Study of californium borate could lead to new technologies for radioactive waste storage and nuclear fuel recycling
The element californium (Cf, atomic number 98) is the heaviest element existing on Earth. Scientists have thought that Cf chemistry was dominated by ionic interactions. Now, a large scale, international study led by Florida State University Professor Thomas Albrecht-Schmitt has shown that Californium can bond covalently to borate. The new study of the synthetic, structural, spectroscopic and quantum chemical properties of a californium borate found that the element has “amazing” abilities to bond and separate other materials, and that it is extremely resistant to radiation damage. Albrecht-Schmitt said that the discoveries could help scientists build new storage containers for radioactive waste, plus help separate radioactive fuel, aiding in its recycling.
A paper on the study is published in the journal Nature Chemistry.
Currently, californium is the heaviest element that exists on Earth, and is the last member of the actinide series with an isotope long-lived enough for work to be carried out in a standard radiological facility. Typically, synthetic studies on californium chemistry have been restricted to microgram scales, and detailed measurements that correlate structure and physicochemical properties are lacking. The limited number of examples of californium compounds can be ascribed to a variety of factors, which include the low isotopic availability of this element, the short half-life of the longest-lived available isotope (Cf=351 years), and its extreme α and γ emissions (6.194 MeV and 0.388 MeV, respectively).—Polinski et al.
After years of working with the US Department of Energy, Albrecht-Schmitt obtained 5 milligrams of californium costing $1.4 million, paid for through an endowment to the university in honor of retired professor Gregory Choppin.
All of the experiments were conducted at Florida State, but Albrecht-Schmitt also worked with theorists and scientists from nine universities and institutes, including Oak Ridge National Laboratory, which supplied the californium.
David A. Dixon, professor of chemistry at the University of Alabama, and his graduate student, Ted Garner, provided the calculations and theory on why the californium could bond in such unique ways, while scientists at Argonne National Laboratory helped correlate the theory with the experiments. Evgeny Alekseev and Wulf Depmeier of Germany also provided an improved understanding on the atomic structure of californium.
Matthew J. Polinski, Edward B. Garner, Rémi Maurice, Nora Planas, Jared T. Stritzinger, T. Gannon Parker, Justin N. Cross, Thomas D. Green, Evgeny V. Alekseev, Shelley M. Van Cleve, Wulf Depmeier, Laura Gagliardi, Michael Shatruk, Kenneth L. Knappenberger, Guokui Liu, S. Skanthakumar, Lynda Soderholm, David A. Dixon & Thomas E. Albrecht-Schmitt (2014) “Unusual structure, bonding and properties in a californium borate,” Nature Chemistry doi: 10.1038/nchem.1896
“Californium compound springs bonding surprise,” Anthony King, Chemistry World, 23 March 2014