Fig. 4-13 Crystal structure of the new ceramic waste form (yttriastabilized zirconia) The new ceramic forms include TRU elements in the crystal lattice and show good crystallographic phase stability and excellent chemical durability in ground water.

Fig. 4-14 Chemical durability of the new ceramic waste form This figure shows the chemical durability of the new ceramic waste form is remarkably more resistant to harsh conditions than glass waste forms and SYNROC waste forms that have been studied and developed.

Many TRU elements produced in nuclear reactors have long half-lives and high toxicities. Hence, waste containing highly concentrated TRU elements should be immobilized in crystallographically stable and chemically durable forms. These waste forms should be placed in a repository for long-term disposal. New ceramic waste forms (matrix; zirconia and/or alumina) that contain TRU elements stably are being developed in cooperation with Osaka University. These new ceramic waste forms incorporate Ce and/or Nd, which are similar chemically to TRU elements. Their crystallographic phase stability and chemical durability are being investigated. The results to date reveal the new ceramic waste form can contain Ce and/or Nd over a wide range and is stable crystallographically and durable chemically. This form is remarkably more durable than glass waste forms and SYNROC waste forms, as shown in the figure. It is supposed that the new waste form with the improved properties (chemical durability) will decrease the cost of a repository, reduce the multi-barrier system qualitatively and quantitatively, and reduce the treatment of the highly concentrated TRU waste.

Reference K. Kuramoto et al., Development of Zirconia-and Alumina-based Ceramic Waste Forms for High Concentrated TRU Elements, International Conference on Evaliation of Emerging Nuclear Fuel Cycle Systems, Sep. 11-14, 1995, Versailles, France, p.1838.

Select a topic in left column