The paper investigates the dependence of the transformation texture of Zr-2.5wt%Nb tubes and rods on the initial texture, the method of heating (furnacing, conductive heating, inductive heating) and cooling (furnace cooling, water quenching, water shower), stress, and thermal cycling. It was demonstrated that the primary factors determining the transformation texture are the initial texture and the heating rate for quenching. From the investigation results, a method of final thermal treatment of finished zirconium reactor core components (pressure tubes, guide tubes, and cladding fuel rods) is suggested, allowing the destruction of their texture without changing the well-established manufacturing process. The suggested SHF heating includes the use of the α→β→α transformation with fast heating up to the β-phase, subsequent quenching for texture destruction, and annealing for transformation from the metastable α'-state to the equilibrium double-phase αZr + βNb state.

The results of studying the dependence of mechanical properties, corrosion and radiation resistances of hafnium rods on their structure are presented and reviewed in this paper. As observed, the rods in a fully recrystallized state with a finegrained structure possess optimal mechanical properties (high strength and ductility). Tensile strength of these rods at room temperature is of ≈575 MPa, percentage elongation is of 27-28%. Autoclave corrosion tests and anode polarization curves reveal that oxide films formed on hafnium samples in a fully recrystallized state are the most protective that is due to the low surface activity at the medium-metal interface. The corrosion rate of such hafnium rods at the initial period of oxidation (before the pre-transition period) is well described by the empirical power equation with the power coefficient of 0.242 ± 0.015. After the transition point (≈6000 h), the corrosion kinetics is described by a linear dependence with the oxidation rate of 3.12 ⋅ 10 −4 ± 2.07 ⋅ 10 −5 mg/(dm 2 ⋅ h). As shown, there is a correlation between the radiation growth of hafnium rods and their texture coefficient (Kearns's parameter) accor ding to the results of radiation tests carried out at the JSC 'SSC RIAR' (RF) as well as structural-textural studies of the same samples of hafnium rods in various structural states performed in this work. The results presented in this paper reveal that the coefficient of radiation growth linearly decreases with an increase of the Kearns's parameter to a value of 0.33. This indicates that hafnium rod samples with a more isotropic texture are less susceptible to radiation growth. The radiation growths differ, depending on the rods' structure. For rods with the same texture and different grain sizes, the samples with a fine-grained structure are less disposed to radiation growth. While Kearns's parameters are similar, the hafnium rods with a coarse-grained structure show a higher rate of radiation growth. The deformation *

The paper researches into the effect of the initial structural condition of Zr-2.5%Nb alloy, which is widely used in reactor engineering to manufacture reactor core components (mainly as a structural material for RBMK and CANDU pressure tubes), and of irradiation conditions (temperature, applied stress) on irradiation hardening and embrittlement. The reactor damage of Zr-2.5%Nb alloy was modeled with a method of high-energy 225 MeV (e,γ)-beam irradiation, which allows samples to be irradiated under strictly controlled stress conditions. The research has been carried out on Zr-2.5%Nb alloy exposed to four types of thermo-mechanical treatment. It has been found that the alloy is susceptible to intensive irradiation embrittlement irrespective of its initial condition, and the intensity of Zr-2.5%Nb irradiation hardening greatly depends on pre-treatment. In contrast to other conditions, Zr-2.5%Nb alloy is virtually not susceptible to irradiation hardening after high-speed high-frequency (SHF) heating, quenching, and subsequent annealing in the high-temperature range of the α-region, during which the double-phase α+βNb state with high dispersion of βNb (∼1023 m−3) precipitates develops. The obtained results are in good agreement with the post-reactor irradiation tensile test results. The study demonstrates the efficiency of high-energy (e,γ)-beam irradiation for investigating the irradiation hardening and embrittlement of zirconium alloys.

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