Speaker
Description
Uranium carbide (UCₓ), thorium carbide (ThCₓ), and lanthanum carbide (LaCₓ) constitute approximately 85% of the target materials used at CERN-ISOLDE. These carbides are highly pyrophoric and must be chemically stabilized after proton irradiation to enable their safe handling and disposal as radioactive waste, preventing ignition and thermal runaway upon exposure to ambient air or oxidizing atmospheres.
The chemical stabilization process, including scale-up experiments, was successfully demonstrated for lanthanum carbide (LaCₓ) [1,2]. The operational experience and data obtained from these studies enabled the initiation of uranium carbide (UCₓ) stabilization experiments using a dedicated system integrated to an inert-atmosphere nuclear glovebox working at negative pressure [3]. UCₓ hydrolyzed under controlled water vapor concentrations, releasing hydrogen and hydrocarbons monitored via non-dispersive infrared spectroscopy (NDIR) and residual gas analysis (RGA). The solid product is being characterized to prove its stability in ambient air. A similar strategy will also be applied to ThCₓ and nano-UCₓ.
The objective is to develop a controlled stabilization process for these materials within ISOLDE hot cells, ensuring radiological and chemical safety. The stabilized materials will subsequently be conditioned, packaged, and prepared for long-term disposal in Swiss deep geological repositories.
Keywords: uranium carbide, ISOLDE target, radioactive waste, pyrophoricity, thermal runaway, chemical stabilization
References
[1] Usta, S. Controlled Hydrolysis of Lanthanum Carbide to Form Submicron- to Nano Lanthanum Hydroxide, manuscript in preparation, 2026.
[2] LaCx Chemical Stabilization [EDMS No.: 3342156]
[3] UCx Reoxidation [EDMS No.: 3299121]
