Important thermodynamic analyses of possible reactions affecting the long-term performance of the engineered materials being considered for isolation of high-level waste are reviewed. Analysis of the literature on the possible failure mechanisms of copper waste packages in granite and basalt environments shows that many of the conclusions from postulated thermodynamic equilibria reactions are inconsistent with the original assumptions and with observations. The absence of evidence for the existence of reactions calculated to have negative free energy changes is classically explained by kinetic inhibitions. We suggest reasons why some of these reactions should be treated as thermodynamic artifacts rather than slowly occurring natural reactions.