Heavy water properties

Dave, S.M. Sadhukhan H.K. Novaro, O.A. Heavy Water—Properties, Production and Analysis, Quest Publications Mumbai, 1997. 

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. 

Thermodynamic Properties. Ordinary water contains three isotopes of hydrogen [1333-74-0] (qv), ie, H, H, and H, and three of oxygen [7782 4-7] (qv), ie, O, and The bulk of water is composed of and O. Tritium [15086-10-9] H, and are present only in extremely minute concentrations, but there is about 200-ppm deuterium [16873-17-9], H, and 1000-ppm in water and steam (see Deuterium and tritium). The thermodynamic properties of heavy water are subtly different from those of ordinary water. lAPWS has special formulations for heavy water. The properties given herein are for ordinary water having the usual mix of isotopes. 

H. Mandel, Heavy Water Organic Cooled Keactor, Physical Properties of Some Polyphenyl Coolants, A EC Report A l-CE-15, Apr. 15, 1966. 

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,... 

Properties of Light and Heavy Water. Selected physical properties of light and heavy water are Hsted ia Table 3 (17). Thermodynamic properties are given ia Table 4. The Hquid plus vapor critical-temperature curve for xT) (1 )H2 ) mixtures over the entire concentration range has been reported (28). 

Table 3. Physical Properties of Light and Heavy Water...

The only large-scale use of deuterium in industry is as a moderator, in the form of D2O, for nuclear reactors. Because of its favorable slowing-down properties and its small capture cross section for neutrons, deuterium moderation permits the use of uranium containing the natural abundance of uranium-235, thus avoiding an isotope enrichment step in the preparation of reactor fuel. Heavy water-moderated thermal neutron reactors fueled with uranium-233 and surrounded with a natural thorium blanket offer the prospect of successful fuel breeding, ie, production of greater amounts of (by neutron capture in thorium) than are consumed by nuclear fission in the operation of the reactor. The advantages of heavy water-moderated reactors are difficult to assess. 

L Khschenbaum, Physical Properties and Analysis of Heavy Water, McGraw-HiU Book Co., Inc., New York, 1951, p. 54. 

Water is a volatile, mobile liquid with many curious properties, most of which can be ascribed to extensive H bonding (p. 52). In the gas phase the H2O molecule has a bond angle of 104.5° (close to tetrahedral) and an interatomic distance of 95.7 pm. The dipole moment is 1.84 D. Some properties of liquid water are summarized in Table 14.8 together with those of heavy water... 

Moderators. Neutrons are most effectively slowed by collisions with nuclei of about the same mass. Thus the best moderators are those light atoms which do not capture neutrons. These are H, " He, Be and C. Of these He, being a gas, is insufficiently dense and Be is expensive and toxic, so the common moderators are highly purified graphite or the more expensive heavy water. In spite of its neutron-absorbing properties, which as mentioned above must be offset by using enriched fuel, ordinary water is also used because of its cheapness and excellent neutronmoderating ability. 

In the light water reactor, the circulating water serves another purpose in addition to heat transfer. It acts to slow down, or moderate, the neutrons given off by fission. This is necessary if the chain reaction is to continue fast neutrons are not readily absorbed by U-235. Reactors in Canada use heavy water, D20, which has an important advantage over H20. Its moderating properties are such that naturally occurring uranium can be used as a fuel enrichment in U-235 is not necessary. 

Coolant property (D20 and HzO) effects on CHF. Fluid property effects here refer to fluids of heavy water versus light water as used in water-cooled reactors. For other fluids, readers are referred to Section 5.3.4. These effects were taken... 

Sit, P. Marzari, N., Static and dynamical properties of heavy water at ambient conditions from first-principles molecular dynamics, Los Alamos Eprint Server 2005. cond-mat/0504146... 

Deuterium, 8 456—485 13 759. See also Canadian Deuterium Uranium (CANDU) reactors analytical methods, 8 467-468 economic aspects, 8 467 health and safety factors, 8 461-462 physical properties, 8 457-462, 459t production of heavy water, 8 459t, 462-467... 

The title indicates the scope of the text. The term isotope effects is used rather than applications of isotopes to indicate clearly that it deals with differences in the properties of isotopically substituted molecules, for example differences in the chemical and physical properties of water and the heavy waters (H2O, HDO, D2O, HTO, etc.). Thus H20, HDO and D2O have different thermodynamic properties. Also reactions in solvent mixtures of light and heavy water proceed at different rates than they do in pure H2O. On the other hand, the differences are not large and consequently, to the extent the difference in properties can be ignored, HDO or HTO can be used as tracers for H2O. An important point, however, is that this book does not deal with isotopes as tracers in spite of the widespread importance of tracer studies, particularly in the bio and medical sciences. Also the title specifically does not mention physics which would necessarily have been included if the term Physical Sciences had been used. Thus the text does not deal with differences in the nuclear properties of isotopic atoms. Such differences are in the realm of nuclear physics and will not be discussed. 

It has been shown that the interpretation of catalytic reactions involving group VIII transition metals in terms of n complex adsorption possesses considerable advantages over classical theories by providing a link between theoretical parameters and chemical properties of aromatic reagents and catalysts. The concept has led to the formulation of a number of reaction mechanisms. In heavy water exchange the dissociative tt complex substitution mechanism appears to predominate it could also play a major role when deuterium gas is used as the second reagent. The dissociative mechanism resolves the main difficulties of the classical associative and dissociative theories, in particular the occurrence... 

Table 3.11 Comparison of the properties of light and heavy water (DIPPR 1997 Marcus 1985)...

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