European Project “CArbon-14 Source Term” CAST - Deliverable D 4.5 - "Final report on the estimation of the source term and speciation"

The CAST project (CArbon-14 Source Term) aims to develop understanding of the potential release mechanisms of carbon-14 from radioactive waste materials under conditions relevant to waste packaging and disposal to underground geological disposal facilities. The project focuses on the release of carbon-14 as dissolved and gaseous species from irradiated metals (steels, Zircaloys), irradiated graphite and from ion-exchange materials. This report describes the final results of the CAST activities on the 14C inventory in the ionic exchange resins and their speciation and has the objective to combine the experiences of all the partners and to show the most significant results they achieve, leading to an improvement of the knowledge of the behaviour of the activated ionic exchange resins. The experimental data are presented, whenever possible, as aggregates in order to make a common picture of the 14C inventory and speciation in the resins used in the nuclear reactors. Available results on the speciation of 14C originated from SIERs – partition between inorganic (carbonate) and organic fractions – seem to show that the majority of the 14C activity comes from the inorganic part. However, results on the partition of inorganic and organic molecules are often contrasting, spanning between 5 and 20% under the form of organic molecules from PWRs and CANDU. The wide range of 14C inventory values shows that it is not possible to simply estimate the 14C source term for ionic exchange resins but a dedicated and accurate sampling and analysis programme has to be developed and executed.