perly stored, it can leach into the environment.
Many researchers, like those on the Notre Dame team, believe one solution to effective, efficient, and safe nuclear power lies in the reprocessing of spent nuclear fuel. In 2005 Burns and his research group published the first information on a family of novel uranyl peroxide hydroxide spherical nanoclusters — actinides — that they have continued to explore. Most recently, funded by the Office of Basic Energy Sciences of the U.S. Department of Energy, they have demonstrated that these species can be separated from aqueous solutions, such as those created dissolving spent fuel from nuclear power plants.
What the team has found is that uranyl peroxide nanocluster species are composed of collections of four-, five-, or six-membered rings of uranium polyhedra. These spherical cage clusters feature diameters up to four nanometers. The cluster properties of the species suggest that they could then be removed from solutions using a variety of separation processes, selective-size ultrafiltration. Using a series of three commercial ultrafiltration membranes, the team successfully separated the uranium species from the waste stream for purification and to concentrate and collect the purified uranium product for further processing.
After encouraging the development of uranyl peroxide clusters in untreated samples, the waste solution is then sieved through a series of membranes (ultrafiltration) so that the clusters can be separated from the solution. Chemical and spectroscopic analyses confirm the efficiency of the filtration process. This is also visible in the noticeable color change of the solution.
The results of their work suggest that the assembly of the cluster species they encouraged accounts for nearly all of the uranium in the test solution, with no evidence of uranium species being absorbed by the membranes used as filters. Furthermore, their work implies that it may be possible to design an ultrafiltration to recover the uranium from the solution by exploiting the difference in size between the uranyl peroxide clusters and other solutes in a solution. It also begins to identify the characteristics necessary for more specific membranes, rather than the three commercially available membranes with different pore sizes used in this study. As the team continues to work, the data will assist in the design and synthesis of new membrane materials designed specifically for safe and effective processing of nuclear waste.