Delayed Ettringite Formation Thermal Management in Cement Grout for Long-Lived Intermediate-Level Radioactive Waste Conditioning

Isabelle Rupp (1, 2) , Bursi Jean-Michel (3)

1 EDF R&D - EDF R&D
2 EDF R&D MFEE - Mécanique des Fluides, Energies et Environnement
3 EDF-DP2D

Activated long-lived medium or intermediate-level metallic radioactive waste (LL-ILW) from dismantled or in operation French nuclear power plants are conditioned since 2021 in a new EDF1 facility (ICEDA) located in the Middle East of France. The conditioning consists in blocking waste in a cement grout inside a long-lasting and confining con-crete container. Due to the waste radioactivity, the process is carried out remotely, in hot cells. Containers must have confining properties to be disposed without any additional packaging in the future French final geological repository studied by ANDRA2. The goal is to demonstrate that confinement properties of the concrete container are preserved during manufacturing and storage stages in the EDF facility and then after transfer to the ANDRA repository. Many phenomena, such as irradiation and radiolysis, shrinkage induced by drying, carbonation and corrosion, can alter confining properties of the container. This paper focuses on the manufacturing stage and especially on industrial operating conditions that have been defined in order to limit the temperature rise and thus control the risk of Delayed Ettringite Formation in the packages. Temperature of the block-ing grout is directly influenced by the thermal residual power of the metallic waste and by the exothermic reaction taking place during the hydration phase of the blocking grout. To verify that the core temperature of packages stays below the 75°C threshold during the manufactur-ing process, experiments have been carried out with full scale package prototypes instrumented with thermocouples. Then, a thermal numerical model of the mock-up has been developed and validated based on the measurements. At last, an experimental campaign, including 5 instrumented packages with inactive waste, has been carried out in the industrial facility. Again, numerical model comparisons between measurements and calculations indicate that the numerical model is predictive and ultimately makes it possible to perform a sensitivity study. This study leads to identify manufacturing parameters required to ensure that the package core temperature will stay under 75°C: initial grout temperature and manufacturing cell temperature have to be controlled according to the nature and the mass of the waste in the packages.

Mots clés: Nuclear waste thermal management conditioning cement manufacturing process; Nuclear waste; thermal management; conditioning cement; manufacturing process

Domaines: Physique [physics]; Informatique [cs]

Isabelle Rupp, Bursi Jean-Michel. Delayed Ettringite Formation Thermal Management in Cement Grout for Long-Lived Intermediate-Level Radioactive Waste Conditioning. NUWCEM 2022 – International Symposium on Cement-Based Materials for Nuclear Wastes, SFEN, May 2022, Avignon, France. ⟨hal-04060690⟩