Radiation damage in glasses and ceramics

No discussion of the relative attributes of glass, glass-ceramics, and ceramic/ mineral waste forms is complete without a discussion of the relative radiation stability of the various waste forms. The effects of radiation damage due to self-irradiation of various waste forms have been studied for decades and a few of the more recent reviews of this field are given in Section 6.9.2.

Radiation damage is not only important because it impacts the stability of the wasteform but if the material swells or is otherwise degraded by self­irradiation, this impacts the long-term durability of the waste form (see discussion in Section 6.8). While glasses undergo radiation damage that can cause density variations, careful durability experiments have shown that the radiation damage does not affect the dissolution rate as studied by single pass flow through (SPFT) and Soxhlet durability tests. Many pertinent examples are given in [4].

In ceramic/mineral waste forms, the crystalline structure may become amorphous, a phenomenon observed in nature and known as metamictiza — tion (the formation of amorphous metamict phases). This phase change, from a crystalline structure to a partially or completely amorphous struc­ture, is accompanied by macroscopic swelling of the structure. An interest­ing study by Weber et al. [166] has shown that the Synroc crystalline phases (zirconolite and perovskite) are susceptible to macroscopic swelling at high dosages (Fig. 6.6) . Moreover, the swelling in the titanium-based Synroc phases is greater than the swelling in the silicate-based supercalcine ceram­ics at lower dosages which in turn is greater than the swelling in glass ceramics (Fig. 6.6). Additional references regarding the swelling of indi­vidual mineral/ceramic phases can be found in the references in the anno­tated Tables 6.6 and 6.8 .

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6.6 Macroscopic swelling in Pu-doped Synroc, Cm-doped supercalcine, and Cm-doped and Pu-doped glass-ceramics. (Reprinted with permission from [166].

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