Oxidative transformation of Tungsten (W) nanoparticles potentially released in aqueous and biologicalmedia in case of Tokamak (nuclear fusion) Lost of Vacuum Accident (LOVA)

Abstract

Fusion energy has the potential to provide sustainable solutions to global energy needs for the next generations. However, despite decades of intense international efforts many scientific and technological breakthroughs need to be achieved before fusion become available and economically viable. In addition, and prior to industrial development of the fusion technology, it is worth addressing possible negative environmental and health impacts. For instance, the interactions between the plasma and refractory materials called plasma facing components (PFC) like tungsten, will generate tritiated dust. The aim of the study is to address the fate in water and biological media of W nanoparticles that might be released in case of Lost Of Vacuum Accident (LOVA). The dilution of particles in TRIS, LHC9 and pulmonary media did not strongly affect the average size of the particles while the dilution in Saline medium lead to substantial aggregation. The results proved that oxidative dissolution of W nanoparticles occurred in several aqueous/biological media (TRIS, LHC9 and Lung media) with increasing time. Fromthe different dissolution rates as a function of the tested media, it seems that the oxidative dissolutions are rate limited by diffusion in the oxidized layer surrounding the metallic core of particles. The mechanisms of dissolution involved W4+and W6+corroded layers prior to W6Å dissolution. Knowledge provided by these dispersion-dissolution experiments helped to determine the environmental mobility and persistence as well as the bio-durability of these tungsten nanoparticles. As dissolution has potential to influence the toxicity of particles, it is a crucial parameter to consider in the risk assessment of particles.