New equation of state as international standard to describe thermodynamics of heavy water
New equation of state as international standard to describe thermodynamics of heavy water lead image
Heavy water is a term used to describe water where the hydrogen nuclei have an additional neutron, increasing the mass density and altering its thermophysical properties. Heavy water is used primarily in applications for certain types of nuclear reactors because it absorbs many fewer neutrons relative to ordinary water. However, the previous standard equation of state describing the properties of heavy water is nearly 40 years old and does not reflect current experimental knowledge or modern equation-of-state techniques.
Herrig et al. from the Ruhr-Universität Bochum (RUB) and the National Institute of Standards and Technology (NIST) have developed a new equation of state for heavy water with greater accuracy, lower uncertainties and a wider range of applicability compared to its predecessor. This new equation of state is being adopted as an international standard and will be implemented in the standard thermophysical property software packages made available through NIST and RUB.
Examples of equations of state, which describe a given substance’s thermodynamic properties, include the well-known ideal gas law and so-called steam tables that engineers use for ordinary water. It is essential to have high confidence in these properties when designing processes that use heavy water, especially for nuclear energy applications. The main difference in the equations of state between ordinary and heavy water is that heavy water has increased hydrogen bonding between the water molecules when in condensed phases, requiring higher temperatures or lower pressures to evaporate or become steam.
The development of this new equation of state ensures high fidelity knowledge of the behavior of heavy water for applications throughout the world.
Source: “A Reference Equation of State for Heavy Water,” by Stefan Herrig, Monika Thol, Allan H. Harvey, and Eric W. Lemmon, Journal of Physical and Chemical Reference Data (2018). The article can be accessed at https://doi.org/10.1063/1.5053993 .
This work was supported by the International Association for the Properties and Water and Steam (IAPWS, www.iapws.org )
