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The grain boundary sink strengths for intrinsic point defects in an anisotropic lattice are calculated.It is shown that the sink strength depends on the grain size, its shape, its metallurgical state, and, for hexagonal symmetry, on the anisotropy factor for the diffusivity (DJD.). It appears to be independent of the volume averaged diffusivity constant. For the grain shape dependence, the Holt and Ibrahim anisotropy factor is obtained only as a limit case.Die Starke der Korngrenzensenke fur Eigen-Punktdefekte in einem anisotropen Gitter wird berechnet. Es wird gezeigt, daB die Senkenstarke von der KorngroBe, deren Form, metallurgischer Zustand und fur hexagonale Symmetrie, vom Anisotropiefaktor fur das Diffusionsvermogen (D,D,) abhangt. Sie scheint von der volurnengemittelten Diffusionskonstante unabhangig zu sein. Fur die Abhangigkeit der Kornform wird der Anisotropiefaktor nach Holt und Ibrahim nur als Grenzfall erhalten. 37*

An irreversible thermodynamic model is proposed for describing the deformation of a crystal under stress and irradiation. A thermodynamic inequality is found to relate the lattice straining and stress with the irreversible part of the free energy density. As an application of the model the case of straight dislocation climbing under irradiation is studied.Un modhle thermodynamique irreversible est propose pour dbcrire la deformation d'un cristal sous contrainte et irradiation. Une idgalit6 thermodynamique est trouv6e qui rattache la &for-mation e t les contraintes du reseau avec la partie irreversible de la densite d'energie libre. Comme application du modhle on 6tudie le cas de la montee d'une dislocation coin sous irradiation.