Determination of ultra-low concentrations of gaseous C-bearing hydrocarbons produced during corrosion of irradiated steel using accelerator mass spectrometry

Compound-specific radiocarbon analysis (CSRA) was developed to identify and quantify gaseous 14 C-bearing carbon compounds at the pico- to femtomolar concentration range and employed in a corrosion experiment with small specimens of irradiated steel. The approach is based on gas chromatographic separation of single 14 C-bearing carbon compounds, their oxidation to 14 CO 2 , sampling with a custom-made fraction collector and quantification by accelerator mass spectrometry (AMS). In addition to CSRA, a method allowing the quantification of the total 14 C content of the gas phase was developed and tested. After validation of the two set-ups with standards, the gaseous 14 C-bearing carbon compounds produced during alkaline anoxic corrosion of irradiated steel were quantified. Small hydrocarbons (HCs) like methane ( 14 CH 4 ) and ethane ( 14 C 2 H 6 ) were the only 14 C-bearing compounds identified in the gas phase above the detection limit. 14 CH 4 was the main species (on average 5.4 × 10 −14 mol L −1 gas) and contributed >90% to the total 14 C content, whereas the concentration of 14 C 2 H 6 was much lower (7.9 × 10 −16 mol L −1 gas). To our knowledge, this is the first study reporting CSRA of gaseous 14 C-bearing HCs produced during anoxic corrosion of irradiated metallic radioactive waste at ultra-low concentrations. Compound specific radiocarbon analysis, based on gas chromatography and accelerator mass spectrometry, was developed to quantify gaseous 14 C species released at pico- to femtomolar concentrations during alkaline anoxic corrosion of irradiated steel.