[en] The surface area of the fissure inside the glass block is an important parameter influencing the long term behavior of high level radioactive waste glass in the aqueous media during the deep geological disposal. Inverse gas chromatography is used to study the surface area and specific surface area of these fissures. The fissure webs inside the glass block are simulated by the voids between the glass particles filled in the column of the chromatography. Glass samples of 11 g were filled in the column with a diameter of 6 mm and a length of 600 mm. The column temperature was kept at 50℃ with the temperature of the injection and chamber at 200℃. The carrier media is helium with a flowrate of 25 ml/min. The probes injected were methane and the pentanol. The peak of the methane is used to determine the dead volume of the column and the peak of methane is used to calculate the adsorption isotherm of the pentanol onto the glass surface. After the adsorption isotherm is calculated, the surface area of the glass will be obtained. The study showed that inverse gas chromatography technique is practical and precise for the measurement of the fissure areas inside the glass block. The relative deviation for the surface area is less than 10%. (authors)