A procedure has been developed to determine the geometrical parameters of fuel assemblies (FA) by an ultrasonic pulse-echo technique used for all types of light-water reactor FAs. The measurement of geometrical parameters is achieved through the pairwise installation of ultrasonic transducers opposite the FA spacer grid faces at a distance of not more than a half of the transducer acoustic field near-region length such that the acoustic axes of the pairwise transducers are parallel to each other. The advantages of the presented technique is that it enables monitoring of any FA modifications, including the VVER reactor assemblies with a different number of spacer grids. The paper presents a mathematical model of the acoustic path developed in a geometrical acoustics approximation and its verification results. The model was used for computational and experimental studies of the ultrasonic test technique, and engineering formulas have been developed to calculate the errors of the transducer-measured distance to the FA surface. A code has been developed to simulate the FA form change monitoring and can be used to design new monitoring systems. The developed technique to determine the VVER-1000 FA geometrical parameters was introduced at units 1 and 2 of the Temelin NPP, the Czech Republic, for the TVSA-T FA form change monitoring. The successful use of the proposed technique makes it possible to recommend it for use in inspection benches at other NPPs.

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Objectives assessment of structural changes in the calcaneal tendon tissue in experimental tendinopathy under autologous platelet-rich plasma. Material and methods. Twenty mature Wistar rats, selected for the study, were divided into 5 groups. Rats of all groups received intra- and peritendinous injections of 0.5 ml of 10% sterile talc suspension to provide the experimental modeling of tendinopathy of the calcaneal tendon. Then the tendinopathy area was treated by injections of autologous platelet-rich plasma (PRP), a hyaluronic acid preparation "Rusvisk" (Rusvisk, Russia) and their sequential combination. The results were evaluated after 10 weeks in the autopsy preparations using a light microscopy method and morphometry. Results. The histological signs characteristic of tendinopathy were revealed, such as the disorganization of collagen structures, mucoid and lipoid degeneration, neovascularization, lymphoid and histiocytic infiltration. The injection of PRP, hyaluronic acid, or their sequential combination in the area of simulated tendinopathy led to changes in the histological presentation of the tissue. As a result, the collagen matrix had less signs of disorganization and less pronounced degenerative changes, as well as manifestations of the inflammatory process in the peritenon and the soft tissues surrounding the tendon, in comparison with the histological profile, which was observed in micropreparations in animals with tendinopathy who had no treatment. Conclusion. The introduction of PRP into the area of the calcaneal tendon has reduced the manifestations of the inflammatory process, disorganization of the collagen matrix, promoted the enhancement of collagen synthesis by cells and, ultimately, the processes of tissue remodeling.