Girdler sulfide process
The Girdler sulfide (GS) process, also known as the Geib–Spevack (GS) process, is an industrial production method for extracting heavy water (deuterium oxide, D2O) from natural water. Heavy water is used in particle research, in deuterium NMR spectroscopy, deuterated solvents for proton NMR spectroscopy, heavy water nuclear reactors (as a coolant and moderator) and deuterated drugs.
In 1943, Karl-Hermann Geib and Jerome S. Spevack independently invented the process.The process is named after the Girdler Company, which constructed the first American plant to implement it.
The method is an isotopic exchange process, where isotopes of hydrogen are swapped between hydrogen sulfide (H2S) and water (H2O), also known as "light" water, that produces heavy water over several steps. This process is highly energy intensive.
Until its closure in 1997, the Bruce Heavy Water Plant in Ontario (located on the same site as Douglas Point and the Bruce Nuclear Generating Station) was the world's largest heavy water production plant, with a peak capacity of 1600 tonnes per year (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 by mass 340000 units of feed water to produce 1 unit of heavy water.
The first such facility of India's Heavy Water Board to use the Girdler process is at Rawatbhata near Kota, Rajasthan. This was followed by a larger plant at Manuguru, Andhra Pradesh. Other plants exist in the United States and Romania for example. Romania, India and the former supplier of much of the world's heavy water demand, Canada, all have operating heavy water reactors with two at Cernavoda Nuclear Power Plant in Romania making up the country's entire fleet and several each in India (mostly IPHWR) and Canada (exclusively CANDU).