Speaker
Description
Oxidation kinetics studies for the treatment and disposal of current and future UCx target materials
N.-T. Vuong1,2, P. Schouwink3, S. Chowdhury4, A. P. Gonçalves4, O. Walter5, K. Popa5, K. Sivula2, T. Stora1
1 CERN, 1211 Geneva 23, Switzerland
2 École Polytechnique Fédérale de Lausanne, 1015 Lausanne, Switzerland
3 École Polytechnique Fédérale de Lausanne, 1950 Sion, Switzerland
4 C2TN Instituto Superior Técnico, Universidade Lisboa, 2695-066 Bobadela LRS, Portugal
5 European Commission, Joint Research Centre, 76125 Karlsruhe, Germany
Uranium carbide-carbon composite (UCx) is the most used target material at ISOLDE (> 65% of the beam time). About 12 UCx targets are produced annually and operated at temperatures up to 2300°C to promote isotope release. Under these conditions, microstructures are degraded (i.e. loss of porosity, increase of grain size) due to sintering, which results in a loss of radioisotope beam intensity over time.
Over the last decade, new porous target nanostructures were developed to improve their isotope release efficiency while keeping microstructural stability at high temperatures [1,2]. However, new nanomaterials were found highly pyrophoric and require extreme care in all handling procedures. Since actinide carbide materials are not compatible with long-term storage requirements, a safe process for their conversion into stable oxides is investigated.
In this talk, systematic investigations on the oxidation of five different uranium carbide and carbon composite materials will be presented. A combination of characterization and thermal analysis techniques were used to study the reaction mechanism and its kinetics. It was found that, despite their different characteristics, the materials generally followed a similar reaction pathway. However, the onset oxidation temperatures and kinetics were strongly affected by the sample form, grain size and carbon content.
The study provided valuable inputs for the design of safe oxidation and disposal procedures for current and future UCx composite targets waste at ISOLDE, such as the microporous, high density or nanostructured targets.
This research project has been supported by a Marie Skłodowska-Curie Innovative Training Network Fellowship of the European Commission's Horizon 2020 Programme under contract number 642889 MEDICIS-PROMED.
References
[1] Y. Kadi et al., EURISOL High Power Targets, Nuclear Physics News, 18:3, 19-25 (2008) (accessed http://www.nupecc.org/?display=npn/issues, Feb 2021)
[2] J. P. Ramos. NIM B, 463(May), 1–10.
https://doi.org/10.1016/j.nimb.2019.05.045
