Determination of the structural and thermophysical parameters of fuel composition

Use of the methods for identifications of systems with distributed parameters makes it possible to investigate evolution of the main structural and thermophysical parameters of fuel compositions directly in the process of irradiation. The results of the calculations and experiments on the contact thermal resistance (CTR) between the fuel and VVER-440 cladding depending on the linear heat generating rate in the process raise the reactor power in the initial increase the reactor power are presented as an example of practical application of method. The experimental data for the VVER-440 fuel elements are presented. The effect of cracking of the pellets of the fuel elements filled with helium on dependence of CTR on linear heat generating rate is analyzed. The fact of pellet jump in the fuel elements filled with helium at a linear heat generating rate of about 200 W/cm are discussed. 5 refs.; 4 figs. (author)