Treatment and immobilization

As has been shown in Section 25.2, defence wastes can have an extremely large compositional range, varying from pure metal (i. e., Pu or HEU) through well-defined chemical compounds (e. g., oxides), to the liquid and semi-solid HLW tank wastes found at various separation facilities. Any treatment process must ensure that the ultimate waste form is intrinsically (passively) safe, leach resistant, chemically stable and radiation resistant. The chosen process must also be sufficiently flexible in order to deal with the compositional variability within a waste stream and more significant variations between different varieties of waste stream.

During the Cold War period, the two major protagonists, US and Russia, operated two different philosophies on the value of plutonium which had a significant impact on the inventories of Pu-contaminated wastes and resi­dues requiring disposal (Jardine et al., 1999). Whereas US policy was to establish a Pu concentration for the various wastes and residues below which it was considered more economical to produce new metal (economic discard limit, EDL), Russian policy was to recover all Pu above a concentra­tion of 200 ppm for re-use. To implement this philosophy extensive recovery processes were installed at the Pu production facilities of Mayak, Tomsk and Krasnoyarsk.

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