Various ion exchange materials have been proposed for the removal of Cs from
high level waste streams produced during the reprocessing of fuel rods. Cs
can be released from loaded traditional exchange resins by elution and then
the resin can be reused. However large quantities of secondary wastes are
generated. Another class of “single use” exchangers is directly incorporated
in the loaded state into a solid waste form (e.g. borosilicate glass logs).
A third alternative is electroactive ion-exchange materials, where the
uptake and elution of Cs are controlled by an applied potential. This
approach has several advantages over traditional reusable ion-exchange
resins including much reduced secondary waste, higher Cs selectivity, and
higher durability.
XAS experiments were conducted at the Fe K-edge and Cs Lm-edge on
a series of electrochemically produced nickel ferrocyanide films to
determine the effects of deposition conditions and subsequent alkali
exchange on structural and chemical aspects of the films. The deposition
conditions include methods described in the literature and PNNL proprietary
procedures. Although the performance and the durability of the films do vary
with processing conditions, Fe K-edge EXAFS results indicate that all
deposition conditions result in the. formation of the cubic phase. Initial
results from Cs Lm-edge EXAFS analysis suggest that the Cs ion is
present as a hydrated species.