The paper presents the analysis of dynamic behavior of the reinforced concrete containment of NPP unit under the combined effect of internal pressure shock caused by the accident in the reactor hall and seismic impact of design-basis earthquake using the finite element method (FEM) and DIPROS software. Using the modal analysis and numerical solution of the FEM equations of containment concrete, the stress-strain state of the building structure in the post-accident period was defined. It is shown that the maximum intensity of the stresses in the steel liner of the containment does not exceed the yield strength of the steel liner material. Accordingly, the liner integrity is preserved, the containment remains operable and ensures compliance of radiation safety requirements.

Computer analysis of thermomechanical state of the sealing steel lining under relevant extreme hazards has been performed to define the possibility and scope of loss of integrity of sealing steel lining, in particular the possibility of losing of the confining function by the NPP reactor compartment containment under emergency conditions. The study gave an opportunity to obtain functions of stress strain parameter evolution function in reinforced concrete and sealing steel lining depending on changes in emergency temperature and pressure in the reactor compartment. The paper assessed the margin of sealing steel lining bearing capacity.

Over the last decade, new national regulatory documents on the design and assessment of the technical state of building structures, in particular steel ones, have been put into force in Ukraine to replace relevant former USSR regulations. The experience of applying new national regulatory documents indicates certain incorrect provisions, which can potentially cause catastrophic consequences in case of failure of steel building structures of corresponding facilities and(or) hazardous production capacities. The paper presents the analysis of Ukrainian regulations to check compliance of available methodologies for computer strength justification of steel structures. It is established that current regulatory documents of Ukraine do not contain a description of methodologies and procedures (formulae) with regard to calculations of steel structures on resistance to brittle fracture and cyclic crack resistance. The analysis of a number of publications was performed to define methods for the calculation of steel structures to check endurance, cyclic crack resistance and resistance to brittle fracture.