Mykhailovsky V. Physical aspects of application of the ultrasonic testing of temperature fields and thermal stresses in the reactor steels in nonstationary conditions

The thesis presents results of ultrasound (US) studies of specimens made of 08Cr18N10T (08Cr18Ni10Ti), 15Cr2MFA (15Cr2MoVA), Sv-07Cr25Ni13, Sv-08Cr19Ni10Mn2Nb, and 15Cr2NMFA (15Cr2NiMoVA) steels which were cut from the archival fragment of the VVER pressure vessel walls under quasi-thermodynamic equilibrium condition and pulse heat load (PHL) in the overall temperature range Т=0 350 оС. The reference data on the acoustic and elastic properties of the aforesaid steels in quasi-thermodynamic equilibrium conditions are obtained. Significant anisotropy of the US velocities and elastic modules and their spatial heterogeneity in specimens made of 08Cr18N10T, Sv-07Cr25Ni13, Sv-08Cr19Ni10Mn2Nb steels (wall cladding of pressure vessel) were revealed. Using the US method of texture analysis the evolution of texture of the cladding layers by depth was studied. A satisfactory correlation between the thermal profile T(x, t) reconstructed by US method and the independent thermometric measurements during the PHL was established. The later results of other authors qualitatively coincide with the obtained data on the reconstruction of T(x, t). The calculated corresponding thermal stresses ?(x, t) also in good agreement in absolute value with the results of calculations by OKB Gidropress (2015) for a single-layer wall of the VVER-1000 pressure vessel for emergency regime with a thermal shock. Models of reconstruction of T(x, t) in two-layered walls of closed constructions with one-way access under PHL are improved. As a result of the studies, a physical basis for substantiation of the method of ultrasonic nondestructive testing of temperature fields and thermal stresses in closed constructions of the VVER pressure vessels type under nonstationary thermal conditions has been created.