<p>A research software package has been developed to solve nonstationary and nonlinear boundary value problems of thermomechanics and fracture mechanics in a three-dimensional formulation. The computational analysis is based on a mixed scheme of the finite element method, which ensures the continuity of not only displacements but also deformations and stresses. Calculations of the stress-strain state take into account the history of elastic-plastic deformation, residual technological heredity in the form of residual strain fields, and radiation effects , including hardening and swelling of irradiated metal. The main features of the software package include accurate implementation of static boundary conditions for stresses on the body surface, a built-in fragmentation procedure, and libraries of parameterized computational models with built-in cracks and piping system elements. The calculations are based on the use of proposed mixed finite elements, which utilize a hexagonal prism and a tetrahedron. Modern computational approaches to analyzing the stress-strain state and fracture resistance of critical equipment elements in the first circuit of the WWER-1000 reactor unit, specifically the nuclear reactor vessel and the PGV-1000M steam generator, have been implemented. The results of the calculations obtained using the software package were utilized during the state examination of works related to the extension of the beyond-design operation of power units at nuclear power plants in Ukraine. The software includes tools that enable the rapid assessment of brittle fracture resistance to identify unfavorable emergency cooling conditions of the reactor vessel and hazardous locations and orientations of postulated cracks. The refined analysis of the fracture resistance of the collector-to-vessel welding assembly is based on calculating the stress-strain state in an elastic-plastic formulation using the fragmentation procedure and incorporating the calculated crack into the finite element model of the structure. To evaluate the fracture resistance of the weld assembly, not only a surface semi-elliptic crack but also surface defects in the form of an elongated crack and an extended groove in combination with the postulated semi-elliptic crack are used. The developed software package was used to analyze the strength of the WWER-M research nuclear reactor vessel and its components, thereby justifying the extension of safe operation. A library of parameterized models of typical pipeline elements was created to assess the strength and durability of key components in the main pipeline systems of the oil and gas industry. The developed software was utilized to investigate the kinetics of thermal fatigue cracks in gas turbine engine components of aircraft. The software complex is continuously improved and supplemented with the latest developments and modern software tools to solve a wide range of current scientific and applied problems related to the assessment of strength and fracture resistance of spatial structures of complex shape under the influence of intense thermal and power loads, prolonged neutron irradiation and subcritical damage of the metal using brittle-viscous fracture models.</p>