Permanent staff: Céline Cannes, Sylvie Delpech, Davide Rodrigues

Post-doctoral researcher : Kim Le

PhD students: Pauline Bouhier, Gabriel Poras

Description of the research activities

The operation and decommissioning of the nuclear facilities generate a large volume of radioactive metallic wastes, which have to be managed as a function of their radioactivity level and their lifetime. The conditioning of metallic waste of low and intermediate level consists in their encapsulation in a cement in a drum to limit the corrosion with water and dioxygen. However, some metallic wastes are too reactive in the usual matrices like Portland cements and so hydrogen is produced by aqueous corrosion. The eligible H2 amounts in the storage site correspond to the concentration of the explosive limit or to the pression increase, which can lead to the damage of the package and so to the loss of the radioactivity confinement. New matrices, such as the magnesium phosphate cements (MPC) and the geopolymers (GP) are under study (formulations, reactivity of metals in these media) to evaluate the risks generated during the conditioning and to reduce the H2 production inside the package.

The work of this topic within the CHIMèNE team mainly concerns the massive metal waste generated during the dismantling of Natural Uranium Graphite Gas reactors: Al (fuel cladding plug), MgZr (fuel cladding). The results show that the MPCs make it possible to confine the Al waste and the GPs to confine MgZr polluted by the fuel in U metal. Part of this work is carried out within the framework of the PREDIS project, with a study on the reduction in the cost of MPCs and on the corrosion of the steel drum in contact with these matrices. More recently, a research axis has been developed on the management of metal waste generated by fusion reactors, in particular beryllium, which is a strong chemical toxicant.

The problem of nuclear waste in the form of powders, exhibiting increased reactivity, is also studied. It is envisaged to dissolve the metal powders in molten hydroxides at 250 °C. The solution obtained can then be used to prepare the conditioning matrix.

Collaborations

    CEA (Marcoule, Cadarache, Saclay), ORANO

PhD thesis in progress and defended

  • Pauline Bouhier (Université Paris-Saclay, CEA funding, 2019-2021) : Comparative study of Be and its simulants for its conditioning in a cement matrix.
  • Gabriel Poras (Université de Montpellier, CEA funding, 2021-2023) : Study of the conditioning of aluminum alloys in a matrix based on phospho-magnesium cement.
  • Hugo Lahalle (Université de Bourgogne, CEA funding, 2014-2016) : Conditioning of metallic aluminum in phospho-magnesium cements.

Last publications

  • C. Cannes, D. Rodrigues, N. Barré, D. Lambertin, S. Delpech, Reactivity of uranium in geopolymers, confinement matrices proposed to encapsulate Mg-Zr waste. J. Nucl. Mater. 518 (2019) 370-379
  • D. Rodrigues, C. Cannes, N. Barre, D. Lambertin, S. Delpech. Role of fluoride ions on the uranium oxidation mechanism in highly alkaline solutions. Electrochim. Acta 266 (2018) 384-394
  • Hugo Lahalle, Céline Cau Dit Coumes, Cyrille Mercier, David Lambertin, Céline Cannes, Sylvie Delpech, Sandrine Gauffinet. Influence of the w/c ratio on the hydration process of a magnesium phosphate cement and on its retardation by boric acid. Cem. Concr. 109 (2018) 159-174
  • S. Delpech, C. Cannes, N. Barré, Q. Thuan Tran, H. Lahalle, D. Lambertin, S. Gauffinet, C. Cau Dit Coumes. Kinetic Model of Aluminum Behavior in Cement-Based Matrices Analyzed by Impedance Spectroscopy. J. Electrochem. Soc. 164 (2017) C717-C727
  • H. Lahalle, C. Cau Dit Coumes, A. Mesbah, D. Lambertin, C. Cannes, S. Delpech, A. Nonat, S. Gauffinet. Investigation of magnesium phosphate cement hydration and its retardation by boric acid. Cem. Concr. Res. 87 (2016) 77-86
  • C. Cau Dit Coumes, D. Lambertin, H. Lahalle, P. Antonucci, C. Cannes, S. Delpech. Selection of a mineral binder with potentialities for the stabilization / solidification of aluminum metal. J. Nucl. Mat. 453 (2014) 31-40