[en] The cause of the pellet-clad interaction failures are the combined effects of differential thermal expansion driven localized stress, and aggressive fission products, primarily iodine (pitting corrosion). Reactor pressure vessel is also being exposed to high mechanical loads and to an intensive neutron flux irradiation. This leads to a gradual decrease in resistance to brittle fracture. The finite element method has been selected for the solution of the above problems, and results are presented in form of isobars and isotherms respectively in the meridional cross section. (author)