferentially takes place from the hydrogen sulfide gas to the liquid water. This "enriched" water from the cold tower is fed to the hot tower where deuterium transfer takes place from the liquid water to the hydrogen sulfide gas. An appropriate "cascade" setup accomplishes enrichment. Using one tower instead of a cascade is possible, but in practice it never occurs, as the tower size and process inventory would be much larger.
Normally in this process, water is enriched to 15–20% deuterium. Further enrichment to "reactor-grade" heavy water (> 99% deuterium) is done in a vacuum distillation
Vacuum distillation
Vacuum distillation is a method of distillation whereby the pressure above the liquid mixture to be distilled is reduced to less than its vapor pressure causing evaporation of the most volatile liquid...
unit.