Experimental findings of full-scale leach tests performed on simulated ceme
nted waste forms and self-shielded concrete waste containers for periods up
to 19 yr in saturated salt brines (NaCl- and Q-brine) are presented. Measu
rements cover the evolution of leachant composition and the release of radi
onuclides such as Cs, U, and Np. Performance of the waste forms and the sel
f-shielded concrete waste containers depends on the pore volume of the hard
ened cement/concrete, which is correlated to the water/cement ratio of the
waste forms. Cesium release follows a linear time dependence. Samples, espe
cially those having a high pore volume, show almost complete release of Cs
in. the period of investigation. Uranium release is independent of the leac
h period. Uranium concentrations are controlled by thermodynamic equilibriu
m Neptunium is released only to a small extent; concentrations are close to
the detection limit.
Modeling of the cement corrosion progress allows the prediction of the evol
ution of the brines in terms of pH, calcium concentration, etc. and the ide
ntification of solids controlling the solubilities of the main components a
nd of uranium.