Heavy water processes

Fig. 1. Simplified flow diagrams for H2S/H2O heavy water processes, (a) Dual-temperature system where the pressure is 1.90 MPa (b) siagle-temperature...

Rae, H.K. "Selecting Heavy Water Processes" ACS Symposium Series No. 68, Separation of Hydrogen Isotopes, H.K. Rae (Editor). American Chemical Society, Washington, 1978... 

Problems that are common to all heavy water processes are a very dilute feed, a large overall concentration ratio, and low recovery. Thus, irrespective of process, the ratio of feed to product is 8000 1 for 100% and 40,000 1 for 20% recovery. 

Figure 13.40 Material flow sheet for first stage of Sulzer dual-temperature methylamine-hydrogen exchange heavy-water process. [AT] = deuterium content of hydrogen relative to natural water containing 135 ppm. Flow quantities, kg-mol/h.

Rae, H. K. Selecting Heavy Water Processes, paper presented at Joint Canadian Institute of Chemistry and American Chemical Society Meeting, Montreal, May 31, 1977. Rafn, I., Norsk Hydro Co. Personal communication to M. Benedict, Dec. 1976. 

In many respects, the case history presented by D. W. Jones and J. B. Jones of the DuPont Company is typical, They reported studies conducted on a pair of columns in use at Dana, Indiana, and Savannah River, Georgia, for a heavy-water process using dual temperature exchange of deuterium between water and hydrogen sulfide at elevated pressures. 

Heavy-water production in Canada began on a small scale in a plant operated by Cominco for the United States Atomic Energy Commission (USAEC) in 1944 (14) and continued until 1956. This was also a period of initial research into heavy-water processes at CRNL (15). By the mid-1950 s the USAEC and the E. I. Dupont de Nemours and Company had put into operation two large, heavy-water plants using the GS process. The... 

There have been many assessments and comparisons of heavy-water processes in Canada during the past three decades (15, 31, 32, 33). Despite the wide range of alternatives studied, none that can ofier unlimited production are able to compete with the GS process—deuterium exchange between water and hydrogen sulfide—which was chosen by the US AEG for their large-scale production needs nearly 30 years ago (34). 

When the scope of this commitment became known in the mid-1950 s, further heavy-water process development in Canada was halted. Initial Canadian requirements for heavy water were purchased from the USAEC, and investment in a heavy-water industry was postponed until demand was large enough to provide an economic scale of operation. 

Rae, H. K. A Review of Heavy Water Processes, Atomic Energy of Canada Limited Report, AECL-2503, 1965. 

Wynn, N. P. Lockerby, W. E. Heavy Water Processes Using Amine-Hydrogen Exchange, Annual International Conference of the Canadian Nuclear Association, 18th, 1978. 

Foaming is commonly experienced in the "cold (90 to 100°F) hydrogen sulfide-water contactors of the (jS (girdler-sulfide) heavy water process (132,182). This foaming is promoted by a high content of suspended solids in the feed water, is sensitive to this solids content. 

Heavy Water Process Takes a Big First Step, Chemical Week 33, October 5, 1957. 

One of the most significant sources of change in isotope ratios is caused by the small mass differences between isotopes and their effects on the physical properties of elements and compounds. For example, ordinary water (mostly Ej O) has a lower density, lower boiling point, and higher vapor pressure than does heavy water (mostly H2 0). Other major changes can occur through exchange processes. Such physical and kinetic differences lead to natural local fractionation of isotopes. Artificial fractionation (enrichment or depletion) of uranium isotopes is the basis for construction of atomic bombs, nuclear power reactors, and depleted uranium weapons. 

DifficultSepa.ra.tions, Difficult separations, characterized by separation factors in the range 0.95 to 1.05, are frequentiy expensive because these involve high operating costs. Such processes can be made economically feasible by reducing the solvent recovery load (260) this approach is effective, for example, in the separation of m- and -cresol, Hnoleic and abietic components of tall oil (qv), and the production of heavy water (see Deuteriumand TRITIUM, deuterium). 

In the spring of 1989, it was announced that electrochemists at the University of Utah had produced a sustained nuclear fusion reaction at room temperature, using simple equipment available in any high school laboratory. The process, referred to as cold fusion, consists of loading deuterium into pieces of palladium metal by electrolysis of heavy water, E)20, thereby developing a sufficiently large density of deuterium nuclei in the metal lattice to cause fusion between these nuclei to occur. These results have proven extremely difficult to confirm (20,21). Neutrons usually have not been detected in cold fusion experiments, so that the D-D fusion reaction familiar to nuclear physicists does not seem to be the explanation for the experimental results, which typically involve the release of heat and sometimes gamma rays. 

Herein reactors are described in their most prominent appHcation, that of electric power. Eive distinctly different reactors, ie, pressurized water reactors, boiling water reactors, heavy water reactors, graphite reactors, and fast breeder reactors, are emphasized. A variety of other appHcations and types of reactors also exist. Whereas space does not permit identification of all of the reactors that have been built over the years, each contributed experience of processes and knowledge about the performance of materials, components, and systems. 

The recognition in 1940 that deuterium as heavy water [7789-20-0] has nuclear properties that make it a highly desirable moderator and coolant for nuclear reactors (qv) (8,9) fueled by uranium (qv) of natural isotopic composition stimulated the development of industrial processes for the manufacture of heavy water. Between 1940 and 1945 four heavy water production plants were operated by the United States Government, one in Canada at Trail,... 

In the heavy-water plants constmcted at Savannah River and at Dana, these considerations led to designs in which the relatively economical GS process was used to concentrate the deuterium content of natural water to about 15 mol %. Vacuum distillation of water was selected (because there is Httle likelihood of product loss) for the additional concentration of the GS product from 15 to 90% D2O, and an electrolytic process was used to produce the final reactor-grade concentrate of 99.75% D2O. 

Heavy water [11105-15-0] 1 2 produced by a combination of electrolysis and catalytic exchange reactions. Some nuclear reactors (qv) require heavy water as a moderator of neutrons. Plants for the production of heavy water were built by the U.S. government during World War II. These plants, located at Trad, British Columbia, Morgantown, West Virginia, and Savaimah River, South Carolina, have been shut down except for a portion of the Savaimah River plant, which produces heavy water by a three-stage process (see Deuterium and tritium) an H2S/H2O exchange process produces 15% D2O a vacuum distillation increases the concentration to 90% D2O an electrolysis system produces 99.75% D2O (58). 

The facilities at Savannah River(j)) consist of five heavy-water-moderated and cooled production reactors, two chemical separations areas as a heavy water extraction plant, several test reactors, reactor fuel and target processing facilities, the Savannah River Laboratory, and many other facilities necessary to support the operations. During the 1960 s, two of the... 

A process involving water electrolysis is the production of heavy water. During cathodic polarization the relative rates of deuterium discharge and evolution are lower than those of the normal hydrogen isotope. Hence, during electrolysis the solution is enriched in heavy water. When the process is performed repeatedly, water with a D2O content of up to 99.7% can be produced. Electrochemical methods are also used widely in the manufacture of a variety of other inorganic and organic substances. 

The very low D/H natural abundance ratio (0.015% = 150 ppm) is responsible for the high cost of heavy water. Materials balance requires a minimum of 7x 103 mol feed per mol of product, and that increases even more for reasonable values of tails analysis (in some plants the feed/product ratio has reached nearly 4 x 104). At peak Canadian production, 800t year-1, this amounted to feeds of 3 x 107t year-1. Clearly that figure demands a cheap and easily accessible feed (i.e. water), or alternatively, requires deuterium production to be parasitic on some large industrial process, for example the production of NH3 for fertilizer, or petrochemical processing. 

Table 8.4 Possible processes for heavy water production (Rae, H. K., Ed., Separation of hydrogen isotopes, ACS Symp. Ser. 68, 134 (1978)) ...

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