Halides can be retained in bellows hot-pressed Synroc-C. Loadings of 0.2 wt% of fluoride or 2 wt% of sulphate did not appear to exert deleterious effects on the aqueous durability of the Synroc, but 0.2 wt% of chloride or 0.5 wt% of fluoride increased the Cs leach rate by a factor of ˜10. Fluoride was present principally as CaF2 in both calcined and hot-pressed Synrocs containing (a) ˜2 wt% of F as the only waste or (b) ˜2 wt% of F plus 20 wt% of simulated PW-4b Purex reprocessing waste. The speciation of Cl- in Synroc is not clear, though there was some evidence of CsCl from nmr and a compound giving a similar X-ray pattern to that of TiCI3. Iodine can retained in the hot-pressed Synroc containing the full complement of fission products, probably as insoluble Ag, Cr or Pd group iodides.
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