Electron-phonon processes in semiconductors at low temperatures

The thermal conductivity and thermopower are simultaneously studied in the semiconductors HgSe, HgTe, InP, GaAs, Cd _x H_{1 ? x} Te, and Ag₂S in which the effect of electron drag by phonons was detected at low temperatures T. It is found that x = 1–3 in the dependences K _ph ∝ T ^?x . It is shown that the underestimated values of x are caused by phonon scattering at certain defects. It is also found that the maxima of K _ph(T) and α_ph(T) coincide in all studied crystals, except for Ag₂S. For the first time, it is found that the strong effect α_ph ∝ T ^?3 is observed in Ag₂S, the α_ph maximum is at T = 16 K, and the K _ph maximum is at 27 K. The results obtained are in agreement with Callaway and Herring theory. The effect of magnetic field on the drag thermopower α_ph(T) in n-Cd _x H_1?x Te (in which the strong dependence α_ph ∝ T ^?3 and the strong effect of the magnetic field on it are detected) is considered for the first time. The results are compared with the Askerov theory. The force parameter A _ph(?) of the drag effect and its dependence on magnetic field are determined.     

Developing and applying modern methods of leakage monitoring and state estimation of fuel at the Novovoronezh nuclear power plant

The results of developing and implementing the modernized fuel leakage monitoring methods at the shut-down and running reactor of the Novovoronezh nuclear power plant (NPP) are presented. An automated computerized expert system integrated with an in-core monitoring system (ICMS) and installed at the Novovoronezh NPP unit no. 5 is described. If leaky fuel elements appear in the core, the system allows one to perform on-line assessment of the parameters of leaky fuel assemblies (FAs). The computer expert system units designed for optimizing the operating regimes and enhancing the fuel usage efficiency at the Novovoronezh NPP unit no. 5 are now being developed.