Quantification of dissolved organic 14C-containing compounds by accelerator mass spectrometry in a corrosion experiment with irradiated steel

Low- and intermediate-level (L/ILW) radioactive waste produced in Switzerland consists of large amounts of C-14-containing irradiated steel. C-14 will be released during the anoxic corrosion of the steel in the cementitious near field of an L/ILW repository. In this study, a corrosion experiment with irradiated steel was carried out to determine the speciation of C-14 released during the corrosion process in conditions similar to those anticipated in the near field of a cement-based repository. The development of the experimental setup, including installation of the reactor and development of suitable analytical methods based on compound-specific C-14 analysis with accelerator mass spectrometry (CSRA AMS) is reported. Time-dependent increase in the total content of C-14-bearing organic compounds in solution ((TOC)-C-14) was determined by AMS and the main organic corrosion products that are C-14-bearing formate, acetate and lactate were identified by CSRA AMS after a pre-concentration step. The concentration of the C-14-bearing organic compounds was found to be very low (fmol to pmol C-14/L). Stable carbon compounds were identified and quantified while the source of stable carbon in the system has not yet been identified and the temporal evolution of the concentration of these carbon species is presently not understood.