THE SOLUBILITY OF TECHNETIUM IN THE NEAR-FIELD ENVIRONMENT OF A RADIOACTIVE-WASTE REPOSITORY

Experimental measurements of the solubility of technetium under conditions similar to those expected to be found in the near-field environment of a radioactive waste repository have been carried out. The measured solubility of technetium under high pH and reducing conditions in contact with hydrated technetium dioxide has been found to be about 10-7 mol dm-3 and is independent of pH in the range 8-13 and the type of cement-equilibrated water used. The measured solubility was insensitive to the solid-liquid separation method used, suggesting that signficant quantities of technetium-containing colloidal species are not present. A limited investigation of the effects of organic decomposition products on the solution concentration of reduced technetium has shown that there is a modest enhancement in technetium solubility. © 1990.