Assessment of the release behaviour of 14C from irradiated nuclear graphite from a German research reactor

The behaviour of irradiated graphite (i-graphite) from a German research reactor was investigated under different boundary conditions for assessment of 14C-speciation and the release kinetics into the aqueous and gas phase. The results showed that most of released 14C remains in the solution. Under near neutral conditions, volatile 14C is predominantly in form of CO2 (i.e. 90%) with some minor fraction of 14CO + 14Corg. Almost negligible 14C release into the gas phase was detected under cementitious conditions, although the total 14C release increases. Evaluated release rates of 14C are discussed in the context of i-graphite disposal in the GDF Schacht Konrad