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The X ray degree of crystallinity, χ, and the density, ρ, of suspension polymerized polytetrafluo roethylene after its irradiation above the melting temperature of the crystalline phase are studied. A compar ison of dose dependences of χ and ρ makes it possible to infer that pores occur in the initial polytetrafluoro ethylene and that porosity substantially decreases during irradiation. The time of pore contraction in polytet rafluoroethylene after its radiation modification above the meting temperature is estimated with respect to the order of the magnitude. This estimate is based on the consideration of viscous flow under the action of sur face tension forces.