Effect of the Degree of Perfection of Reactor Graphite on Performance

Experimental data on the density changes occurring in graphite blocks of RBMK masonry in the course of operation of the reactor are presented. They show significant variance due to the nonuniformity of the radiation-induced change in the properties which is associated with the difference in the degree of perfection of the initial graphite. Experimental data on the dependence of the radiation-induced deformation at the shrinkage stage versus the size of the graphite crystallites are presented. An attempt is made to explain the mechanisms giving rise to this dependence. Experimental data showing that for temperature changes within certain limits from T1 to T2 the graphite transforms under irradiation into a state that would be observed under irradiation at T2 at the outset. A relation for determining the difference between the maximum depth of shrinkage of the graphite samples irradiated at temperatures T1 and T2 is proposed on the basis of an analysis of the experimental data.