Nuclear industry produces nuclear wastes which need to be managed on the long term. Depending on their classification based on radioactivity levels and lasting for various periods of time, radioactive wastes are treated and stored differently: intermediate and high level long-life wastes are most of the time immobilized into glass matrices while low and intermediate level wastes with short or long life are immobilized in cement or bitumen matrices (Abdel Rahman, Rakhimov et al. 2015, Andra 2023). One of the best ways to enhance the stabilisation of contaminants and radionuclides from the wastes is to have it directly react with the components of the cement to be incorporated within the mineral phases by redox, sorption and/or chemical reaction processes (Zatloukalová, Zatloukal et al. 2021, Bourchy, Saslow et al. 2022, Mukiza, Phung et al. 2023). However, many of the wastes have several competing species that exist in large excess compared to the target (e.g. sodium Na+, sulphate SO42- and ammonium NH4+) and these can be detrimental to cement hydration (hydration delay, difference of hydrates produced) or induce pathologies at different age (gas release, Delayed Ettringite Formation – DEF) (Collepardi 2003). However, these species can be harnessed to generate beneficial phases to ensure the long-term integrity of the resulting cement waste form.
Considering that, the objective of this research is to understand the interactions between the waste and the cementitious matrix with regard to composition (impact of sodium and sulphate), radioactivity and characteristics as they can impact cement hydration, heat produced and durability (Zhu, Zheng et al. 2022, Bourchy, Fujii Yamagata et al. 2023).
The methodology used will begin by a literature review of waste inventory from nuclear powered countries, a short list of waste compositions will be established. Several non-radiological formulations (using a surrogate) adapted from the reference nuclear wastes-free (such as geopolymer, alkali activated or ternary cement) will be developed considering a possible range of variation around targeted oxide values leading to hydration, setting and targeted mineralogy. The evolution of mineralogy, activation, hydration and mechanical properties will be monitored with time. Based on these properties, a selection of the best candidate formulations will be done before testing their durability through leach test when loaded with radionuclide surrogates (EPA 2013). An effort will be focused on tracking the evolution of these beneficial or deleterious phases in how they form during setting and how they evolve with environmental exposures.
Depending on the results, it is possible that the PhD student would collaborate with international partners to test the best formulations with radioactive materials and research visits.
Key words:
Cement, formulation, mineral incorporation, durability, nuclear waste
References:
Abdel Rahman, R. O., R. Z. Rakhimov, N. R. Rakhimova and M. I. Ojovan (2015). Cementitious materials for nuclear waste immobilization, John Wiley & Sons, Ltd.
Andra (2023). Inventaire national des matières et déchets radioactifs - Les essentiels 2023.
Bourchy, A., A. L. Fujii Yamagata, G. L. Smith, G. J. Sevigny, B. N. Seiner and S. A. Saslow (2023). ”Cerium oxide impact on fresh and hardened properties of cementitious materials.” Cement and Concrete Composites 138: 104976.
Bourchy, A., S. A. Saslow, B. D. Williams, N. M. Avalos, W. Um, N. L. Canfield, L. Sweet, G. L. Smith and R. M. Asmussen (2022). ”The evolution of hydrated lime-based cementitious waste forms during leach testing leading to enhanced technetium retention.” Journal of Hazardous Materials 430: 128507.
Collepardi, M. (2003). ”A state-of-the-art review on delayed ettringite attack on concrete.” Cement and Concrete Composites 25(4–5): 401-407.
EPA (2013). Mass Transfer Rates of Constituents in Monolithic or Compacted Granular Materials Using a Semi-Dynamic Tank Leaching Procedure - Method 1315 Revision.0, U.S. Environmental Protection Agency, Washington, D.C.
Mukiza, E., Q. T. Phung, L. Frederickx, D. Jacques, S. Seetharam and G. De Schutter (2023). ”Co-immobilization of cesium and strontium containing waste by metakaolin-based geopolymer: Microstructure, mineralogy and mechanical properties.” Journal of Nuclear Materials 585: 154639.
Zatloukalová, J., J. Zatloukal, J. Hraníček, K. Kolář and P. Konvalinka (2021). ”Study on the properties of cement composites for immobilization of evaporator concentrates.” Progress in Nuclear Energy 140: 103919.
Zhu, Y., Z. Zheng, Y. Deng, C. Shi and Z. Zhang (2022). ”Advances in immobilization of radionuclide wastes by alkali activated cement and related materials.” Cement and Concrete Composites 126: 104377.
CPDM laboratory (Physico-Chemical Behaviour and Durability of Materials) in MAST department (Materials and Structures) of the Université Gustave Eiffel at Champs-sur-Marne (France), conducts research projects and judicial assessments on different materials used in civil engineering (cementitious and alternative materials, bio-based materials and polymers). Specifically on cementitious materials, CPDM laboratory has several experts working on formulations and their impact on hydration, mineral, chemical and physical characterisation, material implementation, initial to long term performances comprehension and durability testing against internal and/or external attacks.
Contact(s):
Agathe Bourchy: agathe.bourchy@univ-eiffel.fr
Nicolas Roussel: nicolas.roussel@univ-eiffel.fr
Starting date: October 1st 2024
Contract: 3 years, Université Gustave Eiffel SIE doctoral scholarship, 2075€ monthly gross wage
Localisation: Champs sur Marne (77), France, in CPDM Laboratory (Physico-Chemical Behaviour and Material Durability), in MAST Division (Materials and Structures) of Université Gustave Eiffel