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5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Assessment of the literature about Be-W mixed material layer formation in the fusion reactor environment

Abstract All plasma facing surfaces in a fusion reactor, whether initially pure or an alloy, will rapidly evolve into a mixed material due to plasma-induced erosion, migration and redeposition. Beryllium (Be) erosion from the main chamber, and its transport and deposition on to a tungsten (W) divertor results in the growth of mixed Be-W layers, which can evolve to form beryllides. These Be-W mixed materials exhibit generally less desirable properties than pure tungsten or pure beryllium, such as lower melting points. In order to better understand the parameter space for growth of these alloys, this paper reviews the literature on Be-W mixed material formation experiments—in magnetically confined fusion reactors, in linear plasma test stands, and during thin-film deposition—and on computational modeling of Be-W interactions, as well as briefly assesses the Be-W growth kinetics. We conclude that the following kinetic steps drive the material mixing: adsorption of the implanted/deposited ion on the metal surface; diffusion of the implanted/deposited ion from surface into the bulk, which is accelerated by defects; and loss of deposited material through erosion. Adsorption dominates (or prevents) material mixing in thin-film deposition experiments, whereas diffusion drives material mixing in plasma exposures due to the energetic ion implantation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2024

Assessment of the literature about Be-W mixed material layer formation in the fusion reactor environment

All plasma facing surfaces in a fusion reactor, whether initially pure or an alloy, will rapidly evolve into a mixed material due to plasma-induced erosion, migration and redeposition. Beryllium (Be) erosion from the main chamber, and its transport and deposition on to a tungsten (W) divertor results in the growth of mixed Be-W layers, which can evolve to form beryllides. These Be-W mixed materials exhibit generally less desirable properties than pure tungsten or pure beryllium, such as lower melting points. In order to better understand the parameter space for growth of these alloys, this paper reviews the literature on Be-W mixed material formation experiments—in magnetically confined fusion reactors, in linear plasma test stands, and during thin-film deposition—and on computational modeling of Be-W interactions, as well as briefly assesses the Be-W growth kinetics. We conclude that the following kinetic steps drive the material mixing: adsorption of the implanted/deposited ion on the metal surface; diffusion of the implanted/deposited ion from surface into the bulk, which is accelerated by defects; and loss of deposited material through erosion. Adsorption dominates (or prevents) material mixing in thin-film deposition experiments, whereas diffusion drives material mixing in plasma exposures due to the energetic ion implantation.

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on Be2W by Materials Project

Be2W is Hexagonal Laves structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. there are two inequivalent Be sites. In the first Be site, Be is bonded to six equivalent Be and six equivalent W atoms to form a mixture of corner, edge, and face-sharing BeBe6W6 cuboctahedra. All Be–Be bond lengths are 2.25 Å. All Be–W bond lengths are 2.62 Å. In the second Be site, Be is bonded to six Be and six equivalent W atoms to form a mixture of corner, edge, and face-sharing BeBe6W6 cuboctahedra. There are two shorter (2.19 Å) and two longer (2.27 Å) Be–Be bond lengths. All Be–W bond lengths are 2.62 Å. W is bonded in a 12-coordinate geometry to twelve Be atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Be22W by Materials Project

Be22W crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. there are four inequivalent Be sites. In the first Be site, Be is bonded to twelve Be atoms to form a mixture of edge, face, and corner-sharing BeBe12 cuboctahedra. There are six shorter (2.05 Å) and six longer (2.26 Å) Be–Be bond lengths. In the second Be site, Be is bonded in a distorted linear geometry to twelve equivalent Be and two equivalent W atoms. All Be–Be bond lengths are 2.46 Å. Both Be–W bond lengths are 2.50 Å. In the third Be site, Be is bonded to twelve Be atoms to form a mixture of distorted edge, face, and corner-sharing BeBe12 cuboctahedra. There are a spread of Be–Be bond distances ranging from 2.19–2.29 Å. In the fourth Be site, Be is bonded to eleven Be and one W atom to form a mixture of distorted edge, face, and corner-sharing BeBe11W cuboctahedra. There are a spread of Be–Be bond distances ranging from 2.13–2.35 Å. The Be–W bond length is 2.54 Å. W is bonded in a 4-coordinate geometry to sixteen Be atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Be12W by Materials Project

Be12W crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are three inequivalent Be sites. In the first Be site, Be is bonded in a 2-coordinate geometry to nine Be and one W atom. There are a spread of Be–Be bond distances ranging from 2.15–2.35 Å. The Be–W bond length is 2.53 Å. In the second Be site, Be is bonded to ten Be and two equivalent W atoms to form a mixture of face, edge, and corner-sharing BeBe10W2 cuboctahedra. All Be–Be bond lengths are 2.10 Å. Both Be–W bond lengths are 2.76 Å. In the third Be site, Be is bonded in a 12-coordinate geometry to ten Be and two equivalent W atoms. Both Be–Be bond lengths are 2.15 Å. Both Be–W bond lengths are 2.59 Å. W is bonded in a 12-coordinate geometry to twenty Be atoms.

36 MATERIALS SCIENCE↗