J.P. Sharpe

A review of dust in fusion devices: Implications for safety and operational performance

Abstract Dust is produced in fusion devices by energetic plasma–surface interactions. As the amount of dust increases, potential safety and operational concerns arise. The dust may contain tritium, may be radioactive from activation products, and may be chemically reactive and/or toxic. Possible accidents in large fusion reactors could mobilize the dust and threaten public safety. Dust also poses potential problems to device operation. For example, plasma startup could be impeded, particulate injected from flaking deposits may disrupt the fusion plasma, and tritium retention in dust will affect fuel recovery systems. The current understanding of dusts role in fusion devices is reviewed in this paper by discussing mechanisms of dust production, considering ways dust impacts device safety and operation, and comparing characteristics of dust collected from existing fusion plasma research devices.

Modeling of particulate production in the SIRENS plasma disruption simulator

Abstract Modeling of the complex interplay among plasma physics, fluid mechanics, and aerosol dynamics is critical to providing a detailed understanding of the mechanisms responsible for particulate production from plasma–surface interaction in fusion devices. Plasma/fluid and aerosol models developed for analysis of disruption simulation experiments in the SIRENS high heat flux facility integrate the necessary mechanisms of plasma–material interaction, plasma and fluid flow, and particulate generation and transport. The model successfully predicts the size distribution of primary particulate generated in SIRENS disruption-induced material mobilization experiments.

Characterization of surface morphology and retention in tungsten materials exposed to high fluxes of deuterium ions in the tritium plasma experiment

Under appropriate conditions, exposing tungsten to a high flux D plasma creates near-surface blisters and other changes in surface morphology. We have characterized the sizes of blisters formed at different temperatures (147 °C≤Tsurface≤704 °C) and performed a surface analysis to elucidate factors that influence blister formation. Tungsten targets that were exposed to low energy (70 eV) D ions at a flux of 1.1×1022 m−2 s−1 in the tritium plasma experiment (TPE) were considered. We used AES to analyze the surface for evidence of implanted impurities. Blister diameters and heights were quantified using SEM imagery and vertical scanning interferometry. Given the likelihood of D precipitation in blisters, we expect that the data obtained here could be incorporated into a computational model to better simulate the diffusion and desorption of D in W. With this in mind, we present an analysis of thermal desorption profiles showing the release of D from the surface.

Oxidation and Volatilization from Tantalum Alloy T-222 During Air Exposure

................................................................................................................................ ii SUMMARY................................................................................................................................. iii ACKNOWLEDGMENTS ............................................................................................................iv