Girdler sulfide process
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The Girdler sulfide (GS) process, also known as the Geib-Spevack (GS) process,[1] is an industrial production method for making heavy water (deuterium oxide), an important component of many nuclear reactors 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 less than 200 parts per million of deuterium. [2]
The Bruce Heavy Water Plant in Ontario 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. It is located closely to the Bruce Nuclear Generating Station.
[edit] 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. Deuterium 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. 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.
Normally in this process, water is enriched to 15% to 20% deuterium. Further enrichment to "reactor-grade" heavy water (>99% deuterium) is done in a vacuum distillation unit. [3]
[edit] References
- ^ U.S. Patent 4620909 , Method for isotope replenishment in an exchange liquid used in a laser induced isotope enrichment process
- ^ Federation of American Scientists, Heavy Water Production, accessed 1 Feb 2007.
- ^ Boris M. Andreev (2001). "Separating of Hydrogen Isotopes in H2O-H2S System". Separation Science and Technology 36 (8-9): 1949 - 1989. DOI:10.1081/SS-100104764.
