Synroc containing 20 wt% simulated high level waste (HLW) was subjected to
two sets of leach tests at 150°C where the leachant was and was not replaced
during the test (replacement and non-replacement testing). The leachant was
a KH-phthalate buffered solution (pH 4.2). Samples were characterised before
and after leach testing using SEM, AEM and SIMS. Elemental concentrations in
leachates were measured using ICP-MS. In concert with the findings of i) a
dissolution study of perovskite in a flowing leachant and ii) a previous
Synroc dissolution study (wherein Synroc containing 10 wt% simulated HLW was
subjected to periodic replacement, leach testing in deionised water at
150°C), the results of this study show that when the leachant replacement
frequency is varied from 7 d to the duration of the test, there is no effect
on leach rate or leaching mechanisms.