[en] Lifetime control in power devices is an effective means of their speeding. To reduce the turn-off time of such devices, irradiation with fast electrons may be used. The main advantage of the electron irradiation as a means of lifetime control is the possibility to irradiate the devices after their packaging. Required characteristics of devices can be finally adjusted by varying the dose given to them. An MOS controlled thyristor (MCT) with a blocking voltage of 3000 V was used to demonstrate the possibilities offered by this method. Before irradiation, the turn-off time of the MCT was 30 μs. After irradiating the thyristor with 2 MeV electrons up to the dose 5x10¹² cm^-2, the turn-off time was reduced to 2.5 μs. The on-voltage was increased to 7.5 V at a highest controlled current density of 160 A/cm². The experiments showed that, using electron irradiation, it is possible to control the minority carrier lifetime in the range between 30 and 2 μs with acceptable increase in the on-voltage (from 2.8 to 7.5 V). The most interesting consequences of the above treatment were an increase in the current density which could be controlled by the thyristor (up to 160 A/cm² ) and the possibility of device operation at a total current of 55 A. Thermal stability of the radiation-reduced changes was compared with the case of proton-irradiated MCT crystals

[en] The main goal of the Project is to study and evaluate nuclear characteristics of materials and isotopes involved in processes of irradiated nuclear fuel transmutation. This principal task is subdivided into 9 subtasks subject to the neutron or proton source used, the type of the nuclear process under study, isotope collection, characteristics of which are to be investigated, etc. In the presented extract of the Project Activity report the measurements there were used the MAKET zero-power heavy-water reactor in the measurements there was employed a large set of minor actinide samples highly enriched with the main isotope. The samples were obtained with mass-separator SM-2 (VNIIEF). At the heavy-water reactor MAKET (ITEP) there were measured multiplying and kinetic characteristics of salt mixtures basing on the spectra of fast and thermal neutrons. The salt mixtures of zirconium and sodium fluorides were available in salt blanket models (SBM) of cylindrical shape. There were measured the neutron spectra formed by this micro-model as well as the effective fission cross-sections of neptunium, plutonium, americium and curium isotopes caused by SBM neutrons. The neutron spectra in the measurement positions were determined from activation reaction rates. (author)

[en] The work presents the results of determining the blanket subcriticality for a zero-power heavy water reactor MAKET at the Institute for Theoretical and Experimental Physics, Moscow. The blanket is hexagonal lattice made of 36 90%-enriched 235U fuel rods spaced 173mm apart. The subcriticality was varied from ∼0.3% to 5% by adjusting the heavy water level. The subcriticality values were calibrated using the dependence of reactivity on heavy water level. The pulsed neutron source technique was used to measure the temporal dependence of neutron field at different blanket points for the calibrated subcriticality values. The subciticality values obtained in terms of the 'inverse clock' formulae using the decay constants of the measured dependences proved to differ from the calibrated subcriticalities by not more than 7% at the average. The MCNP code-aided simulations of the experiment made has given the calibrated keff values at prescribed heavy water levels and led to the neutron field decay constants at given points, which differ on the average from their experimental values by not more than 7% too. (author)