At the stage of design and testing of fuel rods for reactors that must operate in complex temperature and mechanical conditions, it is important to establish the maximum allowable temperature regimes, in particular the temperature distribution along the fuel rods. An ultrasonic control seems to be one of the possible non-destructive methods for assessing product quality. We consider the ultrasonic devices to monitor operational temperature modes of fuel rods and can propose the pulsed multi-zone thermometers as the optimal type.
The paper analyzes operating conditions, thermophysical characteristics were calculated as applied to WWER-1000 fuel rods in a four-year cycle for unified core. The paper gives a summary of models for calculating gas release, pressure of gases within fuel rod cladding, fuel swelling and thermal conductivity, fuel-cladding gap conductance. The thermophysical condition of fuels in a reactor core is one of the main factors that determine their serviceability.
The paper describes the phenomenology of fuel rod behaviour in severe accident. As an example, an experiment is described resulting in severe damage of 19 fuel rod assembly of VVER type; it was carried out in the CORA facility in 1993 (Research Centre, Karlsruhe, Germany). Testing conditions and results of post-test investigations of fuel assembly are given. The fuel rod code RAPTA-SFD is briefly dealt with; the code was a participant in the International Standard Problem ISP-36. The basic results are presented acquired by computer modelling CORA-W2 experiment using RAPTA-SFD code.