Applied Physics and Mathematics Annotation << Back Graphite grow old mechanism under irradiation. The critical fluence of neutron irradiation P.A. Platonov O.K. Chugunov I.F. Novobratskaya V.M. Alekseev V.Y. Manevsky L.L. Lishov E.I. Smorodkin D.A. Kuleshov In 1964 year in «hot» laboratory of «Kurchatov Institute» (later department) the group of graphite research has been organized. P.A. Platonov was assignment as a head this group. «The stress analyses cod of graphite details» has been worked (together with RDIPI – main designer) after 10 years of graphite research. They are actual for the present time. The program of creation of high temperature graphite reactors (HTGR) in Russia has been declared in 1970 year (project VG-400).Work on research of radiation stability of graphite under high irradiation temperatures (up to 900 oC) has began. The experiments on irradiation carry out mainly in MR,SM-2 and fast reactor BR-10. Ya. I .Shtrombakh (together with V.M . Alekseev as an assistant) was assignment as a head of this work. The unique experiments on electron – microscopic research of graphite structure degradation has been performed by B.A. Gurovich in this period. These result permit as to understand the mechanism of graphite structure degradation due to creation of inter crystalline cracks. In process of all these experiments it became clear that the graphite behavior of different grades differ from each to other. The main single criterion was need to describe the process of graphite degradation on neutron irradiation for different grads. Such criterion was suggested by P.A. Platonov. That was critical fluence of neutron irradiation (Fкр) – neutron fluence when the volume of graphite after shrinkage and swelling came back to its initial value. At this stage of irradiation all properties of graphite changes rapidly and graphite looses its capacity as design material. This criterion has been accepted as main criterion for estimation of irradiation stability of graphite in « Technique of estimation of residual resource of RBMK -1000 reactor graphite stack». Keywords: graphite, neutron fluence, graphite stack, physicalmechanical properties. Contacts: E-mail: platonov@irtm.kiae.ru Pp. 08-16.