Dissolution and diffusion of helium in graphite

doi:10.1016/0022-3115(91)90067-H

Journal of Nuclear Materials

Volumes 179–181, Part 1, March–April 1991, Pages 227-230

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Abstract

Thermal desorption measurements were performed on three isotropic graphite samples which were exposed to helium gas at 100–700° C under 7–130 kPa for 1 h. Helium atoms which were desorbed from the sample during ramp heating at 10° C/min in vacuum were identified with a quadrupole mass spectrometer. Helium was dissolved into graphite for a few ppm in atomic fraction. The thermal desorption curve for ISO-880U appears to consist of two peaks (450 and 620° C) after helium gas exposure at above 500° C. The helium desorption can be ascribed to the diffusion-controlled process where the helium atoms may leave through bulk surface and open pores.

References (7)

H.F. Dylla
J. Nucl. Mater.
(1989)
S. Kato
J. Nucl. Mater.
(1989)
H. Atsumi et al.
J. Nucl. Mater.
(1988)

There are more references available in the full text version of this article.

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Dissolution and diffusion of helium in graphite

Abstract

J. Nucl. Mater.

J. Nucl. Mater.

J. Nucl. Mater.