Abstract
The technetium isotope 99Tc is a major fission product from nuclear reactors. Because 99Tc has few applications outside of scientific research, most of this technetium will ultimately be disposed of as nuclear waste. Geochemical modeling of the dissolution of nuclear waste, and of the solubility and speciation of the dissolved radionuclides in groundwaters, is an important part of the Performance Asssessment of the safety of a nuclear waste repository that relies on the availability of a critically-assessed thermodynamic database. Such a database for technetium was published in the book Chemical Thermodynamics of Technetium, covering the published literature through 1998. This database is described here, along with a discussion of more recent relevant studies. Gaps in the knowledge of the chemical and thermodynamic properties of technetium are identified here, and recommendations are made for measurements that are required to eliminate these gaps.
