ASTM D8645-25

1.1 This guide covers the measurement of gas permeability of carbon and graphite by using a method based on the Darcy equation. The gas permeability can be estimated by using this method.

1.2 The gas permeability measurements for the method are at gas pressures up to 0.5 MPa, due to the specific method of specimen sealing.

1.3 This guide is based on experiments conducted on specimens between 10Ø × 20 mm to 50 mm, 20Ø × 20 mm to 50 mm, 30Ø × 20 mm to 50 mm. This guide may be suitable for other sizes but caution should be exercised with smaller specimens.

1.4 Units—The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.

1.5 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.6 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.

4.1 Gas permeability is an important property which is required for correct modelling of graphite oxidation and to understand interactions between gas and graphite components in reactors. Such interactions may include thermal and radiolytic oxidation, as well as the escape of gaseous fission by-products through the graphite components.

4.2 The test methods described in this guide can be used to characterize graphite and carbon materials for design purposes and post irradiation examination (PIE).