(GRS-587) Stability of Iron Corrosion Phases expected in a Repository in Lower Cretaceous Clay

S. Hagemann, H. Mönig

Iron-containing materials from the containers represent the most important source of redox-sensitive chemical elements in the near field. It is therefore assumed that the redox potential is primarily driven by the iron phases, notably iron corrosion phases that are present /JOB 97/, /WER 03/.

For repository concepts in argillaceous rock, an influx of pore waters to the emplaced waste containers is to be expected for all system developments to be considered within the framework of a long-term safety assessment. In the case of clay formations in northern Germany which are considered for the construction of a repository for heat-generat-ing radioactive waste, saline pore waters are also to be assumed.

The inflowing solutions lead to progressive corrosion of the containers, which eventually can lead to a loss of its barrier function and the mobilisation of radionuclides into the near-field system. There, the radionuclides released from the waste matrix encounter a geochemical environment that is strongly determined by the corrosion of the metallic components in the nearfield (e. g. containers, liners). Although it is based on the geo-chemical conditions in the host rock formation, it is decisively influenced locally by the solid, dissolved, and gaseous corrosion products.