CORROSION OF HIGH-LEVEL WASTE PACKAGING MATERIALS IN DISPOSAL RELEVANT BRINES

Previous corrosion studies identified the materials Hastelloy C4, Ti99 .8-Pd, and carbon steels as promising for the manufacture of long-live d high-level waste containers that could act as an engineered barrier in a rock-salt repository. Here, the efficiency of the corrosion-resis tant concept using surface-welded Hastelloy C4 as corrosion protection of carbon steel containers is compared with the corrosion-allowance c oncept using unalloyed or low-alloyed steels. The materials are examin ed in three disposal relevant brines (two rich in MgCl2, one rich in N aCl) at 150-degrees-C The results indicate that welded Hastelloy C4 is highly resistant to corrosion in the NaCl-rich brine. In the presence of sulfides or MgCl2-rich brines, however, severe pitting corrosion o ccurs. The three steels investigated are resistant to pitting corrosio n in all brines, and their general corrosion rates imply corrosion all owances acceptable for thick-walled containers. In view of these resul ts, carbon steels continue to be considered promising materials for lo ng-lived containers. Further investigations on carbon steels and Ti 99 .8-Pd as alternatives to Hastelloy C4 are in progress.