Heures thésards

Animé par Johannès Jahan

jeudi 9 juillet 2020 à 14:00

En visio

Boron and iodine behaviour during nuclear glass vapor hydration

Haohan Zhang

Subatech (équipe Radiochimie)

In France the nuclear waste glass, designed to confine high level radioactive materials, is proposed to be disposed in the disposal facilities constructed underground and with engineered barriers to prevent the release of radioactive materials.
During the long-term disposal of the nuclear glass, underground water will penetrate the engineered barriers and make the disposal cell re-saturated. It may lead to radioactive elements release upon glass dissolution. Before re-saturation, the unsaturated state may be kept for thousands of years due to the presence of hydrogen gas generated via the corrosion of glass canister. Thus, it is probable that nuclear glass will contact water vapor prior to aqueous solution. Recent studies suggested that glass vapor hydration process cannot be simulated as the glass aqueous corrosion and that the constituents of the hydrated layer were instantly released in aqueous solution [1]. As a result, understanding the durability of nuclear glass in vapor phase is indispensable for evaluating the long-term safety of nuclear glass.

The current PhD thesis focuses on studying the hydration of nuclear glass in vapor phase. The mechanism of glass vapor hydration is discussed by investigating the release of boron and iodine during the hydration process. The results indicate the possible transformation of tetrahedral 4B to trigonal 3B on the hydrated glass surface, which may result in the volatilization of boron in the form of boric acid.

[1] J. Neeway, et al., J. Non-Cryst. Solids 358, 21 (2012).

Cluster production in heavy ion collisions at Fermi energie

Yifeng CHEN

Subatech (équipe Théorie)

E. Bonnet(1), V. De-La-Mota(1)
(1) Subatech UMR 6457 (IMT atlantique, Université de Nantes, IN2P3/CNRS)

Investigating the production of clusters (nucleons ended together) produced in heavy ion collisions (HIC) helps to understand the dynamics in nuclear collision, constraining both equation of state (EOS) of non-homogeneous nuclear matter and the correlation treatment in transport models.[1] When the central collisions happen between the heavy nuclei, in the early state, a hot nuclei is formed by the projectile and the target, which is a compressed and excited system. Depending on the incident energies, the evolution of the nuclei could be different. When the energies come to the regime of Fermi energy, the multifragmentation will dominate. The products of the collision could be fragments, light particles and nucleons, depending on the incident energy of projectile, the mass of the system and the impact parameter. Then the clusters built by these products could be different.
Systematic analysis of the system Xe + Sn collisions is based on the data collected with 4π apparatus INDRA in GANIL for different beam energies: 12 MeV/A, 18 MeV/A, 25 MeV/A, 32 MeV/A and 45 MeV/A. To estimate the fragmentation degree of the collision system, the charge of the biggest fragment (Zmax) is chosen as the straight forward observable. Beside, multiplicity and the mass fraction of the fragments are the observables for the analysis.

[1] BONNET, E. Evolution of cluster production with fragmentation degree.