CAST: CArbon-14 Source Term

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 in underground geological disposal facilities.

Overview

Project Dates: 1/10/2013 – 31/03/2018

Project Status: Ongoing

Project Website: www.projectcast.eu

In our atmosphere, carbon-14 is continuously generated from nitrogen (about 80% of air) and is incorporated into all living things.  When a species die, the incorporation of this cosmogenically generated carbon-14 stops and its content decreases by radioactive decay.  The degree of carbon-14 decay in material from once living things allows archaeologists to determine how old their findings of biological origin (e.g. a wooden tool) are.  Carbon-14 is also generated in nuclear reactors, for example, during irradiation of metals containing nitrogen or carbon additions.  These materials are considered radioactive waste for which special safety measures are and will be taken.  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 in underground geological disposal facilities.  The expected increase in understanding should decrease uncertainties in the long-term safety assessment and increase confidence in the safety case.

The CAST consortium brings together 33 partners with many different skills and competences both in geological disposal of difference waste types, but also in developing safety cases and on planning and implementing experimental programmes on gas generation.  The consortium includes national waste management organisations, research institutes, universities and commercial organisations working in this field.  The involvement of the waste management organisations (the end-users of the outcome in the form of process understanding, data and competence) ensures that the project is focused on important and outstanding issues.  It also ensures that the project is aligned to European national programmes and thus that results are used as intended.  Two partners are from outside Europe – one from the Ukraine (SI IEG NASU) and one from Japan (RWMC).  This offers a unique extension of scientific basis to the project, as well as an insight into how other national programmes manage the issue of carbon-14.

CAST is a collaborative project that has received funding from the European Union’s Seventh Framework Programme for research, technological development and demonstration.

Objective

The scope of CAST has been defined through a process of consultation initiated by a questionnaire circulated to a wide range of organisations.  A synthesis of the responses to the questionnaire showed that carbon-14 release from irradiated steels, Zircaloys, graphites and from ion-exchange resins were of widest interest.  The responses indicated that there were several on-going (or planned studies) on irradiated graphites and uncertainties on carbon-14 release rates and speciation remain to be resolved.  However, there was less on-going work and little information available for the release of carbon-14 from irradiated steels, Zircaloys and ion-exchange resins.

The objectives of CAST are to:

  1. gain a scientific understanding of the carbon-14 release mechanisms and rates from the corrosion of irradiated steels and Zircaloys and from the leaching of ion-exchange resins and irradiated graphites under geological disposal conditions;
  2. provide speciation of the carbon-14 release and how this relates to aqueous conditions;
  3. evaluate this understanding in the context of national safety assessments; and
  4. disseminate this understanding and its relevance to safety assessments to a range of interested stakeholders and provide an opportunity for training of early career researchers.

These objectives address Topic 2 in Key Topic 2 (Understanding the Wastes) of the IGD-TP Strategic Research Agenda, which identifies a need for improved data and understanding of the underpinning scientific mechanisms of the release of radionuclides and chemical species from various long-lived Intermediate Level Wastes.  This includes detailed characterisation methods, issues related to adequate inventory determinations, chemical form, speciation on release and transport in the near field and far field.